Activation Of Stimulator Of Interferon Genes Research Articles

Targeting STING oligomerization with small-molecule inhibitors.

Stimulator of interferon genes (STING) is an essential adaptor protein required for the inflammatory response to cytosolic DNA. dsDNA activates cGAS to generate cGAMP, which binds and activates STING triggering a conformational change, oligomerization, and the IRF3- and NFκB-dependent transcription of type I Interferons (IFNs) and inflammatory cytokines, as well as the activation of autophagy. Aberrant activation of STING is now linked to a growing number of both rare as well as common chronic inflammatory diseases. Here, we identify and characterize a potent small-molecule inhibitor of STING. This compound, BB-Cl-amidine inhibits STING signaling and production of type I IFNs, IFN-stimulated genes (ISGs) and NFκB-dependent cytokines, but not other pattern recognition receptors. In vivo, BB-Cl-amidine alleviated pathology resulting from accrual of cytosolic DNA in Trex-1 mutant mice. Mechanistically BB-Cl-amidine inhibited STING oligomerization through modification of Cys148. Collectively, our work uncovers an approach to inhibit STING activation and highlights the potential of this strategy for the treatment of STING-driven inflammatory diseases.

MEF2A suppresses stress responses that trigger DDX41-dependent IFN production

Cellular stress in the form of disrupted transcription, loss of organelle integrity, or damage to nucleic acids can elicit inflammatory responses by activating signaling cascades canonically tasked with controlling pathogen infections. These stressors must be kept in check to prevent unscheduled activation of interferon, which contributes to autoinflammation. This study examines the role of the transcription factor myocyte enhancing factor 2A (MEF2A) in setting the threshold of transcriptional stress responses to prevent R-loop accumulation. Increases in R-loops lead to the induction of interferon and inflammatory responses in a DEAD-box helicase 41 (DDX41)-, cyclic GMP-AMP synthase (cGAS)-, and stimulator of interferon genes (STING)-dependent manner. The loss of MEF2A results in the activation of ATM and RAD3-related (ATR) kinase, which is also necessary for the activation of STING. This study identifies the role of MEF2A in sustaining transcriptional homeostasis and highlights the role of ATR in positively regulating R-loop-associated inflammatory responses.

STING strengthens host anti-hantaviral immunity through an interferon-independent pathway

Hantaan virus (HTNV), the prototype virus of hantavirus, could escape innate immunity by restraining type I interferon (IFN) responses. It is largely unknown whether there existed other efficient anti-hantaviral tactics in host cells. Here, we demonstrate that the stimulator of interferon genes (STING) strengthens the host IFN-independent anti-hantaviral immunity. HTNV infection activates RIG-I through IRE1-XBP 1-mediated ER stress, which further facilitates the subcellular translocation and activation of STING. During this process, STING triggers cellular autophagy by interacting with Rab7A, thus restricting viral replication. To note, the anti-hantaviral effects of STING are independent of canonical IFN signaling. Additionally, neither application of the pharmacological antagonist nor the agonist targeting STING could improve the outcomes of nude mice post HTNV challenge in vivo. However, the administration of plasmids exogenously expressing the mutant C-terminal tail (ΔCTT) STING, which would not trigger the type I IFN responses, protected the nude mice from lethal HTNV infection. In summary, our research revealed a novel antiviral pathway through the RIG-I-STING-autophagy pathway, which offered novel therapeutic strategies against hantavirus infection.

The Many Ways to Deal with STING.

The stimulator of interferon genes (STING) is an adaptor protein involved in the activation of IFN-β and many other genes associated with the immune response activation in vertebrates. STING induction has gained attention from different angles such as the potential to trigger an early immune response against different signs of infection and cell damage, or to be used as an adjuvant in cancer immune treatments. Pharmacological control of aberrant STING activation can be used to mitigate the pathology of some autoimmune diseases. The STING structure has a well-defined ligand binding site that can harbor natural ligands such as specific purine cyclic di-nucleotides (CDN). In addition to a canonical stimulation by CDNs, other non-canonical stimuli have also been described, whose exact mechanism has not been well defined. Understanding the molecular insights underlying the activation of STING is important to realize the different angles that need to be considered when designing new STING-binding molecules as therapeutic drugs since STING acts as a versatile platform for immune modulators. This review analyzes the different determinants of STING regulation from the structural, molecular, and cell biology points of view.

