We addressed the role of EFA6, exchange factor for ARF6, during the development of epithelial cell polarity in MDCK cells. EFA6 is located primarily at the apical pole of polarized cells, including the plasma membrane (PM). Following calcium-triggered E-cadherin-mediated cell adhesion, EFA6 is recruited to a Triton X-100 insoluble fraction and its protein level is increased concomitantly to the accelerated formation of a functional TJ. The expression of EFA6 results in the selective retention at the cell surface of the TJ protein occludin. This effect is due to EFA6 capacities to promote selectively the stability of the apical actin ring onto which the TJ is anchored, resulting in the exclusion of TJ proteins from endocytosis. Finally, our data suggest that EFA6 effects are achieved by the coordinate action of both its exchange activity and its actin remodeling C-terminal domain. We conclude that EFA6 is a signaling molecule that responds to E-cadherin engagement and is involved in TJ formation and stability.
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