ABCMdb

ABCA1 p.Asn935Ser

ClinVar:	c.2804A>G , p.Asn935Ser D , Pathogenic c.2803A>C , p.Asn935His D , Pathogenic
Predicted by SNAP2:	A: D (75%), C: D (80%), D: D (85%), E: D (91%), F: D (91%), G: D (85%), H: D (75%), I: D (85%), K: D (85%), L: D (91%), M: D (85%), P: D (85%), Q: D (80%), R: D (91%), S: D (75%), T: D (75%), V: D (85%), W: D (91%), Y: D (85%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: D, K: D, L: D, M: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D,

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[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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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. Login to comment
169 Effects of some ABCA1 mutations described here are also consistent with previous in vitro cellular efflux studies; for example, the highly expressive ABCA1 mutations R587W, Q597R, N935S, and M1091T cause ~10-25% of wild-type efflux in vitro, while the less expressive mutations K776N and T929I cause 62 and 80% efflux, respectively [35-37]. Login to comment

[hide] The role of ATP-binding cassette transporter A1 in... Biochim Biophys Acta. 2010 Aug;1801(8):824-30. Epub 2010 Feb 24. Koldamova R, Fitz NF, Lefterov I
The role of ATP-binding cassette transporter A1 in Alzheimer's disease and neurodegeneration.
Biochim Biophys Acta. 2010 Aug;1801(8):824-30. Epub 2010 Feb 24., [PMID:20188211]

Abstract [show]
ATP-binding cassette transporter A1 - ABCA1, is the most extensively studied transporter in human pathology. ABCA1 became a primary subject of research in many academic and pharmaceutical laboratories immediately after the discovery that mutations at the gene locus cause severe familial High Density Lipoprotein (HDL) deficiency and, in the homozygous form - Tangier disease. The protein is the major regulator of intracellular cholesterol efflux which is the initial and essential step in the biogenesis and formation of nascent HDL particles. The transcriptional regulation of ABCA1 by nuclear Liver X Receptors (LXR) provided a starting point for drug discovery and development of synthetic LXR ligands/ABCA1 activators for treatment of arteriosclerosis. A series of reports that revealed the role of ABCA1 in Abeta deposition and clearance, as well as the possibility for association of some ABCA1 genetic variants with risk for Alzheimer's disease (AD) brought a new dimension to ABCA1 research. The LXR-ABCA1-APOE regulatory axis is now considered a promising therapeutic target in AD, which includes the only proven risk factor for AD - APOE, at two distinct levels - transcriptional regulation by LXR, and ABCA1 controlled lipidation which can influence Abeta aggregation and amyloid clearance. This review will summarize the results of research on ABCA1, particularly related to AD and neurodegeneration.

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93 N935S mutation was identified in patient with extremely low levels of HDL, but without accelerated development of premature atherosclerosis and with signs of severe dementia and amyloid depositions in the brain at age of 60 [35]. Login to comment

[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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44 In patients defined by missense mutations on both alleles, 2 clear groups were observed: those showing negligible plasma HDL-C (R587W, N935S, N1800H), and those with HDL-C levels that were Ϸ10% of HDL-C in controls (A255T). Login to comment
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). Login to comment
48 Six mutants, R587W, Q597R, ⌬L693, N935S, N1800H, and R2081W, showed no localization at the plasma membrane and instead accumulated intracellularly (Figure 2A), indicating that these mutations severely affect ABCA1 function by preventing its migration to the plasma membrane, thus diminishing its ability to efflux lipids and generate HDL. Login to comment
68 All 6 mutants showing no plasma membrane localization elicited significantly reduced cell surface ApoA-I binding (R587W, 33.0Ϯ8.9%, nϭ3, Pϭ0.006; Q597R, 17.4Ϯ14.0%, nϭ3, Pϭ0.009; ⌬L693, 32.6Ϯ10.6%, nϭ3, Pϭ0.008; N935S, 26.4Ϯ37.5%, nϭ3, Pϭ0.01; N1800H, 36.9Ϯ15.5%, nϭ3, Pϭ0.01; R2081W, 34.6Ϯ16.6%, nϭ3, Pϭ0.02) (Figure 3A), confirming that cell surface localization of ABCA1 is essential to elicit ApoA-I binding. Login to comment
78 Wild-type ABCA1 was localized intracellularly and at the plasma membrane. R587W, Q597R, ⌬L693, N935S, N1800H, and R2081W were only localized intracellularly. Login to comment
81 Wt ABCA1 shows both EndoH resistant and sensitive bands, indicating localization at the ER and plasma membrane. R587W, Q597R, ⌬L693, and N935S show only the lower EndoH sensitive band, indicating ER retention. Login to comment
95 Near-Complete Absence of Plasma HDL-C in Homozygotes for Mutations in ABCA1 Implies the Presence of Null Alleles of ABCA1 Patients homozygous for R587W mutations showed 6.3% of normal HDL-C levels, those with N935S showed 2.62%, and those with N1800H showed 3.4% of normal plasma HDL-C levels. Login to comment

