Stimulation of the mitogen-activated protein kinase via the A2A-adenosine receptor in primary human endothelial cells.
Adenosine exerts a mitogenic effect on human endothelial cells via stimulation of the A2A-adenosine receptor. This effect can also be elicited by the beta2-adrenergic receptor but is not mimicked by elevation of intracellular cAMP levels. In the present work, we report that stimulation of the A2A-adenosine receptor and of the beta2-adrenergic receptor activates mitogen-activated protein kinase (MAP kinase) in human endothelial cells based on the following criteria: adenosine analogues and beta-adrenergic agonists cause an (i) increase in tyrosine phosphorylation of the p42 isoform and to a lesser extent of the p44 isoform of MAP kinase and (ii) stimulate the phosphorylation of myelin basic protein by MAP kinase; (iii) this is accompanied by a redistribution of the enzyme to the perinuclear region. Pretreatment of the cells with cholera toxin (to down-regulate Gsalpha) abolishes activation of MAP kinase by isoproterenol but not that induced by adenosine analogues. In addition, MAP kinase stimulation via the A2A-adenosine receptor is neither impaired following pretreatment of the cells with pertussis toxin (to block Gi-dependent pathways) nor affected by GF109203X (1 microM; to inhibit typical protein kinase C isoforms) nor by a monoclonal antibody, which blocks epidermal growth factor-dependent signaling. In contrast, MAP kinase activation is blocked by PD 098059, an inhibitor of MAP kinase kinase 1 (MEK1) activation, which also blunts the A2A-adenosine receptor-mediated increase in [3H]thymidine incorporation. Activation of the A2A-adenosine receptor is associated with increased levels of GTP-bound p21(ras). Thus, our experiments define stimulation of MAP kinase as the candidate cellular target mediating the mitogenic action of the A2A-adenosine receptor on primary human endothelial cells; the signaling pathway operates via p21(ras) and MEK1 but is independent of Gi, Gs, and the typical protein kinase C isoforms. This implies an additional G protein which links this prototypical Gs-coupled receptor to the MAP kinase cascade.
Sexl
V
V
Institute of Pharmacology, University of Vienna, Währinger Strasse 13a, A-1090 Vienna, Austria.
Mancusi
G
G
Höller
C
C
Gloria-Maercker
E
E
Schütz
W
W
Freissmuth
M
M
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide); D000911:Antibodies, Monoclonal; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000201:enzymology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000276:immunology; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D010766:Phosphorylation; D018047:Receptors, Purinergic P1 / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D014665:Vasodilator Agents / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D004791:Enzyme Inhibitors; D005419:Flavonoids; D018047:Receptors, Purinergic P1; D014665:Vasodilator Agents; D016222:Fibroblast Growth Factor 2; D015124:8-Bromo Cyclic Adenosine Monophosphate; D019830:Adenosine-5'-(N-ethylcarboxamide); D014443:Tyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D000241:Adenosine; D007545:Isoproterenol; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D013936:Thymidine