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

项目总结 亨廷顿病(HD)是一种由亨廷顿蛋白(HTT)CAG扩张引起的致命性神经退行性疾病 突变(编码聚谷氨酰胺，mHTT)。MHTT是一种普遍表达的基因，但它显著损害 纹状体和皮质，随着疾病的发展，随之而来的是广泛的周围缺陷。以前的工作有 先天性和获得性炎症反应在HD中联系在一起。小胶质细胞，一种炎症的细胞指标，也是 HD动物模型和细胞培养模型及HD患者的纹状体表达增加。提高了反应性水平 单核细胞，炎性细胞因子，趋化因子，以及N-犬尿氨酸/色氨酸比率，一个指标 持续性炎症，已在出现症状前的HD患者中观察到，并与HD的进展相关。 此外，从人类HD患者和HD猴子模型获得的组织的rna-seq分析揭示了 广泛的转录失调与致炎途径激活相关。炎症也是 自噬与自噬密切相关，自噬是一种在HD中调节失调的分解代谢过程。尽管有这些研究，但 减轻炎症反应的机制或治疗目标尚不清楚。为了填满这个 知识缺口，这一建议检验了环状GMP-AMP合成酶(CGAS)-刺激物 干扰素基因(STING)是先天性免疫反应的主要途径，是HD的疾病修饰物 发病机制。这一假说是基于我们最近的发现提出的，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外显子1高核糖体占有率和cGAS依赖的炎症转录 因子(IRF3、IRF7)和炎性趋化因子(CCL5、CxCl10)在HD中表达上调。CGAS的耗竭 减少下游效应器的激活，并抑制HD细胞的自噬通量。后者是 与cGAS-STING通路在自噬诱导中的原始功能一致。这些数据强调了 CGAS-STING信号在HD发病机制中的重要作用随后，一个 独立研究证实，在HD模型中cGAS-STING被激活。然而，目前尚不清楚cGAS是否- STING通路是HD发生的被动或主动贡献者。在目标1中，我们将确定是否 CGAS基因缺失改变了HD Ki(Z175HD)小鼠的行为和病理特征。我们会 测定cGAS-/-；HD Ki小鼠的增龄相关行为改变和病理改变。在目标2中，我们将 确定小分子刺痛抑制剂是否降低HD Ki小鼠的HD表型。我们会请客的 Z175HD小鼠使用小分子刺痛抑制剂H-151并测定HD样缺陷的变化 与z175HD处理的车辆进行比较。拟议的实验将阐明cGAS-STING途径的作用 作为HD的抗炎治疗药物。

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.