Protein kinase C-mediated phosphorylation of troponin I and C-protein in isolated myocardial cells is associated with inhibition of myofibrillar actomyosin MgATPase

Richard C Venema, J. F. Kuo

Research output: Contribution to journalArticle

154 Citations (Scopus)

Abstract

Phosphorylation of cardiac myofibrillar proteins by protein kinase C (PKC) in isolated adult rat cardiomyocytes has been compared with that mediated by the cAMP-dependent protein kinase (PKA). PKA activation by β-adrenoreceptor (isoproterenol) stimulation results in stoichiometric phosphorylation of troponin I (TnI) and C-protein. PKC activation by either 12-O- tetradecanoylphorbol-13-acetate (TPA) or by α-adrenoreceptor (phenylephrine plus propranolol) stimulation results in phosphorylation of the same two proteins to similar extents. Two-dimensional phosphopeptide mapping shows that the same sites in TnI are modified by PKC in vitro and in TPA- or α- agonist-stimulated cells. These sites are distinct from those phosphorylated in isoproterenol-stimulated cells or by PKA in vitro. Phosphopeptide mapping analysis of C-protein shows that PKC and PKA phosphorylate identical residues in this protein in vitro and in situ. TPA-stimulated phosphorylation in myocytes is associated with a reduction in maximal activity of myofibrillar Ca2+-dependent actomyosin MgATPase. Isoproterenol-stimulated phosphorylation has no effect on maximal activity but reduces the Ca2+ sensitivity of the MgATPase. These data demonstrate that TnI and C-protein are phosphorylated in myocardial cells by both PKA and PKC, resulting in different functional consequences in each case.

Original languageEnglish (US)
Pages (from-to)2705-2711
Number of pages7
JournalJournal of Biological Chemistry
Volume268
Issue number4
StatePublished - Jan 1 1993

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Troponin C
Actomyosin
Phosphorylation
Troponin I
Protein Kinase C
Protein Kinases
Tetradecanoylphorbol Acetate
Isoproterenol
Phosphopeptides
Acetates
Proteins
Chemical activation
Phenylephrine
Cyclic AMP-Dependent Protein Kinases
Protein C
Cardiac Myocytes
Propranolol
Muscle Cells
Rats
In Vitro Techniques

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Protein kinase C-mediated phosphorylation of troponin I and C-protein in isolated myocardial cells is associated with inhibition of myofibrillar actomyosin MgATPase. / Venema, Richard C; Kuo, J. F.

In: Journal of Biological Chemistry, Vol. 268, No. 4, 01.01.1993, p. 2705-2711.

Research output: Contribution to journalArticle

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