Different actions of protein kinase C isoforms alpha and epsilon on gastric acid secretion

Br J Pharmacol. 2002 Jul;136(6):938-46. doi: 10.1038/sj.bjp.0704790.

Abstract

1. The phorbol ester TPA, an activator of protein kinase C (PKC), inhibits cholinergic stimulation of gastric acid secretion but increases basal H(+) secretion. 2. Since these contradictory findings suggest the action of different PKC isozymes we analysed the role of calcium-dependent PKC-alpha, and calcium-independent PKC-epsilon in gastric acid secretion. 3. Inhibition of PKC-alpha by the indolocarbazole Gö 6976 revealed that about 28% of carbachol-induced acid secretion was inhibited by PKC-alpha. In the presence of Gö 6976 approximately 64% of the carbachol-induced signal transduction is mediated by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), and 14% is conveyed by PKC-epsilon as deduced from the inhibition with the bisindolylmaleimide Ro 31-8220. 4. Inhibition of carbachol-induced acid secretion by TPA was accompanied by a decrease in CaMKII activity. 5. The stimulation of basal acid secretion by TPA was biphasic with a peak at a very low concentration (10 pM), resulting in an activation of the calcium-sensor CaMKII. The activation was determined with a phosphospecific polyclonal antibody against active CaMKII. The TPA-induced increase of H(+) secretion was sensitive to the cell-permeable Ca(2+)-chelator BAPTA/AM, Ro 31-8220, and the CaMKII-inhibitor KN-62, but not to Gö 6976. 6. Since TPA induced the translocation of PKC-epsilon but not of PKC-alpha in resting parietal cells, PKC-epsilon seems to be at least responsible for an initial elevation of free intracellular calcium to initiate TPA-induced acid secretion. 7. Our data indicate the different roles of two PKC isoforms: PKC-epsilon activation appears to facilitate cholinergic stimulation of H(+)-secretion likely by increasing intracellular calcium. In contrast, PKC-alpha activation attenuates acid secretion accompanied by a down-regulation of CaMKII activity.

MeSH terms

  • Animals
  • Blotting, Western
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors
  • Carbachol / antagonists & inhibitors
  • Carbachol / pharmacology
  • Carbazoles / pharmacology
  • Cells, Cultured
  • Enzyme Activators / pharmacology
  • Gastric Acid / metabolism*
  • In Vitro Techniques
  • Indoles / pharmacology
  • Male
  • Parietal Cells, Gastric / drug effects
  • Parietal Cells, Gastric / enzymology
  • Parietal Cells, Gastric / metabolism
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Protein Kinase C-alpha
  • Protein Kinase C-epsilon
  • Rabbits
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Carbazoles
  • Enzyme Activators
  • Indoles
  • Go 6976
  • Carbachol
  • Protein Kinase C
  • Protein Kinase C-alpha
  • Protein Kinase C-epsilon
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Tetradecanoylphorbol Acetate
  • Ro 31-8220