Role of protein kinase C in the phosphorylation of cardiac myosin light chain 2

Richard C Venema, R. L. Raynor, T. A. Noland, J. F. Kuo

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Abstract

The role of protein kinase C (PKC) in the phosphorylation of myosin light chain 2 (MLC2) in adult rat heart cells has been investigated. PKC-mediated phosphorylation of MLC2 in adult rat cardiac myofibrils in vitro occurs with a stoichiometry (0.7 mol of phosphate/mol of protein) similar to that mediated by myosin light chain kinase (MLCK). Two-dimensional tryptic phosphopeptide mapping of MLC2 following phosphorylation by PKC or MLCK in vitro yields the same major phosphopeptides for each protein kinase. These sites are also 32P-labelled in situ when isolated cardiomyocytes are incubated with [32P]P(i). 32P labelling of MLC2 in cardiomyocytes is increased by 5-fold in 10 min upon incubation with the phosphatase inhibitor calyculin A, demonstrating the existence of a rapidly turning over component of MLC2 phosphorylation in these cells. 32P label is completely removed from MLC2 when myocytes are exposed to 2,3-butanedione monoxime, an inhibitor of cardiac contraction known to desensitize the myofilaments to activation by Ca2+. 32P labelling of MLC2 is also decreased by 50-100% following exposure to the PKC-selective inhibitors calphostin C and chelerythrine, suggesting that PKC, and not MLCK, is primarily responsible for incorporation of rapidly turning over phosphate into MLC2 in situ. Taken together, these data implicate PKC in the phosphorylation of MLC2 in heart cells and support the hypothesis that phosphorylation of cardiac MLC2 has a role in determining myofibrillar Ca2+ sensitivity.

Original languageEnglish (US)
Pages (from-to)401-406
Number of pages6
JournalBiochemical Journal
Volume294
Issue number2
DOIs
StatePublished - Jan 1 1993

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Cardiac Myosins
Phosphorylation
Protein Kinase C
Myosin-Light-Chain Kinase
Phosphopeptides
Myofibrils
Cardiac Myocytes
Labeling
Rats
Phosphates
myosin light chain 2
Phosphoric Monoester Hydrolases
Stoichiometry
Protein Kinases
Muscle Cells
Labels
Chemical activation

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

Role of protein kinase C in the phosphorylation of cardiac myosin light chain 2. / Venema, Richard C; Raynor, R. L.; Noland, T. A.; Kuo, J. F.

In: Biochemical Journal, Vol. 294, No. 2, 01.01.1993, p. 401-406.

Research output: Contribution to journalArticle

Venema, Richard C ; Raynor, R. L. ; Noland, T. A. ; Kuo, J. F. / Role of protein kinase C in the phosphorylation of cardiac myosin light chain 2. In: Biochemical Journal. 1993 ; Vol. 294, No. 2. pp. 401-406.
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