ABCMdb

ABCA1 p.Ala937Val

ClinVar:	c.2810C>T , p.Ala937Val D , Pathogenic
Predicted by SNAP2:	C: D (53%), D: D (91%), E: D (85%), F: D (80%), G: D (75%), H: D (80%), I: D (66%), K: D (85%), L: D (80%), M: D (75%), N: D (80%), P: D (80%), Q: D (80%), R: D (85%), S: D (59%), T: D (66%), V: D (71%), W: D (80%), Y: D (80%),
Predicted by PROVEAN:	C: 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,

[switch to compact view]
Comments [show]

None has been submitted yet.

Publications
[hide] ABCA1 increases extracellular ATP to mediate chole... Am J Physiol Cell Physiol. 2011 Oct;301(4):C886-94. Epub 2011 Jun 22. Lee JY, Karwatsky J, Ma L, Zha X
ABCA1 increases extracellular ATP to mediate cholesterol efflux to ApoA-I.
Am J Physiol Cell Physiol. 2011 Oct;301(4):C886-94. Epub 2011 Jun 22., [PMID:21697542]

Abstract [show]
ATP-binding cassette protein A1 (ABCA1) is a key plasma membrane protein required for the efflux of cellular cholesterol to extracellular acceptors, particularly to apolipoprotein A-I (apoA-I). This process is essential to maintain cholesterol homeostasis in the body. The detailed molecular mechanisms, however, are still insufficiently understood. Also, the molecular identity of ABCA1, i.e., channel, pump, or flippase, remains unknown. In this study we analyzed extracellular ATP levels in the medium of ABCA1-expressing BHK cells and RAW macrophages and compared them to the medium of nonexpressing cells. We found that extracellular ATP concentrations are significantly elevated when cells express ABCA1. Importantly, a dysfunctional ABCA1 mutant (A937V), when expressed similarly as wild-type ABCA1, is unable to raise extracellular ATP concentration, which suggests a casual relationship between functional ABCA1 and elevated extracellular ATP. To explore the physiological role of extracellular ATP, we analyzed ABCA1-mediated cholesterol efflux under conditions where extracellular ATP levels were modulated. We found that increasing extracellular ATP within the physiological range, i.e., <muM, promotes cholesterol efflux to apoA-I. On the other hand, removing extracellular ATP, either by adding apyrase to the medium or by expressing a plasma membrane-bound ectonucleotidase, CD39, abolishes cholesterol efflux to apoA-I. On the basis of these results, we conclude that, through direct or indirect mechanisms, ABCA1 functions to raise ATP levels in the medium. This elevated extracellular ATP is required for ABCA1-mediated cholesterol efflux to apoA-I.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
11 Importantly, a dysfunctional ABCA1 mutant (A937V), when expressed similarly as wild-type ABCA1, is unable to raise extracellular ATP concentration, which suggests a casual relationship between functional ABCA1 and elevated extracellular ATP. Login to comment
61 BHK-A937V cells contain an ABCA1 gene insert carrying a single nucleotide A to V mutation. Login to comment
116 RESULTS To determine whether functional ABCA1 influences extracellular ATP levels, we analyzed ATP concentrations in the medium of BHK-ABCA1 cells and compared them with the medium collected from Mock-BHK or BHK-A937V cells. Login to comment
118 Specifically, BHK-ABCA1 cells carry the wild-type (WT) ABCA1 insert, whereas BHK-A937V cells carry an alanine to valine mutant within the first nucleotide-binding domain of the transporter (34). Login to comment
120 Once induced with mifepristone overnight, BHK-ABCA1 and BHK-A937V cells express ABCA1 or ABCA1A937V , respectively, at comparable levels but not BHK-Mock cells (Fig. 1A, right 3 lanes). Login to comment
145 Most interestingly, mifepristone does not alter the extracellular ATP concentration in BHK-A937V cells (Fig. 1C), although ABCA1A937V is similarly expressed as WT ABCA1. Login to comment
7 Importantly, a dysfunctional ABCA1 mutant (A937V), when expressed similarly as wild-type ABCA1, is unable to raise extracellular ATP concentration, which suggests a casual relationship between functional ABCA1 and elevated extracellular ATP. Login to comment
58 BHK-A937V cells contain an ABCA1 gene insert carrying a single nucleotide A to V mutation. Login to comment
112 RESULTS To determine whether functional ABCA1 influences extracellular ATP levels, we analyzed ATP concentrations in the medium of BHK-ABCA1 cells and compared them with the medium collected from Mock-BHK or BHK-A937V cells. Login to comment
114 Specifically, BHK-ABCA1 cells carry the wild-type (WT) ABCA1 insert, whereas BHK-A937V cells carry an alanine to valine mutant within the first nucleotide-binding domain of the transporter (34). Login to comment
140 Most interestingly, mifepristone does not alter the extracellular ATP concentration in BHK-A937V cells (Fig. 1C), although ABCA1A937V is similarly expressed as WT ABCA1. Login to comment

