RILP interacts with VPS22 and VPS36 of ESCRT-II and regulates their membrane recruitment

RILP is emerging as a key regulator of late endocytic pathway by functioning as a downstream effector of activated Rab7 and Rab34, while ESCRT-I-->ESCRT-II-->ESCRT-III machinery acts in sorting proteins to the multivesicular body (MVB) initiated at the early/sorting endosome. We show here that the early machinery is integrated with the late machinery through a novel regulatory loop in which RILP interacts with VPS22 and VPS36 of ESCRT-II to mediate their membrane recruitment. The N-terminal and C-terminal half of RILP mediate interaction with VPS22 and VPS36, respectively. Overexpression of RILP leads to enlarged and clustered MVBs marked by lysobisphosphatidic acid (LBPA). In addition, RILP or its C-terminal fragment causes a retardation of sorting internalized EGF to the degradation route at the level of sorting endosomes marked by EEA1. We propose that RILP-->ESCRT-II serves as a regulatory/feedback loop to govern the coordination of early and late parts of the endocytic pathway.