Electron transfer between cytochrome c and p66Shc generates reactive oxygen species that trigger mitochondrial apoptosis

Cell. 2005 Jul 29;122(2):221-33. doi: 10.1016/j.cell.2005.05.011.


Reactive oxygen species (ROS) are potent inducers of oxidative damage and have been implicated in the regulation of specific cellular functions, including apoptosis. Mitochondrial ROS increase markedly after proapoptotic signals, though the biological significance and the underlying molecular mechanisms remain undetermined. P66Shc is a genetic determinant of life span in mammals, which regulates ROS metabolism and apoptosis. We report here that p66Shc is a redox enzyme that generates mitochondrial ROS (hydrogen peroxide) as signaling molecules for apoptosis. For this function, p66Shc utilizes reducing equivalents of the mitochondrial electron transfer chain through the oxidation of cytochrome c. Redox-defective mutants of p66Shc are unable to induce mitochondrial ROS generation and swelling in vitro or to mediate mitochondrial apoptosis in vivo. These data demonstrate the existence of alternative redox reactions of the mitochondrial electron transfer chain, which evolved to generate proapoptotic ROS in response to specific stress signals.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Amino Acid Sequence
  • Animals
  • Apoptosis / physiology*
  • Cells, Cultured
  • Cytochromes c / metabolism*
  • Electron Transport
  • Hydrogen Peroxide / metabolism
  • Intracellular Membranes / metabolism
  • Mice
  • Mitochondria, Liver / metabolism*
  • Molecular Sequence Data
  • Mutation
  • Oxidation-Reduction
  • Permeability
  • Protein Structure, Tertiary
  • Reactive Oxygen Species / metabolism*
  • Shc Signaling Adaptor Proteins
  • Signal Transduction
  • Src Homology 2 Domain-Containing, Transforming Protein 1


  • Adaptor Proteins, Signal Transducing
  • Reactive Oxygen Species
  • Shc Signaling Adaptor Proteins
  • Shc1 protein, mouse
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Cytochromes c
  • Hydrogen Peroxide