Mediates homophilic cell-cell adhesion in a Ca(2+)-independent manner (PubMed:12202822, PubMed:12799182, PubMed:12826663). Also mediates heterophilic cell-cell adhesion with CADM3 and NECTIN3 in a Ca(2+)-independent manner (PubMed:12826663). Interaction with CRTAM promotes natural killer (NK) cell cytotoxicity and interferon-gamma (IFN-gamma) secretion by CD8+ T-cells in vitro as well as NK cell-mediated rejection of tumors expressing CADM1 in vivo (PubMed:15811952). In mast cells, may mediate attachment to and promote communication with nerves (By similarity). CADM1, together with MITF, is essential for development and survival of mast cells in vivo (PubMed:15158462, PubMed:16605125). By interacting with CRTAM and thus promoting the adhesion between CD8+ T-cells and CD8+ dendritic cells, regulates the retention of activated CD8+ T-cell within the draining lymph node (PubMed:19752223). Required for the intestinal retention of intraepithelial CD4+ CD8+ T-cells and, to a lesser extent, intraepithelial and lamina propria CD8+ T-cells and CD4+ T-cells (PubMed:24687959). Interaction with CRTAM promotes the adhesion to gut-associated CD103+ dendritic cells, which may facilitate the expression of gut-homing and adhesion molecules on T-cells and the conversion of CD4+ T-cells into CD4+ CD8+ T-cells (PubMed:24687959). Acts as a synaptic cell adhesion molecule and plays a role in the formation of dendritic spines and in synapse assembly (PubMed:12202822, PubMed:23209303). May be involved in neuronal migration, axon growth, pathfinding, and fasciculation on the axons of differentiating neurons (PubMed:15707673). May play diverse roles in the spermatogenesis including in the adhesion of spermatocytes and spermatids to Sertoli cells and for their normal differentiation into mature spermatozoa (PubMed:12606335, PubMed:16612000). Homodimer (via Ig-like V-type domain) (By similarity). Interacts with FARP1 (PubMed:23209303). Interacts (via Ig-like V-type domain) with CRTAM (via Ig-like V-type domain); the interaction competes with CRTAM homodimerization and CADM1 homodimerization (PubMed:15811952, PubMed:15781451). Interacts (via C-terminus) with EPB41L3/DAL1 (By similarity). The interaction with EPB41L3/DAL1 may act to anchor CADM1 to the actin cytoskeleton (By similarity). Interacts (via C-terminus) with MPP2 (via PDZ domain) (By similarity). Interacts (via C-terminus) with MPP3 (via PDZ domain) (By similarity). Interacts (via C-terminus) with PALS2 (via PDZ domain) (PubMed:12826663). Localized to the basolateral plasma membrane of epithelial cells in gall bladder. Expressed dominantly in epithelial cells but not expressed in fibroblast cells (at protein level) (PubMed:12826663). Expressed in the T-cell area of lymph nodes, specifically in CD8+ and CD4- CD8- dendritic cells (at protein level) (PubMed:19752223). Expressed in CD8+ dendritic cells in the spleen (at protein level) (PubMed:19752223). Expressed in CD103+ dendritic cells in the small intestine lamina propria and mesenteric lymph nodes (at protein level) (PubMed:24687959). Expressed in brain, lung, kidney, testis, heart, spleen and liver, but not expressed in skeletal muscle (PubMed:12242005, PubMed:12606335, PubMed:12202822). Expressed in spermatogenic cells during early spermatogenesis. Expression increases in intermediate spermatogonia through to zygotene spermatocytes but becomes diminished in the steps from early pachytene spermatocytes through to round spermatids. After meiosis, expression reappears in spermatids and is present in elongating spermatids until spermiation. Not detected in Sertoli cells. The cytoplasmic domain appears to play a critical role in proapoptosis and tumor suppressor activity in NSCLC. N-glycosylated. Glycosylation at Asn-70 and Asn-104 promotes adhesive binding and synapse induction. Male mice are infertile, due to a defect at the spermatid stage of spermatogenesis, and show oligoasthenoteratozoospermia with almost no mature motile spermatozoa in the epididymis (PubMed:16382161, PubMed:16611999, PubMed:16612000). Heterozygous males and females and homozygous null females are fertile and have no overt developmental defects (PubMed:16382161, PubMed:16611999, PubMed:16612000). In the small intestine mucosa and under steady-state conditions, severe reduction in the number of intraepithelial CD4+ CD8+ T-cells and, partial reduction in the number of lamina propria and intraepithelial CD8+ and CD4+ T-cells (PubMed:24687959). Belongs to the nectin family.