The function of NECTIN3 (nectin cell adhesion molecule 3, Ensembl gene identifier ENSG00000177707) is as follows. Cell adhesion molecule that promotes cell-cell adhesion through heterophilic trans-interactions with nectins-like or other nectins, such as trans-interaction with NECTIN2 at Sertoli-spermatid junctions (PubMed:16216929). Trans-interaction with PVR induces activation of CDC42 and RAC small G proteins through common signaling molecules such as SRC and RAP1 (PubMed:16216929). Induces endocytosis- mediated down-regulation of PVR from the cell surface, resulting in reduction of cell movement and proliferation (PubMed:16216929). Involved in axon guidance by promoting contacts between the commissural axons and the floor plate cells (By similarity). Also involved in the formation of cell-cell junctions, including adherens junctions and synapses (By similarity). Promotes formation of checkerboard-like cellular pattern of hair cells and supporting cells in the auditory epithelium via heterophilic interaction with NECTIN1: NECTIN1 is present in the membrane of hair cells and associates with NECTIN3 on supporting cells, thereby mediating heterotypic adhesion between these two cell types (By similarity). Plays a role in the morphology of the ciliary body (By similarity). {ECO:0000250|UniProtKB:Q9JLB9, ECO:0000269|PubMed:16216929}.