ABCMdb

ABCA1 p.Arg2144*

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[hide] Genetic variation in the ABCA1 gene, HDL cholester... Atherosclerosis. 2010 Feb;208(2):305-16. Epub 2009 Jun 11. Frikke-Schmidt R
Genetic variation in the ABCA1 gene, HDL cholesterol, and risk of ischemic heart disease in the general population.
Atherosclerosis. 2010 Feb;208(2):305-16. Epub 2009 Jun 11., [PMID:19596329]

Abstract [show]
Epidemiological studies consistently demonstrate a strong inverse association between low levels of high-density lipoprotein (HDL) cholesterol and increased risk of ischemic heart disease (IHD). This review focuses on whether both rare and common genetic variation in ABCA1 contributes to plasma levels of HDL cholesterol and to risk of IHD in the general population, and further seeks to understand whether low levels of HDL cholesterol per se are causally related to IHD. Studies of the ABCA1 gene demonstrate a general strategy for detecting functional genetic variants, and show that both common and rare ABCA1 variants contribute to levels of HDL cholesterol and risk of IHD in the general population. The association between ABCA1 variants and risk of IHD appears, however, to be independent of plasma levels of HDL cholesterol. With the recent identification of the largest number of individuals heterozygous for loss-of-function mutations in ABCA1 worldwide, population studies suggests that genetically low HDL cholesterol per se does not predict an increased risk of IHD, and thus questions the causality of isolated low levels of HDL cholesterol for the development of IHD.

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2337 4.2. Frequency of mutations in the general population Four of seven non-synonymous mutations (P1065C, G1216V, N1800H, R2144X), ranging in frequency from 0.1 to two per 1000, were associated with low levels of HDL cholesterol in the general population. Login to comment
2342 Genotyping revealed 28 het- erozygous carriers of P1065S, G1216V, N1800H, and R2144X in the CCHS (n = 9022), and 76 heterozygous carriers of G1216V, N1800H, and R2144 in the Copenhagen General Population Study (CGPS) (n = 31,241) [66]. Login to comment

[hide] ABCA1 gene mutations, HDL cholesterol levels, and ... JAMA. 2008 Nov 5;300(17):1997-8; author reply 1998. Brunham LR, Kastelein JJ, Hayden MR
ABCA1 gene mutations, HDL cholesterol levels, and risk of ischemic heart disease.
JAMA. 2008 Nov 5;300(17):1997-8; author reply 1998., [PMID:18984885]

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54 Third, our findings are consistent with our previous reports on the same cohort showing that polymorphisms and mutations in ABCA1 may or may not affect HDL levels, but that risk of IHD is independent of these HDL effects.2-4 Fourth, it is not correct that to state that heterozygosity for the 3 rare mutations in the CCHS (P1065S, G1216V, or R2144X; n=6) was associated with a 25% reduction in LDL cholesterol levels compared with noncarriers because this was not statistically significant. Login to comment
61 Third, our findings are consistent with our previous reports on the same cohort showing that polymorphisms and mutations in ABCA1 may or may not affect HDL levels, but that risk of IHD is independent of these HDL effects.2-4 Fourth, it is not correct that to state that heterozygosity for the 3 rare mutations in the CCHS (P1065S, G1216V, or R2144X; n=6) was associated with a 25% reduction in LDL cholesterol levels compared with noncarriers because this was not statistically significant. Login to comment

[hide] Effect of ABCA1 mutations on risk for myocardial i... Curr Atheroscler Rep. 2008 Oct;10(5):413-26. Iatan I, Alrasadi K, Ruel I, Alwaili K, Genest J
Effect of ABCA1 mutations on risk for myocardial infarction.
Curr Atheroscler Rep. 2008 Oct;10(5):413-26., [PMID:18706283]

Abstract [show]
The adenosine triphosphate-binding cassette A1 (ABCA1) gene codes for a cellular phospholipid and cholesterol transporter that mediates the initial and essential step in high-density lipoprotein (HDL) biogenesis: the formation of nascent HDL particles. Mutations at the ABCA1 gene locus cause severe familial HDL deficiency and, in the homozygous form, cause Tangier disease. Several studies have investigated the influence of ABCA1 variation on lipid metabolism and coronary heart disease, but they have resulted in controversial and inconsistent results. Genetic variability at the ABCA1 gene has also been associated with increased risk of myocardial infarction. In one study, this association was independent of HDL cholesterol levels, raising the possibility that the measurement of HDL cholesterol levels may not provide adequate information on the functional roles of HDL particles. Nevertheless, genomic screening for complex diseases, such as coronary heart disease, and HDL deficiency in particular, may not add additional information to that gained from conventional global cardiovascular risk stratification.

