The Role of TRIM6 and Ubiquitin in Influenza Virus-Induced Pathology

摘要。甲型流感病毒（IAV）每年引起流行病和危险的大流行，涉及数百万人， 世界各地的疾病和死亡病例。IAV病理学的主要原因是过度炎症， 因此，这项建议的首要目标是了解炎症机制如何被 以促进对病毒感染的疾病耐受性。细胞因子的产生， 炎症，在翻译后水平调节，以平衡有效的抗病毒反应和 破坏性炎症一个主要的分子调控机制涉及信号的泛素化 件.该提案的具体目标是通过以下方式确定炎症调节机制： IAV体内感染过程中的泛素系统。 我们最近报道了E3-Ub连接酶TRIM 6催化非锚定聚Ub链的合成， 其促进抗病毒IFN-I应答。然而，TRIM 6在调节其他炎症反应中的作用， 细胞因子未知。我们产生了TRIM 6敲除小鼠（Trim 6-/-），这提供了一个独特的工具， 在体内鉴定由TRIM 6和未锚定的Ub调节的新免疫途径。我们的初步数据显示 Trim 6-/-小鼠具有较少的病理学迹象，即使在早期时间点IAV滴度增加 感染后。我们还发现CXCL 1（一种众所周知的中性粒细胞化学引诱物）的表达水平降低， 这与IAV感染的Trim 6-/-小鼠的肺中性粒细胞浸润减少相关。我们发现 TRIM 6和未锚定的Ub与PI 3 K/AKT信号传导组分形成复合物，并且它们的磷酸化被激活。 Trim 6-/-细胞受损。我们的数据还表明，感染细胞产生的TNFα诱导致病性 旁观者细胞中的CXCL 1招募中性粒细胞。中性粒细胞在IAV期间被募集到肺中 感染，可以起到保护和有害的作用。然而，是什么因素驱使中性粒细胞引起 感染期间的组织损伤还不太清楚。因此，在知识上存在差距， 中性粒细胞募集的调节机制及其在保护性和非保护性中性粒细胞之间的平衡中的作用 反应和致病性炎症。我们的假设是TRIM 6被TNFα信号激活， 促进早期CXCL 1介导的致病性炎症，从而抑制疾病耐受性。目标1： 将确定TRIM 6诱导的CXCL 1的细胞来源，及其在中性粒细胞向肺募集中的作用， 在IAV感染期间。我们将证明早期CXCL 1的产生在病理学中的作用，以及TNFα是否 参与诱导TRIM 6介导的CXCL 1。在目标2中，我们将确定TRIM 6 和Ub调节下游信号传导的PI 3 K-AKT的激活以及TRIM 6在 感染结果包括鉴定致病性CXCL 1的细胞来源，以及 TRIM 6被激活用于信令的机制。这些信息将指导 通过靶向TRIM 6和CXCL 1产生细胞来减少炎症性疾病的治疗方法。

ABSTRACT. Influenza A virus (IAV) causes annual epidemics and dangerous pandemics involving millions of cases of illness and deaths worldwide. The main cause of pathology from IAV is excessive inflammation, therefore, the overarching goal of this proposal is to learn how mechanisms of inflammation can be manipulated to promote disease tolerance to virus infection. Cytokine production, a chief contributor of inflammation, is regulated at the post-translational level to balance between efficient antiviral responses and damaging inflammation. A major molecular regulatory mechanism involves ubiquitination of signaling components. The specific goal of this proposal is to identify mechanisms of regulation of inflammation by the ubiquitin (Ub) system during IAV infection in vivo. We recently reported that the E3-Ub ligase, TRIM6, catalyzes the synthesis of unanchored poly-Ub chains, which promote antiviral IFN-I responses. However, the role of TRIM6 in regulating other inflammatory cytokines is not known. We generated TRIM6 knockout mice (Trim6-/-), which provides a unique tool to identify novel immune pathways regulated by TRIM6 and unanchored Ub in vivo. Our preliminary data show that Trim6-/- mice have fewer signs of pathology even though there are increased IAV titers at early time points post-infection. We also found reduced expression levels of CXCL1, a well-known neutrophil chemo-attractant, which correlated with reduced neutrophil infiltration to the lungs of IAV-infected Trim6-/- mice. We found that TRIM6 and unanchored Ub form a complex with PI3K/AKT signaling components, and their phosphorylation is impaired in Trim6-/- cells. Our data also suggest that TNFα produced by infected cells induces pathogenic CXCL1 in bystander cells to recruit neutrophils. Neutrophils are known to be recruited to the lung during IAV infection and can play both protective and detrimental roles. However, what factors drive neutrophils to cause tissue damage during infection are not well-understood. Therefore, there is a gap in knowledge on the mechanisms of regulation of neutrophil recruitment and their roles in the balance between protective responses and pathogenic inflammation. Our hypothesis is that TRIM6 is activated by TNFα signaling and promotes early CXCL1-mediated pathogenic inflammation, thereby inhibiting disease tolerance. In Aim 1, we will determine the cellular source of TRIM6-induced CXCL1, and its role in neutrophil recruitment to the lungs, during IAV infection. We will demonstrate the role of early CXCL1 production in pathology and whether TNFα is involved in inducing TRIM6-mediated CXCL1. In Aim 2, we will determine the mechanism by which TRIM6 and Ub modulate the activation of PI3K-AKT for downstream signaling and how TRIM6 is activated during infection. The outcomes include the identification of the cellular source of pathogenic CXCL1, and the mechanism by which TRIM6 is activated for signaling. This information will guide the development of therapeutic approaches by targeting TRIM6 and CXCL1-producing cells to reduce inflammatory diseases.