Lack of involvement of mitochondrial factors in caspase activation in a Drosophila cell-free system.
Although mitochondrial proteins play well-defined roles in caspase activation in mammalian cells, the role of mitochondrial factors in caspase activation in Drosophila is unclear. Using cell-free extracts, we demonstrate that mitochondrial factors play no apparent role in Drosophila caspase activation. Cytosolic extract from apoptotic S2 cells, in which caspases were inhibited, induced caspase activation in cytosolic extract from normal S2 cells. Mitochondrial extract did not activate caspases, nor did it influence caspase activation by cytosolic extract. Silencing of Hid, Reaper, or Grim reduced caspase activation by apoptotic cell extract. Furthermore, a peptide representing the amino terminus of Hid was sufficient to activate caspases in cytosolic extract, and this activity was not enhanced by addition of mitochondria or mitochondrial lysate. The Hid peptide also induced apoptosis when introduced into S2 cells. These results suggest that caspase activation in Drosophila is regulated solely by cytoplasmic factors and does not involve any mitochondrial factors.
Means
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Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
Muro
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Clem
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RJ
D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D002474:Cell-Free System; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008928:Mitochondria / Q000378:metabolism / Q000528:radiation effects; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference / Q000502:physiology; D011994:Recombinant Proteins / Q000378:metabolism; D014466:Ultraviolet Rays
D029721:Drosophila Proteins; C108880:HID protein, Drosophila; D024101:Mitochondrial Proteins; D009479:Neuropeptides; D011994:Recombinant Proteins; C086973:rpr protein, Drosophila; D045304:Cytochromes c; D020169:Caspases