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Cleavage of the calpain inhibitor, calpastatin, during apoptosis

M I Pörn-Ares1, A Samali, S Orrenius

  • 1Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. Isabella.Ares@imm.ki.se

Cell Death and Differentiation
|January 23, 1999
PubMed

Insights

This study shows that caspases cleave calpastatin, a calpain inhibitor, during apoptosis. This suggests caspases regulate calpain activity in programmed cell death.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Biology

Background:

  • Calpain activity is crucial for apoptosis execution in some models.
  • Calpastatin is the physiological inhibitor of calpains.

Purpose of the Study:

  • To investigate the cleavage of calpastatin during apoptosis.
  • To determine the role of caspases and calpains in calpastatin cleavage.

Main Methods:

  • Induction of apoptosis in Jurkat T-lymphocytes and U937 cells using anti-CD95 antibody, staurosporine, or TNF.
  • Analysis of calpastatin cleavage by Western blotting.
  • Inhibition studies using caspase and calpain inhibitors.
  • In vitro cleavage assays with purified enzymes.

Main Results:

  • Calpastatin (110-120 kDa) was cleaved to a 65-70 kDa form during apoptosis.
  • Calpastatin cleavage occurred concurrently with poly(ADP-ribose) polymerase cleavage.
  • Caspase inhibitors blocked calpastatin cleavage in all tested apoptotic systems.
  • Calpain inhibitor I only partially inhibited cleavage during TNF-induced apoptosis.
  • Recombinant caspase-3, calpain I, and calpain II cleaved calpastatin in vitro.

Conclusions:

  • Caspases, particularly caspase-3, likely cleave calpastatin during apoptosis.
  • Caspase-mediated cleavage of calpastatin may regulate calpain activity in programmed cell death.

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