(2020) support a cGAS-independent mechanism of STING activation by PERK in neurons during TBI. Of course, the activation of the cGAS-STING signal pathway is also determined by the dose and frequency of radiotherapy. . Herpes simplex virus 1 (HSV-1), which elicited cGAS-STING signalling, induced the activation of endogenous PERK in PMs, dynamically upstream of TBK1 activation (Fig. On the other hand, inactivation of cGAS signaling causes deficiency to. Notably, SAVI mutations and ER stress activate STING in a cGAS-independent manner. deed, recent studies in cGAS2/2 knockout animals showed the cGAS-independent STING activation by PC7A NP alone in mice Disclosures (13), although with a lesser magnitude compared with cGAMP. STING is an adaptor protein that is expressed in macrophages, dendritic cells (DCs), and lymphocytes, as well as endothelial and epithelial cells ().Macrophages, as major professional antigen-presenting cells (APCs), are best known for their ability to prime the host defense by engulfing foreign pathogens ().The DNA contained in pathogens would activate the cGAS-STING signal pathway of . The upstream dsDNA interacts with enzyme cGAS in a sequence-independent way [12, 13], promoting a conformational change of cGAS to catalyze the formation of 2′,3′-cyclic GMP-AMP (cGAMP), a cyclic dinucleotide . Several DNA viruses carrying dsDNA activate cGAS-STING signaling in in vitro and in vivo studies. IFN-β mRNA in HUVECs (A) or EA.hy926 endothelial cells (B) was measured by real-time qPCR 4 h after transfection of various DNA fragments (ISD90, HSV60, and E. coli DNA at 5 μg/mL) and cGAMP (5 μg/mL) with Lipofectamine 2000 (Life Technologies). find DDX41 regulates cGAS activation through unwinding and annealing activities on dsDNA and ssDNA, respectively, and MDS/AML patient mutant R525H causes overactivation of innate immune response due to its unbalanced activities. (FP) of IAV reportedly interacts with STING to antagonize type I IFN production in a STING-dependent but cGAS-independent manner 89. Using biochemical and genetic approaches (an anti-IL-6R antibody blockade, IL-6 knockout [KO], MyD88 KO or myeloid-specific p38 KO mice), we demonstrate that a blockade of the cGAS . Moreover, cGAS- or cGAMP-independent STING activation is conceivable. Our understanding of innate immune responses made a leap forward in 1989 when Charles A. Janeway Jr. proposed a system of non-clonal, germline encoded sensors which he deemed pattern recognition receptors (PRRs) []. Activation of STING signaling and viral evasion. In response to Brucella DNA, STING and the AIM2 inflammasome directly instigate caspase-1 activation and IL-1β secretion in macrophages in a cGAS-independent manner [59]. Activated STING translocates from the ER to the Golgi apparatus, where STING recruits and activates the kinase TBK1 that mediates the phosphorylation of IRF3 and NF-κB. This demonstrates that the function of STING during the response to nuclear DNA damage involves its non-canonical activation in a cGAS- and cGAMP-independent manner. Interestingly, A-T patient skin fibroblasts prematurely undergo cellular senescence and accumulate micronuclei in culture (Lan et al., 2019). in cGAS-STING pathway. However, it is not clear how STING is activated in this setting. The cGAS-STING signaling pathway was needed for IFN-β production induced by LGG in dendritic cells (DCs) (Table 2). . recent studies have revealed cGAS-STING activities that impact cells in unexpectedly diverse manners. While CGAS was originally found to be required for STING1 activation during viral infection, recent studies have also reported a CGAS-independent STING1 pathway in response to different Jo urn al Pre- pr of 13 stimuli, including virial infection (Holm et al., 2016; Suschak et al., 2016; Unterholzner and Dunphy, 2019). Activation of STING was independent of the cytosolic double stranded DNA sensor cGAS, and infection did not induce detectable release into the cytosol of either mitochondrial, nuclear or bacterial DNA-indicating DNA-independent activation of the STING pathway in S. pyogenes infected macrophages. Additionally, DNA/cGAS-independent mode of