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119 Genetic variation in ABCA1 and risk of myocardial infarction Study* / year Population screened HDL-C, mmol/L ABCA1 variants Conclusions Clee et al. [28] / 2000 Within 11 TD families: Del L693, R2144X † , Del E,D1893,94 † , R909X, M1091T † , P2150L † , ivs25+1G→C, Del C6825→2145X, CTC6952- 4TT→2203X, C1477R, Q597R, T929I ABCA1 heterozygous patients had a 40%-45% decrease in HDL-C and a greater than threefold increased risk of CHD versus unaffected individuals. Login to comment

[hide] Association of loss-of-function mutations in the A... JAMA. 2008 Jun 4;299(21):2524-32. Frikke-Schmidt R, Nordestgaard BG, Stene MC, Sethi AA, Remaley AT, Schnohr P, Grande P, Tybjaerg-Hansen A
Association of loss-of-function mutations in the ABCA1 gene with high-density lipoprotein cholesterol levels and risk of ischemic heart disease.
JAMA. 2008 Jun 4;299(21):2524-32., [PMID:18523221]

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CONTEXT: Low levels of high-density lipoprotein (HDL) cholesterol are inversely related to cardiovascular risk. Whether this is a causal effect is unclear. OBJECTIVE: To determine whether genetically reduced HDL cholesterol due to heterozygosity for 4 loss-of-function mutations in ABCA1 cause increased risk of ischemic heart disease (IHD). DESIGN, SETTING, AND PARTICIPANTS: Three studies of white individuals from Copenhagen, Denmark, were used: the Copenhagen City Heart Study (CCHS), a 31-year prospective general population study (n = 9022; 28 heterozygotes); the Copenhagen General Population Study (CGPS), a cross-sectional general population study (n = 31,241; 76 heterozygotes); and the Copenhagen Ischemic Heart Disease Study (CIHDS), a case-control study (n = 16,623; 44 heterozygotes). End points in all 3 studies were recorded during the period of January 1, 1976, through July 9, 2007. MAIN OUTCOME MEASURES: Levels of HDL cholesterol in the general population, cellular cholesterol efflux, and the association between IHD and HDL cholesterol and genotype. RESULTS: Heterozygotes vs noncarriers for 4 ABCA1 mutations (P1065S, G1216V, N1800H, R2144X) had HDL cholesterol levels of 41 mg/dL (interquartile range, 31-50 mg/dL) vs 58 mg/dL (interquartile range, 46-73 mg/dL), corresponding to a reduction in HDL cholesterol of 17 mg/dL (P < .001). A 17-mg/dL lower HDL cholesterol level in the CCHS was associated with a multifactorially adjusted hazard ratio for IHD of 1.70 (95% confidence interval [CI], 1.57-1.85). However, for IHD in heterozygotes vs noncarriers, the multifactorially adjusted hazard ratio was 0.67 (95% CI, 0.28-1.61; 1741 IHD events) in the CCHS, the multifactorially adjusted odds ratio was 0.82 (95% CI, 0.34-1.96; 2427 IHD events) in the CGPS, and the multifactorially adjusted odds ratio was 0.86 (95% CI, 0.32-2.32; 2498 IHD cases) in the CIHDS. The corresponding odds ratio for IHD in heterozygotes vs noncarriers for the combined studies (n = 41,961; 6666 cases; 109 heterozygotes) was 0.93 (95% CI, 0.53-1.62). CONCLUSION: Lower plasma levels of HDL cholesterol due to heterozygosity for loss-of-function mutations in ABCA1 were not associated with an increased risk of IHD.

