Novel role of nectin: implication in the co-localization of JAM-A and claudin-1 at the same cell-cell adhesion membrane domain.

Tight junctions (TJs) are formed at the apical side of adherens junctions (AJs) in epithelial cells. Major cell adhesion molecules (CAMs) at TJs are JAM and claudin, whereas major CAMs at AJs are nectin and cadherin. We previously showed that nectin initially forms cell-cell adhesion and then recruits cadherin to the nectin-based cell-cell adhesion sites to form AJs, followed by the recruitment of JAM and claudin to the apical side of AJs to form TJs. We investigated the roles of nectin in the formation of TJs by expressing various combinations of CAMs in L fibroblasts with no TJs or AJs. Co-expression of one of the AJ CAMs and one of the TJ CAMs formed two separate cell-cell adhesion membrane domains (CAMDs). Co-expression of nectin-3 and E-cadherin formed the same CAMD, but co-expression of JAM-A and claudin-1 did not form the same CAMD. Co-expression of JAM-A and claudin-1 with nectin-3, but not E-cadherin, made them form the same CAMD, which was separated from the nectin-based CAMD. Nectin-3 required afadin, a nectin- and F-actin-binding protein, for this ability. In conclusion, nectin plays a novel role in the co-localization of JAM and claudin at the same CAMD.