title: Protein kinase C mediated activation and phosphorylation of Ca(2+)-pump in cardiac sarcolemma.
abstract: The effects of purified protein kinase C (PKC) on the Ca(2+)-pumping ATPase of cardiac sarcolemma were investigated. The addition of PKC to sarcolemmal vesicles resulted in a significant increase in ATP-dependent Ca2+ uptake, by increasing the calcium affinity by 2.8-fold (Km 0.14 vs. 0.4 microM for control) and by increasing Vmax from 5 to 6.8 nmol.mg protein-1.min-1. The addition of PKC also stimulated Ca2+ ATPase activity in sarcolemmal preparations. This activity was increased further upon the addition of calmodulin. These results suggest that PKC stimulates Ca2+ ATPase through a kinase-directed phosphorylation. The addition of PKC to a purified preparation of Ca2+ ATPase in the presence of [gamma-32P]ATP resulted in a 100% increase in phosphorylation that was dependent on the presence of Ca2+, phosphatidylserine, and phorbol 12,13-dibutyrate. These results demonstrate that the Ca2+ ATPase of canine cardiac muscle can be phosphorylated by PKC in vitro, resulting in increased affinity of the Ca2+ ATPase for Ca2+ and increase in the Ca2+ pump pumping rate. The results suggest that the Ca(2+)-pumping ATPase in heart tissue can be stimulated by PKC, thereby regulating the intracellular Ca2+ levels in whole heart.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, University of Toronto, Ont., Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Qu
authors.forename: J
authors.initials: J
authors.lastname: Torchia
authors.forename: A K
authors.initials: AK
authors.lastname: Sen
mesh_terms: D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics; D000252:Calcium-Transporting ATPases / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D004285:Dogs; D006321:Heart / Q000187:drug effects; D019811:Hydroxylamine; D006898:Hydroxylamines; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism / Q000494:pharmacology*; D012508:Sarcolemma / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D013268:Stimulation, Chemical
chemical_list: D006898:Hydroxylamines; D019811:Hydroxylamine; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases; D002118:Calcium