Expression of an IKKγ Splice Variant Determines IRF3 and Canonical NF-κB Pathway Utilization in ssRNA Virus Infection

Ping Liu, Muping Lu, Bing Tian, Kui Li, Roberto P. Garofalo, Deborah Prusak, Thomas G. Wood, Allan R. Brasier

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

Single stranded RNA (ssRNA) virus infection activates the retinoic acid inducible gene I (RIG-I)- mitochondrial antiviral signaling (MAVS) complex, a complex that coordinates the host innate immune response via the NF-κB and IRF3 pathways. Recent work has shown that the IκB kinase (IKK)γ scaffolding protein is the final common adapter protein required by RIG-I·MAVS to activate divergent rate-limiting kinases downstream controlling the NF-κB and IRF3 pathways. Previously we discovered a ubiquitous IKKγ splice-variant, IKKγΔ, that exhibits distinct signaling properties.Methodology/Principal Findings:We examined the regulation and function of IKKγ splice forms in response to ssRNA virus infection, a condition that preferentially induces full length IKKγ-WT mRNA expression. In IKKγΔ-expressing cells, we found increased viral translation and cytopathic effect compared to those expressing full length IKKγ-WT. IKKγΔ fails to support viral-induced IRF3 activation in response to ssRNA infections; consequently type I IFN production and the induction of anti-viral interferon stimulated genes (ISGs) are significantly attenuated. By contrast, ectopic RIG-I·MAVS or TNFα-induced canonical NF-κB activation is preserved in IKKγΔ expressing cells. Increasing relative levels of IKKγ-WT to IKKγΔ (while keeping total IKKγ constant) results in increased type I IFN expression. Conversely, overexpressing IKKγΔ (in a background of constant IKKγ-WT expression) shows IKKγΔ functions as a dominant-negative IRF3 signaling inhibitor. IKKγΔ binds both IKK-α and β, but not TANK and IKKε, indicating that exon 5 encodes an essential TANK binding domain. Finally, IKKγΔ displaces IKKγWT from MAVS explaining its domainant negative effect.Conclusions/Significance:Relative endogenous IKKγΔ expression affects cellular selection of inflammatory/anti-viral pathway responses to ssRNA viral infection.

Original languageEnglish (US)
Article numbere0008079
JournalPloS one
Volume4
Issue number11
DOIs
StatePublished - Dec 1 2009

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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