The small GTPases Rab are key regulators in vesicle trafficking (PubMed:23395371). Essential for maintaining the integrity of endosome-trans-Golgi network structure (PubMed:23395371). Together with LRRK2, plays a role in the retrograde trafficking pathway for recycling proteins, such as mannose 6 phosphate receptor (M6PR), between lysosomes and the Golgi apparatus in a retromer-dependent manner (PubMed:23395371). Recruits LRRK2 to the Golgi apparatus and stimulates LRRK2 kinase activity (By similarity). Regulates also neuronal process morphology in the intact central nervous system (CNS) (PubMed:23395371). Interacts with LRRK2. Colocalizes with GM130 at the Golgi apparatus (By similarity). Colocalizes with dynamic tubules emerging from and retracting to the Golgi apparatus (By similarity). Colocalizes with TGN46 at the trans-Golgi network (TGN) (By similarity). Colocalized with LRRK2 along tubular structures emerging from Golgi apparatus (PubMed:23395371). Expressed predominantly in kidney and much less in brain, heart, muscle, fat, liver, spleen, adrenal gland, ovary, thymus and lung. Not expressed in testis and intestine. Belongs to the small GTPase superfamily. Rab family.