ABSTRACT
cGAS-STING signaling is a significant component of the innate immune system and functions as a vital sentinel mechanism to monitor cellular and tissue aberrations in microbial invasion and organ injury. cGAS, a cytosolic DNA sensor, is specialized in recognizing abnormally localized cytoplasmic double-stranded DNA (dsDNA) and catalytically synthesizes the second messenger cyclic-GMP-AMP (cGAMP), which initiates a cascade of type I interferon and inflammatory responses mediated by STING. Micronucleus, a byproduct of chromosomal missegregation during anaphase, are also significant contributors to cytoplasmic dsDNA. These unstable subcellular structures are susceptible to irreversible nuclear envelope rupture, exposing genomic dsDNA to the cytoplasm, which potently recruits cGAS and activates STING-mediated innate immune signaling and its downstream activities, including type I interferon and classical nuclear factor-κB (NF-κB) signaling pathways lead to senescence, apoptosis, autophagy activating anti-cancer immunity or directly killing tumor cells. However, sustained STING activation-induced endoplasmic reticulum stress, activated chronic type I interferon and nonclassical NF-κB signaling pathways remodel immunosuppressive tumor microenvironment, leading to immune evasion and facilitating tumor metastasis. Therefore, activated cGAS-STING signaling plays a dual role of suppressing or facilitating tumor growth in tumorigenesis and therapy. This review elaborates on research advances in mechanisms of micronucleus inducing activation of cGAS-STING signaling and its implications in tumorigenesis and therapeutic strategies of malignant tumors.
ABSTRACT
Epstein-Barr virus (EBV) is generally susceptible in human beings and multi-organ systems can be involved in EBV infection, such as blood, respiratory, urinary, digestive and nervous systems. EBV infection also plays an important role in the pathogenesis of related tumors, autoimmune diseases and other diseases, posing a great threat to human health. As a DNA virus, EBV can be sensed by DNA recognition receptors to trigger a series of downstream immune responses. A DNA-sensing pathway consists of DNA sensors, adaptor molecules and downstream effector signals. Double-stranded DNA sensors mainly include absent in melanoma 2-like receptors (ALRs) and cyclic GMP-AMP synthase (cGAS). Adaptors were mainly stimulator of interferon genes (STING) and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC). Downstream immune responses mainly involve typeⅠIFN, inflammasomes and proinflammatory cytokines. As a double-stranded DNA virus of the Herpesviridae family, EBV triggers complex innate and adaptive immune responses in the host, especially the sensing pathways mediated by a variety of DNA recognition receptors, which play a key role in host immune defense and pathogen immune evasion. This review made the DNA sensor as the clue to comprehensively summarize the progress in the activation, regulatory mechanism and clinical relevance of DNA-sensing pathways in EBV infection in recent years, aiming to achieve a better understanding of the host innate immune responses during EBV infection and provide an immunological basis for the prevention and treatment of EBV infection-related diseases.
ABSTRACT
The cGAS-STING signaling pathway is one of the main pathways of immune defense against many types of pathogens. cGAS catalyzes the production of the second messenger cGAMP (cyclic GMP-tVMP) by recognizing plasma DNA and cGAMP subsequently binds to the interferon gene stimulating factor (STING). The pathway induces the production of type I interferon (IFN-I) and activates the innate immune system. The activation of the cGAS-STI]NG pathway could facilitate self-protection,thus STI]NG agonists for tumor immunotherapy have attracted much attention in recent years,and several drug candidates have been in clinical trials. Meanwhile,aberrant activation of cGAS-STI]NG could lead to autoimmune diseases and has attracted extensive interest in developing its inhibitors. This paper summarizes the mechanism and regulatory sites of the cGAS-STI]NG pathway,and outlines the research progress of cGAS-STING pathway-related immune and inflammatory diseases and its inhibitors.
ABSTRACT
Objective To investigate whether cyclic GMP-AMP synthase ( cGAS ) , a cytosolic DNA sensor, could recognize the reverse transcription intermediate and induce the subsequent signaling path-way during the infection of human T cell leukemia virus type 1 ( HTLV-1 ) . Methods Biotin-labeled ssDNA90, a reverse transcription intermediate of HTLV-1, was transfected into HeLa cells and the interac-tion between it and cGAS was detected by co-immunoprecipitation experiments. HeLa cells were co-cultured with HTLV-1-positive MT2 cells and the interaction between cGAS and stimulator of interferon genes ( STING) was analyzed by co-immunoprecipitation experiments. The expression of STING in HeLa cells was silenced by siRNA. cGAS was transfected into the HeLa cells 24 h after the silencing and after 24 h, these cells were co-cultured with MT2 cells for another 24 h. Real-time PCR assay was used to measure the ex-pression of IFN-β, RANTES ( regulated upon activation, normal T-cell expressed, and secreted) , TNF-α, HTLV-1 protein Tax, p19 and HBZ. Immunoblot assay was performed to evaluate the phosphorylation of IRF3 and p65 in HeLa cells. Results cGAS interacted with ssDNA90. cGAS interacted with STING in the cytoplasm. In STING-silenced HeLa cells, cGAS transfection had no influence on the expression of IFN-β, RANTES , TNF-α, Tax , p19 or HBZ , nor did it affect the phosphorylation of IRF3 or p65 . Conclusions cGAS interacted with HTLV-1 RTI ssDNA90 and activated STING-dependent innate immune responses.
