Establishing a blueprint for CED-3-dependent killing through identification of multiple substrates for this protease.
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.
Taylor
Rebecca C
RC
Molecular Cell Biology Laboratory, The Smurfit Institute of Genetics, Trinity College, Dublin 2, Ireland.
Brumatti
Gabriela
G
Ito
Shu
S
Hengartner
Michael O
MO
Derry
W Brent
WB
Martin
Seamus J
SJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D017173:Caenorhabditis elegans / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D037282:Calreticulin / Q000378:metabolism; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D006801:Humans; D018832:Molecular Chaperones; D010586:Phagocytes / Q000166:cytology / Q000378:metabolism; D020543:Proteome / Q000378:metabolism; D013379:Substrate Specificity / Q000502:physiology
D029742:Caenorhabditis elegans Proteins; D037282:Calreticulin; D003598:Cytoskeletal Proteins; D018832:Molecular Chaperones; D020543:Proteome; D000255:Adenosine Triphosphate; D020169:Caspases; C089223:ced-3 protein, C elegans