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Updated: Sep 14, 2026

A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
05:20

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

Published on: November 28, 2014

Granzyme B-induced apoptosis requires both direct caspase activation and relief of caspase inhibition

Ing Swie Goping1, Michele Barry, Peter Liston

  • 1Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.

Immunity
|March 22, 2003
PubMed

Insights

Cytotoxic lymphocytes use Granzyme B to trigger apoptosis. This study reveals Granzyme B directly cleaves caspase 3 and activates mitochondria, crucial for cell death.

Area of Science:

  • Cellular Biology
  • Immunology
  • Molecular Biology

Background:

  • Cytotoxic lymphocytes initiate apoptosis via Granzyme B, cleaving effector caspases.
  • Bcl-2 expression confers resistance to Granzyme B, indicating a critical mitochondrial role.

Purpose of the Study:

  • To investigate the precise mechanisms of Granzyme B-induced apoptosis, particularly the roles of caspase activation and mitochondrial pathways.
  • To elucidate how Bcl-2 influences Granzyme B-mediated cell death.

Main Methods:

  • Utilized cells expressing a dominant-negative caspase 9 to assess apoptosome-independent pathways.
  • Analyzed caspase 3 cleavage products in Bcl-2-transfected cells.
  • Investigated the effects of XIAP and Smac/DIABLO on caspase processing.

Main Results:

  • Granzyme B-induced killing was resistant in Bcl-2-expressing cells, highlighting mitochondrial involvement.
  • Apoptosome-mediated caspase activation was not essential for Granzyme B-induced apoptosis.
  • Caspase 3 cleavage to p20 occurred in Bcl-2 transfectants, but processing to p17 was inhibited by Bcl-2, similar to XIAP.
  • This inhibition was reversed by Smac/DIABLO, indicating Granzyme B directly cleaves caspase 3.
  • Granzyme B also triggers mitochondrial disruption, releasing proteins that overcome caspase inhibition.

Conclusions:

  • Granzyme B induces apoptosis through two critical pathways: direct caspase 3 cleavage and mitochondrial outer membrane permeabilization.
  • The release of mitochondrial proteins is essential for overcoming caspase inhibition, such as by XIAP.
  • Effective cytotoxic lymphocyte-mediated killing requires the coordinated engagement of both direct caspase activation and mitochondrial pathways.

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