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12 Results Heterozygotes vs noncarriers for 4 ABCA1 mutations (P1065S, G1216V, N1800H, R2144X) had HDL cholesterol levels of 41 mg/dL (interquartile range, 31-50 mg/dL) vs 58 mg/dL (interquartile range, 46-73 mg/dL), corresponding to a reduction in HDL cholesterol of 17 mg/dL (PϽ.001). Login to comment
26 The 9022 individuals were genotyped for all non-synonymous mutations (S364C, T774P, K776N, P1065S, G1216V, N1800H, R2144X [http://www.hgmd.cf.ac.uk/ac /index.php; http://www.mutdb.org]), which were previously identified by resequencing the promoter, coding region,andconsensussplicesitesofABCA1 in 190 individuals of Danish ancestry with high and low HDL cholesterol levels.13 All end points and data collection were recorded in the follow-up period of January 1, 1976, through July 9, 2007. Login to comment
39 Participants in the CIHDS were genotyped for the 4 mutations (P1065S, G1216V, N1800H, R2144X) associated with reduced HDL cholesterol levels in the CCHS and the CGPS. Login to comment
60 On a continuous scale, a 17-mg/dL (to convert to mmol/L, multiply by 0.0259) lower HDL cholesterol level associated with a multifactorially adjusted HR for IHD of 1.70 (95% CI, 1.57-1.85), similar to that reported in other studies.1 ABCA1 Mutation Heterozygotes and Plasma HDL Cholesterol Four of 7 mutations (P1065S, G1216V, N1800H, R2144X) were associated with Figure 1. Login to comment
69 Number of Participants Heterozygous for Missense or Nonsense Mutations in ABCA1 in the Studied Populations Mutation CCHS (n = 9022) CGPS (n = 31 241) CIHDS (n = 2498) P1065S 1 0 0 G1216V 3 3 1 N1800H 22 70 3 R2144X 2 3 1 Abbreviations: CCHS, Copenhagen City Heart Study; CGPS, Copenhagen General Population Study; CIHDS, Copenhagen Ischemic Heart Disease Study. Login to comment
72 The overall heterozygote frequency in the general population was approximately 3:1000 in both the CCHS and the CGPS, the majority carrying the N1800H mutation. Login to comment
78 ABCA1 Mutations and Cellular Cholesterol Efflux in Vitro In agreement with the observed lower plasma HDL cholesterol levels associated with these mutations in vivo, 4 mutations were associated with impaired cholesterol efflux in vitro: 79% (95% CI, 56%-103%) for P1065S, 74% (95% CI, 54%-95%) for G1216V, 49% (95% CI, 37%-60%) for N1800H, and 48%7 for R2144X compared with 100% in wild-type (P=.04 for all). Login to comment
88 bProbands heterozygous for P1065S, G1216V, or R2144X. Login to comment
89 cProbands heterozygous for P1065S, G1216V, R2144X, or N1800H. Login to comment
98 When restricting the analyses to N1800H heterozygotes, the corresponding values were an HR of 0.50 (95% CI, 0.16-1.56), an OR of 0.87 (95% CI, 0.36-2.10), and an OR of 0.51 (95% CI, 0.15-1.80). Login to comment
111 Plasma High-Density Lipoprotein (HDL) Cholesterol and Apolipoprotein A-I Levels for Heterozygous Carriers of ABCA1 Mutations in the Copenhagen City Heart Study 120 80 60 100 40 20 0 20 40 60 80 100 Women 120 80 60 100 40 20 0 20 40 60 80 100 Men HDL cholesterol 220 140 160 120 180 200 100 80 60 0 20 40 60 80 100 Women Age, y Age, y Age, y 200 160 140 180 120 100 80 60 0 20 40 60 80 100 Men Age, y Apolipoprotein A-I Mutation P1065S G1216V N1800H R2144X 95th 50th 5th 95th 50th 5th 95th 50th 5th 95th 50th 5th mg/dLmg/dL Exact values for each heterozygous mutation carrier are superimposed on the 5th, 50th, and 95th percentiles for age and sex as a whole (N=9022). Login to comment
117 Plasma High-Density Lipoprotein (HDL) Cholesterol and Apolipoprotein A-I Levels for Heterozygous Carriers of ABCA1 Mutations in the Copenhagen General Population Study 120 80 60 100 40 20 0 20 40 60 80 100 Women 120 80 60 100 40 20 0 20 40 60 80 100 Men HDL cholesterol 240 140 160 120 180 200 220 100 80 0 20 40 60 80 100 Women Age, y 240 160 140 180 200 220 120 100 80 60 0 20 40 60 80 100 Men Age, y Apolipoprotein A-I 95th 50th 5th 95th 50th 5th 95th 50th 5th 95th 50th 5th G1216V N1800H R2144X Mutation Age, y Age, y mg/dLmg/dL Exact values for each heterozygous mutation carrier are superimposed on the 5th, 50th, and 95th percentiles for age and sex as a whole (n=31 241). Login to comment
25 The 9022 individuals were genotyped for all nonsynonymous mutations (S364C, T774P, K776N, P1065S, G1216V, N1800H, R2144X [http://www.hgmd.cf.ac.uk/ac /index.php; http://www.mutdb.org]), which were previously identified by resequencing the promoter, coding region,andconsensussplicesitesofABCA1 in 190 individuals of Danish ancestry with high and low HDL cholesterol levels.13 All end points and data collection were recorded in the follow-up period of January 1, 1976, through July 9, 2007. Login to comment
38 Participants in the CIHDS were genotyped for the 4 mutations (P1065S, G1216V, N1800H, R2144X) associated with reduced HDL cholesterol levels in the CCHS and the CGPS. Login to comment
52 Plasma High-Density Lipoprotein (HDL) Cholesterol and Apolipoprotein A-I Levels for Heterozygous Carriers of ABCA1 Mutations in the Copenhagen City Heart Study 120 80 60 100 40 20 0 20 40 60 80 100 Women 120 80 60 100 40 20 0 20 40 60 80 100 Men HDL cholesterol 220 140 160 120 180 200 100 80 60 0 20 40 60 80 100 Women Age, y Age, y Age, y 200 160 140 180 120 100 80 60 0 20 40 60 80 100 Men Age, y Apolipoprotein A-I Mutation P1065S G1216V N1800H R2144X 95th 50th 5th 95th 50th 5th 95th 50th 5th 95th 50th 5th mg/dL mg/dL Exact values for each heterozygous mutation carrier are superimposed on the 5th, 50th, and 95th percentiles for age and sex as a whole (N=9022). Login to comment
62 ABCA1 Mutations and Cellular Cholesterol Efflux in Vitro In agreement with the observed lower plasma HDL cholesterol levels associated with these mutations in vivo, 4 mutations were associated with impaired cholesterol efflux in vitro: 79% (95% CI, 56%-103%) for P1065S, 74% (95% CI, 54%-95%) for G1216V, 49% (95% CI, 37%-60%) for N1800H, and 48%7 for R2144X compared with 100% in wild-type (P=.04 for all). Login to comment
73 cProbands heterozygous for P1065S, G1216V, R2144X, or N1800H. 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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554 Conversely, a small number of mutations are associated with less than 50% of control HDL cholesterol, specifically M1091T, G1216V, and the truncation mutations R2144X, R282X, and R909X. Login to 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] ATP-binding cassette transporter A1 contains a nov... J Biol Chem. 2004 Nov 12;279(46):48477-85. Epub 2004 Sep 3. Fitzgerald ML, Okuhira K, Short GF 3rd, Manning JJ, Bell SA, Freeman MW
ATP-binding cassette transporter A1 contains a novel C-terminal VFVNFA motif that is required for its cholesterol efflux and ApoA-I binding activities.
J Biol Chem. 2004 Nov 12;279(46):48477-85. Epub 2004 Sep 3., [PMID:15347662]

Abstract [show]
The stimulation of cellular cholesterol and phospholipid efflux by apolipoprotein A-I is mediated by the activity of the ATP-binding cassette transporter A1 (ABCA1). Individuals with Tangier disease harbor loss-of-function mutations in this transporter that have proven useful in illuminating its activity. Here, we analyze a mutation that deletes the last 46 residues of the 2261 amino acid transporter (Delta46) and eliminates its lipid efflux. As the final four amino acids of the C terminus represent a putative PDZ-binding motif, we initially characterized deletion mutants lacking only these residues. Although a moderate decline in lipid efflux was detected, this decline was not as profound as that seen in the Delta46 mutant. Subsequent systematic analysis of the ABCA1 C terminus revealed a novel, highly conserved motif (VFVNFA) that was required for lipid efflux. Alteration of this motif, which is present in some but not all members of the ABCA family, did not prevent trafficking of the transporter to the plasma membrane but did eliminate its binding of apoA-I. Chimeric transporters, generated by substituting the C termini of either ABCA4 or ABCA7 for the endogenous terminus, demonstrated that ABCA1 could stimulate cholesterol efflux without its PDZ-binding motif but not without the VFVNFA motif. When a peptide containing the VFVNFA sequence was introduced into ABCA1-expressing cells, ABCA1-mediated lipid efflux was also markedly inhibited. These results indicate that the C-terminal VFVNFA motif of ABCA1 is essential for its lipid efflux activity. The data also suggest that this motif participates in novel protein-protein interactions that may be shared among members of the ABCA family.

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113 The ABCA1 C Terminus Is Essential for Efflux but the PDZ Protein-binding Motif Is Not-To test the functional importance of the C terminus, we engineered the 46-amino acid Tangier deletion (Q2215X, ⌬46) as well as a larger deletion described by Clee et al. (R2144X, ⌬117) (33) into our cDNA constructs. 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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67 TD 3` deletion (intron 38) truncated truncation [61] 5587 C/G 38 S1731C extracellular [68] TD 5793 A/C 40 N1800H extracellular loop, sm [65] FHA 5946 C/T 41 R1851X truncation [75..] FHA 6068 del 42 del 1893-1894(E,D) cytoplasmic [63] TD 6152 (14bp Ins) (42-43) truncated truncation [67] 6316 A/G 44 K1974R cytoplasmic [67] 6421 T/C 45 F2009S cytoplasmic [9] TD 6636 C/T 47 R2081W cytoplasmic [64] FHA 6825 C/T 49 R2144X cytoplasmic [63] TD 6825 del C 49 2145X truncation [62] FHA 6844 C/T 49 P2150L cytoplasmic [62] 6898 C/T 49 P2168L cytoplasmic [67] TD CTC6952-4TT 49 2203X truncation [62] TD 6968 (4bp Ins) 49 2215X, truncated PDZ binding (cyto) [65] *Location in accordance with Santamaria-Fojo et al. (Proc Natl Acad Sci U S A 2000; 97:7987-7992). Login to comment

[hide] Cellular phospholipid and cholesterol efflux in hi... Circulation. 2003 Mar 18;107(10):1366-71. Marcil M, Bissonnette R, Vincent J, Krimbou L, Genest J
Cellular phospholipid and cholesterol efflux in high-density lipoprotein deficiency.
Circulation. 2003 Mar 18;107(10):1366-71., [PMID:12642355]

