病原体识别受体NLR家族蛋白质及其复合物炎症小体形成和激活动态过程的分子机理研究

The vertebrate immune system consists of two arms: the innate and adaptive immune systems. The innate immune system is essential both in forming the first line of defense against the invading pathogens and in activating and shaping the adaptive immune system. The pattern recognition receptors (PRR) detect the presence of invading pathogens and are paramount in innate immune response. The extensively studied Toll-like receptors (TLRs) and newly identified NOD-like receptors (NLRs) are key families of PPRs in the innate immune response. The NLRs are cytosolic and respond to a diverse range of intracellular PAMPs (Pathogen-associated Molecular Patterns) and/or DAMPs (Damage-associated Molecular Patterns). The intracellular NLRs organize signaling complexes such as inflammasomes and NOD signalosomes. Inflammasomes and signalosomes are molecular platforms activated upon cellular pathogen infection or stress and subsequently trigger the innate immune defenses. The precise mechanism by which this "sensing" occurs, however, remains a major challenge in the field. As the key PAMPs sensor, NLR proteins have rapidly emerged as central regulators of immunity and inflammation with demonstrated direct relevance to various human diseases, however, essential knowledge regarding to the structural basis of pathogen recognition and inflammasome formation is still missing, which has hampered the effort to prevent the pathogen invasion and further more, to control the inflammation response of our body, and to develop efficient pharmaceutical strategies for various immune system diseases. Having the full-length structure is essential to elucidate the molecular details of inflammasome induced by PAMPs binding. However, due to their high molecular weight, complicated domain organization, highly hydrophobic feature, and oligomerization of the active form, "NLRs are notoriously difficult to purify, and thus resolving their full-length structure will be a major technical hurdle" (Ting JP., et al., Science, 2010, 327 (5963): 286-290). The research project we are proposing here is to understand the dynamic structure and the precise mechanism of this receptor family and how they sense various pathogens and trigger immune responses, which remains mostly unknown today.As we learn more about the structure and formation of inflammasome, and more about the molecular details of host-pathogen recognition, the probability of interfering in the pathogenesis of infectious diseases and autoimmune diseases will certainly increase in the coming years.

病原体和宿主的相互作用，生物体识别和清除抗原性异物是现代免疫学的核心研究内容。对病原体的快速和特异性识别是宿主抵御病原入侵的前提。新近发现的NOD样受体（NLRs）是一类全新的病原识别受体，在结合病原体配体后组装成多组分功能复合物，即炎症小体。最新研究表明NLR是天然免疫和炎症反应的中心调节蛋白，因此成为炎症、自身免疫等疾病的药物标靶。NLR全长蛋白质的重组表达，以及高分子量的炎症小体的组装过程是目前对NLR结构研究和炎症小体激活机理研究的主要技术难关和瓶颈。本项目拟通过整合结构生物学途径揭示NLR蛋白质、以NLR为核心的炎症小体及其介导的炎症反应的激活机理以及病原体识别的分子基础，诠释NLR作为天然免疫中一种古老而保守的病原识别受体在病原体和宿主相互作用的普遍规律和结构特征。研究结果具有重要的基础科学价值，而且可能为寻找病原体感染性疾病诊治提供新思路，为创新型药物的研发提供理论基础。

病原体和宿主的相互作用，生物体识别和清除抗原性异物是现代免疫学的核心研究内容。新近发现的NOD样受体（NLRs）是一类全新的天然免疫病原识别受体，在结合病原体配体后组装成多组分功能复合物，即炎症小体。最新研究表明NLR是天然免疫和炎症反应的中心调节蛋白，因此成为炎症、自身免疫等疾病的药物标靶。NLRP6炎症小体在肠道菌群-宿主互作中起着关键性的作用。本项目通过整合结构生物学途径解析了NLRP6单体（非活化构象）的结构，成功鉴定出细菌粘多糖LPS是NLRP6的配体，解析了NLRP6和配体LPS结合的二聚体结构；发现在NLRP6结合配体LPS之后，能在ATP的诱导下形成更高的高聚；成功解析了NLRP6在结合LPS以及ATP以后的多聚体的电镜结构，包括四聚体，六聚体电镜结构的三维重构；获取了更高高聚的电镜照片，并在细胞水平成功验证了LPS对NLRP6多聚化和激活的影响，同时，根据我们的数据，提出NLRP6的激活是一个两步过程的假说。本研究对LPS诱导的炎症小体提出了新的机制，揭示了NLRP6炎症小体形成的结构基础。