The small GTPases Rab are key regulators of intracellular membrane trafficking, from the formation of transport vesicles to their fusion with membranes. Rabs cycle between an inactive GDP-bound form and an active GTP-bound form that is able to recruit to membranes different set of downstream effectors directly responsible for vesicle formation, movement, tethering and fusion. Required for basolateral endocytic recycling, the return of macromolecules and fluid from endosomes to the plasma membrane, in polarized epithelial cells of the intestine upstream of rme-1. Involved in the formation of the endosomal tubular network that is required for basolateral recycling of clathrin-independent endocytic cargo such as daf-4 in the intestine. Required for the recruitment of cnt-1 effector to endosomal membranes in the intestinal epithelium, which is important for the regulation of levels of endosomal phosphatidylinositol-4,5-bisphosphate, a key phosphoinositide in membrane traffic, and for the recruitment of endosomal membrane-bending proteins, rme-1 and sdpn-1. Recruits the rab-5 GTPase-activating protein tbc-2 to endosomes where it then inactivates rab-5 resulting in removal of rab-5 from membranes, which is necessary for cargo transport from early endosomes to recycling endosomes in the basolateral intestine. Regulates recycling of synaptic membrane AMPA glutamate receptor, glr-1, from intracellular endosomal compartments back to synapses in a cholesterol-dependent endocytosis pathway functioning after clathrin-independent endocytosis in command interneurons. Regulates neuropeptide release from dense core vesicles (DCVs) of cholinergic motoneurons in cooperation with rab-5. They reciprocally recruite each other's inactivating GAP molecule leading to local exclusion of one or the other rab protein at the Golgi-endosomal interphase at an essential stage during DCV sorting. Regulates membrane trafficking of membranes and dendrite proteins from the Golgi and/or endosomal compartments to plasma membrane during dendrite morphogenesis together with the exocyst complex in the multi-dendritic PVD sensory neurons acting in a cell-autonomous manner and requiring its GTPase activity. Functions cell-autonomously together with the exocyst complex to regulate dendrite morphogenesis and anterior-posterior patterning of the PVD neurons dendritic arbor by balancing the anterograde and retrograde transport via molecular motors unc-116 (kinesin heavy chain) and dhc-1 (dynein heavy chain) to appropriately transport branching factors, such as dma-1, to the specific subcellular regions of the developing dendrite in its GTPase activity-dependent manner.
