Bax cleavage is mediated by calpain during drug-induced apoptosis

Oncogene. 1998 Sep 3;17(9):1069-78. doi: 10.1038/sj.onc.1202034.


The anti-apoptotic molecule Bcl-2 is located in the mitochondrial and endoplasmic reticulum membranes as well as the nuclear envelope. Although its location has not been as rigorously defined, the pro-apoptotic molecule Bax appears to be mainly a cytosolic protein which translocates to the mitochondria upon induction of apoptosis. Here we identify a protease activity in mitochondria-enriched membrane fractions from HL-60 cells capable of cleaving Bax which is absent from the cytosolic fraction. Bax protease activity is blocked in vitro by cysteine protease inhibitors including E-64 which distinguishes it from all known caspases and granzyme B, both of which are involved in apoptosis. Protease activity is also blocked by inhibitors against the calcium-activated neutral cysteine endopeptidase calpain. Partial purification of the Bax protease activity from HL-60 cell membrane fractions by column chromatography revealed that a calpain-like activity was the protease responsible for Bax cleavage. In addition, purified calpain enzymes cleaved Bax in a calcium-dependent manner. Pretreatment of HL-60 cells with the specific calpain inhibitor calpeptin effectively blocked both drug-induced Bax cleavage and calpain activation, but not PARP cleavage or cell death. These results suggest that calpains and caspases are activated during drug-induced apoptosis and that calpains, along with caspases, may be involved in modulating cell death by acting selectively on cellular substrates.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alanine / genetics
  • Amino Acid Sequence
  • Apoptosis / drug effects*
  • Aspartic Acid / genetics
  • Binding Sites / drug effects
  • Binding Sites / genetics
  • Calpain / antagonists & inhibitors
  • Calpain / isolation & purification
  • Calpain / pharmacology*
  • Camptothecin / analogs & derivatives
  • Camptothecin / antagonists & inhibitors
  • Camptothecin / pharmacology
  • Cell Death / drug effects
  • Cell Extracts / chemistry
  • Cell Membrane / drug effects
  • Cell Membrane / enzymology
  • Cysteine Proteinase Inhibitors / pharmacology*
  • Dipeptides / pharmacology
  • HL-60 Cells / drug effects
  • HL-60 Cells / enzymology
  • HL-60 Cells / ultrastructure
  • Humans
  • Hydrolysis / drug effects
  • Leucine / analogs & derivatives
  • Leucine / pharmacology
  • Molecular Sequence Data
  • Mutation / genetics
  • Poly(ADP-ribose) Polymerases / drug effects
  • Poly(ADP-ribose) Polymerases / metabolism
  • Proto-Oncogene Proteins / chemistry
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-bcl-2*
  • Substrate Specificity
  • bcl-2-Associated X Protein


  • BAX protein, human
  • Cell Extracts
  • Cysteine Proteinase Inhibitors
  • Dipeptides
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein
  • calpeptin
  • Aspartic Acid
  • 9-aminocamptothecin
  • Poly(ADP-ribose) Polymerases
  • Calpain
  • Leucine
  • Alanine
  • E 64
  • Camptothecin