An essential role for ARF6-regulated membrane traffic in adherens junctionturnover and epithelial cell migration

We describe a novel role for the ARF6 GTPase in the regulation of adherens junction (AJ) turnover in MDCK epithelial cells. Expression of a GTPase-def ective ARF6 mutant, ARF6(Q67L), led to a loss of AJs and ruffling of the la teral plasma membrane via mechanisms that were mutually exclusive. ARF6-GTP -induced AJ disassembly did not require actin remodeling, but was dependent on the internalization of E-cadherin into the cytoplasm via vesicle transp ort. ARF6 activation was accompanied by increased migratory potential, and treatment of cells with hepatocyte growth factor (HGF) induced the activati on of endogenous ARF6. The effect of ARF6(Q67L) on AJs was specific since A RF6 activation did not perturb tight junction assembly or cell polarity. In contrast, dominant-negative ARF6, ARF6(T27N), localized to AJs and its exp ression blocked cell migration and HGF-induced internalization of cadherin- based junctional components into the cytoplasm. Finally, we show that ARF6 exerts its role downstream (if v-Src activation during the disassembly of A Js. These findings document an essential role for ARF6-regulated membrane t raffic in AJ disassembly and epithelial cell migration.