Altered cytochrome c display precedes apoptotic cell death in Drosophila.
Drosophila affords a genetically well-defined system to study apoptosis in vivo. It offers a powerful extension to in vitro models that have implicated a requirement for cytochrome c in caspase activation and apoptosis. We found that an overt alteration in cytochrome c anticipates programmed cell death (PCD) in Drosophila tissues, occurring at a time that considerably precedes other known indicators of apoptosis. The altered configuration is manifested by display of an otherwise hidden epitope and occurs without release of the protein into the cytosol. Conditional expression of the Drosophila death activators, reaper or grim, provoked apoptogenic cytochrome c display and, surprisingly, caspase activity was necessary and sufficient to induce this alteration. In cell-free studies, cytosolic caspase activation was triggered by mitochondria from apoptotic cells but identical preparations from healthy cells were inactive. Our observations provide compelling validation of an early role for altered cytochrome c in PCD and suggest propagation of apoptotic physiology through reciprocal, feed-forward amplification involving cytochrome c and caspases.
Department of Cell Biology and Neuroscience, University of Texas, Southwestern Medical Center, Dallas, Texas 75235-9039, USA.
J
J
Varkey
P
P
Chen
R
R
Jemmerson
J M
JM
Abrams
D000818:Animals; D000911:Antibodies, Monoclonal; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004789:Enzyme Activation; D005260:Female; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D000911:Antibodies, Monoclonal; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D017931:DNA Primers; D029721:Drosophila Proteins; D019476:Insect Proteins; D009479:Neuropeptides; D010455:Peptides; C108881:grim protein, Drosophila; C086973:rpr protein, Drosophila; D020169:Caspases