The Unfolded Protein Response and Neuroprotection in Stroke

摘要 缺血性中风是一种破坏性的医学状况，除了 仅适用于一小部分中风患者的溶栓疗法。为了改善中风的结局，新的 必须考虑药理学方法，例如促进内源性促进生存的途径。这里, 未折叠蛋白反应(UPR)是一个很有前途的靶点，因为UPR可以恢复内质网 (Er)功能，这对应激细胞的生存至关重要。内质网在折叠和折叠过程中起着关键作用 处理新合成的蛋白质。内质网功能在各种应激条件下受损，包括 中风，导致未折叠/错误折叠的蛋白质在内质网中积累，这种情况称为内质网应激。至 解决内质网应激，UPR激活由内质网中3个应激传感器介导的适应性反应 膜激活转录因子-6(ATF6)、肌醇需要酶-1(IRE1)和蛋白激酶 核糖核酸样ER激酶(PERK)。这些UPR分支有3个主要功能：1)增加蛋白质折叠 容量，2)减少内质网负荷，以及3)从内质网中消除积累的未折叠/错误折叠的蛋白质。这个 Upr还调节其他促生存途径，包括O-连接的β-N-乙酰氨基葡萄糖(O-GlcNAc) 修改。虽然我们知道中风会损害ER功能并激活UPR，但我们还不知道 单个UPR分支如何定义卒中缺血后神经元的命运和功能，或者 一个或多个UPR分支在卒中预后中起主导作用。这方面的知识对于 开发一种新的策略来利用UPR有利于生存的通路来获得中风的治疗益处。我们的长- 学期目标是为中风的治疗目的开发促进UPR促进生存的途径的策略。这个 这项应用的目的是建立UPR和卒中结果之间的机制联系，并 确定对中风后神经功能恢复起关键作用的一个或多个UPR分支。我们的 中心假说是促进有利于生存的UPR和相关通路促进受损内质网的恢复 缺血后神经元的功能和细胞内稳态，从而改善中风预后。基于我们的 新的独特的UPR选择性和神经元特异性转基因小鼠模型，假设将是 测试的具体目标如下：1)确定ATF6激活在中风预后中的作用；2)确定 IRE1/XBP1/O-GlcNAc轴对卒中结局的贡献；3)确定PERK分支的作用 在脑缺血后蛋白质合成和卒中预后方面。这项拟议的研究意义重大，因为我们 期望发现将UPR和下游通路与卒中结局联系起来的机制。是这样的 知识将成为未来研究的关键平台，旨在建立新的和创新的方法 改善中风后神经功能的恢复，这对中风患者的生活质量起着至关重要的作用。

Abstract Ischemic stroke is a devastating medical condition for which no pharmacologic intervention is available, except thrombolysis that can be used only for a small percentage of stroke patients. To improve stroke outcome, new pharmacologic approaches must be considered, such as boosting endogenous pro-survival pathways. Here, the unfolded protein response (UPR) is a promising target, because the UPR restores endoplasmic reticulum (ER) function, which is critical for survival of stressed cells. The ER plays a pivotal role in folding and processing newly synthesized proteins. ER function is impaired in a variety of stress conditions, including stroke, which results in accumulation of unfolded/misfolded proteins in the ER, a condition called ER stress. To resolve ER stress, the UPR activates adaptive responses that are mediated by 3 stress sensors in the ER membrane – activating transcription factor-6 (ATF6), inositol-requiring enzyme-1 (IRE1), and protein kinase RNA-like ER kinase (PERK). These UPR branches have 3 primary functions: 1) increase protein-folding capacity, 2) decrease the ER load, and 3) eliminate accumulated unfolded/misfolded proteins from the ER. The UPR also modulates other pro-survival pathways including O-linked β-N-acetylglucosamine (O-GlcNAc) modification. Although we know that stroke impairs ER function and activates the UPR, we do not yet know how the individual UPR branches define the fate and function of post-ischemic neurons in stroke, nor which UPR branch or branches play a predominant role in stroke outcome. Such knowledge is essential to developing a novel strategy to harness UPR pro-survival pathways for therapeutic benefits in stroke. Our long- term goal is to develop strategies to boost UPR pro-survival pathways for therapeutic purposes in stroke. The objective of this application is to establish the mechanistic link between the UPR and stroke outcome, and to identify the UPR branch or branches that critically define recovery of neurologic function after stroke. Our central hypothesis is that boosting pro-survival UPR and related pathways facilitates restoration of impaired ER function and cellular homeostasis in post-ischemic neurons, thereby improving stroke outcome. Based on our new unique UPR-selective and neuron-specific genetically modified mouse models, the hypothesis will be tested in the following specific aims: 1) Determine the role of ATF6 activation in stroke outcome; 2) Determine the contribution of the IRE1/XBP1/O-GlcNAc axis to stroke outcome; 3) Determine the role of the PERK branch in post-ischemic protein synthesis and stroke outcome. The proposed research is significant because we expect to uncover the mechanisms that link the UPR and downstream pathways to stroke outcome. Such knowledge will be a pivotal platform for future studies aimed at establishing new and innovative approaches to improve recovery of neurologic function after stroke, which critically defines quality of life for stroke patients.