title: PKA-mediated protein phosphorylation regulates ezrin-WWOX interaction.
abstract: The 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 Ser(66) and established its functional role in parietal cell activation [R. Zhou et al., Characterization of protein kinase A-mediated phosphorylation of ezrin in gastric parietal cell activation, J. Biol. Chem. 278 (2003) 35651-35659], but the underlying basis for this regulation is not known. Here, we provide the first evidence that PKA-mediated phosphorylation of Ser(66)regulates the interaction of ezrin with WWOX, a WW domain-containing protein. Our biochemical study reveals that ezrin directly binds to the first WW domain of WWOX via its C-terminal tyrosine-containing polyproline sequence (470)PPPPPPVY(477). Mutational analyses further demonstrate that tyrosine(477) is essential for the ezrin-WWOX interaction. In addition, our study shows that PKA-mediated phosphorylation of ezrin is essential and sufficient for the apical localization of WWOX protein as disruption of ezrin-WWOX interaction eliminated the apical localization of WWOX. Finally, our study demonstrates the essential role of ezrin-WWOX interaction in the apical membrane remodeling associated with H,K-ATPase recruitment. Taken together, these results define a novel molecular mechanism underlying phospho-regulation of ezrin function by PKA in parietal cell activation.
authors.affiliation: Laboratory of Cellular Dynamics, University of Science and Technology of China, Heifei National Laboratory for Physical Sciences at the Microscale, Hefei 230027, China.
authors.forename: Changjiang
authors.initials: C
authors.lastname: Jin
authors.forename: Ling
authors.initials: L
authors.lastname: Ge
authors.forename: Xia
authors.initials: X
authors.lastname: Ding
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Hongling
authors.initials: H
authors.lastname: Zhu
authors.forename: Tarsha
authors.initials: T
authors.lastname: Ward
authors.forename: Fang
authors.initials: F
authors.lastname: Wu
authors.forename: Xinwang
authors.initials: X
authors.lastname: Cao
authors.forename: Qichen
authors.initials: Q
authors.lastname: Wang
authors.forename: Xuebiao
authors.initials: X
authors.lastname: Yao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011817:Rabbits; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D000074584:WW Domain-Containing Oxidoreductase; D000099149:Ezrin
chemical_list: D017868:Cyclic AMP-Dependent Protein Kinases; D003598:Cytoskeletal Proteins; D010088:Oxidoreductases; D025521:Tumor Suppressor Proteins; D014443:Tyrosine; D000074584:WW Domain-Containing Oxidoreductase; D000099149:Ezrin; C486071:WWOX protein, human