Guanine nucleotide exchange factor (GEF) which activates RAB21 and possibly RAB28 (, ). Promotes the exchange of GDP to GTP, converting inactive GDP-bound Rab proteins into their active GTP-bound form (, ). In response to starvation-induced autophagy, activates RAB21 which in turn binds to and regulates SNARE protein VAMP8 endolysosomal transport required for SNARE-mediated autophagosome-lysosome fusion . Acts as an adapter for the phosphatase MTMR2 (By similarity). Increases MTMR2 catalytic activity towards phosphatidylinositol 3,5-bisphosphate and to a lesser extent towards phosphatidylinositol 3-phosphate (By similarity).
Subcellular locations: Cytoplasm, Cytoplasm, Perinuclear region, Membrane, Endosome membrane, Cell projection, Axon
Associated with membranes . Localizes to vacuoles in hypo-osmotic conditions (By similarity). Membrane localization is likely to be mediated via its interaction with MTMR2 (By similarity).
Widely expressed. Expressed in spinal cord.