STING activation has also been characterized in the progression of several sterile inflammatory diseases. We show that cGAMP administration at 1 to 10 µg increased STING dimers, TBK1 phosphorylation (pTBK1),. S4 and S5). cGAMP acts as a second messenger, which can directly activate STING in the cGAS engaged cells (if present—in this schematic the cells with cytosolic DNA do not express STING). ture of canonical STING activation, sev-eral findings by Sen et al. Using gene targeting, RNA interference and inhibitors, we found that the innate immune response to Etoposide required STING but, unexpectedly, was independent of cGAS. During conventional DNA sensing, STING translocates from the ER to peri-nuclear foci and gets phosphorylated by TBK1 at Serine 366 ( Dobbs et al., 2015 , Liu et al., 2015 ). The MDS/AML-derived mutant R525H had reduced unwinding activities but retained normal strand . . 2, A and B, and figs. Activation of the innate immune system is a critical step in limiting viral infection. The released DNA can then be detected by cytosolic cGAS to result in cGAMP production. Considering that radiation-induced DNA damage needs cells mitotic progression for up to 24-72 h to accumulate into cytosol [], we hypothesized that synchronizing delivery of Mn 2+ into tumor with RT-induced accumulation of DNA damage by sustained-release of Mn 2+ may prime the antitumor . Additionally, tumor cells and MDSCs may impede STING signaling by upregulating Gal9 or via other . The initial finding of enhanced cGAS-STING activation in cells deficient for a prototype regulator of actin dynamics anticipates the importance of this layer of . DDX41 is required for the activation of cGAS and STING (A) cGAMP production detected by an ELISA kit (Cayman Chemical) in WT and DDX41 KO THP-1 macrophages 6 h post mock or indicated DNA stimulation. A cGAS-Independent STING/IRF7 Pathway Mediates the Immunogenicity of DNA Vaccines It has been known since the discovery of DNA vaccines >20 y ago that DNA vaccines can function as adjuvants. cGAS binds to both pathogen-derived and host organelle-derived DNA in the Despite cGAS nuclear translocation, neither approach induced an ISG response in wild-type (WT) cells (Fig. CDNs produced by cGAS bind to STING in the ER inducing a conformational change in the molecule that leads to relocation of STING and TBK1 to the perinuclear region of the cell resulting in activation ( 16 ). Tumor-derived DNA Although the function of cGAS-STING in protozoan infection has been characterized, little is known about the activation of this pathway in helminth infection. . in cGAS-STING pathway. Notably, HSV-1 infection. By recognizing host-derived DNA, cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activates endoplasmic reticulum-associated stimulator of interferon genes (STING), which leads to the induction of type I interferons and inflammatory cytokines or immunogenic cell death that promotes sterile inflammation. cGAS-independent STING activation in response to DNA damage Self-DNA has previously been thought to be protected from immune detection by compartmentalisation in the nucleus or mitochondria. Data show a representative result of two independent experiments. STING activation triggers several inflammatory pathways including IRF3 and NF-κB activation. Downstream from the BCR, Btk activation is a defining feature of the signaling induced by TI-2 antigens ( 1 ). Double-stranded DNA (dsDNA) sensor cyclic-GMP-AMP synthase (cGAS) along with the downstream stimulator of interferon genes (STING) acting as essential immune-surveillance mediators have become hot topics of research. cGAS is activated by dsDNA. It has been detected that the activation of cGAS-STING is usually impaired in multiple cancers by epigenetic hypermethylation [46]. Mitochondrial distress-induced cGAS/STING activation was identified as a significant mechanism underlying macrophage hyperactivation and exacerbated inflammapathology. Mock (no DNA) was set as 1. cGAS KO cells serve as a negative control. Thus, STING may also play an evolutionarily important role in protecting the host against microbial infection. The cGAS-STING