Ionomycin-activated calpain triggers apoptosis. A probable role for Bcl-2 family members

J Biol Chem. 2002 Jul 26;277(30):27217-26. doi: 10.1074/jbc.M202945200. Epub 2002 May 8.


Ubiquitous calpains (mu- and m-calpain) have been repeatedly implicated in apoptosis, but the underlying mechanism(s) remain(s) to be elucidated. We examined ionomycin-induced cell death in LCLC 103H cells, derived from a human large cell lung carcinoma. We detected hallmarks of apoptosis such as membrane blebbing, nuclear condensation, DNA ladder formation, caspase activation, and poly-(ADP-ribose)polymerase cleavage. Apoptosis was prevented by preincubation of the cells with the calpain inhibitor acetyl-calpastatin 27-peptide and the caspase inhibitor Z-DEVD-fmk, implicating both the calpains and caspases in the apoptotic process. The apoptotic events correlated in a calpastatin-inhibitable manner with Bid and Bcl-2 decrease and with activation of caspases-9, -3, and -7. In vitro both ubiquitous calpains cleaved recombinant Bcl-2, Bid, and Bcl-x(L) at single sites truncating their N-terminal regions. Binding studies revealed diminished interactions of calpain-truncated Bcl-2 and Bid with immobilized intact Bcl-2 family proteins. Moreover, calpain-cleaved Bcl-2 and Bid induced cytochrome c release from isolated mitochondria. We conclude that ionomycin-induced calpain activation promotes decrease of Bcl-2 proteins thereby triggering the intrinsic apoptotic pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Calcium / metabolism
  • Calpain / pharmacology*
  • Carcinoma, Large Cell / metabolism
  • Cell Nucleus / metabolism
  • Cell Separation
  • Cells, Cultured
  • Cytochrome c Group / metabolism
  • Cytoplasm / metabolism
  • DNA / metabolism
  • Enzyme Activation
  • Flow Cytometry
  • Humans
  • Ionomycin / pharmacology*
  • Ionophores / pharmacology
  • Lung Neoplasms / metabolism
  • Mitochondria / metabolism
  • Models, Molecular
  • Oligopeptides / pharmacology
  • Poly(ADP-ribose) Polymerases / metabolism
  • Protein Binding
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • Time Factors
  • Tumor Cells, Cultured


  • Cytochrome c Group
  • Ionophores
  • Oligopeptides
  • Proto-Oncogene Proteins c-bcl-2
  • benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone
  • Ionomycin
  • DNA
  • Poly(ADP-ribose) Polymerases
  • Calpain
  • Calcium