Fielding P E, Fielding C J
Department of Medicine, University of California, San Francisco 94143-0130, USA.
Biochemistry. 1996 Nov 26;35(47):14932-8. doi: 10.1021/bi9613382.
Free cholesterol (FC) is selectively internalized from low-density lipoprotein (LDL) by confluent fibroblast monolayers (Fielding & Fielding (1995) Biochemistry 34, 14237-14244). The kinetics of transport of LDL-derived 3H-FC within the cell were studied by density-gradient ultracentrifugal fractionation and in terms of the effects of inhibitors of endocytosis and intracellular transport. By these criteria, the initial uptake of LDL-FC was mediated by the cell-surface clathrin-coated pits. FC label then appeared in clathrin-coated dense vesicles. Uncoating of clathrin from these vesicles led to the appearance of label in a light density fraction and, subsequently, in an intermediate density fraction coincident with protein markers of the trans-Golgi network in these cells. 3H-FC was finally transported to the plasma membrane via a temperature-sensitive, probably microtubule-dependent pathway. These data are consistent with a role for the trans-Golgi network as an intermediate compartment in intracellular FC transport. They provide further evidence of a role for cell-surface caveolae in FC efflux.
汇合的成纤维细胞单层可从低密度脂蛋白（LDL）中选择性内化游离胆固醇（FC）（菲尔丁和菲尔丁，《生物化学》，1995年，第34卷，第14237 - 14244页）。通过密度梯度超速离心分级分离，并结合内吞作用和细胞内运输抑制剂的作用，研究了细胞内LDL衍生的3H - FC的运输动力学。根据这些标准，LDL - FC的初始摄取是由细胞表面网格蛋白包被的小窝介导的。然后，FC标记出现在网格蛋白包被的致密小泡中。这些小泡上的网格蛋白脱衣导致标记物出现在低密度组分中，随后出现在与这些细胞中反式高尔基体网络的蛋白质标记物一致的中密度组分中。3H - FC最终通过一条温度敏感的、可能依赖微管的途径转运到质膜。这些数据与反式高尔基体网络作为细胞内FC运输中间区室的作用一致。它们进一步证明了细胞表面小窝在FC流出中的作用。
