The NLR family pyrin domain containing 3 (NLRP3) inflammasome is one of the best-characterized inflammasomes in humans and other mammals. However, knowledge about the NLRP3 inflammasome in nonmammalian species remains limited. Here, we report the molecular and functional identification of an NLRP3 homolog (DrNLRP3) in a zebrafish (Danio rerio) model. We found that DrNLRP3's overall structural architecture was shared with mammalian NLRP3s. It initiates a classical inflammasome assembly for zebrafish inflammatory caspase (DrCaspase-A/-B) activation and interleukin 1β (DrIL-1β) maturation in an apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC)-dependent manner, in which DrNLRP3 organizes DrASC into a filament that recruits DrCaspase-A/-B by homotypic pyrin domain (PYD)-PYD interactions. DrCaspase-A/-B activation in the DrNLRP3 inflammasome occurred in two steps, with DrCaspase-A being activated first and DrCaspase-B second. DrNLRP3 also directly activated full-length DrCaspase-B and elicited cell pyroptosis in a gasdermin E (GSDME)-dependent but ASC-independent manner. These two events were tightly coordinated by DrNLRP3 to ensure efficient IL-1β secretion for the initiation of host innate immunity. By knocking down DrNLRP3 in zebrafish embryos and generating a DrASC-knockout (DrASC-/-) fish clone, we characterized the function of the DrNLRP3 inflammasome in anti-bacterial immunity in vivo The results of our study disclosed the origin of the NLRP3 inflammasome in teleost fish, providing a cross-species understanding of the evolutionary history of inflammasomes. Our findings also indicate that the NLRP3 inflammasome may coordinate inflammatory cytokine processing and secretion through a GSDME-mediated pyroptotic pathway, uncovering a previously unrecognized regulatory function of NLRP3 in both inflammation and cell pyroptosis.

中文翻译：

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斑马鱼NLRP3炎性小体在依赖ASC的白介素1β成熟和Gasdermin E介导的细胞凋亡中具有功能性作用。

包含3个（NLRP3）炎性小体的NLR家族吡喃结构域是人类和其他哺乳动物中最典型的炎性小体之一。但是，关于非哺乳动物物种中NLRP3炎性小体的知识仍然有限。在这里，我们报告在斑马鱼（Danio rerio）模型中的NLRP3同源（DrNLRP3）的分子和功能鉴定。我们发现DrNLRP3的整体结构与哺乳动物NLRP3共享。它启动了经典的炎症小体组装，以斑马鱼炎症半胱天冬酶（DrCaspase-A / -B）激活和白介素1β（DrIL-1β）成熟，并以凋亡相关的斑点样蛋白质形式出现，其中包含caspase-recruitment结构域（ASC）依赖性方式，其中DrNLRP3将DrASC组织成一条细丝，该细丝通过同型吡啶结构域（PYD）-PYD相互作用募集DrCaspase-A / -B。DrNLRP3炎性小体中的DrCaspase-A / -B激活分为两个步骤，首先激活DrCaspase-A，然后激活DrCaspase-B。DrNLRP3还直接激活全长DrCaspase-B，并以依赖于Gasdermin E（GSDME）但不依赖ASC的方式引发细胞凋亡。这两个事件由DrNLRP3紧密协调，以确保有效的IL-1β分泌来启动宿主先天免疫。通过敲除斑马鱼胚胎中的DrNLRP3并产生DrASC基因敲除（DrASC-/-）鱼克隆，我们表征了DrNLRP3炎性小体在体内抗菌免疫中的功能。我们的研究结果揭示了NLRP3炎性小体的起源。硬骨鱼类，提供了跨物种对炎症小体进化史的理解。