Deactivation of the kinase IKK by CUEDC2 through recruitment of the phosphatase PP1

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Despite rapid progress in elucidating the molecular mechanisms of activation of the kinase IKK, the processes that regulate IKK deactivation are still unknown. Here we demonstrate that CUE domain–containing 2 (CUEDC2) interacted with IKKα and IKKβ and repressed activation of the transcription factor NF-κB by decreasing phosphorylation and activation of IKK. Notably, CUEDC2 also interacted with GADD34, a regulatory subunit of protein phosphatase 1 (PP1). We found that IKK, CUEDC2 and PP1 existed in a complex and that IKK was released from the complex in response to inflammatory stimuli such as tumor necrosis factor. CUEDC2 deactivated IKK by recruiting PP1 to the complex. Therefore, CUEDC2 acts as an adaptor protein to target IKK for dephosphorylation and inactivation by recruiting PP1.

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Figure 1: CUEDC2 binds to IKKα and IKKβ and decreases their phosphorylation.
Figure 2: CUEDC2 inhibits NF-κB activation through IKK inactivation.
Figure 3: CUEDC2 inhibits IKK phosphorylation by interacting with IKK.
Figure 4: IKK transiently disassociates from CUEDC2 but is recruited to TRAF2.
Figure 5: CUEDC2 and GADD34 mediate the formation of a IKK-CUEDC2-GADD34-PP1 complex.
Figure 6: CUEDC2 induces IKK dephosphorylation by recruiting the GADD34-PP1 complex to IKK.
Figure 7: CUEDC2 inhibits TNF-induced gene expression.


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We thank Z.G. Liu (National Cancer Institute, National Institutes of Health) for human IKKα and IKKβ plasmids and TRAF2-deficient MEFs; M.W. Mayo (University of Virginia) for the p65 expression plasmid; X. Lin (Anderson Cancer Center) for the RIP expression vector; X.X. Li (Cleveland Clinic Foundation) for construction of pE-selectin-Luc; G. Haegeman (University of Gent, Gent) for the pIL-6-Luc plasmid; and Z.G. Liu for discussions and technical help. Supported by the National Natural Science Foundation of China (30525021, 30672357, 30500583 and 30321003), the Major State Basic Research Development Program of China (973 Program; 2004CB518800) and the National High Technology Research and Development Program of China (2006AA02Z340).

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H.-Y.L., A.-L.L. and X.-M.Z. contributed to all studies; H.L. contributed to the yeast two-hybrid experiments; C.-H.W. and J.-H.M. participated in study design and analyzed data; J.Z., W.-H.L., and X.P. developed the stable cell lines; T.Z. and W.-L.G. contributed to the preparation of antibodies; and Y.-F.G., J.-Y.Z. and P.-J.Z. did the primary macrophage study.

Correspondence to Ai-Ling Li or Xue-Min Zhang.

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Supplementary Figures 1–8, Supplementary Table 1 and Supplementary Methods (PDF 465 kb)

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