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Omi/HtrA2 promotes cell death by binding and degrading the anti-apoptotic protein ped/pea-15

Alessandra Trencia1, Francesca Fiory, Maria Alessandra Maitan

  • 1Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del CNR, Università degli Studi di Napoli Federico II, Naples 80131, Italy.

The Journal of Biological Chemistry
|August 26, 2004
PubMed

Insights

The pro-apoptotic Omi/HtrA2 protease degrades the anti-apoptotic PED/PEA-15 protein, promoting UVC-induced cell death. Omi/HtrA2

Area of Science:

  • Cellular and Molecular Biology
  • Apoptosis Research
  • Protein-Protein Interactions

Background:

  • PED/PEA-15 is a 15-kDa protein with broad anti-apoptotic functions.
  • Omi/HtrA2 is a mitochondrial serine protease that promotes apoptosis.
  • PED/PEA-15 and Omi/HtrA2 interactions are crucial in regulating cell death pathways.

Purpose of the Study:

  • To investigate the interaction between PED/PEA-15 and Omi/HtrA2.
  • To elucidate the role of this interaction in UVC-induced apoptosis.
  • To understand how Omi/HtrA2 affects PED/PEA-15 levels and function.

Main Methods:

  • Yeast two-hybrid screening to identify protein interactors.
  • In vitro binding assays with recombinant proteins.
  • Co-precipitation assays in cell extracts (293 and HeLa cells).
  • UVC irradiation to induce apoptosis and protein release.
  • Inhibition studies using ucf-101, a specific Omi/HtrA2 inhibitor.
  • Western blotting to assess protein expression levels and degradation.
  • Caspase activation assays and XIAP interaction studies.

Main Results:

  • Omi/HtrA2 specifically interacts with PED/PEA-15, binding both in vitro and in cell extracts.
  • UVC exposure triggers Omi/HtrA2 release from mitochondria and subsequent binding to cytoplasmic PED/PEA-15.
  • UVC-induced apoptosis leads to decreased cellular PED/PEA-15 levels, an effect inhibited by ucf-101.
  • Omi/HtrA2 directly degrades PED/PEA-15 in vitro.
  • PED/PEA-15 inhibits Omi/HtrA2-mediated apoptosis by preventing Omi/HtrA2 interaction with XIAP and subsequent caspase-3 activation.
  • The anti-apoptotic effect of PED/PEA-15 diminishes with increasing Omi/HtrA2 levels, modulated by ucf-101.

Conclusions:

  • Omi/HtrA2-mediated degradation of PED/PEA-15 is a key mechanism contributing to UVC-induced apoptosis.
  • PED/PEA-15 levels modulate Omi/HtrA2's ability to release XIAP inhibition on caspases.
  • The balance between Omi/HtrA2 and PED/PEA-15 levels dictates the cell's susceptibility to apoptosis following mitochondrial Omi/HtrA2 release.

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