[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. Login to comment

[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. Login to comment
75 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. Login to comment
93 harvard.edu/pph) is a Web-based program used to predict allele function based on homology and three-dimensional structural models where available [15], and it predicts alleles as being ''probably damaging,`` ''possibly damaging,`` or ''benign.`` In the dataset of variants for which we assessed cholesterol efflux, the predictions made by PANTHER and PolyPhen were significantly different for two mutations: N935S and P2150L. Login to comment
94 PolyPhen predicted N935S to be benign, while PANTHER predicted it to be deleterious. Login to comment

[hide] Screening for functional sequence variations and m... Atherosclerosis. 2004 Aug;175(2):269-79. Probst MC, Thumann H, Aslanidis C, Langmann T, Buechler C, Patsch W, Baralle FE, Dallinga-Thie GM, Geisel J, Keller C, Menys VC, Schmitz G
Screening for functional sequence variations and mutations in ABCA1.
Atherosclerosis. 2004 Aug;175(2):269-79., [PMID:15262183]

Abstract [show]
Mutations in the ATP-binding cassette 1 transporter gene (ABCA1) are responsible for the genetic HDL-deficiency syndromes, which are characterized by severely diminished plasma HDL-C levels and a predisposition to cardiovascular disease and splenomegaly. The ABCA1 gene contains 50 exons and codes for a 2261-amino acid long membrane protein that facilitates phospholipid and cholesterol transport. Several mutations have been identified so far as responsible either for Tangier disease or for reduced HDL levels. We have selectively looked for additional polymorphisms in functionally relevant regions of the gene in cohorts constituted of individuals with altered HDL levels as well as healthy blood donors and octogenarians, and screened for mutations in the complete coding region of selected individuals with extremely aberrant HDL levels. In the promoter region, which is important for regulation of gene expression, we have identified several polymorphisms including one VNTR polymorphism, located at a putative ZNF202 binding site, which displayed different binding of ZNF202 in an electromobility shift assay. Three novel SNPs were discovered in the promoter region (G1047C, C1152T and C1440T). The prevalence of exchange G1047C (G-395C) was found significantly increased in probands with low HDL compared to probands with high HDL. Exchanges C1152T (C-290T) and C1440T (C-7T) were significantly more frequent in the cohort with low HDL compared to healthy blood donors and octogenarians. In the C-terminal part of ABCA1, known to interact with other proteins, two novel sequence variations (F2163S and V2244I) have been found in one phenotype related to cardiovascular disease, but none in the aforementioned cohorts. In one individual with extremely high HDL levels, the V771M polymorphism was found in a homozygous state. In patients with HDL deficiency, three novel mutations have been identified (W590L, W840R and R1068C). To facilitate further research in ABCA1 sequence variations and expand our understanding of their effects, we are introducing a webpage archive (http://www.abca1-mutants.all.at) containing all sequence variations reported in ABCA1 so far. This webpage provides a more recent and detailed summary of sequence variations and mutations in ABCA1 than existing databases and should also be of interest for molecular diagnosis of ABCA1-related HDL deficiency.

