Cathepsin B contributes to TNF-alpha-mediated hepatocyte apoptosis by promoting mitochondrial release of cytochrome c

J Clin Invest. 2000 Nov;106(9):1127-37. doi: 10.1172/JCI9914.


TNF-alpha-induced apoptosis is thought to involve mediators from acidic vesicles. Cathepsin B (cat B), a lysosomal cysteine protease, has recently been implicated in apoptosis. To determine whether cat B contributes to TNF-alpha-induced apoptosis, we exposed mouse hepatocytes to the cytokine in vitro and in vivo. Isolated hepatocytes treated with TNF-alpha in the presence of the transcription inhibitor actinomycin D (AcD) accumulated cat B in their cytosol. Further experiments using cell-free systems indicated that caspase-8 caused release of active cat B from purified lysosomes and that cat B, in turn, increased cytosol-induced release of cytochrome c from mitochondria. Consistent with these observations, the ability of TNF-alpha/AcD to induce mitochondrial release of cytochrome c, caspase activation, and apoptosis of isolated hepatocytes was markedly diminished in cells from CatB(-/-) mice. Deletion of the CatB gene resulted in diminished liver injury and enhanced survival after treatment in vivo with TNF-alpha and an adenovirus construct expressing the IkappaB superrepressor. Collectively, these observations suggest that caspase-mediated release of cat B from lysosomes enhances mitochondrial release of cytochrome c and subsequent caspase activation in TNF-alpha-treated hepatocytes.

Publication types

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

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Biological Transport, Active / drug effects
  • Caspases / metabolism
  • Cathepsin B / deficiency
  • Cathepsin B / genetics
  • Cathepsin B / metabolism*
  • Cytochrome c Group / metabolism*
  • Cytosol / metabolism
  • Dactinomycin / pharmacology
  • Enzyme Activation / drug effects
  • Hepatocytes / cytology
  • Hepatocytes / drug effects*
  • Hepatocytes / metabolism*
  • Liver / drug effects
  • Liver / metabolism
  • Liver / pathology
  • Mice
  • Mice, Knockout
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Models, Biological
  • Signal Transduction
  • Tumor Necrosis Factor-alpha / metabolism
  • Tumor Necrosis Factor-alpha / pharmacology*


  • Cytochrome c Group
  • Tumor Necrosis Factor-alpha
  • Dactinomycin
  • Caspases
  • Cathepsin B