Protein transport. Probably involved in vesicular traffic (By similarity). May be involved in the insulin-induced exocytosis of glut4-containing vesicles in adipocytes. Interacts with RIMS1, RIMS2, RPH3A, RPH3AL and RAB3IP (PubMed:11431472, PubMed:12578829). Interacts with CHM and CHML; phosphorylation at Thr-86 disrupts these interactions (By similarity). Interacts with MADD (via uDENN domain); the GTP-bound form is preferred for interaction (PubMed:18849981). Predominantly expressed in the adipocyte tissue, but is also expressed in several other organs including skin, spleen, heart and lung. Phosphorylation of Thr-86 in the switch II region by LRRK2 prevents the association of RAB regulatory proteins, including CHM and CHML. Belongs to the small GTPase superfamily. Rab family.