RILP is required for the proper morphology and function of late endosomes
RILP is required for the proper morphology and function of late endosomes
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DOI：
10.1242/jcs.017301
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发表时间：
2007-11-01
影响因子：
4
通讯作者：
Stenmark, Harald
中科院分区：
文献类型：
--
作者：
Progida, Cinzia;Malerod, Lene;Stenmark, Harald
信号传导受体（例如表皮生长因子（EGF）受体（EGFR））的溶酶体降解是终止细胞信号传导的重要机制。这种降解涉及将泛素化受体内体分选到多囊泡内体 (MVE) 的腔内囊泡 (ILV) 中，沿着微管移动与核周溶酶体融合。 Rab7 相互作用的溶酶体蛋白 RILP 在这方面很有趣，因为它与 Vps22（也称为 EAP30）和 Vps36（也称为 EAP45）（转运 II (ESCRT-II) 所需的内体分选复合物的亚基）以及动力蛋白-动力蛋白运动复合物相互作用。由于之前的 RILP 功能研究都是基于其过度表达，因此我们在这里询问 RILP 是否是受体内吞运输所必需的。 RILP 的消耗导致四种晚期内体分子、溶血双磷脂酸、Lamp1、CD63 和阳离子非依赖性甘露糖-6-磷酸受体的水平升高。电子显微镜显示，RILP 耗尽细胞的内体在形态上与正常晚期内体不同，并且 ILV 含量大幅降低。与 Vps22 耗尽的细胞一样，配体介导的 EGFR 降解在 RILP 耗尽的细胞中受到强烈抑制，其中发现内吞的 EGFR 在早期内体中积累。相比之下，转铁蛋白受体的内吞作用和再循环在 RILP 耗尽的细胞中正常发生。这些结果表明，RILP 与 ESCRT 蛋白一样，是 MVE 的生物发生和 EGFR 的降解运输所必需的，但不是转铁蛋白受体通过早期内体运输所必需的。我们认为 RILP 可能通过动力蛋白介导的运动来协调 MVE 的生物发生。
Lysosomal degradation of signalling receptors such as the epidermal growth factor (EGF) receptor (EGFR) is an important mechanism for termination of cell signalling. Such degradation involves the endosomal sorting of ubiquitylated receptors into intralumenal vesicles (ILVs) of multivesicular endosomes (MVEs) that move along microtubules to fuse with perinuclear lysosomes. The Rab7-interacting lysosomal protein RILP is interesting in this context as it interacts with Vps22 (also known as EAP30) and Vps36 (also known as EAP45), subunits of the endosomal sorting complex required for transport II (ESCRT-II), as well as with the dynein-dynactin motor complex. Because previous functional studies of RILP have been based on its overexpression, we have asked here whether RILP is required for endocytic trafficking of receptors. Depletion of RILP caused elevated levels of four late-endosomal molecules, lyso-bisphosphatidic acid, Lamp1, CD63 and cation-independent mannose-6-phosphate receptors. Electron microscopy showed that endosomes of RILP-depleted cells were morphologically distinct from normal late endosomes and had a strongly reduced content of ILVs. As in Vps22-depleted cells, ligand-mediated degradation of EGFRs was strongly inhibited in RILP-depleted cells, in which endocytosed EGFRs were found to accumulate in early endosomes. By contrast, endocytosis and recycling of transferrin receptors occurred normally in RILP-depleted cells. These results establish that RILP, like the ESCRT proteins, is required for biogenesis of MVEs and degradative trafficking of EGFRs but not for trafficking of transferrin receptors through early endosomes. We propose that RILP might coordinate the biogenesis of MVEs with dynein-mediated motility.