活化小胶质细胞在病灶旁聚集是多种慢性CNS病变的特征，深入研究对阐明相关的病理机制意义重大。ATP是触发小胶质细胞迁移的关键分子，而外核苷酸酶水解ATP生成腺苷，是调控ATP浓度的重要因素。已知ATP介导的P2受体通路是诱导小胶质细胞向病损迁移的关键通路，新近研究却发现脂多糖活化的小胶质细胞能通过腺苷依赖的P1受体通路而逆转对ATP的趋向性，但调控机制未明。我们发现脂多糖活化小胶质细胞明显上调一种新型外核苷酸酶PAP，后者可能通过促进ATP水解生成腺苷，激活P1通路来改变细胞对ATP的趋向性。在此基础上，本项目将应用实时共聚焦和双光子显微成像、结合RNAi、基因敲除和药理阻断等技术，从细胞、活脑组织切片和整体动物三个方面系统探讨PAP对小胶质细胞迁移的调控。本项目以外核苷酸酶为切入点研究活化小胶质细胞迁移，将为小胶质细胞迁移的分子调控提供新思路，为阐明相关疾病的病理机制提供理论依据。

A hallmark of chronic CNS inflammation is the clustering of activated microglial cells at the disease sites,where they contribute to the pathogenesis of multiple neurodegenerative disorders including Alzheimer's and Parkinson diseases. ATP plays a pivotal role in triggering microglial migration towards the sites of diesease/injury. Ectonuleotidases,by hydrolyzing ATP to adenosine, are important factors that control the quantity of extracellular ATP. It is well-known that ATP-mediated P2 receptor signaling is key to the chemoattractive migration of microglia. Intriguingly,recent studies have shown that the pro-inflammatory liposaccride(LPS)-activated microglia showed repulsive migration in response to ATP, through the adenosine-P1 receptor signaling. Yet, the underlying regulatory mechanism remains unknown. We have found that prostate acid phosphatase (PAP), a novel type of ectonucleotidases, is robustly upregulated in LPS-activated microglia, suggesting that upregulated PAP may drive an enhanced adenosine-P1 receptor signaling, resulting in the chemotactic reversal of activated microglia. Based on these findings, this grant proposal will use real-time confocal and two-photon microscopy imaging, in combination with RNAi, knockout and pharmaceutical techniques, to further examine the role of PAP ectonucleotidase in the chemotactic switch of activated microglia, at cellular, organotypic and whole-animal levels. A migratory study of activated microglia from the perspective of ectonucleotidase not only provides new insights into the mechanisms underlying the migratory features of microglia, but also helps to elucidate the pathogenesis of CNS disorders in which the migration of activated microglia is involved.