ABCA1 p.Cys1477Arg
ClinVar: |
c.4429T>C
,
p.Cys1477Arg
D
, Pathogenic
|
Predicted by SNAP2: | A: D (71%), D: D (91%), E: D (85%), F: D (85%), G: D (85%), H: D (85%), I: D (80%), K: D (91%), L: D (80%), M: D (80%), N: D (80%), P: D (91%), Q: D (80%), R: D (91%), S: D (80%), T: D (80%), V: D (80%), W: D (91%), Y: D (85%), |
Predicted by PROVEAN: | A: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D, |
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[hide] Anticancer Activity of the Cholesterol Exporter AB... Cell Rep. 2012 Sep 27;2(3):580-90. doi: 10.1016/j.celrep.2012.08.011. Epub 2012 Sep 13. Smith B, Land H
Anticancer Activity of the Cholesterol Exporter ABCA1 Gene.
Cell Rep. 2012 Sep 27;2(3):580-90. doi: 10.1016/j.celrep.2012.08.011. Epub 2012 Sep 13., [PMID:22981231]
Abstract [show]
The ABCA1 protein mediates the transfer of cellular cholesterol across the plasma membrane to apolipoprotein A-I. Loss-of-function mutations in the ABCA1 gene induce Tangier disease and familial hypoalphalipoproteinemia, both cardiovascular conditions characterized by abnormally low levels of serum cholesterol, increased cholesterol in macrophages, and subsequent formation of vascular plaque. Increased intracellular cholesterol levels are also frequently found in cancer cells. Here, we demonstrate anticancer activity of ABCA1 efflux function, which is compromised following inhibition of ABCA1 gene expression by oncogenic mutations or cancer-specific ABCA1 loss-of-function mutations. In concert with elevated cholesterol synthesis found in cancer cells, ABCA1 deficiency allows for increased mitochondrial cholesterol, inhibits release of mitochondrial cell death-promoting molecules, and thus facilitates cancer cell survival, suggesting that elevated mitochondrial cholesterol is essential to the cancer phenotype.
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No. Sentence Comment
124 To this end, we utilized two missense mutations of human ABCA1 proteins (Q597R and C1477R) linked to TD and familial hypoalphalipoproteinemia (FHA), which were previously characterized to have diminished cholesterol efflux activity (Singaraja et al., 2006).
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ABCA1 p.Cys1477Arg 22981231:124:83
status: NEW[hide] Regulation of ABCA1 functions by signaling pathway... Biochim Biophys Acta. 2012 Mar;1821(3):522-9. doi: 10.1016/j.bbalip.2011.08.015. Epub 2011 Sep 5. Liu Y, Tang C
Regulation of ABCA1 functions by signaling pathways.
Biochim Biophys Acta. 2012 Mar;1821(3):522-9. doi: 10.1016/j.bbalip.2011.08.015. Epub 2011 Sep 5., [PMID:21920460]
Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) is an integral cell membrane protein that protects cardiovascular disease by at least two mechanisms: by export of excess cholesterol from cells and by suppression of inflammation. ABCA1 exports cholesterol and phospholipids from cells by multiple steps that involve forming cell surface lipid domains, binding of apolipoproteins to ABCA1, activating signaling pathways, and solubilizing these lipids by apolipoproteins. ABCA1 executes its anti-inflammatory effect by modifying cell membrane lipid rafts and directly activating signaling pathways. The interaction of apolipoproteins with ABCA1 activates multiple signaling pathways, including Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3), protein kinase A, Rho family G protein CDC42 and protein kinase C. Activating protein kinase A and Rho family G protein CDC42 regulates ABCA1-mediated lipid efflux, activating PKC stabilizes ABCA1 protein, and activating JAK2/STAT3 regulates both ABCA1-mediated lipid efflux and anti-inflammation. Thus, ABCA1 behaves both as a lipid exporter and a signaling receptor. Targeting ABCA1 receptor-like property using agonists for ABCA1 protein could become a promising new therapeutic target for increasing ABCA1 function and treating cardiovascular disease. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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109 Significantly, one naturally-occurring mutation of ABCA1 associated with Tangier disease, C1477R, severely reduces apoA-I-mediated cAMP production, ABCA1 phosphorylation and apoA-I-mediated lipid efflux, suggesting that direct interaction of apoA-I with a functional ABCA1 is required for the activation of cAMP/PKA pathway by apoA-I.
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ABCA1 p.Cys1477Arg 21920460:109:90
status: NEW[hide] Increased risk of coronary artery disease in Cauca... Biochim Biophys Acta. 2012 Mar;1821(3):416-24. doi: 10.1016/j.bbalip.2011.08.006. Epub 2011 Aug 19. Tietjen I, Hovingh GK, Singaraja R, Radomski C, McEwen J, Chan E, Mattice M, Legendre A, Kastelein JJ, Hayden MR
Increased risk of coronary artery disease in Caucasians with extremely low HDL cholesterol due to mutations in ABCA1, APOA1, and LCAT.
Biochim Biophys Acta. 2012 Mar;1821(3):416-24. doi: 10.1016/j.bbalip.2011.08.006. Epub 2011 Aug 19., [PMID:21875686]
Abstract [show]
Mutations in ABCA1, APOA1, and LCAT reduce HDL cholesterol (HDLc) in humans. However, the prevalence of these mutations and their relative effects on HDLc reduction and risk of coronary artery disease (CAD) are less clear. Here we searched for ABCA1, APOA1, and LCAT mutations in 178 unrelated probands with HDLc <10th percentile but no other major lipid abnormalities, including 89 with >/=1 first-degree relative with low HDLc (familial probands) and 89 where familial status of low HDLc is uncertain (unknown probands). Mutations were most frequent in LCAT (15.7%), followed by ABCA1 (9.0%) and APOA1 (4.5%), and were found in 42.7% of familial but only 14.6% of unknown probands (p=2.44 *10(-5)). Interestingly, only 16 of 24 (66.7%) mutations assessed in families conferred an average HDLc <10th percentile. Furthermore, only mutation carriers with HDLc <5th percentile had elevated risk of CAD (odds ratio (OR)=2.26 for 34 ABCA1 mutation carriers vs. 149 total first-degree relative controls, p=0.05; OR=2.50 for 26 APOA1 mutation carriers, p=0.04; OR=3.44 for 38 LCAT mutation carriers, p=1.1 *10(-3)). These observations show that mutations in ABCA1, APOA1, and LCAT are sufficient to explain >40% of familial hypoalphalipoproteinemia in this cohort. Moreover, individuals with mutations and large reductions in HDLc have increased risk of CAD. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).
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No. Sentence Comment
117 COOHA B T929I H2N R587W B A M1091T C1477R K776N N935S S1181F IVS24+1 G>C V2244I R282X D571G M640L S930F M968T R1615WIVS16-5 CA>del ABCA1 Transmembrane domain ATP-binding domain Q597R A) AA 1 AA 267 K130del L202P 74 90 98 112 122 145 167 189 211 215 233 253 APOA1 Negative charge domain Alpha-helix E222K E134DT37M 140 178 206 41127 104 121 165 200 229 360 391 Y135N V246F 127 206 369 401 Catalytic triad R322C L338H V371MV52M Y107X A117T T147I V333M Phe Leu Asp His AA 1 AA 440 R159Q I202T LCAT Alpha helixBeta sheet B) 419I.Tietjenetal./BiochimicaetBiophysicaActa1821(2012)416-424 3.4.
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ABCA1 p.Cys1477Arg 21875686:117:35
status: NEW[hide] Function and regulation of ABCA1--membrane meso-do... FEBS J. 2011 Sep;278(18):3190-203. doi: 10.1111/j.1742-4658.2011.08170.x. Epub 2011 Jun 13. Nagao K, Tomioka M, Ueda K
Function and regulation of ABCA1--membrane meso-domain organization and reorganization.
FEBS J. 2011 Sep;278(18):3190-203. doi: 10.1111/j.1742-4658.2011.08170.x. Epub 2011 Jun 13., [PMID:21554545]
Abstract [show]
The ATP-binding cassette protein A1 (ABCA1) mediates the secretion of cellular-free cholesterol and phospholipids to an extracellular acceptor, apolipoprotein A-I, to form high-density lipoprotein. Because ABCA1 is a key factor in cholesterol homeostasis, elaborate transcriptional and post-transcriptional regulations of ABCA1 have evolved to maintain cholesterol homeostasis. Recent studies suggest that ABCA1 moves lipids not only between membranes but also within membranes to organize and reorganize membrane meso-domains to modulate cell proliferation and immunity.
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No. Sentence Comment
80 This group is represented by the C1477R mutant of the second ECD (Table 2).
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ABCA1 p.Cys1477Arg 21554545:80:33
status: NEW81 Although C1477R mutant is expressed in the plasma membrane like wild-type ABCA1, apoA-I binding is abolished [9,10,49,50].
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ABCA1 p.Cys1477Arg 21554545:81:9
status: NEW[hide] Characterization of antioxidant/anti-inflammatory ... Clin Chim Acta. 2011 Jun 11;412(13-14):1213-20. Epub 2011 Mar 21. Daniil G, Phedonos AA, Holleboom AG, Motazacker MM, Argyri L, Kuivenhoven JA, Chroni A
Characterization of antioxidant/anti-inflammatory properties and apoA-I-containing subpopulations of HDL from family subjects with monogenic low HDL disorders.
Clin Chim Acta. 2011 Jun 11;412(13-14):1213-20. Epub 2011 Mar 21., [PMID:21420943]
Abstract [show]
BACKGROUND: Genetic factors regulate both high-density lipoprotein (HDL) levels and functionality, thus affecting HDL antiatherogenic properties. We characterized the HDL antioxidant/anti-inflammatory properties and apoA-I-containing subpopulations in families with monogenic low HDL disorders. METHODS: Subjects with mutations in apolipoprotein A-I (apoA-I), ATP-binding cassette transporter A1 (ABCA1) or lecithin:cholesterol acyltransferase (LCAT) and family controls were studied. HDL antioxidant/anti-inflammatory properties were assayed by an in vitro fluorometric method and HDL-associated paraoxonase-1 (PON1), platelet activating factor-acetylhydrolase (PAF-AH), LCAT, malondialdehyde (MDA), PAF and serum amyloid A (SAA) were measured. ApoA-I-containing HDL subpopulations were analyzed by two-dimensional non-denaturing gel electrophoresis. RESULTS: ApoA-I heterozygotes and subjects with partial or complete ABCA1 or LCAT deficiency had HDL with reduced antioxidant/anti-inflammatory properties and increased MDA levels. HDL-PON1 activity was reduced in apoA-I heterozygotes and in subjects with complete ABCA1 deficiency. HDL-PAF-AH activity was reduced in subjects with partial or complete ABCA1 deficiency or complete LCAT deficiency. HDL-LCAT activity was reduced in all LCAT mutation carriers. HDL-PAF levels were increased in apoA-I heterozygotes. HDL-SAA levels were increased in subjects with complete ABCA1 deficiency. ApoA-I, ABCA1 and LCAT heterozygotes were depleted of the large alpha1 HDL subpopulation. Subjects with complete LCAT deficiency showed mostly the small alpha4 HDL subpopulation and subjects with complete ABCA1 deficiency the alpha4 and prebeta HDL subpopulations. CONCLUSIONS: This study shows that mutations in apoA-I, ABCA1 and LCAT have direct effect on the antioxidant/anti-inflammatory properties of HDL. Furthermore, our study shows the effect of specific mutations on the apoA-I-containing HDL subpopulation profiles.
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No. Sentence Comment
56 Subjects We examined serum obtained from 3 heterozygotes for the apoA-I (NM_000039) mutation p.L202P (n=3; mutation was previously denoted as L178P [14]), 6 heterozygotes for ABCA1 (NM_005502) mutations(p.C1477R,n=3;p.L1056P,n=3),2compoundheterozygotes for ABCA1 mutations (p.C1477R/IVS25+1GNC; p.Q1038X/p.N1800H), 1 homozygote for the ABCA1 mutation p.L1056P, 12 heterozygotes for LCAT (NM_000229) mutations (p.P34Q, n=1; p.Y107X, n=1; p.T147I, n=4; p.N155D, n=2; p.I202T, n=1; p.R322C, n=2, p.V333M, n=1), 3 compound heterozygotes for the LCAT mutation p.T147I/IVS4-22TNC and 1 homozygote for the LCAT mutation p.N155D.
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ABCA1 p.Cys1477Arg 21420943:56:205
status: NEWX
ABCA1 p.Cys1477Arg 21420943:56:276
status: NEW150 Male/female TC HDL-c apoA-I apoA-II LDL-c apoB TG apoA-I mutation carriers Unaffected (n=3) 1/2 179±27 45±3 163±13 30±1 131±22 97±15 97±25 Heterozygotes (n=3) 1/2 141±12* 20±14* 87±38* 19±6* 113±5 85±6 97±45 ABCA1 mutation carriers Unaffected (n=8) 4/4 171±56 57±15 160±29 30±4 111±23 84±12 85±20 Heterozygotes (n=6) 3/3 179±64 37±7** 124±12** 28±2 129±35 98±22 90±44 Compound heterozygote 1c (n=1) 1/0 54 6 4 2 44 75 138 Compound heterozygote 2d (n=1) 0/1 220 3 7 ndb 173 192 387 Homozygote (n=1) 0/1 63 0.8 nd nd 61 81 87 LCAT mutation carriers Unaffected (n=7) 5/2 199±32 49±13 166±19 31±2 134±28 100±20 123±58 Heterozygotes (n=12) 8/4 166±47 32±11** 122±27*** 26±5* 122±38 97±28 115±49 Compound heterozygotes (n=3) 0/3 140±24* 5±1*** 48±8*** 3.8±0.3*** 118±17 102±27 244±103* Homozygote (n=1) 1/0 107 3 58 4 77 118 279 a Values presented as mean±SD (mg/dl); b nd, not detectable; c ABCA1[p.C1477R/IVS25+1GNC]; d ABCA1[p.Q1038X/ p.N1800H].
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ABCA1 p.Cys1477Arg 21420943:150:1144
status: NEW162 HDL from heterozygotes for ABCA1 mutations (p.C1477R, p.L1056P), incubated in the absence or presence of LDL, increased the fluorescence signal by 39% (p=0.043) and 41% (p=0.029), respectively, compared to controls (Fig. 2A).
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ABCA1 p.Cys1477Arg 21420943:162:46
status: NEW163 A previous study has shown that heterozygotes for ABCA1 mutation p.C1477R, but not for ABCA1 mutation p.L1056P, have increased CAD compared to unaffected family members [24,25].
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ABCA1 p.Cys1477Arg 21420943:163:67
status: NEWX
ABCA1 p.Cys1477Arg 21420943:163:105
status: NEWX
ABCA1 p.Cys1477Arg 21420943:163:112
status: NEWX
ABCA1 p.Cys1477Arg 21420943:163:125
status: NEWX
ABCA1 p.Cys1477Arg 21420943:163:159
status: NEW164 These observations may be related to the current finding (although the number of analyzed samples is small) that HDL from heterozygotes for ABCA1 mutation p.C1477R was more oxidized and contained higher MDA levels compared to HDL from heterozygotes for ABCA1 mutation p. L1056P (Fig. 2A, B).
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ABCA1 p.Cys1477Arg 21420943:164:157
status: NEW166 Compound heterozygotes for ABCA1 mutations * * 0 10000 20000 30000 40000 50000 60000 70000 L1056P L1056P C1477R C1477R ** ** C1477R/ IVS25+1G>C Q1038X/ N1800H C1477R/ IVS25+1G>C Q1038X/ N1800H 0.0 2.5 5.0 7.5 10.0 SAA/HDL-c(RLU) ** 0 10 20 30 40 *** 0 1 2 3 PAF-AHactivity (nmolCE/h) A B C D * ** HDL C HDL Het HDL Com HDL Hom HDL C HDL Het HDL Com HDL Hom HDL C HDL Het HDL Com HDL Hom DCF LDL HDL C HDL HetHDL C +LDL HDL Het + LDL HDL Com HDL Com +LDL Fluoresence(AU) MDA/HDL-c(RLU) Fig. 2.
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ABCA1 p.Cys1477Arg 21420943:166:105
status: NEWX
ABCA1 p.Cys1477Arg 21420943:166:112
status: NEWX
ABCA1 p.Cys1477Arg 21420943:166:125
status: NEWX
ABCA1 p.Cys1477Arg 21420943:166:159
status: NEW176 p.C1477R/ IVS25+1GNC and a homozygote for ABCA1 mutation p.L1056P presented with CAD [24,25].
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ABCA1 p.Cys1477Arg 21420943:176:2
status: NEW147 Male/female TC HDL-c apoA-I apoA-II LDL-c apoB TG apoA-I mutation carriers Unaffected (n=3) 1/2 179&#b1;27 45&#b1;3 163&#b1;13 30&#b1;1 131&#b1;22 97&#b1;15 97&#b1;25 Heterozygotes (n=3) 1/2 141&#b1;12* 20&#b1;14* 87&#b1;38* 19&#b1;6* 113&#b1;5 85&#b1;6 97&#b1;45 ABCA1 mutation carriers Unaffected (n=8) 4/4 171&#b1;56 57&#b1;15 160&#b1;29 30&#b1;4 111&#b1;23 84&#b1;12 85&#b1;20 Heterozygotes (n=6) 3/3 179&#b1;64 37&#b1;7** 124&#b1;12** 28&#b1;2 129&#b1;35 98&#b1;22 90&#b1;44 Compound heterozygote 1c (n=1) 1/0 54 6 4 2 44 75 138 Compound heterozygote 2d (n=1) 0/1 220 3 7 ndb 173 192 387 Homozygote (n=1) 0/1 63 0.8 nd nd 61 81 87 LCAT mutation carriers Unaffected (n=7) 5/2 199&#b1;32 49&#b1;13 166&#b1;19 31&#b1;2 134&#b1;28 100&#b1;20 123&#b1;58 Heterozygotes (n=12) 8/4 166&#b1;47 32&#b1;11** 122&#b1;27*** 26&#b1;5* 122&#b1;38 97&#b1;28 115&#b1;49 Compound heterozygotes (n=3) 0/3 140&#b1;24* 5&#b1;1*** 48&#b1;8*** 3.8&#b1;0.3*** 118&#b1;17 102&#b1;27 244&#b1;103* Homozygote (n=1) 1/0 107 3 58 4 77 118 279 a Values presented as mean&#b1;SD (mg/dl); b nd, not detectable; c ABCA1[p.C1477R/IVS25+1GNC]; d ABCA1[p.Q1038X/ p.N1800H].
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ABCA1 p.Cys1477Arg 21420943:147:1094
status: NEW159 HDL from heterozygotes for ABCA1 mutations (p.C1477R, p.L1056P), incubated in the absence or presence of LDL, increased the fluorescence signal by 39% (p=0.043) and 41% (p=0.029), respectively, compared to controls (Fig. 2A).
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ABCA1 p.Cys1477Arg 21420943:159:46
status: NEW160 A previous study has shown that heterozygotes for ABCA1 mutation p.C1477R, but not for ABCA1 mutation p.L1056P, have increased CAD compared to unaffected family members [24,25].
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ABCA1 p.Cys1477Arg 21420943:160:67
status: NEW161 These observations may be related to the current finding (although the number of analyzed samples is small) that HDL from heterozygotes for ABCA1 mutation p.C1477R was more oxidized and contained higher MDA levels compared to HDL from heterozygotes for ABCA1 mutation p. L1056P (Fig. 2A, B).
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ABCA1 p.Cys1477Arg 21420943:161:157
status: NEW173 p.C1477R/ IVS25+1GNC and a homozygote for ABCA1 mutation p.L1056P presented with CAD [24,25].
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ABCA1 p.Cys1477Arg 21420943:173:2
status: NEW[hide] Plasma levels of 27-hydroxycholesterol in humans a... Atherosclerosis. 2011 Feb;214(2):448-55. Epub 2010 Nov 3. Karuna R, Holleboom AG, Motazacker MM, Kuivenhoven JA, Frikke-Schmidt R, Tybjaerg-Hansen A, Georgopoulos S, van Eck M, van Berkel TJ, von Eckardstein A, Rentsch KM
Plasma levels of 27-hydroxycholesterol in humans and mice with monogenic disturbances of high density lipoprotein metabolism.
Atherosclerosis. 2011 Feb;214(2):448-55. Epub 2010 Nov 3., [PMID:21130455]
Abstract [show]
Secretion of 27-hydroxycholesterol (27OHC) from macrophages is considered as an alternative to HDL-mediated reverse transport of excess cholesterol. We investigated 27OHC-concentrations in plasma of humans and mice with monogenic disorders of HDL metabolism. As compared to family controls mutations in the genes for apolipoprotein A-I, ATP binding cassette transporter (ABC) A1 and lecithin:cholesterol acylstransferase (LCAT) were associated with reduced concentrations of both HDL-cholesterol and HDL-27OHC whereas mutations in the genes for cholesterylester transfer protein (CETP), scavenger receptor type BI and hepatic lipase were associated with elevated HDL concentrations of either sterol. Compared to family controls and relative to the concentrations of total 27OHC and cholesterol, lower 27OHC-ester but normal cholesterylester levels were found in HDL of heterozygous LCAT mutation carriers and nonHDL of heterozygous CETP mutation carriers. In family controls, LCAT activity and CETP mass were more strongly correlated with 27OHC-ester than cholesterylester concentrations in HDL and nonHDL, respectively. These findings suggest that the formation and transfer of 27OHC-esters are more sensitive to reduced activities of LCAT and CETP, respectively, than the formation and transfer of cholesterylesters. 27OHC plasma levels were also decreased in apoA-I-, ABCA1- or LCAT-knockout mice but increased in SR-BI-knockout mice. Transplantation of ABCA1- and/or ABCG1-deficient bone marrow into LDL receptor deficient mice decreased plasma levels of 27OHC. In conclusion, mutations or absence of HDL genes lead to distinct alterations in the quantity, esterification or lipoprotein distribution of 27OHC. These findings argue against the earlier suggestion that 27OHC-metabolism in plasma occurs independently of HDL.
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No. Sentence Comment
63 Mutated gene Number of defective alleles Mutationa Age (year) Cholesterol (mM) HDL-cholesterol (mM) NonHDL-cholesterol (mM) Triglyceride (mM) Number of smokers Dutch APOA1 0 27 ± 14 4.59 ± 0.68 1.16 ± 0.06 3.43 ± 0.63 1.09 ± 0.29 0 1 p.L202P (c.605T > C) 26 ± 17 3.61 ± 0.31 0.51 ± 0.35 3.10 ± 0.06 1.09 ± 0.51 0 ABCA1 0 44 ± 20 4.39 ± 0.89 1.47 ± 0.39 2.92 ± 0.62 0.95 ± 0.22 1 1 p.L1056P (c.3167T > C) or p.C1477R (c.4429T > C) 57 ± 11 4.47 ± 1.08 0.94 ± 0.17 3.53 ± 0.96 1.01 ± 0.05 0 2 p.L1056P (c.3167T > C, homozygote) or p.Q1038X (c.3112C > T) + p.N1800H (c.5398A > C) or p.C1477R (c.4429T > C) + IVS25 + 1G > C 53 ± 10 2.89 ± 2.39 NDb NDb 2.29 ± 1.80 0 LCAT 0 49 ± 9 4.96 ± 0.86 1.33 ± 0.38 3.62 ± 0.97 1.29 ± 0.66 0 1 p.T147I (c.440C > T), p.R322C (c.964C > T), p.N155D (c.463A > G), p.P34Q (c.101C > A), p.Y107X (c.321C > A), p.I202T (c.605T > C) or p.V333M (c.997G > A) 43 ± 13 4.27 ± 1.21 0.81 ± 0.28 3.45 ± 1.08 1.30 ± 0.55 1 2 p.T147I (c.440C > T) + V333M 69 ± 4 3.26 ± 0.19 NDb NDb 2.11 ± 0.49 0 SR-BI 0 54 ± 19 4.77 ± 0.89 1.17 ± 0.33 3.60 ± 0.79 1.21 ± 0.64 0 1 p.P297S (c.889C > T) 45 ± 22 4.46 ± 1.21 1.73 ± 0.56 2.73 ± 0.81 0.97 ± 0.28 1 CETP 0 36 ± 16 4.14 ± 0.51 1.30 ± 0.21 2.85 ± 0.48 0.87 ± 0.40 1 1 IVS7 + 1 (G > T) 39 ± 18 4.20 ± 0.51 1.56 ± 0.29 2.64 ± 0.77 0.76 ± 0.32 1 HL (LIPC) 0 45 ± 19 5.23 ± 0.99 1.61 ± 0.54 3.62 ± 0.90 1.45 ± 1.05 3 1 p.S289F (c.866C > T) 45 ± 15 4.92 ± 1.21 2.00 ± 0.68 2.92 ± 0.86 1.14 ± 0.43 1 Danish Controls 0 50 ± 9 5.84 ± 1.24 1.54 ± 0.24 4.30 ± 1.23 1.34 ± 0.62 1 APOA1 1 p.L168R (c.503T > G) 63 ± 4 4.70 ± 0.28 0.85 ± 0.07 3.85 ± 0.35 1.27 ± 0.70 0 CETP 1 p.S349Y (c.1046C > A) 59 ± 4 6.85 ± 2.05 3.05 ± 1.77 3.80 ± 0.28 0.86 ± 0.23 1 Values represent mean ± SD.
