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TAK1 MAPK kinase kinase mediates transforming growth factor-beta signaling by targeting SnoN oncoprotein for

Taisuke Kajino1, Emily Omori2, Shunsuke Ishii3

  • 1Department of Molecular Biology, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.

The Journal of Biological Chemistry
|February 6, 2007
PubMed

Insights

Transforming growth factor-beta (TGF-beta) signaling is regulated by SnoN degradation. This study identifies TAK1 as a key kinase that phosphorylates SnoN, targeting it for degradation and enabling TGF-beta responses.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Signal Transduction

Background:

  • Transforming growth factor-beta (TGF-beta) is crucial for physiological processes, mediated by Smad proteins.
  • The oncoprotein SnoN inhibits TGF-beta signaling by blocking Smad-dependent gene activation.
  • TGF-beta stimulation leads to rapid SnoN degradation, enabling target gene activation.

Purpose of the Study:

  • To investigate the role of TAK1 in the regulation of SnoN stability.
  • To elucidate the mechanism by which SnoN is degraded following TGF-beta stimulation.

Main Methods:

  • Co-immunoprecipitation to assess protein interactions.
  • In vitro kinase assays to determine phosphorylation.
  • Western blotting to analyze protein stability and degradation.
  • Analysis of gene expression in response to TGF-beta stimulation.

Main Results:

  • TAK1 directly interacts with and phosphorylates SnoN.
  • Phosphorylation of SnoN by TAK1 regulates its stability.
  • Inactivation of TAK1 inhibits TGF-beta-induced SnoN degradation.
  • Impaired SnoN degradation due to TAK1 inactivation leads to reduced induction of TGF-beta-responsive genes.

Conclusions:

  • TAK1 functions as a SnoN protein kinase.
  • TAK1-mediated phosphorylation targets SnoN for degradation.
  • TAK1 plays a critical role in modulating TGF-beta-dependent cellular responses by controlling SnoN stability.

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