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184 We found that 451 (94.4%) out of 478 successfully genotyped individuals were wild-types, only 27 (5.6%) were heterozygous V/M771 and no homozygous M771 individual was found. Sequencing of the complete ABCA1 gene of the 50-year-old female with 2 mg/dl HDL (patient B) showed that she was heterozygous for A107009G (N935S), a known Tangier mutation [7], and also heterozygous for the novel mutation T103822A, which results in the amino acid exchange W840R. Login to comment

[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. Login to comment
232 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. Login to comment

[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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83 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. Login to comment
113 This could result from 2 null alleles for ABCA1 preventing export of the protein to the plasma membrane or from ABCA1 at the plasma membrane harboring mutations in residues crucial for its function. Indeed, patients harboring the mutations 635X, N935S, N1800H, 1851X, and 2203X and the large C-terminal deletion all have below 1% of HDL-C levels of age-and sex-matched controls from the Lipid Research Clinic population. Login to comment
75 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. Login to comment
105 This could result from 2 null alleles for ABCA1 preventing export of the protein to the plasma membrane or from ABCA1 at the plasma membrane harboring mutations in residues crucial for its function. Indeed, patients harboring the mutations 635X, N935S, N1800H, 1851X, and 2203X and the large C-terminal deletion all have below 1% of HDL-C levels of age-and sex-matched controls from the Lipid Research Clinic population. Login to comment

[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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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.] Login to comment

[hide] Double deletions and missense mutations in the fir... J Hum Genet. 2002;47(6):325-9. Guo Z, Inazu A, Yu W, Suzumura T, Okamoto M, Nohara A, Higashikata T, Sano R, Wakasugi K, Hayakawa T, Yoshida K, Suehiro T, Schmitz G, Mabuchi H
Double deletions and missense mutations in the first nucleotide-binding fold of the ATP-binding cassette transporter A1 ( ABCA1) gene in Japanese patients with Tangier disease.
J Hum Genet. 2002;47(6):325-9., [PMID:12111381]

Abstract [show]
Tangier disease (TD) is a rare autosomal recessive disease characterized by plasma high-density lipoprotein deficiency caused by an ATP-binding cassette transporter A1 ( ABCA1) gene mutation. We describe three different mutations in Japanese patients with TD. The first patient was homozygous for double deletions of 1221 bp between intron 12 and 14 and 19.9 kb between intron 16 and 31. The breakpoint sequence analyses suggest that it is a simultaneous event caused by double-loop formation through multiple Alu. The second patient was homozygous for a novel mutation of A3198C in exon 19, resulting in Asn935His. The third patient was homozygous for A3199G of exon 19 that leads to Asn935Ser, which is the same mutation found in German and Spanish families. Both Asn mutations involved Walker A motif of the first nucleotide-binding fold.

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5 The third patient was homozygous for A3199G of exon 19 that leads to Asn935Ser, which is the same mutation found in German and Spanish families. Login to comment
65 Case 3, homozygous for the AϾG mutation at 3199 (Asn935Ser), as shown in the left panel, was confirmed by PCR-RFLP using DdeI digestion on 10% polyacrylamide gel in the right panel. Login to comment
68 The mutation in case 3 was A3199G of exon 19, resulting in a change of Asn935Ser. Login to comment
77 The Asn935Ser mutation in the third case showed atypical clinical signs, such as an obsessive-compulsive disorder and lower intelligence, in addition to the typical features. Login to comment
78 The mutation of Asn935Ser in the third patient was the same as that of German and Spanish families (Bodzioch et al. 1999; Utech et al. 2001), which suggests that it is a recurrent mutation and that they did not have cognitive disorders. Login to comment

[hide] Accumulation of cardiolipin and lysocardiolipin in... FEBS Lett. 2001 Jul 6;500(3):157-62. Fobker M, Voss R, Reinecke H, Crone C, Assmann G, Walter M
Accumulation of cardiolipin and lysocardiolipin in fibroblasts from Tangier disease subjects.
FEBS Lett. 2001 Jul 6;500(3):157-62., [PMID:11445077]

