Deciphering the Role of dNTP Metabolism in Innate Immunity

项目摘要 平衡供应脱氧核苷三磷酸(DNTPs)是DNA的组成成分，对于 核基因组和线粒体基因组的合成或修复，而其不平衡导致基因组 导致细胞损伤和动态平衡被破坏的不稳定性。对dNTP代谢的研究已经 传统上在高度增殖(如肿瘤细胞)、代谢活跃(如肌肉细胞)或 由于dNTPs在满足细胞生长、能量生产和生产的需求中的关键作用而感染病毒的细胞 病毒复制。然而，对dNTP代谢在先天性免疫中的作用知之甚少，尤其是 在非病原体诱导的免疫激活的背景下。先天免疫激活的一个标志是 含3(NLRP3)炎症体的结节样受体吡咯结构域的组装 组织损伤的免疫传感器。NLRP3炎症体由传感器NLRP3、适配器 ASC(凋亡性相关刺激性蛋白)及其效应因子caspase-1。NLRP3的组装 炎症体有两个不同的步骤：“启动”和“激活”。启动需要快速的核因子-kB 激活启动前-IL-1β的从头合成以及增加NLRP3的数量。相比之下， 激活涉及NLRP3炎症小体机械的组装，导致自动切割和 激活Caspase-1，然后将未成熟的前IL-1β转化为具有生物活性的IL-1β-a 引发炎症的促炎细胞因子。尽管适当控制了NLRP3炎症小体的活动 允许通过刺激损伤清除和组织来恢复创伤组织损伤后的动态平衡 修复，其异常和长时间的激活也促进了许多毁灭性的快速进展 这些疾病包括痛风性关节炎、阿尔茨海默病、动脉粥样硬化、黄斑变性和癌症。它 因此，对于了解NLRP3炎症体活动是如何在先天性免疫细胞中受到调节至关重要的。 最近，我们发现dNTP中的两个关键酶CMPK2或SAMHD1的基因缺失 分别负责合成或降解dNTPs的代谢途径，协调NLRP3 炎性小体激活。因此，这个Mira R35项目的最终目标是建立dNTP 代谢作为天然免疫调节的新层次，并进一步阐明其潜在的机制 行动。为了实现这一目标，将探讨三个主要的科学问题：(1)炎性小体如何 启动调节dNTP代谢酶的功能？(2)dNTP代谢如何调控NLRP3 炎性小体激活？最后，由于NLRP3炎症体过度激活是共同的致病标志 在许多疾病中，我们进一步询问：(3)常见的疾病风险因素，如衰老和肥胖， 巨噬细胞dNTP代谢紊乱，从而允许NLRP3炎症体过度激活？ 该项目的完成不仅将填补先天免疫领域的一个重要知识空白，而且可能 并指导新的治疗方法的开发，以防止NLRP3炎症体过度激活。

Project Summary A balanced supply of deoxynucleoside triphosphates (dNTPs), the building blocks for DNA, is vital for the synthesis or repair of both nuclear and mitochondrial genomes, whereas its imbalance results in genome instability that precipitates cellular damage and breach of homeostasis. Research on dNTP metabolism has been traditionally conducted in highly proliferative (e.g. tumor cells), metabolically active (e.g. muscle cells) or virus-infected cells due to the key roles of dNTPs in fulfilling demands for cell growth, energy production and viral replication. However, little is known regarding the role of dNTP metabolism in innate immunity, especially in the context of nonpathogen-induced immune activation. A hallmark of innate immune activation is the assembly of the Nod-like receptor pyrin domain containing 3 (NLRP3) inflammasome—a dominant innate immune sensor for tissue damage. The NLRP3 inflammasome is composed of the sensor NLRP3, the adaptor ASC (apoptosis associated spike-like protein) and the effector pro-caspase-1. Assembly of the NLRP3 inflammasome proceeds with two distinct steps: ‘priming’ and ‘activation’. Priming entails rapid NF-kB activation for initiating de novo synthesis of pro-IL-1β as well as increasing the amount of NLRP3. In contrast, activation involves the assembly of the NLRP3 inflammasome machinery, resulting in autocleavage and activation of caspase-1 which then converts immature pro-IL-1β into bioactive IL-1β—a powerful proinflammatory cytokine that ignites inflammation. Although properly controlled NLRP3 inflammasome activity allows for restoration of homeostasis after traumatic tissue injury by stimulating damage clearance and tissue repair, its aberrant and prolonged activation also promotes the rapid progression of many devastating disorders, including gouty arthritis, Alzheimer’s disease, atherosclerosis, macular degeneration and cancer. It is therefore crucial to understand how NLRP3 inflammasome activity is regulated in innate immune cells. Recently, we discovered that genetic deletion of CMPK2 or SAMHD1, two key enzymes within the dNTP metabolic pathways responsible for synthesizing or degrading dNTPs respectively, orchestrates NLRP3 inflammasome activation. Therefore, the ultimate goal of this MIRA R35 project is to establish dNTP metabolism as a new layer for innate immune regulation and further delineate its underlying mechanism of action. To achieve this goal, three major scientific questions will be pursued: (1) how does inflammasome priming regulate the function of dNTP metabolic enzymes? (2) how does dNTP metabolism control NLRP3 inflammasome activation? Lastly, since NLRP3 inflammasome overactivation is a shared pathogenic hallmark of many diseases, we further asked: (3) do common disease risk factors, such as aging and obesity, dysregulate macrophage dNTP metabolism, thereby permitting NLRP3 inflammasome overactivation? Completion of this project will not only fill an important knowledge gap in the innate immunity field, but may also guide new therapy development to prevent NLRP3 inflammasome hyperactivation.