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A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
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A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl

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Granzyme B induces BID-mediated cytochrome c release and mitochondrial permeability transition

J B Alimonti1, L Shi, P K Baijal

  • 1Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Manitoba R3E 0V9, Canada.

The Journal of Biological Chemistry
|December 15, 2000
PubMed

Insights

Granzyme B (GrB) triggers apoptosis through two distinct mitochondrial pathways: one involving BID for cytochrome c release, and another directly opening the permeability transition pore. This dual action leads to mitochondrial dysfunction and cell death.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Immunology

Background:

  • Apoptosis involves mitochondrial pathways, including the release of apoptogenic proteins and permeability transition.
  • The death receptor pathway is a triphasic process involving apical caspases, mitochondria, and effector caspases.
  • Granzyme B (GrB) is known to activate caspases and induce mitochondrial events like cytochrome c release.

Purpose of the Study:

  • To investigate the specific mechanisms by which Granzyme B (GrB) affects mitochondria.
  • To differentiate the pathways leading to cytochrome c release and permeability transition induced by GrB.
  • To elucidate the role of cytosolic proteins and caspases in GrB-mediated mitochondrial apoptosis.

Main Methods:

  • Utilized an in vitro cell-free system to study Granzyme B (GrB) interactions with mitochondria.
  • Analyzed the cleavage of cytosolic BID by GrB and its effect on cytochrome c release.
  • Investigated GrB's direct effects on mitochondrial permeability transition pore opening and proton gradient disruption.

Main Results:

  • Cleavage of cytosolic BID by GrB initiates mitochondrial cytochrome c release, with BID being the sole cytosolic factor responsible in vitro.
  • Granzyme B (GrB) directly induces mitochondrial permeability transition pore opening and disrupts the proton electrochemical gradient, independent of cytosolic S100 proteins.
  • While BID-mediated pathway is key, caspases also participate in cytochrome c release in certain cellular contexts.

Conclusions:

  • Granzyme B (GrB) employs two distinct mechanisms to induce mitochondrial dysfunction and apoptosis.
  • One pathway involves BID-mediated cytochrome c release, while the other involves direct mitochondrial action on the permeability transition pore.
  • These GrB-induced mitochondrial events culminate in cellular demise.

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