pathway is a component of the innate immune system that functions to detect cytosolic DNA and, upon activation of STING, results in the production of type 1 interferons [56].. Independent of enhanced anti-cancer immunity, cGAS-STING pathway could directly activate senescence and apoptosis signaling pathways in cancer cells [51, 52]. Our recent study reported the involvement of Aim2 as the sensor of DNA vaccines in eliciting Ag-specific Ab responses. While CGAS was originally found to be required for STING1 activation during viral infection, recent studies have also reported a CGAS-independent STING1 pathway in response to different Jo urn al Pre- pr of 13 stimuli, including virial infection (Holm et al., 2016; Suschak et al., 2016; Unterholzner and Dunphy, 2019). The activated cGAS-STING signal pathway would induce interferon (IFN) production to promote DCs maturation and activation, which mediated CD8 + T cells activation to provide tumor regression ( 43, 60 - 62 ). STING signalling contributes to the pathology in Niemann-Pick disease type C independent of cGAS- and cGAMP Summary: Scientists at the University of Texas Southwestern Medical Center in Dallas, Texas, uncovered a cGAS- and cGAMP-independent mode of STING activation as the driver of Niemann-Pick disease type C (NPC1). . Although the authors did not mea-sure cytosolic DNA or cGAMP levels to definitively exclude the involvement of cGAS, they found that STING was acti-vated selectively in neurons and . KSHV primary infection can activate a STING-cGAS-dependent IFN-β response. 114, 115 Interestingly, the activation of cGAS-STING signaling pathway can also be observed in other 5 A and B). cGas is a nucleotidyl transferase enzyme which catalyzes the conversion of ATP and GTP into a novel cyclic dinucleotide, cGMP-AMP (cGAMP) which in turn binds and activates Sting. Hansen AL, Jensen SK, Sun C, Thomsen MK et al (2016) Influenza A virus targets a cGAS-independent STING pathway that controls enveloped RNA viruses. Recently, evidence has shown that self-DNA release and cGAS-STING pathway over-activation can drive lung disease, making this pathway a promising therapeutic target for inflammatory lung disease. Kubarenko AV, Andreeva L, Hopfner KP, Hornung V (2014) Cytosolic RNA: DNA hybrids activate the cGAS-STING axis. There are two primary disease scenarios that could benefit from modulation: activation or inhibition of cGAS-STING, namely cancer and diseases with pathogenesis attributed to increased inflammatory. To investigate whether VZV ORFs block cGAS/STING activation, we utilised a luciferase-based screening platform in HEK293T cells. To cite this article: Leonie Unterholzner & Gillian Dunphy (2019): cGAS-independent STING activation in response to DNA damage, Molecular & Cellular Oncology, DOI: 10.1080/23723556.2018.1558682 Activation of cGAS occurs with viruses that infect through different high-affinity receptors (CAR, CD46, and desmoglein-2), and the magnitude of the cGAS/STING DNA response cascade is influenced . The cGAS-STING signaling pathway, comprising the cyclic GMP-AMP synthase (cGAS) and the cyclic GMP-AMP receptor stimulator of interferon genes (STING), is an evolutionarily conserved defense. RAW cGAS and STING knockout cells infected with B. thailandensis had significantly less cell death as compared to B. thailandensis-infected wild-type cells (Fig. In contrast, a recent study revealed that cGAS protects the liver from IR injury in a STING-independent manner (Lei et al., 2018). The cGAS-independent activation of STING that we observe after etoposide-induced damage appears to . . In concordance with the crucial role for cGAS and STING in NLRP3 activation, direct activation of STING by the endogenous second messenger cGAMP led to STING-and NLRP3-dependent, but cGAS . cGAS activation by G3BP1 is independent of stress granule assembly. Email. Interferon stimulated genes (ISGs) can be induced independent of the interferons known to mediate this response, or the upstream regulator protein STING. Ten independent reconstructions were averaged to generate a representative model with the program DAMAVER 59 In addition, . The activation of DNA-PK by free DNA ends leads to STING-independent IRF3 phosphorylation and type I IFN production . However . . including Drosophila melanogaster (26, 45). These DNA viruses include adenovirus, 62 vaccinia virus, 34 African swine fever viruses 63 and herpesviruses such as cytomegalovirus, 64, . These DNA viruses include adenovirus, 62 vaccinia virus, 34 African swine fever viruses 63 and herpesviruses such as cytomegalovirus, 64, . cGAS-STING pathway downregulates the expression of anti-apoptosis protein BCL2 and upregulates the abundance of pro-apoptosis protein BCL2-associated X (BAX) . 2, C and D). Enter the email address you signed up with and we'll email you a reset link. 7 We also did not detect any production of the second messenger cGAMP in Etoposide-treated cells, or the classical signs of STING activation such as its translocation to peri . Independent of intracellular STING activation, cGAMP can transfer to adjacent . By contrast, in BAF-KD cells, mechanical compression elicited cGAS-STING pathway activation, as revealed by robust IRF3 activation (Fig. Thus, the STING-independent function of cGAS in suppressing genomic instability contributes to cell viability after radiation and chemotherapy, and it may be . More recently, it was reported that ATM inhibition could activate a type 1 IFN response in pancreatic tumor cells that could enhance ICB therapy in a cGAS/STING-independent manner . helps cGAS in the activation of STING during cytosolic DNA recognition in human cells.8,9 However, even though IFI16 is also involved in conventional cytosolic DNA sensing, it promotes a different mode of STING activation after Etoposide-induced damage. In addition to genetic and cytological consequences, mitotic errors induce inflammation and immunosurveillance through the activation of the viral DNA sensor cyclic GMP-AMP synthase (cGAS) (13, 14).Upon binding to DNA, cGAS synthesizes 2′3'-cyclic GMP-AMP (cGAMP) which in turn activates STING followed by TBK1 and IRF3, ultimately leading to induction of type I interferon (IFN) expression . In this light, it is worth noting that many RNA . cGAS-STING pathway in DC In tumor microenvironment, cGAS-STING in DC plays an important role in the cross-presentation and priming of tumor-specific CD8+ Tcell(Fig.2). K) ISRE reporter activation in THP1-Dual-CAS9 cells treated with 10uM cGAS inhibitor (G140) or DMSO and stimulated with 2.5ug/ml ISD (+ Lipofectamin LTX plus), 5ug/ml R848 or 50uM cGAMP. Activation of STING was independent of the cytosolic double stranded DNA sensor cGAS, and infection did not induce detectable release into the cytosol of either mitochondrial, nuclear or bacterial DNA-indicating DNA-independent activation of the STING pathway in S. pyogenes infected macrophages. In addition to the classic cGAS/STING-IFN axis (Fig. Immunoprecipitation . The cGAS-STING pathway relies on two independent receptors. The cGAS-STING pathway was discovered as an important DNA-sensing machinery in innate immunity and viral defense. The data from one of three independent experiments are expressed as means ± SD. The recombinant DDX41 protein exhibited ATP-dependent DNA unwinding activity and ATP-independent strand annealing activity. Thus, the control of cGAS activity against nuclear self . Nat Commun 7: 10680 Crossref CAS PubMed Web of Science . Often the effect of STING signaling is mediated by IFN-β, but can also be independent of type I IFNs, for example by upregulation of SOCS1 which hampers STAT3 phosphorylation. The capacity of cGAS to initiate STING activation by eCDNs prompted us to investigate whether cGAS directly senses endocytosed eCDNs. In this work, we investigated whether Natterin activates mitochondrial damage, resulting in self-DNA leaks into the cytosol, and whether the DNA sensor cGAS and STING pathway participate in triggering the innate immune response. However, the molecular mechanisms involved in the above studies, especially those responsible for triggering spontaneous activation of the type 1 IFN response in . Taken together, these results establish the engagement of the cGAS-cGAMP-STING axis by flavine in human and mouse cells, through