Background and Purpose- Ischemic stroke impairs endoplasmic reticulum (ER) function, causes ER stress, and activates the unfolded protein response. The unfolded protein response consists of 3 branches controlled by ER stress sensor proteins, which include PERK (protein kinase RNA-like ER kinase). Activated PERK phosphorylates eIF2α (eukaryotic initiation factor 2 alpha), resulting in inhibition of global protein synthesis. Here, we aimed to clarify the role of the PERK unfolded protein response branch in stroke. Methods- Neuron-specific and tamoxifen-inducible PERK conditional knockout (cKO) mice were generated by cross-breeding Camk2a-CreERT2 with Perkf/f mice. Transient middle cerebral artery occlusion was used to induce stroke. Short- and long-term stroke outcomes were evaluated. Protein synthesis in the brain was assessed using a surface-sensing-of-translation approach. Results- After tamoxifen-induced deletion of Perk in forebrain neurons was confirmed in PERK-cKO mice, PERK-cKO and control mice were subjected to transient middle cerebral artery occlusion and 3 days or 3 weeks recovery. PERK-cKO mice had larger infarcts and worse neurological outcomes compared with control mice, suggesting that PERK-induced eIF2α phosphorylation and subsequent suppression of translation protects neurons from ischemic stress. Indeed, better stroke outcomes were observed in PERK-cKO mice that received postischemic treatment with salubrinal, which can restore the ischemia-induced increase in phosphorylated eIF2α in these mice. Finally, our data showed that post-treatment with salubrinal improved functional recovery after stroke. Conclusions- Here, we presented the first evidence that postischemic suppression of translation induced by PERK activation promotes recovery of neurological function after stroke. This confirms and further extends our previous observations that recovery of ER function impaired by ischemic stress critically contributes to stroke outcome. Therefore, future research should include strategies to improve stroke outcome by targeting unfolded protein response branches to restore protein homeostasis in neurons.

中文翻译：

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展开的蛋白应答的PERK（蛋白激酶RNA样ER激酶）分支通过抑制蛋白合成赋予缺血性卒中神经保护作用。

背景与目的-缺血性中风损害内质网（ER）的功能，引起内质网应激，并激活未折叠的蛋白质反应。展开的蛋白应答由ER应力传感器蛋白控制的3个分支组成，其中包括PERK（类似于蛋白激酶RNA的ER激酶）。激活的PERK使eIF2α（真核起始因子2α）磷酸化，从而抑制了整体蛋白质合成。在这里，我们旨在阐明PERK展开的蛋白应答分支在中风中的作用。方法-通过将Camk2a-CreERT2与Perkf / f小鼠杂交获得神经元特异性和他莫昔芬诱导的PERK条件性基因敲除（cKO）小鼠。使用短暂的大脑中动脉闭塞诱发中风。评价了短期和长期的卒中结果。使用表面感测翻译方法评估大脑中的蛋白质合成。结果-在PERK-cKO小鼠中证实了他莫昔芬诱导的前脑神经元Perk缺失后，对PERK-cKO和对照组小鼠进行短暂的大脑中动脉闭塞，并恢复3天或3周。与对照小鼠相比，PERK-cKO小鼠具有更大的梗塞和较差的神经系统结果，表明PERK诱导的eIF2α磷酸化和随后的翻译抑制可保护神经元免于缺血性应激。确实，在接受salubrinal缺血后治疗的PERK-cKO小鼠中观察到了较好的中风转归，可以恢复这些小鼠的缺血诱导的磷酸化eIF2α增加。最后，我们的数据表明，用金枪鱼进行后处理可改善卒中后的功能恢复。结论-在这里，我们提出了第一个证据，即缺血性抑制PERK激活诱导的翻译促进中风后神经功能的恢复。这证实并进一步扩展了我们以前的观察结果，即缺血性应激损害的ER功能恢复对卒中结局至关重要。因此，未来的研究应包括通过针对未折叠的蛋白质反应分支来恢复神经元蛋白质稳态来改善卒中预后的策略。