IKK-i signals through IRF3 and NFκB to mediate the production of inflammatory cytokines

S Sankar, H Chan, WJ Romanow, J Li, RJ Bates - Cellular signalling, 2006 - Elsevier
S Sankar, H Chan, WJ Romanow, J Li, RJ Bates
Cellular signalling, 2006Elsevier
IKK-i and TBK1 were recently identified as IKK-related kinases that are activated by toll-like
receptors TLR3 and TLR4. These kinases were identified as essential components of the
virus-activated as well as LPS-MyD88 independent kinase complex that phosphorylates
IRF3 and results in the production of cytokines involved in innate immunity. Both IKK-i and
TBK1 have also been implicated in the activation of the NFκB pathway but the precise
mechanism is not clear. Although the literature to date suggests that IKK-i and TBK1 play …
IKK-i and TBK1 were recently identified as IKK-related kinases that are activated by toll-like receptors TLR3 and TLR4. These kinases were identified as essential components of the virus-activated as well as LPS-MyD88 independent kinase complex that phosphorylates IRF3 and results in the production of cytokines involved in innate immunity. Both IKK-i and TBK1 have also been implicated in the activation of the NFκB pathway but the precise mechanism is not clear. Although the literature to date suggests that IKK-i and TBK1 play redundant roles in TLR3 and TLR4 signaling, recent data suggest that there may be subtle differences in the signaling pathways affected by these kinases. We have generated tetracycline-inducible stable cell lines that express a wild type or kinase-inactive mutant form of IKK-i. Our data suggest that expression of IKK-i can activate both NFκB and IRF3, leading to the production of several cytokines including interferon β. IKK-i most likely acts upstream of IKK2 to activate NFκB in these cells since expression of the kinase-inactive version of IKK-i did not inhibit TNFα mediated production of inflammatory cytokines. The data suggest that IKK-i is not involved in TNF-α mediated signaling but instead could likely play a role in activating IKK2 downstream of Toll-like receptor signaling. We also identified STAT1, Tyk2, and JAK1 as secondary mediators of IKK-i signaling as a result of interferon β production in these cells.
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