Functional Interactions of Transforming Growth Factor β-activated Kinase 1 with IκB Kinases to Stimulate NF-κB Activation

Abstract

Several mitogen-activated protein kinase kinase kinases play critical roles in nuclear factor-κB (NF-κB) activation. We recently reported that the overexpression of transforming growth factor-β-activated kinase 1 (TAK1), a member of the mitogen-activated protein kinase kinase kinase family, together with its activator TAK1-binding protein 1 (TAB1) stimulates NF-κB activation. Here we investigated the molecular mechanism of TAK1-induced NF-κB activation. Dominant negative mutants of IκB kinase (IKK) α and IKKβ inhibited TAK1-induced NF-κB activation. TAK1 activated IKKα and IKKβ in the presence of TAB1. IKKα and IKKβ were coimmunoprecipitated with TAK1 in the absence of TAB1. TAB1-induced TAK1 activation promoted the dissociation of active forms of IKKα and IKKβ from active TAK1, whereas the IKK mutants remained to interact with active TAK1. Furthermore, tumor necrosis factor-α activated endogenous TAK1, and the kinase-negative TAK1 acted as a dominant negative inhibitor against tumor necrosis factor-α-induced NF-κB activation. These results demonstrated a novel signaling pathway to NF-κB activation through TAK1 in which TAK1 may act as a regulatory kinase of IKKs. Several mitogen-activated protein kinase kinase kinases play critical roles in nuclear factor-κB (NF-κB) activation. We recently reported that the overexpression of transforming growth factor-β-activated kinase 1 (TAK1), a member of the mitogen-activated protein kinase kinase kinase family, together with its activator TAK1-binding protein 1 (TAB1) stimulates NF-κB activation. Here we investigated the molecular mechanism of TAK1-induced NF-κB activation. Dominant negative mutants of IκB kinase (IKK) α and IKKβ inhibited TAK1-induced NF-κB activation. TAK1 activated IKKα and IKKβ in the presence of TAB1. IKKα and IKKβ were coimmunoprecipitated with TAK1 in the absence of TAB1. TAB1-induced TAK1 activation promoted the dissociation of active forms of IKKα and IKKβ from active TAK1, whereas the IKK mutants remained to interact with active TAK1. Furthermore, tumor necrosis factor-α activated endogenous TAK1, and the kinase-negative TAK1 acted as a dominant negative inhibitor against tumor necrosis factor-α-induced NF-κB activation. These results demonstrated a novel signaling pathway to NF-κB activation through TAK1 in which TAK1 may act as a regulatory kinase of IKKs. nuclear factor κB mitogen-activated protein kinase MAPK kinase kinase transforming growth factor transforming growth factor β-activated kinase 1 IκB kinase NF-κB-inducing kinase tumor necrosis factor TAK1-binding protein 1 MAPK/extracellular signal-regulated kinase kinase kinase 1 c-Jun N-terminal kinase SDS-polyacrylamide gel electrophoresis glutathione S-transferase TNF-α receptor-associated factor MAPK kinase Transcription factor nuclear factor κB (NF-κB)1 is composed of homodimers and heterodimers of Rel family proteins and plays a pivotal role in the gene expression involved in inflammatory and immune responses (1Baeuerle P.A. Henkel T. Annu. Rev. Immunol. 1994; 12: 141-179Crossref PubMed Scopus (4584) Google Scholar, 2Verma I.M. Stevenson J.K. Schwarz E.M. Van Antwerp D. Miyamoto S. 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Virelizier J.L. Hay R.T. Arenzana-Seisdedos F. Oncogene. 1996; 12: 2425-2435PubMed Google Scholar, 14Roff M. Thompson J. Rodriguez M.S. Jacque J.M. Baleux F. Arenzana-Seisdedos F. Hay R.T. J. Biol. Chem. 1996; 271: 7844-7850Abstract Full Text Full Text PDF PubMed Scopus (206) Google Scholar, 15Weil R. Laurent-Winter C. Israel A. J. Biol. Chem. 1997; 272: 9942-9949Abstract Full Text Full Text PDF PubMed Scopus (101) Google Scholar). Diverse extracellular stimuli such as tumor necrosis factor (TNF)-α and interleukin-1β, phorbol esters, and environmental stresses lead to NF-κB activation utilizing the common mechanism for the IκB degradation, suggesting the diversity of the upstream signaling pathways for phosphorylation of IκB proteins. Several regulatory kinases involved in the signal-induced phosphorylation of IκB proteins have recently been reported. Two closely related kinases designated IκB kinase (IKK) α and IKKβ have been identified as components of the multiprotein IKK complex (500–900 kDa) that directly phosphorylates the critical Ser residues of IκB proteins (16DiDonato J.A. Hayakawa M. Rothwarf D.M. Zandi E. Karin M. Nature. 