Interaction between XIAP and Smac/DIABLO in the mouse brain after transient focal cerebral ischemia.
The X chromosome-linked inhibitor-of-apoptosis protein (XIAP) contributes to apoptosis regulation after a variety of cell death stimuli. XIAP inhibits the caspase reaction via binding to caspases, and is inhibited via binding to the second mitochondria-derived activator of caspase (Smac)/DIABLO to tightly control apoptotic cell death. However, the interaction among XIAP, Smac/DIABLO, and caspases after in vivo cerebral ischemia is not well known. To clarify this issue, the authors examined time-dependent expression and interaction among XIAP, Smac/DIABLO, and activated caspase-9 by immunohistochemistry, Western blot analysis, and immunoprecipitation using an in vivo transient focal cerebral ischemia model. To examine the relationship of the XIAP pathway to the caspase cascade, a pan-caspase inhibitor was administered. XIAP increased concurrently with the release of Smac/DIABLO and the appearance of activated caspase-9 during the early period after reperfusion injury. The bindings of XIAP to Smac/DIABLO and to caspase-9 and the binding of Smac/DIABLO to caspase-9 reached a peak simultaneously after transient focal cerebral ischemia. Neither XIAP nor Smac/DIABLO expression was affected by caspase inhibition. These results suggest that the XIAP pathway was activated upstream of the caspase cascade and that interaction among XIAP, Smac/DIABLO, and caspase-9 plays an important role in the regulation of apoptotic neuronal cell death after transient focal cerebral ischemia.
Saito
Atsushi
A
Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
Hayashi
Takeshi
T
Okuno
Shuzo
S
Ferrand-Drake
Michel
M
Chan
Pak H
PH
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins; D001921:Brain / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D004789:Enzyme Activation; D002546:Ischemic Attack, Transient / Q000378:metabolism*; D008297:Male; D051379:Mice; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051636:X-Linked Inhibitor of Apoptosis Protein
D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D003574:Cytochrome c Group; C499605:Diablo protein, mouse; D024101:Mitochondrial Proteins; D011506:Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases