Negative regulation of cytochrome c-mediated oligomerization of Apaf-1 and activation of procaspase-9 by heat shock protein 90

EMBO J. 2000 Aug 15;19(16):4310-22. doi: 10.1093/emboj/19.16.4310.

Abstract

The release of cytochrome c from mitochondria results in the formation of an Apaf-1-caspase-9 apoptosome and induces the apoptotic protease cascade by activation of procaspase-3. The present studies demonstrate that heat shock protein 90 (Hsp90) forms a cytosolic complex with Apaf-1 and thereby inhibits the formation of the active complex. Immunodepletion of Hsp90 depletes Apaf-1 and thereby inhibits cytochrome c-mediated activation of caspase-9. Addition of purified Apaf-1 to Hsp90-depleted cytosolic extracts restores cytochrome c-mediated activation of procaspase-9. We also show that Hsp90 inhibits cytochrome c-mediated oligomerization of Apaf-1 and thereby activation of procaspase-9. Furthermore, treatment of cells with diverse DNA-damaging agents dissociates the Hsp90-Apaf-1 complex and relieves the inhibition of procaspase-9 activation. These findings provide the first evidence for a negative cytosolic regulator of cytochrome c-dependent apoptosis and for involvement of a chaperone in the caspase cascade.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Apoptosis
  • Apoptotic Protease-Activating Factor 1
  • Binding, Competitive
  • Caspase 3
  • Caspase 9
  • Caspases / metabolism*
  • Cell Line
  • Cell-Free System
  • Chromatography, Affinity
  • Cytochrome c Group / chemistry
  • Cytochrome c Group / metabolism*
  • Cytoplasm / metabolism
  • Cytosol / metabolism
  • Dose-Response Relationship, Drug
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Activation
  • Enzyme Precursors / metabolism*
  • Gene Expression Regulation, Enzymologic*
  • HSP90 Heat-Shock Proteins / metabolism*
  • Humans
  • Immunoblotting
  • Isoenzymes / metabolism
  • Models, Biological
  • Molecular Sequence Data
  • Precipitin Tests
  • Protein Binding
  • Protein Kinase C / metabolism
  • Protein Kinase C-delta
  • Proteins / chemistry
  • Proteins / metabolism*
  • Sequence Homology, Amino Acid
  • Transfection
  • U937 Cells

Substances

  • APAF1 protein, human
  • Apoptotic Protease-Activating Factor 1
  • Cytochrome c Group
  • Enzyme Precursors
  • HSP90 Heat-Shock Proteins
  • Isoenzymes
  • Proteins
  • PRKCD protein, human
  • Protein Kinase C
  • Protein Kinase C-delta
  • CASP3 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 9
  • Caspases