The roles of two IkappaB kinase-related kinases in lipopolysaccharide and double stranded RNA signaling and viral infection.
Viral infection and stimulation with lipopolysaccharide (LPS) or double stranded RNA (dsRNA) induce phosphorylation of interferon (IFN) regulatory factor (IRF)-3 and its translocation to the nucleus, thereby leading to the IFN-beta gene induction. Recently, two IkappaB kinase (IKK)-related kinases, inducible IkappaB kinase (IKK-i) and TANK-binding kinase 1 (TBK1), were suggested to act as IRF-3 kinases and be involved in IFN-beta production in Toll-like receptor (TLR) signaling and viral infection. In this work, we investigated the physiological roles of these kinases by gene targeting. TBK1-deficient embryonic fibroblasts (EFs) showed dramatic decrease in induction of IFN-beta and IFN-inducible genes in response to LPS or dsRNA as well as after viral infection. However, dsRNA-induced expression of these genes was residually detected in TBK1-deficient cells and intact in IKK-i-deficient cells, but completely abolished in IKK-i/TBK1 doubly deficient cells. IRF-3 activation, in response not only to dsRNA but also to viral infection, was impaired in TBK1-deficient cells. Together, these results demonstrate that TBK1 as well as, albeit to a lesser extent, IKK-i play a crucial role in the induction of IFN-beta and IFN-inducible genes in both TLR-stimulated and virus-infected EFs.
Hemmi
Hiroaki
H
Department of Host Defense, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Takeuchi
Osamu
O
Sato
Shintaro
S
Yamamoto
Masahiro
M
Kaisho
Tsuneyasu
T
Sanjo
Hideki
H
Kawai
Taro
T
Hoshino
Katsuaki
K
Takeda
Kiyoshi
K
Akira
Shizuo
S
D000818:Animals; D002467:Cell Nucleus / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000502:physiology; D051550:I-kappa B Kinase; D050838:Interferon Regulatory Factor-3; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport; D012330:RNA, Double-Stranded / Q000235:genetics*; D012475:Salmonella / Q000276:immunology; D015398:Signal Transduction / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014777:Virus Diseases / Q000503:physiopathology*
D004268:DNA-Binding Proteins; D050838:Interferon Regulatory Factor-3; C494233:Irf3 protein, mouse; D008070:Lipopolysaccharides; D012330:RNA, Double-Stranded; D014157:Transcription Factors; C498588:Tbk1 protein, mouse; D017346:Protein Serine-Threonine Kinases; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse