Protein kinase-independent inhibition of muscarinic K+ channels by staurosporine

Am J Physiol. 1994 Apr;266(4 Pt 1):C1128-32. doi: 10.1152/ajpcell.1994.266.4.C1128.

Abstract

Acetylcholine (ACh) binding to atrial muscarinic receptors activates an inwardly rectifying K+ current (IK[ACh]) via a pertussis toxin-sensitive GTP-binding protein (GK). The muscarinic K+ channel (termed GIRK1) has been cloned, and the nucleotide sequence contains nine consensus sites for protein kinase C (PKC) phosphorylation (16). Dephosphorylation of the muscarinic K+ channel has been implicated in rapid IK[ACh] desensitization in the presence of agonist (13). Staurosporine is a widely used membrane-permeant inhibitor of PKC and other protein kinases (7), including G protein-coupled receptor kinases. We investigated the role of phosphorylation in the regulation of IK[ACh] by examining the effect of a variety of protein kinase inhibitors. Staurosporine produced a rapid and reversible dose-dependent decrease in IK[ACh], activated by either GTP or guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S). Other PKC inhibitors, including calphostin C and K-252b, were without effect on GTP gamma S-activated IK[ACh]. In excised patches of atrial membrane under nonphosphorylating conditions (0 ATP, 1 mM 5'-adenylylimidodiphosphate), staurosporine reversibly reduced muscarinic K+ channel activity without altering single-channel current amplitude. These results suggest that staurosporine inhibits IK[ACh] by a mechanism independent of intracellular protein kinases.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Imidodiphosphate / pharmacology
  • Alkaloids / pharmacology*
  • Animals
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
  • Heart Atria
  • Myocardium / cytology
  • Myocardium / metabolism*
  • Potassium Channel Blockers*
  • Protein Kinase Inhibitors
  • Protein Kinases / physiology*
  • Rana catesbeiana
  • Receptors, Muscarinic / metabolism*
  • Staurosporine

Substances

  • Alkaloids
  • Potassium Channel Blockers
  • Protein Kinase Inhibitors
  • Receptors, Muscarinic
  • Adenylyl Imidodiphosphate
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Protein Kinases
  • Staurosporine