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Published on: March 5, 2018

Activation of caspases in p53-induced transactivation-independent apoptosis

C Gao1, N Tsuchida

  • 1Department of Molecular Cellular Oncology, Tokyo Medical and Dental University.

Japanese Journal of Cancer Research : Gann
|April 6, 1999
PubMed

Insights

p53-induced apoptosis, crucial for tumor suppression, proceeds independently of gene activation. This pathway involves sequential activation of caspases like CPP32 and ICH-1, bypassing the Fas pathway.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • p53 is a critical tumor suppressor.
  • The precise mechanisms of p53-induced apoptosis remain incompletely understood.
  • Understanding these pathways is vital for developing targeted cancer therapies.

Purpose of the Study:

  • To investigate the role of p53 transactivation activity in apoptosis.
  • To elucidate the specific caspase cascade involved in p53-mediated cell death.
  • To determine the involvement of the Fas pathway in p53-induced apoptosis.

Main Methods:

  • Utilized J138V5C cells with a temperature-sensitive p53 mutant.
  • Assessed apoptosis induction with and without cycloheximide (inhibitor of gene expression).
  • Employed Western blot analysis to detect protein cleavage (PARP, CPP32, ICH-1) and caspase inhibitors (Ac-DEVD-CHO).
  • Investigated the Fas pathway using neutralizing antibodies against Fas and Fas ligand.

Main Results:

  • p53-induced apoptosis occurred independently of p53 transactivation activity, as cycloheximide did not block it.
  • Cleavage of Poly(ADP-ribose) polymerase (PARP), CPP32, and ICH-1 precursors was observed during apoptosis.
  • A caspase inhibitor (Ac-DEVD-CHO) blocked the cleavage of ICH-1 and PARP, indicating CPP32 or a similar caspase is upstream of ICH-1.
  • The Fas pathway was not essential for p53-induced apoptosis, as Fas-neutralizing antibodies had no inhibitory effect.

Conclusions:

  • p53 induces apoptosis in Jurkat cells through a transactivation-independent mechanism.
  • The pathway involves the sequential activation of CPP32 (or other DEVD-sensitive caspases) and ICH-1.
  • This apoptotic cascade operates independently of the Fas signaling pathway.

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