ATP-binding cassette transporter A1 contains a novel C-terminal VFVNFA motif that is required for its cholesterol efflux and ApoA-I binding activities
ATP-binding cassette transporter A1 contains a novel C-terminal VFVNFA motif that is required for its cholesterol efflux and ApoA-I binding activities
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DOI：
10.1074/jbc.m409848200
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发表时间：
2004-11-12
影响因子：
4.8
通讯作者：
Freeman, MW
中科院分区：
文献类型：
--
作者：
Fitzgerald, ML;Okuhira, K;Freeman, MW
载脂蛋白A-I刺激细胞胆固醇和磷脂流出是由ATP结合盒转运蛋白A1（ABCA 1）的活性介导的。患有丹吉尔病的个体在这种转运蛋白中具有功能丧失突变，这些突变已被证明有助于阐明其活性。在这里，我们分析了一个突变，删除了最后46个残基的2261个氨基酸的转运蛋白（Delta46），并消除其脂质流出。由于C末端的最后四个氨基酸代表了一个假定的PDZ结合基序，我们最初的特点是缺失突变体只缺乏这些残基。虽然检测到脂质流出的中度下降，但这种下降并不像在Delta46突变体中观察到的那样深刻。随后对ABCA1 C末端的系统分析揭示了一个新的高度保守的基序（VFVNFA），它是脂质流出所必需的。该基序的改变存在于ABCA家族的一些但不是所有成员中，并不能阻止转运蛋白转运至质膜，但确实消除了其与apoA-I的结合。通过将ABCA 4或ABCA 7的C末端替换为内源性末端而产生的嵌合转运蛋白表明，ABCA 1可以在没有其PDZ结合基序的情况下刺激胆固醇流出，但在没有VFVNFA基序的情况下不能。当含有VFVNFA序列的肽被引入ABCA 1表达细胞时，ABCA 1介导的脂质流出也被显著抑制。这些结果表明ABCA 1的C-末端VFVNFA基序对于其脂质流出活性是必需的。这些数据还表明，该基序参与了ABCA家族成员之间可能共享的新型蛋白质-蛋白质相互作用。
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.