A Bax/Bak-independent mechanism of cytochrome c release.
Bax and Bak are multidomain pro-apoptotic members of the Bcl-2 family of proteins that regulate mitochondria-mediated apoptosis by direct modulation of mitochondrial membrane permeability. Since double-knock-out mouse embryonic fibroblasts with deficiency of Bax and Bak are resistant to multiple apoptotic stimuli, Bax and Bak are considered to be an essential gateway for various apoptotic signals. Here we showed that the combination of calcium ionophore A23187 and arachidonic acid induced cytochrome c release and caspase-dependent death of double-knock-out mouse embryonic fibroblasts, indicating that other mechanisms of cytochrome c release exist. Furthermore, A23187/arachidonic acid (ArA)-induced caspase-dependent death was significantly suppressed by the treatment of several serine protease inhibitors including 4-(2-aminoethyl)benzenesulfonylfluoride and l-1-chloro-3-(4-tosylamido)-4-phenyl-2-butanone but not the overexpression of anti-apoptotic Bcl-2 family of proteins or the inhibition of mitochondrial membrane permeability transition. These results indicate that there are at least two mechanisms of cytochrome c release leading to caspase activation, a Bax/Bak-dependent mechanism and a Bax/Bak-independent, but serine protease(s)-dependent, mechanism.
Mizuta
Takeshi
T
Laboratory of Molecular Genetics, Department of Medical Genetics, Osaka University Medical School, Osaka 565-0871, Japan.
Shimizu
Shigeomi
S
Matsuoka
Yousuke
Y
Nakagawa
Takashi
T
Tsujimoto
Yoshihide
Y
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D016718:Arachidonic Acid / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D020169:Caspases / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000201:enzymology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013450:Sulfones / Q000494:pharmacology; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000172:deficiency / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000172:deficiency / Q000378:metabolism*
C494773:Bak1 protein, mouse; C494827:Bax protein, mouse; D007476:Ionophores; D015842:Serine Proteinase Inhibitors; D013450:Sulfones; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D016718:Arachidonic Acid; C002010:4-(2-aminoethyl)benzenesulfonylfluoride; D000001:Calcimycin; D045304:Cytochromes c; D020169:Caspases