ABSTRACT
Innate immune system rapidly detects and responds to viruses at the early stage of viral infection. However,the mechanisms by which the immune system recognizes and eliminates them have not been fully clarified so far. Studies have shown that receptors are the primary tool for cell recognition and detection of viruses, and cyclic GMP-AMP synthase(cGAS)is one of the newly found DNA recognition receptors. cGAS transmits the signal to the downstream protein called STING(stimulator of interferon genes)and mediates the production of type I interferon(IFN-I),thereby to initiates the antiviral immunity of cells. This review briefly introduces the mechanism of the cGAS-STING signaling pathway, in order to provide a theoretical basis for the research and development of new antiviral drugs.
ABSTRACT
<p><b>OBJECTIVE</b>This work aims to determine the effect of cytosolic bacteria on the expression of cyclic GMP-AMP synthase (cGAS) in human periodontal ligament cells (hPDLCs) and gingival tissues.</p><p><b>METHODS</b>The ability of Porphyromonas gingivalis (P. gingivalis) to invade hPDLCs was detected using laser scanning confocal microscope assay at a multiplicity of infection of 10. P. gingivalis-infected cells were sorted by fluorescence-activated cell sorting (FACS). Then, quantitative real time reverse transcription polymerase chain reaction (qRT-PCR) and Western blot were used to detect cGAS expression in infected cells. Finally, the location and expression of cGAS in inflammatory and normal gingival tissues were investigated by immunohistochemistry.</p><p><b>RESULTS</b>P. gingivalis actively invaded hPDLCs. Moreover, cGAS expression significantly increased in P. gingivalis-infected cells. Although cGAS was expressed in the epithelial and subepithelial cells of both inflamed and normal gingival tissues, cGAS expression significantly increased in inflamed gingival tissues.</p><p><b>CONCLUSIONS</b>Cytosolic bacteria can upregulate cGAS expression in infected cells. These data suggest that cGAS may act as pattern-recognition receptors and participate in recognizing cytosolic nucleic acid pathogen-associated molecular patterns. .</p>
Subject(s)
Humans , Blotting, Western , Cells, Cultured , Flow Cytometry , Gingiva , Nucleotides, Cyclic , Periodontal Ligament , Porphyromonas gingivalis , Real-Time Polymerase Chain ReactionABSTRACT
Objective To investigate the function and the possible mechanism of cyclic GMP-AMP synthase (cGAS), a DNA sensor, in HeLa cells during human T cell leukemia virus type 1 (HTLV-1) in-fection.Methods HeLa cells were co-cultured with MT2 cells (HTLV-1-positive T cells) and then detec-ted by immunoblot assay to analyze the changes in the expression of cGAS .A hemagglutinin ( HA)-tagged cGAS plasmid was constructed and transfected into HeLa cells .Twenty-four hours after transfection , these cells were co-cultured with MT2 cells for another 24 hours.Immunoblot assay was used to detect the expres-sion of HTLV-1 proteins Tax and p19.Real-time PCR was performed to measure the expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level .Immunoblot assay was also used to analyze the phosphorylation of interferon regulatory factor 3 (IRF3) and p65.Expression of interferon (IFN)-β, IFN-gamma-inducible protein 10 ( IP-10 ) , RANTES ( regulated on activation , normal T cell expressed and secreted ) and tumor necrosis factor (TNF)-αwas detected by real-time PCR assay.Results Expression of cGAS was enhanced in HeLa cells after co-cultured with MT2 cells.Compared with control cells , the HeLa cells that were trans-fected with cGAS plasmid showed lower levels of Tax and p 19 proteins, suppressed expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level , enhanced phosphorylation of IRF 3 and p65, and higher levels of IFN-β, IP-10, RANTES and TNF-αafter co-cultured with MT2 cells.Conclusion cGAS might promote the innate immune response and inhibit HTLV-1 replication in HTLV-1-infected HeLa cells .