Regulation of E-cadherin endocytosis by nectin through afadin, Rap1, and p120ctn

Adherens junctions (AJs) are a major cell-cell adhesion structure in epithelial cells that are formed by two major cell-cell adhesion molecules, E-cadherin and nectin. We have previously shown that nectin first forms cell-cell adhesion and then recruits non-trans-interacting E-cadherin to the nectin-based cell-cell adhesion sites, which gradually trans-interact there, eventually forming AJs. We have examined here the effect of trans-interacting nectin on non-trans-interacting E-cadherin endocytosis. Trans-interacting nectin capable of associating with afadin, but not trans-interacting nectin mutant incapable of associating with afadin, inhibited non-trans-interacting E-cadherin endocytosis in intact cells. Afadin is a nectin- and actin filament-binding protein that connects nectin to the actin cytoskeleton. Studies on the mode of action of the nectin- afadin system using cell-free assay revealed that afadin associated with nectin bound Rap1 activated by trans-interacting nectin, interacted with p120(ctn), and strengthened the binding of p120ctn to E-cadherin, eventually reducing non-trans-interacting E-cadherin endocytosis. Afadin, which did not bind Rap1, was inactive in this capacity. These results indicate that trans-interacting nectin inhibits non-trans-interacting E-cadherin endocytosis through afadin, Rap1, and p120ctn and thereby further accumulates non-trans-interacting E-cadherin to the nectin-based cell-cell adhesion sites for the formation of AJs.