Parkinson's and Prokaryotes: roles of bacteria, gut permeability, innate immunity, and genetics in C. elegans dopaminergic neurodegeneration

摘要 帕金森病 (PD)，其特征是多巴胺能 (DA) 神经元通过𝛼-突触核蛋白 (𝛼S) 发生退化 美国每年花费 519 亿美元，预计到 2030 年将影响 120 万美国人。 目前的治疗只能提供有限的症状缓解，无法实现功能性治愈，这主要是由于 PD 启动的神秘本质。因此，对 PD 发病机制有更深入、机制的了解至关重要 以获得有效的治疗。一个新兴的假设是 PD 始于肠道，𝛼S 聚集体从肠道传播 肠道通过迷走神经等途径到达大脑。有趣的是，这些 𝛼S 聚集体是在肠道中检测到的 在 PD 诊断之前。此外，肠道通透性和功能障碍在帕金森病患者中也很常见。虽然这些 肠道病理可能导致肠道细菌和微生物相关分子模式的易位 （MAMP）进入宿主组织并随后通过先天免疫受体激活诱导炎症，这 没有被直接调查过。因此，肠道细菌和先天免疫受体在𝛼S聚集中的作用 PD 进展尚不清楚。此外，像小鼠这样的帕金森病哺乳动物模型在生物学上很复杂， 拥有多样化的肠道微生物群，并且无法进行公正的诱变筛选来识别新的 PD 因子。 因此，一个极简主义模型在遗传上是易于处理的，并且允许对宿主和宿主进行诱变筛选。 单个微生物将有助于识别对帕金森病发病机制至关重要的新宿主和细菌因素。 为此，我建议使用线虫秀丽隐杆线虫，一种广泛用于疾病治疗的模式生物 研究和 PD 研究，调查肠道细菌如何引发炎症反应，从而加剧炎症反应 DA神经变性。我将使用的特定模型在 DA 神经元中共同表达人类 𝛼S 和 GFP， 导致 DA 神经元逐渐丧失，如 GFP 信号丧失所示。我提议的研究将使用 CRISPR-Cas9 基因组编辑技术可灭活对肠道屏障完整性和先天免疫至关重要的基因 受体，然后通过监测荧光来研究这些基因在 PD 发病机制中的空间作用 标记的 𝛼S 和 GFP 标记的 DA 神经元。此外，细菌种类或特定的 MAMP 将被单独 分别给予秀丽隐杆线虫作为细菌食物来源或治疗方法，以确定哪些细菌特征 可能会增强或抑制 PD。最后，我将对秀丽隐杆线虫和个别细菌进行诱变筛选 草坪分别识别新的宿主和细菌因素，它们促进或抑制PD进展。 我提出的研究将有助于确定新的治疗靶点和治疗方法，以阻止或潜在逆转帕金森病， 使用线虫作为具有成本效益的筛选工具。该项目是高度跨学科的，结合了 免疫学、神经生物学、微生物学、肠道生物学和遗传学。该策略提高了可能性 确定影响 PD 发病机制的新因素和治疗方法。

Abstract Parkinson’s disease (PD), characterized by the degeneration of dopaminergic (DA) neurons via 𝛼-Synuclein (𝛼S) aggregation, costs $51.9 billion annually in the US and is predicted to affect 1.2 million Americans by 2030. Current treatments only provide limited and symptomatic relief, with no functional cure, largely due to the mysterious nature in which PD is initiated. Thus, a deeper, mechanistic understanding of PD pathogenesis is vital for effective treatment. An emerging hypothesis is that PD begins in the gut, where 𝛼S aggregates spread from the gut to the brain via routes like the vagus nerve. Interestingly, these 𝛼S aggregates are detected in the gut years before PD diagnosis. In addition, gut permeability and dysfunction are common in PD patients. Although these intestinal pathologies likely lead to in the translocation of gut bacteria and microbe-associated molecular patterns (MAMPs) into host tissues and subsequent induction of inflammation via innate immune receptor activation, this has not been directly investigated. Thus, the role of gut bacteria and innate immune receptors in 𝛼S aggregation and PD progression is unclear. Furthermore, mammalian models for PD like mice are biologically complex, harbor a diverse gut microbiota, and cannot undergo unbiased mutagenesis screens to identify novel PD factors. Thus, a minimalist model which is genetically tractable and permits mutagenesis screens for both the host and individual microbes would empower identification of novel host and bacterial factors crucial to PD pathogenesis. To this end, I propose to use the nematode Caenorhabditis elegans, a model organism widely used in disease study and PD research, to investigate how gut bacteria may trigger inflammatory responses that exacerbate DA neurodegeneration. The particular model that I will use co-expresses human 𝛼S and GFP in DA neurons, causing a progressive loss of DA neurons as indicated by GFP signal loss. My proposed studies will use the CRISPR-Cas9 genome editing technique to inactivate genes crucial for gut barrier integrity and innate immune receptors and then investigate the spatial role of these genes in PD pathogenesis by monitoring fluorescently- labeled 𝛼S and GFP-labeled DA neurons. Furthermore, bacterial species or specific MAMPs will be individually given to C. elegans as bacterial food sources or treatments, respectively, to identify what bacterial characteristics may enhance or suppress PD. Lastly, I will conduct mutagenesis screens on C. elegans and individual bacterial lawns to identify novel host and bacterial factors, respectively, which either promote or inhibit PD progression. My proposed study will help identify novel therapeutic targets and treatments to block or potentially reverse PD, using C. elegans as a cost-efficient screening tool. This project is highly interdisciplinary, combining immunology, neurobiology, microbiology, enteric biology, and genetics. This strategy improves the possibility of identifying novel factors and treatments which affect PD pathogenesis.