Caspase-2-induced apoptosis is dependent on caspase-9, but its processing during UV- or tumor necrosis factor-dependent cell death requires caspase-3.
Mammalian caspases are a family of cysteine proteases that plays a critical role in apoptosis. We have analyzed caspase-2 processing in human cell lines containing defined mutations in caspase-3 and caspase-9. Here we demonstrate that caspase-2 processing, during cell death induced by UV irradiation, depends both on caspase-9 and caspase-3 activity, while, during TNF-alpha-dependent apoptosis, capase-2 processing is independent of caspase-9 but still requires caspase-3. In vitro procaspase-2 is the preferred caspase cleaved by caspase-3, while caspase-7 cleaves procaspase-2 with reduced efficiency. We have also demonstrated that caspase-2-mediated apoptosis requires caspase-9 and that cells co-expressing caspase-2 and a dominant negative form of caspase-9 are impaired in activating a normal apoptotic response and release cytochrome c into the cytoplasm. Our findings suggest a role played by caspase-2 as a regulator of the mitochondrial integrity and open questions on the mechanisms responsible for its activation during cell death.
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Dipartimento di Scienze e Tecnologie Biomediche, Sezione di Biologia, Universita' di Udine, P. le Kolbe 4, Udine 33100, Italy.
Henderson
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Schneider
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Brancolini
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D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D053143:Caspase 2; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases / Q000235:genetics* / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D002460:Cell Line; D005260:Female; D005347:Fibroblasts; D019084:Fluorescent Antibody Technique, Indirect; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology / Q000528:radiation effects*; D015723:Gene Library; D006801:Humans; D008322:Mammals; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D014466:Ultraviolet Rays
D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C506433:CASP9 protein, human; D053143:Caspase 2; D053148:Caspase 3; D053179:Caspase 7; D053453:Caspase 9; D020169:Caspases