The role of cytochrome c in caspase activation in Drosophila melanogaster cells.
The release of cytochrome c from mitochondria is necessary for the formation of the Apaf-1 apoptosome and subsequent activation of caspase-9 in mammalian cells. However, the role of cytochrome c in caspase activation in Drosophila cells is not well understood. We demonstrate here that cytochrome c remains associated with mitochondria during apoptosis of Drosophila cells and that the initiator caspase DRONC and effector caspase DRICE are activated after various death stimuli without any significant release of cytochrome c in the cytosol. Ectopic expression of the proapoptotic Bcl-2 protein, DEBCL, also fails to show any cytochrome c release from mitochondria. A significant proportion of cellular DRONC and DRICE appears to localize near mitochondria, suggesting that an apoptosome may form in the vicinity of mitochondria in the absence of cytochrome c release. In vitro, DRONC was recruited to a >700-kD complex, similar to the mammalian apoptosome in cell extracts supplemented with cytochrome c and dATP. These results suggest that caspase activation in insects follows a more primitive mechanism that may be the precursor to the caspase activation pathways in mammals.
Dorstyn
Loretta
L
Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Adelaide SA 5000, Australia.
Read
Stuart
S
Cakouros
Dimitrios
D
Huh
Jun R
JR
Hay
Bruce A
BA
Kumar
Sharad
S
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D002451:Cell Compartmentation / Q000235:genetics; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D046911:Macromolecular Substances; D008928:Mitochondria / Q000201:enzymology*; D015398:Signal Transduction / Q000502:physiology*
D003574:Cytochrome c Group; D029721:Drosophila Proteins; D046911:Macromolecular Substances; D020169:Caspases; C109171:drICE protein, Drosophila; C118731:dronc protein, Drosophila