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BACKGROUND: Prospective studies have examined the relationship between coronary artery disease and low plasma levels of high-density lipoprotein cholesterol (HDL-C). METHODS AND RESULTS: We investigated the causes of hypoalphalipoproteinemia (HypoA; HDL-C <5th percentile) in 64 subjects (12 women and 52 men). Apolipoprotein AI-mediated cellular cholesterol and phospholipid efflux were measured in fibroblasts from HypoA subjects, 9 controls, 2 patients with Tangier disease, and 5 patients with hyperalphalipoproteinemia. A phospholipid efflux defect was defined as <70% of controls. Mean HDL-C was 0.49+/-0.21 mmol/L. Cholesterol and phospholipid efflux correlated strongly (r=0.72, P<0.001). Phospholipid efflux and HDL-C (r=0.64, P<0.001) correlated in HypoA subjects. However, phospholipid or cholesterol efflux was no longer a determinant of HDL-C levels at higher levels (> approximately 1.0 mmol/L) of HDL-C. In HypoA subjects, 4 cases of Tangier disease and 6 of familial HDL deficiency (heterozygous Tangier disease) were identified (10 of 64; 16%). In the remaining 54 subjects, mean lipid efflux was not significantly different from controls and subjects with hyperalphalipoproteinemia. A phospholipid efflux defect was identified in 7 additional HypoA subjects, and a cholesterol efflux defect was detected in 11 subjects. In 2 of these subjects, the ABCA1 gene was ruled out as the cause of the efflux defect, while in 3, the low HDL-C trait segregated with the ABCA1 gene locus. CONCLUSIONS: Lipidation of lipid-poor apolipoprotein AI may not be a major determinant of cholesterol accumulation within more mature HDL particles and increasing cholesterol or phospholipid efflux beyond normal levels may not lead to increase in plasma HDL-C levels. ABCA1 is essential in the initial steps of HDL formation but other plasma events are major modulators of HDL-C levels.

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85 Molecular Characterization of ABCA1 Gene in Study Subjects Cell Lines HDL-C, mmol/L Nucleotide Change Predicted Protein Alteration TD CTL-1 0.10 Exon 30 T4369C; exon 24 splice site G3C C1477R; part of the transcript deleted TD CTL-2 0.15 Exon 13 A1730G Q597R FHD-1 0.40 Exon 14 ⌬2017-9 ⌬L693 FHD-2 0.18 Exon 48 C6370T R2144X FHD-3 0.39 Exon 41 ⌬5618-23 ⌬ED1893,4 FHD-4 0.18 Exon 18 C2665T R909X FHD-5 0.10 Exon 23 T3667C M1091T FHD-6 0.57 Exon 49 C6844T P2150L, R587W TD-1 0.03 Exon 48 ⌬C6370; ND 2145X TD-2 0.07 ND ND TD-3 0.03 ND 2203X TD-4 0.09 Exon 19 C3181T; ND T929I; ND CTL indicates control. Login to comment
79 Molecular Characterization of ABCA1 Gene in Study Subjects Cell Lines HDL-C, mmol/L Nucleotide Change Predicted Protein Alteration TD CTL-1 0.10 Exon 30 T4369C; exon 24 splice site G3C C1477R; part of the transcript deleted TD CTL-2 0.15 Exon 13 A1730G Q597R FHD-1 0.40 Exon 14 èc;2017-9 èc;L693 FHD-2 0.18 Exon 48 C6370T R2144X FHD-3 0.39 Exon 41 èc;5618-23 èc;ED1893,4 FHD-4 0.18 Exon 18 C2665T R909X FHD-5 0.10 Exon 23 T3667C M1091T FHD-6 0.57 Exon 49 C6844T P2150L, R587W TD-1 0.03 Exon 48 èc;C6370; ND 2145X TD-2 0.07 ND ND TD-3 0.03 ND 2203X TD-4 0.09 Exon 19 C3181T; ND T929I; ND CTL indicates control. Login to comment

[hide] cAMP induces ABCA1 phosphorylation activity and pr... J Lipid Res. 2002 Dec;43(12):2087-94. Haidar B, Denis M, Krimbou L, Marcil M, Genest J Jr
cAMP induces ABCA1 phosphorylation activity and promotes cholesterol efflux from fibroblasts.
J Lipid Res. 2002 Dec;43(12):2087-94., [PMID:12454270]