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ABCA1 p.Cys1477Arg 21130455:63:484
status: NEWX
ABCA1 p.Cys1477Arg 21130455:63:681
status: NEW62 Mutated gene Number of defective alleles Mutationa Age (year) Cholesterol (mM) HDL-cholesterol (mM) NonHDL-cholesterol (mM) Triglyceride (mM) Number of smokers Dutch APOA1 0 27 &#b1; 14 4.59 &#b1; 0.68 1.16 &#b1; 0.06 3.43 &#b1; 0.63 1.09 &#b1; 0.29 0 1 p.L202P (c.605T > C) 26 &#b1; 17 3.61 &#b1; 0.31 0.51 &#b1; 0.35 3.10 &#b1; 0.06 1.09 &#b1; 0.51 0 ABCA1 0 44 &#b1; 20 4.39 &#b1; 0.89 1.47 &#b1; 0.39 2.92 &#b1; 0.62 0.95 &#b1; 0.22 1 1 p.L1056P (c.3167T > C) or p.C1477R (c.4429T > C) 57 &#b1; 11 4.47 &#b1; 1.08 0.94 &#b1; 0.17 3.53 &#b1; 0.96 1.01 &#b1; 0.05 0 2 p.L1056P (c.3167T > C, homozygote) or p.Q1038X (c.3112C > T) + p.N1800H (c.5398A > C) or p.C1477R (c.4429T > C) + IVS25 + 1G > C 53 &#b1; 10 2.89 &#b1; 2.39 NDb NDb 2.29 &#b1; 1.80 0 LCAT 0 49 &#b1; 9 4.96 &#b1; 0.86 1.33 &#b1; 0.38 3.62 &#b1; 0.97 1.29 &#b1; 0.66 0 1 p.T147I (c.440C > T), p.R322C (c.964C > T), p.N155D (c.463A > G), p.P34Q (c.101C > A), p.Y107X (c.321C > A), p.I202T (c.605T > C) or p.V333M (c.997G > A) 43 &#b1; 13 4.27 &#b1; 1.21 0.81 &#b1; 0.28 3.45 &#b1; 1.08 1.30 &#b1; 0.55 1 2 p.T147I (c.440C > T) + V333M 69 &#b1; 4 3.26 &#b1; 0.19 NDb NDb 2.11 &#b1; 0.49 0 SR-BI 0 54 &#b1; 19 4.77 &#b1; 0.89 1.17 &#b1; 0.33 3.60 &#b1; 0.79 1.21 &#b1; 0.64 0 1 p.P297S (c.889C > T) 45 &#b1; 22 4.46 &#b1; 1.21 1.73 &#b1; 0.56 2.73 &#b1; 0.81 0.97 &#b1; 0.28 1 CETP 0 36 &#b1; 16 4.14 &#b1; 0.51 1.30 &#b1; 0.21 2.85 &#b1; 0.48 0.87 &#b1; 0.40 1 1 IVS7 + 1 (G > T) 39 &#b1; 18 4.20 &#b1; 0.51 1.56 &#b1; 0.29 2.64 &#b1; 0.77 0.76 &#b1; 0.32 1 HL (LIPC) 0 45 &#b1; 19 5.23 &#b1; 0.99 1.61 &#b1; 0.54 3.62 &#b1; 0.90 1.45 &#b1; 1.05 3 1 p.S289F (c.866C > T) 45 &#b1; 15 4.92 &#b1; 1.21 2.00 &#b1; 0.68 2.92 &#b1; 0.86 1.14 &#b1; 0.43 1 Danish Controls 0 50 &#b1; 9 5.84 &#b1; 1.24 1.54 &#b1; 0.24 4.30 &#b1; 1.23 1.34 &#b1; 0.62 1 APOA1 1 p.L168R (c.503T > G) 63 &#b1; 4 4.70 &#b1; 0.28 0.85 &#b1; 0.07 3.85 &#b1; 0.35 1.27 &#b1; 0.70 0 CETP 1 p.S349Y (c.1046C > A) 59 &#b1; 4 6.85 &#b1; 2.05 3.05 &#b1; 1.77 3.80 &#b1; 0.28 0.86 &#b1; 0.23 1 Values represent mean &#b1; SD.
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ABCA1 p.Cys1477Arg 21130455:62:469
status: NEWX
ABCA1 p.Cys1477Arg 21130455:62:661
status: NEW[hide] Identification and characterization of novel loss ... Atherosclerosis. 2010 Dec;213(2):492-8. Epub 2010 Aug 26. Candini C, Schimmel AW, Peter J, Bochem AE, Holleboom AG, Vergeer M, Dullaart RP, Dallinga-Thie GM, Hovingh GK, Khoo KL, Fasano T, Bocchi L, Calandra S, Kuivenhoven JA, Motazacker MM
Identification and characterization of novel loss of function mutations in ATP-binding cassette transporter A1 in patients with low plasma high-density lipoprotein cholesterol.
Atherosclerosis. 2010 Dec;213(2):492-8. Epub 2010 Aug 26., [PMID:20880529]
Abstract [show]
OBJECTIVES: The current literature provides little information on the frequency of mutations in the ATP-binding cassette transporter A1 (ABCA1) in patients with low high-density lipoprotein cholesterol (HDL) levels that are referred to the clinic. In 78 patients with low plasma levels of HDL cholesterol that were referred to our clinic, we routinely screened for ABCA1 gene mutations and studied the functionality of newly identified ABCA1 missense mutations. METHODS: The coding regions and exon-intron boundaries of the ABCA1 gene were sequenced in 78 subjects with HDL cholesterol levels below the 10th percentile for age and gender. Novel mutations were studied by assessing cholesterol efflux capacity (using apolipoprotein A-I as acceptor) after transient expression of ABCA1 variants in BHK cells. RESULTS: Sixteen out of 78 patients (21%) were found to carry 19 different ABCA1 gene variants (1 frameshift, 2 splice-site, 4 nonsense and 12 missense variation) of which 14 variations were novel. Of three patients with homozygous mutations and three patients having compound heterozygous mutations only one patient presented with the clinical characteristics of Tangier Disease (TD) in the presence of nearly complete HDL deficiency. Seven out of eight newly identified ABCA1 missense mutations were found to exhibit a statistically significant loss of cholesterol efflux capacity. CONCLUSION: This study shows that one out of five patients who are referred to our hospital because of low HDL cholesterol levels have a functional ABCA1 gene mutation. It is furthermore demonstrated that in vitro studies are needed to assess functionality of ABCA1 missense mutations.
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76 Patients (gender, age) Amino acida (nucleotidea ) change TC TG LDL-c HDL-c Clinical manifestations of TD CVD Other relevant clinical data Homozygotes Patient 1 (female, 42) p.L1056P (c.3167T > C) 2.4 0.9 1.99 <0.10 Absent CAD Thrombocytopenia Patient 2 (male, 40) p.Wl747X (c.5240G > A) 1.76 1.93 0.52 0.1-0.3 Neuropathy, splenomegaly, thrombocytopenia Mild stenosis (20-30%) of coronary arteries None Patient 3 (male, 55) p.F593L (c.1779C > G) 4.4 1.4 3.6 <0.10 Absent CAD None p.E1253K (c.3757G > A) Compound heterozygotes Patient 4 (female, 63) p.Q1038X (c.3112C > T) 6.68 2.72 5.4 <0.10 Absent None None p.N1800H (c.5398A > C) [32] Patient 5 (female, 28) p.T1512M (c.4535C > T) 4.42 1.83 3.46 0.1 Absent None None p.N1800H (c.5398A > C) [32] p.C978fsX988 (c.2934delT) Patient 6 (female, 17) p.D575G (c.1724A > G) 4.96 2.84 4.35 <0.10 Absent None DM1 p.C1941R(c.5821T > C) Heterozygotes Patient 7 (male, 42) p.S100C (c.299C > G) 8.5 8.7 4.3 0.3 N.A. None None Patient 8 (male, 58) p.E1172D (c.3516G > C) [33] 6.4 2.7 4.1 0.9 N.A. None None Patient 9 (male, 35) p.S1181F (c.3542C > T) [17] 2.9 0.31 1.88 0.88 N.A. None None Patient 10 (male, 48) p.C1477R (c.4429T > C) [13] 2.01 1.4 0.92 0.46 N.A. CAD None Patient 11 (male, 68) p.V1858A (c.5573T > C) 4.9 3.78 2.41 0.75 N.A. CAD None Patient 12 (female, 36) p.N1800H (c.5398A > C) [32] 4.6 1.2 4 <0.10 N.A. None DM2, obesity Patient 13 (male, 67) p.R282X (c.844C > T) [34] 3.2 1.21 2.14 0.51 N.A. None DM2 Patient 14 (female, 42) p.W424X (c.1272G > A) 2.07 1.04 1.39 0.21 N.A. None None Patient 15 (female, 52) N.A. - (IVS11 - 1G > A) 5.51 3.51 3.28 0.56 N.A. None Hypothyroidism, hypertension Patient 16 (female, 54) N.A. - (IVS48 + 2T > C) 3.29 1.92 1.94 0.49 N.A. None DM2, hypertension a Nomenclature based on guidelines of Human Genome Variation Society.
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ABCA1 p.Cys1477Arg 20880529:76:1150
status: NEW89 In ABCA1, we identified 14 novel and 5 known genetic variations in 16 subjects including one frameshift (p.C978fsX988), 2 splice-site (IVS11-1G > C and IVS48 + 2T > C), 4 nonsense (p.R282X, p.W424X, p.Q1038X, p.Wl747X) and 12 missense variations (p.S100C, p.D575G, p.F593L, p.L1056P, p.E1172D, p.S1181F, p.E1253K, p.C1477R, p.T1512M, p.N1800H, p.V1858A, p.C1941R).
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ABCA1 p.Cys1477Arg 20880529:89:316
status: NEW[hide] Carriers of loss-of-function mutations in ABCA1 di... Diabetes Care. 2010 Apr;33(4):869-74. Epub 2010 Jan 12. Vergeer M, Brunham LR, Koetsveld J, Kruit JK, Verchere CB, Kastelein JJ, Hayden MR, Stroes ES
Carriers of loss-of-function mutations in ABCA1 display pancreatic beta-cell dysfunction.
Diabetes Care. 2010 Apr;33(4):869-74. Epub 2010 Jan 12., [PMID:20067955]
Abstract [show]
OBJECTIVE: Abnormal cellular cholesterol handling in islets may contribute to beta-cell dysfunction in type 2 diabetes. beta-Cell deficiency for the ATP binding cassette transporter A1 (ABCA1), which mediates the efflux of cellular cholesterol, leads to altered intracellular cholesterol homeostasis and impaired insulin secretion in mice. We aimed to assess the impact of ABCA1 dysfunction on glucose homeostasis in humans. RESEARCH DESIGN AND METHODS: In heterozygous carriers of disruptive mutations in ABCA1 and family-based noncarriers of similar age, sex, and BMI, we performed oral glucose tolerance tests (OGTTs) (n = 15 vs. 14) and hyperglycemic clamps (n = 8 vs. 8). RESULTS: HDL cholesterol levels in carriers were less than half those in noncarriers, but LDL cholesterol levels did not differ. Although fasting plasma glucose was similar between groups, glucose curves after an OGTT were mildly higher in carriers than in noncarriers. During hyperglycemic clamps, carriers demonstrated lower first-phase insulin secretion than noncarriers but no difference in insulin sensitivity. The disposition index (a measure of beta-cell function adjusted for insulin sensitivity) of the carriers was significantly reduced in ABCA1 heterozygotes. CONCLUSIONS: Carriers of loss-of-function mutations in ABCA1 show impaired insulin secretion without insulin resistance. Our data provide evidence that ABCA1 is important for normal beta-cell function in humans.
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46 Subjects included in the present study were heterozygous carriers of the following extremely rare ABCA1 mutations: C1477R, M1091T, and R587W (4,7-10) and L996P and Q978X (C. Candini et al., manuscript in preparation).
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ABCA1 p.Cys1477Arg 20067955:46:115
status: NEW48 C1477R has been reported in nine heterozygous individuals, M1091T in four individuals, and R587W in seven individuals (11).
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ABCA1 p.Cys1477Arg 20067955:48:0
status: NEW93 Carriers were recruited from five different families (four C1477R carriers, three M1091T carriers, three R587W carriers, four L996P carriers, and one Q978X carrier); family control subjects were siblings, cousins, or partners of a carrier.
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ABCA1 p.Cys1477Arg 20067955:93:59
status: NEW103 This group consisted of four C1477R carriers, two M1091T carriers, one L996P carrier, one Q978X carrier, and eight control subjects.
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ABCA1 p.Cys1477Arg 20067955:103:29
status: NEW47 Subjects included in the present study were heterozygous carriers of the following extremely rare ABCA1 mutations: C1477R, M1091T, and R587W (4,7-10) and L996P and Q978X (C. Candini et al., manuscript in preparation).
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ABCA1 p.Cys1477Arg 20067955:47:115
status: NEW49 C1477R has been reported in nine heterozygous individuals, M1091T in four individuals, and R587W in seven individuals (11).
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ABCA1 p.Cys1477Arg 20067955:49:0
status: NEW95 Carriers were recruited from five different families (four C1477R carriers, three M1091T carriers, three R587W carriers, four L996P carriers, and one Q978X carrier); family control subjects were siblings, cousins, or partners of a carrier.
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ABCA1 p.Cys1477Arg 20067955:95:59
status: NEW105 This group consisted of four C1477R carriers, two M1091T carriers, one L996P carrier, one Q978X carrier, and eight control subjects.
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ABCA1 p.Cys1477Arg 20067955:105:29
status: NEW[hide] Tangier disease caused by compound heterozygosity ... Atherosclerosis. 2010 Mar;209(1):163-6. Epub 2009 Aug 29. Cameron J, Ranheim T, Halvorsen B, Kulseth MA, Leren TP, Berge KE
Tangier disease caused by compound heterozygosity for ABCA1 mutations R282X and Y1532C.
Atherosclerosis. 2010 Mar;209(1):163-6. Epub 2009 Aug 29., [PMID:19765707]
Abstract [show]
BACKGROUND: Inherited low levels of high density lipoprotein (HDL) cholesterol may be due to mutations in the genes encoding the ATP-binding cassette transporter A1 (ABCA1), apolipoprotein (apo) A-I or lecithin:cholesterol acyltransferase (LCAT). METHODS: The ABCA1, apoA-I and LCAT genes of a 40-year-old male subject with serum HDL cholesterol of 0.06mmol/l were subjected to DNA sequencing. The proband's family was examined for co-segregation between mutations and levels of HDL cholesterol. Cholesterol efflux in fibroblasts from the proband and a normocholesterolemic subject was compared. The effects of an ABCA1 mutation on cholesterol efflux and membrane localization of ABCA1 were studied in transfected HEK293 and HeLa cells, respectively. RESULTS: The proband was a compound heterozygote for ABCA1 mutations R282X (c.844 C>T) and Y1532C (c.4595 A>G). Relatives who were heterozygous for one of these mutations, had about half-normal HDL cholesterol levels. Cholesterol efflux was reduced in fibroblasts from the proband, as was cholesterol efflux from HEK293 cells transfected with an human (h) ABCA1 expression plasmid harboring the Y1532C mutation. Confocal microscopy of HeLa cells transfected with the Y1532C-hABCA1 plasmid revealed that the Y1532C mutation inhibits ABCA1 from reaching the cellular membrane. CONCLUSION: Compound heterozygosity for the nonsense mutation R282X and the missense mutation Y1532C in the ABCA1 gene causes Tangier disease. R282X has a detrimental effect on the function of ABCA1 since a premature stop codon is introduced. Mutation Y1532C disrupts the normal function of ABCA1 as determined by in vitro analyses.
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121 Mutations C1477R and S1506L affecting residues in this loop, have been found to have no effect on the transport of ABCA1 [21], but the mutant proteins encoded by the two mutant alleles interacted much weaker with apoA-I than normal.
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ABCA1 p.Cys1477Arg 19765707:121:10
status: NEW122 Singaraja et al. [22] also showed C1477R-ABCA1 to be present at the cell surface to a similar degree as WT-ABCA1.
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ABCA1 p.Cys1477Arg 19765707:122:34
status: NEW119 Mutations C1477R and S1506L affecting residues in this loop, have been found to have no effect on the transport of ABCA1 [21], but the mutant proteins encoded by the two mutant alleles interacted much weaker with apoA-I than normal.
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ABCA1 p.Cys1477Arg 19765707:119:10
status: NEW120 Singaraja et al. [22] also showed C1477R-ABCA1 to be present at the cell surface to a similar degree as WT-ABCA1.
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ABCA1 p.Cys1477Arg 19765707:120:34
status: NEW[hide] Adenosine-triphosphate-binding cassette transporte... Trends Cardiovasc Med. 2010 Feb;20(2):41-9. Kang MH, Singaraja R, Hayden MR
Adenosine-triphosphate-binding cassette transporter-1 trafficking and function.
Trends Cardiovasc Med. 2010 Feb;20(2):41-9., [PMID:20656214]
Abstract [show]
Mutations in the adenosine-triphosphate-binding cassette transporter-1 (ABCA1) lead to Tangier disease, a genetic disorder characterized by an almost complete absence of plasma high-density lipoprotein cholesterol. Although the importance of ABCA1 localization to its cholesterol efflux function has been extensively characterized, the cellular itinerary of ABCA1 leading to the plasma membrane is not fully elucidated. This review will summarize the current knowledge of ABCA1 trafficking and its relationship to function. Understanding these crucial processes provides potential novel therapeutic targets to regulate high-density lipoprotein biogenesis through influencing pathways of ABCA1 trafficking.
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135 Table 2. Summary of ABCA1 domains involved in trafficking and function Domain Amino acids Role Effect on ABCA1 TD mutations in domain Reference NH2 signal anchor sequence 1-60 Proper insertion of ABCA1 into membrane in a type II orientation ABCA1 protein expression, proper glycosylation Fitzgerald et al. 2001 PEST sequence 1283-1306 Target for calpain protease Controls cell-surface concentration of ABCA1 and ABCA1 degradation D1289N, 1284X Wang et al. 2003 "NDF6F1" sequence 1311-1450 ApoA-I binding ApoA-I binding increases ABCA1 stability and cell-surface expression L1379F Mukhamedova et al. 2007 PDZ binding motif 2259-2261 Binding site for PDZ-containing proteins Interactions with PDZ proteins stabilize ABCA1 Munehira et al. 2004, Okuhira et al. 2005 Table 3. Summary of ABCA1 posttranslational modifications involved in trafficking and function Posttranslational modification Amino acids Effect on ABCA1 TD mutations Reference Disulfide bond formation C75, C309, C1463, C1465, C1477 Two disulfide bonds formed between the Nand C-terminal halves of ABCA1 are required for ABCA1 to be fully functional C1477R Hozoji et al. 2009 Glycosylation N98, N400, N489, N1504, N1637 (predicted) Unknown, but glycosylation often plays a role in proper protein folding, stability, and trafficking Bungert et al. 2001 Palmitoylation C3, C23, C1110, C1111 Localization of ABCA1 at the PM Singaraja et al. 2009 Phosphorylation T1286, T1305 Are constitutively phosphorylated; the dephosphorylation of these residues increases ABCA1 stability Martinez et al. 2003 45TCM Vol. 20, No. 2, Once proteins arrive at the trans-Golgi network (TGN), they are sorted for delivery to multiple destinations including the PM, endosomes, or involvement in retrograde transport.
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ABCA1 p.Cys1477Arg 20656214:135:1112
status: NEW136 Table 2. Summary of ABCA1 domains involved in trafficking and function Domain Amino acids Role Effect on ABCA1 TD mutations in domain Reference NH2 signal anchor sequence 1-60 Proper insertion of ABCA1 into membrane in a type II orientation ABCA1 protein expression, proper glycosylation Fitzgerald et al. 2001 PEST sequence 1283-1306 Target for calpain protease Controls cell-surface concentration of ABCA1 and ABCA1 degradation D1289N, 1284X Wang et al. 2003 "NDF6F1" sequence 1311-1450 ApoA-I binding ApoA-I binding increases ABCA1 stability and cell-surface expression L1379F Mukhamedova et al. 2007 PDZ binding motif 2259-2261 Binding site for PDZ-containing proteins Interactions with PDZ proteins stabilize ABCA1 Munehira et al. 2004, Okuhira et al. 2005 Table 3. Summary of ABCA1 posttranslational modifications involved in trafficking and function Posttranslational modification Amino acids Effect on ABCA1 TD mutations Reference Disulfide bond formation C75, C309, C1463, C1465, C1477 Two disulfide bonds formed between the Nand C-terminal halves of ABCA1 are required for ABCA1 to be fully functional C1477R Hozoji et al. 2009 Glycosylation N98, N400, N489, N1504, N1637 (predicted) Unknown, but glycosylation often plays a role in proper protein folding, stability, and trafficking Bungert et al. 2001 Palmitoylation C3, C23, C1110, C1111 Localization of ABCA1 at the PM Singaraja et al. 2009 Phosphorylation T1286, T1305 Are constitutively phosphorylated; the dephosphorylation of these residues increases ABCA1 stability Martinez et al. 2003 Once proteins arrive at the trans-Golgi network (TGN), they are sorted for delivery to multiple destinations including the PM, endosomes, or involvement in retrograde transport.
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ABCA1 p.Cys1477Arg 20656214:136:1112
status: NEW[hide] A novel missense mutation of ABCA1 in transmembran... Atherosclerosis. 2009 Sep;206(1):216-22. Epub 2009 Feb 25. Maekawa M, Kikuchi J, Kotani K, Nagao K, Odgerel T, Ueda K, Kawano M, Furukawa Y, Sakurabayashi I
A novel missense mutation of ABCA1 in transmembrane alpha-helix in a Japanese patient with Tangier disease.
Atherosclerosis. 2009 Sep;206(1):216-22. Epub 2009 Feb 25., [PMID:19344898]
Abstract [show]
Tangier disease (TD) is a hereditary disorder characterized by the severe deficiency or absence of high-density lipoprotein cholesterol (HDL-C). TD is caused by mutations in the ATP-binding cassette transporter A1 (ABCA1) gene, most of which are located in the extracellular loops and nucleotide-binding domains. Here we describe the first case of TD carrying a missense mutation in a transmembrane alpha-helix of ABCA1. A 31-year-old Japanese woman had an extremely low level of HDL-C (1mg/dl) and yellowish tonsillar swelling, leading to the diagnosis of TD. The proband was homozygous for a point mutation of T4978C in exon 37, which results in the substitution of cysteine-1660 to arginine (C1660R) in the 8th transmembrane segment of ABCA1. Her parents, grandmother, and brother were found to be heterozygous for the same mutation. Both peripheral blood leukocytes from the patient and HEK293 cells transfected with T4978C-mutated ABCA1 normally expressed ABCA1 on the plasma membrane and had normal apolipoprotein A-I-binding ability. However, apolipoprotein A-I-mediated efflux of cholesterol and phospholipids was markedly diminished in HEK293 cells transfected with T4978C-mutated ABCA1. These results suggest that this mutant is normally translated and exists as a stable product with normal localization, yet is functionally defective. Cysteine-1660 appears to be a critical residue for cholesterol transport of ABCA1.
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168 To our knowledge, there is only one case with missense mutation resulting in the substitution of cysteine, i.e., C1477R [2].
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ABCA1 p.Cys1477Arg 19344898:168:113
status: NEW169 The C1477R mutant can be expressed on the cell surface normally, but fails to bind to apo A-I unlike C1660R [18].
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ABCA1 p.Cys1477Arg 19344898:169:4
status: NEW170 This difference may reflect the localization of the mutants: C1477R is in the extracellular loop and C1660R is in the transmembrane domain.
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ABCA1 p.Cys1477Arg 19344898:170:61
status: NEW[hide] Formation of two intramolecular disulfide bonds is... J Biol Chem. 2009 Apr 24;284(17):11293-300. Epub 2009 Mar 3. Hozoji M, Kimura Y, Kioka N, Ueda K
Formation of two intramolecular disulfide bonds is necessary for ApoA-I-dependent cholesterol efflux mediated by ABCA1.
J Biol Chem. 2009 Apr 24;284(17):11293-300. Epub 2009 Mar 3., [PMID:19258317]
Abstract [show]
ABCA1 plays a major role in cholesterol homeostasis and high density lipoprotein (HDL) metabolism. ABCA1 contains disulfide bond(s) between its N- and C-terminal halves, but it remains unclear whether disulfide bond formation is important for the functions of ABCA1 and which cysteines are involved in disulfide bond formation. To answer these questions, we constructed >30 ABCA1 mutants in which 16 extracellular domain (ECD) cysteines were replaced with serines and examined disulfide bond formation, apoA-I binding, and HDL formation in these mutants. From the single cysteine replacements, two cysteines (Cys(75) and Cys(309)) in ECD1 were found to be essential for apoA-I binding. In contrast, in ECD2, only Cys(1477) was found to be essential for HDL formation, and no single cysteine replacement impaired apoA-I binding. The concurrent replacement of two cysteines, Cys(1463) and Cys(1465), impaired apoA-I binding and HDL formation, suggesting that four of five extracellular cysteines (Cys(75), Cys(309), Cys(1463), Cys(1465), and Cys(1477)) are involved in these functions of ABCA1. Trypsin digestion experiments suggested that one disulfide bond is not sufficient and that two intramolecular disulfide bonds (between Cys(75) and Cys(309) in ECD1 and either Cys(1463) or Cys(1465) and Cys(1477) in ECD2) are required for ABCA1 to be fully functional.
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25 Indeed, the Tangier disease mutation C1477R has been reported to abolish apoA-I binding and HDL formation (15-17), and several missense mutations in cysteine residues within ECD1 (C54Y, C75G) and ECD2 (C1488R, C1490Y) of ABCA4 have been linked to Stargardt * Thisworkwassupportedbyagrant-in-aidforscientificresearch(S)fromthe Ministry of Education, Culture, Sports, Science, and Technology of Japan, by the Program for Promotion of Fundamental Studies in Health Sciences of the National Institute of Biomedical Innovation, and by the World Premier International Research Center Initiative, Ministry of Education, Culture, Sports, Science, and Technology of Japan.
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ABCA1 p.Cys1477Arg 19258317:25:37
status: NEW[hide] Severe HDL deficiency due to novel defects in the ... J Intern Med. 2009 Mar;265(3):359-72. Epub 2008 Oct 25. Pisciotta L, Bocchi L, Candini C, Sallo R, Zanotti I, Fasano T, Chakrapani A, Bates T, Bonardi R, Cantafora A, Ball S, Watts G, Bernini F, Calandra S, Bertolini S
Severe HDL deficiency due to novel defects in the ABCA1 transporter.
