细胞质DNA免疫识别通路的分子机制研究

The appearance of DNA in the cytoplasm is a very dangerous signal to cells. This could be caused by viral or bacterial infection, or as a result of cellular damage that leaks host DNA into the cytoplasm. Cytosolic DNA activates the host immune response, which is critically dependent on the newly identified cGAS- STING-TBK1-IRF3 pathway. The activation of this pathway has been known to play important roles in anti-viral infections and inhibition of tumor cell proliferation. While a robust DNA sensing pathway is essential for eliminating microbial infection, this response must be well controlled to prevent excessive production of inflammatory cytokines, which will cause dangerous auto-immune diseases. The previous structural immunology studies have contributed to our understanding of mechanisms of DNA recognition, second messenger 2'3'-cGAMP generation, as well as the STING activation. While the molecular mechanism and structural basis of the downstream signaling transduction from STING to TBK1 and IRF3 is still largely unknown. Till now, there has been no successful drugs designed for targeting this pathway, which represents a critical needs for the development of specific small molecule agonist and antagonists for treating infection, cancer, and auto-immune diseases. Based on our previous study and preliminary data, a research program that combines approaches of structural, biochemical, cellular biology will be assembled to decipher the molecular mechanisms at play, and to harness this knowledge for the generation of drugs to enhance or repress human immune activity.

宿主细胞的胞质中出现DNA，往往是由于病原微生物的侵染或宿主细胞的损伤所导致的。细胞质DNA将激活宿主的重要固有免疫信号通路：cGAS-STING-TBK1-IRF3。该通路的激活除了帮助宿主抵御病原微生物的感染，还有着明确的抗肿瘤作用。而另一方面，此通路的过度活化则会导致危险的自身免疫疾病。之前关于此通路的结构免疫学研究主要集中在上游部分，即cGAS识别DNA并激活STING的分子机制。而STING招募TBK1并活化IRF3的下游分子机制及其结构基础是领域内亟待解决的科学问题。在应用方面，目前还没有任何针对此通路的有效靶向药物，因此设计有效的小分子抑制剂或激活剂将为传染病、癌症、及自身免疫疾病的治疗提供帮助。申请人在前期大量相关工作的基础上，拟结合结构生物学、生物化学、细胞生物学等多种手段研究此通路中还未解决的基本生物学问题；并结合高通量筛选及结构辅助，设计针对此通路的小分子先导化合物。

细胞质DNA可激活宿主的重要固有免疫信号通路:cGAS-STING通路。该通路的激活除了帮助宿主抵御病原微生物的感染，还有着明确的抗肿瘤作用；而另一方面，此通路的过度活化则会导致危险的自身免疫疾病。基于前期研究基础，本项目拟结合结构生物学、生物化学、细胞生物学等多种手段，研究此通路中还未解决的基本生物学问题，并结合高通量筛选及结构辅助，设计靶向此通路的小分子先导化合物。本项目取得的重要进展包括：1）鉴定了一类进化距离遥远、但结构有相似性的疱疹病毒间质蛋白家族，可以通过一种保守的机制破坏cGAS-DNA液-液相分离；2）建立了基于质谱的高通量筛选方法，并获得多种靶向cGAS的小分子抑制剂；3）建立了基于抗体的高通量筛选方法，并获得多种靶向STING的小分子激动剂；4）揭示了细胞质RNA免疫识别、原核细胞DNA免疫识别、病原对宿主信号通路的干预修饰等分子机制。