Phospholamban and troponin I are substrates for protein kinase C in vitro but not in intact beating guinea pig hearts

I. Édes, E. G. Kranias

Research output: Contribution to journalArticle

60 Citations (Scopus)

Abstract

The incorporation of [32P]inorganic phosphate into membranous, myofibrillar, and cytosolic proteins was studied in Langendorff-perfused guinea pig hearts treated with phorbol 12-myristate 13-acetate (PMA) or 1,2-dioctanoylglycerol (D8G), which are potent activators of protein kinase C. Control hearts were perfused with an inactive phorbol ester (4α-phorbol 12,13-didecanoate), which does not cause activation of protein kinase C. To ensure the blockade of different receptor systems, the perfusions were carried out in the presence of prazosin, propranolol, and atropine. Perfusion of hearts with either PMA (4 μM) or D8G (200 μM) was associated with a negative effect on left ventricular inotropy and relaxation. Examination of the 32P incorporation into various fractions revealed that there were no increases in the degree of phosphorylation of phospholamban in sarcoplasmic reticulum, and troponin I and C protein in the myofibrils, although these proteins were found to be substrates for protein kinase C in vitro. However, in the same hearts, there were significant changes in the 32P incorporation into a 28-kDa cytosolic protein. Examination of the activity levels of protein kinase C in hearts perfused with PMA indicated a redistribution of this activity from the cytosolic to the membrane fraction, suggesting the activation of the enzyme in vivo. These findings indicate that regulatory phosphoproteins, which may be phosphorylated by protein kinase C in vitro, are not substrates for protein kinase C in beating hearts perfused with phorbol esters or diacylglycerol analogues.

Original languageEnglish
Pages (from-to)394-400
Number of pages7
JournalCirculation Research
Volume67
Issue number2
Publication statusPublished - 1990

Fingerprint

Troponin I
Protein Kinase C
Guinea Pigs
Acetates
Phorbol Esters
Proteins
Perfusion
Troponin C
Enzyme Activation
Myofibrils
Prazosin
Phosphoproteins
Diglycerides
Sarcoplasmic Reticulum
Atropine
Propranolol
phospholamban
In Vitro Techniques
Phosphates
Phosphorylation

Keywords

  • Diacylglycerol
  • Heart
  • Phorbol ester
  • Protein phosphorylation

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

Cite this

Phospholamban and troponin I are substrates for protein kinase C in vitro but not in intact beating guinea pig hearts. / Édes, I.; Kranias, E. G.

In: Circulation Research, Vol. 67, No. 2, 1990, p. 394-400.

Research output: Contribution to journalArticle

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