title: Involvement of double-stranded RNA-activated protein kinase in the synergistic activation of nuclear factor-kappaB by tumor necrosis factor-alpha and gamma-interferon in preneuronal cells.
abstract: Tumor necrosis factor-alpha (TNF-alpha) and gamma-interferon (IFN-gamma) cooperate during a variety of biological responses and ultimately synergistically enhance the expression of genes involved in immune and inflammatory responses. Recently, we demonstrated that IFN-gamma can significantly potentiate TNF-alpha-induced nuclear factor (NF)-kappaB nuclear translocation in neuronal derived and endothelial cell lines. The mechanism by which these two cytokines exert their synergistic effect on NF-kappaB involves the de novo degradation of the NF-kappaB inhibitor, IkappaBbeta. The double-stranded RNA-dependent kinase PKR is IFN-inducible and has been implicated in the activation of NF-kappaB; therefore, we examined the possibility that PKR may play a role in the synergistic activation of NF-kappaB during TNF-alpha/IFN-gamma cotreatment. The PKR inhibitor 2-aminopurine (2-AP) inhibited TNF-alpha/IFN-gamma-induced NF-kappaB nuclear translocation in neuronal derived cells but not in endothelial cells. The induced degradation of IkappaBbeta, which is normally observed upon TNF-alpha/IFN-gamma cotreatment, was blocked completely by 2-AP in neuronal derived cells. Also, 2-AP treatment or overexpression of a catalytically inactive PKR inhibited the TNF-alpha/IFN-gamma-induced synergistic activation of kappaB-dependent gene expression. Our results suggest that the signal generated by IFN-gamma during TNF-alpha/IFN-gamma cotreatment may require PKR to elicit enhanced NF-kappaB activity, and this signal may affect the stability of the IkappaBbeta protein.
authors.affiliation: Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Cheshire
authors.forename: B R
authors.initials: BR
authors.lastname: Williams
authors.forename: A S
authors.initials: AS
authors.lastname: Baldwin
mesh_terms: D015075:2-Aminopurine / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D020672:I-kappa B Proteins; D007371:Interferon-gamma / Q000494:pharmacology*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D016716:PC12 Cells; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019892:eIF-2 Kinase / Q000378:metabolism*