title: Parallel contractile signal transduction pathways activated by receptors for thrombin and epidermal growth factor-urogastrone in guinea pig gastric smooth muscle: blockade by inhibitors of mitogen-activated protein kinase-kinase and phosphatidyl inositol 3'-kinase.
abstract: Using a guinea pig gastric longitudinal smooth muscle preparation, we have compared the contractile signaling pathways triggered by the thrombin receptor-activating peptide, TFLLR-NH2 (TF) and by epidermal growth factor-urogastrone (EGF). In addition to inhibitors of tyrosine kinase [tyrphostin 47/AG213, genistein and the src-selective inhibitor CP118,556/PP1], cyclooxygenase (indomethacin, INDO) and diacylglycerol lipase (U57, 908), we also used the signal pathway probe inhibitors of mitogen-activated protein-kinase-kinase (MEK:PD98059), phosphatidylinositol 3'-kinase [PI3K: Wortmannin (WM) and LY294002], protein kinase C [PKC: GF109203X (GF)], and of the EGF-receptor kinase (PD153035). We found that in addition to the inhibition of both TF and EGF-stimulated contractions by the inhibitors of tyrosine kinase, cyclooxygenase and diacylglycerol lipase, the actions of TF and EGF were also attenuated by PD98059, WM/LY294002 and GF. However, PD153035 blocked only EGF-triggered contractions. The contractile actions of both TF and EGF were dependent on extracellular calcium. In contrast, the contractile action of arachidonic acid, via a presumed cyclooxygenase product that mediated the contractions caused by both TF and EGF, was not blocked by any of the signal pathway probe inhibitors. The contractile actions of both TF and EGF were accompanied by increases in tissue phosphotyrosyl proteins and an increase in tissue c-src kinase activity. We conclude that protease-activated receptor no. 1- (thrombin receptor) mediated contractions in the logitudial muscle, like EGF receptor-activated responses, require the influx of extracellular calcium and use parallel signal pathways upstream of the cyclooxygenase step, involving MEK, PI3K, kinase C and possibly cellular src. The TF-induced response did not involve trans-activation of the EGF receptor kinase; but the converse (i.e., trans-activation of protease-activated receptor no. 1 (thrombin receptor) by the EGF receptor kinase) could not be ruled out.
authors.affiliation: Endocrine Research Group, Department of Pharmacology & Therapeutics, The University of Calgary Faculty of Medicine, Calgary, Alberta, Canada T2N 4N1.
authors.forename: X L
authors.initials: XL
authors.lastname: Zheng
authors.forename: B
authors.initials: B
authors.lastname: Renaux
authors.forename: M D
authors.initials: MD
authors.lastname: Hollenberg
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004815:Epidermal Growth Factor / Q000187:drug effects* / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors; D006168:Guinea Pigs; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011799:Quinazolines / Q000494:pharmacology; D018179:Receptors, Thrombin / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D018179:Receptors, Thrombin; D016718:Arachidonic Acid; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases; D008071:Lipoprotein Lipase; D002118:Calcium; C088860:4-((3-bromophenyl)amino)-6,7-dimethoxyquinazoline