title: Tumor necrosis factor receptor-associated factor-6 and ribosomal S6 kinase intracellular pathways link the angiotensin II AT1 receptor to the phosphorylation and activation of the IkappaB kinase complex in vascular smooth muscle cells.
abstract: Activation of NF-κB transcription factors by locally produced angiotensin II (Ang II) is proposed to be involved in chronic inflammatory reactions leading to atherosclerosis development. However, a clear understanding of the signaling cascades coupling the Ang II AT1 receptors to the activation of NF-κB transcription factors is still lacking. Using primary cultured aortic vascular smooth muscle cells, we show that activation of the IKK complex and NF-κB transcription factors by Ang II is regulated by phosphorylation of the catalytic subunit IKKβ on serine residues 177 and 181 in the activation T-loop. The use of pharmacological inhibitors against conventional protein kinases C (PKCs), mitogen-activated/extracellular signal-regulated kinase (MEK) 1/2, ribosomal S6 kinase (RSK), and silencing RNA technology targeting PKCα, IKKβ subunit, tumor growth factor β-activating kinase-1 (TAK1), the E3 ubiquitin ligase tumor necrosis factor receptor-associated factor-6 (TRAF6), and RSK isoforms, demonstrates the requirement of two distinct signaling pathway for the phosphorylation of IKKβ and the activation of the IKK complex by Ang II. Rapid phosphorylation of IKKβ requires a second messenger-dependent pathway composed of PKCα-TRAF6-TAK1, whereas sustained phosphorylation and activation of IKKβ requires the MEK1/2-ERK1/2-RSK pathway. Importantly, simultaneously targeting components of these two pathways completely blunts the phosphorylation of IKKβ and the proinflammatory effect of the octapeptide. This is the first report demonstrating activation of TAK1 by the AT1R. We propose a model whereby TRAF6-TAK1 and ERK-RSK intracellular pathways independently and sequentially converge to the T-loop phosphorylation for full activation of IKKβ, which is an essential step in the proinflammatory activity of Ang II.
authors.affiliation: Faculty of Pharmacy and Groupe de Recherche Universitaire sur le Médicament, Université de Montréal, Montreal H3C 3J7, Canada.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Doyon
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Servant
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism*; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048370:MAP Kinase Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D008954:Models, Biological; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism*; D015290:Second Messenger Systems; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D051550:I-kappa B Kinase; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020930:MAP Kinase Kinase Kinases; D048052:Mitogen-Activated Protein Kinase 3; D051571:Protein Kinase C-alpha; D047428:Protein Kinase Inhibitors; D044140:Receptor, Angiotensin, Type 1; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D048029:TNF Receptor-Associated Factor 6; D000099151:MAP Kinase Kinase Kinase 7; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3