Role of nectin in formation of E-cadherin-based adherens junctions in keratinocytes: analysis with the N-cadherin dominant negative mutant.

E-cadherin is a Ca(2+)-dependent cell-cell adhesion molecule at adherens junctions (AJs) of epithelial cells. A fragment of N-cadherin lacking its extracellular region serves as a dominant negative mutant (DN) and inhibits cell-cell adhesion activity of E-cadherin, but its mode of action remains to be elucidated. Nectin is a Ca(2+)-independent immunoglobulin-like cell-cell adhesion molecule at AJs and is associated with E-cadherin through their respective peripheral membrane proteins, afadin and catenins, which connect nectin and cadherin to the actin cytoskeleton, respectively. We showed here that overexpression of nectin capable of binding afadin, but not a mutant incapable of binding afadin, reduced the inhibitory effect of N-cadherin DN on the cell-cell adhesion activity of E-cadherin in keratinocytes. Overexpressed nectin recruited N-cadherin DN to the nectin-based cell-cell adhesion sites in an afadin-dependent manner. Moreover, overexpression of nectin enhanced the E-cadherin-based cell-cell adhesion activity. These results suggest that N-cadherin DN competitively inhibits the association of the endogenous nectin-afadin system with the endogenous E-cadherin-catenin system and thereby reduces the cell-cell adhesion activity of E-cadherin. Thus, nectin plays a role in the formation of E-cadherin-based AJs in keratinocytes.