Different behavior of 1-Afadin and Neurabin-II during the formation and destruction of cell-cell adberens junction

Abstract

We have recently isolated two novel actin filament-binding proteins, 1-afadin and neurabin-II and shown that they are localized at cell-cell adherens junction (AJ) in epithelial cells. We found here that 1-afadin, neurabin-II, ZO-1, and E-cadherin showed similar and different behavior during the formation and destruction of cell-cell AJ in MDCK cells. In MDCK cells, the accumulation of both 1-afadin and E-cadherin, but not that of ZO-1, changed in parallel depending on Rac small G protein activity. Dissociation of MDCK cells by culturing the cells at 2 μM Ca2+ caused rapid endocytosis of E-cadherin, but not that of 1-afadin or ZO-1. Addition of phorbol 12-myristate 13-acetate to these dissociated cells formed a tight junction-like structure where ZO-1 and 1-afadin, but not neurabin-II or E-cadherin, accumulated. We furthemore found that, in nonepithelial EL cells, which expressed E-cadherin and attached to each other, 1-afadin, neurabin-II, ZO-1 and E-cadherin were all localized at AJ. In cadherin-deficient L cells, 1-afadin was mainly localized at cell-cell contact sites, but ZO-1 was mainly localized at the tip area of cell processes. Neurabin-II did not accumulate at the plasma membrane area. Neither 1-afadin nor neurabin-II significantly interacted with α-, β-catenin, E-cadherin, ZO-1 or occludin.