Protein Kinase C Contributes to the Maintenance of Contractile Force in Human Ventricular Cardiomyocytes

• Published in: The Journal of biological chemistry Vol. 284; no. 2; pp. 1031 - 1039
• Main Authors: Molnár, Andrea, Borbély, Attila, Czuriga, Dániel, Ivetta, Siket M., Szilágyi, Szabolcs, Hertelendi, Zita, Pásztor, Enikó T., Balogh, Ágnes, Galajda, Zoltán, Szerafin, Tamás, Jaquet, Kornelia, Papp, Zoltán, Édes, István, Tóth, Attila
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.01.2009; American Society for Biochemistry and Molecular Biology
• Subjects: Adult; Calcium - pharmacology; Cytosol - drug effects; Cytosol - enzymology; Enzyme Activation - drug effects; Female; Heart Ventricles - drug effects; Heart Ventricles - enzymology; Humans; Isoenzymes - metabolism; Male; Muscle Contraction; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - enzymology; Protein Binding; Protein Kinase C - metabolism; Substrate Specificity; Troponin I - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M807600200

Prolonged Ca2+ stimulations often result in a decrease in contractile force of isolated, demembranated human ventricular cardiomyocytes, whereas intact cells are likely to be protected from this deterioration. We hypothesized that cytosolic protein kinase C (PKC) contributes to this protection. Prolonged contracture (10 min) of demembranated human cardiomyocytes at half-maximal Ca2+ resulted in a 37 ± 5% reduction of active force (p < 0.01), whereas no decrease (2 ± 3% increase) was observed in the presence of the cytosol (reconstituted myocytes). The PKC inhibitors GF 109203X and Gö 6976 (10μmol/liter) partially antagonized the cytosol-mediated protection (15 ± 5 and 9 ± 2% decrease in active force, p < 0.05). Quantitation of PKC isoform expression revealed the dominance of the Ca2+-dependent PKCα over PKCδ and PKC∊ (189 ± 31, 7 ± 3, and 7 ± 2 ng/mg protein, respectively). Ca2+ stimulations of reconstituted human cardiomyocytes resulted in the translocation of endogenous PKCα, but not PKCβ1, δ, and ∊ from the cytosol to the contractile system (PKCα association: control, 5 ± 3 arbitrary units; +Ca2+, 39 ± 8 arbitrary units; p < 0.01, EC50,Ca = 645 nmol/liter). One of the PKCα-binding proteins were identified as the thin filament regulatory protein cardiac troponin I (TnI). Finally, the Ca2+-dependent interaction between PKCα and TnI was confirmed using purified recombinant proteins (binding without Ca2+ was only 28 ± 18% of that with Ca2+). Our data suggest that PKCα translocates to the contractile system and anchors to TnI in a Ca2+-dependent manner in the human heart, contributing to the maintenance of contractile force.