1997; 388: 548-554Crossref PubMed Scopus (1900) Google Scholar, 17Mercurio F. Zhu H. Murray B.W. Shevchenko A. Bennett B.L. Li J. Young D.B. Barbosa M. Mann M. Manning A. Rao A. Science. 1997; 278: 860-866Crossref PubMed Scopus (1841) Google Scholar, 18Zandi E. Rothwarf D.M. Delhase M. Hayakawa M. Karin M. Cell. 1997; 91: 243-252Abstract Full Text Full Text PDF PubMed Scopus (1575) Google Scholar, 19Woronicz J.D. Gao X. Cao Z. Rothe M. Goeddel D.V. Science. 1997; 278: 866-869Crossref PubMed Scopus (1065) Google Scholar, 20Regnier C.H. Song H.Y. Gao X. Goeddel D.V. Cao Z. Rothe M. Cell. 1997; 90: 373-383Abstract Full Text Full Text PDF PubMed Scopus (1070) Google Scholar). Together, IKKα and IKKβ form a heterodimer through their C-terminal leucine zipper motifs, and the functional IKK complex contains both IKK subunits. NF-κB-inducing kinase (NIK) is a member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, which was first identified as a TNF-α receptor-associated factor (TRAF) 2-interacting protein (21Malinin N.L. Boldin M.P. Kovalenko A.V. Wallach D. Nature. 1997; 385: 540-544Crossref PubMed Scopus (1160) Google Scholar). The ligand-mediated trimerization of the TNF-α receptor triggers the recruitment of NIK to TRAF2, and this association results in the activation of NIK, which in turn phosphorylates and activates IKKs. NIK also interacts with TRAF6, another member of the TRAF family, which is required for interleukin-1β-induced NF-κB activation (22Cao Z. Xiong J. Takeuchi M. Kurama T. Goeddel D.V. Nature. 1996; 383: 443-446Crossref PubMed Scopus (1117) Google Scholar). In addition, MAPK/extracellular signal-regulated kinase kinase kinase 1 (MEKK1), another member of the MAPKKK family, stimulates NF-κB activation by preferentially activating IKKβ over IKKα (23Nakano H. Shindo M. Sakon S. Nishinaka S. Mihara M. Yagita H. Okumura K. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 3537-3542Crossref PubMed Scopus (471) Google Scholar, 24Yin M.J. Christerson L.B. Yamamoto Y. Kwak Y.T. Xu S. Mercurio F. Barbosa M. Cobb M.H. Gaynor R.B. Cell. 1998; 93: 875-884Abstract Full Text Full Text PDF PubMed Scopus (232) Google Scholar, 25Chu Z.L. DiDonato J.A. Hawiger J. Ballard D.W. J. Biol. Chem. 1998; 273: 15891-15894Abstract Full Text Full Text PDF PubMed Scopus (134) Google Scholar). These findings suggest that several MAPKKKs play a key role in the NF-κB activation pathway by regulating the kinase activity of the IKK complex. However, little is known about the regulatory molecular mechanisms of the kinase activity of the IKK complex induced by diverse extracellular stimuli. Transforming growth factor (TGF) β-activated kinase 1 (TAK1) was first identified as a MAPKKK that can be activated by TGF-β and bone morphological protein (26Yamaguchi K. Shirakabe K. Shibuya H. Irie K. Oishi I. Ueno N. Taniguchi T. Nishida E. Matsumoto K. Science. 1995; 270: 2008-2011Crossref PubMed Scopus (1172) Google Scholar). TAK1 activity is regulated by its activator, TAK1-binding protein 1 (TAB1) (27Shibuya H. Yamaguchi K. Shirakabe K. Tonegawa A. Gotoh Y. Ueno N. Irie K. Nishida E. Matsumoto K. Science. 