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Enhancement of CPP32-like activity in the TNF-treated U937 cells by the proteasome inhibitors

E Fujita1, T Mukasa, T Tsukahara

  • 1Division of Development and Differentiation, NCNP, Tokyo, Japan.

Biochemical and Biophysical Research Communications
|July 5, 1996
PubMed

Insights

Proteasome inhibitors unexpectedly enhanced CPP32-like activity during apoptosis in U937 cells. This suggests the proteasome normally degrades CPP32-like proteases, protecting cells from apoptosis.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Background:

  • CPP32 is a protease crucial for apoptosis, structurally similar to C. elegans CED-3.
  • CPP32 activation is essential for apoptosis induced by anti-Fas and TNF.
  • Protease inhibitors were used to investigate CPP32-like activity regulation.

Purpose of the Study:

  • To examine the effects of protease inhibitors on CPP32-like activity in TNF-treated U937 cells.
  • To understand the role of proteasomes in regulating CPP32-like protease activity and apoptosis.

Main Methods:

  • U937 cells were treated with TNF to induce apoptosis.
  • Cells were treated with various protease inhibitors, including proteasome inhibitors (Z-LLnV, Z-LLL, lactacystin) and a cysteine protease inhibitor (E64d).
  • CPP32-like activity was measured by Ac-DEVD-MCA degrading activity.

Main Results:

  • Proteasome inhibitors significantly enhanced CPP32-like activity in TNF-treated U937 cells.
  • The cysteine protease inhibitor E64d did not enhance this activity.
  • Proteasome inhibitors alone did not affect CPP32-like activity in untreated U937 cells.

Conclusions:

  • The proteasome appears to play a protective role against apoptosis by degrading CPP32-like proteases or their processing enzymes.
  • Inhibition of the proteasome leads to increased CPP32-like protease activity, potentially promoting apoptosis.
  • These findings highlight a novel regulatory mechanism of apoptosis involving proteasome-mediated degradation of key apoptotic proteases.

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