Abstract [show]
ATP-binding cassette transporter A1 (ABCA1) plays a crucial role in apoA-I lipidation, a key step in reverse cholesterol transport. cAMP induces apoA-I binding activity and promotes cellular cholesterol efflux. We investigated the role of the cAMP/protein kinase A (PKA) dependent pathway in the regulation of cellular cholesterol efflux. Treatment of normal fibroblasts with 8-bromo-cAMP (8-Br-cAMP) increased significantly apoA-I-mediated cholesterol efflux, with specificity for apoA-I, but not for cyclodextrin. Concomitantly, 8-Br-cAMP increased ABCA1 phosphorylation in a time-dependent manner. Maximum phosphorylation was reached in <10 min, representing a 260% increase compared to basal ABCA1 phosphorylation level. Forskolin, a known cAMP regulator, increased both cellular cholesterol efflux and ABCA1 phosphorylation. In contrast, H-89 PKA inhibitor reduced cellular cholesterol efflux by 70% in a dose-dependent manner and inhibited almost completely ABCA1 phosphorylation. To determine whether naturally occurring mutants of ABCA1 may affect its phosphorylation activity, fibroblasts from subjects with familial HDL deficiency (FHD, heterozygous ABCA1 defect) and Tangier disease (TD, homozygous/compound heterozygous ABCA1 defect) were treated with 8-Br-cAMP or forskolin. Cellular cholesterol efflux and ABCA1 phosphorylation were increased in FHD but not in TD cells. Taken together, these findings provide evidence for a link between the cAMP/PKA-dependent pathway, ABCA1 phosphorylation, and apoA-I mediated cellular cholesterol efflux.

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176 Molecular characterization of ABCA1 gene in study subjects Cell Lines HDL-C Nucleotide Change Predicted Protein Alteration mmol/l CTR1 1.63 - - CTR2 1.20 - - FHD1 0.27 Exon 14 ⌬2017-9 ⌬L693 FHD2 0.18 Exon 18 C2665T R909X FHD3 0.39 Exon 41 ⌬5618-23 ⌬ED1893,4 FHD4 0.18 Exon 48 C6370T R2144X FHD5 0.09 Exon 36 GG5277,8C fs 1628G, Q1636X TD1 Ͻ0.1 Exon 30 T4369C; Exon 24 splice site G→C C1477R; Part of the transcript deleted TD2 Ͻ0.1 Exon 13 A1730G Q597R TD3 Ͻ0.1 Exon 48 ⌬C6370; nd 2145X; nd FHD1-5 are heterozygous for the reported mutation; TD1,3 are compound heterozygous and TD2 is homozygous. Login to comment

[hide] Truncation mutations in ABCA1 suppress normal upre... J Lipid Res. 2002 Nov;43(11):1939-49. Wellington CL, Yang YZ, Zhou S, Clee SM, Tan B, Hirano K, Zwarts K, Kwok A, Gelfer A, Marcil M, Newman S, Roomp K, Singaraja R, Collins J, Zhang LH, Groen AK, Hovingh K, Brownlie A, Tafuri S, Genest J Jr, Kastelein JJ, Hayden MR
Truncation mutations in ABCA1 suppress normal upregulation of full-length ABCA1 by 9-cis-retinoic acid and 22-R-hydroxycholesterol.
J Lipid Res. 2002 Nov;43(11):1939-49., [PMID:12401893]

Abstract [show]
Mutations in ABCA1 uniformly decrease plasma HDL-cholesterol (HDL-C) and reduce cholesterol efflux, yet different mutations in ABCA1 result in different phenotypic effects in heterozygotes. For example, truncation mutations result in significantly lower HDL-C and apoliprotein A-I (apoA-I) levels in heterozygotes compared with nontruncation mutations, suggesting that truncation mutations may negatively affect the wild-type allele. To specifically test this hypothesis, we examined ABCA1 protein expression in response to 9-cis-retinoic acid (9-cis-RA) and 22-R-hydroxycholesterol (22-R-OH-Chol) in a collection of human fibroblasts representing eight different mutations and observed that truncation mutations blunted the response to oxysterol stimulation and dominantly suppressed induction of the remaining full-length allele to 5-10% of wild-type levels. mRNA levels between truncation and nontruncation mutations were comparable, suggesting that ABCA1 expression was suppressed at the protein level. Dominant negative activity of truncated ABCA1 was recapitulated in an in vitro model using transfected Cos-7 cells. Our results suggest that the severe reduction of HDL-C in patients with truncation mutations may be at least partly explained by dominant negative suppression of expression and activity of the remaining full-length ABCA1 allele. These data suggest that ABCA1 requires a physical association with itself or other molecules for normal function and has important pharmacogenetic implications for individuals with truncation mutations.