[hide] ABCA1-mediated cholesterol efflux generates microp... J Lipid Res. 2009 Mar;50(3):456-66. Epub 2008 Oct 21. Nandi S, Ma L, Denis M, Karwatsky J, Li Z, Jiang XC, Zha X
ABCA1-mediated cholesterol efflux generates microparticles in addition to HDL through processes governed by membrane rigidity.
J Lipid Res. 2009 Mar;50(3):456-66. Epub 2008 Oct 21., [PMID:18941142]

Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) mediates cholesterol efflux to lipid-poor apolipoprotein A-I (apoA-I) and generates HDL. Here, we demonstrate that ABCA1 also directly mediates the production of apoA-I free microparticles. In baby hamster kidney (BHK) cells and RAW macrophages, ABCA1 expression led to lipid efflux in the absence of apoA-I and released large microparticles devoid of apoB and apoE. We provide evidence that these microparticles are an integral component of the classical cholesterol efflux pathway when apoA-I is present and accounted for approximately 30% of the total cholesterol released to the medium. Furthermore, microparticle release required similar ABCA1 activities as was required for HDL production. For instance, a nucleotide binding domain mutation in ABCA1 (A937V) that impaired HDL generation also abolished microparticle release. Similarly, inhibition of protein kinase A (PKA) prevented the release of both types of particles. Interestingly, physical modulation of membrane dynamics affected HDL and microparticle production, rigidifying the plasma membrane with wheat germ agglutinin inhibited HDL and microparticle release, whereas increasing the fluidity promoted the production of these particles. Given the established role of ABCA1 in expending nonraft or more fluid-like membrane domains, our results suggest that both HDL and microparticle release is favored by a more fluid plasma membrane. We speculate that ABCA1 enhances the dynamic movement of the plasma membrane, which is required for apoA-I lipidation and microparticle formation.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
5 For instance, a nucleotide binding domain mutation in ABCA1 (A937V) that impaired HDL generation also abolished microparticle release. Login to comment
151 A: 3 H-cholesterol labeled BHK-mock, ABCA1, ABCA1-A937V cells were induced for 20 h and incubated with DMEM without apoA-I for 4 h. B: 3 H-cholesterol labeled BHK-mock and ABCA1 were induced and incubated with DMEM with or without 50 mM PKI. Login to comment

[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.

Comments [show]

None has been submitted yet.

Sentences [show]
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). Login to comment
50 We also generated an artificial mutation in the Walker A motif of NBD2 (A1950V) that corresponds to the A937V mutation in NBD1. Login to comment
93 The two most severe mutations, which reduced apoA-I-mediated lipid efflux to less than 20% of normal, were located in the first extracellular loop (Q597R) and the ATP binding site (A937V). Login to comment
92 The two most severe mutations, which reduced apoA-I-mediated lipid efflux to less than 20% of normal, were located in the first extracellular loop (Q597R) and the ATP binding site (A937V). Login to comment

[hide] Enhanced apoA-I-dependent cholesterol efflux by AB... J Biol Chem. 2007 May 18;282(20):14868-74. Epub 2007 Apr 3. Nagao K, Takahashi K, Hanada K, Kioka N, Matsuo M, Ueda K
Enhanced apoA-I-dependent cholesterol efflux by ABCA1 from sphingomyelin-deficient Chinese hamster ovary cells.
J Biol Chem. 2007 May 18;282(20):14868-74. Epub 2007 Apr 3., [PMID:17409096]

