cGAS-STING信号通路在自身免疫性疾病中的研究进展

存在于细胞质中的游离DNA可被机体固有免疫系统识别清除,但其具体机制尚不明确。近年来越来越多的研究发现,环鸟苷酸-腺苷酸合成酶(cyclic guanosine monophosphate-adenosine monophosphate synthase, cGAS)-干扰素基因刺激蛋白(stimulator of interferon gene, STING)通路参与固有免疫并发挥重要的免疫调控作用。cGAS-STING信号通路参与胞内微生物和自身胞质中异常核酸的识别。该综述阐述cGAS-STING信号通路介导自身免疫性疾病发生发展的相关研究,旨在为自身免疫性疾病的防治寻找有效的靶点。     

cGAS——一种胞质DNA感应器的研究进展

机体天然免疫领域的最新研究发现了一系列具有感应胞内核酸作用的蛋白质,其中受到广泛关注且已经得到确认的是一种被称为cGAS的蛋白质。cGAS全称Cyclic guanosine monophosphate-adenosine monophosphate synthase,即环磷酸鸟苷-腺苷合成酶。大量的研究已经发现cGAS能感应入侵宿主细胞的病毒性或细菌性DNA,通过重要分子cGAMP、STING的相关作用,产生大量的干扰素以及其他种类的细胞因子,进而发挥重要的抗病毒作用。本文就cGAS-DNA感应通路以及cGAS与抗病毒免疫反应及自身免疫性疾病的研究进展进行综述,以期为其功能研究提供良好的理论基础。     

胞质DNA受体及其对干扰素调控作用研究进展

机体对入侵抗原的识别是启动固有免疫的关键步骤.当哺乳动物细胞受到微生物病原体感染后,细胞即通过表达多种胞质DNA受体来识别感染信号并激活多种信号转导通路.有效的免疫反应通常需要通过各亚细胞结构中的多种受体对抗原依次检测.近年来,国内外学者接连发现了STING、cGAS、DDX41、IFI16、LRRFIP1、DNA-PK、MRE11、DAI和AIM2等众多胞质DNA受体,并对其诱导干扰素产生的过程进行了研究.这将对更全面的认识固有免疫应答产生重要意义.     

干扰素基因刺激蛋白功能调控机制的研究进展

Ⅰ型干扰素(interferon,IFN-I)在固有免疫抗病毒中发挥着关键作用,其产生与环状GMP-AMP合成酶(cyclic GMP-AMP synthase,cGAS)-干扰素基因刺激蛋白(stimulator of interferon gene,STING)信号通路对胞质内非我DNA的识别以及对下游激酶TBK1和干扰素调节因子3(interferon regulatory factor 3,IRF3)的活化密不可分。STING作为此条信号通路的核心部分,其本身的修饰和稳定性对机体能否正确有效地产生免疫应答至关重要。STING本身的功能调控机制主要分为3种:一是通过泛素化修饰促进或抑制STING信号通路;二是通过磷酸化调节STING信号通路活化的持续时间和强度;三是对STING-TBK1复合体稳定性的调节。STING功能调控机制的认识为病毒性疾病和炎症性疾病的治疗提供了新的途径。     

cGAS-STING信号通路与代谢性疾病的研究进展

cGAS-STING信号通路是检测细胞内DNA的主要途径之一,病毒、 细菌和自体DNA都可通过cGAS-STING信号通路激活免疫系统.其中自体DNA通过cGAS-STING信号通路与非酒精性脂肪肝、脂肪组织炎症、胰岛素抵抗、糖代谢异常等代谢性疾病的发生相关.文章结合近年cGAS-STING信号通路与代谢性疾病的相关研...     

右美托咪定通过cGAS-STING通路介导的免疫调控机制对胃癌细胞恶性生物学行为的影响

目的：探究右美托咪定（DEX）通过环磷酸鸟苷-磷酸腺苷合酶-干扰素基因刺激因子（cGAS-STING）通路介导的免疫调控机制对胃癌（GC）细胞恶性生物学行为的影响。方法：将GC细胞株MGC-803随机分为对照组（Control组,空白培养基处理）、DEX低浓度组（DEX-L组,1 ng/ml）、DEX中浓度组（DEX-M组,10 ng/ml）、DEX高浓度组（DEX-H组,100 ng/ml）和DEX高浓度+cGAS抑制剂RU.521组（DEX-H+RU.521组,100 ng/ml DEX+1.0μmol/L RU.521）。CCK-8法检测细胞增殖情况。细胞划痕实验检测各组细胞的迁移能力。Transwell实验检测各组细胞的侵袭能力。流式细胞术检测细胞凋亡率。ELISA检测细胞中IL-2、干扰素-γ(IFN-γ)、肿瘤坏死因子α(TNF-α)水平。实时荧光定量PCR(RT-qPCR)法检测细胞cGAS、STING、Ⅰ型干扰素（IFN-Ⅰ）mRNA的表达水平。Western blot检测细胞cGAS、STING、Bax、细胞周期蛋白D1(CyclinD1)、基质金属蛋白酶9(MMP9...     

模式识别受体DNA依赖的干扰素调节因子激活物(DAI)的免疫学研究进展

DNA感受器是一类广泛表达于固有免疫细胞的模式识别受体(PRR),通过识别病原体或异常宿主细胞DNA激活相关炎症信号通路触发固有免疫应答。DNA依赖的干扰素调节因子激活物(DAI)是首个被发现的细胞质DNA感受器,在调控以干扰素诱导和程序性细胞死亡为特征的固有免疫应答中发挥重要作用。我们总结了DAI的分子特性,下游信号通路及其在抗感染免疫、肿瘤免疫和炎症性疾病中的作用及机制,并初步探讨了DAI与移植免疫的相关性,为临床治疗多种免疫性疾病提供新的靶点。     

AMPK通过抑制STING调节干扰素免疫应答通路的研究

目的探索腺苷酸活化蛋白激酶(AMPK)与cGAS-STING通路之间的联系及其在先天免疫中扮演的角色。方法利用CRISPR/Cas9技术、蛋白质印迹、RT-qPCR等方法,探究AMPK对DNA相关免疫通路的调控机制。结果在HT-DNA和cGAMP刺激下,AMPK-/-细胞株的IFN-β的表达量明显高于野生型细胞株,但这种变化在RNA信号通路中并不明显;激活AMPK可以抑制细胞内的DNA信号通路;在DNA信号通路中,AMPK-/-细胞株相较于野生型细胞株,STING在RNA和蛋白水平上都明显升高,即AMPK对cGAS-STING通路的抑制很可能是通过抑制STING起作用。结论AMPK在调节cGAS-STING介导的干扰素免疫应答中起重要作用。     

cGAS-cGAMP-STING信号通路的功能及研究进展

cGAS-cGAMP-STING信号通路是固有免疫系统重要组成部分,通过识别胞浆DNA诱导I型干扰素(interferons,IFNs)和其他细胞因子产生,介导抗微生物先天免疫,同时也在肿瘤进展及远处转移中发挥作用。深入了解cGAS-cGAMP-STING信号通路与炎症性疾病、自身免疫性疾病及肿瘤发生发展的关系,以及S...     

EB病毒感染中DNA识别通路的研究进展

EB病毒(Epstein-Barr virus, EBV)在人群中普遍易感, 其感染可累及血液、呼吸、泌尿、消化、神经等全身多个系统, 亦在相关肿瘤、自身免疫病等疾病发展中扮演重要角色, 严重威胁人类健康。作为一种DNA病毒, EBV可被固有免疫应答中的DNA识别受体感知, 触发下游一系列免疫应答。DNA识别通路由DNA感受器、接头分子及下游效应信号组成。双链DNA感受器主要包括黑色素瘤缺乏因子2样受体(absent in melanoma 2-like receptors, ALRs)、环状GMP-AMP合酶(cyclic GMP-AMP synthase, cGAS)等;接头分子主要是干扰素基因刺激因子(stimulator of interferon genes, STING)和含有caspase招募结构域的凋亡相关斑点样蛋白(apoptosis-associated speck-like protein containing a caspase recruitment domain, ASC);下游免疫效应主要包括Ⅰ型IFN、炎性小体及促炎细胞因子等。作为一种疱疹病毒科的双链D...     

