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The molecular mechanism of apoptosis upon caspase-8 activation: quantitative experimental validation of a

Katsuya Kominami1, Jun Nakabayashi, Takeharu Nagai

  • 1Department of Animal Development and Physiology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan.

Biochimica Et Biophysica Acta
|July 18, 2012
PubMed

Insights

Activating just 1% of Caspase-8 (CASP8) initiates cell death signaling. This study quantifies the caspase cascade dynamics in living cells, revealing precise apoptotic signal transmission via the extrinsic pathway.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Signaling

Background:

  • Caspase-8 (CASP8) is crucial for extrinsic apoptosis via death receptors.
  • The precise kinetics and dynamics of CASP8-mediated signaling remain unclear.

Purpose of the Study:

  • To monitor CASP8 and caspase-3 activity in living cells using FRET biosensors.
  • To investigate the caspase cascade by regulating extrinsic death receptor signals.
  • To determine the molar concentrations of caspases and Bid in HeLa cells for signal transmission.

Main Methods:

  • Developed high-sensitivity FRET-based biosensors for real-time protease activity monitoring.
  • Systematically regulated extrinsic apoptotic signals in single cells.
  • Quantified molar concentrations of key caspases and Bid.

Main Results:

  • Less than 1% of activated CASP8 is sufficient to initiate apoptosis.
  • Validated a mathematical model for caspase cascade kinetics and dynamics.
  • Demonstrated precise hierarchical transmission of apoptotic signals.

Conclusions:

  • The study elucidates the quantitative aspects of the extrinsic apoptotic pathway.
  • Findings reveal the minimal CASP8 activation threshold for initiating apoptosis.
  • Provides a validated model for understanding caspase cascade dynamics.

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