Small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state (PubMed:14697203). Involved in protein transport. Plays a role in vesicular traffic. Mediates VEGFR2 endosomal trafficking to enhance VEGFR2 signaling (By similarity). Acts as a regulator of platelet alpha-granule release during activation and aggregation of platelets (PubMed:14697203). GTP + H2O = GDP + H(+) + phosphate Interacts with SGSM1, SGSM2 and SGSM3 (PubMed:17509819). Interacts with RAB11FIP1, RABEP1, ZFYVE20 and RUFY1 (PubMed:11172003). Interacts (membrane-bound form) with NDRG1; the interaction involves NDRG1 in vesicular recycling of E-cadherin. Interacts (in GTP-bound form) with GRIPAP1 (via N-terminus). Interacts with RABEP1 and RBSN (By similarity). Does not interact with HPS4 (By similarity). Does not interact with HPS4 (PubMed:20048159). Interacts with RABEP2; this interaction may mediate VEGFR2 cell surface expression (By similarity). Generally associated with membranes. Cytoplasmic when phosphorylated by CDK1. Expressed in the central nervous system, including cortex, cerebellum, midbrain and spinal cord, and in the kidney, lung, liver and spleen. Serotonylation of Gln-72 by TGM2 during activation and aggregation of platelets leads to constitutive activation of GTPase activity. Phosphorylated by CDK1 kinase during mitosis. Belongs to the small GTPase superfamily. Rab family. It is uncertain whether Met-1 or Met-6 is the initiator. Truncated N-terminus.