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Prostate apoptosis response 4 (Par-4), a novel substrate of caspase-3 during apoptosis activation

Parvesh Chaudhry1, Mohan Singh, Sophie Parent

  • 1Research Group in Molecular Oncology and Endocrinology, Department of Chemistry-Biology, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.

Molecular and Cellular Biology
|December 21, 2011
PubMed

Insights

Prostate apoptosis response 4 (Par-4) is cleaved by caspase-3 during apoptosis. This cleavage generates a fragment that enhances apoptosis and inhibits NF-κB signaling, revealing a new role for Par-4 in cancer cell death.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Prostate apoptosis response 4 (Par-4) is a known tumor suppressor protein.
  • The precise mechanisms regulating Par-4 function during apoptosis are not fully understood.

Purpose of the Study:

  • To investigate the role of caspase-3 in the regulation of Par-4 during apoptosis.
  • To identify the cleavage site and characterize the function of Par-4 fragments generated by caspase-3.

Main Methods:

  • Cisplatin-induced apoptosis in human cell lines.
  • Caspase-3 inhibition and knockdown experiments.
  • Site-directed mutagenesis and analysis of Par-4 fragments.
  • Western blotting and immunofluorescence assays.

Main Results:

  • Par-4 is a novel substrate of caspase-3, cleaved during cisplatin-induced apoptosis.
  • Caspase-3-deficient cells exhibit reduced Par-4 cleavage and apoptosis.
  • Cleavage occurs at an unconventional site (EEPD(131)↓G), generating a proapoptotic fragment.
  • The cleaved Par-4 fragment accumulates in the nucleus, inhibits NF-κB signaling, and enhances apoptosis.

Conclusions:

  • Caspase-3 directly cleaves Par-4, generating a functional fragment that promotes apoptosis.
  • This cleavage event represents a novel regulatory mechanism in the apoptotic pathway.
  • Targeting Par-4 cleavage may offer new therapeutic strategies for cancer treatment.

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