Rab2 is a conserved Rab GTPase with a well-established role in secretory pathway function and phagocytosis. Here we demonstrate that Drosophila Rab2 is recruited to late endosomal membranes, where it controls the fusion of LAMP-containing biosynthetic carriers and lysosomes to late endosomes. In contrast, the lysosomal GTPase Gie/Arl8 is only required for late endosome-lysosome fusion, but not for the delivery of LAMP to the endocytic pathway. We also find that Rab2 is required for the fusion of autophagosomes to the endolysosomal pathway, but not for the biogenesis of lysosome-related organelles. Surprisingly, Rab2 does not rely on HOPS-mediated vesicular fusion for recruitment to late endosomal membranes. Our work suggests that Drosophila Rab2 is a central regulator of the endolysosomal and macroautophagic/autophagic pathways by controlling the major heterotypic fusion processes at the late endosome.
Keywords: Autophagy; Drosophila; HOPS complex; LAMP; Rab proteins; Rab2; late endosomes; lysosomes; membrane trafficking.