Specificity
Homologous to the poliovirus receptor (PVR/CD155), the nectin immunoglobulin superfamily comprises four known isoforms (-1, -2, -3, and -4). The ectodomain of nectin family members comprises three Ig-like domains (V, C, C). Nectins localize at the adherens junctions (AJ) in epithelial and endothelial cells where they serve as adhesion molecules. Actin-based AJs play a role in mechanical adhesion, cellular morphogenesis and cellular differentiation. Nectin associates with the actin cytoskeleton through its interaction with the actin filament-binding protein afadin. Nectin 4 and afadin co-localize at cadherin-based adherens junctions in MDCKII epithelial cells. Nectin 4 and nectin 3 share a common binding region in the V domain of Nectin 1 and thus compete for Nectin 1 binding. The Nectin 3/4 binding domain maps to the C-C strands of the V domain of Nectin 1. Unlike other nectins, which are more widely expressed, Nectin 4 is mainly expressed in the placenta.