Abstract [show]
Tangier disease (TD) is an inherited disorder of lipid metabolism characterized by very low high density lipoprotein (HDL) plasma levels, cellular cholesteryl ester accumulation and reduced cholesterol excretion in response to HDL apolipoproteins. Molecular defects in the ATP binding cassette transporter 1 (ABCA1) have recently been identified as the cause of TD. ABCA1 plays a key role in the translocation of cholesterol across the plasma membrane, and defective ABCA1 causes cholesterol storage in TD cells. Not only cholesterol efflux, but also phospholipid efflux was shown to be impaired in TD cells. By use of thin layer chromatography, high performance liquid chromatography and time-of-flight secondary ion mass spectrometry, we characterized the cellular phospholipid content in fibroblasts from three homozygous TD patients. The cellular content of the major phospholipids was not found to be significantly altered in TD fibroblasts. However, the two phospholipids cardiolipin and lysocardiolipin, which make up minute amounts in normal cells, were at least 3-5-fold enriched in fibroblasts from TD subjects. A structurally closely related phospholipid (lysobisphosphatidic acid) has recently been shown to be enriched in Niemann-Pick type C, another lipid storage disorder. Altogether these data may indicate that the role of these phospholipids is a regulatory one rather than that of a bulk mediator of cholesterol solubilization in sterol trafficking and efflux.

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34 Patients TD1 and TD3 are characterized by an asparagine to serine mutation at position 935 of ABCA1 [25]. Login to comment

[hide] Accumulation of RhoA, RhoB, RhoG, and Rac1 in fibr... Biochem Biophys Res Commun. 2001 Jan 12;280(1):229-36. Utech M, Hobbel G, Rust S, Reinecke H, Assmann G, Walter M
Accumulation of RhoA, RhoB, RhoG, and Rac1 in fibroblasts from Tangier disease subjects suggests a regulatory role of Rho family proteins in cholesterol efflux.
Biochem Biophys Res Commun. 2001 Jan 12;280(1):229-36., [PMID:11162504]

Abstract [show]
Tangier disease (TD) is an inherited disorder of lipid metabolism characterized by very low high density lipoprotein (HDL) plasma levels, cellular cholesteryl ester accumulation and reduced cholesterol excretion in response to HDL apolipoproteins. Molecular defects in the ATP binding cassette transporter 1 (ABCA1) have recently been identified as the cause of TD. ABCA1 plays a key role in the translocation of cholesterol across the plasma membrane, and defective ABCA1 causes cholesterol storage in TD cells. However, the exact relationship of many of the biochemical and morphological abnormalities in TD to ABCA1 is unknown. Since small GTP-binding proteins are important regulators of many cellular functions, we characterized these proteins in normal and TD fibroblasts using the [alpha-32P]GTP overlay technique and Western blotting of SDS and isoelectric focusing gels. Our results indicate that GTP-binding proteins of the Rho family (RhoA, RhoB, RhoG, Rac-1) are enriched in fibroblasts from TD patients. The accumulation of small G proteins may have potential implications for the TD phenotype and the regulation of cholesterol excretion in TD cells.

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134 Homozygous point mutation AAT-AGT (asparagine- serine, N935S). Login to comment
133 Homozygous point mutation AAT-AGT (asparagine- serine, N935S). Login to comment

[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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69 Subjects were carriers of the following mutations: c.6401+2T.C, p.Ser930Phe, p.Ser824Leu, p.Arg587Trp, p.Thr929Ile, p.Asn935Ser, c.3535+1G.C, p.Asp571Gly, p.Asn1800his, p.Leu1056Pro, p.Gln1038Ter, c.1195-1G.C, p.Arg579Gln, and p.Phe1760Valfs*21. Login to comment
79 The efflux capacity of the remaining nine mutations: p.Asn935Ser, c.3535+1G.C, p.Ser824Leu, p.Ser930Phe, p.Gln1038Ter, c.1195-1G.C, c.6401+2T.C, p.Asp571Gly, and p.Arg579Gln are listed in Figure 1. Login to comment

