alpha-Adrenergic response and myofilament activity in mouse hearts lacking PKC phosphorylation sites on cardiac TnI.
Protein kinase C (PKC)-mediated phosphorylation of cardiac myofilament (MF) proteins has been shown to depress the actomyosin interaction and may be important during heart failure. Biochemical studies indicate that phosphorylation of Ser(43) and Ser(45) of cardiac troponin I (cTnI) plays a substantial role in the PKC-mediated depression. We studied intact and detergent-extracted papillary muscles from nontransgenic (NTG) and transgenic (TG) mouse hearts that express a mutant cTnI (Ser43Ala, Ser45Ala) that lacks specific PKC-dependent phosphorylation sites. Treatment of NTG papillary muscles with phenylephrine (PE) resulted in a transient increase and a subsequent 62% reduction in peak twitch force. TG muscles showed no transient increase and only a 45% reduction in force. There was a similar difference in maximum tension between NTG and TG fiber bundles that had been treated with a phorbol ester and had received subsequent detergent extraction. Although levels of cTnI phosphorylation correlated with these differences, the TG fibers also demonstrated a decrease in phosphorylation of cardiac troponin T. The PKC-specific inhibitor chelerythrine inhibited these responses. Our data provide evidence that specific PKC-mediated phosphorylation of Ser(43) and Ser(45) of cTnI plays an important role in regulating force development in the intact myocardium.
Montgomery
David E
DE
Program in Cardiovascular Sciences, Department of Physiology and Biophysics, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
Wolska
Beata M
BM
Pyle
W Glen
WG
Roman
Brian B
BB
Dowell
Jasmine C
JC
Buttrick
Peter M
PM
Koretsky
Alan P
AP
Del Nido
Pedro
P
Solaro
R John
RJ
D008841:Actin Cytoskeleton / Q000378:metabolism; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D001665:Binding Sites; D003902:Detergents; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D006321:Heart / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology; D010617:Phenanthridines / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019210:Troponin I / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D000470:Alkaloids; D053119:Benzophenanthridines; D003902:Detergents; D004791:Enzyme Inhibitors; D010617:Phenanthridines; D011942:Receptors, Adrenergic, alpha; D019210:Troponin I; D010768:Phosphoserine; D010656:Phenylephrine; C016299:chelerythrine; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate