Interrogating and Targeting Microglia Phagocytosis in Alzheimer’s Disease

阿尔茨海默病（AD）是一种顽固性神经退行性疾病，在全国范围内摧毁了大约620万美国人。新出现的证据表明，小胶质细胞在阿尔茨海默病的发病机制中起着核心作用，并揭示了这些细胞的转录和表观遗传水平变化与疾病进展密切相关。因此，用选择性药物靶向小胶质细胞来控制其细胞活性是一种强有力的治疗途径。然而，精确的小胶质细胞靶向需要对细胞表面蛋白质组或表面组如何在疾病环境中重塑有广泛的了解，而这一生物学尚未得到系统的探索。我对暴露于Aβ原纤维后的小胶质细胞进行了质谱分析。我的数据显示，硫酸肝素蛋白聚糖和促进吞噬的蛋白质有明显的上调。在本提案的Aim 1中，我将直接测试a β诱导的硫酸肝素蛋白多糖是否导致人iPSC小胶质细胞中tau吞噬和播种增加。这一假设代表了一个独特的框架，通过小胶质细胞吞噬机制将a β和tau病理联系起来。在Aim 2中，我将确定硫酸肝素蛋白多糖在人AD大脑中的组织表达模式。最后，在Aim 3中，我将设计新的细胞表面降解抗体，称为KineTACs，从细胞表面特异性地降解疾病相关的小胶质细胞靶标。本提案中概述的工作具有创新性，将大大增加我们对阿尔茨海默病小胶质细胞吞噬的理解，并提供新的重组工具来调节这一过程。在我在加州大学旧金山分校的科学导师和指导老师的大力支持下，这次K08培训计划将使我在iPSC细胞培养模型、人体免疫组织化学和重组抗体工程方面培养掌握。这个轨迹构成了迈向更广泛的职业目标的第一步，即成为一名独立的内科科学家，研究神经变性的细胞和分子机制。

Alzheimer's disease (AD) is an intractable neurodegenerative disorder that devastates approximately 6.2 million Americans nationwide. Emerging evidence now establishes a central role for microglia in AD pathogenesis and reveals that transcriptional and epigenetic level changes in these cells tightly correlate with disease progression. Thus, targeting microglia with selective pharmacologic agents to control their cellular activity represents a powerful therapeutic avenue. However, precise microglia targeting requires broad knowledge of how the cell-surface proteome, or surfaceome, remodels in the disease environment, and this biology has not been systematically explored. I performed mass spectrometry-based surfaceome profiling of microglia after exposure to Aβ fibrils. My data revealed a robust upregulation of heparan sulfate proteoglycans and proteins that promote phagocytosis. In Aim 1 of this proposal, I will directly test if Aβ-induced heparan sulfate proteoglycans result in increased tau phagocytosis and seeding in human iPSC microglia. This hypothesis represents a unique framework that mechanistically links Aβ and tau pathology through microglia phagocytosis. In Aim 2, I will determine the tissue expression patterns of heparan sulfate proteoglycan in human AD brain. Finally, in Aim 3, I will engineer novel cell-surface degrading antibodies, called KineTACs, to specifically degrade disease-associated microglia targets from the cell-surface. The work outlined within this proposal is innovative and will greatly increase our understanding of microglia phagocytosis in AD and provide new recombinant tools to modulate this process. With the strong support of my scientific mentors and advisors at the University of California San Francisco, this K08 training proposal will enable me to cultivate mastery in iPSC cell culture models, human immunohistochemistry, and recombinant antibody engineering. This trajectory constitutes the first steps toward a broader career goal of becoming an independent physician-scientist studying the cellular and molecular mechanisms of neurodegeneration.