Induction of Inflammation Disrupts the Negative Interplay between STING and S1P Axis That Is Observed during Physiological Conditions in the Lung.

The stimulator of interferon genes (STING) is a master regulator of innate immunity, involved in several inflammatory diseases. Our previous data showed that sphingosine-1-phosphate (S1P) is released during inflammatory conditions in the lung. The aim of this study was to understand the interplay between S1P and STING during both physiological and pathological conditions. The mRNA levels of ceramidase (ASAH1), S1P precursor enzyme, and STING were inversely correlated in healthy lung tissues, but positively correlated in tumor tissues. The activation of STING induced higher expression of ASAH1 and was accompanied by IFN-β and IL-6 release. ASAH1 and sphingosine kinases (SPHK I/II) blockade significantly reduced IL-6, but not IFNβ, after STING activation. In support of this, taking advantage of a mouse model, we found that inflamed lungs had higher levels of inactive ASAH1 when STING was inhibited. This confirmed the human data, where higher levels of STING promoted the activation of ASAH1. Lung cancer patients positive to STING and ASAH1 mRNA levels had a dismal prognosis in that the overall survival was reduced compared to STING/ASAH1 negative patients. These data highlight that during physiological conditions, STING and the S1P axis do not interfere, whereas in lung cancer patients their interplay is associated to poor prognosis.

Role of stimulator of interferon genes (STING) in the enteric nervous system in health and disease.

Stimulator of Interferon Genes (STING) is a crucial protein that controls the immune system's reaction to bacterial and viral infections. As a pattern-recognition receptor, STING is found in immune cells as well as in neurons and glia in the enteric nervous system (ENS). Recent studies have linked STING to the pathogenesis of several neurological disorders like multiple sclerosis (MS), Alzheimer's disease (AD), and gastrointestinal disorders, including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), which are characterized by chronic inflammation and dysregulation of the enteric nervous system (ENS) in the digestive tract. STING plays a crucial role in the pathway that induces the production of interferon in response to viral infection in the central nervous system (CNS). A new study by Dharshika et al. in the current issue of Neurogastroenterology and Motility has demonstrated distinct roles for STING in enteric neurons and glia, namely activation of STING leads to IFN-β production in enteric neurons but not in glia and reducing STING activation in enteric glia does not modulate the severity of Dextran sulfate sodium (DSS) colitis or subsequent loss of enteric neurons. Rather, the role of STING in enteric glia is related to enhancing autophagy. STING can influence gastrointestinal motility and barrier function and therefore be involved in the pathophysiology of IBS and IBD. This mini review highlights the current knowledge of STING in the pathophysiology of CNS and gastrointestinal diseases as well as these newly uncovered roles STING in enteric neurons and glia.

STAT2 hinders STING intracellular trafficking and reshapes its activation in response to DNA damage

In cancer cells, endogenous or therapy-induced DNA damage leads to the abnormal presence of DNA in the cytoplasm, which triggers the activation of cGAS (cyclic GMP-AMP synthase) and STING (stimulator of interferon genes). STAT2 suppresses the cGAMP-induced expression of IRF3-dependent genes by binding to STING, blocking its intracellular trafficking, which is essential for the full response to STING activation. STAT2 reshapes STING signaling by inhibiting the induction of IRF3-dependent, but not NF-κB-dependent genes. This noncanonical activity of STAT2 is regulated independently of its tyrosine phosphorylation but does depend on the phosphorylation of threonine 404, which promotes the formation of a STAT2:STING complex that keeps STING bound to the endoplasmic reticulum (ER) and increases resistance to DNA damage. We conclude that STAT2 is a key negative intracellular regulator of STING, a function that is quite distinct from its function as a transcription factor.

STING-dependent interferon signatures restrict osteoclast differentiation and bone loss in mice

Stimulator of interferon genes (STING) is a key mediator of type-I interferon (IFN-I) signaling in response to a variety of stimuli, but the contribution of STING to homeostatic processes is not fully characterized. Previous studies showed that ligand activation of STING limits osteoclast differentiation invitro through the induction of IFNβ and IFN-I interferon-stimulated genes (ISGs). In a disease model (SAVI) driven by the V154M gain-of-function mutation in STING, fewer osteoclasts form from SAVI precursors in response to receptor activator of NF-kappaB ligand (RANKL) in an IFN-I-dependent manner. Due to the described role of STING-mediated regulation of osteoclastogenesis in activation settings, we sought to determine whether basal STING signaling contributes to bone homeostasis, an unexplored area. Using whole-body and myeloid-specific deficiency, we show that STING signaling prevents trabecular bone loss in mice over time and that myeloid-restricted STING activity is sufficient for this effect. STING-deficient osteoclast precursors differentiate with greater efficiency than wild types. RNA sequencing of wild-type and STING-deficient osteoclast precursor cells and differentiating osteoclasts reveals unique clusters of ISGs including a previously undescribed ISG set expressed in RANKL naïve precursors (tonic expression) and down-regulated during differentiation. We identify a 50 gene tonic ISG signature that is STING dependent and shapes osteoclast differentiation. From this list, we identify interferon-stimulated gene 15 (ISG15) as a tonic STING-regulated ISG that limits osteoclast formation. Thus, STING is an important upstream regulator of tonic IFN-I signatures shaping the commitment to osteoclast fates, providing evidence for a nuanced and unique role for this pathway in bone homeostasis.

Discovery of podofilox as a potent cGAMP-STING signaling enhancer with antitumor activity.

Cyclic GMP-AMP (cGAMP) is a second messenger that activates the stimulator of interferon genes (STING) innate immune pathway to induce the expression of type I interferons (IFNs) and other cytokines. Pharmacological activation of STING is considered a potent therapeutic strategy in cancer. In this study, we employed a cell-based phenotypic screen and identified podophyllotoxin (podofilox), a microtubule destabilizer, as a robust enhancer of the cGAMP-STING signaling pathway. We found that podofilox enhanced the cGAMP-mediated immune response by increasing STING-containing membrane puncta and the extent of STING oligomerization. Furthermore, podofilox changed the trafficking pattern of STING and delayed trafficking-mediated STING degradation. Importantly, the combination of cGAMP and podofilox had profound antitumor effects on mice by activating the immune response through host STING signaling. Together, these data provide insights into the regulation of cGAMP-STING pathway activation and demonstrate what we believe to be a novel approach for modulating this pathway and thereby promoting antitumor immunity.

GPR162 activates STING dependent DNA damage pathway as a novel tumor suppressor and radiation sensitizer

In the treatment of most malignancies, radiotherapy plays a significant role. However, the resistance of cancer cells to ionizing radiation (IR) is the main reason for the failure of radiotherapy, which causes tumor recurrence and metastasis. In this study, we confirmed that GPR162, an orphan receptor in the G-protein-coupled receptor family, acted as a novel radiotherapy sensitizer by interacting with the stimulator of interferon genes (STING), which targeted DNA damage responses, activated IRF3, accelerated the activation of type I interferon system, promoted the expression of chemokines including CXCL10 and CXCL4, and inhibited the occurrence and development of tumors. Interestingly, the activation of STING by overexpression of GPR162 was independent of the classical pathway of cGAS. STING inhibitors could resist the antitumor effect of overexpression of GPR162 in IR-induced mouse models. In addition, most solid tumors showed low expression of GPR162. And the higher expression of GPR162 indicated a better prognosis in patients with lung adenocarcinoma, liver cancer, breast cancer, etc. In summary, these results suggested that GPR162 may serve as a potential sensitizer of radiotherapy by promoting radiotherapy-induced STING-IFN production and increasing the expression of chemokines including CXCL10 and CXCL4 in DNA damage response, providing an alternative strategy for improving cancer radiotherapy.

