Duong Bao H, Onizawa Michio, Oses-Prieto Juan A, Advincula Rommel, Burlingame Alma, Malynn Barbara A, Ma Averil
Department of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, CA 94143, USA.
Immunity. 2015 Jan 20;42(1):55-67. doi: 10.1016/j.immuni.2014.12.031.
Inappropriate inflammasome activation contributes to multiple human diseases, but the mechanisms by which inflammasomes are suppressed are poorly understood. The NF-κB inhibitor A20 is a ubiquitin-modifying enzyme that might be critical in preventing human inflammatory diseases. Here, we report that A20-deficient macrophages, unlike normal cells, exhibit spontaneous NLRP3 inflammasome activity to LPS alone. The kinase RIPK3, but not the adaptor MyD88, is required for this response. In normal cells, A20 constitutively associates with caspase-1 and pro-IL-1β, and NLRP3 activation further promotes A20 recruitment to the inflammasome. Pro-IL-1β also co-immunoprecipitates with RIPK1, RIPK3, caspase-1, and caspase-8 in a complex that is modified with K63-linked and unanchored polyubiquitin. In A20-deficient macrophages, this pro-IL-1β-associated ubiquitination is markedly increased in a RIPK3-dependent manner. Mass spectrometric and mutational analyses reveal that K133 of pro-IL-1β is a physiological ubiquitination site that supports processing. Our study reveals a mechanism by which A20 prevents inflammatory diseases.
不适当的炎性小体激活会导致多种人类疾病，但人们对炎性小体被抑制的机制了解甚少。核因子κB抑制剂A20是一种泛素修饰酶，可能在预防人类炎症性疾病中起关键作用。在此，我们报告，与正常细胞不同，A20缺陷型巨噬细胞对单独的脂多糖表现出自发性NLRP3炎性小体活性。这种反应需要激酶RIPK3，而不是衔接蛋白MyD88。在正常细胞中，A20与半胱天冬酶-1和前白细胞介素-1β组成性结合，NLRP3激活进一步促进A20募集到炎性小体。前白细胞介素-1β还与RIPK1、RIPK3、半胱天冬酶-1和半胱天冬酶-8在一个用K63连接的和非锚定的多聚泛素修饰的复合物中共同免疫沉淀。在A20缺陷型巨噬细胞中，这种与前白细胞介素-1β相关的泛素化以RIPK3依赖的方式显著增加。质谱和突变分析表明，前白细胞介素-1β的K133是一个支持加工的生理性泛素化位点。我们的研究揭示了A20预防炎症性疾病的机制。
