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 hypodermal P-cell nuclear positioning (PubMed:23150597). Together with toca-2, 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 (PubMed:19798448). Interacts with cdc-42 and (via SH3 domain) with wve-1 (PubMed:25775511). Co-localizes with ajm-1 at cell junctions (PubMed:19798448). Co-localizes with toca-2, rme-1, cdc-42 and wve-1 on recycling endosomes (PubMed:25775511). Expressed in the germline and specifically in the gonads. Ubiquitously expressed in developing embryos. Defective endocytosis by occytes characterized by either reduced or non-detectable yolk protein in the oocytes and by an accumulation of aggregated yolk in the pseudocoelomatic space (PubMed:19798448). This is more pronounced in the double knockout with toca-2 where nearly 100% of animals display this phenotype (PubMed:19798448). Double knockout mutants with toca-2 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). Double knockown with unc-84 results in defective hypodermal P-cell nuclear positioning with nuclei failing to migrate during larval development and a reduced number of GABA neurons (PubMed:23150597). Belongs to the FNBP1 family.