Photochemically controlled activation of STING by CAIX-targeting photocaged agonists to suppress tumor cell growth.

Controllable activation of the innate immune adapter protein - stimulator of interferon genes (STING) pathway is a critical challenge for the clinical development of STING agonists due to the potential "on-target off-tumor" toxicity caused by systematic activation of STING. Herein, we designed and synthesized a photo-caged STING agonist 2 with a tumor cell-targeting carbonic anhydrase inhibitor warhead, which could be readily uncaged by blue light to release the active STING agonist leading to remarkable activation of STING signaling. Furthermore, compound 2 was found to preferentially target tumor cells, stimulate the STING signaling in zebrafish embryo upon photo-uncaging and to induce proliferation of macrophages and upregulation of the mRNA expression of STING as well as its downstream NF-kB and cytokines, thus leading to significant suppression of tumor cell growth in a photo-dependent manner with reduced systemic toxicity. This photo-caged agonist not only provides a powerful tool to precisely trigger STING signalling, but also represents a novel controllable STING activation strategy for safer cancer immunotherapy.

Activation of STING by SAMHD1 Deficiency Promotes PANoptosis and Enhances Efficacy of PD-L1 Blockade in Diffuse Large B-cell Lymphoma.

Genomic instability is a significant driver of cancer. As the sensor of cytosolic DNA, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a critical role in regulating anti-tumor immunity and cell death. However, the role and regulatory mechanisms of STING in diffuse large B-cell lymphoma (DLBCL) are still undefined. In this study, we reported that sterile alpha motif and HD domain-containing protein 1 (SAMHD1) deficiency induced STING expression and inhibited tumor growth in DLBCL. High level of SAMHD1 was associated with poor prognosis in DLBCL patients. Down-regulation of SAMHD1 inhibited DLBCL cell proliferation both in vitro and in vivo. Moreover, we found that SAMHD1 deficiency induced DNA damage and promoted the expression of DNA damage adaptor STING. STING overexpression promoted the formation of Caspase 8/RIPK3/ASC, further leading to MLKL phosphorylation, Caspase 3 cleavage, and GSDME cleavage. Up-regulation of necroptotic, apoptotic, and pyroptotic effectors indicated STING-mediated PANoptosis. Finally, we demonstrated that the STING agonist, DMXAA, enhanced the efficacy of a PD-L1 inhibitor in DLBCL. Our findings highlight the important role of STING-mediated PANoptosis in restricting DLBCL progression and provide a potential strategy for enhancing the efficacy of immune checkpoint inhibitor agents in DLBCL.

A non-nucleotide agonist that binds covalently to cysteine residues of STING.

Stimulator of interferon genes (STING) is an ER-localized transmembrane protein and the receptor for 2',3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP), which is a second messenger produced by cGAMP synthase (cGAS), a cytosolic double-stranded DNA sensor. The cGAS-STING pathway plays a critical role in the innate immune response to infection of a variety of DNA pathogens through the induction of the type I interferons. Pharmacological activation of STING is a promising therapeutic strategy for cancer, thus the development of potent and selective STING agonists has been pursued. Here we report that mouse STING can be activated by phenylarsine oxide (PAO), a membrane permeable trivalent arsenic compound that preferentially reacts with thiol group of cysteine residue (Cys). The activation of STING with PAO does not require cGAS or cGAMP. Mass spectrometric analysis of the peptides generated by trypsin and chymotrypsin digestion of STING identifies several PAO adducts, suggesting that PAO covalently binds to STING. Screening of STING variants with single Cys to serine residues (Ser) reveals that Cys88 and Cys291 are critical to the response to PAO. STING activation with PAO, as with cGAMP, requires the ER-to-Golgi traffic and palmitoylation of STING. Our results identify a non-nucleotide STING agonist that does not target the cGAMP-binding pocket, and demonstrate that Cys of STING can be a novel target for the development of STING agonist.Key words: STING agonist, cysteine modification, innate immunity, phenylarsine oxide.

