Validating cGAS-STING pathway as drug target in Huntington disease mouse model

项目摘要 亨廷顿病（Huntington disease，HD）是由亨廷顿蛋白（huntingtin，HTT）CAG扩增引起的一种致死性神经退行性疾病 突变（编码多聚谷氨酰胺，mHTT）。mHTT是一种普遍表达的基因，但它显著损害 纹状体和皮质，随着疾病的进展，随之而来的是广泛的外周缺陷。以前的作品有 先天性和适应性炎症反应相关。小胶质细胞是炎症的细胞指标， 在HD动物和细胞培养模型以及HD患者的纹状体中增加。反应水平增加 单核细胞，炎性细胞因子，趋化因子和n-犬尿氨酸/色氨酸比率， 持续性炎症，均在表现前HD患者中观察到，并与HD进展相关。 此外，从人HD患者和HD猴模型获得的组织的RNA-seq分析揭示了 与促炎通路激活相关的广泛转录失调。炎症也是 与自噬密切相关，自噬是HD中失调的分解代谢过程。尽管有这些研究， 减少炎症反应的机制或治疗靶点仍然不太清楚。填补这一 知识差距，这项建议测试的假设，环GMP-AMP合酶（cGAS）-刺激剂的 干扰素基因（STING）是一种主要的先天免疫反应途径，是HD的疾病修饰因子 发病机制这一假设是基于我们最近的发现，即cGAS-STING途径是 在HD患者的组织和细胞模型中上调，并介导自噬和炎症反应。我们 发现cGAS mRNA和cGAS依赖性炎症转录的外显子1中存在高核糖体占据率 因子（Irf 3、Irf 7）和炎症趋化因子（Ccl 5和Cxcl 10）在HD中上调。cGAS消耗 减少下游效应STING活化，并且还抑制HD细胞中的自噬通量。后者是 这与cGAS-STING途径在自噬诱导中的原始功能一致。这些数据表明， cGAS-STING信号在HD病理机制中的重要作用。随后拟订一项 独立研究证实了cGAS-STING在HD模型中的活化。目前尚不清楚cGAS是否... STING途径是HD发展的被动或主动贡献者。在目标1中，我们将确定 cGAS的遗传缺失改变了HD KI（z175 HD）小鼠的行为和病理学特征。我们将 确定cGAS-/-;HD KI小鼠中年龄相关的行为改变和病理学变化。在目标2中，我们 确定小分子STING抑制剂是否减少HD KI小鼠中的HD表型。本公司对待 用小分子STING抑制剂H-151处理z175 HD小鼠，并确定HD样缺陷的变化 比较媒介物处理的z175 HD。拟议的实验将阐明cGAS-STING途径的作用， 作为HD的抗炎治疗剂。

Project summary Huntington disease (HD) is a fatal neurodegenerative disorder caused by the huntingtin (HTT) CAG expansion mutation (coding for polyglutamine, mHTT). mHTT is a ubiquitously expressed gene, yet it prominently damages the striatum and cortex, followed by widespread peripheral defects as the disease progresses. Prior works have linked innate and adaptive inflammatory responses in HD. Microglia, a cellular indicator of inflammation, is also increased in the striatum of HD animal and cell culture models and HD patients. Increased levels of reactive monocytes, inflammatory cytokines, chemokines, and the n-kynurenine/tryptophan ratio, an indicator of persistent inflammation, have all been observed in pre-manifest HD patients and correlated with HD progression. Furthermore, RNA-seq analysis of tissue obtained from human HD patients and HD monkey models reveals extensive transcriptional dysregulation associated with proinflammatory pathway activation. Inflammation is also closely linked to autophagy, a catabolic process that is dysregulated in HD. Despite these studies, the mechanisms or treatment targets for the reduction of inflammatory responses remain less clear. To fill this knowledge gap, this proposal tests the hypothesis that cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING), a major innate immunity response pathway, is a disease modifier in HD pathogenesis. This hypothesis was formulated based on our recent finding that the cGAS-STING pathway is upregulated in HD patients’ tissue and cell models and mediates autophagy and inflammatory responses. We found high ribosome occupancy in exon 1 of cGAS mRNA and cGAS-dependent inflammatory transcription factors (Irf3, Irf7), and inflammatory chemokine (Ccl5, and Cxcl10) are upregulated in HD. Depletion of cGAS diminishes downstream effector STING activation and also inhibits autophagy flux in HD cells. The latter is consistent with the primordial function of the cGAS-STING pathway in autophagy induction. These data underline an important role of cGAS-STING signaling in the pathological mechanisms of HD. Subsequently, an independent study confirmed activation of cGAS-STING in HD models. Yet, it is unclear whether the cGAS- STING pathway is a passive or active contributor to HD development. In Aim 1, we will determine whether the genetic deletion of cGAS alters the behavioral and pathological hallmarks of HD KI (z175HD) mice. We will determine age-related behavioral alterations and pathological changes in cGAS–/–;HD KI mice. In Aim 2, we will determine whether the small molecule STING inhibitor diminishes the HD phenotype in HD KI mice. We will treat z175HD mice with the small molecule STING inhibitor, H-151 and determine changes in the HD-like deficits compared vehicle treated z175HD. The proposed experiments will clarify the role of the cGAS–STING pathway as anti-inflammatory therapeutic agents in HD.