1996; 272: 1179-1182Crossref PubMed Scopus (517) Google Scholar). TAK1 is suggested to act as a MAPKKK in the c-Jun N-terminal kinase (JNK)/stress-activated protein kinase (SAPK) and the p38 MAPK cascades, in which TAK1 phosphorylates MAPK kinase (MKK) 4, MKK3, and MKK6 (28Moriguchi T. Kuroyanagi N. Yamaguchi K. Gotoh Y. Irie K. Kano T. Shirakabe K. Muro Y. Shibuya H. Matsumoto K. Nishida E. Hagiwara M. J. Biol. Chem. 1996; 271: 13675-13679Abstract Full Text Full Text PDF PubMed Scopus (406) Google Scholar, 29Shirakabe K. Yamaguchi K. Shibuya H. Irie K. Matsuda S. Moriguchi T. Gotoh Y. Matsumoto K. Nishida E. J. Biol. Chem. 1997; 272: 8141-8144Abstract Full Text Full Text PDF PubMed Scopus (298) Google Scholar). In addition, kinase 1 the activation of the pathway by TAK1 and kinase G. Z. J. Biol. Chem. 1997; 272: PubMed Scopus Google Scholar). However, the role of TAK1 in the signaling pathways is We recently reported that the overexpression of TAK1 together with stimulates NF-κB activation H. N. K. T. 1998; PubMed Scopus Google Scholar). In the we investigated the molecular mechanisms of TAK1-induced NF-κB activation. We functional of TAK1 with IKKα and In the activation of TAK1-induced two Ser residues in the activation of the were In of TAK1 were H. N. K. T. 1998; PubMed Scopus Google Scholar). is the in and was in the TAK1 was the in expression and as a The expression for and were H. N. K. T. 1998; PubMed Scopus Google Scholar). IKKα and IKKβ were from by The were as and for the of and for the of and for the of and and for the of IKKα and IKKβ were and of and the dominant negative mutants IKKα IKKα IKKβ and IKKβ were a of the were by were in with and at in were with expression the were and gel were with nuclear as H. R. K. T. M. J. PubMed Scopus Google Scholar). gene was by was by M. and were with 1 and were with of 1 and and for were with a for and with protein at for The were with and and the were by SDS-polyacrylamide gel electrophoresis was as H. N. K. T. 1998; PubMed Scopus Google Scholar). The were and were with the the an by the the were with of kinase and of at for the IKK kinase of were as a expression for was by the of expression for was by the The were by by The activity was by kinase was an and a kinase was with as a the The expression was by M. p38 MAPK activation was by its phosphorylation at both the and residues by the of with an p38 were with the the were with at for was in the We demonstrated the of TAK1 to NF-κB in a H. N. K. T. 1998; PubMed Scopus Google Scholar). the molecular mechanism of TAK1-induced NF-κB N-terminal TAK1 a kinase was in gel that TAK1 together with induced the nuclear of whereas the was In the activity was by the overexpression of TAK1 and 1 In addition, two inhibitory proteins, and IκBβ, were in both TAK1 and 1 The degradation of was by a that TAK1 may NF-κB through the was first identified as a TAK1 activator in a (27Shibuya H. Yamaguchi K. Shirakabe K. Tonegawa A. Gotoh Y. Ueno N. Irie K. Nishida E. Matsumoto K. Science. 1996; 272: 1179-1182Crossref PubMed Scopus (517) Google Scholar). we the molecular mechanism of the TAK1 activation by in and were with in and were for the of by was coimmunoprecipitated with and kinase TAK1 a SDS-polyacrylamide gel with TAK1, with TAK1, also with In addition, TAK1 to be as a of the association with The of TAK1 and may the phosphorylation of both proteins induced by their functional as been for several protein kinases 1 receptor-associated kinase H. Li S. Cao Z. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). this an in was the The phosphorylation of TAK1 and was TAK1 and were Furthermore, of the complex with the forms to the forms this of TAK1. The of was by the suggesting phosphorylation in TAB1. These results suggest that the association of with TAK1 the activation of TAK1, which TAK1 and phosphorylation of by TAK1 may be The degradation of IκB proteins by TAK1 the of the of the IKK complex in TAK1-induced NF-κB activation. this the of dominant negative mutants of the were The TAK1-induced nuclear of NF-κB was inhibited by the kinase mutants IKKα and IKKβ In TAK1-induced and p38 MAPK activation was inhibited by IKK mutants These results suggest that TAK1-induced NF-κB activation is by the IKK through the MAPK signaling The TAK1-induced of IKK kinase activity was the endogenous IKK kinase activity was by an in kinase as a The kinase activity was TAK1 and were whereas the IKK activity The of the IKK activity was by a and in which the critical Ser residues for were with The was to IKKβ as as suggesting that both IKK to the IKK results were by an kinase an which been to the IKK complex F. Zhu H. Murray B.W. Shevchenko A. Bennett B.L. Li J. Young D.B. Barbosa M. Mann M. Manning A. Rao A. Science. 