J Intern Med. 2009 Mar;265(3):359-72. Epub 2008 Oct 25., [PMID:19019193]
Abstract [show]
OBJECTIVES: The objective was the identification and functional characterization of mutations in the ABCA1 gene in four patients with severe HDL deficiency. SUBJECTS: Patients were referred to the clinic because of almost complete HDL deficiency. METHODS: The ABCA1 gene was sequenced directly. The analysis of the ABCA1 protein, ABCA1 mRNA and ABCA1-mediated cholesterol efflux was performed in cultured fibroblasts. Intracellular localization of ABCA1 mutants was investigated in transfected HEK293 cells. RESULTS: Two patients were homozygous for mutations in the coding region of the ABCA1 gene, resulting in an amino acid substitution (p.A1046D) and a truncated protein (p.I74YFsX76). The third patient was homozygous for a splice site mutation in intron 35 (c.4773 + 1g>a), resulting in an in-frame deletion of 25 amino acids (del p.D1567_K1591) in ABCA1. These patients had clinical manifestations of accumulation of cholesterol in the reticulo-endothelial system. The fourth patient, with preclinical atherosclerosis, was a compound heterozygote for two missense mutations (p.R587W/p.W1699C). ABCA1-mediated cholesterol efflux was abolished in fibroblasts from patients with p.A1046D and del p.D1567_K1591 mutants and in fibroblasts homozygous for p.R587W. A reduced ABCA1 protein content was observed in these cells, suggesting an increased intracellular degradation. The mutant p.W1699C was largely retained in the endoplasmic reticulum, when expressed in HEK293 cells. CONCLUSIONS: The homozygotes for mutations which abolish ABCA1 function showed overt signs of involvement of the reticulo-endothelial system. This was not the case in the compound heterozygote for missense mutations, suggesting that this patient retains some residual ABCA1 function that reduces cholesterol accumulation in the reticulo-endothelial system.
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197 Previous studies have shown that two missense ABCA1 mutants (p.C1477R and p.S1506L) located in the second extracellular loop, when expressed in transfected cells, exhibited a dramatic reduction in the interaction capacity with Apo A-I [27].
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ABCA1 p.Cys1477Arg 19019193:197:63
status: NEW[hide] ABCA1 mutants reveal an interdependency between li... J Lipid Res. 2009 Feb;50(2):285-92. Epub 2008 Sep 5. Vaughan AM, Tang C, Oram JF
ABCA1 mutants reveal an interdependency between lipid export function, apoA-I binding activity, and Janus kinase 2 activation.
J Lipid Res. 2009 Feb;50(2):285-92. Epub 2008 Sep 5., [PMID:18776170]
Abstract [show]
ABCA1 exports cholesterol and phospholipids from cells by a multistep pathway that involves forming cell surface lipid domains, solubilizing these lipids by apolipoproteins, binding of apolipoproteins to ABCA1, and activating signaling processes. Here we used a mutational analysis approach to evaluate the relationship between these events. We prepared seven naturally occurring mutants and one artificial missense mutant of ABCA1 with varying degrees of impaired function, expressed them to similar levels as wild-type ABCA1 on the cell surface of BHK cells, and measured ABCA1-dependent lipid export, apolipoprotein A-I (apoA-I) binding, and signaling activities. Linear regression analyses showed that cholesterol and phospholipid efflux and cellular apoA-I binding correlated significantly with the ability of ABCA1 to form cell surface lipid domains. Lipid export and cellular apoA-I binding activities and formation of lipid domains also correlated with the amount of apoA-I that could be cross-linked to ABCA1. Moreover, each of these lipid export and apoA-I binding activities correlated with apoA-I-induced Janus kinase 2 (JAK2) activation. Thus, these missense mutations in ABCA1 impair lipid export, apoA-I binding, and apoA-I-stimulated JAK2 activities to similar extents, indicating that these processes are highly interactive components of a pathway that functions to export lipids from cells.
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No. Sentence Comment
49 the first extracellular loop (V399A, R587W, W590S, and Q597R), two were in the second extracellular loop (C1477R and I1517R), and one was in the Walker A motif of the first nucleotide binding domain (A937V, NBD1) (Fig. 1).
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ABCA1 p.Cys1477Arg 18776170:49:106
status: NEW96 Fitzgerald et al. (24) reported similar cell surface localizations for mutants R587W, W590S, Q597R, and C1477R.
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ABCA1 p.Cys1477Arg 18776170:96:104
status: NEW95 Fitzgerald et al. (24) reported similar cell surface localizations for mutants R587W, W590S, Q597R, and C1477R.
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ABCA1 p.Cys1477Arg 18776170:95:104
status: NEW[hide] Effect of ABCA1 mutations on risk for myocardial i... Curr Atheroscler Rep. 2008 Oct;10(5):413-26. Iatan I, Alrasadi K, Ruel I, Alwaili K, Genest J
Effect of ABCA1 mutations on risk for myocardial infarction.
Curr Atheroscler Rep. 2008 Oct;10(5):413-26., [PMID:18706283]
Abstract [show]
The adenosine triphosphate-binding cassette A1 (ABCA1) gene codes for a cellular phospholipid and cholesterol transporter that mediates the initial and essential step in high-density lipoprotein (HDL) biogenesis: the formation of nascent HDL particles. Mutations at the ABCA1 gene locus cause severe familial HDL deficiency and, in the homozygous form, cause Tangier disease. Several studies have investigated the influence of ABCA1 variation on lipid metabolism and coronary heart disease, but they have resulted in controversial and inconsistent results. Genetic variability at the ABCA1 gene has also been associated with increased risk of myocardial infarction. In one study, this association was independent of HDL cholesterol levels, raising the possibility that the measurement of HDL cholesterol levels may not provide adequate information on the functional roles of HDL particles. Nevertheless, genomic screening for complex diseases, such as coronary heart disease, and HDL deficiency in particular, may not add additional information to that gained from conventional global cardiovascular risk stratification.
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No. Sentence Comment
119 Genetic variation in ABCA1 and risk of myocardial infarction Study* / year Population screened HDL-C, mmol/L ABCA1 variants Conclusions Clee et al. [28] / 2000 Within 11 TD families: Del L693, R2144X † , Del E,D1893,94 † , R909X, M1091T † , P2150L † , ivs25+1G→C, Del C6825→2145X, CTC6952- 4TT→2203X, C1477R, Q597R, T929I ABCA1 heterozygous patients had a 40%-45% decrease in HDL-C and a greater than threefold increased risk of CHD versus unaffected individuals.
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ABCA1 p.Cys1477Arg 18706283:119:350
status: NEW[hide] Quantitative analysis of ABCA1-dependent compartme... J Biol Chem. 2008 Apr 25;283(17):11164-75. Epub 2008 Jan 24. Hassan HH, Bailey D, Lee DY, Iatan I, Hafiane A, Ruel I, Krimbou L, Genest J
Quantitative analysis of ABCA1-dependent compartmentalization and trafficking of apolipoprotein A-I: implications for determining cellular kinetics of nascent high density lipoprotein biogenesis.
J Biol Chem. 2008 Apr 25;283(17):11164-75. Epub 2008 Jan 24., [PMID:18218626]
Abstract [show]
The molecular mechanisms underlying the apoA-I/ABCA1 endocytic trafficking pathway in relation to high density lipoprotein (HDL) formation remain poorly understood. We have developed a quantitative cell surface biotinylation assay to determine the compartmentalization and trafficking of apoA-I between the plasma membrane (PM) and intracellular compartments (ICCs). Here we report that (125)I-apoA-I exhibited saturable association with the PM and ICCs in baby hamster kidney cells stably overexpressing ABCA1 and in fibroblasts. The PM was found to have a 2-fold higher capacity to accommodate apoA-I as compared with ICCs. Overexpressing various levels of ABCA1 in baby hamster kidney cells promoted the association of apoA-I with PM and ICCs compartments. The C-terminal deletion of apoA-I Delta(187-243) and reconstituted HDL particles exhibited reduced association of apoA-I with both the PM and ICCs. Interestingly, cell surface biotinylation with a cleavable biotin revealed that apoA-I induces ABCA1 endocytosis. Such endocytosis was impaired by naturally occurring mutations of ABCA1 (Q597R and C1477R). To better understand the role of the endocytotic pathway in the dynamics of the lipidation of apoA-I, a pulse-chase experiment was performed, and the dissociation (re-secretion) of (125)I-apoA-I from both PM and ICCs was monitored over a 6-h period. Unexpectedly, we found that the time required for 50% dissociation of (125)I-apoA-I from the PM was 4-fold slower than that from ICCs at 37 degrees C. Finally, treatment of the cells with phosphatidylcholine-specific phospholipase C, increased the dissociation of apoA-I from the PM. This study provides evidence that the lipidation of apoA-I occurs in two kinetically distinguishable compartments. The finding that apoA-I specifically mediates the continuous endocytic recycling of ABCA1, together with the kinetic data showing that apoA-I associated with ICCs is rapidly re-secreted, suggests that the endocytotic pathway plays a central role in the genesis of nascent HDL.
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No. Sentence Comment
7 Such endocytosis was impaired by naturally occurring mutations of ABCA1 (Q597R and C1477R).
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ABCA1 p.Cys1477Arg 18218626:7:83
status: NEW35 EXPERIMENTAL PROCEDURES Patient Selection-For this study, we selected fibroblasts from three normal control subjects and two patients with TD (homozygous for Q597R at the ABCA1 gene and compound heterozygous for C1477R as described previously (12)).
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ABCA1 p.Cys1477Arg 18218626:35:212
status: NEW71 Cellular Compartmentalization and Trafficking of ApoA-I/ABCA1 APRIL 25, 2008•VOLUME 283•NUMBER 17 JOURNAL OF BIOLOGICAL CHEMISTRY 11165 Dissociation of 125 I-ApoA-I from Intact Cells-BHK-ABCA1, normal human fibroblasts, or fibroblasts with ABCA1 mutations (Q597R and C1477R) from Tangier disease subjects were used.
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ABCA1 p.Cys1477Arg 18218626:71:282
status: NEW174 Similar results were obtained with normal fibroblasts but not TD mutants (Q597R and C1477R).
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ABCA1 p.Cys1477Arg 18218626:174:84
status: NEW176 Furthermore, we found that apoA-I-mediated ABCA1 internalization was impaired in the ABCA1 mutant (C1477R) associated with TD (data not shown).
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ABCA1 p.Cys1477Arg 18218626:176:99
status: NEW36 EXPERIMENTAL PROCEDURES Patient Selection-For this study, we selected fibroblasts from three normal control subjects and two patients with TD (homozygous for Q597R at the ABCA1 gene and compound heterozygous for C1477R as described previously (12)).
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ABCA1 p.Cys1477Arg 18218626:36:212
status: NEW73 Cellular Compartmentalization and Trafficking of ApoA-I/ABCA1 APRIL 25, 2008ߦVOLUME 283ߦNUMBER 17 JOURNAL OF BIOLOGICAL CHEMISTRY 11165 at SEMMELWEIS UNIV OF MEDICINE on December 3, Dissociation of 125 I-ApoA-I from Intact Cells-BHK-ABCA1, normal human fibroblasts, or fibroblasts with ABCA1 mutations (Q597R and C1477R) from Tangier disease subjects were used.
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ABCA1 p.Cys1477Arg 18218626:73:326
status: NEW182 Similar results were obtained with normal fibroblasts but not TD mutants (Q597R and C1477R).
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ABCA1 p.Cys1477Arg 18218626:182:84
status: NEW185 Furthermore, we found that apoA-I-mediated ABCA1 internalization was impaired in the ABCA1 mutant (C1477R) associated with TD (data not shown).
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ABCA1 p.Cys1477Arg 18218626:185:99
status: NEW[hide] The role of different regions of ATP-binding casse... Biochemistry. 2007 Aug 21;46(33):9388-98. Epub 2007 Jul 26. Mukhamedova N, Fu Y, Bukrinsky M, Remaley AT, Sviridov D
The role of different regions of ATP-binding cassette transporter A1 in cholesterol efflux.
Biochemistry. 2007 Aug 21;46(33):9388-98. Epub 2007 Jul 26., [PMID:17655203]
Abstract [show]
ABCA1 is a key element of cholesterol efflux, but the mechanism of ABCA1-dependent cholesterol efflux is still unclear. Monoclonal antibodies against ABCA1 were used to map functional domains of ABCA1. Two antibodies were directed against a fragment of the first extracellular loop of ABCA1, and the third antibody was directed against a fragment of the fourth extracellular loop. One antibody against the first loop inhibited cholesterol efflux from human macrophages without inhibiting apolipoprotein A-I (apoA-I) binding and internalization. Another antibody against the first loop inhibited apoA-I binding and internalization without inhibiting cholesterol efflux. The antibody against the fourth loop inhibited apoA-I binding to ABCA1 but enhanced cholesterol efflux from macrophages and reduced intracellular cholesterol content. This antibody also increased cholesterol efflux from HeLa cells transfected with ABCA1 but not from cells with DeltaPEST-ABCA1. The mechanism of the stimulating effect of this antibody on cholesterol efflux was found to be stabilization of ABCA1 leading to the increase in abundance of cell surface ABCA1. We conclude that a site on the first extracellular loop is required for cholesterol efflux, whereas a site on the fourth extracellular loop may be responsible for ABCA1 stability.
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No. Sentence Comment
269 Natural mutations found in the Tangier pedigree, R587W, W590S, Q597R, and S1506L, as well as generated mutant C1477R strongly inhibited cholesterol and phospholipid efflux (28, 35, 36) and, with the exception of W590S, also apoA-I binding (36).
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ABCA1 p.Cys1477Arg 17655203:269:110
status: NEW[hide] Genetic etiology of isolated low HDL syndrome: inc... Arterioscler Thromb Vasc Biol. 2007 May;27(5):1139-45. Epub 2007 Feb 15. Kiss RS, Kavaslar N, Okuhira K, Freeman MW, Walter S, Milne RW, McPherson R, Marcel YL
Genetic etiology of isolated low HDL syndrome: incidence and heterogeneity of efflux defects.
Arterioscler Thromb Vasc Biol. 2007 May;27(5):1139-45. Epub 2007 Feb 15., [PMID:17303779]
Abstract [show]
OBJECTIVE: We have used a multitiered approach to identify genetic and cellular contributors to high-density lipoprotein (HDL) deficiency in 124 human subjects. METHODS AND RESULTS: We resequenced 4 candidate genes for HDL regulation and identified several functional nonsynonymous mutations including 2 in apolipoprotein A-I (APOA1), 4 in lecithin:cholesterol acyltransferase (LCAT), 1 in phospholipid transfer protein (PLTP), and 7 in the ATP-binding cassette transporter ABCA1, leaving 88% (110/124) of HDL deficient subjects without a genetic diagnosis. Cholesterol efflux assays performed using cholesterol-loaded monocyte-derived macrophages from the 124 low HDL subjects and 48 control subjects revealed that 33% (41/124) of low HDL subjects had low efflux, despite the fact that the majority of these subjects (34/41) were not carriers of dysfunctional ABCA1 alleles. In contrast, only 2% of control subjects presented with low efflux (1/48). In 3 families without ABCA1 mutations, efflux defects were found to cosegregate with low HDL. CONCLUSIONS: Efflux defects are frequent in low HDL syndromes, but the majority of HDL deficient subjects with cellular cholesterol efflux defects do not harbor ABCA1 mutations, suggesting that novel pathways contribute to this phenotype.
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No. Sentence Comment
47 In ABCA1, a total of 19 nonsynonymous coding sequence variants; some of these we reported previously.22 Of these, 9 sequence variants were common polymorphisms (ie, reported in the literature as common or of similar prevalence in control subjects): P85L, P85A, R219K, V399A, V771M, V825I, I883M, E1172D, R1587K.14,32-35 Another 5 sequence variants, identified here, were previously reported to be disease causing: W590L (reported as W590S)14; C1477F (reported as C1477R)13; S1731C (only found in French-Canadian populations)36; N1800H32; and 1851X.37 Five sequence variants were novel: K199F, H551D, R965C, E1386Q, and D1706N.
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ABCA1 p.Cys1477Arg 17303779:47:463
status: NEW42 In ABCA1, a total of 19 nonsynonymous coding sequence variants; some of these we reported previously.22 Of these, 9 sequence variants were common polymorphisms (ie, reported in the literature as common or of similar prevalence in control subjects): P85L, P85A, R219K, V399A, V771M, V825I, I883M, E1172D, R1587K.14,32-35 Another 5 sequence variants, identified here, were previously reported to be disease causing: W590L (reported as W590S)14; C1477F (reported as C1477R)13; S1731C (only found in French-Canadian populations)36; N1800H32; and 1851X.37 Five sequence variants were novel: K199F, H551D, R965C, E1386Q, and D1706N.
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ABCA1 p.Cys1477Arg 17303779:42:463
status: NEW[hide] Specific mutations in ABCA1 have discrete effects ... Circ Res. 2006 Aug 18;99(4):389-97. Epub 2006 Jul 27. Singaraja RR, Visscher H, James ER, Chroni A, Coutinho JM, Brunham LR, Kang MH, Zannis VI, Chimini G, Hayden MR
Specific mutations in ABCA1 have discrete effects on ABCA1 function and lipid phenotypes both in vivo and in vitro.
Circ Res. 2006 Aug 18;99(4):389-97. Epub 2006 Jul 27., [PMID:16873719]
Abstract [show]
Mutations in ATP-binding cassette transporter A1 (ABCA1) cause Tangier disease and familial hypoalphalipoproteinemia, resulting in low to absent plasma high-density lipoprotein cholesterol levels. However, wide variations in clinical lipid phenotypes are observed in patients with mutations in ABCA1. We hypothesized that the various lipid phenotypes would be the direct result of discrete and differing effects of the mutations on ABCA1 function. To determine whether there is a correlation between the mutations and the resulting phenotypes, we generated in vitro 15 missense mutations that have been described in patients with Tangier disease and familial hypoalphalipoproteinemia. Using localization of ABCA1, its ability to induce cell surface binding of apolipoprotein A-I, and its ability to elicit efflux of cholesterol and phospholipids to apolipoprotein A-I we determined that the phenotypes of patients correlate with the severity and nature of defects in ABCA1 function.
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46 Indeed, patients heterozygous for the mutations R587W, Q597R, ⌬L693, N935S, A1046D, C1477R, and R2081W had between 47% and 69% of HDL-C levels of controls (Table).
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ABCA1 p.Cys1477Arg 16873719:46:90
status: NEW49 In contrast, C1477R, D1289N, and P2150L showed similar distribution to wild-type ABCA1, indicating that these mutants cause defects despite their normal localization at the plasma membrane.
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ABCA1 p.Cys1477Arg 16873719:49:13
status: NEW55 R2081W, along with the mutants localizing to the plasma membrane by fluorescence, D1289N, C1477R, and P2150L, showed both EndoH resistant and sensitive bands, indicating that they are distributed at the ER and at the Golgi, thus confirming the GFP localization data.
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ABCA1 p.Cys1477Arg 16873719:55:90
status: NEW59 By contrast, D1289N, C1477R, and P2150L were at the plasma membrane in similar quantities as wild-type ABCA1(Figure 2C), also confirming our previous localization data.
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ABCA1 p.Cys1477Arg 16873719:59:21
status: NEW70 Interestingly however, C1477R, which localized to the plasma membrane elicited almost no ApoA-I binding (19.04Ϯ3.9%, nϭ3, Pϭ0.0008) (Figure 3A), indicating that although plasma membrane localization of ABCA1 is essential, it is not sufficient for ApoA-I binding.
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ABCA1 p.Cys1477Arg 16873719:70:23
status: NEW79 A1046D and S1506L showed reduced localization at the plasma membrane, and C1477R, D1289L, and P2150L showed localization at the plasma membrane and intracellularly.
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ABCA1 p.Cys1477Arg 16873719:79:74
status: NEW82 C1477R, S1506L, and R2081W show both EndoH sensitive and resistant bands indicating localization at both the ER and the plasma membrane.
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ABCA1 p.Cys1477Arg 16873719:82:0
status: NEW84 D1289N, C1477R, and P2150L showed normal ABCA1 localization at the membrane.
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ABCA1 p.Cys1477Arg 16873719:84:8
status: NEW87 Of the 3 mutants showing plasma membrane localization, C1477R showed significantly reduced lipid efflux.
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ABCA1 p.Cys1477Arg 16873719:87:55
status: NEW88 Because C1477R showed diminished cell surface ApoA-I binding, this finding indicates that ApoA-I binding is required for ABCA1-mediated lipid efflux.
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ABCA1 p.Cys1477Arg 16873719:88:8
status: NEW148 C1477R, however, did reach the plasma membrane, similar to wild-type ABCA1.
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ABCA1 p.Cys1477Arg 16873719:148:0
status: NEW150 The defect in the C1477R mutant suggests that although plasma membrane localization is critical for lipid efflux, clearly other mechanisms must result in the failure to recruit ApoA-I.
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ABCA1 p.Cys1477Arg 16873719:150:18
status: NEW151 C1477R is localized within the second large extracellular loop in ABCA1, and studies in the related transporter ABCA4 revealed that its 2 large extracellular loops interact with each other through disulfide bonds.26 Because ABCA4 and ABCA1 are closely related, it is possible that the disrupted cysteine in the second large extracellular loop in ABCA1 may also prevent interaction between the 2 large extracellular loops, which could be essential for cell surface ApoA-I binding and lipid efflux.
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ABCA1 p.Cys1477Arg 16873719:151:0
status: NEW[hide] Transition from dimers to higher oligomeric forms ... J Biol Chem. 2006 Jul 21;281(29):20283-90. Epub 2006 May 18. Trompier D, Alibert M, Davanture S, Hamon Y, Pierres M, Chimini G
Transition from dimers to higher oligomeric forms occurs during the ATPase cycle of the ABCA1 transporter.
J Biol Chem. 2006 Jul 21;281(29):20283-90. Epub 2006 May 18., [PMID:16709568]
Abstract [show]
Fluorescence resonance energy transfer and native PAGE analytical techniques were employed to assess the quaternary structure of ABCA1, an ATP binding cassette transporter playing a crucial role in cellular lipid handling. These experimental approaches support the conclusion that ABCA1 is associated in dimeric structures that undergo transition into higher order structures, i.e. tetramers, during the ATP catalytic cycle. Our data hence underline molecular assembly as a crucial parameter in ABCA1 function and the advantage of native PAGE as analytical tool for intractable membrane proteins.
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No. Sentence Comment
128 We chose to analyze W590S and C1477R, two Tangier-associated mutations previously characterized and known to differentially affect the ABCA1-induced binding of apoA-I and annexin V (3, 32).
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ABCA1 p.Cys1477Arg 16709568:128:30
status: NEW133 A:D ratio < 2.5 A:D ratio > 2.5 N-ter 14.86 Ϯ 1.4 19.11 Ϯ 1.3 YABCA1/CABCA1 n ϭ 11 n ϭ 17 Nand C-ter 17.72 Ϯ 2.1 18.91 Ϯ 2.312 C Y ABCA1/ABCA1 Y C n ϭ 11 n ϭ 8 C-ter 11.74 Ϯ 0.85 24.00 Ϯ 1.001 ABCA1Y/ABCA1C n ϭ 29 n ϭ 21 W590S 11.79 Ϯ 1.230 26.54 Ϯ 1.004 W590SY/W590SC n ϭ 12 n ϭ 30 C1477R 13.70 Ϯ 0.7299 26.50 Ϯ 1.462 C1477RY/C1477RC n ϭ 27 n ϭ 22 ABCA1MM 11.83 Ϯ 1.048 26.59 Ϯ 1.591 ABCA1MMY/ABCA1MMC n ϭ 14 n ϭ 15 Oligomerization of the ABCA1 Transporter 20286 constructs supported dimerization since an efficiency of the energy transfer similar to that of wild type and similarly sensitive to variations in acceptor-to-donor ratios was detected (Fig. 4, A and B, and Table 1).
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ABCA1 p.Cys1477Arg 16709568:133:91
status: NEWX
ABCA1 p.Cys1477Arg 16709568:133:379
status: NEW134 However, upon fractionation on native PAGE, the lysates of cells transfected with W590S or C1477R showed a higher molecular mass band migrating at Ͼ800 kDa and accounting for 9 and 27%, respectively, of the total ABCA1 signal (Fig. 4C, upper panel), in the absence of any modification of expression levels as shown by the SDS-PAGE analysis (Fig. 4C, lower panel).
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ABCA1 p.Cys1477Arg 16709568:134:91
status: NEW180 A and B, imaging FRET of cells expressing appropriately tagged W590S or C1477R, two ABCA1 variants associated with Tangier disease and variably affecting the functional readouts associated with ABCA1 expression.
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ABCA1 p.Cys1477Arg 16709568:180:72
status: NEW127 We chose to analyze W590S and C1477R, two Tangier-associated mutations previously characterized and known to differentially affect the ABCA1-induced binding of apoA-I and annexin V (3, 32).
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ABCA1 p.Cys1477Arg 16709568:127:30
status: NEW132 A:D ratio < 2.5 A:D ratio > 2.5 N-ter 14.86 afe; 1.4 19.11 afe; 1.3 YABCA1/CABCA1 n afd; 11 n afd; 17 Nand C-ter 17.72 afe; 2.1 18.91 afe; 2.312 C Y ABCA1/ABCA1 Y C n afd; 11 n afd; 8 C-ter 11.74 afe; 0.85 24.00 afe; 1.001 ABCA1Y/ABCA1C n afd; 29 n afd; 21 W590S 11.79 afe; 1.230 26.54 afe; 1.004 W590SY/W590SC n afd; 12 n afd; 30 C1477R 13.70 afe; 0.7299 26.50 afe; 1.462 C1477RY/C1477RC n afd; 27 n afd; 22 ABCA1MM 11.83 afe; 1.048 26.59 afe; 1.591 ABCA1MMY/ABCA1MMC n afd; 14 n afd; 15 Oligomerization of the ABCA1 Transporter 20286 JOURNAL OF BIOLOGICAL CHEMISTRY VOLUME 281ߦNUMBER 29ߦJULY 21, 2006 at SEMMELWEIS UNIV OF MEDICINE on December 3, constructs supported dimerization since an efficiency of the energy transfer similar to that of wild type and similarly sensitive to variations in acceptor-to-donor ratios was detected (Fig. 4, A and B, and Table 1).
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ABCA1 p.Cys1477Arg 16709568:132:379
status: NEW179 A and B, imaging FRET of cells expressing appropriately tagged W590S or C1477R, two ABCA1 variants associated with Tangier disease and variably affecting the functional readouts associated with ABCA1 expression.
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ABCA1 p.Cys1477Arg 16709568:179:72
status: NEW[hide] New insights into the biogenesis of human high-den... Curr Opin Lipidol. 2006 Jun;17(3):258-67. Krimbou L, Marcil M, Genest J
New insights into the biogenesis of human high-density lipoproteins.
