title: IKK beta is required for Bcl-2-mediated NF-kappa B activation in ventricular myocytes.
abstract: The transcription factor nuclear factor kappa B (NF-kappa B) is regulated by cytoplasmic inhibitor I kappa B alpha. An integral step in the activation of NF-kappa B involves the phosphorylation and degradation of I kappa B alpha. We have previously reported that I kappa B alpha activity is diminished in ventricular myocytes expressing Bcl-2 (de Moissac, D., Zheng, H., and Kirshenbaum, L. A. (1999) J. Biol. Chem. 274, 29505-29509). The underlying mechanism by which Bcl-2 activates NF-kappa B is undefined. In view of growing evidence that the I kappa B kinases (IKKs), notably IKK beta, are involved in signal induced phosphorylation of I kappa B alpha, we ascertained whether IKK beta is necessary and sufficient for Bcl-2 mediated NF-kappa B activation. Here we demonstrate that expression of Bcl-2 in ventricular myocytes resulted in an increase in NF-kappa B-dependent DNA binding, NF-kappa B gene transcription and reduced I kappa B alpha levels. An increase in the IKK beta kinase activity was observed in cells expressing full-length Bcl-2 but not in cells expressing the BH4 deletion mutant of Bcl-2 (Delta BH4; residues 10-30). Catalytically inactive mutants of IKK beta, but not IKK alpha, suppressed Bcl-2-mediated I kappa B alpha phosphorylation and NF-kappa B activation. Transfection of human embryonic 293 cells with a kinase-defective Raf-1 or a kinase-defective mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-1 (MEKK-1) suppressed Bcl-2-mediated IKK beta activity and NF-kappa B activation. Further, Bcl-2-mediated NF-kappa B activity was impaired in nullizygous mouse embryonic fibroblasts deficient for IKK beta. In this report, we provide the first direct evidence that Bcl-2 activates NF-kappa B by a signaling mechanism that involves Raf-1/MEKK-1 mediated activation of IKK beta.
authors.affiliation: Institute of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, and the Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba R2H 2A6, Canada.
authors.forename: Kelly M
authors.initials: KM
authors.lastname: Regula
authors.forename: Karen
authors.initials: K
authors.lastname: Ens
authors.forename: Lorrie A
authors.initials: LA
authors.lastname: Kirshenbaum
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D048728:MAP Kinase Kinase Kinase 1; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D032383:Myocytes, Cardiac / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D016895:Culture Media, Serum-Free; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; C000606206:Nfkbia protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D048728:MAP Kinase Kinase Kinase 1; C482576:MAP3K1 protein, human; C482578:Map3k1 protein, mouse