title: Suppression of phospholipase C blocks Gi-mediated inhibition of adenylyl cyclase activity.
abstract: The potential effect of inhibition of phospholipase C on the response of Gi-coupled receptors was investigated in neuroblastoma x glioma hybrid (NG108-15) cells. The phospholipase C specific inhibitor 1-[6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H -pyrrole-2,5-dione (U73122), which did not affect basal and forskolin-stimulated adenylyl cyclase activities, time- and dose-dependently blocked delta-opioid receptor-mediated inhibition of adenylyl cyclase activity, the EC50 (0.5 microM) of which was consistent with that for inhibition of bradykinin-dependent phospholipase C activation (EC50 = 1 microM). U73122 treatment also blocked functional responses of m4 muscarinic receptor and alpha2-adrenoceptor in NG108-15 cells and three opioid receptors (mu, delta and opioid receptor-like receptor (ORL1)) in human neuroblastoma SK-N-SH cells. 1-[6-((17Beta-3-Methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-2, 5-pyrrolidinedione (U73343), an inactive analog of U73122, did not show any effect, which suggests that the blockade by U73122 of Gi-coupled receptor-mediated signaling is probably mediated through inhibition of phospholipase C, although a possible direct modification of G proteins can not be excluded. Furthermore, treatment with U73122 but not U73343 blocked the GTP-induced inhibition of adenylyl cyclase, indicating blockade at the level of Gi proteins.
authors.affiliation: Shanghai Institute of Cell Biology, Chinese Academy of Sciences, PR China.
authors.forename: G H
authors.initials: GH
authors.lastname: Fan
authors.forename: T H
authors.initials: TH
authors.lastname: Zhou
authors.forename: W B
authors.initials: WB
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Pei
mesh_terms: D000262:Adenylyl Cyclases / Q000096:biosynthesis / Q000187:drug effects* / Q000378:metabolism; D000700:Analgesics / Q000494:pharmacology; D001920:Bradykinin / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D004794:Enzyme Repression; D004963:Estrenes / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D006825:Hybridomas / Q000187:drug effects / Q000201:enzymology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011760:Pyrrolidinones / Q000494:pharmacology*; D017465:Receptors, Opioid, delta / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects; D010738:Type C Phospholipases / Q000096:biosynthesis / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000700:Analgesics; D004745:Enkephalins; D004963:Estrenes; D010726:Phosphodiesterase Inhibitors; D011760:Pyrrolidinones; D017465:Receptors, Opioid, delta; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D020881:Enkephalin, D-Penicillamine (2,5)-; D000242:Cyclic AMP; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D001920:Bradykinin