Curr Opin Lipidol. 2006 Jun;17(3):258-67., [PMID:16680030]
Abstract [show]
PURPOSE OF REVIEW: The interest for the human HDL system was recently revived by the identification of the ABCA1 as a critical component in the formation and maintenance of plasma HDL levels. The present review focuses on recent progress in our understanding of the basic mechanisms underlying HDL biogenesis pathways. RECENT FINDINGS: Several novel mechanisms governing ABCA1/apoA-I interactions have recently been identified: apolipoprotein A-I activates ABCA1 phosphorylation through the cAMP/protein kinase A-dependent pathway; the majority of ABCA1 exists as a tetramer in human living cell, supporting the concept that the homotetrameric ABCA1 complex constitutes the minimum functional unit for the formation of nascent HDL particles; apolipoprotein A-I has been shown to have a recycling retroendocytic pathway with uptake and resecretion of the lipidated nascent HDL particles by the cell, most likely through the ABCA1 transporter pathway; there is evidence that the speciation of nascent HDL into pre-beta and alpha-HDL is linked to specific cell lines, and occurs by both ABCA1-dependent and independent pathways. SUMMARY: The fundamental mechanisms underlying the biogenesis, speciation and maturation of HDL remain complex and not well understood. Understanding the mechanisms governing HDL genesis at the cellular level could provide novel insights into the human atheroprotective system in health and disease.
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No. Sentence Comment
55 We have previously shown [40], however, that incubation of lipid-free apoE3 with normal fibroblasts generated nascent apoE3/cholesterol/phospholipid complexes that exhibited preb-electrophoretic mobility with a particle size ranging from 9 to 15 nm, whereas lipid-free apoE3 incubated with ABCA1 mutant (C1477R) cells was unable to form such particles.
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ABCA1 p.Cys1477Arg 16680030:55:304
status: NEW63 We have previously suggested that the high content in phosphatidylinositol [41] or the high number of apoA-I molecules per particle [43] (Fig. 2b, lower panels) may contribute to the increase in the net negative charge of nascent LpA-I and consequently cause 260 Lipid metabolism Table 1 Formation and speciation of nascent apolipoprotein (apo)A-I-containing particles in various cell lines Cell type Pre-b1-LpA-I a-LpA-I Macrophages monocyte-derived þ þ THP-1 þ þ Hepatocytes HepG2 (apoA-I endo, exo) þ þ primary mouse (apoA-I endo) þ þ CaCo-2 (apoA-I endo, exo) - þ Fibroblasts normal - þ Tangier (Q597R) - - Tangier (C1477R) - - HUVEC - - CHO - þ CHO overexpressing ABCA1 - þ The presence of pre-b1-LpA-I and a-LpA-I generated by different cell lines was determined by two-dimensional polyacrylamide nondenaturing gradient gel electrophoresis based on our previous study [28].
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ABCA1 p.Cys1477Arg 16680030:63:670
status: NEW[hide] Apolipoprotein A-I activates Cdc42 signaling throu... J Lipid Res. 2006 Apr;47(4):794-803. Epub 2006 Jan 28. Nofer JR, Remaley AT, Feuerborn R, Wolinnska I, Engel T, von Eckardstein A, Assmann G
Apolipoprotein A-I activates Cdc42 signaling through the ABCA1 transporter.
J Lipid Res. 2006 Apr;47(4):794-803. Epub 2006 Jan 28., [PMID:16443932]
Abstract [show]
It has been suggested that the signal transduction initiated by apolipoprotein A-I (apoA-I) activates key proteins involved in cholesterol efflux. ABCA1 serves as a binding partner for apoA-I, but its participation in apoA-I-induced signaling remains uncertain. We show that the exposure of human fibroblasts to ABCA1 ligands (apolipoproteins and amphipathic helical peptides) results in the generation of intracellular signals, including activation of the small G-protein Cdc42, protein kinases (PAK-1 and p54JNK), and actin polymerization. ApoA-I-induced signaling was abrogated by glyburide, an inhibitor of the ABC transporter family, and in fibroblasts from patients with Tangier disease, which do not express ABCA1. Conversely, induction of ABCA1 expression with the liver X receptor agonist, T0901317, and the retinoid X receptor agonist, R0264456, potentiated apoA-I-induced signaling. Similar effects were observed in HEK293 cells overexpressing ABCA1-green fluorescent protein (GFP) fusion protein, but not ABCA1-GFP (K939M), which fails to hydrolyze ATP, or a nonfunctional ABCA1-GFP with a truncated C terminus. We further found that Cdc42 coimmunoprecipitates with ABCA1 in ABCA1-GFP-expressing HEK293 cells exposed to apoA-I but not in cells expressing ABCA1 mutants. We conclude that ABCA1 transduces signals from apoA-I by complexing and activating Cdc42 and downstream kinases and, therefore, acts as a full apoA-I receptor.
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No. Sentence Comment
192 Another ABCA1 variant, C1477R, was shown by Haidar et al. (8) to be fully ineffective at mediating apoA-I-dependent cAMP formation and effluxing cholesterol, despite there being only partially decreased apoA-I binding.
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ABCA1 p.Cys1477Arg 16443932:192:23
status: NEW190 Another ABCA1 variant, C1477R, was shown by Haidar et al. (8) to be fully ineffective at mediating apoA-I-dependent cAMP formation and effluxing cholesterol, despite there being only partially decreased apoA-I binding.
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ABCA1 p.Cys1477Arg 16443932:190:23
status: NEW[hide] Role of apoA-I, ABCA1, LCAT, and SR-BI in the biog... J Mol Med (Berl). 2006 Apr;84(4):276-94. Epub 2006 Feb 25. Zannis VI, Chroni A, Krieger M
Role of apoA-I, ABCA1, LCAT, and SR-BI in the biogenesis of HDL.
J Mol Med (Berl). 2006 Apr;84(4):276-94. Epub 2006 Feb 25., [PMID:16501936]
Abstract [show]
The concentration, composition, shape, and size of plasma high-density lipoprotein (HDL) are determined by numerous proteins that influence its biogenesis, remodeling, and catabolism. The discoveries of the HDL receptor (scavenger receptor class B type I, SR-BI) and the ABCA1 (ATP-binding cassette transporter A1) lipid transporter provided two missing links that were necessary to understand the biogenesis and some of the functions of HDL. Existing data indicate that functional interactions between apoA-I and ABCA1 are necessary for the initial lipidation of apoA-I. Through a series of intermediate steps, lipidated apoA-I proceeds to form discoidal HDL particles that can be converted to spherical particles by the action of lecithin:cholesterol acyltransferase (LCAT). Discoidal and spherical HDL can interact functionally with SR-BI and these interactions lead to selective lipid uptake and net efflux of cholesterol and thus remodel HDL. Defective apoA-I/ABCA1 interactions prevent lipidation of apoA-I that is necessary for the formation of HDL particles. In the same way, specific mutations in apoA-I or LCAT prevent the conversion of discoidal to spherical HDL particles. The interactions of lipid-bound apoA-I with SR-BI are affected in vitro by specific mutations in apoA-I or SR-BI. Furthermore, deficiency of SR-BI affects the lipid and apolipoprotein composition of HDL and is associated with increased susceptibility to atherosclerosis. Here we review the current status of the pathway of HDL biogenesis and mutations in apoA-I, ABCA1, and SR-BI that disrupt different steps of the pathway and may lead to dyslipidemia and atherosclerosis in mouse models. The phenotypes generated in experimental mouse models for apoA-I, ABCA1, LCAT, SR-BI, and other proteins of the HDL pathway may facilitate early diagnosis of similar phenotypes in the human population and provide guidance for proper treatment.
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147 In vitro analysis of the effects on apoA-I/ABCA1 interactions (cross-linking assay) by mutations in ABCA1 that are found in Tangier disease patients and diminish lipid efflux [71] showed that cross-linking was dramatically reduced to 5-10% of the WT control for three mutants (Gln597Arg, Cys1477Arg, and Ser1506Leu), reduced by 50% for the Arg587Trp mutant, and was remarkably increased to 125% of control for the Trp590Ser mutant [71].
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ABCA1 p.Cys1477Arg 16501936:147:288
status: NEW[hide] Variations on a gene: rare and common variants in ... Annu Rev Nutr. 2006;26:105-29. Brunham LR, Singaraja RR, Hayden MR
Variations on a gene: rare and common variants in ABCA1 and their impact on HDL cholesterol levels and atherosclerosis.
Annu Rev Nutr. 2006;26:105-29., [PMID:16704350]
Abstract [show]
Cholesterol and its metabolites play a variety of essential roles in living systems. Virtually all animal cells require cholesterol, which they acquire through synthesis or uptake, but only the liver can degrade cholesterol. The ABCA1 gene product regulates the rate-controlling step in the removal of cellular cholesterol: the efflux of cellular cholesterol and phospholipids to an apolipoprotein acceptor. Mutations in ABCA1, as seen in Tangier disease, result in accumulation of cellular cholesterol, reduced plasma high-density lipoprotein cholesterol, and increased risk for coronary artery disease. To date, more than 100 coding variants have been identified in ABCA1, and these variants result in a broad spectrum of biochemical and clinical phenotypes. Here we review genetic variation in ABCA1 and its critical role in cholesterol metabolism and atherosclerosis in the general population.
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555 Since a complete loss of function allele would be expected to result in a 50% reduction in HDL levels, a greater than 50% reduction in HDL is most likely explained by a dominant negative allele, in which TABLE 3 Patient phenotypes associated with heterozygous ABCA1 mutations Mutation HDL (mmol/L) HDL (% of control) Number of patients M1091T 0.48 ± 0.5 30 ± 30 4 G1216V 0.50 40 1 R2144X 0.56 ± 0.2 41 ± 18 12 R282X 0.52 41 1 R909X 0.59 ± 0.3 42 ± 19 5 K776N 0.55 ± 0.1 47 ± 5 2 R587W 0.61 ± 0.1 47 ± 8 7 S364C 0.60 48 1 P1065S 0.80 51 1 c-ter deletion 0.75 53 1 N1800H - 56.5 33 P85L 0.72 ± 0.4 57 ± 33 5 Del693L 0.79 ± 0.2 57 ± 15 8 D1289N 0.80 ± 0.1 59 ± 12 4 R2081W 0.80 ± 0.1 59 ± 12 4 2203X 0.80 ± 0.2 59 ± 20 4 DelED1893,4 0.77 ± 0.2 59 ± 18 8 2145X 0.82 ± 0.1 59 ± 9 4 A1046D 0.70 ± 0.1 60 ± 8 2 Q597R 0.82 ± 0.1 60 ± 5 5 C1477R 0.82 ± 0.2 61 ± 15 9 IVS25 + 1G > C 0.78 ± 0.1 62 ± 12 4 D1099Y 0.83 ± 0.3 63 ± 21 5 1552X 1.00 64 1 F2009S 0.82 ± 0.2 64 ± 19 6 R587W 0.86 ± 0.1 65 ± 17 2 R1068H 0.90 ± 0.3 67 ± 26 9 N935S 1.00 ± 0.3 74 ± 16 7 T929I 1.01 ± 0.2 76 ± 7 8 1284X 1.11 ± 0.2 83 ± 14 5 A937V 1.15 ± 0.6 85 ± 28 2 R1680W 1.22 ± 0.2 87 ± 17 3 635X 1.24 ± 0.5 90 ± 32 7 W590S 1.32 ± 0.6 103 ± 46 15 the mutant protein actually interferes with the activity of the remaining wild-type protein.
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ABCA1 p.Cys1477Arg 16704350:555:973
status: NEW[hide] Accurate prediction of the functional significance... PLoS Genet. 2005 Dec;1(6):e83. Epub 2005 Dec 30. Brunham LR, Singaraja RR, Pape TD, Kejariwal A, Thomas PD, Hayden MR
Accurate prediction of the functional significance of single nucleotide polymorphisms and mutations in the ABCA1 gene.
PLoS Genet. 2005 Dec;1(6):e83. Epub 2005 Dec 30., [PMID:16429166]
Abstract [show]
The human genome contains an estimated 100,000 to 300,000 DNA variants that alter an amino acid in an encoded protein. However, our ability to predict which of these variants are functionally significant is limited. We used a bioinformatics approach to define the functional significance of genetic variation in the ABCA1 gene, a cholesterol transporter crucial for the metabolism of high density lipoprotein cholesterol. To predict the functional consequence of each coding single nucleotide polymorphism and mutation in this gene, we calculated a substitution position-specific evolutionary conservation score for each variant, which considers site-specific variation among evolutionarily related proteins. To test the bioinformatics predictions experimentally, we evaluated the biochemical consequence of these sequence variants by examining the ability of cell lines stably transfected with the ABCA1 alleles to elicit cholesterol efflux. Our bioinformatics approach correctly predicted the functional impact of greater than 94% of the naturally occurring variants we assessed. The bioinformatics predictions were significantly correlated with the degree of functional impairment of ABCA1 mutations (r2 = 0.62, p = 0.0008). These results have allowed us to define the impact of genetic variation on ABCA1 function and to suggest that the in silico evolutionary approach we used may be a useful tool in general for predicting the effects of DNA variation on gene function. In addition, our data suggest that considering patterns of positive selection, along with patterns of negative selection such as evolutionary conservation, may improve our ability to predict the functional effects of amino acid variation.
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48 This SNP has been reported to be associated with decreased HDL cholesterol and increased severity of atherosclerosis in Table 1. subPSEC Scores and Probability of Functional Impairment (Pdeleterious) for ABCA1 Mutations and SNPs Mutations SNPs Variant SubPSEC Pdeleterious Variant subPSEC Pdeleterious P85L À4.62 0.83 R219K À0.57 0.08 H160F À2.79 0.45 V399A À2.26 0.32 R230C À4.27 0.78 V771M À2.86 0.46 A255T À1.81 0.23 T774P À1.99 0.27 E284K À2.34 0.34 K776N À3.53 0.63 Y482C À4.21 0.77 V825I À1.06 0.13 R587W À6.04 0.95 I883M À1.38 0.17 W590S À5.19 0.9 E1172D À1.96 0.26 W590L À4.48 0.82 R1587K À0.58 0.08 Q597R À7.15 0.98 S1731C À4.21 0.77 T929I À4.29 0.78 N935H À8.54 1 N935S À7.53 0.99 A937V À6.6 0.97 A1046D À7.52 0.99 M1091T À3.56 0.64 D1099Y À6.09 0.96 D1289N À2.48 0.37 L1379F À3.81 0.69 C1477R À5.44 0.92 S1506L À5.17 0.9 N1611D À5.69 0.94 R1680W À6.02 0.95 V1704D À3.21 0.55 N1800H À4.23 0.77 R1901S À5.06 0.89 F2009S À2.73 0.43 R2081W À8.08 0.99 P2150L À2.88 0.47 Q2196H À2.74 0.43 DOI: 10.1371/journal.pgen.0010083.t001 PLoS Genetics | www.plosgenetics.org December 2005 | Volume 1 | Issue 6 | e83 0740 Accurate Prediction of ABCA1 Variants Synopsis A major goal of human genetics research is to understand how genetic variation leads to differences in the function of genes.
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ABCA1 p.Cys1477Arg 16429166:48:797
status: NEWX
ABCA1 p.Cys1477Arg 16429166:48:942
status: NEW75 Cholesterol Efflux Values for 293 Cells Transfected with ABCA1 Variants and subPSEC and PolyPhen Predictions of the Functional Impact of these Variants Variant Variant Type subPSEC Cholesterol Efflux PolyPhen R2081W Mutation À8.08 21.1 6 21%* Probably damaging N935S Mutation À7.53 29.3 6 13%* Benign A1046D Mutation À7.52 16.8 6 7%* Possibly damaging Q597R Mutation À7.15 17.7 6 14%* Probably damaging R587W Mutation À6.04 31.7 6 33%* Probably damaging C1477R Mutation À5.44 20.5 6 10%* Probably damaging W590S Mutation À5.19 47.1 6 13%* Probably damaging S1506L Mutation À5.17 17.8 6 15%* Probably damaging T929I Mutation À4.29 69.9 6 11%* Possibly damaging N1800H Mutation À4.23 31.3 6 16%* Possibly damaging S1731C SNP À4.21 12.3 6 10%* Possibly damaging M1091T Mutation À3.56 6.9 6 20%* Probably damaging P2150L Mutation À2.88 88.4 6 21% Probably damaging V771M SNP À2.86 145.4 6 33% Benign D1289N Mutation À2.48 137.7 6 86% Benign I883M SNP À1.38 69.1 6 16%* Benign R219K SNP À0.57 103.7 6 21.05 Benign Wild-type - 0.0 100% - *p , 0.01 compared to wild-type ABCA1.
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ABCA1 p.Cys1477Arg 16429166:75:454
status: NEWX
ABCA1 p.Cys1477Arg 16429166:75:479
status: NEW[hide] Biogenesis and speciation of nascent apoA-I-contai... J Lipid Res. 2005 Aug;46(8):1668-77. Epub 2005 May 16. Krimbou L, Hajj Hassan H, Blain S, Rashid S, Denis M, Marcil M, Genest J
Biogenesis and speciation of nascent apoA-I-containing particles in various cell lines.
J Lipid Res. 2005 Aug;46(8):1668-77. Epub 2005 May 16., [PMID:15897603]
Abstract [show]
It is generally thought that the large heterogeneity of human HDL confers antiatherogenic properties; however, the mechanisms governing HDL biogenesis and speciation are complex and poorly understood. Here, we show that incubation of exogenous apolipoprotein A-I (apoA-I) with fibroblasts, CaCo-2, or CHO-overexpressing ABCA1 cells generates only alpha-nascent apolipoprotein A-I-containing particles (alpha-LpA-I) with diameters of 8-20 nm, whereas human umbilical vein endothelial cells and ABCA1 mutant (Q597R) cells were unable to form such particles. Interestingly, incubation of exogenous apoA-I with either HepG2 or macrophages generates both alpha-LpA-I and prebeta1-LpA-I. Furthermore, glyburide inhibits almost completely the formation of alpha-LpA-I but not prebeta1-LpA-I. Similarly, endogenously secreted HepG2 apoA-I was found to be associated with both prebeta1-LpA-I and alpha-LpA-I; by contrast, CaCo-2 cells secreted only alpha-LpA-I. To determine whether alpha-LpA-I generated by fibroblasts is a good substrate for LCAT, isolated alpha-LpA-I as well as reconstituted HDL [r(HDL)] was reacted with LCAT. Although both particles had similar V(max) (8.4 vs. 8.2 nmol cholesteryl ester/h/microg LCAT, respectively), the K(m) value was increased 2-fold for alpha-LpA-I compared with r(HDL) (1.2 vs. 0.7 microM apoA-I). These results demonstrate that 1) ABCA1 is required for the formation of alpha-LpA-I but not prebeta1-LpA-I; and 2) alpha-LpA-I interacts efficiently with LCAT. Thus, our study provides direct evidence for a new link between specific cell lines and the speciation of nascent HDL that occurs by both ABCA1-dependent and -independent pathways.
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26 MATERIALS AND METHODS Patient selection For the present study, we selected fibroblasts from three normal control subjects and two patients with TD (TD1, homozygous for Q597R at the ABCA1 gene; and TD2, compound heterozygous carrying the mutations C1477R and the splice site G→C in exon 24), as described previously (13, 14).
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ABCA1 p.Cys1477Arg 15897603:26:247
status: NEW78 As shown in Fig. 1 (upper panels), incubation of stimulated normal fibroblasts, CaCo-2 cells, or CHO-overexpressing ABCA1 (CHO-ABCA1) with 10 g/ml exogenously added 125I-apoA-I for 6 h at 37ЊC followed by the removal of lipid-free apoA-I as described above, and then separation of samples by 2D-PAGGE, generated only ␣-LpA-I with a particle size ranging from 8 to 20 nm, whereas lipid-free apoA-I incubated with either HUVEC or ABCA1 mutant (Q597R) was unable to form such particles.
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ABCA1 p.Cys1477Arg 15897603:78:52
status: NEW79 In separate experiments, we found that ABCA1 mutant C1477R also failed to form ␣-LpA-I (data not shown).
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ABCA1 p.Cys1477Arg 15897603:79:52
status: NEW[hide] Cellular physiology of cholesterol efflux in vascu... Circulation. 2004 Nov 2;110(18):2881-8. Epub 2004 Oct 18. O'Connell BJ, Denis M, Genest J
Cellular physiology of cholesterol efflux in vascular endothelial cells.
Circulation. 2004 Nov 2;110(18):2881-8. Epub 2004 Oct 18., [PMID:15492319]
Abstract [show]
BACKGROUND: Of the cells that compose the atherosclerotic plaque, vascular endothelial cells are the most resistant to cholesterol accumulation. Cholesterol efflux pathways may play an important role in endothelial cholesterol homeostasis. METHODS AND RESULTS: We examined the global genetic response of endothelial cells to cholesterol and in particular the contribution of the cholesterol efflux proteins ATP-binding cassette transporter A1 (ABCA1), ATP-binding cassette transporter G1 (ABCG1), and scavenger receptor B-I (SR-BI) to endothelial cell cholesterol efflux. The ABCG1 gene is induced in endothelial cells by cholesterol, whereas ABCA1 is not. Using specific chemical inhibitors of ABC transporters and SR-BI, we have shown that neither ABC transporters nor SR-BI is required for apolipoprotein A-1-mediated endothelial cholesterol efflux. CONCLUSIONS: Endothelial cells may use nontraditional pathways for cholesterol efflux.
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No. Sentence Comment
27 Normal human skin fibroblasts were obtained by biopsy from a healthy human volunteer, and Tangier fibroblasts were from a patient with compound ABCA1 mutations (ABCA1 C1477R amino acid substitution and an ABCA1 IVS25ϩ1 [G3C] mRNA splice site mutation).
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ABCA1 p.Cys1477Arg 15492319:27:167
status: NEW22 Normal human skin fibroblasts were obtained by biopsy from a healthy human volunteer, and Tangier fibroblasts were from a patient with compound ABCA1 mutations (ABCA1 C1477R amino acid substitution and an ABCA1 IVS25af9;1 [G3C] mRNA splice site mutation).
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ABCA1 p.Cys1477Arg 15492319:22:167
status: NEW[hide] Characterization of oligomeric human ATP binding c... J Biol Chem. 2004 Oct 1;279(40):41529-36. Epub 2004 Jul 26. Denis M, Haidar B, Marcil M, Bouvier M, Krimbou L, Genest J
Characterization of oligomeric human ATP binding cassette transporter A1. Potential implications for determining the structure of nascent high density lipoprotein particles.
J Biol Chem. 2004 Oct 1;279(40):41529-36. Epub 2004 Jul 26., [PMID:15280376]
Abstract [show]
The oligomeric structure of ABCA1 transporter and its function related to the biogenesis of nascent apoA-I-containing particles (LpA-I) were investigated. Using n-dodecylmaltoside and perfluoro-octanoic acid combined with non-denaturing gel, the majority of ABCA1 was found as a tetramer in ABCA1-induced human fibroblasts. Furthermore, using chemical cross-linking and SDS-PAGE, ABCA1 dimers but not the tetramers were found covalently linked. Oligomeric ABCA1 was present in isolated plasma membranes as well as in intracellular compartments. Interestingly, apoA-I was found to be associated with both dimeric and tetrameric, but not monomeric, forms of ABCA1. Neither apoA-I nor lipid molecules did affect ABCA1 oligomerization. Immunoprecipitation analysis showed that oligomeric ABCA1 did not contain other associated proteins. We next investigated the relationship between the oligomeric ABCA1 complex and the structure of LpA-I. Lipid-free apoA-I incubated with normal cells generated LpA-I with diameters between 9.5 and 20 nm. Subsequent isolation of LpA-I followed by cross-linking revealed the presence of four and eight apoA-I molecules per particle, whereas apoA-I incubated with ABCA1 mutant (Q597R) cells was unable to form such particles and remained in the monomeric form. These results demonstrate that: 1) ABCA1 exists as an oligomeric complex; and 2) ABCA1 oligomerization was independent of apoA-I binding and lipid molecules. The findings that the majority of ABCA1 exists as a tetramer that binds apoA-I, together with the observation that LpA-I contains at least four molecules of apoA-I per particle, support the concept that the homotetrameric ABCA1 complex constitutes the minimum functional unit required for the biogenesis of high density lipoprotein particles.
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182 Interestingly, we found that pre-beta- LpE3 contains four and eight molecules of apoE3 per particle, whereas lipid-free apoE3 incubated with ABCA1 mutant (C1477R) remained in the monomeric form (data not shown).
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ABCA1 p.Cys1477Arg 15280376:182:155
status: NEW199 Although ABCA1 mutants Q597R and C1477R were found to oligomerize normally (data not shown) and localized to the plasma membrane, they showed the total absence of binding to apoA-I (21, 23).
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ABCA1 p.Cys1477Arg 15280376:199:33
status: NEW200 These results indicate that the apoA-I lipidation defect observed in either Q597R or C1477R ABCA1 mutants is not caused by impaired oligomerization of ABCA1.
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ABCA1 p.Cys1477Arg 15280376:200:85
status: NEW201 Furthermore, C1477R, a naturally occurring mutant of ABCA1 in which cysteine 1477 within the second large extracellular loop is replaced with arginine (10), was found to dimerize normally.
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ABCA1 p.Cys1477Arg 15280376:201:13
status: NEW177 Interestingly, we found that pre-beta- LpE3 contains four and eight molecules of apoE3 per particle, whereas lipid-free apoE3 incubated with ABCA1 mutant (C1477R) remained in the monomeric form (data not shown).
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ABCA1 p.Cys1477Arg 15280376:177:155
status: NEW194 Although ABCA1 mutants Q597R and C1477R were found to oligomerize normally (data not shown) and localized to the plasma membrane, they showed the total absence of binding to apoA-I (21, 23).
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ABCA1 p.Cys1477Arg 15280376:194:33
status: NEW195 These results indicate that the apoA-I lipidation defect observed in either Q597R or C1477R ABCA1 mutants is not caused by impaired oligomerization of ABCA1.
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ABCA1 p.Cys1477Arg 15280376:195:85
status: NEW196 Furthermore, C1477R, a naturally occurring mutant of ABCA1 in which cysteine 1477 within the second large extracellular loop is replaced with arginine (10), was found to dimerize normally.
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ABCA1 p.Cys1477Arg 15280376:196:13
status: NEW[hide] The ATP-binding cassette transporter 1 mediates li... J Lipid Res. 2004 Jun;45(6):1040-50. Epub 2004 Mar 16. Selva DM, Hirsch-Reinshagen V, Burgess B, Zhou S, Chan J, McIsaac S, Hayden MR, Hammond GL, Vogl AW, Wellington CL
The ATP-binding cassette transporter 1 mediates lipid efflux from Sertoli cells and influences male fertility.