DNA virus oncoprotein HPV18 E7 selectively antagonizes cGAS-STING-triggered innate immune activation

Cellular infections by DNA viruses trigger innate immune responses mediated by DNA sensors. The cyclic GMP–AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway has been identified as a DNA-sensing pathway that activates interferons in response to viral infection and, thus, mediates host defense against viruses. Previous studies have identified oncogenes E7 and E1A of the DNA tumor viruses, human papillomavirus 18 (HPV18) and adenovirus, respectively, as inhibitors of the cGAS-STING pathway. However, the function of STING in infected cells and the mechanism by which HPV18 E7 antagonizes STING-induced Interferon beta production remain unknown. We report that HPV18 E7 selectively antagonizes STING-triggered nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation but not IRF3 activation. HPV18 E7 binds to STING in a region critical for NF-κB activation and blocks the nuclear accumulation of p65. Moreover, E7 inhibition of STING-triggered NF-κB activation is related to HPV pathogenicity but not E7–Rb binding. HPV18 E7, severe acute respiratory syndrome coronavirus-2 open reading frame 3a, human immunodeficiency virus-2 viral protein X, and Kaposi's sarcoma-associated herpesvirus KSHV viral interferon regulatory factor 1 selectively inhibited STING-triggered NF-κB or IRF3 activation, suggesting a convergent evolution among these viruses toward antagonizing host innate immunity. Collectively, selective suppression of the cGAS-STING pathway by viral proteins is likely to be a key pathogenic determinant, making it a promising target for treating oncogenic virus-induced tumor diseases.     

Emerging role of the cGAS-STING signaling pathway in autoimmune diseases: Biologic function,mechanisms and clinical prospection

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS–STING) signaling pathway, as vital component of innate immune system, acts a vital role in distinguishing invasive pathogens and cytosolic DNA. Cytosolic DNA sensor cGAS first binds to cytosolic DNA and catalyzes synthesis of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), which is known as the second messenger. Next, cGAMP activates the adaptor protein STING, triggering a molecular chain reaction to stimulate cytokines including interferons (IFNs). Recently, many researches have revealed that the regulatory role of cGAS-STING signaling pathway in autoimmune diseases (AIDs) such as Rheumatoid arthritis (RA), Aicardi Goutières syndrome (AGS) and systemic lupus erythematosus (SLE). Moreover, accumulated evidence have showed inhibition of the cGAS-STING signaling pathway could remarkably suppress the joint swelling and inflammatory cell infiltration in RA mice. Therefore, in this review, we describe the molecular properties, biologic function and mechanisms of the cGAS-STING signaling pathway in AIDs. In addition, potential clinical applications especially selective small molecule inhibitors targeting the cGAS-STING signaling pathway are also discussed.     

Human plasmacytoid dendritic cells elicit a Type I Interferon response by sensing DNA via the cGAS‐STING signaling pathway

Plasmacytoid dendritic cells (pDCs) are a major source of type I interferon (IFN) and are important for host defense by sensing microbial DNA via TLR9. pDCs also play a critical role in the pathogenesis of IFN‐driven autoimmune diseases. Yet, this autoimmune reaction is caused by the recognition of self‐DNA and has been linked to TLR9‐independent pathways. Increasing evidence suggests that the cytosolic DNA receptor cyclic GMP‐AMP (cGAMP) synthase (cGAS) is a critical component in the detection of pathogens and contributes to autoimmune diseases. It has been shown that binding of DNA to cGAS results in the synthesis of cGAMP and the subsequent activation of the stimulator of interferon genes (STING) adaptor to induce IFNs. Our results show that the cGAS‐STING pathway is expressed and activated in human pDCs by cytosolic DNA leading to a robust type I IFN response. Direct activation of STING by cyclic dinucleotides including cGAMP also activated pDCs and knockdown of STING abolished this IFN response. These results suggest that pDCs sense cytosolic DNA and cyclic dinucleotides via the cGAS‐STING pathway and that targeting this pathway could be of therapeutic interest.     

Suppressive oligodeoxynucleotides containing TTAGGG motifs inhibit cGAS activation in human monocytes

Type I interferon (IFN) is a critical mediator of autoimmune diseases such as systemic lupus erythematosus (SLE) and Aicardi–Goutières Syndrome (AGS). The recently discovered cyclic‐GMP‐AMP (cGAMP) synthase (cGAS) induces the production of type I IFN in response to cytosolic DNA and is potentially linked to SLE and AGS. Suppressive oligodeoxynucleotides (ODN) containing repetitive TTAGGG motifs present in mammalian telomeres have proven useful in the treatment of autoimmune diseases including SLE. In this study, we demonstrate that the suppressive ODN A151 effectively inhibits activation of cGAS in response to cytosolic DNA, thereby inhibiting type I IFN production by human monocytes. In addition, A151 abrogated cGAS activation in response to endogenous accumulation of DNA using TREX1‐deficient monocytes. We demonstrate that A151 prevents cGAS activation in a manner that is competitive with DNA. This suppressive activity of A151 was dependent on both telomeric sequence and phosphorothioate backbone. To our knowledge this report presents the first cGAS inhibitor capable of blocking self‐DNA. Collectively, these findings might lead to the development of new therapeutics against IFN‐driven pathologies due to cGAS activation.     

