Caspase-2 acts upstream of mitochondria to promote cytochrome c release during etoposide-induced apoptosis.
DNA damage induced by the cancer chemotherapeutic drug etoposide triggers the onset of a series of intracellular events characteristic of apoptosis. Among the early changes observed is the release of cytochrome c from mitochondria, although the mechanism responsible for this effect is unclear. We demonstrate here a role for caspase-2 in etoposide-induced cytochrome c release. In particular, Jurkat T-lymphocytes treated with an irreversible caspase-2 inhibitor, benzyloxycarbonyl-Val-Asp-Val-Ala-Asp-fluoromethyl ketone (z-VDVAD-fmk), or stably transfected with pro-caspase-2 antisense (Casp-2/AS) are refractory to cytochrome c release stimulated by etoposide. Experiments performed using a reconstituted cell-free system indicate that etoposide-induced cytochrome c release by way of caspase-2 occurs independently of cytosolic factors, suggesting that the nuclear pool of pro-caspase-2 is critical to this process. Apart from inhibiting cytochrome c release, undermining caspase-2 activity results in an attenuation of downstream events, such as pro-caspase-9 and -3 activation, phosphatidylserine exposure on the plasma membrane, and DNA fragmentation. Taken together, our data indicate that caspase-2 provides an important link between etoposide-induced DNA damage and the engagement of the mitochondrial apoptotic pathway.
Robertson
John D
JD
Division of Toxicology, Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden. John.Robertson@imm.ki.se
Enoksson
Mari
M
Suomela
Minna
M
Zhivotovsky
Boris
B
Orrenius
Sten
S
D017209:Apoptosis / Q000187:drug effects*; D053143:Caspase 2; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D005047:Etoposide / Q000494:pharmacology*; D006801:Humans; D019169:Jurkat Cells; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology
D003574:Cytochrome c Group; D009842:Oligopeptides; C427308:benzoylcarbonyl-valyl-aspartyl-valyl-alanyl-aspartyl-fluoromethyl ketone; D005047:Etoposide; D053143:Caspase 2; D020169:Caspases