A two-step mechanism for free cholesterol and phospholipid efflux from human vascular cells to apolipoprotein A-1
A two-step mechanism for free cholesterol and phospholipid efflux from human vascular cells to apolipoprotein A-1
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DOI：
10.1021/bi0004192
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发表时间：
2000-11-21
期刊：
影响因子：
2.9
通讯作者：
Fielding, CJ
中科院分区：
文献类型：
--
作者：
Fielding, PE;Nagao, K;Fielding, CJ
体内的平滑肌和内皮细胞处于静止状态，但暴露在高水平的脂蛋白脂中。磷脂(PL)和游离胆固醇(FC)外流维持动态平衡。高密度脂蛋白的主要蛋白载脂蛋白A-1(apo A-1)在平滑肌细胞(SMC)高表达ABC-1转运蛋白，格列本脲依赖的PL和Fc外流至载脂蛋白A-1(apo A-1)。钒酸和冈田酸对FC外流有抑制作用，而PL外流不受抑制。磷脂酰胆碱是两种细胞转运的主要磷脂酰胆碱。这种转运蛋白对磷脂酰丝氨酸外流的刺激作用仅轻微增加。脐静脉和主动脉内皮细胞很少表达ABC-1mRNA，这些细胞也不促进载脂蛋白A-1的存在而促进PL或FC外流。为了探讨ABC-L依赖的脂质外流的机制，将载脂蛋白A-1与未标记的SMC或成纤维细胞一起预先孵育，然后将条件培养液转移到内皮细胞。此培养基能催化内皮细胞外流Fc，但不能外流PL。这种Fc外排对格列本脲具有抗性，但被冈田酸和钒酸盐抑制。这些数据表明，ABC-L依赖的PL外流先于Fc外流到apoA-1，并且apoA-1与PL的复合体是FC的更好的受体。钒酸和冈田酸抑制FC而不是PL外流，表明这些转运涉及不同的机制。
Smooth muscle and endothelial cells in vivo are quiescent yet exposed to high levels of lipoprotein lipids. Phospholipid (PL) and free cholesterol (FC) efflux maintain homeostasis. Smooth muscle cells (SMC) expressed high levels of ABC-1 transporter mRNA, and glyburide-dependent PL and FC efflux to apolipoprotein A-1 (apo A-1), the major protein of high-density Lipoprotein. FC efflux was inhibited by vanadate and okadaic acid, while PL efflux was not. Phosphatidylcholine was the major PL transferred by both cell types. Stimulation of phosphatidylserine efflux, redistributed within the membrane by this transporter, was only minimally increased. Umbilical vein and aortic endothelial cells expressed little ABC-1 mRNA, nor did these cells promote either PL or FC efflux in response to the presence of apo A-1. To investigate the mechanism of ABC-l-dependent lipid efflux from these cells, apo A-1 was preincubated in the presence of unlabeled SMC or fibroblasts, and the conditioned medium was then transferred to endothelial cells. This medium catalyzed the efflux of FC but not of PL from endothelial cells. Such FC efflux was resistant to glyburide but inhibited by okadaic acid and vanadate. The data suggest that ABC-l-dependent PL efflux precedes FC efflux to apo A-1 and that the complex of apo A-1 and PL is a much better acceptor of FC than apo A-1 itself. Inhibition of FC but not PL efflux by vanadate and okadaic acid suggests these transfers involve different mechanisms.