title: Load-induced focal adhesion kinase activation in the myocardium: role of stretch and contractile activity.
abstract: We investigated the influence of stretch and contractile activity on load-induced activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK)1/2 in isolated rat hearts. Increases of diastolic pressure from approximately 0 to approximately 15 mmHg rapidly increased FAK tyrosine phosphorylation (maximum: 2.3-fold) and binding to c-Src (maximum: 2.8-fold) and Grb2 (maximum: 3.6-fold). This was paralleled by activation (maximum: 2.8-fold) and binding of ERK1/2 to FAK. FAK and ERK1/2 were immunolocalized at sarcolemmal sites of cardiac myocytes and in the nuclei, in the case of ERK1/2. Balloon inflation to raise ventricular pressure in hearts perfused with cardioplegic solution also activated FAK and ERK1/2. However, increases in contractile activity induced by increasing calcium concentration in the perfusate (from 0.5 to 5 mM) did not activate the FAK multicomponent signaling complex or ERK1/2 in the myocardium. These results indicate that stretch rather than contractile activity induces FAK and ERK1/2 activation in the myocardium. In addition, the activation and binding of ERK1/2 to FAK suggest that FAK drives the load-induced activation of ERK1/2.
authors.affiliation: Department of Internal Medicine, School of Medicine, State University of Campinas, Campinas, São Paulo 13081-970, Brazil.
authors.forename: Priscila P
authors.initials: PP
authors.lastname: Domingos
authors.forename: Priscila M
authors.initials: PM
authors.lastname: Fonseca
authors.forename: Wilson
authors.initials: W
authors.lastname: Nadruz
authors.forename: Kleber G
authors.initials: KG
authors.lastname: Franchini
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D003971:Diastole / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020935:MAP Kinase Signaling System / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000201:enzymology; D009206:Myocardium / Q000166:cytology / Q000201:enzymology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical
chemical_list: D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases