Niizuma Kuniyasu, Endo Hidenori, Nito Chikako, Myer D Jeannie, Kim Gab Seok, Chan Pak H
Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA 94305-5487, USA.
Proc Natl Acad Sci U S A. 2008 Oct 21;105(42):16368-73. doi: 10.1073/pnas.0806222105. Epub 2008 Oct 9.
A brief period of global brain ischemia, such as that induced by cardiac arrest or cardiopulmonary bypass surgery, causes cell death in vulnerable hippocampal CA1 pyramidal neurons days after reperfusion. Although numerous factors have been suggested to account for this phenomenon, the mechanisms underlying it are poorly understood. We describe a cell death signal called the PIDDosome, a protein complex of p53-induced protein with a death domain (PIDD), receptor-interacting protein-associated ICH-1/CED-3 homologous protein with a death domain (RAIDD), and procaspase-2. We induced 5 min of transient global cerebral ischemia (tGCI) using bilateral common carotid artery occlusion with hypotension. Western blot analysis showed that expression of twice-cleaved fragment of PIDD (PIDD-CC) increased in the cytosolic fraction of the hippocampal CA1 subregion and preceded procaspase-2 activation after tGCI. Caspase-2 cleaved Bid in brain homogenates. Co-immunoprecipitation and immunofluorescent studies demonstrated that PIDD-CC, RAIDD, and procaspase-2 were co-localized and bound directly, which indicates the formation of the PIDD death domain complex. Furthermore, we tested inhibition of PIDD expression by using small interfering RNA (siRNA) treatment that was initiated 48 h before tGCI. Administration of siRNA against PIDD decreased not only expression of PIDD-CC, but also activation of procaspase-2 and Bid, resulting in a decrease in histological neuronal damage and DNA fragmentation in the hippocampal CA1 subregion after tGCI. These results imply that PIDD plays an important role in procaspase-2 activation and delayed CA1 neuronal death after tGCI. We propose that PIDD is a hypothetical molecular target for therapy against neuronal death after tGCI.
短暂的全脑缺血，如心脏骤停或体外循环手术所引发的缺血，会在再灌注数天后导致易损的海马CA1锥体神经元发生细胞死亡。尽管已有众多因素被认为与这一现象有关，但其潜在机制仍知之甚少。我们描述了一种名为PIDDosome的细胞死亡信号，它是由p53诱导的含死亡结构域蛋白（PIDD）、与受体相互作用蛋白相关的含死亡结构域的ICH-1/CED-3同源蛋白（RAIDD）和procaspase-2组成的蛋白复合物。我们通过双侧颈总动脉闭塞合并低血压诱导5分钟的短暂全脑缺血（tGCI）。蛋白质印迹分析表明，PIDD的二次切割片段（PIDD-CC）在海马CA1亚区的胞质部分表达增加，且在tGCI后先于procaspase-2激活。Caspase-2在脑匀浆中切割Bid。免疫共沉淀和免疫荧光研究表明，PIDD-CC、RAIDD和procaspase-2共定位且直接结合，这表明形成了PIDD死亡结构域复合物。此外，我们在tGCI前48小时开始使用小干扰RNA（siRNA）处理来测试对PIDD表达的抑制作用。给予针对PIDD的siRNA不仅降低了PIDD-CC 的表达，还降低了procaspase-2和Bid的激活，导致tGCI后海马CA1亚区的组织学神经元损伤和DNA片段化减少。这些结果表明，PIDD在tGCI后procaspase-2激活和延迟的CA1神经元死亡中起重要作用。我们提出，PIDD是tGCI后神经元死亡治疗的一个潜在分子靶点。
