Maintains epithelial barrier function by recruiting MARVELD2/tricellulin to tricellular tight junctions (tTJs) (PubMed:23239027). Crucial for normal hearing by maintaining the structural and functional integrity of tTJs, which are critical for the survival of auditory neurosensory HCs (PubMed:25217574). Mediates fatty acids and lipoproteins-stimulated CCK/cholecystokinin secretion in the small intestine (PubMed:23863714). In the inner ear, may regulate alternative pre-mRNA splicing via binding to TRA2A, TRA2B and SRSF1 (PubMed:28785060). Homooligomer (By similarity). Interacts with MARVELD2 and OCLN; the interaction is required to recruit MARVELD2 to tricellular contacts (PubMed:23239027). Interacts (via C-terminus) with TRA2A, TRA2B and SRSF1 (PubMed:28785060). Localizes to tricellular tight junctions (tTJs) between epithelial cells. Expressed in the vestibule and in hair cells and supporting cells of the cochlea. Expressed in epithelial tissues. Highly expressed in colon but also detected in small intestine, bladder and lung (PubMed:23239027). In colon, expressed in the upper portion of the crypts (at protein level) (PubMed:23239027). Expressed in CCK secretory cells of the proximal small intestine (at protein level) (PubMed:23863714). Expressed in the organ of Corti, stria vascularis, utricle and saccule of the inner ear (PubMed:23239027, PubMed:25217574). Expressed early in development. Mutant mice have early-onset severe deafness associated with a rapid degeneration of cochlear hair cells but have a normal endocochlear potential (PubMed:25217574). Mutants show no increase in plasma CCK levels after orogastric gavage with fatty acids (PubMed:23863714). Belongs to the immunoglobulin superfamily. LISCH7 family.