Meta-Biol

• Pathways

RAB18 is a highly conserved RAB GTPase with roles in Golgi to ER trafficking, lipid droplet formation and the regulation of secretory granules and peroxisomes (Dejgaard et al, 2008; Gerondopoulos et al, 2014; Martin et al, 2005; Ozeki et al, 2005; Vazquez-Martinez et al, 2007; Gronemeyer et al, 2013). RAB18 is recruited to the ER membrane by the RAB18 GEF complex RAB3GAP1:RAB3GAP2, a complex that was initially identified and characterized for its GAP activity towards RAB3 (Gerondopoulos et al, 2013; Fukui et al, 1997; Nagano et al, 1998; reviewed in Ishida et al, 2016). Interaction of RAB18:GDP with its GEF promotes release of GDP, allowing GTP to bind, and precludes the interaction of RAB18 with GDI and CHM proteins. Mutations in RAB18, RAB3GAP1 or RAB3GAP2 are associated with Warburg Micro syndromes, characterized by ocular and neurological abnormalities (Handley and Aligianis, 2013; reviewed in Handley and Aligianis, 2012).