J Lipid Res. 2004 Jun;45(6):1040-50. Epub 2004 Mar 16., [PMID:15026428]
Abstract [show]
The liver X receptor/retinoid X receptor (LXR/RXR)-regulated gene ABCA1 effluxes cellular cholesterol and phospholipid to apolipoprotein A1 (apoA1), which is the rate-limiting step in high-density lipoprotein synthesis. The RXR pathway plays a critical role in testicular lipid trafficking, and RXRbeta-deficient male mice are sterile and accumulate lipids in Sertoli cells. Here, we demonstrate that ABCA1 mRNA and protein are abundant in Sertoli cells, whereas germ cells express little ABCA1. LXR/RXR agonists stimulate ABCA1 expression in cultured Sertoli MSC1 and Leydig TM3 cell lines. However, Sertoli TM4 cells lack ABCA1, and TM4 cells or primary Sertoli cells cultured from ABCA1(-/-) mice both fail to efflux cholesterol to apoA1. Expression of exogenous ABCA1 restores apoA1-dependent cholesterol efflux in Sertoli TM4 cells. In vivo, ABCA1-deficient mice exhibit lipid accumulation in Sertoli cells and depletion of normal lipid droplets from Leydig cells by 2 months of age. By 6 months of age, intratesticular testosterone levels and sperm counts are significantly reduced in ABCA1(-/-) mice compared with wild-type (WT) controls. Finally, a 21% decrease (P = 0.01) in fertility was observed between ABCA1(-/-) males compared with WT controls across their reproductive lifespans. These results show that ABCA1 plays an important role in lipid transport in Sertoli cells and influences male fertility.
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231 Children of TD fathers TD Patient Mutation Father`s Age Number of Children Youngest Child`s Age Father-Child Age Difference Reference years years years TD1 (III:01) C1477R, splice 43 1 6 36 (17) TD1 (II:5) G1764del-635X 63 2 21 42 (16) TD2 (II:4) 3Ј del-1834X 52 2 Ͻ14 Ͼ38 (16) TD3 (II.4) N935S 66 3 28 38 (16) TD5 (III:4) A877V, W530S 52 1 31 21 (59) II-2 1,284X 62 4 21 41 (60) P R1680W 48 3 5 43 (61) TD, Tangier disease.
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ABCA1 p.Cys1477Arg 15026428:231:165
status: NEW232 Children of TD fathers TD Patient Mutation Father`s Age Number of Children Youngest Child`s Age Father-Child Age Difference Reference years years years TD1 (III:01) C1477R, splice 43 1 6 36 (17) TD1 (II:5) G1764del-635X 63 2 21 42 (16) TD2 (II:4) 3 del-1834X 52 2 14 38 (16) TD3 (II.4) N935S 66 3 28 38 (16) TD5 (III:4) A877V, W530S 52 1 31 21 (59) II-2 1,284X 62 4 21 41 (60) P R1680W 48 3 5 43 (61) TD, Tangier disease.
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ABCA1 p.Cys1477Arg 15026428:232:165
status: NEW[hide] Two novel missense mutations in ABCA1 result in al... Biochim Biophys Acta. 2004 May 24;1689(1):47-57. Albrecht C, Baynes K, Sardini A, Schepelmann S, Eden ER, Davies SW, Higgins CF, Feher MD, Owen JS, Soutar AK
Two novel missense mutations in ABCA1 result in altered trafficking and cause severe autosomal recessive HDL deficiency.
Biochim Biophys Acta. 2004 May 24;1689(1):47-57., [PMID:15158913]
Abstract [show]
Extremely low concentrations of high density lipoprotein (HDL)-cholesterol and apolipoprotein (apo) AI are features of Tangier disease caused by autosomal recessive mutations in ATP-binding cassette transporter A1 (ABCA1). Less deleterious, but dominantly inherited mutations cause HDL deficiency. We investigated causes of severe HDL deficiency in a 42-year-old female with progressive coronary disease. ApoAI-mediated efflux of cholesterol from the proband's fibroblasts was less than 10% of normal and nucleotide sequencing revealed inheritance of two novel mutations in ABCAI, V1704D and L1379F. ABCA1 mRNA was approximately 3-fold higher in the proband's cells than in control cells; preincubation with cholesterol increased it 5-fold in control and 8-fold in the proband's cells, but similar amounts of ABCA1 protein were present in control and mutant cells. When transiently transfected into HEK293 cells, confocal microscopy revealed that both mutant proteins were retained in the endoplasmic reticulum, while wild-type ABCA1 was located at the plasma membrane. Severe HDL deficiency in the proband was caused by two novel autosomal recessive mutations in ABCA1, one (V1704D) predicted to lie in a transmembrane segment and the other (L1379F) in a large extracellular loop. Both mutations prevent normal trafficking of ABCA1, thereby explaining their inability to mediate apoA1-dependent lipid efflux.
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215 Two of these, C1477R and S1506L, do not appear to disrupt transport of the protein to the cell surface, as judged by the accessibility of the protein in non-permeabilised cells, but the mutant proteins are unable to mediate cholesterol efflux [38].
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ABCA1 p.Cys1477Arg 15158913:215:14
status: NEW214 Two of these, C1477R and S1506L, do not appear to disrupt transport of the protein to the cell surface, as judged by the accessibility of the protein in non-permeabilised cells, but the mutant proteins are unable to mediate cholesterol efflux [38].
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ABCA1 p.Cys1477Arg 15158913:214:14
status: NEW[hide] Molecular interactions between apoE and ABCA1: imp... J Lipid Res. 2004 May;45(5):839-48. Epub 2004 Feb 1. Krimbou L, Denis M, Haidar B, Carrier M, Marcil M, Genest J Jr
Molecular interactions between apoE and ABCA1: impact on apoE lipidation.
J Lipid Res. 2004 May;45(5):839-48. Epub 2004 Feb 1., [PMID:14754908]
Abstract [show]
Apolipoprotein E (apoE)/ABCA1 interactions were investigated in human intact fibroblasts induced with 22(R)-hydroxycholesterol and 9-cis-retinoic acid (stimulated cells). Here, we show that purified human plasma apoE3 forms a complex with ABCA1 in normal fibroblasts. Lipid-free apoE3 inhibited the binding of (125)I-apoA-I to ABCA1 more efficiently than reconstituted HDL particles (IC(50) = 2.5 +/- 0.4 microg/ml vs. 12.3 +/- 1.3 microg/ml). ApoE isoforms showed similar binding for ABCA1 and exhibited identical kinetics in their abilities to induce ABCA1-dependent cholesterol efflux. Mutation of ABCA1 associated with Tangier disease (C1477R) abolished both apoE3 binding and apoE3-mediated cholesterol efflux. Analysis of apoE3-containing particles generated during the incubation of lipid-free apoE3 with stimulated normal cells showed nascent apoE3/cholesterol/phospholipid complexes that exhibited prebeta-electrophoretic mobility with a particle size ranging from 9 to 15 nm, whereas lipid-free apoE3 incubated with ABCA1 mutant (C1477R) cells was unable to form such particles. These results demonstrate that 1). apoE association with lipids reduced its ability to interact with ABCA1; 2). apoE isoforms did not affect apoE binding to ABCA1; 3). apoE-mediated ABCA1-dependent cholesterol efflux was not affected by apoE isoforms in fibroblasts; and 4). the lipid translocase activity of ABCA1 generates apoE-containing high density-sized lipoprotein particles. Thus, ABCA1 is essential for the biogenesis of high density-sized lipoprotein containing only apoE particles in vivo.
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No. Sentence Comment
5 Mutation of ABCA1 associated with Tangier disease (C1477R) abolished both apoE3 binding and apoE3-mediated cholesterol efflux.
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ABCA1 p.Cys1477Arg 14754908:5:51
status: NEW6 Analysis of apoE3-containing particles generated during the incubation of lipid-free apoE3 with stimulated normal cells showed nascent apoE3/ cholesterol/phospholipid complexes that exhibited prebeta- electrophoretic mobility with a particle size ranging from 9 to 15 nm, whereas lipid-free apoE3 incubated with ABCA1 mutant (C1477R) cells was unable to form such particles.
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ABCA1 p.Cys1477Arg 14754908:6:323
status: NEW31 MATERIALS AND METHODS Patient selection For the present study, we selected fibroblasts from three normal control subjects and one patient with TD (compound heterozygous carrying the mutations C1477R and the splice site G→C in exon 24) as previously described (16, 20).
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ABCA1 p.Cys1477Arg 14754908:31:192
status: NEW126 To determine whether naturally occurring mutants of ABCA1 might affect apoE3 binding, cross-linking of apoE3 to mutant ABCA1 (C1477R) was examined.
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ABCA1 p.Cys1477Arg 14754908:126:126
status: NEW127 As shown in Fig. 4, C1477R mutant abolished both apoE3 cross-linking and apoE3-mediated cholesterol efflux.
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ABCA1 p.Cys1477Arg 14754908:127:20
status: NEW128 On the other hand, C1477R mutant was found to be present at the plasma membrane, as determined by cell surface biotinylation (data not shown).
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ABCA1 p.Cys1477Arg 14754908:128:19
status: NEW129 To investigate the nature of apoE3-containing particles generated by ABCA1, stimulated cells from either normal control or TD (C1477R) subjects in 100 mm diameter dishes were incubated with 5 g/ml lipid-free apoE3 in DMEM for 24 h at 37ЊC.
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ABCA1 p.Cys1477Arg 14754908:129:127
status: NEW175 A: Fibroblasts from a normal control and a Tangier disease (TD) (C1477R) subject were stimulated and incubated with 3 g/ml apoE3.
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ABCA1 p.Cys1477Arg 14754908:175:65
status: NEWX
ABCA1 p.Cys1477Arg 14754908:175:186
status: NEW176 Cross-linking, immunoprecipitation, and detection of apoE3 associated with ABCA1 were performed as described in Materials and Methods. B: Fibroblasts from a normal control and a mutant (C1477R) subject were labeled with [3H]cholesterol and cholesterol-loaded, then stimulated for 20 h. Cells were incubated with 10 g/ml apoE3 or apoA-I for 24 h, and cholesterol efflux was determined. Values represent means Ϯ SD from triplicate wells.
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ABCA1 p.Cys1477Arg 14754908:176:186
status: NEW185 In contrast, apoE3 incubated with TD cells (C1477R) was unable to form such particles (Fig. 5); because this is the plasma HDL-LpE3 size range having prebeta electrophoretic mobility (13), these particles are designated prebeta-LpE3-like particles.
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ABCA1 p.Cys1477Arg 14754908:185:44
status: NEW188 These results are consistent with our Fig. 5. Characterization of lipidated apoE3-containing particles generated during apoE3 incubation with stimulated fibroblasts from a normal and a TD (C1477R) subject.
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ABCA1 p.Cys1477Arg 14754908:188:189
status: NEW198 observations that ABCA1 mutation in the second large extracellular loop (C1477R) abolished both apoE3 binding and apoE3-mediated cholesterol efflux (Fig. 4).
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ABCA1 p.Cys1477Arg 14754908:198:73
status: NEW174 A: Fibroblasts from a normal control and a Tangier disease (TD) (C1477R) subject were stimulated and incubated with 3 g/ml apoE3.
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ABCA1 p.Cys1477Arg 14754908:174:65
status: NEW184 In contrast, apoE3 incubated with TD cells (C1477R) was unable to form such particles (Fig. 5); because this is the plasma HDL-LpE3 size range having pre electrophoretic mobility (13), these particles are designated pre-LpE3-like particles.
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ABCA1 p.Cys1477Arg 14754908:184:44
status: NEW187 These results are consistent with our Fig. 5. Characterization of lipidated apoE3-containing particles generated during apoE3 incubation with stimulated fibroblasts from a normal and a TD (C1477R) subject.
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ABCA1 p.Cys1477Arg 14754908:187:189
status: NEW195 observations that ABCA1 mutation in the second large extracellular loop (C1477R) abolished both apoE3 binding and apoE3-mediated cholesterol efflux (Fig. 4).
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ABCA1 p.Cys1477Arg 14754908:195:73
status: NEW[hide] Apolipoprotein A-I activates cellular cAMP signali... J Biol Chem. 2004 Mar 12;279(11):9963-9. Epub 2003 Dec 29. Haidar B, Denis M, Marcil M, Krimbou L, Genest J Jr
Apolipoprotein A-I activates cellular cAMP signaling through the ABCA1 transporter.
J Biol Chem. 2004 Mar 12;279(11):9963-9. Epub 2003 Dec 29., [PMID:14701824]
Abstract [show]
It has been suggested that the signal transduction pathway initiated by apoA-I activates key proteins involved in cellular lipid efflux. We investigated apoA-I-mediated cAMP signaling in cultured human fibroblasts induced with (22R)-hydroxycholesterol and 9-cis-retinoic acid (stimulated cells). Treatment of stimulated fibroblasts with apoA-I for short periods of time (<or=45 min) increased ATP binding cassette A1 (ABCA1) phosphorylation in a concentration-dependent manner. Concomitantly, apoA-I increased the intracellular level of cAMP in a concentration- and time-dependent manner. The maximal cAMP level was reached within 10 min at 10 microg/ml apoA-I representing a 1-fold increase. The ability of apoA-I to mediate cAMP production was only observed in stimulated fibroblasts. Furthermore, overexpression of ABCA1 in Chinese hamster ovary cells resulted in a 1.5-fold increase in apoA-I-mediated cAMP accumulation as compared with untransfected cells. In contrast, forskolin increased cAMP production significantly in unstimulated fibroblasts as well as in untransfected Chinese hamster ovary cells. Pharmacological inhibition of protein kinase A (H89) completely blocked apoA-I-mediated ABCA1 phosphorylation. Naturally occurring mutations of ABCA1 associated with Tangier disease (C1477R, 2203X, and 2145X) severely reduced apoA-I-mediated cAMP production, ABCA1 phosphorylation, (125)I-apoA-I binding, and lipid efflux, without affecting forskolin-mediated cAMP elevation. In contrast, the protein kinase A catalytic subunit was able to phosphorylate ABCA1 similarly from mutant and normal cell lines in vitro. Together, our results indicate that apoA-I activates ABCA1 phosphorylation through the cAMP/protein kinase A-dependent pathway, apoA-I-mediated cAMP production required high level expression of functional ABCA1, and Tangier disease mutants have defective apoA-I-mediated cAMP signaling. These findings suggest that apoA-I may activate cAMP signaling through G protein-coupled ABCA1 transporter.
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No. Sentence Comment
9 Naturally occurring mutations of ABCA1 associated with Tangier disease (C1477R, 2203X, and 2145X) severely reduced apoA-I-mediated cAMP production, ABCA1 phosphorylation, 125 I-apoA-I binding, and lipid efflux, without affecting forskolin-mediated cAMP elevation.
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ABCA1 p.Cys1477Arg 14701824:9:72
status: NEW154 The C1477R (TD-1) mutant showed decreased presence at the plasma membrane, relative to the normal transporter (50% or greater reduction); however, the 2154X (TD-3) mutant failed to reach the membrane.
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ABCA1 p.Cys1477Arg 14701824:154:4
status: NEW200 On the other hand, we have documented previously (8) that 8-Br-cAMP and FRK did not induce ABCA1 phosphorylation in intact fibroblasts from TD-1 (C1477R) as compared with normal cells.
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ABCA1 p.Cys1477Arg 14701824:200:146
status: NEW208 A, fibroblasts from a normal control (CTR) and TD subjects (TD-1 (C1477R), TD-2 (2203X), and TD-3 (2145X)) (Table I) were stimulated, and ABCA1 was immunoprecipitated and incubated with [␥-32 P]ATP in the absence or presence of the PKA catalytic subunit (PKA-c) as described under "Experimental Procedures."
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ABCA1 p.Cys1477Arg 14701824:208:66
status: NEW153 The C1477R (TD-1) mutant showed decreased presence at the plasma membrane, relative to the normal transporter (50% or greater reduction); however, the 2154X (TD-3) mutant failed to reach the membrane.
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ABCA1 p.Cys1477Arg 14701824:153:4
status: NEW198 On the other hand, we have documented previously (8) that 8-Br-cAMP and FRK did not induce ABCA1 phosphorylation in intact fibroblasts from TD-1 (C1477R) as compared with normal cells.
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ABCA1 p.Cys1477Arg 14701824:198:146
status: NEW206 A, fibroblasts from a normal control (CTR) and TD subjects (TD-1 (C1477R), TD-2 (2203X), and TD-3 (2145X)) (Table I) were stimulated, and ABCA1 was immunoprecipitated and incubated with [ॹ-32 P]ATP in the absence or presence of the PKA catalytic subunit (PKA-c) as described under "Experimental Procedures."
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ABCA1 p.Cys1477Arg 14701824:206:66
status: NEW[hide] HDL deficiency and atherosclerosis: lessons from T... J Intern Med. 2004 Feb;255(2):299-301. Hovingh GK, Kuivenhoven JA, Bisoendial RJ, Groen AK, van Dam M, van Tol A, Wellington C, Hayden MR, Smelt AH, Kastelein JJ
HDL deficiency and atherosclerosis: lessons from Tangier disease.
J Intern Med. 2004 Feb;255(2):299-301., [PMID:14746569]
Abstract [show]
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No. Sentence Comment
23 This patient proved to be compound heterozygous for two ABCA1 gene mutations: a splicing defect (ivs 25+IG->C) and a missense mutation (C1477R).
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ABCA1 p.Cys1477Arg 14746569:23:136
status: NEW42 Our data suggest that Table 1 Overview of cases 1 and 2 Case 1 Case 2 Gender Male Male Age 38 52 BMI (kg m)2 ) 26 27 Lipids, lipoproteins and modifying enzymes Total cholesterol (mmol L)1 ) 2.3 4.1 LDL-C (mmol L)1 ) 1.3 2.7 HDL-C (mmol L)1 ) <0.1 <0.1 Triglycerides (mmol L)1 ) 2.0 2.3 ApoAI (g L)1 ) 0.01 0.08 ApoAII (g L)1 ) 0.05 0.16 ApoB (g L)1 ) 0.51 1.26 CETP mass (mg L)1 ) 1.65 2.79 Diagnosis ABCA1 functiona Reduced 90% Reduced 70% ABCA1 gene mutations Compound heterozygous Ivs 25 ¼ IG->C; C1477R Compound heterozygous GG5277,8C; T929I Clinical Clinical manifestation of CAD Premature MI and peripheral vascular disease NO IMT mean femoral and carotid artery 1.21 mm 0.89 mm a Fibroblast cholesterol efflux to apoA-I, compared with control, measured in triplicate.
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ABCA1 p.Cys1477Arg 14746569:42:505
status: NEW[hide] Heterozygosity for ABCA1 gene mutations: effects o... Atherosclerosis. 2003 Dec;171(2):311-9. Kuivenhoven JA, Hovingh GK, van Tol A, Jauhiainen M, Ehnholm C, Fruchart JC, Brinton EA, Otvos JD, Smelt AH, Brownlee A, Zwinderman AH, Hayden MR, Kastelein JJ
Heterozygosity for ABCA1 gene mutations: effects on enzymes, apolipoproteins and lipoprotein particle size.
Atherosclerosis. 2003 Dec;171(2):311-9., [PMID:14644402]
Abstract [show]
A cohort of 13 female and 14 male heterozygotes for ATP binding cassette A1 (ABCA1) gene defects was directly compared with 13 and 14 unaffected female and male family members of almost exact same age. The activities of three proteins that play key roles in HDL metabolism were measured in addition to extensive lipid and (apo) lipoprotein subfraction analysis. Compared to controls, LCAT activity was reduced by 15% in affected subjects (P < 0.001) while PLTP activity was unaffected. Interestingly, CETP activity was elevated by 50% in the heterozygote siblings of one kindred but was unaffected in heterozygotes of the three other families. With respect to lipids, the heterozygotes had normal total cholesterol (TC), and LDL-cholesterol concentrations but presented with a trend towards increased triglyceride levels (13%; P = 0.08). HDL metabolism, by contrast, was severely affected as illustrated by 40% reductions in HDL-cholesterol (P < 0.001) with concomitant reductions in apoAI (25%; P < 0.001) levels and in lipoprotein subfraction LpAI (28%; P < 0.001), LpAI:AII (24%; P=0.014), and LpCIII:nonB (34%; P < 0.001) concentrations. We furthermore observed reduced average HDL particle size (5%; P = 0.004; 16% in female and 3.6% in male) and reduced plasma apoCIII concentration (15%; P = 0.006) while apoAII, apoAIV, apoE and apoB levels were unchanged. In conclusion, heterozygosity for ABCA1 defects was associated with reduced LCAT activity in absence of effects on PLTP activity. Of special interest was our finding that the effects of compromised ABCA1 function on HDL were more pronounced in women than in men.
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45 The proband of family 1 suffered from TD and was found to be compound heterozygote for two ABCA1 gene defects: A missense mutation (T→C at position 4824) resulting in C1477R, and a non-sense defect (IVS25 + 1G to C) that caused differential splicing.
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ABCA1 p.Cys1477Arg 14644402:45:173
status: NEW[hide] Efflux and atherosclerosis: the clinical and bioch... Arterioscler Thromb Vasc Biol. 2003 Aug 1;23(8):1322-32. Epub 2003 May 22. Singaraja RR, Brunham LR, Visscher H, Kastelein JJ, Hayden MR
Efflux and atherosclerosis: the clinical and biochemical impact of variations in the ABCA1 gene.
Arterioscler Thromb Vasc Biol. 2003 Aug 1;23(8):1322-32. Epub 2003 May 22., [PMID:12763760]
Abstract [show]
Approximately 50 mutations and many single nucleotide polymorphisms have been described in the ABCA1 gene, with mutations leading to Tangier disease and familial hypoalphalipoproteinemia. Homozygotes and heterozygotes for mutations in ABCA1 display a wide range of phenotypes. Identification of ABCA1 as the molecular defect in these diseases has allowed for ascertainment based on genetic status and determination of genotype-phenotype correlations and has permitted us to identify mutations conferring a range of severity of cellular, biochemical, and clinical phenotypes. In this study we review how genetic variation at the ABCA1 locus affects its role in the maintenance of lipid homeostasis and the natural progression of atherosclerosis.
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No. Sentence Comment
80 However, failure of binding may also occur because of disruption of residues crucial for this function. Indeed, the variants C1477R and S1506L, which are both localized in the second large extracellular loop, are normally translocated to the plasma membrane but show no ApoA-I binding, indicating that specific amino acids in the large extracellular loops are Figure 4.
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ABCA1 p.Cys1477Arg 12763760:80:125
status: NEW83 TABLE 2. Conservation of Amino Acid Residues Mutated in Humans Mutation H. sapiens M. musculus G. gallus D. melanogaster C. elegans P85L P P P ⅐ ⅐ ⅐ P R230C R R R P G A255T A A S ⅐ ⅐ ⅐ ⅐ ⅐ ⅐ R587W R R R ⅐ ⅐ ⅐ ⅐ ⅐ ⅐ W590S W W W R Q Q597R Q Q Q Q Q ⌬L693 L L L L L T929I T T T T T N935S/H N N N N N A937V A A A A A A1046D A A A A A M1091T M M M M M D1099Y D D D D D D1289L/N D D D D D C1477R C C C ⅐ ⅐ ⅐ ⅐ ⅐ ⅐ S1506L S S S ⅐ ⅐ ⅐ ⅐ ⅐ ⅐ N1611D N N N N S R1680W R R R R R N1800H N N N A W F2009S F F F I M R2081W R R R R R P2150L P P P R N ⌬E1893 E E E D S ⌬D1894 D D D D D Twenty-three of 24 (95.83%) amino acids affected by mutations are conserved with G. gallus, reflecting the functional importance of these residues.
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ABCA1 p.Cys1477Arg 12763760:83:495
status: NEW136 Single Nucleotide Polymorphisms in the ABCA1 Gene Nucleotide Amino Acid Exon -1095A/G Promoter ⅐ ⅐ ⅐ -477C/T Promoter ⅐ ⅐ ⅐ -419A/C Promoter ⅐ ⅐ ⅐ -320G/C Promoter ⅐ ⅐ ⅐ -191G/C Promoter ⅐ ⅐ ⅐ C69T 5ЈUTR 1 C117G 5ЈUTR 1 InsG319 5ЈUTR 2 G378C 5ЈUTR 2 G1051A R219K 7 T1591C V399A 11 G2706A V771M 16 A2715C T774P 16 G2723C K776N 16 G2826A V825I 17 A3044G I883M 18 G3911C E1172D 24 G5255A R1587K 35 C5587G S1731C 38 markers, namely, increased arterial wall thickness and ABCA1-mediated cholesterol efflux, was performed.73 The study group consisted of 30 individuals heterozygous for 4 different missense mutations in the ABCA1 gene, C1477R, M1091T, P2150L, and T929I.
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ABCA1 p.Cys1477Arg 12763760:136:760
status: NEW72 However, failure of binding may also occur because of disruption of residues crucial for this function. Indeed, the variants C1477R and S1506L, which are both localized in the second large extracellular loop, are normally translocated to the plasma membrane but show no ApoA-I binding, indicating that specific amino acids in the large extracellular loops are Figure 4.
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ABCA1 p.Cys1477Arg 12763760:72:125
status: NEW75 TABLE 2. Conservation of Amino Acid Residues Mutated in Humans Mutation H. sapiens M. musculus G. gallus D. melanogaster C. elegans P85L P P P ዼ ዼ ዼ P R230C R R R P G A255T A A S ዼ ዼ ዼ ዼ ዼ ዼ R587W R R R ዼ ዼ ዼ ዼ ዼ ዼ W590S W W W R Q Q597R Q Q Q Q Q èc;L693 L L L L L T929I T T T T T N935S/H N N N N N A937V A A A A A A1046D A A A A A M1091T M M M M M D1099Y D D D D D D1289L/N D D D D D C1477R C C C ዼ ዼ ዼ ዼ ዼ ዼ S1506L S S S ዼ ዼ ዼ ዼ ዼ ዼ N1611D N N N N S R1680W R R R R R N1800H N N N A W F2009S F F F I M R2081W R R R R R P2150L P P P R N èc;E1893 E E E D S èc;D1894 D D D D D Twenty-three of 24 (95.83%) amino acids affected by mutations are conserved with G. gallus, reflecting the functional importance of these residues.
