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Published on: February 21, 2019
Establishing a blueprint for CED-3-dependent killing through identification of multiple substrates for this protease
Rebecca C Taylor1, Gabriela Brumatti, Shu Ito
1Molecular Cell Biology Laboratory, The Smurfit Institute of Genetics, Trinity College, Dublin 2, Ireland.
Abstract:
Genetic studies have established that the cysteine protease CED-3 plays a central role in coordinating programmed cell death in Caenorhabditis elegans. However, it remains unclear how CED-3 activation results in cell death because few substrates for this protease have been described. We have used a global proteomics approach to seek substrates for CED-3 and have identified 22 worm proteins that undergo CED-3-dependent proteolysis. Proteins that were found to be substrates for CED-3 included the cytoskeleton proteins actin, myosin light chain, and tubulin, as well as proteins involved in ATP synthesis, cellular metabolism, and chaperone function. We estimate that approximately 3% of the C. elegans proteome is susceptible to CED-3-dependent proteolysis. Notably, the endoplasmic reticulum chaperone calreticulin, which has been implicated in the recognition of apoptotic cells by phagocytes, was cleaved by CED-3 and was also cleaved by human caspases during apoptosis. Inhibitors of caspase activity blocked the appearance of calreticulin on the surface of apoptotic cells, suggesting a mechanism for the surface display of calreticulin during apoptosis. Further analysis of these substrates is likely to yield important insights into the mechanism of killing by CED-3 and its human caspase counterparts.
Insights
Researchers identified 22 substrates of the programmed cell death protease CED-3 in C. elegans using proteomics. This reveals new insights into cell death mechanisms and identifies calreticulin cleavage during apoptosis.
Area of Science:
- Molecular Biology
- Cell Biology
- Proteomics
Background:
- The cysteine protease CED-3 is crucial for programmed cell death in Caenorhabditis elegans.
- Understanding CED-3's substrates is key to elucidating its cell death mechanisms.
- Few CED-3 substrates have been previously identified.
Purpose of the Study:
- To identify novel substrates of the CED-3 protease using a global proteomics approach.
- To investigate the role of CED-3 substrates in programmed cell death.
- To explore the conserved function of CED-3 substrates, such as calreticulin, in apoptosis.
Main Methods:
- Global proteomics was employed to identify proteins cleaved by CED-3.
- Proteolytic products were analyzed to determine CED-3-dependent substrates.
- Calreticulin cleavage was examined in relation to apoptosis and caspase activity.
Main Results:
- Twenty-two C. elegans proteins were identified as substrates of CED-3-dependent proteolysis.
- Identified substrates include cytoskeletal proteins (actin, myosin light chain, tubulin), ATP synthesis, metabolism, and chaperone proteins.
- The endoplasmic reticulum chaperone calreticulin is cleaved by CED-3 and human caspases, and its surface display during apoptosis is caspase-dependent.
Conclusions:
- CED-3 proteolysis targets a diverse set of proteins, impacting cellular structure, metabolism, and function during programmed cell death.
- Calreticulin cleavage by CED-3 and caspases provides a mechanism for its surface display on apoptotic cells.
- Further study of these substrates will illuminate the conserved mechanisms of CED-3 and human caspases in cell death.
