title: Role of Ras in metal-induced EGF receptor signaling and NF-kappaB activation in human airway epithelial cells.
abstract: We showed previously that epithelial growth factor (EGF) receptor (EGFR) signaling is triggered by metallic compounds associated with ambient air particles. Specifically, we demonstrated that As, Zn, and V activated the EGFR tyrosine kinase and the downstream kinases MEK1/2 and ERK1/2. In this study, we examined the role of Ras in EGFR signaling and the nuclear factor-kappaB (NF-kappaB) activation pathway and the possible interaction between these two signaling pathways in a human airway epithelial cell line (BEAS-2B) exposed to As, V, or Zn ions. Each metal significantly increased Ras activity, and this effect was inhibited by the EGFR tyrosine kinase activity inhibitor PD-153035. Adenoviral-mediated overexpression of a dominant-negative mutant form of Ras(N17) significantly blocked MEK1/2 or ERK1/2 phosphorylation in As-, Zn-, or V-exposed BEAS-2B cells but caused little inhibition of V-, Zn- or EGF-induced EGFR tyrosine phosphorylation. This confirmed Ras as an important intermediate effector in EGFR signaling. Interestingly, V, but not As, Zn, or EGF, induced IkappaBalpha serine phosphorylation, IkappaBalpha breakdown, and NF-kappaB DNA binding. Moreover, PD-153035 and overexpression of Ras(N17) each significantly blocked V-induced IkappaBalpha breakdown and NF-kappaB activation, while inhibition of MEK activity with PD-98059 failed to do so. In summary, exposure to As, Zn, and V initiated EGFR signaling and Ras-dependent activation of MEK1/2 and ERK1/2, but only V induced Ras-dependent NF-kappaB nuclear translocation. EGFR signaling appears to cross talk with NF-kappaB signaling at the level of Ras, but additional signals appear necessary for NF-kappaB activation. Together, these data suggest that, in V-treated BEAS-2B cells, Ras-dependent signaling is essential, but not sufficient, for activation of NF-kappaB.
authors.affiliation: Center for Environmental Medicine and Lung Biology, University of North Carolina, Chapel Hill 27599, USA.
authors.forename: Weidong
authors.initials: W
authors.lastname: Wu
authors.forename: Ilona
authors.initials: I
authors.lastname: Jaspers
authors.forename: Wenli
authors.initials: W
authors.lastname: Zhang
authors.forename: Lee M
authors.initials: LM
authors.lastname: Graves
authors.forename: James M
authors.initials: JM
authors.lastname: Samet
mesh_terms: D001151:Arsenic / Q000494:pharmacology; D001980:Bronchi / Q000166:cytology; D002461:Cell Line, Transformed; D004268:DNA-Binding Proteins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D008670:Metals / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D014639:Vanadium / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D020672:I-kappa B Proteins; D008670:Metals; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011799:Quinazolines; D014639:Vanadium; D000072000:NF-KappaB Inhibitor alpha; C482128:MAP2K2 protein, human; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D015032:Zinc; D001151:Arsenic; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; C088860:4-((3-bromophenyl)amino)-6,7-dimethoxyquinazoline