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131 Expression data by mutation Family Mutation Proteinc Induced/Uninduced HDL-C Net Effluxd mmol/l % of control FHA1 Del L 693 5.95 (0.82) 0.4 79.47 (22.63) FHA2 R2144X 2.45 (0.19) 0.18 64.01 (11.12) FHA3 Del E,D 1893, 1894 7.82 (1.48) 0.39 60.03 (11.85) FHA4 R909X 2.32 (0.52) 0.18 72.28 (18.01) FHA5 M1091T 6.42 (0.29) 0.1 47.24 (3.79) TD1 ivs2511G-C, C1477R 3.46 (0.50) 0.1 2.73 (1.05) TD1-ha C1477R 10.28 (1.07) 0.9 58.14 (5.49) TD3 GG 5277C - 1636 2.89 (0.59) 0.09 23.3 (1.29) TD3-hb T9291 6.65 (0.10) 1.12 51.8 (1.30) TD4 Del C 6825 - 2145X, unidentified 1.14 (0.13) 0.03 17.22 (0) Control None 11.31 (0.68) 1.63 100.00 (7.09) a TD1-h is the heterozygous parent of the TD1 proband. Login to comment

[hide] The carboxyterminus of the ATP-binding cassette tr... Biochem Biophys Res Commun. 2002 May 3;293(2):759-65. Buechler C, Boettcher A, Bared SM, Probst MC, Schmitz G
The carboxyterminus of the ATP-binding cassette transporter A1 interacts with a beta2-syntrophin/utrophin complex.
Biochem Biophys Res Commun. 2002 May 3;293(2):759-65., [PMID:12054535]

Abstract [show]
Recent work identified ABCA1 as the major regulator of plasma HDL-cholesterol responsible for the removal of excess choline-phospholipids and cholesterol from peripheral cells and tissues. ABCA1 function may depend on the association with heteromeric proteins and to identify these candidates a human liver yeast two-hybrid library was screened with the carboxyterminal 144 amino acids of ABCA1. Beta2-syntrophin was found to interact with ABCA1 and the C-terminal five amino acids of ABCA1 proned to represent a perfect tail for binding to syntrophin PDZ domains. Immunoprecipitation further confirmed the association of ABCA1 and beta2-syntrophin and in addition utrophin, known to couple beta2-syntrophin and its PDZ ligands to the F-actin cytoskeleton, was identified as a constituent of this complex. ABCA1 in the plasmamembrane of human macrophages was found to be partially associated with Lubrol rafts and effluxed choline-phospholipids involve these microdomains. Beta2-syntrophin does not colocalize in these rafts indicating that beta2-syntrophin may participate in the retaining of ABCA1 in cytoplasmic vesicles and for the targeting of ABCA1 to plasmamembrane microdomains when ABCA1 is released from beta2-syntrophin.

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85 (1) R2144X causing the Tangier disease [32]; (2) P2151L rare single nucleotide polymorphism (own unpublished results); (3) F2163S; (5) V2244I associated with low HDL, hypertrophic cardiomyopathy, and disturbed glucose metabolism; (4) 4 bp insertion at nucleotide 6513 causing a premature stop and Tangier disease [20]. Login to comment
84 (1) R2144X causing the Tangier disease [32]; (2) P2151L rare single nucleotide polymorphism (own unpublished results); (3) F2163S; (5) V2244I associated with low HDL, hypertrophic cardiomyopathy, and disturbed glucose metabolism; (4) 4 bp insertion at nucleotide 6513 causing a premature stop and Tangier disease [20]. Login to comment

[hide] Common genetic variation in ABCA1 is associated wi... Circulation. 2001 Mar 6;103(9):1198-205. Clee SM, Zwinderman AH, Engert JC, Zwarts KY, Molhuizen HO, Roomp K, Jukema JW, van Wijland M, van Dam M, Hudson TJ, Brooks-Wilson A, Genest J Jr, Kastelein JJ, Hayden MR
Common genetic variation in ABCA1 is associated with altered lipoprotein levels and a modified risk for coronary artery disease.
Circulation. 2001 Mar 6;103(9):1198-205., [PMID:11238261]

Abstract [show]
BACKGROUND: Low plasma HDL cholesterol (HDL-C) is associated with an increased risk of coronary artery disease (CAD). We recently identified the ATP-binding cassette transporter 1 (ABCA1) as the major gene underlying the HDL deficiency associated with reduced cholesterol efflux. Mutations within the ABCA1 gene are associated with decreased HDL-C, increased triglycerides, and an increased risk of CAD. However, the extent to which common variation within this gene influences plasma lipid levels and CAD in the general population is unknown. METHODS AND RESULTS: We examined the phenotypic effects of single nucleotide polymorphisms in the coding region of ABCA1. The R219K variant has a carrier frequency of 46% in Europeans. Carriers have a reduced severity of CAD, decreased focal (minimum obstruction diameter 1.81+/-0.35 versus 1.73+/-0.35 mm in noncarriers, P:=0.001) and diffuse atherosclerosis (mean segment diameter 2.77+/-0.37 versus 2.70+/-0.37 mm, P:=0.005), and fewer coronary events (50% versus 59%, P:=0.02). Atherosclerosis progresses more slowly in carriers of R219K than in noncarriers. Carriers have decreased triglyceride levels (1.42+/-0.49 versus 1.84+/-0.77 mmol/L, P:=0.001) and a trend toward increased HDL-C (0.91+/-0.22 versus 0.88+/-0.20 mmol/L, P:=0.12). Other single nucleotide polymorphisms in the coding region had milder effects on plasma lipids and atherosclerosis. CONCLUSIONS: These data suggest that common variation in ABCA1 significantly influences plasma lipid levels and the severity of CAD.

