利用基因敲除大鼠模型研究PON1对小胶质细胞吞噬的调节机制

Microglia play an important role in Aβ phagocytosis and clearance in AD. TREM2 functions as a key regulator of microglia phagocytosis that promotes Aβ clearance and reduces inflammation. The polymorphism of paraoxonase 1 (PON1) gene is a risk factor for AD, but the mechanism remains unclear. In our previous work, we found that PON1 knockout enhanced microglia phagocytosis with increased TREM2 protein level although no proportionate change was found in TREM2 mRNA transcription level. On the contrary, the administration of PON1 recombinant protein resulted in the decrease of phagocytosis with the decrease of TREM2 protein level. However, the effect of PON1 on microglia phagocytosis and the interaction with TREM2 have not been reported. We proposed the hypothesis that PON1 interacts with TREM2 and induces TREM2 degradation in lysosome that decreases microglia phagocytosis. PON1 knockout rats were used to achieve this goal, and three specific objectives of this study were set as follows: (1) the effect of PON1 on TREM2/DAP12 signaling pathway was clarified; (2) the protein interaction between PON1 and TREM2 was explored; (3) the role of PON1 in the internalization and lysosome degradation of TREM2 was studied. Finally, the role of PON1 in microglia phagocytosis was revealed. Once clarified, it will provide clues and theoretical basis for AD prevention. Establishment and application of PON1 knockout rats are also important for the creation of animal models.

小胶质细胞在AD中发挥吞噬和清除Aβ的重要作用。TREM2是调控小胶质细胞吞噬的关键节点蛋白，促进Aβ清除，减轻炎症。对氧磷酶PON1是AD的风险基因，其多态性与AD相关，但机制不明。前期发现，PON1敲除后小胶质细胞吞噬功能增强，伴随TREM2蛋白增多而转录不变；反之，PON1重组蛋白刺激导致吞噬功能降低，伴随TREM2蛋白减少。然而，PON1与TREM2互作及对小胶质细胞吞噬的作用机制，尚未见报道。由此假设：PON1与TREM2互作诱导TREM2降解，抑制小胶质细胞吞噬。本研究拟利用PON1基因敲除大鼠，①明确PON1对TREM2/DAP12信号通路的调节作用；②探索PON1与TREM2间的蛋白互作；③研究PON1对TREM2的内在化和溶酶体降解促进作用，揭示PON1对小胶质细胞吞噬的调节机制。一旦阐明，将对AD的防治提供线索和理论依据。敲除大鼠的建立和应用对于模型创制也有重要意义。

小胶质细胞在AD中发挥吞噬和清除Aβ的重要作用。TREM2是调控小胶质细胞吞噬的关键节点蛋白，促进Aβ清除，减轻炎症。对氧磷酶PON1是AD的风险基因，其多态性与AD相关，但机制不明。本项目揭示了PON1通过与TREM2互作对小胶质细胞吞噬调节机制：①明确PON1对TREM2/DAP12信号通路的调节作用；②确定了PON1与TREM2间的蛋白互作关系；③明确PON1促进TREM2的内在化和溶酶体降解；④明确了PON1基因敲除对于脑内小胶质细胞Aβ吞噬和清除的促进作用。这些结果为AD的防治提供线索和理论依据。PON1敲除大鼠的建立和应用对于模型创制也有重要意义。在项目执行期间，在行业杂志上发表了学术论文6篇，包含SCI论文4篇，北大核心论文1篇，综述1篇；获得授权专利2项。此外，还建立了新的动物模型，PON1，APOE4基因敲入大鼠，为未来的更进一步的研究工作奠定良好的基础。