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Measuring Caspase Activity Using a Fluorometric Assay or Flow Cytometry
Published on: March 24, 2023
Spatial differences in active caspase-8 defines its role in T-cell activation versus cell death.
A Koenig1, J Q Russell, W A Rodgers
1Department of Medicine, Immunobiology Program, The University of Vermont College of Medicine, Burlington, VT 05405, USA. akoenig@uvm.edu
Cell Death and Differentiation
|July 12, 2008
Summary
The location of active caspase-8 determines its function. In T cells, caspase-8 aggregates in lipid rafts for proliferation but remains cytosolic for apoptosis signaling.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Caspase-8 is a cysteine-protease crucial for initiating apoptosis via death receptors.
- Caspase-8 also plays a vital role in T lymphocyte proliferation following T-cell antigen receptor (TCR) signaling.
Purpose of the Study:
- To investigate whether the distinct functions of caspase-8 arise from differences in activation magnitude or intracellular localization.
- To elucidate the spatial regulation of caspase-8 activity in T cells.
Main Methods:
- High-resolution multicolor confocal laser scanning microscopy to visualize active caspase-8 localization.
- Discontinuous sucrose gradient ultracentrifugation to isolate lipid raft and cytosolic cellular components.
- Assessing cleavage of the caspase-8 substrate BID following different stimulation pathways.
Main Results:
- Active caspase-8 aggregated within membrane lipid rafts in T cells stimulated with anti-CD3, suggesting formation of a signaling platform.
- Fas stimulation induced a predominantly cytosolic activation of caspase-8.
- The caspase-8 substrate BID was not cleaved in CD3-stimulated T cells but was cleaved after Fas engagement.
Conclusions:
- The intracellular localization of active caspase-8, whether in lipid rafts or the cytosol, dictates its functional outcome.
- This spatial sequestration model highlights how caspase-8's location influences its role in regulating cell cycling versus cell death.
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