Involvement of the STING signaling in COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic caused by the infection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has cast a notorious damage to the public health and global economy. The Stimulator of Interferon Genes (STING) is a crucial element of the host antiviral pathway and plays a pivotal but complex role in the infection and development of COVID-19. Herein, we discussed the antagonistic mechanism of viral proteins to the STING pathway as well as its activation induced by host cells. Specifically, we highlighted that the persistent activation of STING by SARS-CoV-2 led to abnormal inflammation, and STING inhibitors could reduce the excessive inflammation. In addition, we also emphasized that STING agonists possessed antiviral potency against diverse coronavirus and showed adjuvant efficacy in SARS-CoV-2 vaccines by inducing IFN responses.

Proteomics analysis uncovers plasminogen activator PLAU as a target of the STING pathway for suppression of cancer cell migration and invasion

The stimulator of interferon genes (STING) pathway is vital for immune defense against pathogen invasion and cancer. Although ample evidence substantiates that the STING signaling pathway plays an essential role in various cancers via cytokines, no comprehensive investigation of secretory proteins regulated by the STING pathway has been conducted hitherto. Herein, we identify 24 secretory proteins significantly regulated by the STING signaling pathway through quantitative proteomics. Mechanistic analyses reveal that STING activation inhibits the translation of urokinase-type plasminogen activator (PLAU) via the STING-PERK-eIF2α signaling axis. PLAU is highly expressed in a variety of cancers and promotes the migration and invasion of cancer cells. Notably, the activation of STING inhibits cancer cell migration and invasion by suppressing PLAU. Collectively, these results provide novel insights into the anticancer mechanism of the STING pathway, offering a theoretical basis for precision therapy for this patient population.

Characterization of a Cyclic Dinucleotide Metabolic Switch to Fuel Antitumor Immunity

Chimeric antigen receptor (CAR) T cells have revolutionized the treatment of patients with relapsed and/or refractory lymphomas resulting in high response rates even in heavily pretreated individuals. Despite the efficacy of CAR T therapy in these cases, long-term disease control remains a challenge owing to the poor persistence and decreased survival of these cells in the tumor microenvironment (TME). Within the TME, CAR T cell activity and survival are impeded by increased metabolic stress from chronic stimulation, hypoxia, and limited nutrient availability. This ultimately leads to T cell exhaustion, a state characterized by dysfunctional mitochondria, decreased proliferation, and increased apoptosis. Memory T cells, particularly memory stem T cells (Tscm), are able to better adapt to the TME than effector T cells, which is in part secondary to metabolic reliance on β-oxidation of fatty acids (FAO) as opposed to glycolysis. This sustains mitochondrial ATP production and supports antioxidant pathways to limit cell stress leading to enhanced persistence and improved tumor control by Tscm. As effector T cells make up the bulk of CAR T products and Tscm are quite rare, tuning CAR T cell metabolism to enhance Tscm production could be a means to improve the long-term efficacy of cellular therapies. Our lab previously observed that treatment of mice with the mammalian cyclic dinucleotide (CDN) 2'3'-cGAMP increased the persistence and proliferation of Th/Tc17 cells expressing an anti-neu CAR in a model of locally advanced breast cancer. CDNs are evolutionarily conserved second messengers that classically activate the innate immune system in response to pathogens by binding to pattern recognition receptors, but more recent data shows that they are also important in the antitumor immune response by modulating tumor immunogenicity. We now extend those findings and show that treatment of isolated T cells with cGAMP induces a T cell intrinsic mechanism that drives Tscm formation in ex vivo expanded murine T cells. Th/Tc17 cells treated with cGAMP during their in vitro differentiation and expansion show a 5-10 fold increase in Tscm compared to control cells. This is supported by increased expression of the transcription factors Tcf7 and Lef1, which are key mediators in maintaining T cell stemness and memory. Though CDNs are thought to mediate their downstream effects mainly through activation of the adaptor protein STING (stimulator of interferon genes), our data indicates that CDNs promote T cell memory independent of canonical STING activation in Th/Tc17 cells. This may in part explain why we see minimal cytotoxicity in Th/Tc17 cells treated with cGAMP as compared to prior reports which observed STING dependent cell death following CDN exposure in other T cell subsets. Instead, CDNs activate AMPK (AMP-activated protein kinase) leading to metabolic reprogramming in Th/Tc17 cells. Total RNA sequencing data and functional studies of cellular bioenergetics point to reduced glycolytic metabolism following cGAMP treatment. Downstream of AMPK activation we also observe inhibition of acetyl-CoA carboxylase (ACC), the rate limiting enzyme in fatty acid synthesis, and upregulation of Cpt1a which is key to FAO, suggestive of enhanced fatty acid usage as a fuel source. Collectively this metabolic profile favors the production of Tscm and further work is ongoing to delineate the molecular mechanisms behind this cGAMP triggered metabolic switch. As there is increasing evidence that tumor cells secrete 2'3'-cGAMP in the TME, this pathway could be readily targeted to manipulate the bioenergetics of CAR T cells to maximize their memory potential and enhance their in vivo persistence and function.

