title: G protein-coupled receptor kinase 2 activates radixin, regulating membrane protrusion and motility in epithelial cells.
abstract: Ezrin/radixin/moesin (ERM) proteins are membrane-cytoskeleton linkers that also have roles in signal transduction. Here we show that G protein-coupled receptor kinase 2 (GRK2) regulates membrane protrusion and cell migration during wound closure in Madin-Darby canine kidney (MDCK) epithelial cell monolayers at least partly through activating phosphorylation of radixin on a conserved, regulatory C-terminal Thr residue. GRK2 phosphorylated radixin exclusively on Thr 564 in vitro. Expression of a phosphomimetic (Thr-564-to-Asp) mutant of radixin resulted in increased Rac1 activity, membrane protrusion and cell motility in MDCK cells, suggesting that radixin functions "upstream" of Rac1, presumably as a scaffolding protein. Phosphorylation of ERM proteins was highest during the most active phase of epithelial cell sheet migration over the course of wound closure. In view of these results, we explored the mode of action of quinocarmycin/quinocarcin analog DX-52-1, an inhibitor of cell migration and radixin function with considerable selectivity for radixin over the other ERM proteins, finding that its mechanism of inhibition of radixin does not appear to involve binding and antagonism at the site of regulatory phosphorylation.
authors.affiliation: Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA.
authors.forename: Alem W
authors.initials: AW
authors.lastname: Kahsai
authors.forename: Shoutian
authors.initials: S
authors.lastname: Zhu
authors.forename: Gabriel
authors.initials: G
authors.lastname: Fenteany
mesh_terms: D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D022081:Cell Surface Extensions / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D007546:Isoquinolines / Q000494:pharmacology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D007546:Isoquinolines; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; C071776:radixin; C091971:DX 52-1; D054769:G-Protein-Coupled Receptor Kinase 2; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein