TAK1, but not TAB1 or TAB2, plays an essential role in multiple signaling pathways in vivo.

TGF-beta-activated kinase 1 (TAK1), a member of the MAPKKK family, is thought to be a key modulator of the inducible transcription factors NF-kappaB and AP-1 and, therefore, plays a crucial role in regulating the genes that mediate inflammation. Although in vitro biochemical studies have revealed the existence of a TAK1 complex, which includes TAK1 and the adapter proteins TAB1 and TAB2, it remains unclear which members of this complex are essential for signaling. To analyze the function of TAK1 in vivo, we have deleted the Tak1 gene in mice, with the resulting phenotype being early embryonic lethality. Using embryonic fibroblasts lacking TAK1, TAB1, or TAB2, we have found that TNFR1, IL-1R, TLR3, and TLR4-mediated NF-kappaB and AP-1 activation are severely impaired in Tak1(m/m) cells, but they are normal in Tab1(-/-) and Tab2(-/-) cells. In addition, Tak1(m/m) cells are highly sensitive to TNF-induced apoptosis. TAK1 mediates IKK activation in TNF-alpha and IL-1 signaling pathways, where it functions downstream of RIP1-TRAF2 and MyD88-IRAK1-TRAF6, respectively. However, TAK1 is not required for NF-kappaB activation through the alternative pathway following LT-beta signaling. In the TGF-beta signaling pathway, TAK1 deletion leads to impaired NF-kappaB and c-Jun N-terminal kinase (JNK) activation without impacting Smad2 activation or TGF-beta-induced gene expression. Therefore, our studies suggests that TAK1 acts as an upstream activating kinase for IKKbeta and JNK, but not IKKalpha, revealing an unexpectedly specific role of TAK1 in inflammatory signaling pathways.

[1]  D. Goeddel,et al.  Tumor necrosis factor (TNF)-mediated kinase cascades: bifurcation of nuclear factor-kappaB and c-jun N-terminal kinase (JNK/SAPK) pathways at TNF receptor-associated factor 2. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[2]  N. Perrimon,et al.  Sequential activation of signaling pathways during innate immune responses in Drosophila. , 2002, Developmental cell.

[3]  K. Irie,et al.  TAB2, a novel adaptor protein, mediates activation of TAK1 MAPKKK by linking TAK1 to TRAF6 in the IL-1 signal transduction pathway. , 2000, Molecular cell.

[4]  Tak W. Mak,et al.  Toll-like receptor 3-mediated activation of NF-κB and IRF3 diverges at Toll-IL-1 receptor domain-containing adapter inducing IFN-β , 2004 .

[5]  D. Goeddel,et al.  Embryonic Lethality, Liver Degeneration, and Impaired NF-κB Activation in IKK-β-Deficient Mice , 1999 .

[6]  Sankar Ghosh,et al.  Signaling to NF-kappaB. , 2004, Genes & development.

[7]  M. Kelliher,et al.  The distinct roles of TRAF2 and RIP in IKK activation by TNF-R1: TRAF2 recruits IKK to TNF-R1 while RIP mediates IKK activation. , 2000, Immunity.

[8]  D. Green,et al.  The Lymphotoxin-β Receptor Induces Different Patterns of Gene Expression via Two NF-κB Pathways , 2002 .

[9]  G. Stark,et al.  Interleukin-1 (IL-1) Receptor-Associated Kinase Leads to Activation of TAK1 by Inducing TAB2 Translocation in the IL-1 Signaling Pathway , 2001, Molecular and Cellular Biology.

[10]  K. Irie,et al.  TAB1: An Activator of the TAK1 MAPKKK in TGF-β Signal Transduction , 1996, Science.

[11]  M. Karin,et al.  The two NF-κB activation pathways and their role in innate and adaptive immunity , 2004 .

[12]  Zhijian J. Chen,et al.  Activation of the IκB Kinase Complex by TRAF6 Requires a Dimeric Ubiquitin-Conjugating Enzyme Complex and a Unique Polyubiquitin Chain , 2000, Cell.

[13]  S. Akira,et al.  TAB2 Is Essential for Prevention of Apoptosis in Fetal Liver but Not for Interleukin-1 Signaling , 2003, Molecular and Cellular Biology.

[14]  P. Cohen,et al.  Feedback control of the protein kinase TAK1 by SAPK2a/p38α , 2003, The EMBO journal.

[15]  R. Flavell,et al.  JunD mediates survival signaling by the JNK signal transduction pathway. , 2003, Molecular cell.

[16]  K. Irie,et al.  Role of TAK1 and TAB1 in BMP signaling in early Xenopus development , 1998, The EMBO journal.

[17]  B. Williams,et al.  Poly(dI·dC)-induced Toll-like Receptor 3 (TLR3)-mediated Activation of NFκB and MAP Kinase Is through an Interleukin-1 Receptor-associated Kinase (IRAK)-independent Pathway Employing the Signaling Components TLR3-TRAF6-TAK1-TAB2-PKR* , 2003, The Journal of Biological Chemistry.

[18]  Jongdae Lee,et al.  IAP Suppression of Apoptosis Involves Distinct Mechanisms: the TAK1/JNK1 Signaling Cascade and Caspase Inhibition , 2002, Molecular and Cellular Biology.

