ABCMdb

ABCA1 p.Thr1512Met

Predicted by SNAP2:	A: D (63%), C: D (53%), D: D (80%), E: D (71%), F: D (75%), G: D (75%), H: D (71%), I: D (71%), K: D (75%), L: D (71%), M: D (63%), N: D (71%), P: D (80%), Q: D (71%), R: D (80%), S: D (59%), V: D (66%), W: D (71%), Y: D (75%),
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, N: D, P: D, Q: D, R: D, S: D, V: D, W: D, Y: D,

[switch to compact view]
Comments [show]

None has been submitted yet.

Publications
[hide] An ABCA1 truncation shows no dominant negative eff... Biochem Biophys Res Commun. 2011 Jun 10;409(3):400-5. Epub 2011 May 7. Sorrenson B, Suetani RJ, Bickley VM, George PM, Williams MJ, Scott RS, McCormick SP
An ABCA1 truncation shows no dominant negative effect in a familial hypoalphalipoproteinemia pedigree with three ABCA1 mutations.
Biochem Biophys Res Commun. 2011 Jun 10;409(3):400-5. Epub 2011 May 7., [PMID:21575609]

Abstract [show]
The ATP binding cassette transporter (ABCA1) A1 is a key determinant of circulating high density lipoprotein cholesterol (HDL-C) levels. Mutations in ABCA1 are a major genetic contributor to low HDL-C levels within the general population. Following the finding of three different ABCA1 mutations, p.C978fsX988, p.T1512M and p.N1800H in a subject with hypoalphalipoproteinemia, we aimed to establish whether the p.C978fsX988 truncation exerted a dominant negative effect on the full-length ABCA1 alleles within family members as has been reported for other ABCA1 truncations. Characterisation of the p.C978fsX988 mutant in transfected HEK 293 cells showed it to be expressed as a GFP fusion protein but lacking in cholesterol efflux function. This was in keeping with results from cholesterol efflux assays in the fibroblasts of p.C978fsX988 carriers which also showed impaired efflux. Allele- specific quantification of p.C978fsX988 mRNA and analysis of ABCA1 protein levels in the fibroblasts of p.C978fsX988 heterozygotes showed negligible levels of mRNA and protein expression. There was no evidence of a dominant negative effect on wildtype or p.N1800H protein levels. We conclude that in the case of the p.C978fsX988 truncated mutant a lack of expression precludes it from having a dominant negative effect.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
2 Following the finding of three different ABCA1 mutations, p.C978fsX988, p.T1512M and p.N1800H in a subject with hypoalphalipoproteinemia, we aimed to establish whether the p.C978fsX988 truncation exerted a dominant negative effect on the full-length ABCA1 alleles within family members as has been reported for other ABCA1 truncations. Login to comment
29 In this study, we characterised a pedigree with three different ABCA1 mutations; p.N1800H, p.C978fsX988 and p.T1512M. Login to comment
30 The p.N1800H is a common ABCA1 mutation known to impair function [1,6,11,12]. Login to comment
31 The p.C978fsX988 and p.T1512M mutations were recently reported but were not characterised with respect to segregation, expression or function in the case of the p.C978fsX988 mutation [13]. Login to comment
32 Here we show that the p.C978fsX988 and p.T1512M mutations are on the same allele and that the p.C978fsX988 protein is dysfunctional. Login to comment
33 This situation gave us the unique opportunity to test the effect of a short ABCA1 truncation on the expression and function of both the wildtype and the p.N1800H ABCA1 alleles. Login to comment
72 The T1512 primer was used to amplify the wildtype and p.N1800H alleles and the M1512 primer to amplify the p.C978fsX988/p.T1512M allele. Login to comment
84 Sequencing showed the proband (I:1) was heterozygote for three mutations; p.C978fsX988 (c.2934delT), p.T1512M (c.4535C > T) and p.N1800H (c.5398A > C). Login to comment
87 The daughter (II:2) was heterozygous for the N1800H mutation and the son (II:1) heterozygous for the p.C978fsX988 and p.T1512M mutations making it apparent that the p.C978fsX988 and p.T1512M mutations were on the same allele. Login to comment
109 The proband, a compound heterozygote for the p.C978fsX988, p.T1512M and p.N1800H mutations, exhibited a low HDL-C level (0.23 mmol/L) but showed no signs of Tangier disease. Login to comment
110 Segregation of alleles within the family showed the p.C978fsX988 and p.T1512M mutations to be on the same allele making the p.T1512M mutation effectively redundant. Login to comment
111 As few studies have characterised the effect of truncated ABCA1 alleles [9,10,17], this family gave us a unique opportunity to test the effect of a short truncated allele on both the full-length wildtype and p.N1800H alleles. Login to comment
121 The p.C978fsX988/ p.T1512M and p.N1800H alleles are represented by grey and black shading respectively. Login to comment
73 The T1512 primer was used to amplify the wild-type and p.N1800H alleles and the M1512 primer to amplify the p.C978fsX988/p.T1512M allele. Login to comment
85 Sequencing showed the proband (I:1) was heterozygote for three mutations; p.C978fsX988 (c.2934delT), p.T1512M (c.4535C > T) and p.N1800H (c.5398A > C). Login to comment
88 The daughter (II:2) was heterozygous for the N1800H mutation and the son (II:1) heterozygous for the p.C978fsX988 and p.T1512M mutations making it apparent that the p.C978fsX988 and p.T1512M mutations were on the same allele. Login to comment
122 The p.C978fsX988/ p.T1512M and p.N1800H alleles are represented by grey and black shading respectively. Login to comment

[hide] Identification and characterization of novel loss ... Atherosclerosis. 2010 Dec;213(2):492-8. Epub 2010 Aug 26. Candini C, Schimmel AW, Peter J, Bochem AE, Holleboom AG, Vergeer M, Dullaart RP, Dallinga-Thie GM, Hovingh GK, Khoo KL, Fasano T, Bocchi L, Calandra S, Kuivenhoven JA, Motazacker MM
Identification and characterization of novel loss of function mutations in ATP-binding cassette transporter A1 in patients with low plasma high-density lipoprotein cholesterol.
Atherosclerosis. 2010 Dec;213(2):492-8. Epub 2010 Aug 26., [PMID:20880529]

Abstract [show]
OBJECTIVES: The current literature provides little information on the frequency of mutations in the ATP-binding cassette transporter A1 (ABCA1) in patients with low high-density lipoprotein cholesterol (HDL) levels that are referred to the clinic. In 78 patients with low plasma levels of HDL cholesterol that were referred to our clinic, we routinely screened for ABCA1 gene mutations and studied the functionality of newly identified ABCA1 missense mutations. METHODS: The coding regions and exon-intron boundaries of the ABCA1 gene were sequenced in 78 subjects with HDL cholesterol levels below the 10th percentile for age and gender. Novel mutations were studied by assessing cholesterol efflux capacity (using apolipoprotein A-I as acceptor) after transient expression of ABCA1 variants in BHK cells. RESULTS: Sixteen out of 78 patients (21%) were found to carry 19 different ABCA1 gene variants (1 frameshift, 2 splice-site, 4 nonsense and 12 missense variation) of which 14 variations were novel. Of three patients with homozygous mutations and three patients having compound heterozygous mutations only one patient presented with the clinical characteristics of Tangier Disease (TD) in the presence of nearly complete HDL deficiency. Seven out of eight newly identified ABCA1 missense mutations were found to exhibit a statistically significant loss of cholesterol efflux capacity. CONCLUSION: This study shows that one out of five patients who are referred to our hospital because of low HDL cholesterol levels have a functional ABCA1 gene mutation. It is furthermore demonstrated that in vitro studies are needed to assess functionality of ABCA1 missense mutations.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
61 Eight novel missense variations [c.299C > G (p.S100C), c.1724A > G (p.D575G), c.1779C > G (p.F593L), c.3167T > C (p.L1056P), c.3757G > A (p.E1253K), c.4535C > T (p.T1512M), c.5573T > C (p.V1858A), c.5821T > C (p.C1941R)] were introduced into this chimeric construct by site-directed mutagenesis using Stratagene QuikChange XL site-directed mutagenesis kit according to manufacturer`s instructions (La Jolla, CA, USA). Login to comment
76 Patients (gender, age) Amino acida (nucleotidea ) change TC TG LDL-c HDL-c Clinical manifestations of TD CVD Other relevant clinical data Homozygotes Patient 1 (female, 42) p.L1056P (c.3167T > C) 2.4 0.9 1.99 <0.10 Absent CAD Thrombocytopenia Patient 2 (male, 40) p.Wl747X (c.5240G > A) 1.76 1.93 0.52 0.1-0.3 Neuropathy, splenomegaly, thrombocytopenia Mild stenosis (20-30%) of coronary arteries None Patient 3 (male, 55) p.F593L (c.1779C > G) 4.4 1.4 3.6 <0.10 Absent CAD None p.E1253K (c.3757G > A) Compound heterozygotes Patient 4 (female, 