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LET-502/ROCK Regulates Endocytic Recycling by Promoting Activation of RAB-5 in a Distinct Subpopulation of Sorting
Wenjuan Zhang1, Shimin Wang2, Chao Yang2
1Department of Biochemistry and Molecular Biology, School of Basic Medicine and the Collaborative Innovation Center for Brain Science, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030 Hubei, China; Department of Pathology, Maternal and Child Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430070 Hubei, China.
Abstract:
To explore the mechanism of Rab5/RAB-5 activation during endocytic recycling, we perform a genome-wide RNAi screen and identify a recycling regulator, LET-502/ROCK. LET-502 preferentially interacts with RAB-5(GDP) and activates RABX-5 GEF activity toward RAB-5, presumably by disrupting the self-inhibiting conformation of RABX-5. Furthermore, we find that the concomitant loss of LET-502 and another CED-10 effector, TBC-2/RAB-5-GAP, results in an endosomal buildup of RAB-5, indicating that CED-10 directs TBC-2-mediated RAB-5 inactivation and re-activates RAB-5 via LET-502 afterward. Then, we compare the functional position of LET-502 with that of RME-6/RAB-5-GEF. Loss of LET-502-RABX-5 module or RME-6 leads to diminished RAB-5 presence in spatially distinct endosome groups. We conclude that in the intestine of C. elegans, RAB-5 resides in discrete endosome subpopulations. Under the oversight of CED-10, LET-502 synergizes with RABX-5 to revitalize RAB-5 on a subset of endosomes in the deep cytosol, ensuring the progress of basolateral recycling.
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