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ABCA1 p.Cys1477Arg 12763760:75:479
status: NEW128 Single Nucleotide Polymorphisms in the ABCA1 Gene Nucleotide Amino Acid Exon afa;1095A/G Promoter ዼ ዼ ዼ afa;477C/T Promoter ዼ ዼ ዼ afa;419A/C Promoter ዼ ዼ ዼ afa;320G/C Promoter ዼ ዼ ዼ afa;191G/C Promoter ዼ ዼ ዼ C69T 5b18;UTR 1 C117G 5b18;UTR 1 InsG319 5b18;UTR 2 G378C 5b18;UTR 2 G1051A R219K 7 T1591C V399A 11 G2706A V771M 16 A2715C T774P 16 G2723C K776N 16 G2826A V825I 17 A3044G I883M 18 G3911C E1172D 24 G5255A R1587K 35 C5587G S1731C 38 Singaraja et al Clinical and Biochemical Impact of ABCA1 Variants markers, namely, increased arterial wall thickness and ABCA1-mediated cholesterol efflux, was performed.73 The study group consisted of 30 individuals heterozygous for 4 different missense mutations in the ABCA1 gene, C1477R, M1091T, P2150L, and T929I.
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ABCA1 p.Cys1477Arg 12763760:128:842
status: NEW[hide] Genetics of HDL regulation in humans. Curr Opin Lipidol. 2003 Jun;14(3):273-9. Miller M, Rhyne J, Hamlette S, Birnbaum J, Rodriguez A
Genetics of HDL regulation in humans.
Curr Opin Lipidol. 2003 Jun;14(3):273-9., [PMID:12840658]
Abstract [show]
PURPOSE OF REVIEW: To review gene regulation of HDL-cholesterol and discuss molecular abnormalities in HDL candidate genes that may lead to human pathologic states. RECENT FINDINGS: The inverse association between HDL-cholesterol and vascular disease, especially coronary heart disease, has long been recognized, but understanding gene regulation of HDL in humans gained considerable momentum following the identification of ABCA1 as playing a pivotal role in reverse cholesterol transport. Recent data suggest that potentially important targets for upregulating HDL in humans include upregulators of ABCA1 and APOA1 (e.g. peroxisome proliferator activated receptor and liver X receptor agonists) and downregulators of CETP (e.g. JTT-705). A host of other nuclear receptors under investigation in animal models may advance to human testing in the near future. SUMMARY: Disorders affecting HDL metabolism are complex because monogenic disorders causing low HDL do not necessarily correlate with premature vascular disease. To date, pathologic phenotypes have only been deduced among several HDL candidate genes. Understanding the genetic underpinnings associated with variant HDL and reverse cholesterol transport provides an exceptional opportunity to identify novel agents that may optimize this process and reduce vascular event rates beyond currently available LDL lowering therapies.
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No. Sentence Comment
66 TD 1591 T/C 11 V399A extracellular [68] TD 1979 (110bpAlu Ins) 12 truncated truncation [60] TD/FHA 2154 C/T 14 R587W extracellular [67,69] TD 2164 G/C 14 W590S extracellular [61] TD 2185 A/G 14 Q597R extracellular [59,67] TD 2219 G/del 14 truncated, 635X truncated [60,61] FHA 2472-2474 3bp del 15 Del L693 TM domain #3 [59] phosphorylation 2706 G/A 16 V771M extracellular [68] 2715 A/C 16 T774P extracellular [68] 2723 G/C 16 K776N extracellular [68] 2868 G/A 17 V825I TM domain #6 [67,68] TD/FHA 3044 A/G 18 I883M cytoplasmic [68] phosphorylat site FHA 3120 C/T 19 R909X truncation [63,71] TD 3181 C/T 19 T929I cytoplasmic [62] TD 3199 A/G 19 N935S Walker A [61] TD 3205 C/T 19 A937V Walker A [61] TD 3532 C/A 22 A1046D cytoplasmic, Walker A/B [70] FHA 3667 T/C 23 M1091T cytoplasmic [63] 3690 G/T 23 D1099Y cytoplasmic [9] TD 3738 2bp del 23 1145X truncation [66] FHA 3911 G/C 24 E1172D linker/cytoplasmic [68] FHA 4242 4bp del 27 1297X truncated [64] TD 4260 G/A 27 D1289N linker cytoplasm [64,65] TD 4824 T/C 31 C1477R extracellular [59] TD 4912 C/T 32 S1506L extracellular loop #2 [71] TD 5025 ins A 34 A1544S?1552X truncation [70] 5059 T/C 34 I1555T extracellular loop #2 [67] 5155 G/A 35 R1587K extracellular loop #2 [68] FHA 5226 A/G 36 N1611D extracellular loop #2 [75..] 5338 T/C 36 L1648P extracellular loop #2 [67] TD 5443 C/T 37 R1680W cytoplasmic [74.]
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ABCA1 p.Cys1477Arg 12840658:66:1017
status: NEW[hide] The role of the ABCA1 transporter and cholesterol ... J Lipid Res. 2003 Jun;44(6):1251-5. Epub 2003 Apr 16. Hovingh GK, Van Wijland MJ, Brownlie A, Bisoendial RJ, Hayden MR, Kastelein JJ, Groen AK
The role of the ABCA1 transporter and cholesterol efflux in familial hypoalphalipoproteinemia.
J Lipid Res. 2003 Jun;44(6):1251-5. Epub 2003 Apr 16., [PMID:12700344]
Abstract [show]
Defects in the gene encoding for the ATP binding cassette (ABC) transporter A1 (ABCA1) were shown to be one of the genetic causes for familial hypoalphalipoproteinemia (FHA). We investigated the role of ABCA1-mediated cholesterol efflux in Dutch subjects suffering from FHA. Eighty-eight subjects (mean HDL cholesterol levels 0.63 +/- 0.21 mmol/l) were enrolled. Fibroblasts were cultured and loaded with [3H]cholesterol. ABCA1 and non-ABCA1-mediated efflux was studied by using apolipoprotein A-I (apoA-I), HDL, and methyl-beta-cyclodextrin as acceptors. Efflux to apoA-I was decreased in four patients (4/88, 4.5%), and in all cases, a mutation in the ABCA1 gene was found. In the remaining 84 subjects, no correlation between efflux and apoA-I or HDL cholesterol was found. Efflux to both HDL and cyclodextrin, in contrast, did correlate with HDL cholesterol plasma levels (r = 0.34, P = 0.01; and r = 0.27, P = 0.008, respectively). The prevalence of defects in ABCA1-dependent cholesterol efflux in Dutch FHA patients is low. The significant correlation between plasma HDL cholesterol levels and methyl-beta-cyclodextrin-mediated efflux in the FHA patients with normal ABCA1 function suggests that non-ABCA1-mediated efflux might also be important for plasma HDL cholesterol levels in these individuals.
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No. Sentence Comment
81 The two compound heterozygous patients have been described previously [one of the compound heterozygous carriers suffered from a missense mutation (T to C at position 4,369) resulting in a C1477R, and a defect (IVS24 ϩ 1G to C) that caused differential splicing, whereas the other was shown to carry a missense mutation (C to T at position 3,181 resulting in T929I) and a de novo nonsense mutation] (16).
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ABCA1 p.Cys1477Arg 12700344:81:189
status: NEW80 The two compound heterozygous patients have been described previously [one of the compound heterozygous carriers suffered from a missense mutation (T to C at position 4,369) resulting in a C1477R, and a defect (IVS24 1G to C) that caused differential splicing, whereas the other was shown to carry a missense mutation (C to T at position 3,181 resulting in T929I) and a de novo nonsense mutation] (16).
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ABCA1 p.Cys1477Arg 12700344:80:189
status: NEW[hide] Secretory vesicular transport from the Golgi is al... J Biol Chem. 2003 Mar 21;278(12):10002-5. Epub 2003 Jan 27. Zha X, Gauthier A, Genest J, McPherson R
Secretory vesicular transport from the Golgi is altered during ATP-binding cassette protein A1 (ABCA1)-mediated cholesterol efflux.
J Biol Chem. 2003 Mar 21;278(12):10002-5. Epub 2003 Jan 27., [PMID:12551894]
Abstract [show]
Apolipoprotein AI (apoAI)-mediated cholesterol efflux is a process by which cells export excess cellular cholesterol to apoAI to form high density lipoprotein. ATP-binding cassette protein A1 (ABCA1) has recently been identified as the key regulator of this process. The pathways of intracellular cholesterol transport during efflux are largely unknown nor is the molecular mechanism by which ABCA1 governs cholesterol efflux well understood. Here, we report that, in both macrophages and fibroblasts, the secretory vesicular transport changes in response to apoAI-mediated cholesterol efflux. Vesicular transport from the Golgi to the plasma membrane increased 2-fold during efflux. This increase in vesicular transport during efflux was observed in both raft-poor and raft-rich vesicle populations originated from the Golgi. Importantly, enhanced vesicular transport in response to apoAI is absent in Tangier fibroblasts, a cell type with deficient cholesterol efflux due to functional ABCA1 mutations. These findings are consistent with an efflux model whereby cholesterol is transported from the storage site to the plasma membrane via the Golgi. ABCA1 may influence cholesterol efflux in part by enhancing vesicular trafficking from the Golgi to the plasma membrane.
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No. Sentence Comment
55 The Tangier patient is a compound heterozygote in which one allele gives the mutation C1477R and the other one is a Gly 3 Cys mutation at an exon/intron boundary, causing a splice site mutation and thus a truncated mRNA (5).
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ABCA1 p.Cys1477Arg 12551894:55:86
status: NEW54 The Tangier patient is a compound heterozygote in which one allele gives the mutation C1477R and the other one is a Gly 3 Cys mutation at an exon/intron boundary, causing a splice site mutation and thus a truncated mRNA (5).
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ABCA1 p.Cys1477Arg 12551894:54:86
status: NEW[hide] Cellular phospholipid and cholesterol efflux in hi... Circulation. 2003 Mar 18;107(10):1366-71. Marcil M, Bissonnette R, Vincent J, Krimbou L, Genest J
Cellular phospholipid and cholesterol efflux in high-density lipoprotein deficiency.
Circulation. 2003 Mar 18;107(10):1366-71., [PMID:12642355]
Abstract [show]
BACKGROUND: Prospective studies have examined the relationship between coronary artery disease and low plasma levels of high-density lipoprotein cholesterol (HDL-C). METHODS AND RESULTS: We investigated the causes of hypoalphalipoproteinemia (HypoA; HDL-C <5th percentile) in 64 subjects (12 women and 52 men). Apolipoprotein AI-mediated cellular cholesterol and phospholipid efflux were measured in fibroblasts from HypoA subjects, 9 controls, 2 patients with Tangier disease, and 5 patients with hyperalphalipoproteinemia. A phospholipid efflux defect was defined as <70% of controls. Mean HDL-C was 0.49+/-0.21 mmol/L. Cholesterol and phospholipid efflux correlated strongly (r=0.72, P<0.001). Phospholipid efflux and HDL-C (r=0.64, P<0.001) correlated in HypoA subjects. However, phospholipid or cholesterol efflux was no longer a determinant of HDL-C levels at higher levels (> approximately 1.0 mmol/L) of HDL-C. In HypoA subjects, 4 cases of Tangier disease and 6 of familial HDL deficiency (heterozygous Tangier disease) were identified (10 of 64; 16%). In the remaining 54 subjects, mean lipid efflux was not significantly different from controls and subjects with hyperalphalipoproteinemia. A phospholipid efflux defect was identified in 7 additional HypoA subjects, and a cholesterol efflux defect was detected in 11 subjects. In 2 of these subjects, the ABCA1 gene was ruled out as the cause of the efflux defect, while in 3, the low HDL-C trait segregated with the ABCA1 gene locus. CONCLUSIONS: Lipidation of lipid-poor apolipoprotein AI may not be a major determinant of cholesterol accumulation within more mature HDL particles and increasing cholesterol or phospholipid efflux beyond normal levels may not lead to increase in plasma HDL-C levels. ABCA1 is essential in the initial steps of HDL formation but other plasma events are major modulators of HDL-C levels.
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No. Sentence Comment
85 Molecular Characterization of ABCA1 Gene in Study Subjects Cell Lines HDL-C, mmol/L Nucleotide Change Predicted Protein Alteration TD CTL-1 0.10 Exon 30 T4369C; exon 24 splice site G3C C1477R; part of the transcript deleted TD CTL-2 0.15 Exon 13 A1730G Q597R FHD-1 0.40 Exon 14 ⌬2017-9 ⌬L693 FHD-2 0.18 Exon 48 C6370T R2144X FHD-3 0.39 Exon 41 ⌬5618-23 ⌬ED1893,4 FHD-4 0.18 Exon 18 C2665T R909X FHD-5 0.10 Exon 23 T3667C M1091T FHD-6 0.57 Exon 49 C6844T P2150L, R587W TD-1 0.03 Exon 48 ⌬C6370; ND 2145X TD-2 0.07 ND ND TD-3 0.03 ND 2203X TD-4 0.09 Exon 19 C3181T; ND T929I; ND CTL indicates control.
X
ABCA1 p.Cys1477Arg 12642355:85:185
status: NEW79 Molecular Characterization of ABCA1 Gene in Study Subjects Cell Lines HDL-C, mmol/L Nucleotide Change Predicted Protein Alteration TD CTL-1 0.10 Exon 30 T4369C; exon 24 splice site G3C C1477R; part of the transcript deleted TD CTL-2 0.15 Exon 13 A1730G Q597R FHD-1 0.40 Exon 14 èc;2017-9 èc;L693 FHD-2 0.18 Exon 48 C6370T R2144X FHD-3 0.39 Exon 41 èc;5618-23 èc;ED1893,4 FHD-4 0.18 Exon 18 C2665T R909X FHD-5 0.10 Exon 23 T3667C M1091T FHD-6 0.57 Exon 49 C6844T P2150L, R587W TD-1 0.03 Exon 48 èc;C6370; ND 2145X TD-2 0.07 ND ND TD-3 0.03 ND 2203X TD-4 0.09 Exon 19 C3181T; ND T929I; ND CTL indicates control.
X
ABCA1 p.Cys1477Arg 12642355:79:185
status: NEW[hide] cAMP induces ABCA1 phosphorylation activity and pr... J Lipid Res. 2002 Dec;43(12):2087-94. Haidar B, Denis M, Krimbou L, Marcil M, Genest J Jr
cAMP induces ABCA1 phosphorylation activity and promotes cholesterol efflux from fibroblasts.
J Lipid Res. 2002 Dec;43(12):2087-94., [PMID:12454270]
Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) plays a crucial role in apoA-I lipidation, a key step in reverse cholesterol transport. cAMP induces apoA-I binding activity and promotes cellular cholesterol efflux. We investigated the role of the cAMP/protein kinase A (PKA) dependent pathway in the regulation of cellular cholesterol efflux. Treatment of normal fibroblasts with 8-bromo-cAMP (8-Br-cAMP) increased significantly apoA-I-mediated cholesterol efflux, with specificity for apoA-I, but not for cyclodextrin. Concomitantly, 8-Br-cAMP increased ABCA1 phosphorylation in a time-dependent manner. Maximum phosphorylation was reached in <10 min, representing a 260% increase compared to basal ABCA1 phosphorylation level. Forskolin, a known cAMP regulator, increased both cellular cholesterol efflux and ABCA1 phosphorylation. In contrast, H-89 PKA inhibitor reduced cellular cholesterol efflux by 70% in a dose-dependent manner and inhibited almost completely ABCA1 phosphorylation. To determine whether naturally occurring mutants of ABCA1 may affect its phosphorylation activity, fibroblasts from subjects with familial HDL deficiency (FHD, heterozygous ABCA1 defect) and Tangier disease (TD, homozygous/compound heterozygous ABCA1 defect) were treated with 8-Br-cAMP or forskolin. Cellular cholesterol efflux and ABCA1 phosphorylation were increased in FHD but not in TD cells. Taken together, these findings provide evidence for a link between the cAMP/PKA-dependent pathway, ABCA1 phosphorylation, and apoA-I mediated cellular cholesterol efflux.
Comments [show]
None has been submitted yet.
No. Sentence Comment
176 Molecular characterization of ABCA1 gene in study subjects Cell Lines HDL-C Nucleotide Change Predicted Protein Alteration mmol/l CTR1 1.63 - - CTR2 1.20 - - FHD1 0.27 Exon 14 ⌬2017-9 ⌬L693 FHD2 0.18 Exon 18 C2665T R909X FHD3 0.39 Exon 41 ⌬5618-23 ⌬ED1893,4 FHD4 0.18 Exon 48 C6370T R2144X FHD5 0.09 Exon 36 GG5277,8C fs 1628G, Q1636X TD1 Ͻ0.1 Exon 30 T4369C; Exon 24 splice site G→C C1477R; Part of the transcript deleted TD2 Ͻ0.1 Exon 13 A1730G Q597R TD3 Ͻ0.1 Exon 48 ⌬C6370; nd 2145X; nd FHD1-5 are heterozygous for the reported mutation; TD1,3 are compound heterozygous and TD2 is homozygous.
X
ABCA1 p.Cys1477Arg 12454270:176:390
status: NEWX
ABCA1 p.Cys1477Arg 12454270:176:425
status: NEW[hide] Distinct sites on ABCA1 control distinct steps req... J Lipid Res. 2002 Dec;43(12):2077-86. Rigot V, Hamon Y, Chambenoit O, Alibert M, Duverger N, Chimini G
Distinct sites on ABCA1 control distinct steps required for cellular release of phospholipids.
J Lipid Res. 2002 Dec;43(12):2077-86., [PMID:12454269]
Abstract [show]
The loss of ABCA1 function leads to Tangier dyslipidemia in humans and to a Tangier-like phenotype in mice, by impairing the transformation of nascent apolipoproteins into mature HDL particles. Mechanistically this ensues from the inability of cells to release membrane lipids and cholesterol. Whereas the ability of ABCA1 to promote phospholipid effluxes, surface binding of apolipoproteins and outward flip of membrane lipids has been documented, the relationship between this series of ABCA1-dependent events is still elusive. Here we provide evidence that i) lipid effluxes require both flip of membrane lipids and binding of apolipoproteins to the cell surface, ii) apolipoprotein A-I binding depends on structural determinants on ABCA1, and iii) phospholipid effluxes can be modulated by engineered mutations on the structural determinants identified on ABCA1.
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No. Sentence Comment
60 When analyzing double mutants (HA819/ C1477R and HA819/1466), the comparison was carried out between each double and the relevant loss of function single mutant (C1477R and HA1466, respectively).
X
ABCA1 p.Cys1477Arg 12454269:60:38
status: NEWX
ABCA1 p.Cys1477Arg 12454269:60:162
status: NEW148 This was virtually complete in the case of W590S, Q597R, and ⌬L693, and reduced to one fourth for R587W and C1477R (Table 3).
X
ABCA1 p.Cys1477Arg 12454269:148:115
status: NEW168 C1477R falls into a second class since it is detected at the plasma membrane but elicits a significantly reduced binding of apoA-I as compared with wild-type (33% Ϯ 9, n ϭ 6, P Ͻ 0.01 Table 1).
X
ABCA1 p.Cys1477Arg 12454269:168:0
status: NEW171 Indeed, these variants, while eliciting an apoA-I binding indistinguishable from wild-type ABCA1 (79% Ϯ 5, n ϭ 7, P Ͼ 0.05 and 126% Ϯ 18, n ϭ 6, P Ͼ 0.05 of wild type, respectively) fail to drive both flipping of PS (annexin V binding ϭ 39% Ϯ 11of wild type for R587W, n ϭ 5, P Ͻ 0.05 and 30% Ϯ 9 for W590S, n ϭ 7, P Ͻ 0.01) and membrane release of PL (27% Ϯ 16, n ϭ 3, P Ͻ 0.05 and 16% Ϯ 3, n ϭ 2, P Ͻ 0.01 of wild type, respectively, Table 3), thus indicating that apoA-I binding per se is insufficient for the generation of PL effluxes, which also requires PS flipping.
X
ABCA1 p.Cys1477Arg 12454269:171:50
status: NEW172 HA 819 acts as a suppressive mutations on Tangier C1477R Having observed that we could generate mutant transporters showing opposite behaviors with respect of apoA-I surface binding, we asked which effect could result from the introduction of a gain of function mutation on an hypomorphic mutant allele.
X
ABCA1 p.Cys1477Arg 12454269:172:50
status: NEWX
ABCA1 p.Cys1477Arg 12454269:172:189
status: NEW173 We thus grafted the HA819, which increases selectively apoA-I binding (151% Ϯ 11 of wild type, n ϭ 4, P Ͻ; 0.05), on HA1466 (apoA-I binding ϭ 27% Ϯ 7 of wild type, n ϭ 9, P Ͻ 0.001), and on C1477R (33% Ϯ 9 of wild type, n ϭ 6, P Ͻ 0.01).
X
ABCA1 p.Cys1477Arg 12454269:173:116
status: NEWX
ABCA1 p.Cys1477Arg 12454269:173:231
status: NEW174 The latter showed similar levels of annexin V binding (52% Ϯ 10, n ϭ 7 for HA1466 P Ͼ 0.05 and 53% Ϯ 12, n ϭ 9, for C1477R, P Ͼ 0.05).
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ABCA1 p.Cys1477Arg 12454269:174:146
status: NEW177 In both cases, the presence of an HA tag at position 819 partially and significantly rescued the binding of apoA-I but drove limited and nonsignificant modifications in the annexin V binding with respect to the original loss of function mutation (Table 3; apoA-I binding values reverted to 68% Ϯ 6 for HA819/C1477R, n ϭ 4, P Ͻ 0.05 and to 49% Ϯ 7 for HA819/HA1466, n ϭ 6, P Ͻ 0.05, whereas annexin V binding amounted to 57% Ϯ 15, n ϭ 4, for HA819/ C1477R and 54% Ϯ 12, n ϭ 6 for HA819/HA1466 P Ͼ 0.05).
X
ABCA1 p.Cys1477Arg 12454269:177:88
status: NEWX
ABCA1 p.Cys1477Arg 12454269:177:314
status: NEWX
ABCA1 p.Cys1477Arg 12454269:177:496
status: NEW178 In both cases the ability to induce PL effluxes was also significantly increased (HA819/C1477R ϭ 142% Ϯ 2 4, n ϭ 2, P Ͻ 0.01 and HA819/HA1466 ϭ 108% Ϯ 28, n ϭ 4, P Ͻ 0.05).
X
ABCA1 p.Cys1477Arg 12454269:178:88
status: NEW205 Morphological and functional evaluation of Tangier- associated ABCA1 variants Identity SL AnnV St ApoA-I St PL Efflux St % % % R587W PM 39 Ϯ 11(5) a 79 Ϯ 5 (7) a 27 Ϯ 16 (3) a W590S PM 30 Ϯ 9 (7) b 126 Ϯ 18 (6) ns 16 Ϯ 3 (2) b Q597R ER, PM 24 Ϯ 9 (4) b 15 Ϯ 8 (4) c 8 Ϯ 7 (2) b ⌬L693 ER 26 Ϯ 11 (5) a 12 Ϯ 6 (4) c nd C1477R PM 53 Ϯ 12 (9) ns 33 Ϯ 9 (6) b 12 Ϯ 2 (2) b HA819/1466 PM 54 Ϯ 12 (6) ns 49 Ϯ 7 (6) a 108 Ϯ 28 (4) b HA819/C1477R PM 57 Ϯ 15 (4) ns 68 Ϯ 6 (4) a 142 Ϯ 24 (2) b SL, subcellular localization as detected by confocal imaging and confirmed by surface biotynilation; AnnV and ApoA-I, binding of annexin V or apoA-I in cells successfully transfected with the test construct (GFP positive); St, statistical significance.
X
ABCA1 p.Cys1477Arg 12454269:205:390
status: NEWX
ABCA1 p.Cys1477Arg 12454269:205:540
status: NEW229 Since the presence of disulfide bridges connecting the two halves of the protein has been shown for ABCR and, by extension, suggested for ABCA1, C1477 may well be strategic for the structural configuration of extracellular domains (23); however, considering that the loss of apoA-I binding in C1477R can be rescued by a suppressive mutation in the loop between TM5 and TM6 unable in itself to restore a disulfide bridge, it seems more likely that the coexistence of two discrete modifications in the putative apoA-I docking domain can fine tune its spatial conformation.
X
ABCA1 p.Cys1477Arg 12454269:229:293
status: NEW147 This was virtually complete in the case of W590S, Q597R, and L693, and reduced to one fourth for R587W and C1477R (Table 3).
X
ABCA1 p.Cys1477Arg 12454269:147:108
status: NEW167 C1477R falls into a second class since it is detected at the plasma membrane but elicits a significantly reduced binding of apoA-I as compared with wild-type (33% 9, n 6, P 0.01 Table 1).
X
ABCA1 p.Cys1477Arg 12454269:167:0
status: NEW176 In both cases, the presence of an HA tag at position 819 partially and significantly rescued the binding of apoA-I but drove limited and nonsignificant modifications in the annexin V binding with respect to the original loss of function mutation (Table 3; apoA-I binding values reverted to 68% 6 for HA819/C1477R, n 4, P 0.05 and to 49% 7 for HA819/HA1466, n 6, P 0.05, whereas annexin V binding amounted to 57% 15, n 4, for HA819/ C1477R and 54% 12, n 6 for HA819/HA1466 P 0.05).
X
ABCA1 p.Cys1477Arg 12454269:176:308
status: NEWX
ABCA1 p.Cys1477Arg 12454269:176:448
status: NEW204 Morphological and functional evaluation of Tangier-associated ABCA1 variants Identity SL AnnV St ApoA-I St PL Efflux St % % % R587W PM 39 11(5) a 79 5 (7) a 27 16 (3) a W590S PM 30 9 (7) b 126 18 (6) ns 16 3 (2) b Q597R ER, PM 24 9 (4) b 15 8 (4) c 8 7 (2) b L693 ER 26 11 (5) a 12 6 (4) c nd C1477R PM 53 12 (9) ns 33 9 (6) b 12 2 (2) b HA819/1466 PM 54 12 (6) ns 49 7 (6) a 108 28 (4) b HA819/C1477R PM 57 15 (4) ns 68 6 (4) a 142 24 (2) b SL, subcellular localization as detected by confocal imaging and confirmed by surface biotynilation; AnnV and ApoA-I, binding of annexin V or apoA-I in cells successfully transfected with the test construct (GFP positive); St, statistical significance.
X
ABCA1 p.Cys1477Arg 12454269:204:316
status: NEWX
ABCA1 p.Cys1477Arg 12454269:204:430
status: NEW228 Since the presence of disulfide bridges connecting the two halves of the protein has been shown for ABCR and, by extension, suggested for ABCA1, C1477 may well be strategic for the structural configuration of extracellular domains (23); however, considering that the loss of apoA-I binding in C1477R can be rescued by a suppressive mutation in the loop between TM5 and TM6 unable in itself to restore a disulfide bridge, it seems more likely that the coexistence of two discrete modifications in the putative apoA-I docking domain can fine tune its spatial conformation.