63) p.Q1038X (c.3112C > T) 6.68 2.72 5.4 <0.10 Absent None None p.N1800H (c.5398A > C) [32] Patient 5 (female, 28) p.T1512M (c.4535C > T) 4.42 1.83 3.46 0.1 Absent None None p.N1800H (c.5398A > C) [32] p.C978fsX988 (c.2934delT) Patient 6 (female, 17) p.D575G (c.1724A > G) 4.96 2.84 4.35 <0.10 Absent None DM1 p.C1941R(c.5821T > C) Heterozygotes Patient 7 (male, 42) p.S100C (c.299C > G) 8.5 8.7 4.3 0.3 N.A. None None Patient 8 (male, 58) p.E1172D (c.3516G > C) [33] 6.4 2.7 4.1 0.9 N.A. None None Patient 9 (male, 35) p.S1181F (c.3542C > T) [17] 2.9 0.31 1.88 0.88 N.A. None None Patient 10 (male, 48) p.C1477R (c.4429T > C) [13] 2.01 1.4 0.92 0.46 N.A. CAD None Patient 11 (male, 68) p.V1858A (c.5573T > C) 4.9 3.78 2.41 0.75 N.A. CAD None Patient 12 (female, 36) p.N1800H (c.5398A > C) [32] 4.6 1.2 4 <0.10 N.A. None DM2, obesity Patient 13 (male, 67) p.R282X (c.844C > T) [34] 3.2 1.21 2.14 0.51 N.A. None DM2 Patient 14 (female, 42) p.W424X (c.1272G > A) 2.07 1.04 1.39 0.21 N.A. None None Patient 15 (female, 52) N.A. - (IVS11 - 1G > A) 5.51 3.51 3.28 0.56 N.A. None Hypothyroidism, hypertension Patient 16 (female, 54) N.A. - (IVS48 + 2T > C) 3.29 1.92 1.94 0.49 N.A. None DM2, hypertension a Nomenclature based on guidelines of Human Genome Variation Society. Login to comment
89 In ABCA1, we identified 14 novel and 5 known genetic variations in 16 subjects including one frameshift (p.C978fsX988), 2 splice-site (IVS11-1G > C and IVS48 + 2T > C), 4 nonsense (p.R282X, p.W424X, p.Q1038X, p.Wl747X) and 12 missense variations (p.S100C, p.D575G, p.F593L, p.L1056P, p.E1172D, p.S1181F, p.E1253K, p.C1477R, p.T1512M, p.N1800H, p.V1858A, p.C1941R). Login to comment
94 From eight novel missense variations identified in our cohort, one is localized in the first transmembrane domain (p.S100C), two in the first large extracellular loop (p.D575G and p.F593L), two in the first Nuclear Binding Domain (p.L1056P and p.E1253K), one in the second large extracellular loop (p.T1512M), one in the extracellular region, close to the plasma membrane (p.V1858A) and one is localized in the C-terminal domain (p.C1941R). Login to comment
98 Four out of eight mutations were predicted to be probably damaging (p.S100C, p.D575G, p.T1512M, p.C1941R), two as possibly damaging (p.F593L and p.L1056P) and two were described as benign (p.E1253K and p.V1858A) by PolyPhen. Login to comment
110 Fig. 2 shows that the ABCA1-p.S100C, p.D575G, p.F593L, p.L1056P, p.E1253K, p.T1512M, p.C1941R mutant proteins all had a significantly reduced capacity to efflux cholesterol to apo A-I compared to wild-type ABCA1 which is in line with the low HDL cholesterol levels of the individuals in whom the mutations were identified. Login to comment
148 The ABCA1-p.F593L and ABCA1-p.D575G mutations are located in the first large extracellular loop, while ABCA1-p.T1512M is located in the second extracellular loop. Login to comment

[hide] Functional rescue of mutant ABCA1 proteins by sodi... J Lipid Res. 2013 Jan;54(1):55-62. doi: 10.1194/jlr.M027193. Epub 2012 Oct 20. Sorrenson B, Suetani RJ, Williams MJ, Bickley VM, George PM, Jones GT, McCormick SP
Functional rescue of mutant ABCA1 proteins by sodium 4-phenylbutyrate.
J Lipid Res. 2013 Jan;54(1):55-62. doi: 10.1194/jlr.M027193. Epub 2012 Oct 20., [PMID:23087442]

