Department of Biochemistry and Molecular Biology and the Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
J Biol Chem. 2012 Oct 19;287(43):36617-22. doi: 10.1074/jbc.M112.407130. Epub 2012 Sep 4.
The NLRP3 inflammasome is a key component of the innate immune response to pathogenic infection and tissue damage. It is also involved in the pathogenesis of a number of human diseases, including gouty arthritis, silicosis, atherosclerosis, and type 2 diabetes. The assembly of the NLRP3 inflammasome requires a priming signal derived from pattern recognition or cytokine receptors, followed by a second signal derived from extracellular ATP, pore-forming toxins, or crystalline materials. How these two signals activate the NLRP3 inflammasome is not yet clear. Here, we show that in mouse macrophages, signaling by the pattern recognition receptor TLR4 through MyD88 can rapidly and non-transcriptionally prime NLRP3 by stimulating its deubiquitination. This process is dependent on mitochondrial reactive oxygen species production and can be inhibited by antioxidants. We further show that signaling by ATP can also induce deubiquitination of NLRP3 by a mechanism that is not sensitive to antioxidants. Pharmacological inhibition of NLRP3 deubiquitination completely blocked NLRP3 activation in both mouse and human cells, indicating that deubiquitination of NLRP3 is required for its activation. Our findings suggest that NLRP3 is activated by a two-step deubiquitination mechanism initiated by Toll-like receptor signaling and mitochondrial reactive oxygen species and further potentiated by ATP, which could explain how NLRP3 is activated by diverse danger signals.
NLRP3 炎性小体是先天免疫反应对病原感染和组织损伤的关键组成部分。它也参与了多种人类疾病的发病机制，包括痛风性关节炎、矽肺、动脉粥样硬化和 2 型糖尿病。NLRP3 炎性小体的组装需要源自模式识别或细胞因子受体的初始信号，然后是源自细胞外 ATP、孔形成毒素或结晶物质的第二信号。这两个信号如何激活 NLRP3 炎性小体尚不清楚。在这里，我们表明在小鼠巨噬细胞中，通过 MyD88 的模式识别受体 TLR4 的信号可以通过刺激其去泛素化来快速且非转录地启动 NLRP3。这个过程依赖于线粒体活性氧的产生，并且可以被抗氧化剂抑制。我们进一步表明，ATP 的信号也可以通过一种对抗氧化剂不敏感的机制诱导 NLRP3 的去泛素化。NLRP3 去泛素化的药理学抑制完全阻断了小鼠和人细胞中 NLRP3 的激活，表明 NLRP3 的去泛素化是其激活所必需的。我们的发现表明，NLRP3 通过由 Toll 样受体信号和线粒体活性氧启动的两步去泛素化机制激活，并且进一步被 ATP 增强，这可以解释 NLRP3 如何被多种危险信号激活。
