May play a role as scaffolding protein at cell-cell junctions. May regulate acid-induced ASIC3 currents by modulating its expression at the cell surface. Interacts through its WW 2 domain with SYNPO and through its PDZ 5 domain with ACTN4. Interacts with cytoplasmic domain of ADGRB1. Interacts via its WW domains with DRPLA (By similarity). Interacts with ESAM, LRP2 and CXADR (PubMed:15383320, PubMed:11274227, PubMed:15304526). Isoform 2 interacts with CTNNB1 (PubMed:10772923). Interacts through its PDZ 1 domain with NET1 (PubMed:11350080). Interacts with ASIC3 and AMOT (By similarity) (PubMed:15317815). Interacts with FCHSD2 (By similarity). Interacts with IGSF5/JAM4 and through its PDZ 2 and 3 domains with NPHS1 forming a tripartite complex (By similarity). Interacts with DDN. May interact (via PDZ domain) with RAPGEF2 (By similarity). Interacts with DLL1 (PubMed:15509766). Interacts with KCNJ10 and possibly with KCNJ10/KCNJ16 heterodimer; this interaction may facilitate KCNJ10/KCNJ16 potassium channel expression at the basolateral membrane in kidney tubular cells (By similarity). Interacts with PRRG4 (via cytoplasmic domain) (By similarity). Localizes to epithelial cells tight junctions. Additional isoforms seem to exist. Widely expressed, including kidney glomeruli.