Abstract [show]
ATP binding cassette protein A1 (ABCA1) plays a major role in cholesterol homeostasis and high density lipoprotein (HDL) metabolism. It is proposed that ABCA1 reorganizes the plasma membrane and generates more loosely packed domains that facilitate apoA-I-dependent cholesterol efflux. In this study, we examined the effects of the cellular sphingomyelin level on HDL formation by ABCA1 by using a Chinese hamster ovary-K1 mutant cell line, LY-A, which has a missense mutation in the ceramide transfer protein CERT. When LY-A cells were cultured in Nutridoma-BO medium and sphingomyelin content was reduced, apoA-I-dependent cholesterol efflux by ABCA1 from LY-A cells increased 1.65-fold compared with that from LY-A/CERT cells stably transfected with human CERT cDNA. Exogenously added sphingomyelin significantly reduced the apoA-I-dependent efflux of cholesterol from LY-A cells, confirming that the decrease in sphingomyelin content in the plasma membrane stimulates cholesterol efflux by ABCA1. The amount of cholesterol available to cold methyl-beta-cyclodextrin (MbetaCD) extraction from LY-A cells was increased by 40% by the expression of ABCA1 and was 1.6-fold higher than that from LY-A/CERT cells. This step in ABCA1 function, making cholesterol available to cold MbetaCD, was independent of apoA-I. These results suggest that the function of ABCA1 could be divided into two steps: (i) a flopping step to move phosphatidylcholine and cholesterol from the inner to outer leaflet of the plasma membrane, where cholesterol becomes available to cold MbetaCD extraction, and (ii) a loading step to load phosphatidylcholine and cholesterol onto apoA-I to generate HDL.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
165 The result by Landry et al., showing that a non-functional ABCA1 with mutation in the ATP-binding domain A937V fails to redistribute cholesterol, may support the latter model. Login to comment
163 The result by Landry et al., showing that a non-functional ABCA1 with mutation in the ATP-binding domain A937V fails to redistribute cholesterol, may support the latter model. Login to comment

[hide] ATP-binding cassette transporter A1 expression dis... J Biol Chem. 2006 Nov 24;281(47):36091-101. Epub 2006 Sep 19. Landry YD, Denis M, Nandi S, Bell S, Vaughan AM, Zha X
ATP-binding cassette transporter A1 expression disrupts raft membrane microdomains through its ATPase-related functions.
J Biol Chem. 2006 Nov 24;281(47):36091-101. Epub 2006 Sep 19., [PMID:16984907]

Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) is known to mediate cholesterol efflux to lipid-poor apolipoprotein A-I. In addition, ABCA1 has been shown to influence functions of the plasma membrane, such as endocytosis and phagocytosis. Here, we report that ABCA1 expression results in a significant redistribution of cholesterol and sphingomyelin from rafts to non-rafts. Caveolin, a raft/caveolae marker also redistributes from punctate caveolae-like structures to the general area of the plasma membrane upon ABCA1 expression. Furthermore, we observed significant reduction of Akt activation in ABCA1-expressing cells, consistent with raft disruption. Cholesterol content in the plasma membrane is, however, not altered. Moreover, we provide evidence that a non-functional ABCA1 with mutation in an ATP-binding domain, A937V, fails to redistribute cholesterol, sphingomyelin, or caveolin. A937V also fails to influence Akt activation. Finally, we show that apolipoprotein A-I preferentially associates with non-raft membranes in ABCA1-expressing cells. Our results thus demonstrate that ABCA1 causes a change in overall lipid packing of the plasma membrane, likely through its ATPase-related functions. Such reorganization by ABCA1 effectively expands the non-raft membrane fractions and, consequentially, pre-conditions cells for cholesterol efflux.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
3 Cholesterol content in the plasma membraneis,however,notaltered.Moreover,weprovideevidence that a non-functional ABCA1 with mutation in an ATP-binding domain,A937V,failstoredistributecholesterol,sphingomyelin,or caveolin. Login to comment
4 A937V also fails to influence Akt activation. Login to comment
110 Cy3-Transferrin Labeling of EYFP-Caveolin-1-transfected Cells-Mock, ABCA1, and A937V mutant cells were grown in 35-mm glass-bottom dishes and transfected with EYFP-caveolin-1 as described above. Login to comment
118 Mock, ABCA1, and A937V mutant cells were grown to 80% confluence in 20-cm plates (five per cell line), and incubated in DMEM with 1 mg/ml BSA and 10 nM mifepristone for 18 h to induce ABCA1 expression. Login to comment
132 Subcellular [3 H]Cholesterol Distribution-Mock, ABCA1, and A937V mutant cells were grown to 80% confluence in 20-cm plates (two for each cell line). Login to comment
145 Briefly, mock, ABCA1, and A937V mutant cells were grown to 80% confluence in 20-cm plates. Login to comment
168 A, ABCA1 expression in Mock, ABCA1 and ABCA1 mutant, A937V, before (lane 1-3) and after over night incubation with 10 nM mifepristone (lane 4-12). Login to comment
191 ABCA1-expressing cells, however, seemed to have slightly less cholesterol in the endoplasmic reticulum (fractions 9 and 10) than Mock or A937V cells, which may reflect higher cholesterol mobility from internal membranes to the plasma membrane upon ABCA1 expression. Login to comment
193 We also included a BHK cell line that expresses a mutant form of ABCA1 (A937V) upon mifepristone induction. Login to comment
195 Cholesterol distribution in A937V-expressing cells was also identical to that of wt ABCA1-expressing or Mock cells (Fig. 2, FIGURE 2. Login to comment
197 A, ABCA1 distribution in Mock, ABCA1, and A937V cells. Login to comment
201 B, Mock, ABCA1, and A937V cells were stained with filipin, and fluorescent images were taken under identical conditions. Login to comment
207 A937V contains a naturally occurring mutation in its first ATP-binding domain and is not able to mediate cholesterol efflux (Fig. 1B). Login to comment
210 Mock, ABCA1, and A937V cells were treated with ice-cold Triton X-100 (1%) for 30 min. Login to comment
220 To address this, we used BHK cells expressing A937V. Login to comment
221 The cold Triton X-100-extractable cholesterol fraction in A937V-expressing cells was identical to that in Mock cells (Fig. 3, A and B), indicating that cholesterol redistribution from raft to non-rafts requires functional ABCA1 protein. Login to comment
226 Once again, the A937V mutant failed to redistribute [3 H]sphingomyelin, consistent with its incapability to redistribute cholesterol in these cells. Login to comment
238 We transiently transfected Mock, ABCA1, and A937V cells with YFP-caveolin. Login to comment
242 BHK cells induced to express either empty vector (Mock), ABCA1 (ABCA1), or ABCA1 mutant A937V (A937V) cells were incubated with mifepristone overnight and subjected to 1% cold Triton X-100 extraction for 30 min on ice. Login to comment
