Cell non-autonomous regulation of the unfolded protein response in aging

 描述（由申请人提供）：生活是紧张的。细胞反复暴露于破坏蛋白质稳态（蛋白质稳态）的各种应激源，导致蛋白质错误折叠和聚集。为了维持蛋白质稳态，细胞已经进化出针对抑制翻译、诱导伴侣蛋白表达和消除受损蛋白质的隔室特异性应激反应。内质网（ER）负责折叠人类总蛋白质组的近三分之一，包括几乎所有分泌的蛋白质。为了保护这一重要细胞器的功能，ER可以启动未折叠蛋白反应 （UPRER），以响应错误折叠蛋白质的存在。我们的实验室研究了UPRER在线虫C. elegans，并发现响应ER应激激活IRE-1/XBP-1通路的能力随着年龄的增长而消失。UPRER的这种减少减少了对ER应激诱导剂的保护。有趣的是，UPRE介导的对ER应激的保护作用的这种年龄依赖性下降可以通过神经系统中组成型活性XBP-1的表达来预防。最引人注目的是，在C. elegans导致远端细胞类型中UPRER的细胞非自主激活并延长寿命。最近报道，下丘脑神经元中XBP-1的过表达诱导肝脏中XBP-1的剪接，并保护小鼠免于饮食诱导的肥胖。因此，细胞非自主应激信号转导在C.线虫和啮齿动物，并调节关键的代谢功能。我们假设，神经元XBP-1 s诱导跨细胞信号传导机制，以协调整个生物体的应激反应，改善代谢状态，延长寿命。然而，这种信号传导机制所需的遗传成分是未知的。在目标1中提出的新型CRISPR-Cas9遗传筛选中，我们将鉴定XBP 1 s跨细胞应激反应的重要介质，这将为衰老和代谢疾病提供额外的、可能更特异的治疗靶点。此外，我们假设哺乳动物中神经元XBP 1 s的过表达将挽救UPRER的年龄起始损失并增加寿命。在目标2中，我们将使用在下丘脑神经元中过表达XBP 1 s的转基因小鼠来测试我们的假设。由于我们的医疗保健系统面临的最大挑战之一是与年龄相关的代谢和神经系统疾病日益增长的经济负担，因此阐明调节XBP 1 s诱导寿命的机制并确定XBP 1 s在哺乳动物中的作用具有至关重要的意义。研究这个建议中所描述的问题不仅对正常衰老，而且对老年性疾病都有巨大的治疗意义。

 DESCRIPTION (provided by applicant): Life is stressful. Cells are repeatedly exposed to various stressors that disrupt protein homeostasis (proteostasis), resulting in protein misfolding and aggregation. To maintain proteostasis, cells have evolved compartment-specific stress responses aimed at repressing translation, inducing chaperone expression, and eliminating damaged proteins. The endoplasmic reticulum (ER) is responsible for the folding of nearly one third of the total human proteome, including almost all of the proteins that are secreted. To protect the function of this essential organelle, the ER can initiate the unfolded protein response (UPRER) in response to the presence of misfolded proteins. Our laboratory examined the role of the UPRER in aging within the nematode C. elegans and found that the ability to activate the IRE-1/XBP-1 pathway in response to ER stress is abrogated with age. This reduction in UPRER diminishes protection against ER stress-inducing agents. Interestingly, this age-dependent decline in UPRER-mediated protection against ER stress can be prevented by the expression of constitutively active XBP- 1s in the nervous system. Most striking, neuronal expression of XBP-1s in C. elegans leads to cell non- autonomous activation of the UPRER in distal cell types and increases lifespan. It was recently reported that overexpression of XBP-1s in neurons in the hypothalamus induces XBP-1 splicing in the liver and protected mice from diet-induced obesity. Therefore, cell non-autonomous stress signaling is conserved between C. elegans and rodents and regulates key metabolic functions. We hypothesize that neuronal XBP-1s induces a trans-cellular signaling mechanism to coordinate an organism-wide stress response, an improved metabolic state, and a longer lifespan. However, the genetic components required for this signaling mechanism are unknown. In the novel CRISPR-Cas9 genetic screen proposed in aim 1, we will identify essential mediators of the XBP1s transcellular stress response that will provide additional, potentially more specific, therapeutic targets for aging and metabolic disease. Furthermore, we hypothesize that neuronal XBP1s overexpression in mammals will rescue the age-onset loss of UPRER and increase longevity. In Aim 2 we will test our hypothesis using transgenic mice that overexpress XBP1s in hypothalamic neurons. Since one of the greatest challenges facing our healthcare system is the growing economic burden of age-related metabolic and neurologic diseases, elucidating the mechanisms that regulate XBP1s-induced longevity and determining the role of XBP1s in mammals are of paramount significance. Answering the questions described in this proposal will have enormous therapeutic implications not only for normal aging, but also age-onset diseases.