X
ABCA1 p.Cys1477Arg 12454269:228:293
status: NEW[hide] Truncation mutations in ABCA1 suppress normal upre... J Lipid Res. 2002 Nov;43(11):1939-49. Wellington CL, Yang YZ, Zhou S, Clee SM, Tan B, Hirano K, Zwarts K, Kwok A, Gelfer A, Marcil M, Newman S, Roomp K, Singaraja R, Collins J, Zhang LH, Groen AK, Hovingh K, Brownlie A, Tafuri S, Genest J Jr, Kastelein JJ, Hayden MR
Truncation mutations in ABCA1 suppress normal upregulation of full-length ABCA1 by 9-cis-retinoic acid and 22-R-hydroxycholesterol.
J Lipid Res. 2002 Nov;43(11):1939-49., [PMID:12401893]
Abstract [show]
Mutations in ABCA1 uniformly decrease plasma HDL-cholesterol (HDL-C) and reduce cholesterol efflux, yet different mutations in ABCA1 result in different phenotypic effects in heterozygotes. For example, truncation mutations result in significantly lower HDL-C and apoliprotein A-I (apoA-I) levels in heterozygotes compared with nontruncation mutations, suggesting that truncation mutations may negatively affect the wild-type allele. To specifically test this hypothesis, we examined ABCA1 protein expression in response to 9-cis-retinoic acid (9-cis-RA) and 22-R-hydroxycholesterol (22-R-OH-Chol) in a collection of human fibroblasts representing eight different mutations and observed that truncation mutations blunted the response to oxysterol stimulation and dominantly suppressed induction of the remaining full-length allele to 5-10% of wild-type levels. mRNA levels between truncation and nontruncation mutations were comparable, suggesting that ABCA1 expression was suppressed at the protein level. Dominant negative activity of truncated ABCA1 was recapitulated in an in vitro model using transfected Cos-7 cells. Our results suggest that the severe reduction of HDL-C in patients with truncation mutations may be at least partly explained by dominant negative suppression of expression and activity of the remaining full-length ABCA1 allele. These data suggest that ABCA1 requires a physical association with itself or other molecules for normal function and has important pharmacogenetic implications for individuals with truncation mutations.
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None has been submitted yet.
No. Sentence Comment
131 Expression data by mutation Family Mutation Proteinc Induced/Uninduced HDL-C Net Effluxd mmol/l % of control FHA1 Del L 693 5.95 (0.82) 0.4 79.47 (22.63) FHA2 R2144X 2.45 (0.19) 0.18 64.01 (11.12) FHA3 Del E,D 1893, 1894 7.82 (1.48) 0.39 60.03 (11.85) FHA4 R909X 2.32 (0.52) 0.18 72.28 (18.01) FHA5 M1091T 6.42 (0.29) 0.1 47.24 (3.79) TD1 ivs2511G-C, C1477R 3.46 (0.50) 0.1 2.73 (1.05) TD1-ha C1477R 10.28 (1.07) 0.9 58.14 (5.49) TD3 GG 5277C - 1636 2.89 (0.59) 0.09 23.3 (1.29) TD3-hb T9291 6.65 (0.10) 1.12 51.8 (1.30) TD4 Del C 6825 - 2145X, unidentified 1.14 (0.13) 0.03 17.22 (0) Control None 11.31 (0.68) 1.63 100.00 (7.09) a TD1-h is the heterozygous parent of the TD1 proband.
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ABCA1 p.Cys1477Arg 12401893:131:351
status: NEWX
ABCA1 p.Cys1477Arg 12401893:131:393
status: NEW[hide] Naturally occurring mutations in the largest extra... J Biol Chem. 2002 Sep 6;277(36):33178-87. Epub 2002 Jun 25. Fitzgerald ML, Morris AL, Rhee JS, Andersson LP, Mendez AJ, Freeman MW
Naturally occurring mutations in the largest extracellular loops of ABCA1 can disrupt its direct interaction with apolipoprotein A-I.
J Biol Chem. 2002 Sep 6;277(36):33178-87. Epub 2002 Jun 25., [PMID:12084722]
Abstract [show]
The ABCA1 transporter contains two large domains into which many of the genetic mutations in individuals with Tangier disease fall. To investigate the structural requirements for the cellular cholesterol efflux mediated by ABCA1, we have determined the topology of these two domains and generated transporters harboring five naturally occurring missense mutations in them. These mutants, unlike wild type ABCA1, produced little or no apoA-I-stimulated cholesterol efflux when transfected into 293 cells, establishing their causality in Tangier disease. Because all five mutant proteins were well expressed and detectable on the plasma membrane, their interaction with the ABCA1 ligand, apolipoprotein (apo) A-I, was measured using bifunctional cross-linking agents. Four of five mutants had a marked decline in cross-linking to apoA-I, whereas one (W590S) retained full cross-linking activity. Cross-linking of apoA-I was temperature-dependent, rapid in onset, and detectable with both lipid- and water-soluble cross-linking agents. These results suggest that apoA-I-stimulated cholesterol efflux cannot occur without a direct interaction between the apoprotein and critical residues in two extracellular loops of ABCA1. The behavior of the W590S mutant indicates that although binding of apoA-I by ABCA1 may be necessary, it is not sufficient for stimulation of cholesterol efflux.
Comments [show]
None has been submitted yet.
No. Sentence Comment
39 DNA Constructs-Five missense mutants of ABCA1 (R587W, W590S, Q597R, C1477R, and S1506L) were generated using overlap polymerase chain reaction methods, as described previously (17).
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ABCA1 p.Cys1477Arg 12084722:39:68
status: NEW70 Missense Mutations in Two Putative Extracellular Loops of ABCA1 Ablate Efflux Activity-Five missense mutations (R587W, W590S, Q597R, C1477R, and S1506L) were introduced into a wild type ABCA1 cDNA using PCR mutagenesis techniques.
X
ABCA1 p.Cys1477Arg 12084722:70:133
status: NEW72 The other two mutations (C1477R and S1506L) fall within the central loop of the protein.
X
ABCA1 p.Cys1477Arg 12084722:72:25
status: NEW116 The cells were transfected with either empty vector (mock), wild type ABCA1 (WT), or ABCA1 constructs carrying the indicated point mutations (R587W, W590S, Q597R, C1477R, and S1506L).
X
ABCA1 p.Cys1477Arg 12084722:116:163
status: NEW119 Absolute apoA-I and medium efflux values, respectively, are as follows: mock, 1.59 Ϯ 0.04% versus 1.21 Ϯ 0.39%; WT, 3.92 Ϯ 0.13% versus 1.9 Ϯ 0.08%; R587W, 1.78 Ϯ 0.11% versus 1.61 Ϯ 0.24%; W590S, 1.92 Ϯ 0.24% versus 1.63 Ϯ 0.08%; Q597R, 1.5 Ϯ 0.14% versus 1.49 Ϯ 0.03%; C1477R, 1.67 Ϯ 0.18% versus 1.52 Ϯ 0.15%; and S1506L, 1.66 Ϯ 0.28% versus 1.6 Ϯ 0.13%.
X
ABCA1 p.Cys1477Arg 12084722:119:331
status: NEW198 Three of the mutants (Q597R, C1477R, and S1506L) had dramatic reductions in their cross-linking efficiency to apoA-I, relative to the wild type transporter (90% or greater reduction).
X
ABCA1 p.Cys1477Arg 12084722:198:29
status: NEW202 DISCUSSION In this study, we have established that several naturally occurring missense mutations in ABCA1 (R587W, W590S, Q597R, C1477R, and S1506L) located in the two largest loop domains of the protein (comprising amino acids ϳ44-640 and ϳ1371-1649, respectively) are, in fact, loss-of-function mutations.
X
ABCA1 p.Cys1477Arg 12084722:202:53
status: NEWX
ABCA1 p.Cys1477Arg 12084722:202:129
status: NEW210 Only one cysteine mutant was utilized in this study (C1477R), and work is currently underway to determine whether this mutation affects the formation of a disulfide linkage in ABCA1.
X
ABCA1 p.Cys1477Arg 12084722:210:53
status: NEW212 Although three of the mutations (Q597R, C1477R, and S1506L) showed no appreciable cross-linking to apoA-I, the R587W mutant had an intermediate activity, and the W590S mutant retained full, if not enhanced, cross-linking to the apoprotein.
X
ABCA1 p.Cys1477Arg 12084722:212:40
status: NEW37 DNA Constructs-Five missense mutants of ABCA1 (R587W, W590S, Q597R, C1477R, and S1506L) were generated using overlap polymerase chain reaction methods, as described previously (17).
X
ABCA1 p.Cys1477Arg 12084722:37:68
status: NEW67 Missense Mutations in Two Putative Extracellular Loops of ABCA1 Ablate Efflux Activity-Five missense mutations (R587W, W590S, Q597R, C1477R, and S1506L) were introduced into a wild type ABCA1 cDNA using PCR mutagenesis techniques.
X
ABCA1 p.Cys1477Arg 12084722:67:133
status: NEW69 The other two mutations (C1477R and S1506L) fall within the central loop of the protein.
X
ABCA1 p.Cys1477Arg 12084722:69:25
status: NEW112 The cells were transfected with either empty vector (mock), wild type ABCA1 (WT), or ABCA1 constructs carrying the indicated point mutations (R587W, W590S, Q597R, C1477R, and S1506L).
X
ABCA1 p.Cys1477Arg 12084722:112:163
status: NEW115 Absolute apoA-I and medium efflux values, respectively, are as follows: mock, 1.59 afe; 0.04% versus 1.21 afe; 0.39%; WT, 3.92 afe; 0.13% versus 1.9 afe; 0.08%; R587W, 1.78 afe; 0.11% versus 1.61 afe; 0.24%; W590S, 1.92 afe; 0.24% versus 1.63 afe; 0.08%; Q597R, 1.5 afe; 0.14% versus 1.49 afe; 0.03%; C1477R, 1.67 afe; 0.18% versus 1.52 afe; 0.15%; and S1506L, 1.66 afe; 0.28% versus 1.6 afe; 0.13%.
X
ABCA1 p.Cys1477Arg 12084722:115:331
status: NEW190 Three of the mutants (Q597R, C1477R, and S1506L) had dramatic reductions in their cross-linking efficiency to apoA-I, relative to the wild type transporter (90% or greater reduction).
X
ABCA1 p.Cys1477Arg 12084722:190:29
status: NEW194 DISCUSSION In this study, we have established that several naturally occurring missense mutations in ABCA1 (R587W, W590S, Q597R, C1477R, and S1506L) located in the two largest loop domains of the protein (comprising amino acids b03;44-640 and b03;1371-1649, respectively) are, in fact, loss-of-function mutations.
X
ABCA1 p.Cys1477Arg 12084722:194:129
status: NEW204 Although three of the mutations (Q597R, C1477R, and S1506L) showed no appreciable cross-linking to apoA-I, the R587W mutant had an intermediate activity, and the W590S mutant retained full, if not enhanced, cross-linking to the apoprotein.
X
ABCA1 p.Cys1477Arg 12084722:204:40
status: NEW[hide] Association between increased arterial-wall thickn... Lancet. 2002 Jan 5;359(9300):37-42. van Dam MJ, de Groot E, Clee SM, Hovingh GK, Roelants R, Brooks-Wilson A, Zwinderman AH, Smit AJ, Smelt AH, Groen AK, Hayden MR, Kastelein JJ
Association between increased arterial-wall thickness and impairment in ABCA1-driven cholesterol efflux: an observational study.
Lancet. 2002 Jan 5;359(9300):37-42., [PMID:11809185]
Abstract [show]
BACKGROUND: Decreased concentrations of HDL cholesterol are associated with increased cardiovascular risk. These concentrations are directly related to cholesterol efflux from cells-the first step and a key process in reverse cholesterol transport. Cholesterol efflux is mediated by the ATP-binding cassette A1 transporter (ABCA1), the rate-limiting step in the production of HDL. We aimed to assess the relation between cholesterol efflux, HDL concentrations, and arterial-wall changes in individuals with impaired ABCA1 function. METHODS: We investigated 30 individuals from families with ABCA1 mutations, and 110 controls matched for age, sex, and ethnic origin. We measured concentrations of HDL cholesterol in plasma and intima-media thickness of the carotid arteries by B-mode ultrasonography in all participants. We also measured cholesterol efflux from skin fibroblasts in nine individuals with ABCA1 mutations and in ten controls. FINDINGS: Individuals with ABCA1 mutations had lower amounts of cholesterol efflux, lower HDL cholesterol concentrations, and greater intima-media thicknesses than controls. An intima-media thickness at the upper limit of normal (0.80 mm) was reached by age 55 years in the ABCA1 heterozygotes, and at age 80 years in unaffected controls (p<0.0001). Additionally, strong positive correlations were seen between HDL cholesterol concentrations and cholesterol efflux (r=0.90, p=0.001), and negative correlations between apolipoprotein-AI-mediated (r=-0.61, p=0.030) and HDL-particle-mediated (r=-0.60, p=0.018) efflux and intima-media thickness in the ABCA1 mutation carriers. INTERPRETATION: These results show a direct relation between ABCA1-mediated cellular cholesterol efflux and arterial-wall thickness, and therefore suggest that increasing efflux could inhibit atherosclerosis progression before the manifestation of symptomatic cardiovascular disease.
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None has been submitted yet.
No. Sentence Comment
52 The ABCA1 mutations in NL-014 and NL-016, which have been previously described, consist of 4369T→C (C1477R) and 3212T→C (M1091T), respectively.6,9 Mutation carriers from the two newly discovered families with familial hypoalphalipoproteinaemia NL-020 and NL-016 had a 6844C→T (P2150L) and a 3181C→T (T929I) mutation in the ABCA1 gene respectively.
X
ABCA1 p.Cys1477Arg 11809185:52:106
status: NEW[hide] ABCA1 mutation carriers with low high-density lipo... Eur Heart J. 2013 Jan;34(4):286-91. doi: 10.1093/eurheartj/ehs376. Epub 2012 Nov 7. Bochem AE, van Wijk DF, Holleboom AG, Duivenvoorden R, Motazacker MM, Dallinga-Thie GM, de Groot E, Kastelein JJ, Nederveen AJ, Hovingh GK, Stroes ES
ABCA1 mutation carriers with low high-density lipoprotein cholesterol are characterized by a larger atherosclerotic burden.
Eur Heart J. 2013 Jan;34(4):286-91. doi: 10.1093/eurheartj/ehs376. Epub 2012 Nov 7., [PMID:23136402]
Abstract [show]
AIMS: Low HDL-C is a potent risk factor for cardiovascular disease (CVD). Yet, mutations in ABCA1, a major determinant of circulating HDL-C levels, were previously not associated with CVD risk in cohort studies. To study the consequences of low plasma levels of high-density lipoprotein cholesterol (HDL-C) due to ATP-binding cassette transporter A1 (ABCA1) dysfunction for atherosclerotic vascular disease in the carotid arteries. METHODS AND RESULTS: We performed 3.0 Tesla magnetic resonance imaging (MRI) measurements of the carotid arteries in 36 carriers of high impact functional ABCA1 mutations and 36 normolipidemic controls. Carriers presented with 42% lower HDL-C levels (P < 0.001), a larger mean wall area (18.6 +/- 6.0 vs. 15.8 +/- 4.3 mm(2); P = 0.02), a larger mean wall thickness (0.82 +/- 0.21 vs. 0.70 +/- 0.14 mm; P = 0.005), and a higher normalized wall index (0.37 +/- 0.06 vs. 0.33 +/- 0.04; P = 0.005) compared with controls, retaining significance after adjustment for smoking, alcohol consumption, systolic blood pressure, diabetes, body mass index, history of CVD, LDL-C, and statin use (P = 0.002). CONCLUSION: Carriers of loss of function ABCA1 mutations display a larger atherosclerotic burden compared with age and sex-matched controls, implying a higher risk for CVD. Further studies are needed to elucidate the full function of ABCA1 in the protection against atherosclerosis. These data support the development of strategies to up-regulate ABCA1 in patients with established CVD.
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No. Sentence Comment
81 Efflux measured in fibroblasts from a heterozygous p.Cys1477Arg carrier was used as a positive control since the efflux capacity has consistently been shown to be impaired.19,27 One patient compound heterozygous for mutation p.Arg579Gln and p.Val771Met was included.
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ABCA1 p.Cys1477Arg 23136402:81:53
status: NEW[hide] Factors controlling nascent high-density lipoprote... FASEB J. 2013 Jul;27(7):2880-92. doi: 10.1096/fj.12-216564. Epub 2013 Mar 29. Lyssenko NN, Nickel M, Tang C, Phillips MC
Factors controlling nascent high-density lipoprotein particle heterogeneity: ATP-binding cassette transporter A1 activity and cell lipid and apolipoprotein AI availability.
FASEB J. 2013 Jul;27(7):2880-92. doi: 10.1096/fj.12-216564. Epub 2013 Mar 29., [PMID:23543682]
Abstract [show]
Nascent high-density lipoprotein (HDL) particles arise in different sizes. We have sought to uncover factors that control this size heterogeneity. Gel filtration, native PAGE, and protein cross-linking were used to analyze the size heterogeneity of nascent HDL produced by BHK-ABCA1, RAW 264.7, J774, and HepG2 cells under different levels of two factors considered as a ratio, the availability of apolipoprotein AI (apoAI) -accessible cell lipid, and concentration of extracellular lipid-free apoAI. Increases in the available cell lipid:apoAI ratio due to either elevated ATP-binding cassette transporter A1 (ABCA1) expression and activity or raised cell density (i.e., increasing numerator) shifted the production of nascent HDL from smaller particles with fewer apoAI molecules per particle and fewer molecules of choline-phospholipid and cholesterol per apoAI molecule to larger particles that contained more apoAI and more lipid per molecule of apoAI. A further shift to larger particles was observed in BHK-ABCA1 cells when the available cell lipid:apoAI ratio was raised still higher by decreasing the apoAI concentration (i.e., the denominator). These changes in nascent HDL biogenesis were reminiscent of the transition that occurs in the size composition of reconstituted HDL in response to an increasing initial lipid:apoAI molar ratio. Thus, the ratio of available cell lipid:apoAI is a fundamental cause of nascent HDL size heterogeneity, and rHDL formation is a good model of nascent HDL biogenesis.
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No. Sentence Comment
37 MATERIALS AND METHODS Cell culture and biogenesis of nascent HDL BHK-ABCA1, BHK-ABCA1(W590S), and BHK-ABCA1(C1477R) cells expressing human wild-type or mutant ABCA1 have been previously described (36, 37).
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ABCA1 p.Cys1477Arg 23543682:37:108
status: NEW166 Mutations in ABCA1 that compromise its functionality shift nascent HDL production to the smaller particle species W590S and C1477R are naturally occurring mutations in human ABCA1 that impair its functionality and cause Tangier disease (49) but do not affect its subcellular localization or expression levels (37).
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ABCA1 p.Cys1477Arg 23543682:166:124
status: NEW167 To determine how deficiency in ABCA1 functionality affects size heterogeneity of nascent HDL particles, BHK-ABCA1, BHK-ABCA1(W590S), and BHK-ABCA1(C1477R) cells were plated at the same density, labeled with [3 H]cholesterol, induced to express ABCA1 at the maximum level, and exposed to a high concentration of human lipid-free apoAI, followed by the regular procedure to collect and analyze nascent HDL via gel filtration.
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ABCA1 p.Cys1477Arg 23543682:167:147
status: NEW168 The total amount of newly generated nascent HDL, the [3 H]cholesterol large/small particle ratio, and the size of the larger particles were all the lowest for the C1477R mutant, intermediate for the W509S variant, and the highest for the wild-type ABCA1 (Fig. 7).
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ABCA1 p.Cys1477Arg 23543682:168:163
status: NEW194 BHK cells expressing wild-type ABCA1, ABCA1(W590S), or ABCA1(C1477R) were plated at the same density, labeled with [3 H]cholesterol, treated with 10 nM mifepristone, and exposed to 10 òe;g/ml of human apoAI to generate nascent HDL.
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ABCA1 p.Cys1477Arg 23543682:194:61
status: NEW195 The decreased size of gel-filtration elution peaks indicates that W590S and especially C1477R mutations dramatically reduced the ability of ABCA1 to facilitate nascent HDL assembly.
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ABCA1 p.Cys1477Arg 23543682:195:87
status: NEW[hide] ABCA1 mediates unfolding of apolipoprotein AI N te... Arterioscler Thromb Vasc Biol. 2013 Jun;33(6):1197-205. doi: 10.1161/ATVBAHA.112.301195. Epub 2013 Apr 4. Wang S, Gulshan K, Brubaker G, Hazen SL, Smith JD
ABCA1 mediates unfolding of apolipoprotein AI N terminus on the cell surface before lipidation and release of nascent high-density lipoprotein.
Arterioscler Thromb Vasc Biol. 2013 Jun;33(6):1197-205. doi: 10.1161/ATVBAHA.112.301195. Epub 2013 Apr 4., [PMID:23559627]
Abstract [show]
OBJECTIVE: To gain insight into the mechanism by which ABCA1 generates nascent high-density lipoprotein. APPROACH AND RESULTS: HEK293 cells were stably transfected with ABCA1 vectors, encoding wild type, and the W590S and C1477R Tangier disease mutation isoforms, along with the K939M ATP-binding domain mutant. Apolipoprotein AI (ApoAI) binding, plasma membrane remodeling, cholesterol efflux, apoAI cell surface unfolding, and apoAI cell surface lipidation were determined, the latter 2 measured using novel fluorescent apoAI indicators. The W590S isoform had decreased plasma membrane remodeling and lipid efflux activities, and the C1477R isoform had decreased apoAI binding, and lipid efflux activities, whereas the K939M isoform did not bind apoAI, remodel the membrane, or efflux cholesterol. However, all ABCA1 isoforms led to apoAI unfolding at the cell surface, which was higher for the isoforms that increased apoAI binding. ApoAI lipidation was not detected on ABCA1-expressing cells, only in the conditioned medium, consistent with rapid release of nascent high-density lipoprotein from ABCA1-expressing cells. CONCLUSIONS: We identified a third activity of ABCA1, the ability to unfold the N terminus of apoAI on the cell surface. Our results support a model in which unfolded apoAI on the cell surface is an intermediate in its lipidation and that, once apoAI is lipidated, it forms an unstable structure that is rapidly released from the cells to generate high-density lipoprotein.
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No. Sentence Comment
1 One recent model from Phillips proposes that ABCA1 shuttles phospholipids from the inner to extracellular face of the plasma membrane, resulting in membrane bulges with high curvature that are sufficient to allow apoAI penetration and nHDL formation.4 Mutations in ABCA1 lead to Tangier disease and familial hypoalphalipoproteinemia, characterized by very low levels of plasma HDL-cholesterol.5 Functional studies of certain Tangier disease mutations that are properly trafficked to the plasma membrane demonstrate that ABCA1 seems to have at least 2 distinct activities6 : apoAI binding and plasma membrane remodeling, the latter demonstrated through phosphatidylserine (PS) translocation to the outer leaflet of the plasma membrane.7 The W590S mutation in the first extracellular domain of ABCA1 is defective in PS translocation, but competent for apoAI binding.5,7,8 In contrast, the C1477R mutation in the second extracellular domain of ABCA1 is defective in apoAI binding, but competent for PS translocation.7 Further demonstration of the ability of ABCA1, and the deficit of W590S isoform, to remodel the plasma membrane was provided by Nagao et al,8 who used sodium taurocholate (NaTC) as a weak detergent extracellular lipid acceptor; wild type (WT) but not W590S ABAC1 mediates increased lipid efflux to NaTC.
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ABCA1 p.Cys1477Arg 23559627:1:887
status: NEW4 Approach and Results-HEK293 cells were stably transfected with ABCA1 vectors, encoding wild type, and the W590S and C1477R Tangier disease mutation isoforms, along with the K939M ATP-binding domain mutant.
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ABCA1 p.Cys1477Arg 23559627:4:116
status: NEW6 The W590S isoform had decreased plasma membrane remodeling and lipid efflux activities, and the C1477R isoform had decreased apoAI binding, and lipid efflux activities, whereas the K939M isoform did not bind apoAI, remodel the membrane, or efflux cholesterol.
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ABCA1 p.Cys1477Arg 23559627:6:96
status: NEW24 HEK293 cells were stably transfected with different murine ABCA1-green fluorescent protein (GFP) fusion vectors encoding WT, K939M, W590S, and C1477R isoforms, the latter 2 identified as Tangier disease-causing mutations in the first and second large extracellular domains, respectively.6 Several clonally derived cell lines from each construction were screened by confocal fluorescence microscopy and flow cytometry to select lines for further study with equivalent ABCA1 expression.
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ABCA1 p.Cys1477Arg 23559627:24:143
status: NEW25 As previously described,5,9 WT, W590S, C1477R, and K939M ABCA1-GFP fusions were processed correctly in cells and expressed on the plasma membrane (Figure 1A).
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ABCA1 p.Cys1477Arg 23559627:25:39
status: NEW29 In contrast, the C1477R and K939M isoform-expressing cells had no significant increase in apoAI binding compared with control cells (by ANOVA posttest).
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ABCA1 p.Cys1477Arg 23559627:29:17
status: NEW31 We were able to take advantage of this nonspecific apoAI binding to the control and the C1477R and K939M isoform-expressing cells in cell studies described below.
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ABCA1 p.Cys1477Arg 23559627:31:88
status: NEW32 ABCA1 has been shown to possess PS floppase activity, resulting in plasma membrane remodeling that has been postulated to facilitate HDL assembly.7 Using flow cytometry to measure cell surface PS assayed by Cy5-AnnexinV binding, we showed that WT and C1477R-ABCA1 isoforms increased cell surface PS by ࣈ2.2-fold compared with control cells (P<0.001 by ANOVA posttest).
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ABCA1 p.Cys1477Arg 23559627:32:251
status: NEW34 Thus, our results confirmed previous findings by Singaraja et al5 and Nagao et al8 that the W590S mutation in ABCA1`s first extracellular domain greatly diminishes PS floppase activity indicative of a defect in plasma membrane remodeling, whereas the C1477R mutation in its second large extracellular domain abolishes apoAI binding.
