Plays a role in endocytosis and intracellular protein transport (PubMed:19759177, PubMed:27718357). Mediates trafficking of TF from early endosomes to recycling endosomes. Required for NGF-mediated endocytosis of NTRK1, and subsequent neurite outgrowth. Binds GTP and GDP and has low GTPase activity. Alternates between a GTP-bound active form and a GDP-bound inactive form (By similarity). Binds EEA1 (By similarity). Interacts (in its GTP-bound form) with RINL (By similarity). Interacts directly with ZFYVE20 (PubMed:16034420). Interacts (in its GTP-bound form) with RABGEF1 (PubMed:19759177). Recruited to phagosomes containing S.aureus or M.tuberculosis. Detected in brain and heart, and at lower levels in lung and spleen. Belongs to the small GTPase superfamily. Rab family.