Delineation of the caspase-9 signaling cascade.
In the intrinsic apoptosis pathway, mitochondrial disruption leads to the release of multiple apoptosis signaling molecules, triggering both caspase-dependent and -independent cell death. The release of cytochrome c induces the formation of the apoptosome, resulting in caspase-9 activation. Multiple caspases are activated downstream of caspase-9, however, the precise order of caspase activation downstream of caspase-9 in intact cells has not been completely resolved. To characterize the caspase-9 signaling cascade in intact cells, we employed chemically induced dimerization to activate caspase-9 specifically. Dimerization of caspase-9 led to rapid activation of effector caspases, including caspases-3, -6 and -7, as well as initiator caspases, including caspases-2, -8 and -10, in H9 and Jurkat cells. Knockdown of caspase-3 suppressed caspase-9-induced processing of the other caspases downstream of caspase-9. Silencing of caspase-6 partially inhibited caspase-9-mediated processing of caspases-2, -3 and -10, while silencing of caspase-7 partially inhibited caspase-9-induced processing of caspase-2, -3, -6 and -10. In contrast, deficiency in caspase-2, -8 or -10 did not significantly affect the caspase-9-induced caspase cascade. Our data provide novel insights into the ordering of a caspase signaling network downstream of caspase-9 in intact cells during apoptosis.
Guerrero
Alan D
AD
Department of Immunology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Chen
Min
M
Wang
Jin
J
D017209:Apoptosis; D053453:Caspase 9 / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism*; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism*; D034622:RNA Interference; D015398:Signal Transduction
D047908:Intracellular Signaling Peptides and Proteins; D045304:Cytochromes c; D053453:Caspase 9; D020169:Caspases