title: Ras controls tumor necrosis factor receptor-associated factor (TRAF)6-dependent induction of nuclear factor-kappa b. Selective regulation through receptor signaling components.
abstract: In the present study, we show that Ras activity differentially controls interleukin (IL)-1 induced transcription factor activation by selective regulation of responses mediated by receptor complex components. Initial experiments revealed that stimulation with IL-1 caused a rapid, matrix-dependent activation of Ras. The effect was transient, peaking at 5 min and returning to base levels after 30 min. Activation correlated with pronounced changes in cell shape in EGFPH-Ras transfected cells. Transfection with the dominant negative mutant, Ras(Asn-17), inhibited IL-1 induced activation of the IL-8 promoter as well as of NF-kappa B and AP-1 synthetic promoters in transient transfection assays. Furthermore, overexpression of the IL-1 signaling proteins TRAF6 or MyD88 gave characteristic activation of IL-8, which was accentuated in the presence of IL-1. Co-transfection with Ras(Asn-17) gave a dose-dependent inhibition of TRAF6-induced responses in the presence and absence of IL-1, but had no effect on MyD88 mediated activity. Similarly, induction of NF-kappa B was abolished by Ras(Asn-17) only in TRAF6-transfected cells. In contrast, inhibiting Ras activity limited AP-1-mediated responses through both receptor complex proteins. Constitutively active Ras(Val-12) increased the TRAF6 induced activity of the NF-kappa B pathway similar to the effect induced by IL-1, while the Ras(Val-12) induced activity was not inhibited by co-transfection with a dominant negative TRAF6. Our data show that activation of the Ras GTPase is an early, matrix-dependent response in IL-1 signaling which participates in structural regulation of IL-1-induced genes. In addition, they show that the Ras induced effect selectively regulates TRAF6-mediated activation of the NF-kappa B pathway, suggesting that Ras GTPase represents a convergence point in structural and cytokine responses, with distinct effects on a subset of downstream signaling events.
authors.affiliation: Functional Genomics, Division of Molecular and Genetic Medicine, University of Sheffield, S10 2JF, United Kingdom.
authors.forename: C J
authors.initials: CJ
authors.lastname: Caunt
authors.forename: E
authors.initials: E
authors.lastname: Kiss-Toth
authors.forename: F
authors.initials: F
authors.lastname: Carlotti
authors.forename: R
authors.initials: R
authors.lastname: Chapman
authors.forename: E E
authors.initials: EE
authors.lastname: Qwarnstrom
mesh_terms: D002448:Cell Adhesion; D002478:Cells, Cultured; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D016209:Interleukin-8 / Q000235:genetics; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000502:physiology*; D048029:TNF Receptor-Associated Factor 6; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D007375:Interleukin-1; D016209:Interleukin-8; D016328:NF-kappa B; D011506:Proteins; D048029:TNF Receptor-Associated Factor 6; D020559:Monomeric GTP-Binding Proteins