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TNF-induced mitochondrial changes and activation of apoptotic proteases are inhibited by A20

D Wissing1, H Mouritzen, M Jäättelä

  • 1Apoptosis Laboratory, Institute of Cancer Biology, Danish Cancer Society, Copenhagen.

Free Radical Biology & Medicine
|July 9, 1998
PubMed

Insights

A20 protein negatively regulates tumor necrosis factor (TNF) signaling. Overexpression of A20 blocks TNF-induced apoptosis, free radical generation, and mitochondrial dysfunction, specifically inhibiting TNF pathways.

Area of Science:

  • Molecular Biology
  • Cellular Signaling
  • Immunology

Background:

  • A20 is a cytokine-induced gene product.
  • A20 acts as a negative regulator of tumor necrosis factor (TNF).
  • It inhibits TNF-mediated apoptosis and transcription factor activation.

Purpose of the Study:

  • To investigate the role of A20 in TNF signaling pathways.
  • To determine the specific inhibitory effects of A20 on TNF-induced cellular events.

Main Methods:

  • Overexpression of A20 in cellular models.
  • Analysis of TNF-induced signaling events, including free radical generation, mitochondrial potential changes, and caspase activation.
  • Comparison with general caspase inhibitors (CrmA) and other stimuli (anti-Fas, doxorubicin).

Main Results:

  • A20 overexpression blocked early TNF-induced signaling, including free radical generation, mitochondrial depolarization, and caspase-3-like protease activation.
  • A general caspase inhibitor (CrmA) also inhibited TNF-induced mitochondrial changes, suggesting early caspase activation.
  • A20 did not inhibit mitochondrial or caspase activity induced by anti-Fas or doxorubicin, indicating specificity.

Conclusions:

  • A20 is a specific inhibitor of TNF signaling.
  • A20 acts upstream of TNF-induced free radical formation, mitochondrial potential loss, and caspase activation.

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