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135 Carriers of V771M had no difference in lipid levels compared with noncarriers. Login to comment
140 The presence of this variant in individuals heterozygous for the R2144X ABCA1 mutation was associated with further significantly decreased HDL-C compared with R2144X carriers without this polymorphism (0.16Ϯ0.04 mmol/L, nϭ2, versus 0.64Ϯ0.14 mmol/L, nϭ10; Pϭ0.0009). Login to comment

[hide] ATP-binding cassette transporters, atherosclerosis... Circ Res. 2014 Jan 3;114(1):157-70. doi: 10.1161/CIRCRESAHA.114.300738. Westerterp M, Bochem AE, Yvan-Charvet L, Murphy AJ, Wang N, Tall AR
ATP-binding cassette transporters, atherosclerosis, and inflammation.
Circ Res. 2014 Jan 3;114(1):157-70. doi: 10.1161/CIRCRESAHA.114.300738., [PMID:24385509]

Abstract [show]
Although recent genome-wide association studies have called into question the causal relationship between high-density lipoprotein (HDL) cholesterol levels and cardiovascular disease, ongoing research in animals and cells has produced increasing evidence that cholesterol efflux pathways mediated by ATP-binding cassette (ABC) transporters and HDL suppress atherosclerosis. These differing perspectives may be reconciled by a modified HDL theory that emphasizes the antiatherogenic role of cholesterol flux pathways, initiated in cells by ABC transporters. ABCA1 and ABCG1 control the proliferation of hematopoietic stem and multipotential progenitor cells in the bone marrow and hematopoietic stem and multipotential progenitor cell mobilization and extramedullary hematopoiesis in the spleen. Thus, activation of cholesterol efflux pathways by HDL infusions or liver X receptor activation results in suppression of hematopoietic stem and multipotential progenitor cell mobilization and extramedullary hematopoiesis, leading to decreased production of monocytes and neutrophils and suppression of atherosclerosis. In addition, macrophage-specific knockout of transporters has confirmed their role in suppression of inflammatory responses in the arterial wall. Recent studies have also shown that ABCG4, a close relative of ABCG1, controls platelet production, atherosclerosis, and thrombosis. ABCG4 is highly expressed in megakaryocyte progenitors, where it promotes cholesterol efflux to HDL and controls the proliferative responses to thrombopoietin. Reconstituted HDL infusions act in an ABCG4-dependent fashion to limit hypercholesterolemia-driven excessive platelet production, thrombosis, and atherogenesis, as occurs in human myeloproliferative syndromes. Activation of ABC transporter-dependent cholesterol efflux pathways in macrophages, hematopoietic stem and multipotential progenitor cells, or platelet progenitors by reconstituted HDL infusion or liver X receptor activation remain promising approaches to the treatment of human atherothrombotic diseases.

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59 In a Mendelian randomization approach in a prospective cohort comprising ࣈ9000 individuals, heterozygosity for the ABCA1 mutation K776N led to a 2-to-3 times higher risk of ischemic heart disease.105 Furthermore, 5 single-nucleotide polymorphisms (SNPs) inABCA1 (V771M,V825I, I883M, E1172D, R1587K) were shown to predict risk of ischemic heart disease in a cohort of 9259 individuals.106 However, the same group reported more recently that heterozygosity for 4 loss-of-function mutations (P1065S, G1216V, N1800H, R2144X) was not associated with a higher risk of ischemic heart disease in 3 prospective cohorts comprising 56ߙ886 individuals.107 It must be noted, however, that only small decreases in HDL, of ࣈ28% as opposed to ࣈ50% in previously reported ABCA1 heterozygotes, were observed.94,101-103,107 Also, the residual cholesterol efflux was substantial (74%-79% for P1065S and G1216V and 48%-49% for N1800H and R2144X for homozygous mutations compared with controls),107 whereas in patients with TD there was only 20% to 30% residual cholesterol efflux.108 In addition, LDL levels were reduced by ࣈ25%, probably offsetting the effects of reduced HDL on CVD.107 Thus, the conflicting results in these studies could be related to inclusion of relatively mild ABCA1 mutations as well as offsetting effects of reduced LDL cholesterol levels.109 In a meta-analysis of genome-wide association studies, SNPs near the ABCA1 gene have been associated with HDL and total cholesterol levels,110,111 but not with cardiovascular risk.112 Although these studies have the benefit of huge statistical power, some caution is merited in the interpretation of findings. 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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932 For example, some of the ABCA1 missense mutations (P1065S, G1216V, N1800H, R2144X) cause only a mild decrease of cholesterol efflux which in heterozygous state results in a relatively small reduction of HDL (less than 30% decrease compared to the normal values) explaining the lack of atherosclerosis (Frikke-Schmidt et al., 2008). Login to comment