Small GTPase which cycles between an active GTP-bound and an inactive GDP-bound state (PubMed:15907487, PubMed:16034420). Involved in protein transport (PubMed:29425100). Plays a role in vesicular traffic. Mediates VEGFR2 endosomal trafficking to enhance VEGFR2 signaling (PubMed:29425100). Acts as a regulator of platelet alpha-granule release during activation and aggregation of platelets (By similarity). GTP + H2O = GDP + H(+) + phosphate Interacts with SGSM1, SGSM2 and SGSM3 (By similarity). Interacts with RAB11FIP1, RABEP1, ZFYVE20 and RUFY1 (PubMed:10698684, PubMed:11786538, PubMed:11788822, PubMed:14617813, PubMed:15280022, PubMed:16034420). Interacts (membrane-bound form) with NDRG1; the interaction involves NDRG1 in vesicular recycling of E-cadherin (PubMed:17786215). Interacts (in GTP-bound form) with GRIPAP1 (via N-terminus) (PubMed:20098723). Interacts with RABEP1 and RBSN (PubMed:20098723). Does not interact with HPS4 (By similarity). Interacts with RABEP2; this interaction may mediate VEGFR2 cell surface expression (PubMed:29425100). Generally associated with membranes. Cytoplasmic when phosphorylated by CDK1. Phosphorylated by CDK1 kinase during mitosis. Serotonylation of Gln-72 by TGM2 during activation and aggregation of platelets leads to constitutive activation of GTPase activity. Belongs to the small GTPase superfamily. Rab family. It is uncertain whether Met-1 or Met-6 is the initiator.