Defining the role of SINE retrotransposons and inflammasome activation in Alzheimer's disease

项目摘要 阿尔茨海默病（AD）的病理学标志包括淀粉样蛋白-β（Aβ）斑块的沉积和 过度磷酸化的Tau聚集体在神经元缠结中的积累。这些聚合物已经 证实激活炎性体信号传导。炎性小体是先天免疫平台， 许多慢性神经退行性和炎症性疾病，如AD。炎性小体抑制正在被 探索作为AD和其他复杂神经炎症/退行性疾病的治疗策略，包括 帕金森病、多发性硬化症和年龄相关性黄斑变性（AMD）。最近的研究 确定了转座因子（TE）失调与AD之间的联系。我们已经建立了一个关键的 一类TE-短散在元件（西内斯）-的活性在发病机制中的机械作用 AMD.我们已经证明，SINE RNA的积累诱导细胞变性AMD的双重作用， NLRP 3和NLRC 4炎性体的活化。此外，我们已经鉴定了DDX 17，一种RNA解旋酶， 作为SINE RNA的分子传感器，允许炎性小体的双重激活。而且我们 初步研究已经确定了5xFAD中与Aβ沉积物空间接近的SINE RNA的失调 AD模型和NLRC 4-NLRP 3信号传导的新型小分子抑制剂抑制炎性小体 Aβ聚集体诱导的活化。 尽管有这些发现，关于AD中SINE RNA和炎性小体的知识仍然存在重大差距， 例如，AD中SINE RNA的细胞来源是不确定的， AD中的炎性小体组分是未知的。该提案将检验AD病理学是 通过内源性SINE RNA积累诱导的NLRP 3/NLRC 4活化而加剧。我们将测试这个 通过三个特定的目的进行假设：1）我们将定量SINE RNA表达和炎性小体活化， 在AD的5xFAD模型中绘制它们的细胞起源; 2）我们将确定SINE RNA的细胞机制- 在脑小胶质细胞中诱导炎性小体活化，SINE RNA是否通过 小胶质细胞，以及炎性小体抑制剂是否改善Aβ吞噬作用;以及3）我们将测试 单个和双重炎性体抑制剂对Aβ清除以及认知和行为缺陷的影响 5xFAD型号。总的来说，这些主题相关但独立的目标将揭示以下方面的贡献： AD中SINE RNA诱导的炎性小体活化。本项目响应RFA-AG-22-021，因为它将（a） 定义SINE RNA和神经炎症之间的功能作用和因果关系;（B）定义SINE RNA和神经炎症之间的功能作用和因果关系; 支持对SINE RNA的先天和免疫应答的机制;以及（c）测试治疗干预 干扰SINE RNA介导的分子途径。这些研究将提供更深层次的机制 了解TE的作用，可以作为未来翻译研究的基础。

PROJECT SUMMARY Pathological hallmarks of Alzheimer's disease (AD) include deposition of Amyloid-β (Aβ) plaques and accumulation of hyperphosphorylated Tau aggregates in neurofibrillary tangles. These aggregates have been demonstrated to activate inflammasome signaling. Inflammasomes are innate immune platforms implicated in numerous chronic neurodegenerative and inflammatory conditions such as AD. Inflammasome inhibition is being explored as a therapeutic strategy for AD and other complex neuroinflammatory/degenerative disorders including Parkinson's disease, multiple sclerosis, and age-related macular degeneration (AMD). Recent studies have identified links between dysregulation of transposable elements (TEs) and AD. We have established a critical mechanistic role for activity of one class of TEs – short interspersed elements (SINEs) – in the pathogenesis of AMD. We have demonstrated that SINE RNA accumulation induces cellular degeneration in AMD by dual activation of the NLRP3 and NLRC4 inflammasomes. Furthermore, we have identified DDX17, an RNA helicase, as the molecular sensor of SINE RNAs that licenses dual activation of the inflammasomes. Moreover, our preliminary studies have identified dysregulation of SINE RNAs in spatial proximity to Aβ deposits in the 5xFAD model of AD and that a novel small molecule inhibitor of NLRC4-NLRP3 signaling suppresses inflammasome activation induced by Aβ aggregates. Notwithstanding these findings, major gaps in knowledge about SINE RNAs and inflammasomes in AD persist, e.g, the cellular sources of SINE RNAs in AD are undefined and whether SINE RNAs interact with and activate inflammasome components in AD is unknown. This proposal will test the hypothesis that AD pathology is exacerbated by NLRP3/NLRC4 activation induced by endogenous SINE RNA accumulation. We will test this hypothesis via three specific aims: 1) We will quantitate SINE RNA expression and inflammasome activation and map their cellular origins in the 5xFAD model of AD; 2) We will determine the cellular mechanisms of SINE RNA- induced inflammasome activation in brain microglia, whether SINE RNA compromises Aβ phagocytosis by microglia, and whether inflammasome inhibitors improve Aβ phagocytosis; and 3) We will test the effects of individual and dual inflammasome inhibitors on Aβ clearance as well as cognitive and behavioral deficits in the 5xFAD model. Collectively, these thematically related but independent aims will shed light on the contribution of SINE RNAs-induced inflammasome activation in AD. This project is responsive to RFA-AG-22-021 as it will (a) define the functional roles and causal relationships between SINE RNAs and neuroinflammation; (b) define the mechanisms underpinning innate and immune responses to SINE RNAs; and (c) test therapeutic interventions interfering with SINE RNA-mediated molecular pathways. These studies will provide a deeper mechanistic understanding of the role of TEs that can serve as a foundation for future translational research.