Raft-mediated trafficking of apical resident proteins occurs in both direct and transcytotic pathways in polarized hepatic cells: Role of distinct lipid microdomains
Raft-mediated trafficking of apical resident proteins occurs in both direct and transcytotic pathways in polarized hepatic cells: Role of distinct lipid microdomains
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DOI：
10.1091/mbc.e02-08-0528
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发表时间：
2003-02-01
影响因子：
3.3
通讯作者：
Hoekstra, D
中科院分区：
文献类型：
--
作者：
Slimane, TA;Trugnan, G;Hoekstra, D
在极化的肝细胞中，介导驻留的顶端胆小管蛋白流动的途径和分子原理尚未得到解决。在此，我们已经调查了顶端贩运的糖基磷脂酰肌醇连接和两个单一的跨膜结构域蛋白一方面，和两个多位蛋白在极化HepG 2细胞的其他。我们证明，前者到达胆小管膜通过间接的转胞途径，而多面体蛋白直接到达顶膜后，高尔基体出口。最重要的是，基于胆固醇的脂质微结构域（“筏”）在任一途径中起作用，并且蛋白质分选到这些结构域中发生在生物合成途径中，主要在高尔基体中。有趣的是，直接途径中涉及的筏是Lubrol WX不溶性的，但Triton X-100可溶，而间接途径中的筏是Lubrol WX和Triton X-100都不溶性的。此外，而胆固醇消耗改变筏洗涤剂不溶性在间接途径，而不影响顶端排序，蛋白质分选错误发生在直接途径，而不影响筏不溶性。这些数据表明胆固醇是直接心尖通路中的交通方向决定参数。此外，筏-货物可能区分单跨膜锚与多跨膜锚，而不是筏本身（共同）决定分选途径。
In polarized hepatic cells, pathways and molecular principles mediating the flow of resident apical bile canalicular proteins have not yet been resolved. Herein, we have investigated apical trafficking of a glycosylphosphatidylinositol-linked and two single transmembrane domain proteins on the one hand, and two polytopic proteins on the other in polarized HepG2 cells. We demonstrate that the former arrive at the bile canalicular membrane via the indirect transcytotic pathway, whereas the polytopic proteins reach the apical membrane directly, after Golgi exit. Most importantly, cholesterol-based lipid microdomains ("rafts") are operating in either pathway, and protein sorting into such domains occurs in the biosynthetic pathway, largely in the Golgi. Interestingly, rafts involved in the direct pathway are Lubrol WX insoluble but Triton X-100 soluble, whereas rafts in the indirect pathway are both Lubrol WX and Triton X-100 insoluble. Moreover, whereas cholesterol depletion alters raft-detergent insolubility in the indirect pathway without affecting apical sorting, protein missorting occurs in the direct pathway without affecting raft insolubility. The data implicate cholesterol as a traffic direction-determining parameter in the direct apical pathway. Furthermore, raft-cargo likely distinguishing single vs. multispanning membrane anchors, rather than rafts per se (co)determine the sorting pathway.