ABCA1 mediates high-affinity uptake of 25-hydroxycholesterol by membrane vesicles and rapid efflux of oxysterol by intact cells.
ABCA1 mediates high-affinity uptake of 25-hydroxycholesterol by membrane vesicles and rapid efflux of oxysterol by intact cells.
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ABCA1 介导膜囊泡对 25-羟基胆固醇的高亲和力摄取以及完整细胞对氧甾醇的快速流出。
DOI：
10.1152/ajpcell.00055.2006
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
R. Deeley
中科院分区：
文献类型：
--
作者：
S. Tam;Leo Mok;G. Chimini;M. Vasa;R. Deeley
ATP结合盒（ABC）转运蛋白ABCA 1通过介导磷脂和胆固醇的细胞外排，在胆固醇逆向转运中起关键作用。使用完整细胞的研究强烈表明，ABCA 1作为一个磷脂flopppase，但一直没有直接证明，该蛋白质是一个主要的活性固醇转运蛋白。利用昆虫Sf 21细胞的膜囊泡，我们发现ABCA 1介导ATP依赖的[（3）H]25-羟基胆固醇摄取，表观K（m）为0.7 μ M。与这种高表观亲和力一致，ABCA 1在人胚肾细胞中的表达既增加了25-羟基胆固醇的快速流出，又防止了氧化固醇介导的低密度脂蛋白（LDL）受体和3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶mRNA的抑制。野生型和ABCA 1（-/-）鼠成纤维细胞的比较表明，25-羟基胆固醇流出约5倍更快的野生型细胞。此外，ABCA 1表达诱导剂使野生型成纤维细胞而非ABCA 1（-/-）成纤维细胞的外排率进一步增加两倍。因此，在所采用的实验条件下，内源性ABCA 1是25-羟基胆固醇从野生型成纤维细胞流出的主要贡献者。来自体外研究的证据表明，氧固醇是参与细胞胆固醇流出和代谢的基因（包括ABCA 1基因）的有效诱导剂，以及参与胆固醇合成或摄取的基因的阻遏物。我们的观察提高了ABCA 1的氧化固醇流出可能有助于稳态机制的可能性，该机制既减弱了氧化固醇诱导的同源基因表达，又抑制了编码蛋白质的基因，如HMG-CoA还原酶和LDL受体。
ATP Binding Cassette (ABC) transporter, ABCA1, plays a pivotal role in reverse cholesterol transport by mediating the cellular efflux of phospholipid and cholesterol. Studies using intact cells strongly suggest that ABCA1 acts as a phospholipid floppase, but there has been no direct demonstration that the protein is a primary active sterol transporter. Using membrane vesicles from insect Sf21 cells, we found that ABCA1 mediated ATP-dependent uptake of [(3)H]25-hydroxycholesterol with an apparent K(m) of 0.7 muM. Consistent with this high apparent affinity, expression of ABCA1 in human embryonic kidney cells both increased rapid efflux of 25-hydroxcholesterol and prevented oxysterol-mediated repression of low-density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase mRNAs. Comparison of wild-type and ABCA1(-/-) murine fibroblasts indicates that 25-hydroxycholesterol is effluxed approximately 5-fold more rapidly by wild-type cells. In addition, the rate of efflux from the wild-type but not the ABCA1(-/-) fibroblasts is increased a further twofold by inducers of ABCA1 expression. Thus under the experimental conditions employed, endogenous ABCA1 is a major contributor to 25-hydroxycholesterol efflux from wild-type fibroblasts. Evidence from in vitro studies indicates that oxysterols are potent inducers of genes involved in cellular cholesterol efflux and metabolism, including the ABCA1 gene, and repressors of genes involved in cholesterol synthesis or uptake. Our observations raise the possibility that efflux of oxysterols by ABCA1 could contribute to a homeostatic mechanism, which both attenuates oxysterol-induced expression of its cognate gene and alleviates repression of genes encoding proteins, such as HMG-CoA reductase and LDL receptor.
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DOI：
10.1074/jbc.m003337200
发表时间：
2000-09
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
P. Costet;Yi Luo;Nan Wang;A. Tall
通讯作者：
P. Costet;Yi Luo;Nan Wang;A. Tall
影响因子：
16
作者：
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通讯作者：
Goldstein, JL
影响因子：
56.9
作者：
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通讯作者：
GOLDSTEIN, JL
DOI：
10.1073/pnas.90.24.11603
发表时间：
1993-12-15
影响因子：
11.1
作者：
HUA, XX;YOKOYAMA, C;WANG, XD
通讯作者：
WANG, XD
影响因子：
2.9
作者：
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通讯作者：
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