Wang Wenbiao, Xiao Feng, Wan Pin, Pan Pan, Zhang Yecheng, Liu Fang, Wu Kailang, Liu Yingle, Wu Jianguo
State Key Laboratory of Virology and College of Life Sciences, Wuhan University, Wuhan, China.
PLoS Pathog. 2017 Jan 6;13(1):e1006123. doi: 10.1371/journal.ppat.1006123. eCollection 2017 Jan.
Activation of NLRP3 inflammasome is important for effective host defense against invading pathogen. Together with apoptosis-associated speck-like protein containing CARD domain (ASC), NLRP3 induces the cleavage of caspase-1 to facilitate the maturation of interleukin-1beta (IL-1β), an important pro-inflammatory cytokine. IL-1β subsequently plays critical roles in inflammatory responses by activating immune cells and inducing many secondary pro-inflammatory cytokines. Although the role of NLRP3 inflammasome in immune response is well defined, the mechanism underlying its assembly modulated by pathogen infection remains largely unknown. Here, we identified a novel mechanism by which enterovirus 71 (EV71) facilitates the assembly of NLRP3 inflammasome. Our results show that EV71 induces production and secretion of IL-1β in macrophages and peripheral blood mononuclear cells (PBMCs) through activation of NLRP3 inflammasome. EV71 replication and protein synthesis are required for NLRP3-mediated activation of IL-1β. Interestingly, EV71 3D protein, a RNA-dependent RNA polymerase (RdRp) was found to stimulate the activation of NLRP3 inflammasome, the cleavage of pro-caspase-1, and the release of IL-1β through direct binding to NLRP3. More importantly, 3D interacts with NLRP3 to facilitate the assembly of inflammasome complex by forming a 3D-NLRP3-ASC ring-like structure, resulting in the activation of IL-1β. These findings demonstrate a new role of 3D as an important player in the activation of inflammatory response, and identify a novel mechanism underlying the modulation of inflammasome assembly and function induced by pathogen invasion.
NLRP3炎性小体的激活对于宿主有效抵御入侵病原体至关重要。NLRP3与含半胱天冬酶激活和招募结构域（CARD）的凋亡相关斑点样蛋白（ASC）一起，诱导半胱天冬酶-1的切割，以促进白细胞介素-1β（IL-1β）的成熟，IL-1β是一种重要的促炎细胞因子。IL-1β随后通过激活免疫细胞和诱导许多继发性促炎细胞因子在炎症反应中发挥关键作用。尽管NLRP3炎性小体在免疫反应中的作用已得到明确界定，但其组装受病原体感染调节的机制仍 largely 未知。在此，我们确定了肠道病毒71型（EV71）促进NLRP3炎性小体组装的新机制。我们的结果表明，EV71通过激活NLRP3炎性小体诱导巨噬细胞和外周血单核细胞（PBMC）中IL-1β的产生和分泌。NLRP3介导的IL-1β激活需要EV71复制和蛋白质合成。有趣的是，发现EV71 3D蛋白，一种RNA依赖性RNA聚合酶（RdRp），通过直接与NLRP3结合来刺激NLRP3炎性小体的激活、前半胱天冬酶-1的切割以及IL-1β的释放。更重要的是，3D与NLRP3相互作用，通过形成3D-NLRP3-ASC环状结构促进炎性小体复合物的组装，从而导致IL-1β的激活。这些发现证明了3D作为炎症反应激活中的重要参与者的新作用，并确定了病原体入侵诱导炎性小体组装和功能调节的新机制。
