Fig. 5. A model for the role and mode of action of nectin in the formation of a junctional complex in epithelial cells. (A) Formation of AJs. When the two migrating cells contact through their protrusions, nectin and E-cadherin separately form trans-dimers that form microclusters at intercellular contact sites. The nectin-based microclusters are mainly formed at the initial stage. The nectin-based microclusters then recruit E-cadherin, which results in the formation of a mixture of nectin- and E-cadherin-based microclusters (primordial spot-like junctions). These primordial junctions fuse to form short line-like junctions, which develop into more matured AJs. Upper panel, transverse section view; lower panel, cross-section view. (B) Formation of TJs. During the formation of AJs, JAM is first assembled at the apical side, followed by the recruitment of claudin, which eventually leads to the establishment of TJs (cross-section view).