1997; 278: 860-866Crossref PubMed Scopus (1841) Google Scholar). the of the two IKK N-terminal IKKα and IKKβ were with TAK1 and and the kinase of the were by an kinase TAK1, induced the kinase activity of IKKα with IKKβ activity was by TAK1 whereas IKKβ activity In addition, inhibited the IKKβ activity These results that TAK1 as an activator for IKKα and IKKβ in the signaling pathway of TAK1-induced NF-κB activation. NIK been to directly with both and their kinase J.D. Gao X. Cao Z. Rothe M. Goeddel D.V. Science. 1997; 278: 866-869Crossref PubMed Scopus (1065) Google Scholar, 20Regnier C.H. Song H.Y. Gao X. Goeddel D.V. Cao Z. Rothe M. Cell. 1997; 90: 373-383Abstract Full Text Full Text PDF PubMed Scopus (1070) Google Scholar). TAK1 is also a member of the MAPKKK family, we investigated the of TAK1 with IKKs. were with the expression for with and were for the presence of by with the The of TAK1 with IKKα was in the absence of However, the was TAK1 was activated by the of TAK1 with IKKβ was in the absence of In of NIK with both IKKα and IKKβ were through their active forms with IKKα and IKKβ and whereas this the to interact with The of with the that IKKα and IKKβ with both TAK1 and These results that TAK1 interacts with both IKK to their kinase of the activated protein kinases and have been to be However, a be the kinase the that the residues for phosphorylation was the of IKK mutants and were with in The that TAK1 and IKK mutants were in both the absence and presence of These results that the kinase of for the dissociation of TAK1 from in which TAK1 may the Ser residues in the activation of the IKKs. In addition, the of with the that IKK mutants in the presence of active TAK1, suggesting that the of Furthermore, and acted as dominant negative in TAK1-induced NF-κB activation These results that the activation is involved in TAK1-induced activation. TAK1 and to be in with whereas the expression of IKKβ was and a was in the presence of IKKα The of TAK1 and was the kinase of TAK1 and this was in kinase-negative mutants of TAK1 and IKKβ and may a novel regulatory mechanism of TAK1 kinase In endogenous TAK1 is activated by TNF-α in which the TAK1 activity was for its to K. Yamaguchi K. Shibuya H. Irie K. Matsuda S. Moriguchi T. Gotoh Y. Matsumoto K. Nishida E. J. Biol. Chem. 1997; 272: 8141-8144Abstract Full Text Full Text PDF PubMed Scopus (298) Google Scholar). Here we investigated the of TNF-α TAK1 activation in The in kinase as a that TNF-α activated endogenous TAK1 and the activation was at TAK1 activity was also together with its and phosphorylation which was to the from the overexpression TAK1 activation was by the activation of endogenous IKK which was at In TGF-β TAK1 activation as as IKK activation These results suggest that act as signal of the NF-κB activation pathway through the TNF-α this we the of kinase-negative TAK1 NF-κB activation. inhibited gene expression These results that the complex plays a role in NF-κB activation. NIK plays a key role in NF-κB activation through IKK activation J.D. Gao X. Cao Z. Rothe M. Goeddel D.V. Science. 1997; 278: 866-869Crossref PubMed Scopus (1065) Google Scholar, 20Regnier C.H. Song H.Y. Gao X. Goeddel D.V. Cao Z. Rothe M. Cell. 1997; 90: 373-383Abstract Full Text Full Text PDF PubMed Scopus (1070) Google Scholar, N.L. Boldin M.P. Kovalenko A.V. Wallach D. Nature. 1997; 385: 540-544Crossref PubMed Scopus (1160) Google Scholar). Here we investigated the of the NIK NIK acted as a dominant negative inhibitor against the NF-κB activation Furthermore, the NIK inhibited TAK1-induced NF-κB activation TAK1 was first identified as a MAPKKK that can be activated by TGF-β and bone morphological protein (26Yamaguchi K. Shirakabe K. Shibuya H. Irie K. Oishi I. Ueno N. Taniguchi T. Nishida E. Matsumoto K. Science. 