GSDMD (Gasdermin D) Mediates Pathological Cardiac Hypertrophy and Generates a Feed-Forward Amplification Cascade via Mitochondria-STING (Stimulator of Interferon Genes) Axis

Cardiac hypertrophy is initially an adaptive response of cardiomyocytes to neurohumoral or hemodynamic stimuli. Evidence indicates that Ang II (angiotensin II) or pressure overload causes GSDMD (gasdermin D) activation in cardiomyocytes and myocardial tissues. However, the direct impact of GSDMD on cardiac hypertrophy and its underlying mechanisms are not fully understood. In this study, we examined the aberrant activation of GSDMD in mouse and human hypertrophic myocardia, and the results showed that GSDMD deficiency reduced Ang II or pressure overload-induced cardiac hypertrophy, dysfunction, and associated cardiomyocyte pyroptosis in mice. Mechanistically, Ang II-mediated GSDMD cleavage caused mitochondrial dysfunction upstream of STING (stimulator of interferon genes) activation in vivo and in vitro. Activation of STING, in turn, potentiated GSDMD-mediated cardiac hypertrophy. Moreover, deficiency of both GSDMD and STING suppressed cardiac hypertrophy in cardiac-specific GSDMD-overexpressing mice. Based on these findings, we propose a mechanism by which GSDMD generates a self-amplifying, positive feed-forward loop with the mitochondria-STING axis. This finding points to the prospects of GSDMD as a key therapeutic target for hypertrophy-associated heart diseases.

Signal strength of STING activation determines cytokine plasticity and cell death in human monocytes

The cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway is a cytosolic sensor of microbial and host-derived DNA and plays a key role in innate immunity. Activation of STING by cyclic dinucleotide (CDN) ligands in human monocytes induces a type I interferon response and production of pro-inflammatory cytokines associated with the induction of massive cell death. In this study we have re-evaluated the effect of signal strength of STING activation on the cytokine plasticity of human monocytes. CDN (2′3′c-GAMP) and non-CDN (diABZI, MSA-2) STING ligands in the range of EC50 concentrations (15 μM 2′3′c-GAMP, 100 nM diABZI, 25 μM MSA-2) induced IFN-β, IP-10, and large amounts of IL-1β and TNF-α, but no IL-10 or IL-19. Interestingly, LPS-induced production of IL-10 and IL-19 was abolished in the presence of diABZI or MSA-2, whereas IL-1β and TNF-α were not inhibited. Surprisingly, we observed that tenfold lower (MSA-2, i.e. 2.5 μM) or 100-fold lower (diABZI, i.e. 1 nM) concentrations strongly stimulated secretion of anti-inflammatory IL-10 and IL-19, but little of IL-1β and TNF-α. Induction of IL-10 was associated with up-regulation of PRDM1 (Blimp-1). While cytokine secretion stimulated by the higher concentrations was accompanied by apoptosis as shown by cleavage of caspase-3 and PARP-1, the low concentrations did not trigger overt cell death yet induced cleavage of gasdermin-D. Our results reveal a previously unrecognized plasticity of human monocytes in their signal strength-dependent production of pro- versus anti-inflammatory cytokines upon STING activation.

