Lipopolysaccharide Primes the NALP3 Inflammasome by Inhibiting Its Ubiquitination and Degradation Mediated by the SCFFBXL2 E3 Ligase
Lipopolysaccharide Primes the NALP3 Inflammasome by Inhibiting Its Ubiquitination and Degradation Mediated by the SCFFBXL2 E3 Ligase
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DOI：
10.1074/jbc.m115.645549
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发表时间：
2015-07-17
影响因子：
4.8
通讯作者：
Mallampalli, Rama K.
中科院分区：
文献类型：
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作者：
Han, SeungHye;Lear, Travis B.;Mallampalli, Rama K.
炎症体是一种多蛋白复合体，通过增加关键细胞因子的产生和细胞释放来增强促炎反应。具体地说，NALP3炎症体需要两个步骤的信号传递，即启动和激活，以发挥释放促炎细胞因子IL-1β和IL-18的功能。启动过程，通过未知的机制，增加细胞中NALP3和前IL-1β的蛋白水平。在这里，我们表明，内毒素增加了NALP3蛋白的寿命，而不会显著改变人类细胞中的稳态mRNA。脂多糖暴露通过诱导靶向Fbxl2的E3连接酶组分Fbxo3的水平，减少了泛素介导的NALP3蛋白酶体的加工。后者是NALP3降解的内源性调节因子。Fbxl2识别NALP3中的Trp-73相互作用，并靶向NALP3中的Lys-689进行泛素连接和降解。一种独特的Fbxo3小分子抑制剂可恢复Fbxl2水平，导致细胞内NALP3蛋白水平下降，从而减少NALP3激活后人炎症细胞中IL-1β和IL-18的释放。我们的发现揭示了NALP3作为Fbxl2的分子靶点，并提示针对炎症小体的治疗性靶点可能作为临床前干预的平台。
The inflammasome is a multiprotein complex that augments the proinflammatory response by increasing the generation and cellular release of key cytokines. Specifically, the NALP3 inflammasome requires two-step signaling, priming and activation, to be functional to release the proinflammatory cytokines IL-1 beta and IL-18. The priming process, through unknown mechanisms, increases the protein levels of NALP3 and pro-IL-1 beta in cells. Here we show that LPS increases the NALP3 protein life-span without significantly altering steady-state mRNA in human cells. LPS exposure reduces the ubiquitin-mediated proteasomal processing of NALP3 by inducing levels of an E3 ligase component, FBXO3, which targets FBXL2. The latter is an endogenous mediator of NALP3 degradation. FBXL2 recognizes Trp-73 within NALP3 for interaction and targets Lys-689 within NALP3 for ubiquitin ligation and degradation. A unique small molecule inhibitor of FBXO3 restores FBXL2 levels, resulting in decreased NALP3 protein levels in cells and, thereby, reducing the release of IL-1 beta and IL-18 in human inflammatory cells after NALP3 activation. Our findings uncover NALP3 as a molecular target for FBXL2 and suggest that therapeutic targeting of the inflammasome may serve as a platform for preclinical intervention.