Cyclic AMP stimulates K+ channel activity in mesophyll cells of Vicia faba L.
Whole-cell patch-clamp recordings from Vicia faba mesophyll protoplasts reveal that outward K+ current is increased in a dose-dependent fashion by intracellular application of cAMP. The enhancement of the outward current by cAMP is specific and it cannot be mimicked by a series of nucleotides that includes AMP, cGMP, and GMP. The enhancement is evoked by micromolar concentrations of cAMP in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine. PKI or Walsh inhibitor, a specific peptide inhibitor of cAMP-dependent protein kinase (PKA), inhibits the outward K+ current. Adenosine 3',5'-phosphothioate, a competitive inhibitor of PKA, has a similar effect. Conversely, the catalytic subunit of PKA (cAMP independent) from bovine brain enhances the magnitude of the outward K+ current in the absence of added cAMP. Our results indicate that cAMP modulates K+ channel activity in mesophyll cells and suggest that this modulation occurs through a cAMP-regulated protein kinase.
Li
W
W
Biological Laboratory, Harvard University, Cambridge, Massachusetts 02138.
Luan
S
S
Schreiber
S L
SL
Assmann
S M
SM
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology; D003994:Bucladesine / Q000494:pharmacology; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000494:pharmacology; D006152:Cyclic GMP / Q000494:pharmacology; D004558:Electric Stimulation; D007887:Fabaceae / Q000502:physiology*; D006157:Guanosine Monophosphate / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects; D009946:Organothiophosphorus Compounds / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010946:Plants, Medicinal; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*
D036341:Intercellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D009946:Organothiophosphorus Compounds; D010455:Peptides; D015221:Potassium Channels; C085074:Walsh peptide; C091478:adenosine 3',5'-phosphothioate; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D006157:Guanosine Monophosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D006152:Cyclic GMP; D000241:Adenosine; D015056:1-Methyl-3-isobutylxanthine