The function of CD226 (CD226 molecule, ENSG00000150637) is as follows. Cell surface receptor that plays an important role in the immune system, particularly in intercellular adhesion, lymphocyte signaling, cytotoxicity and lymphokine secretion mediated by cytotoxic T-cells and NK cells (PubMed:8673704, PubMed:9712030). Functions as a costimulatory receptor upon recognition of target cells, such as virus- infected or tumor cells. Upon binding to its ligands PVR/CD155 or NECTIN2/CD112 on target cells, promotes the cytotoxic activity of NK cells and CTLs, enhancing their ability to kill these cells (PubMed:26755705, PubMed:31253644, PubMed:30591568). Mechanistically, phosphorylation by Src kinases such as LYN of FYN, enables binding to adapter GRB2, leading to activation of VAV1, PI3K and PLCG1. Promotes also activation of kinases ERK and AKT, as well as calcium fluxes (By similarity). {ECO:0000250|UniProtKB:Q8K4F0, ECO:0000269|PubMed:26755705, ECO:0000269|PubMed:30591568, ECO:0000269|PubMed:31253644, ECO:0000269|PubMed:8673704, ECO:0000269|PubMed:9712030}.