cytoplasmic leakage of DNA products. This DDX41-cGAS-STING pathway may be related to molecular pathogenesis of MDS/AML. For example, the checkpoint kinase ATM can activate STING in response to etoposide-induced DNA damage independently of cGAS, stimulating NF-κB-dependent gene expression . L) Immunoblot against cGAS and STING in NHDF-NT, NHDF-cGAS KO and NHDF-STING KO pools × Close Log In. cGAS-STING pathway in DC In tumor microenvironment, cGAS-STING in DC plays an important role in the cross-presentation and priming of tumor-specific CD8+ Tcell(Fig.2). cGAS is an enzyme with a positively charged surface that recognizes, preferentially, B-form dsDNA to synthesize cGAMP. In human monocytes and keratinocytes, STING activation by cGAS requires the cooperation with the DNA binding protein IFI16 (interferon-γ-inducible factor 16), which shuttles between the nucleus and the cytosol but is nuclear at steady state . cGAS activation by G3BP1 is independent of stress granule assembly. Several DNA viruses carrying dsDNA activate cGAS-STING signaling in in vitro and in vivo studies. 2c ). 128 . or reset password. The relative amount . The authors have no financial conflicts of interest. An important unanswered question . STING is an adaptor protein that is expressed in macrophages, dendritic cells (DCs), and lymphocytes, as well as endothelial and epithelial cells ().Macrophages, as major professional antigen-presenting cells (APCs), are best known for their ability to prime the host defense by engulfing foreign pathogens ().The DNA contained in pathogens would activate the cGAS-STING signal pathway of . Singh et al. Upon DNA binding, cGAS produces the second messenger cGAMP (cyclic guanosine monophosphate adenosine monophosphate), which activates the adaptor protein STING (STimulator of INterferon Genes, also known as transmembrane protein 173, TMEM173). EMBO J 33(24):2937-2946. Recent advances have now expanded the roles of cGAS-STING to cancer. The activation of cGAS-STING signaling results in the late production of IL-6 (at day four p.i. However, it is unclear what activates STING in this setting . Innate immune signaling and the cGAS-STING pathway. a mRNA expression levels of cGAS (grey bars) and STING (black bars) in different cancer cell lines. The cGAS-STING axis has been implicated in sensing Leishmania donovani DNA and activating the innate cytosolic surveillance pathway to promote parasite survival . Noncanonical STING signaling in response to etoposide-induced DNA damage could be activated by DNA-repair . The intrinsic function of the cGAS-STING pathway facilitates type-I interferon (IFN) inflammatory signaling responses and other cellular processes such as autophagy, cell survival . Overview of cGAS activation and cGAS-STING signaling. cGAS‐STING pathway activator enhances the inhibitory effect of irradiation on NSCLC cells According to a previous study, 8 the small molecule diABZI was able to activate the cGAS‐STING pathway. Investigation of the effects of TBI on cGAS/STING activation, IFN-I signaling and neuroinflammation in young and aged C57Bl/6 male mice confirmed activation of key neuroinflammatory pathways in biochemical studies and indicated a mechanistic link between microglial-associated neuro inflammation and neurodegeneration in the aged TBI brain. This is potentially . for helpful discussion. Hence, we examined the possibility of cell death in bacterial-induced fused cells. In this study, we evaluated the role of Mn 2+ on the activation of cGAS-STING pathway combining with RT. [N67C]), which is closely associated with the sensitive phenotype. Subsequently, nuclear translocation of IRF3 and NF-κB induces the expression of type I . Highly aggressive, unstable . Due to the limited number of studies, it is still unclear how the cGAS/STING pathway regulates the interplay between hepatocytes and macrophages during sterile inflammatory injury in the liver. Hyperactivation of cGAS signaling contributes to autoimmune diseases but serves as an adjuvant for anticancer immune therapy. Among these, cyclic GMP-AMP synthase (cGas) is a powerful activator of the Sting/Tbk1 pathway, providing a strong candidate for the unknown DNA vaccine sensor. Conversely, DMXAA stimulation significantly induced expression of the L929 ISRE-reporter cells, in line with direct activation of mouse Sting (Figure 4D and E). Unexpectedly, cGAS and STING activation were affected in DDX41 KO cells, suggesting that DDX41 functions upstream of cGAS. cGAS-independent roles of STING during RNA virus infection have also been reported. ISG induction upon fractionated irradiation occurs independent of STING, IFN-β or IFN-λ. Password. 