DNA sensors and associated signaling pathways in the innate immune response

描述（由申请方提供）：RNA和DNA引发炎症反应，这对于抗微生物免疫至关重要。DNA是炎症细胞因子和类型的有效触发剂 I IFN基因转录，以及caspase-1介导的促炎细胞因子IL-1？IL-18。越来越多的证据表明，DNA识别不仅是抗微生物宿主防御的核心，而且也是DNA疫苗的佐剂活性以及与自身免疫性疾病如系统性红斑狼疮相关的病理学的主要贡献者。因此，理解DNA识别的分子基础至关重要。 我们小组最近的工作涉及PYHIN家族成员在黑素瘤-2（AIM 2）和干扰素诱导蛋白（IFI 16）中的缺失，作为微生物DNA的传感器。这两种蛋白质通过HIN结构域结合DNA。AIM 2通过pyrin结构域与ASC接合以形成半胱天冬酶-1激活炎性体，而IFI 16激活涉及IFN基因刺激物（STING）、TANK结合激酶-1（TBK-1）和干扰素调节因子3（IRF 3）的胞质信号传导途径以调节I型IFN基因的转录。击倒IFI 16，或其小鼠直系同源p204防止病毒DNA触发IRF 3激活和IFN？基因诱导，同时不影响对细胞质RNA的反应。最近的证据还表明，IFI 16可以响应于卡波西肉瘤疱疹病毒感染的核传感而形成炎性体。我们实验室的其他工作也表明，DEAD盒解旋酶DEAD盒蛋白3x（DDX 3x）在TBK 1/IRF 3信号通路中对RNA和细胞质DNA通路（包括IFI 16）都很重要，但其在先天免疫中的作用仍有待充分表征。 本提案中要检验的基本假设是，IFI 16在 DDX 3x通过调节炎症反应在先天免疫和宿主防御微生物病原体中起中心作用，并且DDX 3x是IFI 16信号传导途径的重要下游组分。我们建议探索IFI 16激活的分子机制，并确定IFI 16和DDX 3x在抗病毒宿主防御中的作用。该项目将增加我们对先天免疫系统如何感知病原体的理解，从而产生新的治疗靶点。 公共卫生相关性：细胞具有免疫传感器，可以检测来自入侵病毒的DNA，从而产生由干扰素控制的适当的保护性抗病毒细胞反应。这些反应有时被自身DNA不适当地激活，导致病理性自身免疫反应。我们已经发现一种名为IFI 16的细胞蛋白质就是这样一种传感器，了解它的工作原理将有助于治疗增强或抑制免疫反应，以分别对抗病原体或抑制自身免疫反应。

DESCRIPTION (provided by applicant): RNA and DNA elicit inflammatory responses which are critical for anti-microbial immunity. DNA is a potent trigger of inflammatory cytokine and type I IFN gene transcription, as well as caspase-1-mediated processing of the pro-inflammatory cytokines IL-1? and IL-18. Growing evidence indicates that DNA recognition is central not only to anti-microbial host defenses but is also a major contributor to the adjuvant activity of DNA vaccines as well as the pathology associated with autoimmune diseases such as Systemic Lupus Erythematosis. It is therefore critical that we understand the molecular basis of DNA recognition. Recent work from our group has implicated the PYHIN family members Absent in melanoma-2 (AIM2) and the interferon-inducible protein (IFI16) as sensors of microbial DNA. Both proteins bind DNA via HIN domains. AIM2 engages ASC via a pyrin domain to form a caspase-1 activating inflammasome while IFI16 activates a cytosolic signaling pathway involving Stimulator of IFN genes (STING), TANK binding kinase-1 (TBK-1) and interferon regulatory factor 3 (IRF3) to regulate transcription of type I IFN genes. Knockdown of IFI16, or its murine ortholog p204 prevents viral DNA from triggering IRF3 activation and IFN? gene induction, while not affecting responses to cytosolic RNA. Recent evidence also indicates that IFI16 can form an inflammasome in responses to nuclear sensing of Kaposi's Sarcoma Herpes Virus infection. Additional work from our laboratories has also implicated the DEAD box helicase DEAD box protein 3x (DDX3x) in the TBK1/IRF3 signaling pathway important for both RNA and cytoplasmic DNA pathways (including for IFI16), but its role in innate immunity remains to be fully characterized. The underlying hypothesis to be tested in this proposal is that IFI16 plays a central role in innate immunity and host-defense to microbial pathogens by regulating inflammatory responses and that DDX3x is an important downstream component of the IFI16 signaling pathway. We propose to explore the molecular mechanisms of IFI16 activation and define the role of IFI16 and DDX3x in anti-viral host-defenses. This project will increase our understanding of how the innate immune system senses pathogens, leading to novel therapeutic targets. PUBLIC HEALTH RELEVANCE: Cells have immune sensors that detect DNA from invading viruses, giving rise to appropriate protective anti-viral cellular responses controlled by interferons. These responses are at times inappropriately activated by self-DNA, leading to pathological autoimmune responses. We have discovered that a cellular protein called IFI16 is such a sensor, and understanding how it works will lead to therapies to enhance or dampen immune responses to fight pathogens or suppressing autoimmune responses respectively.