Mediates homophilic cell-cell adhesion in a Ca(2+)-independent manner. Also mediates heterophilic cell-cell adhesion with CADM3 and NECTIN3 in a Ca(2+)-independent manner. 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 (By similarity). 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. 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. 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. 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. Acts as a synaptic cell adhesion molecule and plays a role in the formation of dendritic spines and in synapse assembly. May be involved in neuronal migration, axon growth, pathfinding, and fasciculation on the axons of differentiating neurons. 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 (By similarity). Homodimer (via Ig-like V-type domain) (By similarity). Interacts with FARP1 (By similarity). Interacts (via Ig-like V-type domain) with CRTAM (via Ig-like V-type domain); the interaction competes with CRTAM homodimerization and CADM1 homodimerization (By similarity). 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) (PubMed:27756895). Interacts (via C-terminus) with MPP3 (via PDZ domain) (By similarity). Interacts (via C-terminus) with PALS2 (via PDZ domain) (By similarity). Localized to the basolateral plasma membrane of epithelial cells in gall bladder. 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. Belongs to the nectin family.