RAB15, Member RAS Oncogene Family (RAB15)

Wild-type rab15 and its constitutively active, GTP-bound mutant (Q67L) reduce fluid phase and receptor-mediated endocytosis without affecting the rate of recycling from early endosomal compartments. Inhibition of early endocytosis appears to be due to a reduction in the rate of homotypic early endosome fusion. Conversely, mutations that constitutively inactivate rab15 stimulate early endocytosis and the homotypic fusion of early endosomesin vitro. Unlike active forms of rab15, constitutively inactive rab15 mutants also affect recycling from early endosomal compartments. Moreover, the two constitutively inactive mutants, GDP-bound rab15-T22N and the non-nucleotide binding mutant rab15-N121I, differentially regulate the transit of fluid phase and receptor-mediated endocytic tracers through early/sorting endosomes.