Evidence for a tyrosine kinase-dependent activation of the adenylyl Cyclase/PKA cascade downstream from the G-protein-linked endothelin ETA receptor in vascular smooth muscle.
Endothelin (ET-1), a contractor and mitogen in the vasculature, enhanced cAMP production (t1/2, 2.2 min; EC50, 89 +/- 6.3 nM) and stimulated activity of the cAMP-dependent protein kinase (PKA) in pig coronary arteries. These responses were blunted by the protein tyrosine kinase (PTK) inhibitors genistein and herbimycin-A, but not by inhibitors of protein kinase C or cyclooxygenase. In contrast, forskolin-stimulated cAMP production was unaffected by PTK inhibition. Immunoblot analysis revealed that ET-1 induced a concentration-dependent protein tyrosine (PT) phosphorylation. Sarafotoxin-c, a selective ETB receptor agonist, had no effect on either cAMP levels or PT phosphorylation. Moreover, pervanadate (PV), a potent inhibitor of PT phosphatases, enhanced both cAMP formation and PT phosphorylation, both of which were blocked by PTK inhibitors. The effects of ET-1 and PV were not additive, suggesting a similar mode of activation, whereas responses to ET-1 and forskolin were synergistic. These findings indicate that AC and PKA are activatable via a nonreceptor PTK-dependent pathway downstream from the G-protein-linked ETA receptor. Because cAMP is a dilator and antimitogen in smooth muscle, stimulation of AC activity may be a negative feedback mechanism regulating ET-1-induced vasoconstriction and/or mitogenesis.
El-Mowafy
A M
AM
Department of Physiology and Biophysics, Wright State University School of Medicine, Dayton, Ohio, 45435, USA.
White
R E
RE
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D016227:Benzoquinones; D005576:Colforsin / Q000494:pharmacology; D003331:Coronary Vessels / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019833:Genistein / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D047029:Lactams, Macrocyclic; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000187:drug effects / Q000502:physiology*; D017828:Rifabutin / Q000031:analogs & derivatives; D015398:Signal Transduction; D013552:Swine; D014638:Vanadates / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D016227:Benzoquinones; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D010455:Peptides; D011809:Quinones; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D014757:Viper Venoms; C076715:pervanadate; C089502:sarafotoxin-c; D005576:Colforsin; D017828:Rifabutin; D014638:Vanadates; C020754:herbimycin; D019833:Genistein; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases