Cholesterol efflux to apolipoprotein AI involves endocytosis and resecretion in a calcium-dependent pathway
Cholesterol efflux to apolipoprotein AI involves endocytosis and resecretion in a calcium-dependent pathway
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DOI：
10.1073/pnas.96.20.11358
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发表时间：
1999-09-28
影响因子：
11.1
通讯作者：
Smith, JD
中科院分区：
文献类型：
--
作者：
Takahashi, Y;Smith, JD
我们以前已经描述了cAMP介导的诱导胆固醇和磷脂流出的小鼠巨噬细胞RAW 264细胞系的无脂质载脂蛋白受体。这种胆固醇流出的诱导与载脂蛋白与细胞的结合和缔合增加有关。在本研究中，主要使用载脂蛋白AI（apeAI）作为受体，cAMP依赖性胆固醇流出载脂蛋白受体与apoAI结合包被的小窝，细胞摄取和切除。在细胞结合和洗涤后，在90分钟的追踪期间，58%的apoAI被切除。此外，在apoAI摄取和洗涤后，在没有额外受体的追踪期间观察到胆固醇流出。胆固醇流出部分阻断氯丙嗪和高渗介质，两种抑制剂包被小凹内吞作用。胆固醇流出apoAI被发现依赖于细胞外钙。通过将cAMP诱导期与apoAI追踪期暂时分开，发现在apoAI追踪期而不是cAMP诱导期需要钙。在缺乏钙的情况下，8-Br-cAMP介导的apoAI结合的诱导得以维持，但特异性apoAI细胞结合被抑制。这些数据与胆固醇流出到载脂蛋白的模型一致，该模型涉及钙依赖性内吞途径，然后再循环和随后从细胞释放新生脂蛋白颗粒。
We previously have described the cAMP-mediated induction of cholesterol and phospholipid efflux from the murine macrophage RAW264 cell line to lipid-free apolipoprotein accepters. This induction of cholesterol efflux is associated with increased binding and association of apolipoprotein to the cells. In the present study, using primarily apolipoprotein AI (apeAI) as the acceptor, cAMP-dependent cholesterol efflux to apolipoprotein accepters was associated with apoAI binding to coated pits, cellular uptake, and resecretion. After cell association and washing, 58% of the apoAI was resecreted during a 90-min chase period. In addition, after apoAI uptake and washing, cholesterol efflux was observed during a chase period without additional accepters. Cholesterol efflux was partially blocked by chlorpromazine and hypertonic media, two inhibitors of coated pit endocytosis. Cholesterol efflux to apoAI was found to depend on extracellular calcium. By temporally separating the cAMP induction phase from the apoAI chase phase, calcium was found to be required during the apoAI chase phase rather than during the cAMP induction period. In the absence of calcium the 8-Br-cAMP-mediated induction of apoAI binding was maintained, but the specific apoAI cellular association was inhibited. The data are consistent with a model for cholesterol efflux to apolipoproteins that involves a calcium-dependent endocytic pathway, followed by recycling and the subsequent release of the nascent lipoprotein particle from the cell.