Lin Xiaosi, Yang Ting, Wang Shicong, Wang Zhen, Yun Ye, Sun Lixiang, Zhou Yunhe, Xu Xiaohui, Akazawa Chihiro, Hong Wanjin, Wang Tuanlao
School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, Fujian, China, 361005.
Department of Biophysics and Biochemistry, Graduate School of Health Sciences, Tokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-Ku, Tokyo 113-8519, Japan.
Sci Rep. 2014 Dec 2;4:7282. doi: 10.1038/srep07282.
The HOPS complex serves as a tethering complex with GEF activity for Ypt7p in yeast to regulate late endosomal membrane maturation. While the role of HOPS complex is well established in yeast cells, its functional and mechanistic aspects in mammalian cells are less well defined. In this study, we report that RILP, a downstream effector of Rab7, interacts with HOPS complex and recruits HOPS subunits to the late endosomal compartment. Structurally, the amino-terminal portion of RILP interacts with HOPS complex. Unexpectedly, this interaction is independent of Rab7. VPS41 subunit of HOPS complex was defined to be the major partner for interacting with RILP. The carboxyl-terminal region of VPS41 was mapped to be responsible for the interaction. Functionally, either depletion of VPS41 by shRNA or overexpression of VPS41 C-terminal half retarded EGF-induced degradation of EGFR. These results suggest that interaction of RILP with HOPS complex via VPS41 plays a role in endocytic trafficking of EGFR.
HOPS复合物作为酵母中Ypt7p的具有鸟嘌呤核苷酸交换因子（GEF）活性的拴系复合物，用于调节晚期内体膜成熟。虽然HOPS复合物在酵母细胞中的作用已得到充分证实，但其在哺乳动物细胞中的功能和机制方面仍不太明确。在本研究中，我们报道Rab7的下游效应器RILP与HOPS复合物相互作用，并将HOPS亚基募集到晚期内体区室。在结构上，RILP的氨基末端部分与HOPS复合物相互作用。出乎意料的是，这种相互作用不依赖于Rab7。HOPS复合物的VPS41亚基被确定为与RILP相互作用的主要伙伴。VPS41的羧基末端区域被定位为负责这种相互作用。在功能上，通过短发夹RNA（shRNA）耗尽VPS41或过表达VPS41的C末端一半都会延迟表皮生长因子（EGF）诱导的表皮生长因子受体（EGFR）降解。这些结果表明，RILP通过VPS41与HOPS复合物的相互作用在EGFR的内吞运输中发挥作用。
