ABCA1 p.Gln2215*
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[hide] Genetic etiology of isolated low HDL syndrome: inc... Arterioscler Thromb Vasc Biol. 2007 May;27(5):1139-45. Epub 2007 Feb 15. Kiss RS, Kavaslar N, Okuhira K, Freeman MW, Walter S, Milne RW, McPherson R, Marcel YL
Genetic etiology of isolated low HDL syndrome: incidence and heterogeneity of efflux defects.
Arterioscler Thromb Vasc Biol. 2007 May;27(5):1139-45. Epub 2007 Feb 15., [PMID:17303779]
Abstract [show]
OBJECTIVE: We have used a multitiered approach to identify genetic and cellular contributors to high-density lipoprotein (HDL) deficiency in 124 human subjects. METHODS AND RESULTS: We resequenced 4 candidate genes for HDL regulation and identified several functional nonsynonymous mutations including 2 in apolipoprotein A-I (APOA1), 4 in lecithin:cholesterol acyltransferase (LCAT), 1 in phospholipid transfer protein (PLTP), and 7 in the ATP-binding cassette transporter ABCA1, leaving 88% (110/124) of HDL deficient subjects without a genetic diagnosis. Cholesterol efflux assays performed using cholesterol-loaded monocyte-derived macrophages from the 124 low HDL subjects and 48 control subjects revealed that 33% (41/124) of low HDL subjects had low efflux, despite the fact that the majority of these subjects (34/41) were not carriers of dysfunctional ABCA1 alleles. In contrast, only 2% of control subjects presented with low efflux (1/48). In 3 families without ABCA1 mutations, efflux defects were found to cosegregate with low HDL. CONCLUSIONS: Efflux defects are frequent in low HDL syndromes, but the majority of HDL deficient subjects with cellular cholesterol efflux defects do not harbor ABCA1 mutations, suggesting that novel pathways contribute to this phenotype.
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No. Sentence Comment
71 0 2 4 6 8 10 m ock W T E1386Q C 1477F D 1706N S1731C N 1800H W 590L H 551D Q 2215X antibodybound (cpmx103 /mgcellprotein) 0 1 2 3 4 5 m ock W T E1386Q C 1477F D 1706N S1731C N 1800H W 590L H 551D Q 2215X apoA-Imediatedefflux(%)A B apoA-Imediatedefflux (%oftotalradioactivity) antibodybound (cpmx103/mgcellprotein) Figure 1.
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ABCA1 p.Gln2215* 17303779:71:0
status: NEW76 Q2215X is a truncation mutant and was used to demonstrate that the C terminus of ABCA1 is necessary for function, and therefore the 1851X mutant would also be nonfunctional.
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ABCA1 p.Gln2215* 17303779:76:0
status: NEW[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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No. Sentence Comment
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.
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ABCA1 p.Gln2215* 15347662:113:189
status: NEW