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Published on: March 5, 2018

An interleukin-1beta converting enzyme-like protease is a key component of Fas-mediated apoptosis

A J Darmon1, R C Bleackley

  • 1Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.

The Journal of Biological Chemistry
|September 6, 1996
PubMed

Insights

Cytotoxic T lymphocytes (CTLs) use Fas-mediated killing, but key proteases like CPP32 and Interleukin-1beta converting enzyme (ICE) are not essential for target cell apoptosis. An alternate pathway likely exists for DNA fragmentation.

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Cytotoxic T lymphocytes (CTLs) eliminate target cells via granule- and Fas-mediated cytotoxicity.
  • The precise molecular mechanisms inducing target cell apoptosis in Fas-mediated killing are not fully understood.
  • Members of the interleukin-1beta converting enzyme (ICE)/Ced-3 family of cysteine proteases are implicated in this process.

Purpose of the Study:

  • To investigate the role of ICE/Ced-3 family proteases in Fas-mediated cytotoxicity.
  • To determine if CPP32 and ICE activities are essential for Fas-mediated target cell apoptosis and DNA fragmentation.

Main Methods:

  • Utilized activity assays and peptide inhibitors specific for ICE/Ced-3 proteases.
  • Measured DNA fragmentation and chromium (51Cr) release as indicators of cytotoxicity.
  • Assessed CPP32 cleavage and ICE activity in cell lysates from anti-Fas-treated target cells.

Main Results:

  • Specific inhibitors blocked DNA fragmentation and chromium release in some instances, but not universally.
  • Potent inhibitors of CPP32 and ICE did not inhibit DNA fragmentation in all Fas-mediated cytotoxicity cases.
  • CPP32 was not cleaved in all target cells during Fas killing, and ICE activity did not correlate with pro-IL-1beta cleavage.

Conclusions:

  • Fas-mediated killing does not strictly require CPP32 or ICE activity for target cell apoptosis.
  • An alternative pathway independent of CPP32 activity contributes to DNA fragmentation.
  • These findings challenge the essential role of CPP32 and ICE in Fas-mediated cytotoxicity.

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