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A Colorimetric Assay that Specifically Measures Granzyme B Proteolytic Activity: Hydrolysis of Boc-Ala-Ala-Asp-S-Bzl
Published on: November 28, 2014
Hop cleavage and function in granzyme B-induced apoptosis
Andrew J Bredemeyer1, Patricia E Carrigan, Todd A Fehniger
1Division of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
The Journal of Biological Chemistry
|September 29, 2006
Summary
Granzyme B (GzmB) cleaves Hop, a protein involved in apoptosis regulation. However, Hop cleavage does not alter cell sensitivity to GzmB-induced cell death, suggesting it may not be a key factor in this process.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Granzyme B (GzmB) is a cytotoxic protease crucial for inducing apoptosis in target cells.
- GzmB initiates cell death through multiple pathways, as no single substrate is essential.
- Hop (Hsp70/Hsp90-organizing protein) was previously identified as a GzmB substrate.
Purpose of the Study:
- To investigate the role of Hop cleavage by GzmB in regulating apoptosis.
- To determine if Hop has an anti-apoptotic function that is disrupted by GzmB.
- To assess if Hop levels influence susceptibility to GzmB-induced cell death.
Main Methods:
- In vitro cleavage assays of Hop by GzmB.
- Analysis of Hop cleavage in cells undergoing GzmB-induced apoptosis.
- Assessing cell death in cells expressing GzmB-resistant Hop or with reduced Hop levels.
Main Results:
- Hop was directly cleaved by GzmB both in vitro and in apoptotic cells.
- Cleavage fragments of Hop did not induce cell death.
- Neither overexpression of GzmB-resistant Hop nor significant reduction in Hop levels altered GzmB-induced cell death susceptibility.
Conclusions:
- Hop cleavage by GzmB does not determine the threshold for GzmB-induced apoptosis.
- Hop may be an 'innocent bystander' or facilitate apoptosis with other GzmB substrates.
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