[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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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. Login to comment
67 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. Login to comment
208 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). Login to comment
229 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). Login to comment
232 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. Login to comment
211 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). Login to comment
64 Mutations introduced by overlap extension PCR using Pfu AD DNA polymerase in ABCA1 included S100C, W590S, F593L, N935S, T929I, C1477R, T1512M, R2081W, and P2150L. Login to comment
206 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). Login to comment
227 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). Login to comment

[hide] Characterization of cholesterol homeostasis in tel... J Biol Chem. 2013 Dec 27;288(52):36936-47. doi: 10.1074/jbc.M113.500256. Epub 2013 Nov 6. Kannenberg F, Gorzelniak K, Jager K, Fobker M, Rust S, Repa J, Roth M, Bjorkhem I, Walter M
Characterization of cholesterol homeostasis in telomerase-immortalized Tangier disease fibroblasts reveals marked phenotype variability.
J Biol Chem. 2013 Dec 27;288(52):36936-47. doi: 10.1074/jbc.M113.500256. Epub 2013 Nov 6., [PMID:24196952]

Abstract [show]
We compared the consequences of an ABCA1 mutation that produced an apparent lack of atherosclerosis (Tangier family 1, N935S) with an ABCA1 mutation with functional ABCA1 knockout that was associated with severe atherosclerosis (Tangier family 2, Leu(548):Leu(575)-End), using primary and telomerase-immortalized fibroblasts. Telomerase-immortalized Tangier fibroblasts of family 1 (TT1) showed 30% residual cholesterol efflux capacity in response to apolipoprotein A-I, whereas telomerase-immortalized Tangier fibroblasts of family 2 (TT2) showed only 20%. However, there were a number of secondary differences that were often stronger and may help to explain the more rapid development of atherosclerosis in family 2. First, the total cellular cholesterol content increase was 2-3-fold and 3-5-fold in TT1 and TT2 cells, respectively. The corresponding increase in esterified cholesterol concentration was 10- and 40-fold, respectively. Second, 24-, 25-, and 27-hydroxycholesterol concentrations were moderately increased in TT1 cells, but were increased as much as 200-fold in TT2 cells. Third, cholesterol biosynthesis was moderately decreased in TT1 cells, but was markedly decreased in TT2 cells. Fourth, potentially atheroprotective LXR-dependent SREBP1c signaling was normal in TT1, but was rather suppressed in TT2 cells. Cultivated primary Tangier fibroblasts were characterized by premature aging in culture and were associated with less obvious biochemical differences. In summary, these results may help to understand the differential atherosclerotic susceptibility in Tangier disease and further demonstrate the usefulness of telomerase-immortalized cells in studying this cellular phenotype. The data support the contention that side chain-oxidized oxysterols are strong suppressors of cholesterol biosynthesis under specific pathological conditions in humans.

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4 We compared the consequences of an ABCA1 mutation that produced an apparent lack of atherosclerosis (Tangier family 1, N935S) with an ABCA1 mutation with functional ABCA1 knockout that was associated with severe atherosclerosis (Tangier family 2, Leu548 :Leu575 -End), using primary and telomerase-immortalized fibroblasts. Login to comment

[hide] ATP-binding cassette transporter A1: from metaboli... Neurobiol Dis. 2014 Dec;72 Pt A:13-21. doi: 10.1016/j.nbd.2014.05.007. Epub 2014 May 17. Koldamova R, Fitz NF, Lefterov I
ATP-binding cassette transporter A1: from metabolism to neurodegeneration.
Neurobiol Dis. 2014 Dec;72 Pt A:13-21. doi: 10.1016/j.nbd.2014.05.007. Epub 2014 May 17., [PMID:24844148]

Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) mediates cholesterol efflux to lipid-free apolipoprotein A-I (apoA-I) and apolipoprotein E (apoE). ABCA1 is an essential regulator of high density lipoproteins (HDL) and reverse cholesterol transport - a role that determines its importance for atherosclerosis. Over the last 10 years studies have provided convincing evidence that ABCA1, via its control of apoE lipidation, also has a role in Alzheimer's disease (AD). A series of reports have revealed a significant impact of ABCA1 on Abeta deposition and clearance in AD model mice, as well as an association of common and rare ABCA1 gene variants with the risk for AD. Since APOE is the major genetic risk factor for late onset AD, the regulation of apoE level or its functionality by ABCA1 may prove significant for AD pathogenesis. ABCA1 is transcriptionally regulated by Liver X Receptors (LXR) and Retinoic X Receptors (RXR) which provides a starting point for drug discovery and development of synthetic LXR and RXR agonists for treatment of metabolic and neurodegenerative disorders. This review summarizes the recent results of research on ABCA1, particularly relevant to atherosclerosis and AD.

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999 N935S mutation was identified in a patient with extremely low levels of HDL, but without accelerated development of premature atherosclerosis and with signs of severe dementia and amyloid depositions in the brain at age of 60 (Walter et al., 1994a,b). Login to comment

[hide] Increased Systemic and Plaque Inflammation in ABCA... Arterioscler Thromb Vasc Biol. 2015 Jul;35(7):1663-9. doi: 10.1161/ATVBAHA.114.304959. Epub 2015 Feb 19. Bochem AE, van der Valk FM, Tolani S, Stroes ES, Westerterp M, Tall AR
Increased Systemic and Plaque Inflammation in ABCA1 Mutation Carriers With Attenuation by Statins.
Arterioscler Thromb Vasc Biol. 2015 Jul;35(7):1663-9. doi: 10.1161/ATVBAHA.114.304959. Epub 2015 Feb 19., [PMID:26109739]

Abstract [show]
OBJECTIVE: We previously demonstrated that subjects with functional ATP-binding cassette (ABC) A1 mutations have increased atherosclerosis, which has been attributed to the role of ABCA1 in reverse cholesterol transport. More recently, a proinflammatory effect of Abca1 deficiency was shown in mice, potentially contributing to atherogenesis. In this study, we investigated whether ABCA1 deficiency was associated with proinflammatory changes in humans. APPROACH AND RESULTS: Thirty-one heterozygous, 5 homozygous ABCA1 mutation carriers, and 21 matched controls were studied. (18)Fluorodeoxyglucose positron emission tomography with computed tomographic scanning was performed in a subset of carriers and controls to assess arterial wall inflammation (target:background ratio). Heterozygous ABCA1 mutation carriers had a 20% higher target:background ratio than in controls (target:background ratio; P=0.008). In carriers using statins (n=7), target:background ratio was 21% reduced than in nonstatin users (n=7; P=0.03). We then measured plasma cytokine levels. Tumor necrosis factor alpha, monocyte chemoattractant protein-1, and interleukin-6 levels were increased in heterozygous and homozygous ABCA1 mutation carriers. We isolated monocytes from carriers and controls and measured inflammatory gene expression. Only TNFalpha mRNA was increased in monocytes from heterozygous ABCA1 mutation carriers. Additional studies in THP-1 macrophages showed that both ABCA1 deficiency and lipoprotein-deficient plasma from ABCA1 mutation carriers increased inflammatory gene expression. CONCLUSIONS: Our data suggest a proinflammatory state in ABCA1 mutation carriers as reflected by an increased positron emission tomography-MRI signal in nonstatin using subjects, and increased circulating cytokines. The increased inflammation in ABCA1 mutation carriers seems to be attenuated by statins.

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28 Homozygous and compoundheterozygoussubjectshadTangierDisease.Subjects were carriers of the following mutations: p.Leu1056Pro, c.3535+1G>C, c.6401+2T>C, p.Asn1800his, p.Ser930Phe, p.Phe1760Valfs*21, p.Ser824Leu, p.Gln1038Ter, p.Thr929Ile, p.Arg587Trp, p.Asn935Ser, and p.Arg579Gln. Login to comment

[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). Login to comment
82 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). Login to comment
149 (C) Immortalized bone marrow-derived macrophages from Abca1-/- mice reconstituted with wild-type Abca1, N935S mutant, C1447R mutant or mock control were pretreated with GW3965 (1 bc;M) overnight, followed by stimulation with LPS (10 ng/ml) for 4 hr. Gene expression was analyzed by real-time PCR. Login to comment