Required for gap junction formation, playing a role in anchoring the cytoskeletal component F-actin to the membrane of adjacent cells and thus facilitating the formation of gap junction channels in embryonic cells, muscle cells and neuronal cells (PubMed:33238150). Plays a role in maintaining gap junction activity to promote pharyngeal muscle contraction (PubMed:33238150). Interacts (via the intracellular domain) with F-actin; the interaction is required for anchoring F-actin at the membrane for gap junction formation. Partially co-localizes with F-actin at gap junctions between EA and EP endodermal precursor cells in embryos. Highly expressed in pharyngeal g1 and g2 gland cells, pharyngeal muscle cells and the unilateral GABAergic RIS interneuron (at protein level) (PubMed:21055481). Expressed in pm5 pharyngeal muscle cells and the nerve ring (PubMed:33238150). Expressed during all stages of larval development and adulthood (at protein level) (PubMed:21055481). Expressed during embryogenesis (PubMed:33238150). Expressed in EA and EP endodermal precursor cells at the 16-24 cell stage of embryogenesis (PubMed:33238150). RNAi-mediated knockdown results in abherrent inx-3-positive gap junction formation along the adjoining membranes of EA and EP endodermal precursor cells at the 16-24 cell stage of embryogenesis, and in adult pharyngeal muscles (PubMed:33238150). The inx-3-positive gap junctions are increased in number, are randomly positioned at irregular intervals on either the EA and EP cells and, although they are along the membrane, they are not on the membrane (PubMed:33238150). Furthermore, F-actin does not accumulate at the gap junction formation plaque in between the EA and EP adjoining membrane, but randomly forms patches along the membrane (PubMed:33238150). RNAi-mediated knockdown does not affect the expression of inx-3 (PubMed:33238150). RNAi-mediated knockdown impairs gap junction function in pharyngeal muscles which disrupts the synchronized muscle contraction between the pharyngeal metacorpus and terminal bulbs and thereby decreases the pharyngeal pumping rate (PubMed:33238150). RNAi-mediated knockdown in the nerve ring results in uncoordinated movements (also known as an unc phenotype), decreased locomotion and defective unc-9-positive gap junction formation and morphology (PubMed:33238150). Belongs to the neurexin family.