The epsilon subtype of protein kinase C is required for cardiomyocyte connexin-43 phosphorylation

Circ Res. 2000 Feb 18;86(3):293-301. doi: 10.1161/01.res.86.3.293.


Gap junctions (GJs), composed of connexins, are intercellular channels ensuring electric and metabolic coupling between cardiomyocytes. We have shown previously that an endogenous mitogenic and cardioprotective protein, fibroblast growth factor-2 (FGF-2), decreases cardiomyocyte GJ permeability by stimulating phosphorylation of connexin-43 (Cx43). Identifying the kinase(s) phosphorylating cardiac Cx43 may thus provide a way of modulating cardiac intercellular communication. Because FGF-2 activates receptors linked to protein kinase C (PKC) and mitogen-activated protein kinase, we first investigated participation of these enzymatic systems in Cx43 phosphorylation. The inhibitor PD98059 blocked activation of mitogen-activated protein kinase, but it did not prevent the FGF-2 effects on GJs. In contrast, the PKC inhibitor chelerythrine blocked the effects of FGF-2 on Cx43 phosphorylation and permeability. Because the epsilon-isoform of PKC localizes to plasma membrane sites, we examined whether it is directly involved in the FGF-2-induced Cx43 phosphorylation. In nonstimulated myocytes, PKCepsilon displayed a discontinuous pattern of localization at intercellular contact sites and partial colocalization with Cx43. Treatment with FGF-2 or phorbol 12-myristate 13-acetate induced a more continuous pattern of PKCepsilon distribution, whereas the anti-Cx43 staining appeared to overlap extensively with that of PKCepsilon. In immunoprecipitation experiments using specific anti-Cx43 antibodies, PKCepsilon but not PKCalpha coprecipitated with Cx43. FGF-2 increased levels of coprecipitated PKCepsilon, suggesting increased association between PKCepsilon and Cx43 on stimulation. Transient gene transfer and overexpression of cDNAs coding for truncated or mutated dominant-negative forms of PKCepsilon decreased cardiomyocyte Cx43 phosphorylation significantly. We conclude that PKC mediates the FGF-2-induced effects on cardiac GJs and that PKCepsilon likely interacts with and phosphorylates cardiac Cx43 at sites of intercellular contact.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaloids
  • Animals
  • Benzophenanthridines
  • Cells, Cultured
  • Connexin 43 / metabolism*
  • Enzyme Inhibitors / pharmacology
  • Fibroblast Growth Factor 2 / pharmacology
  • Gap Junctions / drug effects
  • Humans
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / physiology*
  • Mitogen-Activated Protein Kinases / physiology
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Phenanthridines / pharmacology
  • Phosphorylation / drug effects
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / physiology*
  • Protein Kinase C-epsilon
  • Rats
  • Recombinant Proteins / pharmacology
  • Tetradecanoylphorbol Acetate / pharmacology
  • Tissue Distribution


  • Alkaloids
  • Benzophenanthridines
  • Connexin 43
  • Enzyme Inhibitors
  • Isoenzymes
  • Phenanthridines
  • Recombinant Proteins
  • Fibroblast Growth Factor 2
  • chelerythrine
  • Prkce protein, rat
  • PRKCE protein, human
  • Protein Kinase C
  • Protein Kinase C-epsilon
  • Mitogen-Activated Protein Kinases
  • Tetradecanoylphorbol Acetate