Second immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3), nectin-4 (poliovirus receptor related protein 4) and similar proteins
Ig2_Nectin-3-4_like: domain similar to the second immunoglobulin (Ig) domain of nectin-3 (also known as poliovirus receptor related protein 3) and nectin-4 (poliovirus receptor related protein 4). Nectin-3 and nectin-4 belong to the nectin family comprised of four transmembrane glycoproteins (nectins-1 through 4). Nectins are synaptic cell adhesion molecules (CAMs) which facilitate adhesion and signaling at various intracellular junctions. Nectins form homophilic cis-dimers, followed by homophilic and heterophilic trans-dimers involved in cell-cell adhesion. Nectin-2 and nectin-3 localize at Sertoli-spermatid junctions where they form heterophilic trans-interactions between the cells that are essential for the formation and maintenance of the junctions and for spermatid development. Nectin-3 has also been shown to form a heterophilic trans-interaction with nectin-1 in ciliary epithelia, establishing the apex-apex adhesion between the pigment and non-pigment cell layers. Nectin-4 has recently been identified in several types of breast carcinoma and can be used as a histological and serological marker for breast cancer.