Role of Rab13 binding protein JRAB/MICAL-L2 in regulating cell polarity and adhesion

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Dynamic rearrangement of epithelial cell junctions, tight junction (TJ) and adherens junction (AJ), is essential to maintain the homeostasis of the organism in response to various stimuli. The transport of integral TJ and AJ proteins, claudins, occludins and cadherins, to and/or from the plasma membrane enables this rearrangement. We previously revealed that Rab13 and JRAB/MICAL-L2 (JRAB) mediated the endocytic recycling of occludin. In the present study, we identified Rab8 and actinin-4 as JRAB-binding proteins by using yeast two-hybrid screening. Rab13 and Rab8 competed with each other for the binding to JRAB and functionally associated with JRAB at the plasma membrane and recycling endosome, respectively. Furthermore, Rab13-bound JRAB was targeted to the plasma membrane through its binding to actinin-4. These results suggest that JRAB regulates epithelial cell polarity and adhesion through its binding to Rab13, Rab8 and actinin-4.