6 cGAS-STING activation has been reported to lead to various modes of cell death (51-55). In the classic Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) pathway, downstream signals can control the production of type I interferon and nuclear factor kappa-light-chain-enhancer of activated B cells to promote the activation of pro-inflammatory molecules, which are mainly induced during antiviral responses. Here, we review recent advances on the cGAS-STING pathway governing self-DNA sensing, highlighting its role in pulmonary disease. Thus, chronic cGAS-STING activation may promote tumor metastasis which needs to be overcome. or. Tumor-derived DNA This review focuses on the molecular mechanism of cGAS-dependent and cGAS-independent STING signaling under various disease conditions, particularly highlighting the diverse initiators upon this . CAS PubMed PubMed Central Google Scholar . A cGAS-independent role of STING has been observed during RNA virus infection. 1), study has revealed that cGAS interacted with Beclin-1 to trigger autophagy, which would reduce cGAMP production independent of STING activation [].Similarly, activation of STING could be achieved in a cGAS-independent manner. In- N.Y., J.G., and Z.C. Remember me on this computer. The detection of DNA damage in the nucleus induces AbstractThe recognition of DNA as an immune-stimulatory molecule is an evolutionarily conserved mechanism to initiate rapid innate immune responses against microbial pathogens. Conversely, . MAVS- and cGAS-deficient B cells failed to fully up-regulate activation markers in response to anti-IgM ( Fig. Bars, 100 μm. Streptococcal M protein promotes IL-10 production by cGAS-independent activation of the STING signaling pathway . We thus used diABZI to reinforce the activation of cGAS‐STING pathway and then investigate its inhibitory effect of irradiation on NSCLC cells. cGAS usually detects cytosolic DNA during infection with intracellular pathogens. The activation of cGAS or STING within T and B lymphocytes can slow down proliferation or trigger apoptosis (30, 35, 36). This results in activation of the cGAS-STING pathway (Dou et al., 2017), a cytosolic DNA sensing signalling response that plays essential roles in activating pro-inflammatory genes (Barber, 2015). Expand For example, several instances of STING-mediated induction of programed cell death have been reported40-49 Figure 1. 128 . 4A ); these findings are consistent with MAVS and cGAS activation induced by BCR signaling. Log in with Facebook Log in with Google. STING signalling contributes to the pathology in Niemann-Pick disease type C independent of cGAS- and cGAMP Summary: Scientists at the University of Texas Southwestern Medical Center in Dallas, Texas, uncovered a cGAS- and cGAMP-independent mode of STING activation as the driver of Niemann-Pick disease type C (NPC1). It has been detected that the activation of cGAS-STING is usually impaired in multiple cancers by epigenetic hypermethylation [46]. On one hand, activation of the cGAS-STING pathway promotes antitumor immunity, although some cancers escape this immunity by deactivating the cGAS-STING pathway . During intracellular bacterial infections, activation of STING can be accomplished via two different mechanisms. Activation of STING was independent of the cytosolic double stranded DNA sensor cGAS, and infection did not induce detectable release into the cytosol of either mitochondrial, nuclear or bacterial DNA-indicating DNA-independent activation of the STING pathway in S. pyogenes infected macrophages. To further substantiate the telomere-related disease exacerbation, we also .