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
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Isomerases / metabolism
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Amino Acid Isomerases / pharmacology*
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Amino Acid Sequence
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Calcium / pharmacology
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Carrier Proteins / metabolism
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Carrier Proteins / pharmacology*
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Cyclosporine / metabolism
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Cyclosporine / pharmacology*
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Kinetics
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Membrane Potentials / drug effects
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Molecular Sequence Data
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Peptides / metabolism
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Peptidylprolyl Isomerase
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Phosphoprotein Phosphatases / antagonists & inhibitors
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Phosphoprotein Phosphatases / metabolism*
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Plant Cells
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Plant Physiological Phenomena*
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Plants / drug effects
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Potassium Channels / drug effects
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Potassium Channels / physiology*
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Protein Kinases / metabolism
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Substrate Specificity
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Tacrolimus / metabolism
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Tacrolimus / pharmacology*
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Tacrolimus Binding Proteins
Substances
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Carrier Proteins
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Peptides
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Potassium Channels
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Cyclosporine
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Protein Kinases
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Phosphoprotein Phosphatases
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Amino Acid Isomerases
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Tacrolimus Binding Proteins
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Peptidylprolyl Isomerase
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Calcium
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Tacrolimus