title: Evidence for protein phosphatase 1 and 2A regulation of K+ channels in two types of leaf cells.
abstract: Ion channels control ion fluxes across membranes, membrane potential, and signal transduction between and within cells. Protein kinases and phosphatases are important regulators involved in stimulus-response coupling in eukaryotic organisms. We have identified in extracts of Vicia faba leaf cells protein phosphatase activities inhibited by okadaic acid (OA) and calyculin A (CA), two inhibitors of protein phosphatases 1 and 2A. Using whole-cell patch-clamp techniques, we have demonstrated that inward K+ currents in guard cells are inhibited by nanomolar concentrations of OA or CA, whereas outward K+ currents are not affected. However, the same inhibitors enhance the magnitude of outward K+ currents in mesophyll cells. A phosphatase antagonist, adenosine-5'-O-(3-thiotriphosphate), has an effect similar to OA and CA on outward K+ currents in mesophyll cells. Our findings suggest that protein phosphatases 1 and/or 2A play different physiological roles in modulating the activity of K+ channels in mesophyll cells and guard cells.
authors: Biological Laboratory, Harvard University, Cambridge, Massachusetts 02138.
authors: W
authors: W
authors: Li
authors: S
authors: S
authors: Luan
authors: S L
authors: SL
authors: Schreiber
authors: S M
authors: SM
authors: Assmann
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004988:Ethers, Cyclic / Q000494:pharmacology; D007887:Fabaceae; D006706:Homeostasis; D007700:Kinetics; D008387:Marine Toxins; D008564:Membrane Potentials / Q000187:drug effects; D019319:Okadaic Acid; D010080:Oxazoles / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology*; D010946:Plants, Medicinal; D015221:Potassium Channels / Q000502:physiology*; D054645:Protein Phosphatase 1
chemical_list: D004988:Ethers, Cyclic; D008387:Marine Toxins; D010080:Oxazoles; D015221:Potassium Channels; D019319:Okadaic Acid; C022571:adenosine 5'-O-(3-thiotriphosphate); D004533:Egtazic Acid; C059041:calyculin A; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1