1995; 270: 2008-2011Crossref PubMed Scopus (1172) Google and was reported to play a role in bone morphological protein signaling in H. H. N. Gotoh Y. Yamaguchi K. Irie K. Matsumoto K. Nishida E. Ueno N. EMBO J. 1998; 17: PubMed Scopus Google Scholar). TAK1 that the of the domain is and TAK1 H. N. K. T. 1998; PubMed Scopus Google Scholar, H. H. N. Gotoh Y. Yamaguchi K. Irie K. Matsumoto K. Nishida E. Ueno N. EMBO J. 1998; 17: PubMed Scopus Google Scholar). have that proteins involved in the signaling pathway from TGF-β and bone morphological protein C.H. K. P. Nature. 1997; PubMed Scopus Google Scholar, M. J. Dev. 1998; PubMed Scopus Google Scholar). The of kinase-negative TAK1 the the expression of suggesting TAK1 and proteins H. H. N. Gotoh Y. Yamaguchi K. Irie K. Matsumoto K. Nishida E. Ueno N. EMBO J. 1998; 17: PubMed Scopus Google Scholar). Here we demonstrated a novel of TAK1 as an activator of the IKK complex to NF-κB activation. However, little is known about the functional TGF-β signaling and the NF-κB activation We reported that TGF-β the nuclear of NF-κB in H. N. K. T. 1998; PubMed Scopus Google Scholar). In addition, we that TAK1 was activated by TGF-β in These results suggest that TAK1 is involved in the NF-κB activation pathway induced by extracellular stimuli In this we demonstrated that TNF-α activated TAK1 to NF-κB activation. been that NIK plays a role in NF-κB activation. that the TAK1-induced nuclear of NF-κB H. N. K. T. 1998; PubMed Scopus Google Scholar). In the NIK TAK1-induced gene expression in N. K. in We also the dominant negative of the NIK in These results suggest that TAK1 be a regulatory kinase of TAK1 may the NIK interact with and endogenous IKKs. the functional TAK1 and NIK in NF-κB activation kinase 1 is a kinase with expression in X. Genes Dev. 1996; PubMed Scopus Google Scholar, F. M. A. B.W. N. T. EMBO J. 1996; PubMed Scopus Google Scholar). been that kinase 1 activates the pathway by TAK1 G. Z. J. Biol. Chem. 1997; 272: PubMed Scopus Google Scholar). is to the of kinase 1 to NF-κB activation through TAK1, which may a of TAK1-induced NF-κB activation in In the we demonstrated that the recruitment of to TAK1 may both TAK1 and phosphorylation of TAB1. The C-terminal of were to be for and activating TAK1 (27Shibuya H. Yamaguchi K. Shirakabe K. Tonegawa A. Gotoh Y. Ueno N. Irie K. Nishida E. Matsumoto K. Science. 1996; 272: 1179-1182Crossref PubMed Scopus (517) Google Scholar). In the N-terminal domain the TAK1 domain as a dominant negative inhibitor in TGF-β signaling (27Shibuya H. Yamaguchi K. Shirakabe K. Tonegawa A. Gotoh Y. Ueno N. Irie K. Nishida E. Matsumoto K. Science. 1996; 272: 1179-1182Crossref PubMed Scopus (517) Google Scholar). In addition, the of from the of TAK1 the protein kinase active (26Yamaguchi K. Shirakabe K. Shibuya H. Irie K. Oishi I. Ueno N. Taniguchi T. Nishida E. Matsumoto K. Science. 1995; 270: 2008-2011Crossref PubMed Scopus (1172) Google Scholar). These findings suggest that TAK1 phosphorylates the C-terminal domain of and the N-terminal domain of TAK1. In a (26Yamaguchi K. Shirakabe K. Shibuya H. Irie K. Oishi I. Ueno N. Taniguchi T. Nishida E. Matsumoto K. Science. 1995; 270: 2008-2011Crossref PubMed Scopus (1172) Google Scholar, H. Yamaguchi K. Shirakabe K. Tonegawa A. Gotoh Y. Ueno N. Irie K. Nishida E. Matsumoto K. Science. 1996; 272: 1179-1182Crossref PubMed Scopus (517) Google Scholar). The of the phosphorylation of TAK1 the molecular mechanism of TAK1 activation by TAB1. The functional of MAPK in the signaling pathways to NF-κB activation have been The kinase that of the signal-regulated kinase pathway is involved in phorbol NF-κB activation by of X. J. Biol. Chem. 1997; 272: PubMed Scopus Google Scholar). MAPK that to the MAPK/extracellular signal-regulated kinase inhibitor and the p38 MAPK inhibitor were to the of the NF-κB S. E. K. G. J. Biol. Chem. 1998; 273: Full Text Full Text PDF PubMed Scopus Google Scholar). Several MAPKKKs NIK (21Malinin N.L. Boldin M.P. Kovalenko A.V. Wallach D. Nature. 1997; 385: 540-544Crossref PubMed Scopus (1160) Google M. S. T. S. M. J. S. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar, X. C. D. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google and H. K. K. U. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google were recently to have the to NIK and preferentially IKKα and (23Nakano H. Shindo M. Sakon S. Nishinaka S. Mihara M. Yagita H. Okumura K. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: 3537-3542Crossref PubMed Scopus (471) Google Scholar, Cao Z. Goeddel D.V. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: PubMed Scopus Google Scholar). Here we demonstrated that TAK1 is a member of the MAPKKK family that activates IKKs. TAK1 as as NIK interacts with both IKKα and In the of with been a was with the multiprotein IKK complex F. Zhu H. Murray B.W. Shevchenko A. Bennett B.L. Li J. Young D.B. Barbosa M. Mann M. Manning A. Rao A. Science. 1997; 278: 860-866Crossref PubMed Scopus (1841) Google Scholar). to that is a protein with a N-terminal regulatory domain S. Christerson L.B. J.M. Cobb M.H. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: PubMed Scopus Google the that the regulatory domain may play a role in the with IKKs. In the protein to the regulatory domain of to IKK kinase activity M.J. Christerson L.B. Yamamoto Y. Kwak Y.T. Xu S. Mercurio F. Barbosa M. Cobb M.H. Gaynor R.B. Cell. 1998; 93: 875-884Abstract Full Text Full Text PDF PubMed Scopus (232) Google Scholar). that MAPKKKs NF-κB activation through with through the signaling MAPKKKs by Ser residues in the activation kinase and EMBO J. 1994; PubMed Scopus (298) Google Scholar). These Ser residues in both IKKα and The Ser residues in IKKβ were to be for NF-κB activation. In the signaling pathway to NF-κB IKKβ mutants in which and with act as a dominant negative inhibitor and a active F. Zhu H. Murray B.W. Shevchenko A. Bennett B.L. Li J. Young D.B. Barbosa M. Mann M. Manning A. Rao A. Science. 1997; 278: 860-866Crossref PubMed Scopus (1841) Google Scholar). In addition, NIK activates IKKα by in the activation Cao Z. Goeddel D.V. Proc. Natl. Acad. Sci. U. S. A. 1998; 95: PubMed Scopus Google Scholar). In the we demonstrated the functional of the Ser residues in the activation of both IKK in TAK1-induced IKK activation. findings that the molecular mechanism of the of by TAK1 may be as TAK1 interacts with in The recruitment of to TAK1 activates the kinase activity of TAK1, phosphorylation by TAK1 and the of TAK1 may be The active TAK1 phosphorylates the Ser residues in the activation of in the dissociation of TAK1 from the kinase activity of IKKs. the of the multiprotein IKK complex and were S. G. C. S.T. R. F. R.J. Israel A. Cell. 1998; 93: Full Text Full Text PDF PubMed Scopus Google Scholar, D.M. Zandi E. G. Karin M. Nature. 1998; PubMed Scopus Google Scholar, Baeuerle P.A. Nature. 1998; PubMed Scopus Google Scholar). The of and the of of the IKK complex the regulatory mechanisms of IKK activation by TAK1. of TAK1 and was in the presence of IKKβ activation to the phosphorylation of IκB proteins in the which triggers the degradation of IκB proteins through the These results suggest a novel regulatory mechanism of TAK1 kinase activity in which protein degradation through a pathway be The IKK complex was first from as a kinase complex Maniatis T. Cell. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). In addition, M. R. K. D. R. R. C. M. J. 1998; 12: PubMed Scopus Google recently reported that a novel protein complex to was involved in the phosphorylation of the to and and the activation the that MAPKKKs activity by the Ser residues in the activation of subunits. of the regulatory mechanisms of of the complex the role of protein degradation in the signaling pathways to NF-κB activation. In we demonstrated that TAK1 is a regulatory kinase of that stimulates NF-κB activation. together with that the multiprotein composed of IKK and regulatory kinases such as TAK1, NIK, and may be involved in the signaling pathways to NF-κB activation by diverse extracellular stimuli. of the activation and the of TAK1 is to have in inflammatory in which NF-κB may play We to K. Matsumoto for and the We also to M. and M. for the of and an expression for We N. N. Y. T. and K. for and and Y. for