Stein O, Friedman G, Chajek-Shaul T, Halperin G, Olivecrona T, Stein Y
Biochim Biophys Acta. 1983 Feb 7;750(2):306-16. doi: 10.1016/0005-2760(83)90033-4.
Unilamellar liposomes prepared from purified phospholipids (phosphatidylcholine, phosphatidylethanolamine or sphingomyelin) and labeled cholesteryl linoleyl ether were used to study lipoprotein lipase-catalyzed transfer of cholesteryl ester into cells in culture. In mesenchymal rat heart cell cultures, the transfer of cholesteryl linoleyl ether and cholesteryl linoleate was similar and related to the activity of endogenously produced lipoprotein lipase. In human skin fibroblasts transfer of labeled cholesteryl linoleyl ether was proportional to the concentration of milk lipoprotein lipase added to the incubation medium. Liposomes prepared from phosphatidylcholine or phosphatidylethanolamine were much better donors of cholesteryl ether to normal and apolipoprotein E-B receptor-negative fibroblasts and to endothelial cells than those prepared from sphingomyelin. Lysophosphatidylcholine was formed during incubation with milk lipoprotein lipase but was not considered to be directly responsible for the lipoprotein lipase-catalyzed transfer of cholesteryl ether. This conclusion was drawn because in the absence of lipoprotein lipase addition of lysophosphatidylcholine to liposomes, or almost complete phospholipolysis by phospholipase A2, did not result in the transfer of cholesteryl linoleyl ether from liposomes to cells. Attachment of lipoprotein lipase to the cell surface was mandatory for the transfer of cholesteryl ether and could be prevented by heparin. High density apolipoprotein reduced also the transfer of cholesteryl linoleyl ether, even though it did not interfere with the binding of labeled milk lipoprotein lipase to cultured fibroblasts. The present results provide evidence that lipoprotein lipase, and not the products of phospholipid hydrolysis, is the ligand for the non-apolipoprotein E-B receptor-mediated transfer of cholesteryl ester to cells.
由纯化的磷脂（磷脂酰胆碱、磷脂酰乙醇胺或鞘磷脂）制备并标记了胆固醇亚油酸酯的单层脂质体，被用于研究脂蛋白脂肪酶催化胆固醇酯向培养细胞中的转移。在大鼠间充质心脏细胞培养物中，胆固醇亚油酸酯和胆固醇亚油酸的转移情况相似，且与内源性产生的脂蛋白脂肪酶的活性相关。在人皮肤成纤维细胞中，标记的胆固醇亚油酸酯的转移与添加到孵育培养基中的乳脂蛋白脂肪酶的浓度成正比。由磷脂酰胆碱或磷脂酰乙醇胺制备的脂质体，作为胆固醇醚的供体，对正常和成载脂蛋白E-B受体阴性的成纤维细胞以及内皮细胞来说，比由鞘磷脂制备的脂质体要好得多。溶血磷脂酰胆碱在与乳脂蛋白脂肪酶孵育过程中形成，但不被认为直接负责脂蛋白脂肪酶催化的胆固醇醚转移。得出这一结论是因为在没有脂蛋白脂肪酶的情况下，向脂质体中添加溶血磷脂酰胆碱，或用磷脂酶A2几乎完全进行磷脂水解，都不会导致胆固醇亚油酸酯从脂质体转移到细胞中。脂蛋白脂肪酶附着于细胞表面是胆固醇醚转移所必需的，并且可以被肝素阻止。高密度载脂蛋白也降低了胆固醇亚油酸酯的转移，尽管它并不干扰标记的乳脂蛋白脂肪酶与培养的成纤维细胞的结合。目前的结果提供了证据，表明脂蛋白脂肪酶而非磷脂水解产物，是胆固醇酯通过非载脂蛋白E-B受体介导向细胞转移的配体。