[19]  S. Akira,et al.  Toll-like receptors in innate immunity. , 2004, International immunology.

[20]  Christopher P Austin,et al.  The Knockout Mouse Project , 2004, Nature Genetics.

[21]  Shizuo Akira,et al.  Toll/IL-1 Receptor Domain-Containing Adaptor Inducing IFN-β (TRIF) Associates with TNF Receptor-Associated Factor 6 and TANK-Binding Kinase 1, and Activates Two Distinct Transcription Factors, NF-κB and IFN-Regulatory Factor-3, in the Toll-Like Receptor Signaling 1 , 2003, The Journal of Immunology.

[22]  T. Maniatis,et al.  Immune Activation of NF-κB and JNK Requires Drosophila TAK1* , 2003, Journal of Biological Chemistry.

[23]  G. Xiao,et al.  Induction of p100 Processing by NF-κB-inducing Kinase Involves Docking IκB Kinase α (IKKα) to p100 and IKKα-mediated Phosphorylation* , 2004, Journal of Biological Chemistry.

[24]  R. Surabhi,et al.  TAK1 is Critical for IκB Kinase-mediated Activation of the NF-κB Pathway , 2003 .

[25]  S. Wasserman,et al.  Targeting of TAK1 by the NF-kappa B protein Relish regulates the JNK-mediated immune response in Drosophila. , 2004, Genes & development.

[26]  Wolfgang Wurst,et al.  A public gene trap resource for mouse functional genomics , 2004, Nature Genetics.

[27]  Zhijian J. Chen,et al.  TAK1 is a ubiquitin-dependent kinase of MKK and IKK , 2001, Nature.

[28]  D. Green,et al.  RelB/p50 dimers are differentially regulated by TNF-α and lymphotoxin-β receptor activation: critical roles for p100 , 2003 .

[29]  David Baltimore,et al.  An Essential Role for NF-κB in Preventing TNF-α-Induced Cell Death , 1996, Science.

[30]  D. Wallach,et al.  MAP3K-related kinase involved in NF-KB induction by TNF, CD95 and IL-1 , 1997, Nature.

[31]  Michael Karin,et al.  Activation by IKKα of a Second, Evolutionary Conserved, NF-κB Signaling Pathway , 2001, Science.

[32]  J. Ninomiya-Tsuji,et al.  The kinase TAK1 can activate the NIK-IκB as well as the MAP kinase cascade in the IL-1 signalling pathway , 1999, Nature.

[33]  Mike Rothe,et al.  IκB Kinase-β: NF-κB Activation and Complex Formation with IκB Kinase-α and NIK , 1997 .

[34]  Zhengfan Jiang,et al.  Interleukin-1 (IL-1) Receptor-Associated Kinase-Dependent IL-1-Induced Signaling Complexes Phosphorylate TAK1 and TAB2 at the Plasma Membrane and Activate TAK1 in the Cytosol , 2002, Molecular and Cellular Biology.

[35]  David Baltimore,et al.  Embryonic lethality and liver degeneration in mice lacking the RelA component of NF-κB , 1995, Nature.

[36]  Seamus J. Martin,et al.  Suppression of TNF-α-Induced Apoptosis by NF-κB , 1996, Science.

[37]  M. Karin,et al.  Signal transduction by tumor necrosis factor and its relatives. , 2001, Trends in cell biology.

[38]  D. Goeddel,et al.  TNF-R1 Signaling: A Beautiful Pathway , 2002, Science.

[39]  B. Hogan,et al.  Bmp4 is required for the generation of primordial germ cells in the mouse embryo. , 1999, Genes & development.

[40]  T. Mak,et al.  Severe liver degeneration and lack of NF-kappaB activation in NEMO/IKKgamma-deficient mice. , 2000, Genes & development.

[41]  E. Harhaj,et al.  NF-κB-Inducing Kinase Regulates the Processing of NF-κB2 p100 , 2001 .

[42]  K. Irie,et al.  Identification of a Member of the MAPKKK Family as a Potential Mediator of TGF-β Signal Transduction , 1995, Science.

[43]  Jongdae Lee,et al.  TAK1 regulates multiple protein kinase cascades activated by bacterial lipopolysaccharide , 2000, Journal of leukocyte biology.

[44]  M. O’Connor,et al.  Expression of TAK1, a mediator of TGF-beta and BMP signaling, during mouse embryonic development. , 2003, Gene expression patterns : GEP.

[45]  Hideyuki Kobayashi,et al.  Hrs, a Mammalian Master Molecule in Vesicular Transport and Protein Sorting, Suppresses the Degradation of ESCRT Proteins Signal Transducing Adaptor Molecule 1 and 2* , 2005, Journal of Biological Chemistry.

[46]  B. Lemaître,et al.  Mutations in the Drosophila dTAK1 gene reveal a conserved function for MAPKKKs in the control of rel/NF-kappaB-dependent innate immune responses. , 2001, Genes & development.

[47]  Conrad C. Huang,et al.  BayGenomics: a resource of insertional mutations in mouse embryonic stem cells , 2003, Nucleic Acids Res..

[48]  R. Gaynor,et al.  Role of the TAB2‐related protein TAB3 in IL‐1 and TNF signaling , 2003, The EMBO journal.