Neuronal Apoptosis Induced by DNA Damage

描述(申请人提供)：神经细胞凋亡在正常的大脑发育和神经退化中起着重要的作用。最近的研究结果表明，脑损伤后，这种类型的神经元死亡优先通过caspase激活的内在途径进行。线粒体细胞色素c(Cyto-c)向细胞质的释放在这一途径中起着核心作用。Cyto-c的释放是由Bcl2家族的促凋亡成员介导的，这些成员是在DNA损伤的情况下在受损的神经元中诱导的。另一方面，其他报道表明，线粒体释放的Cyto-c不足以诱导内在的细胞凋亡途径。细胞外信号调节蛋白激酶ERK1/2可以阻断caspase-9的激活，通过直接磷酸化原aspase-9促进细胞存活，尽管细胞外有细胞外信号调节的蛋白激酶ERK1/2抑制该途径的进展。抑制这种凋亡神经元保护机制的途径尚不清楚。在这一应用中，我们提出了DNA损伤、线粒体释放Cyto-c、促进生存的ERK1/2去磷酸化和失活、caspase激活和神经元死亡之间的可能联系。我们的工作假设是，DNA损伤诱导的神经元凋亡的进展依赖于P53介导的特异性双特异性磷酸酶(DUSPs)的激活，DUSPs能够通过选择性地灭活ERK1/2来促进Proaspase-9的处理。如果我们的假设是正确的，神经元损伤后抑制DUSP活性肯定是神经保护的。为了解决这一假说，我们提出了两个相关的特定目标：(1)检测DUSP基因家族成员在体外和体内脑创伤后对DNA损伤的反应；(2)评估可诱导的DUSP在抑制ERK1/2、caspase激活和神经元死亡中的作用。这项研究的结果可能对寻找新的治疗策略具有根本的影响，以治疗各种急性和慢性神经退行性疾病，其中DNA损伤和依赖于P53的细胞凋亡对神经元丢失的贡献非常显著。

DESCRIPTION (provided by applicant): Neuronal apoptosis plays an essential role in normal brain development and neurodegeneration. Results of recent studies indicate that after brain injury this type of neuronal death preferentially proceeds through the intrinsic pathway of caspase activation. The release of mitochondrial cytochrome c (Cyto-c) to the cytoplasm plays a central role in this pathway. Cyto-c release is mediated by pro-apoptotic members of Bcl-2 family, which are induced in injured neurons in response to DNA damage. On the other hand, other reports indicate that the release of Cyto-c from mitochondria is not sufficient for the induction of the intrinsic apoptotic pathway. Despite of Cyto-c release, progression of this pathway is inhibited by the extracellular signal-regulated protein kinases Erk1/2 able to block activation of caspase-9 and promote cell survival by direct phosphorylation of procaspase-9. A pathway, which restrains this protective mechanism in apoptotic neurons, remains unknown. In this application we propose a possible link between DNA damage, the release of Cyto-c from mitochondria, dephosphorylation and inactivation of pro-survival Erk1/2, activation of caspases, and neuronal death. Our working hypothesis is that the progression of DNA damage-induced apoptosis in neurons depends on p53-mediated activation of specific dual specificity phosphatases (DUSPs) able to promote processing of procaspase-9 through selective Erk1/2 inactivation. If our hypothesis is correct, inhibition of DUSP activity after neuronal injury must be neuroprotective. To address the hypothesis, we propose 2 related Specific Aims: (1) To examine neuronal expression of DUSP gene family members in response to DNA damage in vitro and after brain trauma in vivo and (2) To assess a role for inducible DUSPs in inhibition of Erk1/2, caspase activation, and neuronal death. Results of this study may have fundamental impact on identifying novel treatment strategies for a wide variety of acute and chronic neurodegenerative conditions where the contribution of DNA damage and p53-dependent apoptosis to neuronal loss is highly significant.