248 C and D, Mock, ABCA1, and A937V cells were radiolabeled with 1 ␮Ci/ml [3 H]choline for 24 h, chilled on ice for 30 min prior to 1% Triton X-100 extraction at 4 °C. Login to comment
277 Furthermore, when we tested ABCA1 mutant A937V, we found that A937V was mainly localized on the plasma membrane and expressed at levels similar to wild-type ABCA1 (Fig. 6C). Login to comment
279 YFP-caveolin in A937V cells was mostly clustered, identical to that in Mock cells. Login to comment
280 This is consistent with our observations presented above that A937V is defective in redistributing rafts (Fig. 3). Login to comment
291 We therefore performed experiments using a non- detergent-based method, Optiprep gradient floatation, on Mock, ABCA1, and A937V cells (Fig. 7A). Login to comment
293 A minor portion of caveolin (ϳ5%) was found in fractions 7-9, co-localizing with clathrin, a non-raft maker, in Mock and A937V cells. Login to comment
294 However, there was much more caveolin in the non-raft fractions (20%) in ABCA1 cells than either Mock or A937V cells (Fig. 7B). Login to comment
295 There was no significant difference between Mock and A937V cells. Login to comment
300 BHK cells expressing either wt ABCA1 or A937V were transfected with YFP-caveolin and immunostained for ABCA1. Login to comment
305 Mock, ABCA1, and A937V cells were induced overnight with mifepristone, and membrane fractions were isolated as described under "Materials and Methods." Login to comment
307 B, the Western blots were scanned and analyzed for Mock, ABCA1, and A937V cells. Login to comment
313 Expression of A937V once again does not alter Akt activation (Fig. 8A). Login to comment
330 Mock, ABCA1, and A937V cells were induced and serum-starved overnight before EGF treatment. Login to comment
358 Most importantly, we found that a functional nucleotide-binding domain in ABCA1 is required for non-raft expansion, because the A937V mutant failed to induce any cholesterol, sphingomyelin, or caveolin redistribution. Login to comment
359 A937V mutant also failed to impair Akt phosphorylation. Login to comment
378 Our observations with the A937V mutant seem to support this later notion. Login to comment
192 ABCA1-expressing cells, however, seemed to have slightly less cholesterol in the endoplasmic reticulum (fractions 9 and 10) than Mock or A937V cells, which may reflect higher cholesterol mobility from internal membranes to the plasma membrane upon ABCA1 expression. Login to comment
194 We also included a BHK cell line that expresses a mutant form of ABCA1 (A937V) upon mifepristone induction. Login to comment
196 Cholesterol distribution in A937V-expressing cells was also identical to that of wt ABCA1-expressing or Mock cells (Fig. 2, FIGURE 2. Login to comment
198 A, ABCA1 distribution in Mock, ABCA1, and A937V cells. Login to comment
202 B, Mock, ABCA1, and A937V cells were stained with filipin, and fluorescent images were taken under identical conditions. Login to comment
208 A937V contains a naturally occurring mutation in its first ATP-binding domain and is not able to mediate cholesterol efflux (Fig. 1B). Login to comment
211 Mock, ABCA1, and A937V cells were treated with ice-cold Triton X-100 (1%) for 30 min. Login to comment
222 The cold Triton X-100-extractable cholesterol fraction in A937V-expressing cells was identical to that in Mock cells (Fig. 3, A and B), indicating that cholesterol redistribution from raft to non-rafts requires functional ABCA1 protein. Login to comment
227 Once again, the A937V mutant failed to redistribute [3 H]sphingomyelin, consistent with its incapability to redistribute cholesterol in these cells. Login to comment
239 We transiently transfected Mock, ABCA1, and A937V cells with YFP-caveolin. Login to comment
243 BHK cells induced to express either empty vector (Mock), ABCA1 (ABCA1), or ABCA1 mutant A937V (A937V) cells were incubated with mifepristone overnight and subjected to 1% cold Triton X-100 extraction for 30 min on ice. Login to comment
249 C and D, Mock, ABCA1, and A937V cells were radiolabeled with 1 òe;Ci/ml [3 H]choline for 24 h, chilled on ice for 30 min prior to 1% Triton X-100 extraction at 4 &#b0;C. Login to comment
377 Our observations with the A937V mutant seem to support this later notion. 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.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
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.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
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

