Role reversal of MAVS in bacterial sepsis

脓毒症是微生物感染的常见且危及生命的并发症。估计有超过 在美国每年发生750，000例脓毒症，死亡率保持在20 - 50%左右， 重症监护支持的最新进展。在目前缺乏FDA批准的药物化合物的情况下， 仍然迫切需要对潜在的细胞和分子 脓毒症的机制宿主反应失调是肺结核病理生理过程中的一个突出特征， 细菌性败血症，但其整合分子途径的微妙平衡似乎并不完全清楚。 线粒体抗病毒信号蛋白（MAVS）是线粒体外膜上的一种衔接分子 并且在专职吞噬细胞中高度表达。MAVS由细胞质RNA解旋酶RIG-1激活。 I和MDA5，并赋予针对病毒感染的保护。令人惊讶的是，我们的初步发现表明 小鼠中MAVS或RIG-I/MDA5的缺失赋予对死亡的巨大抵抗力并调节吞噬细胞 转录组，免疫蛋白酶体，细胞外陷阱，IL-6/IL-12细胞因子和凝血过程中 多微生物细菌性败血症。细菌RNA是一种与生存力相关的病原体模式（"vita-PAMPs"） 通过巨噬细胞中的MAVS通路感知。总之，这些发现表明， 与病毒感染期间的保护性MAVS通路功能相反，细菌败血症期间的MAVS。 为了验证我们的中心假设，即MAVS信号传导提供了一个致命的开关，用于阻断有利的脓毒症 结果，我们将追求3个具体目标：（1）我们将研究基因表达，激活机制， MAVS在专职吞噬细胞（巨噬细胞，中性粒细胞）中的信号事件和功能作用 多微生物细菌性败血症。对于这些研究，使用MAVS的全部或条件性基因缺失的小鼠，或 RIG-I/MDA5传感器可用。将使用CRISPR-Cas9产生MAVS缺陷型人巨噬细胞。 (2)我们将确定MAVS诱导的转录因子如何促进免疫蛋白酶体的基因表达 亚基，在细菌败血症期间免疫蛋白酶体的多效性功能是什么，以及 免疫蛋白酶体形成巨噬细胞的蛋白质组和转录组。这些研究将包括使用 所有三种调节性免疫蛋白酶体亚基（PSMB 8/9/10）的三重敲除小鼠。(3)我们将研究如何 MAVS途径放大了细菌性脓毒症的有害分子后遗症， 细胞外陷阱（NET/MET）、IL-6/IL-12细胞因子、脓毒性凝血病和免疫抑制; 导致组织损伤、器官功能障碍和败血症致死。特别是，我们将考虑一个新的作用， 免疫蛋白酶体在亚细胞蛋白降解中促进细胞外陷阱的形成。总的来说， 阐明MAVS通路在细菌感染过程中的参与将提供 新的和重要的信息，并可能增加重要的见解，以指导今后的努力， 治疗败血症。

Sepsis is a frequent and life-threatening complication of microbial infections. It is estimated that more than 750,000 annual cases of sepsis occur in the United States and mortality rates remain around 20-50% despite recent advances of critical care support. In the current absence of FDA-approved pharmacologic compounds, there remains an urgent need for a complete characterization of the underlying cellular and molecular mechanisms of sepsis. The dysregulated host response is a prominent feature during the pathophysiology of bacterial sepsis, but the delicate balance of its integrating molecular pathways appear not entirely clear. Mitochondrial antiviral-signaling protein (MAVS) is an adaptor molecule in the outer mitochondrial membrane and is highly expressed in professional phagocytes. MAVS is activated by the cytoplasmic RNA helicases, RIG- I and MDA5, and confers protection against viral infections. Surprisingly, our preliminary findings suggest deletion of MAVS or RIG-I/MDA5 in mice confers immense resistance to mortality and modulates phagocyte transcriptomes, immunoproteasomes, extracellular traps, IL-6/IL-12 cytokines and blood coagulation during polymicrobial bacterial sepsis. Bacterial RNAs are a viability-associated pathogen patterns (`vita-PAMPs') sensed by the MAVS pathway in macrophages. Together, these findings suggest a detrimental role reversal of MAVS during bacterial sepsis as opposed to protective MAVS pathway functions during infections with viruses. To test our central hypothesis that MAVS signaling provides a lethal switch for obstructing favorable sepsis outcomes, we will pursue 3 specific aims: (1) We will study the gene expression, activation mechanisms, signaling events and functional roles of MAVS in professional phagocytes (macrophages, neutrophils) during polymicrobial bacterial sepsis. For these studies, mice with total or conditional gene deletion of MAVS, or the RIG-I/MDA5 sensors are available. MAVS-deficient human macrophages will be generated using CRISPR-Cas9. (2) We will determine how MAVS-induced transcription factors promote gene expression of immunoproteasome subunits, what the pleiotropic functions of the immunoproteasome are during bacterial sepsis, and how the immunoproteasome shapes the proteomes and transcriptomes of macrophages. These studies will include using triple-knockout mice for all three regulatory immunoproteasome subunits (PSMB8/9/10). (3) We will study how the MAVS pathway amplifies the harmful molecular sequelae of bacterial sepsis focusing on phagocyte extracellular traps (NETs/METs), IL-6/IL-12 cytokines, septic coagulopathy and immunosuppression; which all contribute to tissue injury, organ dysfunction and sepsis lethality. In particular, we will consider a novel role of the immunoproteasome in subcellular protein degradation for facilitating extracellular trap formation. In summary, elucidating the previously unsuspected involvement of the MAVS pathway during bacterial infection will provide novel and important information and may add critical insights for guiding future efforts to develop effective therapies for sepsis.