SHP-1 knockdown suppresses mitochondrial biogenesis and aggravates mitochondria-dependent apoptosis induced by all trans retinal through the STING/AMPK pathways

BackgroundOxidative stress-caused damage to the retinal pigment epithelium (RPE) underlies the onset and progression of age-related macular degeneration (AMD). Impaired mitochondrial biogenesis sensitizes RPE cells to mitochondrial dysfunction, energy insufficiency and death. Src-homology 2 domain-containing phosphatase (SHP)-1 is important in regulating immune responses and cell survival. However, its roles in cell survival are not always consistent. Until now, the effects of SHP-1 on RPE dysfunction, especially mitochondrial homeostasis, remain to be elucidated. We sought to clarify the effects of SHP-1 in RPE cells in response to atRAL-induced oxidative stress and determine the regulatory mechanisms involved.MethodsIn the all trans retinal (atRAL)-induced oxidative stress model, we used the vector of lentivirus to knockdown the expression of SHP-1 in ARPE-19 cells. CCK-8 assay, Annexin V/PI staining and JC-1 staining were utilized to determine the cell viability, cell apoptosis and mitochondrial membrane potential. We also used immunoprecipitation to examine the ubiquitination modification of stimulator of interferon genes (STING) and its interaction with SHP-1. The expression levels of mitochondrial marker, proteins related to mitochondrial biogenesis, and signaling molecules involved were examined by western blotting analysis.ResultsWe found that SHP-1 knockdown predisposed RPE cells to apoptosis, aggravated mitochondrial damage, and repressed mitochondrial biogenesis after treatment with atRAL. Immunofluoresent staining and immunoprecipitation analysis confirmed that SHP-1 interacted with the endoplasmic reticulum-resident STING and suppressed K63-linked ubiquitination and activation of STING. Inhibition of STING with the specific antagonist H151 attenuated the effects of SHP-1 knockdown on mitochondrial biogenesis and oxidative damage. The adenosine monophosphate-activated protein kinase (AMPK) pathway acted as the crucial downstream target of STING and was involved in the regulatory processes.ConclusionsThese findings suggest that SHP-1 knockdown potentiates STING overactivation and represses mitochondrial biogenesis and cell survival, at least in part by blocking the AMPK pathway in RPE cells. Therefore, restoring mitochondrial health by regulating SHP-1 in RPE cells may be a potential therapeutic strategy for degenerative retinal diseases including AMD.

ABCC1 transporter exports the immunostimulatory cyclic dinucleotide cGAMP.

The DNA sensor cyclic GMP-AMP synthase (cGAS) is important for antiviral and anti-tumor immunity. cGAS generates cyclic GMP-AMP (cGAMP), a diffusible cyclic dinucleotide that activates the antiviral response through the adaptor protein stimulator of interferon genes (STING). cGAMP cannot passively cross cell membranes, but recent advances have established a role for extracellular cGAMP as an "immunotransmitter" that can be imported into cells. However, the mechanism by which cGAMP exits cells remains unknown. Here, we identifed ABCC1 as a direct, ATP-dependent cGAMP exporter in mouse and human cells. We show that ABCC1 overexpression enhanced cGAMP export and limited STING signaling and that loss of ABCC1 reduced cGAMP export and potentiated STING signaling. We demonstrate that ABCC1 deficiency exacerbated cGAS-dependent autoimmunity in the Trex1-/- mouse model of Aicardi-Goutières syndrome. Thus, ABCC1-mediated cGAMP export is a key regulatory mechanism that limits cell-intrinsic activation of STING and ameliorates STING-dependent autoimmune disease.