Abstract [show]
Mutations in the ATP-binding cassette transporter A1 (ABCA1) are a major cause of decreased HDL cholesterol (HDL-C), which infers an increased risk of cardiovascular disease (CVD). Many ABCA1 mutants show impaired localization to the plasma membrane. The aim of this study was to investigate whether the chemical chaperone, sodium 4-phenylbutyrate (4-PBA) could improve cellular localization and function of ABCA1 mutants. Nine different ABCA1 mutants (p.A594T, p.I659V, p.R1068H, p.T1512M, p.Y1767D, p.N1800H, p.R2004K, p.A2028V, p.Q2239N) expressed in HEK293 cells, displaying different degrees of mislocalization to the plasma membrane and discrete impacts on cholesterol efflux, were subject to treatment with 4-PBA. Treatment restored localization to the plasma membrane and increased cholesterol efflux function for the majority of mutants. Treatment with 4-PBA also increased ABCA1 protein expression in all transfected cell lines. In fibroblast cells obtained from low HDL-C subjects expressing two of the ABCA1 mutants (p.R1068H and p.N1800H), 4-PBA increased cholesterol efflux without any increase in ABCA1 expression. Our study is the first to investigate the effect of the chemical chaperone, 4-PBA on ABCA1 and shows that it is capable of restoring plasma membrane localization and enhancing the cholesterol efflux function of mutant ABCA1s both in vitro and ex vivo. These results suggest 4-PBA may warrant further investigation as a potential therapy for increasing cholesterol efflux and HDL-C levels.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
16 Nine different ABCA1 mutants (p.A594T, p.I659V, p.R1068H, p.T1512M, p.Y1767D, p.N1800H, p.R2004K, p.A2028V, p.Q2239N) expressed in HEK293 cells, displaying different degrees of mislocalization to the plasma membrane and discrete impacts on cholesterol efflux, were subject to treatment with 4-PBA. Login to comment
53 The Pearson`s correlation coefficient between the GFP and AlexaFluor594 of the ABCA1 mutations were previously identified in low HDL-C subjects and included three uncharacterized mutations, p.I659V, p.R2004K, and p.A2028V (18) and three variants, p.R1068H, p.T1512M, and p.N1800H, known to have reduced localization and cholesterol efflux (19, 20). Login to comment
85 4-PBA rescues mutant ABCA1 localization and improves cholesterol efflux function in transfected HEK293 cells 4-PBA treatment was applied to the six uncharacterized ABCA1 mutants as well as to three mutants that we have previously shown to have reduced cholesterol efflux function, p.R1068H (19), p.T1512M (20), and p.N1800H (20, Fig. 1). Login to comment
109 Upon 4-PBA treatment, efflux function was significantly increased relative to the untreated level for the p.R1068H, p.T1512M, p.Y1767D, p.N1800H, p.R2004K, and p.A2028V mutants (Fig. 3B). Login to comment
112 Treatment with 4-PBA induced a significant increase in colocalization for the p.A594T, p.R1068H, p.T1512M, p.Y1767D, p.N1800H, and p.R2004K mutants. Treatment with 4-PBA did not affect the colocalization of the wild-type ABCA1-GFP protein (supplementary Fig. II). 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.

Comments [show]

None has been submitted yet.

Sentences [show]
No. Sentence Comment
65 Mutations introduced by overlap extension PCR using Pfu AD DNA polymerase in ABCA1 included S100C, W590S, F593L, N935S, T929I, C1477R, T1512M, R2081W, and P2150L. 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
230 By contrast, the T1512M mutation in ECD2 and P2150L in the C-terminal segment exhibited ATPase activity similar to the WT protein. 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
234 As shown in Fig. 8, A and B, the Fl-PC flippase activity of the ABCA1 mutants and the Fl-PE flippase activity of ABCA4 mutants have a similar profile with the ABCA1 variants C1477R, T1512M, and P2150L and corresponding ABCA4 variants C1502R, T1537M, and P2180L showing transport activities ranging from 60 to 80% of the WT protein and the other mutants showing reduced activity in the range of 20-40% of the WT protein. Login to comment
295 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (20-30% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT). 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
233 By contrast, the T1512M mutation in ECD2 and P2150L in the C-terminal segment exhibited ATPase activity similar to the WT protein. Login to comment
235 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
237 As shown in Fig. 8, A and B, the Fl-PC flippase activity of the ABCA1 mutants and the Fl-PE flippase activity of ABCA4 mutants have a similar profile with the ABCA1 variants C1477R, T1512M, and P2150L and corresponding ABCA4 variants C1502R, T1537M, and P2180L showing transport activities ranging from 60 to 80% of the WT protein and the other mutants showing reduced activity in the range of 20-40% of the WT protein. Login to comment
298 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (20-30% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT). 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
228 By contrast, the T1512M mutation in ECD2 and P2150L in the C-terminal segment exhibited ATPase activity similar to the WT protein. Login to comment
293 The ABCA1/ABCA4 mutants in the ECD1 (S100C/S100P, W590S/ W605S, and F593L/F608L) displayed the lowest activities (2030% WT), whereas those in the ECD2 (C1477R/C1502R and T1512M/T1537M) and the P2150L/P2180L mutants in the C terminus showed the highest activities (60-100% WT). Login to comment