title: Activation of the endothelin receptor inhibits the G protein-coupled inwardly rectifying potassium channel by a phospholipase A2-mediated mechanism.
abstract: To develop a malleable system to model the well-described, physiological interactions between Gq/11 - coupled receptor and Gi/o-coupled receptor signaling, we coexpressed the endothelin A receptor, the mu-opioid receptor, and the G protein-coupled inwardly rectifying potassium channel (Kir 3) heteromultimers in Xenopus laevis oocytes. Activation of the Gi/o-coupled mu-opioid receptor strongly increased Kir 3 channel current, whereas activation of the Gq/11-coupled endothelin A receptor inhibited the Kir 3 response evoked by mu-opioid receptor activation. The magnitude of the inhibition of Kir 3 was channel subtype specific; heteromultimers composed of Kir 3.1 and Kir 3.2 or Kir 3.1 and Kir 3.4 were significantly more sensitive to the effects of endothelin-1 than heteromultimers composed of Kir 3.1 and Kir 3.5. The difference in sensitivity of the heteromultimers suggests that the endothelin-induced inhibition of the opioid- activated current was caused by an effect at the channel rather than at the opioid receptor. The endothelin-1-mediated inhibition was mimicked by arachidonic acid and blocked by the phospholipase A2 inhibitor arachidonoyl trifluoromethyl ketone. Consistent with a possible phospholipase A2-mediated mechanism, the endothelin-1 effect was blocked by calcium chelation with BAPTA-AM and was not affected by kinase inhibition by either staurosporine or genistein. The data suggest the hypothesis that Gq/11-coupled receptor activation may interfere with Gi/o-coupled receptor signaling by the activation of phospholipase A2 and subsequent inhibition of effector function by a direct effect of an eicosanoid on the channel.
authors: Department of Pharmacology, University of Washington, Seattle 98195-7280, USA.
authors: S L
authors: SL
authors: Rogalski
authors: C
authors: C
authors: Cyr
authors: C
authors: C
authors: Chavkin
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000378:metabolism; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D019332:Endothelin-1 / Q000494:pharmacology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004745:Enkephalins / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000737:chemistry / Q000201:enzymology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D020239:Receptor Cross-Talk / Q000502:physiology; D017466:Receptors, Endothelin / Q000235:genetics / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors; D019311:Staurosporine / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D000701:Analgesics, Opioid; D000838:Anions; D002614:Chelating Agents; D019332:Endothelin-1; D004745:Enkephalins; D004791:Enzyme Inhibitors; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D017466:Receptors, Endothelin; D011976:Receptors, Muscarinic; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D016718:Arachidonic Acid; D004533:Egtazic Acid; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; D019311:Staurosporine; D002118:Calcium