TY - JOUR TI - Endocytic recycling and regulation of the early-to-recycling endosome transition DO - https://doi.org/doi:10.7282/T3V126SR PY - 2015 AB - Endocytic recycling is the process by which cells return internalized cargos and receptors back to plasma membrane. Efficient recycling of cargos requires ordered transport of cargos from early endosome to recycling endosome. This is mainly achieved through the coordination of small GTPase RAB-5 and RAB-10. The small GTPase RAB-5 is a master regulator of cargo sorting at the early endosome and RAB-10 is a key resident of the recycling endosome. Countercurrent cascades of GEFs and GAPs for Rab proteins have been proposed to mediate Rab conversion, a process in which early acting Rabs are inactivated by later acting Rabs. Here we demonstrate that a downstream Rab protein, RAB-10, binds to and recruits a RAB-5 GAP, TBC-2, onto endosomes to inactivate the upstream Rab, RAB-5. This process is critical for proper relay of cargos from RAB-5 controlled early endosomes to RAB-10 regulated recycling endosomes. Lack of TBC-2 disrupted RAB-5/RAB-10 interaction and caused accumulation of recycling cargo hTAC-GFP in a malfunctioned hybrid early-recycling endosome compartment. Furthermore, our study showed that this cargo transition process from early to recycling endosome also requires the concerted effort by a BAR-domain protein AMPH-1, which acts as a binding partner and a contributor to the recruitment of TBC-2 on endosomes. In addition, the C. elegans Rac1 homolog CED-10 can also bind and recruit it to endosomes. Taken together, our worked showed that RAB-10, AMPH-1 and CED-10 act in a concerted manner and recruits TBC-2 to inactivate RAB-5. These interactions are essential for early-to-recycling endosome transition and endocytic recycling. We further demonstrated here that RAB-10, recruits CNT-1, the C. elegans homolog of mammalian ACAP1 and ACAP2 (Arf6 GTPase-activating proteins) to inactivate ARF-6 and downregulate endosomal PI(4,5)P2, a key phosphoinositide in membrane traffic. KW - Cell and Developmental Biology KW - Cell membranes KW - Biological transport LA - eng ER -