The integrated stress response and oligodendrocyte survival after spinal cord injury

抽象的。我们确定内质网应激反应(ERSR)是治疗干预的潜在靶点 防止脊髓损伤(SCI)后脑白质丢失和运动障碍。具体地说，信号 涉及ERSR激酶PERK、PERK靶标延伸起始因子2α(eIF2α)的通路，以及 PERK激活的转录因子CHOP可能以时间依赖的方式被操纵以促进脊髓损伤 恢复。PERK信号与综合应激反应(ISR)有部分重叠，通过几个 应激激活的激酶，导致磷酸化eIF2α(PEIF2α)水平升高，蛋白质短暂抑制 转录因子ATF4的合成和激活。ATF4调控CHOP及其相关基因 ROS代谢、翻译调节和氨基酸合成。通过这种方式，ISR尝试恢复 动态平衡。ISR的过度和长期激活会导致合成代谢相关的氧化应激， 线粒体损伤、细胞死亡和炎症。支持ISR的刺激，如缺氧，缺乏营养， 脊髓损伤后存在氧化应激和内质网应激。然而，ISR主要组件的作用- 除PERK以外的eif2α激酶及其共同的下游靶标atf4--尚未在 挫伤性脊髓损伤后脑白质丢失的情况。我们的首要假设是ISR扮演着关键角色 在挫伤脊髓损伤的发病机制中可能通过促进OL/OPC死亡和脑白质丢失而发挥作用。目标1将研究 4种上游ISR激酶(PERK、PKR、GCN2、HRI)在不同应激源激活中的作用 使eIF2α磷酸化，进而抑制全球翻译并增强应激诱导的基因表达。 我们将在体外OPC/OL和体内脊髓损伤中使用先前优化的功能获得和功能丧失的组合 使用药物抑制剂以及HRI-/-、PKR-/-和GCN2-/-小鼠的检测。来自ER的初步数据 应激OPC或SCI组织表现为这些激酶的激活以及ISR的代偿性激活 当PERK被抑制时的通路。目标2将研究中央ISR效应器ATF4在脊髓损伤中的作用。 相关的脑白质丢失。我们的初步数据显示，在脊髓损伤后或内质网应激的OPC中，ATF4被激活。 我们将确定ATF4是否是OL/OPC死亡、脑白质损伤和功能衰退的调节因子 在挫伤后。总而言之，目前的实验设计是基于我们以前的数据 脊髓损伤后ERSR的特征。在这里，我们建议描述ISR介导的细胞的新机制 脊髓损伤后死亡以及定义哪种ISR介体可能最适合于治疗转化为 急诊治疗脊髓损伤患者。这种治疗很可能适用于其他类型的中枢神经系统创伤，如 脑外伤和中风。

Abstract. We identified the ER stress response (ERSR) as a potential target for therapeutic interventions against white matter loss and locomotor impairment after spinal cord injury (SCI). Specifically, the signaling pathway that involves the ERSR kinase PERK, the PERK target elongation initiation factor 2α (eIF2α), and PERK-activated transcription factor CHOP may be manipulated in a time-dependent manner to promote SCI recovery. PERK signaling has a partial overlap with the integrated stress response (ISR) that, via several stress-activated kinases, leads to increased levels of phospho-eIF2α (peIF2α), transient inhibition of protein synthesis, and activation of the transcription factor ATF4. ATF4 regulates CHOP as well as genes involved in ROS metabolism, translational regulation and amino acid synthesis. In this way, the ISR attempts to restore homeostasis. Excessive and prolonged activation of the ISR results in anabolism-associated oxidative stress, mitochondrial damage, cell death and inflammation. Pro-ISR stimuli such as hypoxia, lack of nutrients, oxidative stress, and ER stress are present after SCI. However, the role of the principal ISR components – eIF2α kinases other than PERK and their common downstream target ATF4 – has not been addressed in the context of white matter loss after contusive SCI. Our overarching hypothesis is that the ISR plays a critical role in pathogenesis of contusive SCI by promoting OL/OPC death and white matter loss. Aim 1 will examine the role of the 4 upstream ISR kinases (PERK, PKR, GCN2, HRI, which are activated by different stressors) that phosphorylate eIF2α, which in turn inhibits global translation and enhances stress-induced gene expression. We will use a combination of previously optimized gain and loss of function in vitro OPC/OL and in vivo SCI assays that utilize pharmacological inhibitors as well as Hri-/-, Pkr-/-, and Gcn2-/-mice. Preliminary data from ER stressed OPCs or SCI tissue show activation of these kinases as well as compensatory activation of the ISR pathway when PERK is inhibited. Aim 2 will examine the role of the central ISR effector ATF4 in SCI- associated white matter loss. Our preliminary data show activation of ATF4 after SCI or in ER-stressed OPCs. We will determine whether ATF4 is a mediator of OL/OPC death, white matter damage, and functional decline after contusive SCI. In summary, current experimental design is based on data from our previous characterization of the ERSR after SCI. Here, we propose to delineate novel mechanisms of ISR-mediated cell death after SCI as well as define which of ISR mediators may best be suited for therapeutic translation to acutely treat SCI patients. Such treatments are likely to be applicable to other types of CNS trauma such as TBI and stroke.