Protein transport. Probably involved in regulated exocytosis (By similarity). Interacts with RIMS1, RIMS2, RPH3A, RPH3AL and RAB3IP (By similarity). Interacts with CHM and CHML; phosphorylation at Thr-86 disrupts these interactions (PubMed:29125462). Interacts with MADD (via uDENN domain); the GTP-bound form is preferred for interaction (By similarity). Highly expressed in granulocytes of peripheral blood. Constitutively expressed at low levels in all hematopoietic cell lines investigated. Activated in myeloid differentiation. 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.