title: beta 2-adrenergic receptor activates extracellular signal-regulated kinases (ERKs) via the small G protein rap1 and the serine/threonine kinase B-Raf.
abstract: G protein-coupled receptors can induce cellular proliferation by stimulating the mitogen-activated protein (MAP) kinase cascade. Heterotrimeric G proteins are composed of both alpha and betagamma subunits that can signal independently to diverse intracellular signaling pathways including those that activate MAP kinases. In this study, we examined the ability of isoproterenol, an agonist of the beta(2)-adrenergic receptor (beta(2)AR), to stimulate extracellular signal-regulated kinases (ERKs). Using HEK293 cells, which express endogenous beta(2)AR, we show that isoproterenol stimulates ERKs via beta(2)AR. This action of isoproterenol requires cAMP-dependent protein kinase and is insensitive to pertussis toxin, suggesting that Galpha(s) activation of cAMP-dependent protein kinase is required. Interestingly, beta(2)AR activates both the small G proteins Rap1 and Ras, but only Rap1 is capable of coupling to Raf isoforms. beta(2)AR inhibits the Ras-dependent activation of both Raf isoforms Raf-1 and B-Raf, whereas Rap1 activation by isoproterenol recruits and activates B-Raf. beta(2)AR activation of ERKs is not blocked by expression of RasN17, an interfering mutant of Ras, but is blocked by expression of either RapN17 or Rap1GAP1, both of which interfere with Rap1 signaling. We propose that isoproterenol can activate ERKs via Rap1 and B-Raf in these cells.
authors.affiliation: Vollum Institute and the Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland 97201, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Schmitt
authors.forename: P J
authors.initials: PJ
authors.lastname: Stork
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D002846:Chromatography, Affinity; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009532:Nickel / Q000378:metabolism; D037342:Pertussis Toxin; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D020033:Protein Isoforms; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D018631:ras Proteins / Q000378:metabolism
chemical_list: D000318:Adrenergic beta-Agonists; D020033:Protein Isoforms; D018343:Receptors, Adrenergic, beta-2; D011993:Recombinant Fusion Proteins; D010566:Virulence Factors, Bordetella; D009532:Nickel; D037342:Pertussis Toxin; D005982:Glutathione Transferase; D019908:Proto-Oncogene Proteins c-raf; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins; D007545:Isoproterenol