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IkappaB kinase beta phosphorylates Dok1 serines in response to TNF, IL-1, or gamma radiation

Sanghoon Lee1, Charlotte Andrieu, Frédéric Saltel

  • 1International Agency for Research on Cancer, 150 Cours Albert Thomas, 69008 Lyon, France.

Proceedings of the National Academy of Sciences of the United States of America
|December 3, 2004
PubMed

Insights

IkappaB kinase beta (IKKbeta) phosphorylates Dok1, a protein regulating cell growth and migration. This phosphorylation is crucial for Dok1

Area of Science:

  • Cellular signaling pathways
  • Protein phosphorylation
  • Tyrosine kinase signaling

Background:

  • Dok1 is a key substrate for Ras-GTPase-activating protein, influencing cell growth and migration.
  • The precise regulatory mechanisms of Dok1 activity, particularly its interaction with kinases, remain incompletely understood.

Purpose of the Study:

  • To investigate the association and phosphorylation of Dok1 by IkappaB kinase beta (IKKbeta).
  • To elucidate the functional consequences of IKKbeta-mediated Dok1 phosphorylation on cellular processes.

Main Methods:

  • Co-immunoprecipitation assays to detect Dok1-IKKbeta interaction.
  • In vitro kinase assays using recombinant IKKbeta and Dok1 peptides.
  • Site-specific phospho-antibody analysis to detect Dok1 phosphorylation in vivo.
  • Site-directed mutagenesis of Dok1 to alanine or glutamate at specific serine residues.

Main Results:

  • IKKbeta directly associates with and phosphorylates Dok1 at serine residues S(439), S(443), S(446), and S(450) in human cells.
  • Stimuli such as TNF-alpha, IL-1, and gamma radiation induce Dok1 phosphorylation at these sites.
  • Mutating these serine residues to alanine abrogates IKKbeta phosphorylation and significantly alters Dok1's regulation of ERK1/2 phosphorylation, cell growth, and cell motility.

Conclusions:

  • IKKbeta plays a critical role in regulating Dok1 function through direct phosphorylation.
  • The identified serine residues are essential for Dok1's inhibitory effects on growth and its promotion of cell motility.
  • These findings highlight a novel regulatory axis involving IKKbeta and Dok1 in cellular responses to growth factors and stress.

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