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Identification of an antiapoptotic protein complex at death receptors

M Sun1, L Song, Y Li

  • 1Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL 35294-0017, USA.

Cell Death and Differentiation
|October 11, 2008
PubMed

Insights

Researchers discovered an anti-apoptotic protein complex involving GSK3, DDX3, and cIAP-1 that regulates cell death signaling. This complex acts as a checkpoint, and its dysfunction is linked to cancer cell resistance to death receptor stimulation.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • The extrinsic apoptotic pathway, initiated by death receptor stimulation, is crucial for programmed cell death.
  • While the signaling cascade is well-studied, mechanisms that counteract apoptotic signals remain largely unknown.

Purpose of the Study:

  • To identify and characterize novel protein complexes that regulate death receptor signaling.
  • To elucidate the role of these complexes in counterbalancing apoptotic signals and in cancer cell resistance.

Main Methods:

  • Co-immunoprecipitation to identify protein-protein interactions.
  • Western blotting to detect protein cleavage and activation.
  • Caspase activity assays to measure apoptosis.
  • Cell viability assays in response to death receptor agonists.

Main Results:

  • An antiapoptotic complex containing glycogen synthase kinase-3 (GSK3), DDX3, and cellular inhibitor of apoptosis protein-1 (cIAP-1) was identified associated with death receptors.
  • Inhibition of GSK3 or DDX3 enhanced death receptor-induced apoptosis.
  • GSK3 restrains apoptosis by preventing death-inducing signaling complex formation and caspase-8 activation.
  • Cancer cells resistant to death receptor stimulation retained this antiapoptotic complex, which was overcome by GSK3 inhibitors.

Conclusions:

  • A novel antiapoptotic complex composed of GSK3, DDX3, and cIAP-1 acts as a checkpoint at death receptors, balancing apoptotic signaling.
  • Dysfunctional or persistent activity of this complex contributes to cancer cell resistance to apoptosis.
  • Targeting GSK3 offers a potential therapeutic strategy to overcome resistance in cancer cells.

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