Plays a role in protein trafficking, actin organization and embryonic morphogenesis (PubMed:19798448). Potentially acts as cdc-42 effector (PubMed:25775511). May play a role in egg laying (PubMed:19798448). Together with toca-1, is required for protein trafficking regulating yolk protein clathrin-mediated endocytosis by oocytes during oogenesis and retrograde recycling and the sorting of recycling endosome cargo proteins such as mig-14 (PubMed:19798448, PubMed:25775511). Also, together with toca-2, controls the distribution of actin at cell junctions (PubMed:19798448, PubMed:26578656). Interacts (via SH3 domain) with wsp-1 and abi-1 (PubMed:19798448). Interacts with cdc-42 and (via SH3 domain) with wve-1 (PubMed:25775511). Diffuse cytoplasmic localization (PubMed:19798448). Localizes to the rachis, which is the central core of the cytoplasm connecting developing oocytes in the syncytial gonad (PubMed:19798448). Co-localizes with toca-1 on recycling endosomes (PubMed:25775511). Ubiquitously expressed in developing embryos. Double knockout with toca-1 results in nearly 100% of mutants with defective endocytosis by oocytes characterized by either reduced or non-detectable yolk protein in the oocytes and by an accumulation of aggregated yolk protein in the pseudocoelomatic space. Double knockout mutants with toca-1 also produce 20% fewer eggs compared to wild-type animals and there is some embryonic lethality whereby the dying embryos display defective morphogenesis including failed epidermal enclosure with extruding gut cells and increased width of the intestinal lumen (PubMed:19798448). This perhaps results from failed intercalation and migration of hypodermal cells and irregular protein trafficking as indicated by an accumulation of the cell junction protein ajm-1 and diffuse localization of actin at cell junctions (PubMed:19798448, PubMed:26578656). These double mutants also demonstrate defective endosomal sorting of recycling cargo proteins such as mig-14 (PubMed:25775511). Belongs to the FNBP1 family.