Saito Atsushi, Hayashi Takeshi, Okuno Shuzo, Ferrand-Drake Michel, Chan Pak H
Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
J Cereb Blood Flow Metab. 2003 Sep;23(9):1010-9. doi: 10.1097/01.WCB.0000080702.47016.FF.
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.
X染色体连锁凋亡抑制蛋白（XIAP）在多种细胞死亡刺激后参与凋亡调控。XIAP通过与半胱天冬酶结合来抑制半胱天冬酶反应，并通过与第二个线粒体衍生的半胱天冬酶激活剂（Smac）/DIABLO结合而受到抑制，从而严格控制凋亡性细胞死亡。然而，体内脑缺血后XIAP、Smac/DIABLO和半胱天冬酶之间的相互作用尚不清楚。为了阐明这一问题，作者使用体内短暂局灶性脑缺血模型，通过免疫组织化学、蛋白质印迹分析和免疫沉淀法，检测了XIAP、Smac/DIABLO和活化的半胱天冬酶-9之间的时间依赖性表达及相互作用。为了研究XIAP途径与半胱天冬酶级联反应的关系，给予了一种泛半胱天冬酶抑制剂。在再灌注损伤后的早期，XIAP与Smac/DIABLO的释放以及活化的半胱天冬酶-9的出现同时增加。短暂局灶性脑缺血后，XIAP与Smac/DIABLO以及与半胱天冬酶-9的结合，以及Smac/DIABLO与半胱天冬酶-9的结合同时达到峰值。半胱天冬酶抑制对XIAP和Smac/DIABLO的表达均无影响。这些结果表明，XIAP途径在半胱天冬酶级联反应的上游被激活，并且XIAP、Smac/DIABLO和半胱天冬酶-9之间的相互作用在短暂局灶性脑缺血后凋亡性神经元细胞死亡的调控中起重要作用。
