Guanine-nucleotide exchange factor (GEF) for members of the Arf family of small GTPases involved in trafficking in the early secretory pathway; its GEF activity initiates the coating of nascent vesicles via the localized generation of activated ARFs through replacement of GDP with GTP (By similarity). Also, plays a role in receptor-mediated endocytosis in oocytes and endosomal trafficking (PubMed:23840591). Involved in vesicle retrograde transport from the ERGIC and cis-Golgi compartments to the endoplasmic reticulum (ER) (PubMed:23840591). Plays a role in maintaining mitochondrial morphology, network organization and function (PubMed:25190516). May be required for the basolateral cell membrane localization of the serine threonine protein kinase sgk-1 in intestinal cells (PubMed:26115433). RNAi-mediated knockdown at the L1 larval stage causes cuticle rupture, mostly through the vulva, and results in lethality in 50 to 80% of animals upon reaching adulthood (PubMed:23840591). Most surviving animals that reach adulthood are sterile due to embryonic lethality, and in over 90% of surviving animals there is an accumulation of vacuole-like structures in the body cavity (PubMed:23840591). The few larvae that hatch have severe cuticle formation abnormalities (PubMed:23840591). RNAi-mediated knockdown at the L2 or L3 larval stage, results in reduced lethality in response to oxidative stress induced by paraquat compared to wild-type (PubMed:25190516). RNAi-mediated knockdown at the L2 or L3 larval stage, results in enlarged mitochondria which are interconnected by thin membrane tubes in maturing oocytes (PubMed:25190516). RNAi-mediated knockdown at the L4 larval stage, results in impaired body bend movements, and disorganization of the mitochondrial network and increased connections between mitochondria in body wall muscle cells (PubMed:25190516). RNAi-mediated knockdown at the L3 or L4 larval stage, results in the normal production and fertilization of oocytes, but 60 to 70% of the fertilized oocytes are embryonic lethal (PubMed:23840591). Arrested eggs from these animals have disintegrated egg shells, which results in a mass of cells and membranes in the gonad (PubMed:23840591). While 30% of fertilized oocytes display defects in meiosis, with the extrusion of the second polar body during anaphase II often failing (PubMed:23840591). Furthermore, 30% of fertilized oocytes have cytokinesis defects (PubMed:23840591). RNAi-mediated knockdown at the L3 or L4 larval stage, results in defects in Golgi apparatus organization with small Golgi apparatus foci aggregating in large structures around the nuclear membrane and cell periphery in oocytes, and small vesicles accumulating at the endoplasmic reticulum-Golgi interface (PubMed:23840591). RNAi-mediated knockdown at the L3 or L4 larval stage, results in endoplasmic reticulum morphology defects with the absence of endoplasmic reticulum lumen in oocytes (PubMed:23840591). RNAi-mediated knockdown at the L3 or L4 larval stage, results in defective cav-1 transport from the Golgi apparatus to the plasma membrane in oocytes, and an accumulation of the yolk protein vit-2 in intestinal cells and in the body cavity (PubMed:23840591). RNAi-mediated knockdown at the L3 or L4 larval stage also results in defects in the endosomal pathway with reduced expression of the early endosomal protein rab-5 in the intestine (PubMed:23840591). RNAi-mediated knockdown results in the mis-localization of the serine threonine protein kinase sgk-1 in intestinal cells (PubMed:26115433).