A Role of Astrocyte and Microglia Interplay in Alzheimer's Disease

项目摘要 阿尔茨海默病（AD）是最常见的神经退行性疾病，影响超过300万美国人 每年，并具有β-淀粉样蛋白的细胞外积累，细胞内tau聚集和异常神经胶质细胞 病理神经胶质功能障碍可引发兴奋性毒性和神经炎症，这总是与AD相关 发病机制反应性星形胶质细胞和小胶质细胞在AD发病机制中的触发因素尚不清楚。 以前，我确定了一种新的ER组分，membralin（TMEM 259），作为一种重要的疾病修饰剂， AD和肌萎缩侧索硬化症（ALS）的发病机制。膜蛋白可调节细胞的完整性和活性 γ-分泌酶复合物，并下调AD小鼠模型（TgCRND 8）中的membralin表达， 加重Aβ病理和记忆障碍。最近，我发现了一种非细胞自主的 Membralin介导的星形胶质细胞谷氨酸清除机制 转运蛋白EAAT 2通过AAV病毒注射提高膜蛋白可显著增加EAAT 2水平 并延长SOD 1G 93 A ALS小鼠的寿命。有趣的是，星形胶质细胞特异性膜蛋白缺失可以 表现出严重的神经炎性病理后果，如神经胶质细胞的强烈升高所证明的。 标记物包括GFAP（星形胶质细胞）、IBA 1和CD 68（小胶质细胞）。星形胶质细胞的转录组学分析 条件性基因敲除动物证实了与神经胶质增生、神经炎症和 异常的免疫反应AD脑和ALS脊髓中的膜蛋白水平均降低。兴奋性毒性， EAAT 2功能障碍和胶质增生是AD和ALS的共同病理特征。此外，最近的一个基因组- 广泛关联（GWAS）研究表明，membralin基因位点（也称为C19 ORF 6， 人类）位于与以下紧密相关的单核苷酸多态性（SNP，rs 117481827）的500 bp内 晚发性AD和膜蛋白转录物的剪接已被报道在AD中显著改变。所以我 假设星形胶质细胞膜蛋白途径上调可以减弱谷氨酸兴奋性毒性， 调节AD中的小胶质细胞依赖性致病作用。 在本研究的K99阶段，我将描述膜蛋白相关的分子机制。 星形胶质细胞功能和解剖反应性星形胶质细胞的分子触发机制（目的1）。我会决定 调节星形胶质细胞膜神经炎症通路是否可以改变AD的致病作用 小鼠模型（Aim 2）。在本研究的R 00阶段，我将研究一种膜蛋白依赖的 小胶质细胞中星形胶质细胞TREM 2依赖性DAM开关（Aim 3）。拟议的研究描述了神经胶质增生 诱导机制，将提供深入了解神经保护膜蛋白相关的星形胶质细胞途径 其可以通过细胞自主和非细胞性 自主机制。在完成这项研究的目的，我们可以定义新的治疗靶向 通过调节AD中神经胶质功能的策略。

PROJECT SUMMARY Alzheimer's disease (AD) is the most common neurodegenerative disease affecting over 3 million Americans yearly, and features the extracellular accumulation of β-amyloid, intracellular tau aggregates, and aberrant glial pathology. Glial dysfunction can trigger excitotoxicity and neuroinflammation, which is invariably linked to AD pathogenesis. Reactive astrocyte and microglia triggers in AD pathogenesis are not yet clear. Previously, I identified a novel ER component, membralin (TMEM259), as an important disease modifier in the pathogenesis of AD and Amyotrophic Lateral Sclerosis (ALS). Membralin can modulate the integrity and activity of the γ-secretase complex, and downregulating membralin expression in a mouse model of AD (TgCRND8) can exacerbate Aβ pathology and memory impairment. More recently, I have identified a non-cell autonomous glutamate clearance mechanism in astrocytes mediated by membralin through regulation of the glutamate transporter, EAAT2. Elevation of membralin through AAV virus injection can significantly increase EAAT2 levels and extend the lifespan of the SOD1G93A ALS mice. Interestingly, astrocyte-specific membralin deletion can manifest severe neuroinflammatory pathological consequences, as demonstrated by robust elevation of gliotic markers including GFAP (astrocytes), IBA1 and CD68 (microglia). Transcriptomic analysis of astrocyte conditional knockout animals confirms the upregulation of genes associated with gliosis, neuroinflammation and abnormal immune response. Membralin levels are reduced in both AD brain and ALS spinal cord. Excitotoxicity, EAAT2 dysfunction and gliosis are common pathological features in AD and ALS. Moreover, a recent genome- wide association (GWAS) study demonstrated that the membralin gene locus (also known as C19ORF6 in human) is located within 500 bp of a single nucleotide polymorphism (SNP, rs117481827) tightly associated with late-onset AD, and splicing of membralin transcripts has been reported to be significantly altered in AD. Thus, I hypothesize that upregulation of astrocytic membralin pathways can attenuate glutamate excitotoxicity and modulate microglial-dependent pathogenic effects in AD. In the K99 phase of this study, I will characterize molecular mechanisms underlying membralin-associated astrocyte function and dissect molecular triggering mechanisms in reactive astrocytes (Aim 1). I will determine whether modulation of astrocytic membralin neuroinflammatory pathways can alter pathogenic effects in an AD mouse model (Aim 2). In the R00 phase of this study, I will investigate modulation of a membralin-dependent astrocytic TREM2-dependent DAM switch in microglia (Aim 3). The proposed study characterizing the gliosis induction mechanisms in AD, will provide insight into neuroprotective membralin-associated astrocyte pathways that can limit glutamatergic excitotoxicity and neuroinflammation through cell-autonomous and non-cell autonomous mechanisms. In completing the aims of this study, we may define new therapeutic targeting strategies through modulation of glial function in AD.