Role of the plasma membrane in cholesterol esterification in rat hepatoma cells.
Role of the plasma membrane in cholesterol esterification in rat hepatoma cells.
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发表时间：
1993-07
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通讯作者：
Yvonne LangeSB;F. Strebel;Theodore L. Steckn
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作者：
Yvonne LangeSB;F. Strebel;Theodore L. Steckn
通过培养的大鼠肝癌细胞检查用于酯合成的胆固醇的来源。胆固醇的合成和纯化活动与RNA以高浮力密度共分布，推测是在粗面内质网（RER）中。胆固醇质量在粗面内质网中检测不到，粗面内质网中合成的胆固醇转移到细胞表面的能力比其酯化作用大100倍以上。类似地，从摄入的细胞内脂蛋白释放的胆固醇基本上全部在细胞表面回收。细胞膜含有约87%的细胞胆固醇，为粗面内质网中的酯化提供的胆固醇是新生胆固醇的100倍以上。胆固醇的供应是细胞匀浆中酯化反应的限速因素。完整细胞中质膜胆固醇的氧化降低了分离株中的酰基辅酶A：胆固醇酰基转移酶活性。最后，胆固醇在肝癌细胞质膜是一个更好的底物在体外酯化比成纤维细胞质膜，红细胞血影，或脂质体。我们的结论是，水平的饱和酰基辅酶A：胆固醇酰基转移酶，控制主要通过质膜和粗面内质网之间的双向运动的基板，起着重要的作用，在调节胆固醇酯化。
The source of the cholesterol used for ester synthesis by cultured rat hepatoma cells was examined. The activities synthesizing and esterifying cholesterol co-distributed with RNA at a high buoyant density, presumably in the rough endoplasmic reticulum (RER). Cholesterol mass was undetectable in the RER, and the transfer of cholesterol synthesized in the RER to the cell surface was more than 100 times greater than was its esterification. Similarly, essentially all of the cholesterol liberated from ingested intracellular lipoproteins was recovered at the cell surface. The plasma membranes, which contained approximately 87% of cell cholesterol, provided > 100 times more cholesterol for esterification in the RER than did nascent cholesterol. The supply of cholesterol was rate-limiting for esterification in cell homogenates. Prior oxidation of plasma membrane cholesterol in intact cells reduced the acyl-CoA:cholesterol acyltransferase activity in isolates proportionately. Finally, cholesterol in hepatoma plasma membranes was a far better substrate for in vitro esterification than was that in fibroblast plasma membranes, red blood cell ghosts, or liposomes. We conclude that the level of saturation of acyl-CoA:cholesterol acyltransferase, controlled principally through the bidirectional movement of the substrate between plasma membranes and RER, plays a major role in the regulation of cholesterol esterification.