Function of the TREM2 R47H variant associated with risk of Alzheimer's disease

描述（由申请人提供）：阿尔茨海默病（AD）是美国和全世界的一个主要临床问题。美国国家卫生统计中心最近的报告显示，美国约有540万人患有阿尔茨海默病，阿尔茨海默病是美国第六大死因。虽然在过去的几十年里，人们对阿尔茨海默病的发病机制已经有了很大的了解，但仍有许多未解决的问题，也没有有效的治疗方法。阿尔茨海默病遗传关联的鉴定使人们对疾病发展的机制有了更深入的了解。最近，两项研究独立地确定了TREM2基因的变异与晚发型阿尔茨海默病的风险增加有关。TREM2基因编码的细胞表面受体表达在一些髓细胞，包括小胶质细胞，巨噬细胞谱系的大脑细胞。小鼠系统研究表明，TREM2可以在小胶质细胞和巨噬细胞中发挥抑制炎症反应的作用，并促进凋亡神经元的吞噬。由于关于AD是否具有炎症成分的讨论很多，TREM2变体与AD的关联支持了小胶质细胞炎症反应增加可能促进AD发展的观点。主要的TREM2变异被确定为增加晚发性AD的风险，编码TREM2受体细胞外部分的单个氨基酸变化（R47H）。我们假设TREM2-H47变异导致大脑炎症增加，从而促进晚发性AD。我们的目的是验证TREM2-H47变体抑制炎症反应、促进吞噬和结合硫酸n -乙酰乳糖胺配体的能力降低的假设。我们将1)生成TREM2的人和小鼠无风险变体（TREM2- r47）和风险变体（TREM2- h47 *）的TREM2- fc融合蛋白，并使用表面等离子体共振和聚糖阵列确定结合动力学和特异性；2)在巨噬细胞和小胶质细胞中表达人和小鼠TREM2的无风险和风险变体，并比较它们抑制toll样受体诱导炎症的能力。3)在CHO细胞和dap12缺陷巨噬细胞中表达tre2的人和小鼠无风险和危险变异体，比较它们与凋亡细胞的结合和诱导吞噬能力。了解R47H变异如何影响TREM2功能将对小胶质细胞和炎症在AD发病机制中的作用产生重要的见解。此外，这些实验的结果将使我们更好地了解如何靶向TREM2治疗AD。因此，围绕TREM2参与AD发病机制的新发现，这是AD研究的一个高度优先的领域。

DESCRIPTION (provided by applicant): Alzheimer's disease (AD) is a major clinical problem in the United States and throughout the world. Recent reports from the National Center for Health Statistics state that approximately 5.4 million people have AD in the United States, where it is the 6th leading cause of death. While great strides have been made over the last decades in understanding the pathogenesis of AD, there are still many unresolved issues and no effective treatments. The identification of genetic associations with AD has led to a greater understanding of the mechanisms involved in disease development. Recently, two studies have independently identified variants in the TREM2 gene with increased risk of late onset Alzheimer's disease. The TREM2 gene encodes a cell- surface receptor expressed on some myeloid cells, including microglia, the macrophage-lineage cells of the brain. Studies in mouse systems have shown that TREM2 can function in microglia and macrophages to inhibit inflammatory responses as well as promote the phagocytosis of apoptotic neurons. As there has been much discussion of whether AD has an inflammatory component, the association of a TREM2 variant with AD supports the idea that increased inflammatory responses of microglia may promote AD development. The predominant TREM2 variant identified as increasing risk of late onset AD encodes a single amino acid change (R47H) in the extracellular portion of the TREM2 receptor. We hypothesize that the TREM2-H47 variant leads to increased inflammation in the brain that promotes late onset AD. Our aim is to test the hypothesis that the TREM2-H47 variant has a reduced ability to inhibit inflammatory responses, promote phagocytosis, and bind sulfated N-acetyllactosamine ligands. We will 1) generate TREM2-Fc fusion proteins of the human and mouse non-risk (TREM2-R47) and risk (TREM2-H47*) variant of TREM2 and determine binding kinetics and specificity using surface plasmon resonance and glycan arrays, 2) express the non-risk and risk variants of human and mouse TREM2 in macrophages and microglia, and compare their ability to inhibit Toll-like receptor induced inflammation, and 3) express the human and mouse non-risk and risk variants of TREM2 in CHO cells and in DAP12-deficient macrophages and compare their ability to bind to and induce phagocytosis of apoptotic cells. Understanding how the R47H variant affects TREM2 function will yield important insights into the role of microglia and inflammation in the pathogenesis of AD. Additionally, the results from these experiments will allow us to better understand how to therapeutically target TREM2 for AD treatment. Therefore this is a high priority area of research in AD centered around the novel finding that TREM2 participates in AD pathogenesis.