Provides, together with MAGI1, an adhesion machinery at tight junctions, which may regulate the permeability of kidney glomerulus and small intestinal epithelial cells. Mediates calcium-independent homophilic cell adhesion. In testis, it may function as a cell adhesion molecule rather than a tight-junction protein. It may participate in the adhesion between spermatogonia-spermatogonia, spermatogonia-Sertoli cells, and Sertoli cells-Sertoli cells (By similarity). Interacts with MAGI1 at tight junctions, forms a tripartite complex with NPHS1. Interacts with LNX1 isoform 2 via its PDZ 2 domain, it may also interact with other isoforms containing this domain. A protein of the expected size has been detected by antibody binding and Western blot in at least one of the analyzed tissues or cells. Belongs to the immunoglobulin superfamily.