title: Bi-directional regulation of dephosphorylation of cAMP-dependent phosphorylated proteins by cAMP and calcium in permeabilized rat heart cells.
abstract: We studied the regulation of dephosphorylation of cAMP-dependent phosphorylated proteins of isolated, permeabilized (skinned) myocardial cells from adult rat. Staurosporine, a potent inhibitor of protein kinase, inhibited cAMP-dependent phosphorylation of phospholamban and troponin-I, the key proteins in the control of contraction and relaxation of the myocardial cells. Staurosporine antagonized the stimulatory action of cAMP on the spontaneous beating of the myocytes accompanied by dephosphorylation of phospholamban but not of troponin-I at pCa 7-8. In cold ATP dilution experiments with apparent stoppage of protein phosphorylation, dephosphorylation of phospholamban was accelerated both by Ca2+ and staurosporine but that of troponin-I took place only in the presence of Ca2+ ion (pCa less than 6.5). These phenomena suggest a bi-directional regulation of dephosphorylation of the key proteins by the intracellular messengers cAMP and Ca2+.
authors.affiliation: Department of Biology, Faculty of Science, Osaka University.
authors.forename: A
authors.initials: A
authors.lastname: Yoshida
authors.forename: H
authors.initials: H
authors.lastname: Takisawa
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D051381:Rats; D019311:Staurosporine; D014336:Troponin / Q000378:metabolism*; D019210:Troponin I; D000099211:Phospholamban
chemical_list: D000255:Adenosine Triphosphate; D000470:Alkaloids; D002118:Calcium; D002135:Calcium-Binding Proteins; D000242:Cyclic AMP; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D019311:Staurosporine; D014336:Troponin; D019210:Troponin I; D000099211:Phospholamban