Small GTPase which cycles between active GTP-bound and inactive GDP-bound states. In its active state, binds to a variety of effector proteins to regulate homeostasis of late endocytic pathway, including endosomal positioning, maturation and secretion (By similarity). Plays a role in NTRK2/TRKB axonal anterograde transport by facilitating the association of NTRK2/TRKB with KLC1 (By similarity). May be involved in targeting uroplakins to urothelial apical membranes (PubMed:14625374). GTP + H2O = GDP + H(+) + phosphate Regulated by guanine nucleotide exchange factors (GEFs) which promote the exchange of bound GDP for free GTP, GTPase activating proteins (GAPs) which increase the GTP hydrolysis activity, and GDP dissociation inhibitors which inhibit the dissociation of the nucleotide from the GTPase. Activated by GEFs such as DENND10. Interacts with SYTL2, SYTL4, MYRIP and MLPH. Interacts with RPH3A and RPH3A (By similarity). Interacts (GDP-bound form preferentially) with DENND10 (By similarity). Expressed at an extraordinary high level (0.1% of total protein) in urothelium. Belongs to the small GTPase superfamily. Rab family.