Polyvalent design in the cGAS-STING pathway

Polyvalent interactions mediate the formation of higher-order macromolecular assemblies to improve the sensitivity, specificity, and temporal response of biological signals. In host defense, innate immune pathways recognize danger signals to alert host of insult or foreign invasion, while limiting aberrant activation from auto-immunity and cellular senescence. Of recent attention are the unique higher-order assemblies in the cGAS-STING pathway. Natural stimulation of cGAS enzymes by dsDNA induces phase separation and enzymatic activation for switchlike production of cGAMP. Subsequent binding of cGAMP to STING induces oligomerization of STING molecules, offering a scaffold for kinase assembly and signaling transduction. Additionally, the discovery of PC7A, a synthetic polymer which activates STING through a non-canonical biomolecular condensation, illustrates the engineering design of agonists by polyvalency principles. Herein, we discuss a mechanistic and functional comparison of natural and synthetic agonists to advance our understanding in STING signaling and highlight the principles of polyvalency in innate immune activation. The combination of exogenous cGAMP along with synthetic PC7A stimulation of STING offers a synergistic strategy in spatiotemporal orchestration of the immune milieu for a safe and effective immunotherapy against cancer.     

Camouflage and interception: how pathogens evade detection by intracellular nucleic acid sensors

Intracellular DNA and RNA sensors play a vital part in the innate immune response to viruses and other intracellular pathogens, causing the secretion of type I interferons, cytokines and chemokines from infected cells. Pathogen RNA can be detected by retinoic-acid inducible gene I-like receptors in the cytosol, whereas cytosolic DNA is recognized by DNA sensors such as cyclic GMP-AMP synthase (cGAS). The resulting local immune response, which is initiated within hours of infection, is able to eliminate many pathogens before they are able to establish an infection in the host. For this reason, all viruses, and some intracellular bacteria and protozoa, need to evade detection by nucleic acid sensors. Immune evasion strategies include the sequestration and modification of nucleic acids, and the inhibition or degradation of host factors involved in innate immune signalling. Large DNA viruses, such as herpesviruses, often use multiple viral proteins to inhibit signalling cascades at several different points; for instance herpes simplex virus 1 targets both DNA sensors cGAS and interferon-γ-inducible protein 16, as well as the adaptor protein STING (stimulator of interferon genes) and other signalling factors in the pathway. Viruses with a small genome encode only a few immunomodulatory proteins, but these are often multifunctional, such as the NS1 protein from influenza A virus, which inhibits RNA sensing in multiple ways. Intracellular bacteria and protozoa can also be detected by nucleic acid sensors. However, as the type I interferon response is not always beneficial for the host under these circumstances, some bacteria subvert, rather than evade, these signalling cascades for their own gain.     

miR-23a/b suppress cGAS-mediated innate and autoimmunity

Cyclic GMP-AMP synthase (cGAS), a key sensor of intracellular DNA, is essential for eliciting innate immunity against infection, whereas aberrant activation of cGAS by endogenous DNA promotes severe autoimmune diseases. However, it is largely unknown how cGAS expression is regulated during pathogen infection and autoimmunity. Here, we report that during herpes simplex virus type 1 (HSV-1) infection, two microRNAs (miR-23a and miR-23b) whose levels significantly decrease due to their interaction with the lncRNA Oasl2-209 directly regulate the expression of cGAS. Overexpression of miR-23a/b markedly dampens cytosolic DNA-induced innate immune responses, whereas inhibition of miR-23a/b enhances these responses. Mice treated with miR-23a/b agomirs exhibit increased susceptibility to HSV-1 infection. Moreover, cGAS is significantly upregulated in the Trex1^−/− mouse autoimmune disease model. Administration of miR-23a/b blunts self DNA-induced autoinflammatory responses in Trex1^−/− mice. Collectively, our study not only reveals a novel regulatory mechanism of cGAS expression by miRNAs but also identifies a potential therapy for cGAS-related autoimmune diseases.