title: Protein kinase C disrupts cannabinoid actions by phosphorylation of the CB1 cannabinoid receptor.
abstract: We have found that phosphorylation of a G-protein-coupled receptor by protein kinase C (PKC) disrupts modulation of ion channels by the receptor. In AtT-20 cells transfected with rat cannabinoid receptor (CB1), the activation of an inwardly rectifying potassium current (Kir current) and depression of P/Q-type calcium channels by cannabinoids were prevented by stimulation of protein kinase C by 100 nM phorbol 12-myristate 13-acetate (PMA). In contrast, activation of Kir current by somatostatin was unaffected, and inhibition of calcium channels was only modestly attenuated. The possibility that PKC acted by phosphorylating CB1 receptors was confirmed by demonstrating that PKC phosphorylated a single serine (S317) of a fusion protein incorporating the third intracellular loop of CB1. Mutating this serine to alanine did not affect the ability of CB1 to modulate currents, but it eliminated disruption by PMA, demonstrating that PKC can disrupt ion channel modulation by receptor phosphorylation.
authors.affiliation: Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Garcia
authors.forename: S
authors.initials: S
authors.lastname: Brown
authors.forename: B
authors.initials: B
authors.lastname: Hille
authors.forename: K
authors.initials: K
authors.lastname: Mackie
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D048588:Benzoxazines; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002186:Cannabinoids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002273:Carcinogens / Q000494:pharmacology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D006727:Hormone Antagonists / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D016296:Mutagenesis; D009281:Naphthalenes / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010704:Phorbols / Q000494:pharmacology; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012694:Serine; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013004:Somatostatin / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D020866:omega-Conotoxin GVIA
chemical_list: D000700:Analgesics; D048588:Benzoxazines; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002186:Cannabinoids; D002273:Carcinogens; D006727:Hormone Antagonists; D007211:Indoles; D008301:Maleimides; D009025:Morpholines; D009281:Naphthalenes; D010455:Peptides; D010704:Phorbols; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D011993:Recombinant Fusion Proteins; D012694:Serine; D013004:Somatostatin; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D020866:omega-Conotoxin GVIA; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D019311:Staurosporine; C088060:bisindolylmaleimide; D013755:Tetradecanoylphorbol Acetate; C033085:phorbol