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ABCA1 p.Cys1477Arg 23559627:34:251
status: NEW36 In the absence of any acceptor, WT ABCA1 increased basal 3 H cholesterol efflux by 32% (P<0.05 by ANOVA posttest versus HEK), which has previously been shown to be attributable to increased microparticle release.14 The C1477R-ABCA1 isoform also had increased basal cholesterol efflux activity (34% increase; P<0.05); however, efflux from the W590S-ABCA1 isoform cell line was not significantly different from the control HEK cells.
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ABCA1 p.Cys1477Arg 23559627:36:219
status: NEW39 A, Confocal microscopy of wild type (WT), W590S, C1477R, and K939M ABCA1-GFP isoforms shows cell surface expression.
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ABCA1 p.Cys1477Arg 23559627:39:49
status: NEW40 B, Similar expression levels of WT, W590S, C1477R, and K939M ABCA1-GFP cell lines shown by flow cytometry (n=3; mean&#b1;SD; different numbers above the bars show P<0.001, by ANOVA posttest).
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ABCA1 p.Cys1477Arg 23559627:40:43
status: NEW42 Interestingly, both Tangier disease mutations supported partial efflux to apoAI with 4.27and 4.02-fold increases above the control HEK cells for the W590S and C1477R isoforms, respectively.
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ABCA1 p.Cys1477Arg 23559627:42:159
status: NEW43 All 4 cell lines have significantly different efflux to apoAI (P<0.001 by ANOVA posttest), except for efflux from the W590S and C1477R cells that were not different from each other.
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ABCA1 p.Cys1477Arg 23559627:43:128
status: NEW47 However, the C1477R-ABCA1 isoform yielded 5.04% cholesterol efflux, more similar to the WT ABCA1 isoform.
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ABCA1 p.Cys1477Arg 23559627:47:13
status: NEW48 Thus, both in the absence of acceptor or in the presence of NaTC, cholesterol efflux followed PS floppase activity (highest for WT and C1477R isoforms), and we confirmed the use of NaTC acceptor as an independent indicator of ABCA1-mediated membrane remodeling.
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ABCA1 p.Cys1477Arg 23559627:48:135
status: NEW49 Thus, our findings show that ABCA1 mutations that disrupt either plasma membrane remodeling (W590S) or apoAI binding (C1477R) are still competent to mediate cholesterol efflux to apoAI, albeit at reduced efficiency.
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ABCA1 p.Cys1477Arg 23559627:49:118
status: NEW62 A, Alexa647-labeled apoAI binding to nontransfected cells (HEK) and cells stably transfected with wild type (WT), W590S, C1477R, and K939M ABCA1-green fluorescent protein (GFP) vectors assayed by flow cytometry (n=3; mean&#b1;SD; P<0.0005 for HEK in the presence or absence of labeled apoAI by t test; for the 5 cell types in the presence of labeled apoAI different numbers above the bars show P<0.001; by ANOVA posttest).
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ABCA1 p.Cys1477Arg 23559627:62:121
status: NEW64 C, Cholesterol efflux from control HEK cells and WT, W590S, and C1477R ABCA1-GFP transfected cells in the absence of exogenous acceptors or in the presence of 5 bc;g/mL apoAI or 2 mmol/L sodium taurocholate (NaTC; n=3; mean&#b1;SD; different numbers above the bars show P<0.05, by ANOVA posttest).
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ABCA1 p.Cys1477Arg 23559627:64:64
status: NEW69 Here, we took advantage of the high sensitivity of flow cytometry and our observation that even control HEK cells and cells expressing the apoAI-binding defective C1477R and K939M-ABCA1 isoforms bound apoAI nonspecifically, enabling us to determine the Bodipy-TMR/Alexa647 ratio of each cell.
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ABCA1 p.Cys1477Arg 23559627:69:163
status: NEW75 The other partially active C1477R isoform has 2 activities: apoAI unfolding (albeit reduced) and plasma membrane remodeling.
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ABCA1 p.Cys1477Arg 23559627:75:27
status: NEW113 We chose to further study 2 specific mutations in the first (W590S) and second (C1477R) extracellular domains, respectively, based on their previously identified distinct activities.
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ABCA1 p.Cys1477Arg 23559627:113:80
status: NEW114 Fitzgerald et al17 examined 5 Tangier disease mutations that mapped to the 2 large extracellular domains, and reported that only the W590S mutation in the first extracellular domain was still competent to mediate apoAI cross-linking, whereas other mutations in the first (R587W and Q597R) and second (C1477R and S1506L) extracellular domains could not mediate apoAI cross-linking.
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ABCA1 p.Cys1477Arg 23559627:114:301
status: NEW116 Our findings reproduce that the W590S isoform has plasma membrane localization and WT levels of apoAI-binding activity; and that it has partial cholesterol efflux activity to extracellular apoAI compared with the WT isoform, as previously demonstrated.5,7,8,18 We chose to study the C1477R mutation in the second extracellular domain because it is processed correctly to the plasma membrane and has defective apoAI binding,5,7,17 but it retains its PS translocase activity and partial efflux activity,7 all findings that we confirmed in the current study, where we found ࣈ50% cholesterol efflux activity to apoAI.
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ABCA1 p.Cys1477Arg 23559627:116:283
status: NEW118 Here, we compared the acceptor activity of NaTC for cells expressing WT, W590S, and C1477R-ABCA1 isoforms, and found that the C1477R mutant has equivalent efflux to NaTC as the WT isoform, whereas the W590S mutant has no detectable efflux to NaTC above nontransfected cells.
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ABCA1 p.Cys1477Arg 23559627:118:84
status: NEWX
ABCA1 p.Cys1477Arg 23559627:118:126
status: NEW119 The NaTC efflux activities of these ABCA1 isoforms is similar to the PS translocase activity, and thus both of these assays are evidence that the WT and C1477R isoforms can remodel the plasma membrane, whereas the W590S isoform is mostly deficient in this activity.
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ABCA1 p.Cys1477Arg 23559627:119:153
status: NEW[hide] Regulation of signal transduction by HDL. J Lipid Res. 2013 Sep;54(9):2315-24. doi: 10.1194/jlr.R039479. Epub 2013 May 18. Mineo C, Shaul PW
Regulation of signal transduction by HDL.
J Lipid Res. 2013 Sep;54(9):2315-24. doi: 10.1194/jlr.R039479. Epub 2013 May 18., [PMID:23687307]
Abstract [show]
High density lipoprotein (HDL) cholesterol has direct effects on numerous cell types that influence cardiovascular and metabolic health. These include endothelial cells, vascular smooth-muscle cells, leukocytes, platelets, adipocytes, skeletal muscle myocytes, and pancreatic beta cells. The effects of HDL or apoA-I, its major apolipoprotein, occur through the modulation of intracellular calcium, oxygen-derived free-radical production, numerous kinases, and enzymes, including endothelial nitric-oxide synthase (eNOS). ApoA-I and HDL also influence gene expression, particularly genes encoding mediators of inflammation in vascular cells. In many paradigms, the change in intracellular signaling occurs as a result of cholesterol efflux, with the cholesterol acceptor methyl-beta-cyclodextrin often invoking responses identical to HDL or apoA-I. The ABC transporters ABCA1 and ABCG1 and scavenger receptor class B, type I (SR-BI) frequently participate in the cellular responses. Structure-function relationships are emerging for signal initiation by ABCA1 and SR-BI, with plasma membrane cholesterol binding by the C-terminal transmembrane domain of SR-BI uniquely enabling it to serve as a sensor of changes in membrane cholesterol. Further investigation of the processes underlying HDL and apoA-I modulation of intracellular signaling will potentially reveal new prophylactic and therapeutic strategies to optimize both cardiovascular and metabolic health.
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No. Sentence Comment
152 In studies of cAMP production and ABCA1 phosphorylation mediated by the apoA-I/ABCA1 tandem, it was found that mutations of ABCA1 associated with Tangier disease (C1477R, 2203X, and 2145X) cause the attenuation of both responses (99).
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ABCA1 p.Cys1477Arg 23687307:152:163
status: NEW[hide] Differential phospholipid substrates and direction... J Biol Chem. 2013 Nov 29;288(48):34414-26. doi: 10.1074/jbc.M113.508812. Epub 2013 Oct 4. Quazi F, Molday RS
Differential phospholipid substrates and directional transport by ATP-binding cassette proteins ABCA1, ABCA7, and ABCA4 and disease-causing mutants.
J Biol Chem. 2013 Nov 29;288(48):34414-26. doi: 10.1074/jbc.M113.508812. Epub 2013 Oct 4., [PMID:24097981]
Abstract [show]
ABCA1, ABCA7, and ABCA4 are members of the ABCA subfamily of ATP-binding cassette transporters that share extensive sequence and structural similarity. Mutations in ABCA1 cause Tangier disease characterized by defective cholesterol homeostasis and high density lipoprotein (HDL) deficiency. Mutations in ABCA4 are responsible for Stargardt disease, a degenerative disorder associated with severe loss in central vision. Although cell-based studies have implicated ABCA proteins in lipid transport, the substrates and direction of transport have not been firmly established. We have purified and reconstituted ABCA1, ABCA7, and ABCA4 into liposomes for fluorescent-lipid transport studies. ABCA1 actively exported or flipped phosphatidylcholine, phosphatidylserine, and sphingomyelin from the cytoplasmic to the exocytoplasmic leaflet of membranes, whereas ABCA7 preferentially exported phosphatidylserine. In contrast, ABCA4 transported phosphatidylethanolamine in the reverse direction. The same phospholipids stimulated the ATPase activity of these ABCA transporters. The transport and ATPase activities of ABCA1 and ABCA4 were reduced by 25% in the presence of 20% cholesterol. Nine ABCA1 Tangier mutants and the corresponding ABCA4 Stargardt mutants showed significantly reduced phospholipid transport activity and subcellular mislocalization. These studies provide the first direct evidence for ABCA1 and ABCA7 functioning as phospholipid transporters and suggest that this activity is an essential step in the loading of apoA-1 with phospholipids for HDL formation.
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No. Sentence Comment
65 Mutations introduced by overlap extension PCR using Pfu AD DNA polymerase in ABCA1 included S100C, W590S, F593L, N935S, T929I, C1477R, T1512M, R2081W, and P2150L.
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ABCA1 p.Cys1477Arg 24097981:65:127
status: NEW67 ABCA1-MM was constructed to harbor the Walker A-motif lysine-to-methionine mutations K939M/K1952M by the nested PCR method; ABCA4-MM had the corresponding K969M/ K1969M Walker A mutations (37), and ABCA7-MM had the Lipid Transport Activity of ABCA Transporters NOVEMBER 29, 2013ߦVOLUME 288ߦNUMBER 48 JOURNAL OF BIOLOGICAL CHEMISTRY 34415 at SEMMELWEIS UNIV OF MEDICINE on December 3, K847M/K1833M Walker A mutations.
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ABCA1 p.Cys1477Arg 24097981:67:127
status: NEW208 Expression and Purification of Disease-causing ABCA1 and ABCA4 Mutants-As part of this study, we have generated a number of disease-causing mutations in ABCA1 and ABCA4 to determine their effect on the expression and functional properties of these transporters. We focused our studies on nine missense mutations in ABCA1 known to cause Tangier disease, including three (S100C, W590S, and F593L) in ECD1, two (T929I and N935S) in the NBD1, two (C1477R and T1512M) in ECD2, one (R2081W) in NBD2, and one (P2150L) in the C-terminal segment as shown in Fig. 6A (blue).
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ABCA1 p.Cys1477Arg 24097981:208:444
status: NEW223 Finally, the null mutant C1502X associated with Stargardt disease was modified to C1502R to reflect the primary sequence change of the corresponding C1477R mutant in ABCA1 linked to Tangier disease.
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ABCA1 p.Cys1477Arg 24097981:223:149
status: NEW226 The levels of expression of the ABCA1 and ABCA4 mutants were generally lower than the corresponding WT proteins with the ABCA1 mutants S100C and R2081W and the corresponding ABCA4 mutants S100P and R2107P expressing at levels less than 25% of WT and the remaining mutants expressing in the range of 35-90% of the WT proteins.
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ABCA1 p.Cys1477Arg 24097981:226:149
status: NEW229 Variants in the ECD1 (S100C, W590S, and F593L), NBD1 (T929I and N935S), and NBD2 (R2081W) of ABCA1 showed significantly reduced ATPase activities in the range of 20-35% of WT activity (Fig. 7A).
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ABCA1 p.Cys1477Arg 24097981:229:4
status: NEW231 The C1477R mutant in ECD2 showed an intermediate reduction in activity.
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ABCA1 p.Cys1477Arg 24097981:231:4
status: NEW232 ABCA4 variants showed a similar ATPase activity profile as the ABCA1 mutants with the exception of the T1537M mutation of ABCA4, which was significantly lower than the corresponding T1512M mutant in ABCA1.
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ABCA1 p.Cys1477Arg 24097981:232:174
status: NEW234 As shown in Fig. 8, A and B, the Fl-PC flippase activity of the ABCA1 mutants and the Fl-PE flippase activity of ABCA4 mutants have a similar profile with the ABCA1 variants C1477R, T1512M, and P2150L and corresponding ABCA4 variants C1502R, T1537M, and P2180L showing transport activities ranging from 60 to 80% of the WT protein and the other mutants showing reduced activity in the range of 20-40% of the WT protein.
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ABCA1 p.Cys1477Arg 24097981:234:4
status: NEWX
ABCA1 p.Cys1477Arg 24097981:234:174
status: NEW251 Some disease alleles such as W590S, C1477R, and P2150L (ABCA1) have conserved residues in ABCA4, but mutations in these positions in ABCA4 have yet to be linked to Stargardt disease.
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ABCA1 p.Cys1477Arg 24097981:251:36
status: NEW295 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (20-30% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT).
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ABCA1 p.Cys1477Arg 24097981:295:153
status: NEW311 For example, the C1477R mutant shows intermediate (b03;60% WT) phospholipid transport activity, whereas it shows minimum (b0d;20% WT) phospholipid efflux activity.
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ABCA1 p.Cys1477Arg 24097981:311:17
status: NEW211 Expression and Purification of Disease-causing ABCA1 and ABCA4 Mutants-As part of this study, we have generated a number of disease-causing mutations in ABCA1 and ABCA4 to determine their effect on the expression and functional properties of these transporters. We focused our studies on nine missense mutations in ABCA1 known to cause Tangier disease, including three (S100C, W590S, and F593L) in ECD1, two (T929I and N935S) in the NBD1, two (C1477R and T1512M) in ECD2, one (R2081W) in NBD2, and one (P2150L) in the C-terminal segment as shown in Fig. 6A (blue).
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ABCA1 p.Cys1477Arg 24097981:211:444
status: NEW237 As shown in Fig. 8, A and B, the Fl-PC flippase activity of the ABCA1 mutants and the Fl-PE flippase activity of ABCA4 mutants have a similar profile with the ABCA1 variants C1477R, T1512M, and P2150L and corresponding ABCA4 variants C1502R, T1537M, and P2180L showing transport activities ranging from 60 to 80% of the WT protein and the other mutants showing reduced activity in the range of 20-40% of the WT protein.
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ABCA1 p.Cys1477Arg 24097981:237:174
status: NEW254 Some disease alleles such as W590S, C1477R, and P2150L (ABCA1) have conserved residues in ABCA4, but mutations in these positions in ABCA4 have yet to be linked to Stargardt disease.
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ABCA1 p.Cys1477Arg 24097981:254:36
status: NEW298 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (20-30% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT).
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ABCA1 p.Cys1477Arg 24097981:298:153
status: NEW314 For example, the C1477R mutant shows intermediate (b03;60% WT) phospholipid transport activity, whereas it shows minimum (b0d;20% WT) phospholipid efflux activity.
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ABCA1 p.Cys1477Arg 24097981:314:17
status: NEW64 Mutations introduced by overlap extension PCR using Pfu AD DNA polymerase in ABCA1 included S100C, W590S, F593L, N935S, T929I, C1477R, T1512M, R2081W, and P2150L.
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ABCA1 p.Cys1477Arg 24097981:64:127
status: NEW206 Expression and Purification of Disease-causing ABCA1 and ABCA4 Mutants-As part of this study, we have generated a number of disease-causing mutations in ABCA1 and ABCA4 to determine their effect on the expression and functional properties of these transporters. We focused our studies on nine missense mutations in ABCA1 known to cause Tangier disease, including three (S100C, W590S, and F593L) in ECD1, two (T929I and N935S) in the NBD1, two (C1477R and T1512M) in ECD2, one (R2081W) in NBD2, and one (P2150L) in the C-terminal segment as shown in Fig. 6A (blue).
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ABCA1 p.Cys1477Arg 24097981:206:444
status: NEW221 Finally, the null mutant C1502X associated with Stargardt disease was modified to C1502R to reflect the primary sequence change of the corresponding C1477R mutant in ABCA1 linked to Tangier disease.
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ABCA1 p.Cys1477Arg 24097981:221:149
status: NEW249 Some disease alleles such as W590S, C1477R, and P2150L (ABCA1) have conserved residues in ABCA4, but mutations in these positions in ABCA4 have yet to be linked to Stargardt disease.
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ABCA1 p.Cys1477Arg 24097981:249:36
status: NEW293 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (2030% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT).
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ABCA1 p.Cys1477Arg 24097981:293:152
status: NEW309 For example, the C1477R mutant shows intermediate (b03;60% WT) phospholipid transport activity, whereas it shows minimum (b0d;20% WT) phospholipid efflux activity.
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ABCA1 p.Cys1477Arg 24097981:309:17
status: NEW[hide] Sphingomyelin depletion impairs anionic phospholip... J Biol Chem. 2013 Dec 27;288(52):37166-79. doi: 10.1074/jbc.M113.512244. Epub 2013 Nov 12. Gulshan K, Brubaker G, Wang S, Hazen SL, Smith JD
Sphingomyelin depletion impairs anionic phospholipid inward translocation and induces cholesterol efflux.
J Biol Chem. 2013 Dec 27;288(52):37166-79. doi: 10.1074/jbc.M113.512244. Epub 2013 Nov 12., [PMID:24220029]
Abstract [show]
The phosphatidylserine (PS) floppase activity (outward translocation) of ABCA1 leads to plasma membrane remodeling that plays a role in lipid efflux to apolipoprotein A-I (apoAI) generating nascent high density lipoprotein. The Tangier disease W590S ABCA1 mutation has defective PS floppase activity and diminished cholesterol efflux activity. Here, we report that depletion of sphingomyelin by inhibitors or sphingomyelinase caused plasma membrane remodeling, leading to defective flip (inward translocation) of PS, higher PS exposure, and higher cholesterol efflux from cells by both ABCA1-dependent and ABCA1-independent mechanisms. Mechanistically, sphingomyelin was connected to PS translocation in cell-free liposome studies that showed that sphingomyelin increased the rate of spontaneous PS flipping. Depletion of sphingomyelin in stably transfected HEK293 cells expressing the Tangier disease W590S mutant ABCA1 isoform rescued the defect in PS exposure and restored cholesterol efflux to apoAI. Liposome studies showed that PS directly increased cholesterol accessibility to extraction by cyclodextrin, providing the mechanistic link between cell surface PS and cholesterol efflux. We conclude that altered plasma membrane environment conferred by depleting sphingomyelin impairs PS flip and promotes cholesterol efflux in ABCA1-dependent and -independent manners.
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107 As previously observed (15, 24-26), cholesterol efflux to apoAI from cells expressing either the W590S (PS translocation deficient) or C1477R (apoAI binding deficient) ABCA1 mutant isoforms was partially, but not completely impaired compared with the WT isoform (p b0d; 0.001 compared with control HEK and WT ABCA1 by ANOVA post test).
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ABCA1 p.Cys1477Arg 24220029:107:135
status: NEW109 Thus, myriocin treatment could overcome much of the impaired cholesterol efflux activity of the W590S Abca1 mutation, although not greatly improving efflux from the C1477R mutation.
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ABCA1 p.Cys1477Arg 24220029:109:165
status: NEW128 Non-transfected HEK293 cells along with HEK cells transfected with WT-Abca1-GFP, W590S-Abca1-GFP, or C1477R-Abca1-GFP isoforms were incubated with radiolabeled cholesterol and subsequently chased with apoAI (5 òe;g/ml) for 6 h.
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ABCA1 p.Cys1477Arg 24220029:128:101
status: NEW[hide] Premature atherosclerosis, extremely low HDL-chole... Int J Cardiol. 2014 Nov 15;177(1):e19-21. doi: 10.1016/j.ijcard.2014.07.172. Epub 2014 Aug 4. Koopal C, Visseren FL, Kastelein JJ, Westerink J
Premature atherosclerosis, extremely low HDL-cholesterol and concurrent defects in APOA1 and ABCA1 genes: a family case report.
Int J Cardiol. 2014 Nov 15;177(1):e19-21. doi: 10.1016/j.ijcard.2014.07.172. Epub 2014 Aug 4., [PMID:25127959]
Abstract [show]
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18 The mutations were an AAG (lysine) deletion in exon 4 (c.391_393deletion; p.Lys131del) of the APOA1 gene and an ABCA1 missense mutation (c.4429TNC; p.C1477R) in exon 31.
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ABCA1 p.Cys1477Arg 25127959:18:150
status: NEW46 5 - - CAC-score (MESA %) 3663 (99) 59 (99) - 0 (0) - - - 33 (95) 0 (0) - - 6. HDL-c 0.74 mmol/L CAC 0 9. HDL-c 1.18 mmol/L 3. HDL-c 0.65 mmol/L AAA + MI 4. HDL-c 0.65 mmol/L 5. HDL-c 1.00 mmol/L 7. HDL-c 1.12 mmol/L CAC 33 1. HDL-c <0.20 mmol/L CAC 3663, MI 2. HDL-c 0.28 mmol/L CAC 59 8. HDL-c 1.07 mmol/L CAC 0 10. HDL-c 0.92 mmol/L 11. HDL-c 1.27 mmol/L 78 yrs 77 yrs 52 yrs 51 yrs 51 yrs 49 yrs 45 yrs 43 yrs 25 yrs 22 yrs 20 yrs MI = myocardial infarction AAA = abdominal aortic aneurysm Male with APOA1 mutation (p.Lys131del) Female with ABCA1 mutation (p.C1477R) CAC = coronary artery calcium Male with ABCA1 mutation (p.C1477R) Female with APOA1 mutation (p.Lys131del) Fig. 1.
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ABCA1 p.Cys1477Arg 25127959:46:562
status: NEWX
ABCA1 p.Cys1477Arg 25127959:46:628
status: NEW[hide] Myocardial infarction in a 36-year-old man with co... J Clin Lipidol. 2015 May-Jun;9(3):396-9. doi: 10.1016/j.jacl.2015.01.006. Epub 2015 Jan 28. van Capelleveen JC, Kootte RS, Hovingh GK, Bochem AE
Myocardial infarction in a 36-year-old man with combined ABCA1 and APOA-1 deficiency.
J Clin Lipidol. 2015 May-Jun;9(3):396-9. doi: 10.1016/j.jacl.2015.01.006. Epub 2015 Jan 28., [PMID:26073400]
Abstract [show]
In this report, we present a patient who suffered from a myocardial infarction at an extremely young age. The only remarkable finding in the risk factor workup was a near undetectable high-density lipoprotein (HDL)-cholesterol plasma level (0.09 mmol/L). Genetic analysis of key genes involved in HDL metabolism resulted in the discovery of 2 very rare mutations in the ABCA1 and APOA1 genes. We discuss the effects of these mutations on HDL metabolism and reverse cholesterol transport and interpret these findings in relation to the extensive atherosclerosis at a very young age in this patient.
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57 Many case studies in these patients have reported premature atherosclerosis, indicating a clear association of HDL-C deficiency with CVD risk.14,15 Although the extreme rarity of the genetic combination and possible referral bias does preclude us from drawing firm conclusions regarding the etiology of atherosclerosis in this patient, we feel that the low HDL-C and corresponding impairment in RCT is an important factor.14,15 The genetic basis of the low HDL-C in one of the recently described families with HDL-C deficiency16 was in fact, a combination of ABCA1 (p.Cys1477Arg) and APOA1 (p.Lys130del) mutations, which has also been shown to be well characterized for the impact on RCT.8,9,17 Conclusion In this report, we present a patient with extremely low HDL-C levels based on a unique combined deficiency of ABCA1 and apoA-1.
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ABCA1 p.Cys1477Arg 26073400:57:568
status: NEW[hide] LXRs link metabolism to inflammation through Abca1... Elife. 2015 Jul 14;4:e08009. doi: 10.7554/eLife.08009. Ito A, Hong C, Rong X, Zhu X, Tarling EJ, Hedde PN, Gratton E, Parks J, Tontonoz P
LXRs link metabolism to inflammation through Abca1-dependent regulation of membrane composition and TLR signaling.
Elife. 2015 Jul 14;4:e08009. doi: 10.7554/eLife.08009., [PMID:26173179]
Abstract [show]
The liver X receptors (LXRs) are transcriptional regulators of lipid homeostasis that also have potent anti-inflammatory effects. The molecular basis for their anti-inflammatory effects is incompletely understood, but has been proposed to involve the indirect tethering of LXRs to inflammatory gene promoters. Here we demonstrate that the ability of LXRs to repress inflammatory gene expression in cells and mice derives primarily from their ability to regulate lipid metabolism through transcriptional activation and can occur in the absence of SUMOylation. Moreover, we identify the putative lipid transporter Abca1 as a critical mediator of LXR's anti-inflammatory effects. Activation of LXR inhibits signaling from TLRs 2, 4 and 9 to their downstream NF-kappaB and MAPK effectors through Abca1-dependent changes in membrane lipid organization that disrupt the recruitment of MyD88 and TRAF6. These data suggest that a common mechanism-direct transcriptional activation-underlies the dual biological functions of LXRs in metabolism and inflammation.
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81 Selected genes that are annotated with the 'Immune system process` GO Figure 2. continued on next page To further examine the function of Abca1 was critical for inflammatory repression, we reconstituted iBMDM from myeloid-specific Abca1-/- mice with wild-type Abca1 or two different Abca1 point mutants that lacks cholesterol efflux ability, N935S and C1477R (Singaraja et al., 2006; Kannenberg et al., 2013).
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ABCA1 p.Cys1477Arg 26173179:81:353
status: NEW82 When Abca1-deficient cells were reconstituted with wild-type Abca1, inflammatory gene expression was repressed by LXR activation; however, this effect was lost in cells expressing the N935S or C1477R mutants (Figure 4C).
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ABCA1 p.Cys1477Arg 26173179:82:193
status: NEW