Ezrin-WWOX相互作用生化研究

he ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton, and also participate in signal-transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the cAMP-dependent protein kinase activation cascade to the regulated HCl secretion in gastric parietal cells. Our recent studies have mapped the PKA-mediated phosphorylation site to Ser66 and established its functional role in parietal cell activation (Zhou et al., 2003, J. Biol. Chem. 278, 35651-35659). Here, we report the identification of a novel ezrin effector, WWOX, a putative tumor suppressor containing two WW domains. Our biochemical study reveals that PKA-mediated phosphorylation of ezrin at Ser66 regulates ezrin-WWOX interaction in vitro, and ezrin directly binds to the first WW domain of WWOX via its C-terminal tyrosine-containing polyproline sequence PPVY. Our mutational analyses further demonstrate that tyrosine477 is essential for the ezrin-WWOX interaction. Given the fact that tyrosine477 is a major substrate for tyrosine kinase (Heiska and Carpen. 2005, J. Biol. Chem. 280, 10244-10252), these results indicate that phosphorylation of ezrin by Src and PKA modulates its association with WWOX.