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Caspase cascade proceeds rapidly after cytochrome c release from mitochondria in tumor necrosis factor-alpha-induced

Hiroshi Kawai1, Takuo Suzuki, Tetsu Kobayashi

  • 1Division of Biological Chemistry and Biologicals, National Institute of Health Sciences, Tokyo 158-8501, Japan. hkawai@jiu.ac.jp

Journal of Pharmacological Sciences
|February 9, 2007
PubMed

Insights

Tumor necrosis factor (TNF)-alpha triggers rapid apoptotic cell death in HeLa cells. Key events include cytochrome c release, caspase activation, and cell shrinkage, occurring sequentially within minutes.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Apoptosis Research

Background:

  • Apoptosis involves caspase activation and mitochondrial changes.
  • The precise timing of these events in tumor necrosis factor (TNF)-alpha-induced cell death requires clarification.

Purpose of the Study:

  • To elucidate the temporal sequence of caspase activation, cytochrome c release, mitochondrial depolarization, and morphological changes during TNF-alpha-induced apoptosis in HeLa cells.

Main Methods:

  • Single-cell analysis with high temporal resolution (0.5–1 min).
  • Utilized green fluorescent protein (GFP)-variant and chemical probes to monitor biochemical reactions.

Main Results:

  • Cytochrome c release, caspase activation, and cellular shrinkage consistently occurred in this order within 10 minutes.
  • Mitochondrial depolarization often followed caspase activation and shrinkage, suggesting it's not an initiating event.
  • Apoptosis proceeded only upon TNF-alpha exposure, indicating its critical role.

Conclusions:

  • The sequence of cytochrome c release, caspase activation, and cellular shrinkage represents a critical pathway in TNF-alpha-induced apoptosis.
  • Mitochondrial depolarization is a downstream event, not a trigger, in this apoptotic pathway.
  • TNF-alpha exposure rapidly drives the entire apoptotic process.

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