Receptor-mediated inhibition of adenylate cyclase and stimulation of arachidonic acid release in 3T3 fibroblasts. Selective susceptibility to islet-activating protein, pertussis toxin.
Thrombin exhibited diverse effects on mouse 3T3 fibroblasts. It (a) decreased cAMP in the cell suspension, (b) inhibited adenylate cyclase in the Lubrol-permeabilized cell suspension in a GTP-dependent manner, increased releases of (c) arachidonic acid and (d) inositol from the cell monolayer prelabeled with these labeled compounds, (e) increased 45Ca2+ uptake into the cell monolayer, and (f) increased 86Rb+ uptake into the cell monolayer in a ouabain-sensitive manner. Most of the effects were reproduced by bradykinin, platelet-activating factor, and angiotensin II. The receptors for these agonists are thus likely to be linked to three separate effector systems: the adenylate cyclase inhibition, the phosphoinositide breakdown leading to Ca2+ mobilization and phospholipase A2 activation, and the Na,K-ATPase activation. Among the effects of these agonists, (a), (b), (c), and (e) were abolished, but (d) and (f) were not, by prior treatment of the cells with islet-activating protein (IAP), pertussis toxin, which ADP-ribosylates the Mr = 41,000 protein, the alpha-subunit of the inhibitory guanine nucleotide regulatory protein (Ni), thereby abolishing receptor-mediated inhibition of adenylate cyclase. The effects (a), (c), (d), and (e) of thrombin, but not (b), were mimicked by A23187, a calcium ionophore. The effects of A23187, in contrast to those of receptor agonists, were not affected by the treatment of cells with IAP. Thus, the IAP substrate, the alpha-subunit of Ni, or the protein alike, may play an additional role in signal transduction arising from the Ca2+-mobilizing receptors, probably mediating process(es) distal to phosphoinositide breakdown and proximal to Ca2+ gating.
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D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001427:Bacterial Toxins / Q000494:pharmacology*; D001886:Bordetella pertussis; D002122:Calcium Chloride / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D037342:Pertussis Toxin; D012413:Rubidium / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D014316:Tritium; D010566:Virulence Factors, Bordetella
D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D001095:Arachidonic Acids; D001427:Bacterial Toxins; D002712:Chlorides; D010566:Virulence Factors, Bordetella; D014316:Tritium; D016718:Arachidonic Acid; D007294:Inositol; D000242:Cyclic AMP; D037342:Pertussis Toxin; D013917:Thrombin; D019204:GTP-Binding Proteins; D002122:Calcium Chloride; D012413:Rubidium; C032710:rubidium chloride