Biochemical mechanisms of inflammasome function

先天免疫系统是动物和植物的第一道防线，通过及早发现即将发生的威胁并随后触发促炎症反应来协调细胞损伤和感染。含有吡啶 (NLRP) 的类 NOD 受体蛋白亚家族已成为细胞内危险信号的关键传感器。快速发展的生物模型现在表明，各种 NLRP 在启动对细胞损伤的炎症反应中至关重要；然而，有关该蛋白质家族的基本生物化学及其信号复合物的关键方面仍未解决。 NLRP 包含一个具有 ATP 结合和水解特性的中心 NACHT 结构域（有时称为核苷酸结合寡聚结构域或 NOD），该结构域将 NLRP 指定为与​​各种细胞活动相关的较大 ATP 酶 (AAA ATP 酶) 超家族的成员。 NAHT 结构域的酶特性被认为可以调节 NLRP 寡聚化和炎症小体激活，但其结构和功能仍有待了解。 NLRP3 是研究最彻底的，被认为是典型的炎症小体形成成员，但 NLRP3 以及其余 NLRP 蛋白（家族中的 14 个成员）的基本生物化学特征仍未完全表征。关于 NLRP 酶活性和炎症小体形成内在调节的许多假设主要基于有限确凿证据的类比。炎症体激活酶学的进一步表征以及最近揭示的翻译后修饰在调节炎症信号通路中的整合对于全面了解该蛋白质家族至关重要。在这方面，我们提出不同 NLRP 的特定生化特性会导致催化活性的差异，进而影响寡聚化和炎症信号传导。因此，NLRP 蛋白酶学的定义以及 ATP 在驱动炎性体组装和下游信号通路激活中的作用对于增进对这种先天免疫过程的理解非常重要。显然，对整个 NLRP 家族进行整体研究是必要的，我们将创造性地推进对 NLRP 家族作为一个整体及其组装成功能性炎症体的倾向的理解。为了解决知识缺陷，将定义有效生产所有 NLRP 蛋白的系统，完成酶功能的生化评估，开发生物询问的新技术和试剂，并生成催化 NACHT 结构域的精确结构定义。我们在重组 NLRP 蛋白生产方面的技术进步支持炎症体催化功能的生化分析以及结构生物学方法。

The innate immune system acts as the first line of defense for animals and plants in reconciling cellular injury and infection through the early detection of impending threats, and consequential triggering of pro-inflammatory responses. The NOD-like receptors-containing pyrin (NLRP) subfamily of proteins have emerged as key sensors of intracellular danger signals. Rapidly developing biological models now indicate the various NLRPs are of paramount importance in initiating inflammatory responses to cellular injury; however, critical aspects regarding the underlying biochemistry of this protein family and their signaling complexes remain unresolved. NLRPs contain a central NACHT domain with ATP-binding and hydrolysis properties, (sometimes referred to as the nucleotide-binding oligomerization domain or NOD) that designate NLRPs as members of the larger ATPases-Associated with various cellular Activities (AAA+ ATPase) superfamily. The enzymatic properties of NACHT domains are thought to regulate NLRP oligomerization and inflammasome activation, yet much remains to be understood regarding its structure and function. NLRP3 is the most thoroughly studied and is considered to be the prototypical inflammasome-forming member, yet the basic biochemistry of NLRP3 as well as the remaining NLRP proteins (14 members in the family) remains incompletely characterized. Many assumptions regarding the enzymatic activity of NLRPs and the intrinsic regulation of inflammasome formation are based primarily upon analogy with limited corroborating evidence. Further characterization of the enzymology of inflammasome activation as well as the integration of recently revealed post-translational modifications in regulating inflammatory signaling pathways will be critical for a comprehensive understanding of this protein family. In this regard, we propose that specific biochemical properties of different NLRPs drive distinctions in catalytic activities, which in turn can impact upon oligomerization and inflammatory signaling. Thus, a definition of the enzymology of NLRP proteins and the role of ATP in driving inflammasome assembly and activation of downstream signaling pathways will be important to advance understanding of this innate immune process. It is clear that holistic studies of the entire NLRP family are necessary, and we will creatively advance understanding of the NLRP family as a whole and their propensity to assemble into functional inflammasomes. To address the knowledge deficit, systems for the effective production of all NLRP proteins will be defined, biochemical assessments of enzymatic function will be completed, novel technologies and reagents for biological interrogations will be developed, and precise structural definitions of the catalytic NACHT domain will be generated. Our technical advances in recombinant NLRP protein production support biochemical analyses of inflammasome catalytic function as well as structural biology approaches.