Nectin4/PRR4, a new afadin-associated member of the nectin family that trans-interacts with Nectin1/PRR1 through V domain interaction

Nectins are adhesion molecules that participate in the organization of epit helial and endothelial junctions and serve as receptors for herpes simplex virus entry. They belong to the immunoglobulin superfamily, are homologues of the poliovirus receptor (PVR/CD155), and were also named poliovirus rece ptor-related (PRR) proteins. We identify a new member of the nectin family named nectin4. Peptide sequences of human and murine nectin4 share 92% iden tity, and as for other members, the ectodomain is made of three immunoglobu lin-like domains of V, C, C types. In contrast to other nectin molecules, d etection of nectin4 transcripts is mainly restricted to placenta in human t issues. Expression is broader in mouse, and interestingly nectin4 is detect ed at days 11, 15, and 17 during murine embryogenesis. Nectin4 interacts wi th afadin, a F-actin-associated molecule, via its carboxyl-terminal cytopla smic sequence. Both molecules co-localize at cadherin-based adherens juncti ons in the MDCKII epithelial cell line. Nectins are homophilic adhesion mol ecules, and recently heterophilic interactions have been described between nectin3/nectin1 and nectin3/nectin2. We confirmed these trans-interactions and also described nectin3 as the PVR/CD155 ligand. By means of several app roaches, we report on the identification of nectin4 as a new ligand for nec tin1. First, a soluble chimeric recombinant nectin4 ectodomain (nectin4-Fc) trans-interacts with cells expressing nectin1 but not with cells expressin g nectin2, nectin3, or PVR/CD155. Conversely, nectin1-Fc binds to cells exp ressing nectin4. Second, nectin1-Fc precipitates nectin4 expressed in COS c ells. Third, reciprocal in vitro physical interactions were detected betwee n nectin4-Fc and nectin1-Fc. The nectin4-Fc/nectin4-Fc interaction was dete cted suggesting that nectin4 exhibits both homophilic and heterophilic prop erties. Using the same approaches we demonstrate, for the first time, that the V domain of nectin1 acts as a major functional region involved in trans -heterointeraction with nectin4 and also nectin3.