Immunosuppressants implicate protein phosphatase regulation of K+ channels in guard cells

Proc Natl Acad Sci U S A. 1993 Mar 15;90(6):2202-6. doi: 10.1073/pnas.90.6.2202.

Abstract

The elevation of Ca2+ levels in the cytoplasm inactivates inward-rectifying K+ channels that play a central role in regulating the apertures of stomatal pores in higher plants. However, the mechanism for the Ca(2+)-mediated inhibition of K(+)-channel function is unknown. Using patch-clamp techniques, we show that cyclophilin-cyclosporin A and FK506-binding protein-FK506 complexes, which are highly specific inhibitors of protein phosphatase 2B (calcineurin), block Ca(2+)-induced inactivation of K+ channels in Vicia faba guard cells. A constitutively active calcineurin fragment that is Ca(2+)-independent inhibits K(+)-channel activity in the absence of Ca2+. We have also identified an endogenous Ca(2+)-dependent phosphatase activity from V. faba that is inhibited by the cyclophilin-cyclosporin A and FK506-binding protein-FK506 complexes. Our findings implicate a Ca(2+)-dependent, calcineurin-like protein phosphatase in a Ca2+ signal-transduction pathway of higher plants.

Publication types

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

MeSH terms

  • Amino Acid Isomerases / metabolism
  • Amino Acid Isomerases / pharmacology*
  • Amino Acid Sequence
  • Calcium / pharmacology
  • Carrier Proteins / metabolism
  • Carrier Proteins / pharmacology*
  • Cyclosporine / metabolism
  • Cyclosporine / pharmacology*
  • Kinetics
  • Membrane Potentials / drug effects
  • Molecular Sequence Data
  • Peptides / metabolism
  • Peptidylprolyl Isomerase
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Phosphoprotein Phosphatases / metabolism*
  • Plant Cells
  • Plant Physiological Phenomena*
  • Plants / drug effects
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Protein Kinases / metabolism
  • Substrate Specificity
  • Tacrolimus / metabolism
  • Tacrolimus / pharmacology*
  • Tacrolimus Binding Proteins

Substances

  • Carrier Proteins
  • Peptides
  • Potassium Channels
  • Cyclosporine
  • Protein Kinases
  • Phosphoprotein Phosphatases
  • Amino Acid Isomerases
  • Tacrolimus Binding Proteins
  • Peptidylprolyl Isomerase
  • Calcium
  • Tacrolimus