[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.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
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
114 Patients homozygous for the mutations A255T and R1680W show HDL-C levels that are greater than 10% of age-and sex-matched population controls. Login to comment
122 This is indeed the case in heterozygous patients harboring mutations A255T, W590S, T929I, R1680W, and A937V, who all show HDL-C levelsϾ75% of normal age-and sex-matched controls. 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

[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.

Comments [show]

None has been submitted yet.

Sentences [show]
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.] 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.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
86 The Ala937Val mutation in Walker A motif (Bodzioch et al. 1999) and Ala1046Asp near Walker B motif (Wang et al. 2000) of the first NBF have been reported. Login to comment

[hide] ABCA1 protein enhances Toll-like receptor 4 (TLR4)... J Biol Chem. 2012 Nov 23;287(48):40502-12. doi: 10.1074/jbc.M112.413245. Epub 2012 Oct 10. Ma L, Dong F, Zaid M, Kumar A, Zha X
ABCA1 protein enhances Toll-like receptor 4 (TLR4)-stimulated interleukin-10 (IL-10) secretion through protein kinase A (PKA) activation.
J Biol Chem. 2012 Nov 23;287(48):40502-12. doi: 10.1074/jbc.M112.413245. Epub 2012 Oct 10., [PMID:23055522]

Abstract [show]
BACKGROUND: ABCA1 is known to suppress proinflammatory cytokines. RESULTS: ABCA1 activates PKA and up-regulates anti-inflammatory cytokine IL-10. Elevated PKA transforms macrophages to M2-like phenotype. Disrupting lipid rafts by statins MCD, and filipin recuperates ABCA1 phenotype and likely functions downstream of ABCA1. CONCLUSION: By modulating cholesterol, ABCA1 activates PKA. This generates M2-like macrophages. SIGNIFICANCE: ABCA1 does not simply suppress inflammatory response. It promotes M2-like activation and facilitates resolution. Nonresolving inflammatory response from macrophages is a major characteristic of atherosclerosis. Macrophage ABCA1 has been previously shown to suppress the secretion of proinflammatory cytokine. In the present study, we demonstrate that ABCA1 also promotes the secretion of IL-10, an anti-inflammatory cytokine critical for inflammation resolution. ABCA1(+/+) bone marrow-derived macrophages secrete more IL-10 but less proinflammatory cytokines than ABCA1(-/-) bone marrow-derived macrophages, similar to alternatively activated (M2) macrophages. We present evidence that ABCA1 activates PKA and that this elevated PKA activity contributes to M2-like inflammatory response from ABCA1(+/+) bone marrow-derived macrophages. Furthermore, cholesterol lowering by statins, methyl-beta-cyclodextrin, or filipin also activates PKA and, consequently, transforms macrophages toward M2-like phenotype. Conversely, cholesterol enrichment suppresses PKA activity and promotes M1-like inflammatory response. As the primary function of ABCA1 is cholesterol removal, our results suggest that ABCA1 activates PKA by regulating cholesterol. Indeed, forced cholesterol enrichment in ABCA1-expressing macrophages suppresses PKA activation and elicits M1-like response. Collectively, these findings reveal a novel protective process by ABCA1-activated PKA in macrophages. They also suggest cholesterol lowering in extra-hepatic tissues by statins as an anti-inflammation strategy.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
106 A nonfunctional ABCA1 mutant, A937V, failed to increase p-CREB despite being expressed at a similar level as WT ABCA1 (Fig. 2A) with correct targeting to the plasma membrane (21). Login to comment

[hide] Akt inhibition promotes ABCA1-mediated cholesterol... PLoS One. 2014 Nov 21;9(11):e113789. doi: 10.1371/journal.pone.0113789. eCollection 2014. Dong F, Mo Z, Eid W, Courtney KC, Zha X
Akt inhibition promotes ABCA1-mediated cholesterol efflux to ApoA-I through suppressing mTORC1.
PLoS One. 2014 Nov 21;9(11):e113789. doi: 10.1371/journal.pone.0113789. eCollection 2014., [PMID:25415591]

Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) plays an essential role in mediating cholesterol efflux to apolipoprotein A-I (apoA-I), a major housekeeping mechanism for cellular cholesterol homeostasis. After initial engagement with ABCA1, apoA-I directly interacts with the plasma membrane to acquire cholesterol. This apoA-I lipidation process is also known to require cellular signaling processes, presumably to support cholesterol trafficking to the plasma membrane. We report here that one of major signaling pathways in mammalian cells, Akt, is also involved. In several cell models that express ABCA1 including macrophages, pancreatic beta cells and hepatocytes, inhibition of Akt increases cholesterol efflux to apoA-I. Importantly, Akt inhibition has little effect on cells expressing non-functional mutant of ABCA1, implicating a specific role of Akt in ABCA1 function. Furthermore, we provide evidence that mTORC1, a major downstream target of Akt, is also a negative regulator of cholesterol efflux. In cells where mTORC1 is constitutively activated due to tuberous sclerosis complex 2 deletion, cholesterol efflux to apoA-I is no longer sensitive to Akt activity. This suggests that Akt suppresses cholesterol efflux through mTORC1 activation. Indeed, inhibition of mTORC1 by rapamycin or Torin-1 promotes cholesterol efflux. On the other hand, autophagy, one of the major pathways of cholesterol trafficking, is increased upon Akt inhibition. Furthermore, Akt inhibition disrupts lipid rafts, which is known to promote cholesterol efflux to apoA-I. We therefore conclude that Akt, through its downstream targets, mTORC1 and hence autophagy, negatively regulates cholesterol efflux to apoA-I.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
64 BHK cells stably expressing an mifepristone-inducible vector with human ABCA1 (ABCA1) or mutant A937V ABCA1 (A937V) gene insert were prepared as described previously [26]. Login to comment
121 It has little effect on BHK cells with no ABCA1 expression (data not shown) or BHK cells expressing a dysfunctional mutant form of ABCA1 (A937V) (Fig. 1 C). Login to comment
150 C) BHK-ABCA1 and BHK-A937V cells were induced with mifepristone (10 nM) overnight. Login to comment