title: Serine-910 phosphorylation of focal adhesion kinase is critical for sarcomere reorganization in cardiomyocyte hypertrophy.
abstract: OBJECTIVE
  Tyrosine-phosphorylated focal adhesion kinase (FAK) is required for the hypertrophic response of cardiomyocytes to growth factors and mechanical load, but the role of FAK serine phosphorylation in this process is unknown. The aims of the present study were to characterize FAK serine phosphorylation in cultured neonatal rat ventricular myocytes (NRVM), analyse its functional significance during hypertrophic signalling, and examine its potential role in the pathogenesis of human dilated cardiomyopathy (DCM).
  
  
  RESULTS
  Endothelin-1 (ET-1) and other hypertrophic factors induced a time- and dose-dependent increase in FAK-S910 phosphorylation. ET-1-induced FAK-S910 phosphorylation required ET(A)R-dependent activation of PKCδ and Src via parallel Raf-1 → MEK1/2 → ERK1/2 and MEK5 → ERK5 signalling pathways. Replication-deficient adenoviruses expressing wild-type (WT) FAK and a non-phosphorylatable, S910A-FAK mutant were then used to examine the functional significance of FAK-S910 phosphorylation. Unlike WT-FAK, S910A-FAK increased the half-life of GFP-tagged paxillin within costameres (as determined by total internal reflection fluorescence microscopy and fluorescence recovery after photobleaching) and increased the steady-state FAK-paxillin interaction (as determined by co-immunoprecipitation and western blotting). These alterations resulted in reduced NRVM sarcomere reorganization and cell spreading. Finally, we found that FAK was serine-phosphorylated at multiple sites in non-failing, human left ventricular tissue. FAK-S910 phosphorylation and ERK5 expression were dramatically reduced in patients undergoing heart transplantation for end-stage DCM.
  
  
  CONCLUSIONS
  FAK undergoes S910 phosphorylation via PKCδ and Src-dependent pathways that are important for cell spreading and sarcomere reorganization. Reduced FAK-S910 phosphorylation may contribute to sarcomere disorganization in DCM.
authors.affiliation: Department of Physiology,  Loyola University Medical Center, Maywood, IL,  USA.
authors.forename: Miensheng
authors.initials: M
authors.lastname: Chu
authors.forename: Rekha
authors.initials: R
authors.lastname: Iyengar
authors.forename: Yevgeniya E
authors.initials: YE
authors.lastname: Koshman
authors.forename: Taehoon
authors.initials: T
authors.lastname: Kim
authors.forename: Brenda
authors.initials: B
authors.lastname: Russell
authors.forename: Jody L
authors.initials: JL
authors.lastname: Martin
authors.forename: Alain L
authors.initials: AL
authors.lastname: Heroux
authors.forename: Seth L
authors.initials: SL
authors.lastname: Robia
authors.forename: Allen M
authors.initials: AM
authors.lastname: Samarel
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D002311:Cardiomyopathy, Dilated / Q000201:enzymology* / Q000473:pathology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D004789:Enzyme Activation; D036681:Fluorescence Recovery After Photobleaching; D051417:Focal Adhesion Kinase 1 / Q000235:genetics / Q000378:metabolism*; D006333:Heart Failure / Q000201:enzymology* / Q000473:pathology; D006801:Humans; D047468:Immunoprecipitation; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009154:Mutation; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D051419:Paxillin / Q000235:genetics / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012518:Sarcomeres / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D012694:Serine; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D051419:Paxillin; D011993:Recombinant Fusion Proteins; D000804:Angiotensin II; D010656:Phenylephrine; D012694:Serine; D007334:Insulin-Like Growth Factor I; C497260:Prkcd protein, rat; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C496052:Ptk2 protein, rat; D019061:src-Family Kinases; D051745:Protein Kinase C-delta