Interaction and regulation of the Caenorhabditis elegans death protease CED-3 by CED-4 and CED-9.
In the nematode Caenorhabditis elegans, three genes, ced-3, ced-4, and ced-9, play critical roles in the induction and execution of the death pathway. Genetic studies have suggested that ced-9 controls programmed cell death by regulating ced-4 and ced-3. However, the mechanism by which CED-9 controls the activities of CED-4 and the cysteine protease CED-3, the effector arm of the cell-death pathway, remains poorly understood. Immunoprecipitation analysis demonstrates that CED-9 forms a multimeric protein complex with CED-4 and CED-3 in vivo. Expression of wild-type CED-4 promotes the ability of CED-3 to induce apoptosis in mammalian cells, which is inhibited by CED-9. The pro-apoptotic activity of CED-4 requires the expression of a functional CED-3 protease. Significantly, loss-of-function CED-4 mutants are impaired in their ability to promote CED-3-mediated apoptosis. Expression of CED-4 enhances the proteolytic activation of CED-3. We also show that CED-9 inhibits the formation of p13 and p15, two cleavage products of CED-3 associated with its proteolytic activation in vivo. Moreover, CED-9 inhibits the enzymatic activity of CED-3 promoted by CED-4. Thus, these results provide evidence that CED-4 and CED-9 regulate the activity of CED-3 through physical interactions, which may provide a molecular basis for the control of programmed cell death in C. elegans.
Wu
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Department of Pathology and Comprehensive Cancer Center, The University of Michigan Medical School, Ann Arbor, Michigan 48109, USA.
Wallen
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Inohara
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Nuñez
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D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D017173:Caenorhabditis elegans / Q000201:enzymology*; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D020169:Caspases; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation; D015801:Helminth Proteins / Q000378:metabolism*; D006801:Humans; D046911:Macromolecular Substances; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D013329:Structure-Activity Relationship; D014162:Transfection
D051017:Apoptosis Regulatory Proteins; D029742:Caenorhabditis elegans Proteins; D002135:Calcium-Binding Proteins; C089224:Ced-4 protein, C elegans; C087233:Ced-9 protein, C elegans; D015801:Helminth Proteins; D046911:Macromolecular Substances; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans