Phosphorylation of innate immune adaptor proteins MAVS, STING, and TRIF induces IRF3 activation

STING and metabolism-related diseases: Roles, mechanisms, and applications

The stimulator of interferon genes (STING) pathway plays a critical role in innate immunity, acting as a central mediator that links cytosolic DNA sensing to inflammatory signaling. STING not only responds to cellular metabolic states but also actively regulates key metabolic processes, including glycolysis, lipid metabolism, and redox balance. This bidirectional interaction underscores the existence of a dynamic feedback mechanism between STING signaling and metabolic pathways, which is essential for maintaining cellular homeostasis. This review provides a comprehensive analysis, beginning with an in-depth overview of the classical STING signaling pathway, followed by a detailed examination of its reciprocal regulation of various metabolic pathways. Additionally, it explores the role and mechanisms of STING signaling in metabolic disorders, including obesity, diabetes, and atherosclerosis. By integrating these insights into the mutual regulation between STING and its metabolism, novel therapeutic strategies targeting this pathway in metabolic diseases have been proposed.

Inhibition of the cGAS-STING pathway: contributing to the treatment of cerebral ischemia-reperfusion injury

The cGAS-STING pathway plays an important role in ischemia-reperfusion injury in the heart, liver, brain, and kidney, but its role and mechanisms in cerebral ischemia-reperfusion injury have not been systematically reviewed. Here, we outline the components of the cGAS-STING pathway and then analyze its role in autophagy, ferroptosis, cellular pyroptosis, disequilibrium of calcium homeostasis, inflammatory responses, disruption of the blood-brain barrier, microglia transformation, and complement system activation following cerebral ischemia-reperfusion injury. We further analyze the value of cGAS-STING pathway inhibitors in the treatment of cerebral ischemia-reperfusion injury and conclude that the pathway can regulate cerebral ischemia-reperfusion injury through multiple mechanisms. Inhibition of the cGAS-STING pathway may be helpful in the treatment of cerebral ischemia-reperfusion injury.

The dual role of chaperone-mediated autophagy in the response and resistance to cancer immunotherapy

Cancer immunotherapy has become a revolutionary strategy in oncology, utilizing the host immune system to fight malignancies. Notwithstanding major progress, obstacles such as immune evasion by tumors and the development of resistance still remain. This manuscript examines the function of chaperone-mediated autophagy (CMA) in cancer biology, focusing on its effects on tumor immunotherapy response and resistance. CMA is a selective degradation mechanism for cytosolic proteins, which is crucial for sustaining cellular homeostasis and regulating immune responses. By degrading specific proteins, CMA can either facilitate tumor progression in stressful conditions, or promote tumor suppression by removing oncogenic factors. This double-edged sword highlights the complexity of CMA in cancer progression and its possible effect on treatment results. Here we clarify the molecular mechanisms by which CMA can regulate the immune response and its possible role as a therapeutic target for improving the effectiveness of cancer immunotherapy.

Tanshinone IIA alleviates myocarditis in Trex1-D18N lupus-like mice by inhibiting the interaction between STING and SEC24C

The cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway serves as a crucial component of the innate immune defense, playing a vital role in combating pathogen invasion. However, its dysregulation or abnormal activation can trigger the development of autoimmune diseases. This study demonstrated that Tanshinone IIA, a major lipid-soluble component of Salvia miltiorrhiza Bunge, can effectively inhibit the activation of the cGAS-STING signaling pathway. Mechanistically, Tanshinone IIA inhibits the transport of STING from the ER to the Golgi apparatus by weakening the interaction between STING and SEC24C, thereby preventing the activation of the cGAS-STING signaling pathway. Furthermore, Tanshinone IIA significantly ameliorated myocardial inflammation in WT and Trex1D18N/D18N mice. Our research indicates that Tanshinone IIA shows potential therapeutic value in alleviating autoimmune diseases by effectively inhibiting the abnormal activation of the cGAS-STING pathway.

Induction of the ISR by AB5 subtilase cytotoxin drives type-I IFN expression in pDCs via STING activation

We demonstrate that exposure to the AB5 subtilase cytotoxin (SubAB) induces the unfolded protein response (UPR) in human peripheral blood mononuclear cells, concomitant with a proinflammatory response across distinct cell subsets. Notably, SubAB selectively induces type-I interferon (IFN) expression in plasmacytoid dendritic cells, acting synergistically with Toll-like receptor 7 stimulation. The induction of type-I IFN in response to SubAB relies on stimulator of interferon genes (STING) activation, coupled with protein synthesis inhibition mediated by protein kinase R-like endoplasmic reticulum kinase (PERK) and phosphorylation of the eukaryotic translation initiation factor 2 subunit-alpha. By impeding mRNA translation through the integrated stress response, SubAB precipitates the downregulation of the negative innate signaling feedback regulator Tax1-binding protein 1. This downregulation is necessary to unleash TANK-binding kinase 1 signaling associated with STING activation. These findings shed light on how UPR-inducing conditions may regulate the immune system during infection or pathogenesis.

Zebrafish fkbp5 attenuates antiviral innate immunity by autophagic degradation of transcription factor irf7

Activation of the type I interferon (IFN-I) signaling pathway is crucial for protecting host cells against viral infections. IFN-I production requires the transcription factors IFN regulatory factor 3 (IRF3) and IRF7, and its regulation must be finely tuned to both combat infection effectively and prevent excessive immunopathology. Here, we report that selective autophagy mediated by zebrafish FK506-binding protein 5 (Fkbp5), a PPIase (peptidyl-prolyl isomerase) promotes the degradation of Irf7 and Irf3, thereby inhibiting virus-induced type I IFN production. Quantitative real-time reverse-transcription polymerase chain reaction experiments indicate that zebrafish fkbp5 is induced by viral infection. Moreover, disrupting fkbp5 in AB-line zebrafish using CRISPR/Cas9 enhances survival rates and reduces viral messenger RNA levels compared with wild-type zebrafish. In cell culture, using promoter analysis and quantitative real-time reverse-transcription polymerase chain reaction, we found fkbp5 overexpression significantly attenuates cellular antiviral capacity and facilitates viral proliferation. Mechanistically, we found that fkbp5 inhibits Irf3/7-induced IFN activation, which depends on the binding of Fkbp5 to the Irf3 or IRF association domain of Irf7 via co-immunoprecipitation and Western blot assays. Furthermore, Fkbp5 induces the autophagic degradation of Irf3 and Irf7 independent of its PPIase activity. Blocking autophagy in vivo and in vitro restores the regulation of the RLR (RIG-I-like receptor) pathway by fkbp5. These findings reveal a critical role for zebrafish fkbp5 in suppressing the activation of Irf7 and Irf3 for IFN signaling and antiviral immune responses.

The ELF3-TRIM22-MAVS signaling axis regulates type I interferon and antiviral responses

Activation of the innate immune response is essential for host cells to restrict the dissemination of invading viruses and other pathogens. Proteins belonging to the tripartite motif (TRIM) family are key effectors in antiviral innate immunity. Among these, TRIM22, a RING-type E3 ubiquitin ligase, has been recognized as a significant regulator in the pathogenesis of various diseases. In the present study, we identified TRIM22 as a critical modulator of mitochondrial antiviral signaling protein (MAVS) activation. Loss of TRIM22 function led to reduced production of type I interferons (IFNs) in response to viral infection such as influenza A virus (IAV) or vesicular stomatitis virus (VSV), thereby facilitating viral replication. Mechanistically, TRIM22 was found to enhance retinoic acid-inducible gene I (RIG-I)-mediated signaling through the catalysis of Lys63-linked polyubiquitination of MAVS, which, in turn, activated the TANK-binding kinase 1 (TBK1)/interferon regulatory factor 3 (IRF3) pathway, driving IFN-β production. Additionally, TRIM22 was shown to inhibit the assembly of the MAVS-NLRX1 inhibitory complex, further amplifying innate immune responses. Our findings also demonstrated that RNA virus infection upregulated TRIM22 expression via the nuclear translocation of ELF3, a transcription factor that activates TRIM22 gene expression. This regulatory loop underscores the role of TRIM22 in modulating the type I IFN pathway, providing critical insights into the host's antiviral defense mechanisms. Our research highlights the potential of targeting the ELF3-TRIM22-MAVS axis as a therapeutic strategy for enhancing antiviral immunity and preventing RNA virus infections.IMPORTANCEInterferon (IFN)-mediated antiviral responses are crucial for the host's defense against foreign pathogens and are regulated by various signaling pathways. The tripartite motif (TRIM) family, recognized for its multifaceted roles in immune regulation and antiviral defense, plays a significant part in this process. In our study, we explored the important role of TRIM22, a protein that helped regulate the host's immune response to viral infections. We found that TRIM22 enhances the Lys63-linked polyubiquitination of mitochondrial antiviral signaling protein (MAVS), which was essential for producing type I interferons. Interestingly, we discovered that the expression of TRIM22 increases after an RNA virus infection, due to a transcription factor ELF3, which moved into the nucleus of cells to activate TRIM22 transcription. This created a feedback loop that strengthens the role of TRIM22 in modulating the type I IFN pathway. By uncovering these mechanisms, we aimed to enhance our understanding of how the immune system works and provide insights that could lead to innovative antiviral therapies.

BAG2 Inhibits Cervical Cancer Progression by Modulating Type I Interferon Signaling through Stabilizing STING

Cervical cancer possesses high morbidity and mortality rates, and a comprehensive understanding of its molecular underpinnings is essential for advancing clinical management strategies. The innate immune sensor STING, which activates type I interferon signaling, plays a pivotal role in enhancing anti-tumor activity. Despite increased attention to STING's involvement in cervical cancer, the regulatory mechanisms governing its protein homeostasis remain poorly understood. In this study, it is found that the BAG2-STUB1 complex regulates ubiquitin proteasomal degradation of STING, which affects the development of cervical cancer. Mechanistically, BAG2 inhibits ubiquitination of STING and stabilizes it by interacting with STING. Specifically, BAG2 inhibits STUB1 from attaching the K48-linked ubiquitin chains at K338 and K370 of STING by forming a complex with STUB1. Functionally, enhanced BAG2 expression suppresses cervical cancer progression by activating the type I interferon pathway in a STING-dependent manner. Notably, clinical cervical cancer samples revealed a positive correlation between BAG2 and STING levels, with low BAG2 expression is strongly linked to advanced disease and poor prognosis in cervical cancer. Collectively, these findings elucidate the molecular mechanism by which the BAG2-STUB1 complex regulates STING homeostasis, underscoring BAG2's potential as a diagnostic biomarker and therapeutic target in cervical cancer.

Deciphering cGAS-STING signaling: implications for tumor immunity and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most prevalent form of primary liver cancer and poses a significant global health challenge due to its rising incidence and associated mortality. Recent advancements in understanding the cytosolic DNA sensing, the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway have illuminated its critical role in the immune response to HCC. This narrative review deciphers the multifaceted involvement of cGAS-STING in HCC, mainly its function in detecting cytosolic DNA and initiating type I interferon (IFN-I) responses, which are pivotal for antitumor immunity. This immune response is crucial for combating pathogens and can play a role in tumor surveillance. In the context of HCC, the tumor microenvironment (TME) can exhibit immune resistance, which complicates the effectiveness of therapies like immune checkpoint blockade. However, activation of the cGAS-STING pathway has been shown to stimulate antitumor immune responses, enhancing the activity of dendritic cells and cytotoxic T lymphocytes. There is ongoing research into STING agonists as a treatment strategy for HCC, with some studies indicating promising results in prolonging survival and enhancing the immune response against tumors. By summarizing current knowledge and identifying research gaps, this review aims to provide a comprehensive overview of cGAS-STING signaling in HCC and its future directions, emphasizing its potential as a therapeutic target in the fight against HCC. Understanding these mechanisms could pave the way for innovative immunotherapeutic approaches that enhance the efficacy of existing treatments and improve patient prognosis.

CINs of the cytoplasm: dissecting dsRNA signaling in chromosomal instability

Chromosomal instability (CIN), a pervasive feature of cancer, promotes tumor evolution and inflammatory signaling, yet its influence on innate immune sensing remains incompletely understood. Ruptured micronuclei, a direct byproduct of CIN arising from missegregated chromosomes, expose out-of-context double-stranded DNA that engages the cGAS-STING pathway. In their recent study, Sasaki et al. show that micronuclei are also a source of immunogenic double-stranded RNA (dsRNA), triggering MAVS-dependent type I interferon responses independently of STING. The authors show that micronuclei undergo aberrant transcription, producing dsRNA from nonexonic, transcriptionally accessible loci, with many species localizing near interferon-stimulated genes. This work suggests a feedforward loop in which type I interferon signaling reinforces its own activation through transcriptional dysregulation. Using MPS1 inhibition to induce acute CIN, the authors show that MAVS signaling promotes MHC Class I expression and immune cell recruitment. These findings reposition CIN as a dual trigger of innate immunity through cytoplasmic DNA and RNA sensing. Future work should define how these pathways integrate in the context of chronic CIN and evaluate strategies to target DNA and RNA sensing in immune-edited tumors.

PCK1 inhibits cGAS-STING activation by consumption of GTP to promote tumor immune evasion

Hypoxia induces immunosuppressive phenotypes in tumor cells even in the presence of cytosolic DNA accumulation. The mechanisms by which tumor cells suppress hypoxia-induced cGAS-STING activation for immune evasion remain largely unclear. Here, we demonstrate that hypoxic stimulation induces JNK1/2-mediated S151 phosphorylation of phosphoenolpyruvate carboxykinase 1 (PCK1), a rate-limiting enzyme in gluconeogenesis. This phosphorylation triggers the interaction between PCK1 and cGAS. The PCK1 associated with cGAS competitively consumes GTP, a substrate shared by both PCK1 and cGAS. Consequently, PCK1 inhibits GTP-dependent cGAS activation and subsequent STING-promoted immune cell infiltration and activation in the tumor microenvironment, leading to promoted tumor growth in mice. The blockade of PCK1 function, in combination with anti-PD-1 antibody treatment, exhibits an additive therapeutic effect on tumor growth. Additionally, PCK1 S151 phosphorylation is inversely correlated with cGAS-STING activation in human breast cancer specimens and patient survival. These findings reveal a novel regulation of cGAS-STING pathway and uncover the metabolic control of immune response in tumor cells.

ATP2A2 regulates STING1/MITA-driven signal transduction including selective autophagy

STING1/MITA not only induces innate immune responses but also triggers macroautophagy/autophagy to selectively degrade signaling molecules. However, the molecular mechanisms regulating STING1-mediated selective autophagy remain unclear. Here, we first report that ATP2A2 directly interacts with STING1, regulating STING1-mediated innate immune response by modulating its polymerization and trafficking, thereby inhibiting DNA virus infection. Notably, while screening for reticulophagy receptors involved in STING1-mediated selective autophagy, we identified SEC62 as an important receptor protein in STING1-mediated reticulophagy. Mechanistically, SEC62 strengthens its interaction with STING1 upon activation and concurrently facilitates STING1-mediated reticulophagy upon starvation, which are dependent on ATP2A2. Furthermore, knocking down SEC62 in WT cells inhibits STING1-mediated MAP1LC3B/LC3B lipidation and autophagosome formation, an effect that is lost in ATP2A2 knockout cells, suggesting that SEC62's role in STING1-mediated selective autophagy is ATP2A2 dependent. Thus, our findings identify the reticulophagy receptor SEC62 as a novel receptor protein regulating STING1-mediated selective autophagy, providing new insight into the mechanism regarding a reticulophagy receptor in the process of STING1-induced selective autophagy.Abbrevations: aa: amino acids; AP-MS: affinity tag purification-mass spectrometry; ATP2A1: ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 1; ATP2A2: ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 2; ATP2A3: ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 3; CANX: calnexin; CCPG1: cell cycle progression 1; CGAS: cyclic GMP-AMP synthase; ctDNA: calf thymus DNA; dsRNA: double-stranded RNA; diABZI: diamidobenzimidazole; ER: endoplasmic reticulum; ERGIC: ER-Golgi intermediate compartment; EBSS: Earle's Balanced Salt Solution; EV: empty vector; FL: full length; GOLGA2/GM130: golgin A2; HSV-1: herpes simplex virus type 1; IRF3: interferon regulatory factor 3; IFNs: type I interferons; ISD: interferon stimulatory DNA; KO: knockout; MAVS: mitochondrial antiviral signaling protein; MOI: multiplicity of infection; poly(I:C): polyinosinic-polycytidylic acid; NBR1: NBR1 autophagy cargo receptor; PRR: pattern recognition receptor; reticulophagy: selective autophagic degradation of the ER; RETREG1/FAM134B: reticulophagy regulator 1; RIGI: RNA sensor RIG-I; RTN3L: reticulon 3; SEC62: SEC62 homolog, preprotein translocation factor; SeV: Sendai virus; STIM1: stromal interaction molecule 1; STING1/MITA: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; TEX264: testis expressed 264, ER-phagy receptor; TMX1: thioredoxin related transmembrane protein 1; VSV: vesicular stomatitis virus; VACV: vaccinia virus; ZMPSTE24: zinc metallopeptidase STE24.

STING-∆C, a novel splice isoform of STING, inhibits DNA virus-induced innate immunity and autophagy

Stimulator of interferon genes (STING) plays a critical role in the innate immune response to cytosolic DNA, primarily activating type I interferons (IFNs). Although alternative splicing is known to modulate immune pathways, the influence of STING splice isoforms requires further exploration. Here, we identified STING-∆C, a novel splice isoform of STING generated by retention of intron 6, resulting in a truncated C-terminus. While STING-∆C shares its N-terminal domain with full-length STING, it contains a unique C-terminal sequence. STING-∆C acts as a dominant negative regulator of cGAS-STING signaling pathway by suppressing cGAS-, 2'3'-cGAMP-, and STING-mediated activation of the IFN response. Gain- and loss-of-function experiments showed that STING-∆C inhibited IFN production in response to double-stranded DNA and DNA virus, including HSV-1 and HPV. Furthermore, STING-∆C promoted HSV-1 replication and reduces STING-induced autophagy. Mechanistically, STING-∆C interacts with full-length STING, preventing its oligomerization and assembly with TBK1, a vital component of the STING-TBK1-IRF3 signalsome. This interaction blocks IRF3 phosphorylation and nuclear translocation, thereby halting IFN production. STING-∆C thus represents a newly identified splice isoform that negatively regulates cGAS-STING signaling. These findings broaden our understanding of STING's regulatory mechanisms and may guide therapeutic strategies for autoimmune diseases and viral infections linked to excessive STING activation.

Cisplatin Promotes Hepatotoxicity by cGAS-STING Mediated Innate Immune Response

Although platinum-based chemotherapy represented by cisplatin has been widely approved for the management of diverse cancer types, its hepatotoxicity and other adverse effects impact patient prognosis, while currently, there are few effective strategies for prevention or treatment. RNA sequencing analysis indicated that the type I interferon (IFN-I) pathway was significantly upregulated in cisplatin-induced liver injury (CILI) mouse model. The cGAS-STING signaling was found to be significantly activated in vitro and CILI model in vivo. Mechanistically, cisplatin-induced DNA damage triggered the release of double-stranded DNA (dsDNA), which subsequently activated the cGAS-STING pathway. The activated pathway promoted the production of IFN-I and induced apoptosis, ultimately contributing to liver injury. Importantly, inhibition of the cGAS-STING pathway, either by enzymatic digestion of dsDNA or by genetic knockout of cGAS, effectively attenuated IFN-I production and liver injury in response to cisplatin. Overall, our results highlight the cGAS-STING-IFN-I axis as a promising therapeutic target for preventing and treating platinum-based drug-induced liver damage.

SIRT5 modulates mitochondria function via mitophagy and antioxidant mechanisms to facilitate oocyte maturation in mice

Mitochondrial homeostasis, closely associated with mitophagy and antioxidant mechanisms, is essential for proper meiotic spindle assembly and chromosome segregation during oocyte maturation. SIRT5, known to modulate mitochondrial function under various conditions, has been shown to impact oocyte quality when inhibited, however, the precise mechanisms linking SIRT5 to mitochondrial homeostasis during meiotic progression remain unclear. In this study, we demonstrate that SIRT5 localizes predominantly at the periphery of the meiotic spindle and is enriched on chromosomes during oocyte maturation. Inhibition of SIRT5 led to significant meiotic defects, including disrupted spindle organization and chromosome misalignment. These defects were associated with increased histone acetylation, which impaired kinetochore-microtubule attachments. Moreover, SIRT5 inhibition resulted in mitochondrial dysfunction, subsequently elevating ROS levels and triggering oxidative stress, which further exacerbated meiotic abnormalities. Mechanistically, SIRT5 inhibition disrupted the balance of Parkin-dependent mitophagy by inducing ULK phosphorylation. Additionally, it activated the PI3K/Akt signaling pathway, which increased NADPH consumption and reduced GSH levels. Collectively, these findings reveal that SIRT5 plays dual roles in maintaining mitochondrial homeostasis during oocyte maturation: (1) by regulating Parkin-dependent mitophagy to prevent excessive mitochondrial clearance, and (2) by preserving the NADPH/GSH antioxidant system to ensure redox balance. These insights provide potential targets for improving oocyte quality and addressing mitochondrial dysfunction-related reproductive disorders in females.

Targeting a key disulfide linkage to regulate RIG-I condensation and cytosolic RNA-sensing

Maintaining innate immune homeostasis is critical for preventing infections and autoimmune diseases but effective interventions are lacking. Here we identified C864-C869-mediated intermolecular disulfide-linkage formation as a critical step for human RIG-I activation that can be bidirectionally regulated to control innate immune homeostasis. The viral-stimulated C864-C869 disulfide linkage mediates conjugation of an SDS-resistant RIG-I oligomer, which prevents RIG-I degradation by E3 ubiquitin-ligase MIB2 and is necessary for RIG-I to perform liquid-liquid phase separation to compartmentalize downstream signalsome, thereby stimulating type I interferon signalling. The corresponding C865S 'knock-in' caused an oligomerization defect and liquid-liquid phase separation in mouse RIG-I, which inhibited innate immunity, resulting in increased viral load and mortality in mice. Using unnatural amino acids to generate covalent C864-C869 linkage and the development of an interfering peptide to block C864-C869 residues, we bidirectionally regulated RIG-I activities in human diseases. These findings provide in-depth insights on mechanism of RIG-I activation, allowing for the development of methodologies that hold promising implications in clinics.

Development of a TBK1 and ALK dual inhibitor for alleviating depressive behavior via anti-inflammatory effects

Polypharmacology offers innovative strategies for treating immune and inflammatory dysregulation in complex diseases. Here, we identified ALS-04, a dual inhibitor of TANK-binding kinase 1 (TBK1) and anaplastic lymphoma kinase (ALK), which are closely linked to stimulator of interferon genes (STING)-mediated immune responses. ALS-04 effectively suppressed 2'3'-cyclic GMP-AMP (cGAMP)- and lipopolysaccharide (LPS)-induced type I interferon and pro-inflammatory responses by targeting the STING-TBK1 and STING-ALK pathways. Furthermore, ALS-04 significantly alleviated depressive symptoms, including anhedonia and behavioral despair, in an LPS-induced mouse model of depression. These findings highlight the therapeutic potential of dual TBK1 and ALK inhibition in depression by modulating immune and inflammatory pathways.

PWWP3A disrupts the assembly of VISA/MAVS signalosome to inhibit innate immune response against RNA viruses

VISA/MAVS is crucial in antiviral innate immunity. Upon RNA virus infection, VISA recruits TBK1 via TRAFs to mitochondria, inducing IRF3 phosphorylation and type I interferons. However, TBK1 recruitment mechanisms via individual TRAFs are unclear. Here, we reveal that PWWP domain-containing 3A (PWWP3A) serves as a negative regulator of RNA virus-triggered signaling. During viral infection, PWWP3A translocates from nucleus to the mitochondria, competing with TRAF6 for binding to VISA, thereby impeding the recruitment of TBK1 and inhibiting IRF3 activation. However, the extent of PWWP3A-mediated inhibition is regulated by the E3 ligase PJA2, which induces PWWP3A degradation post-infection, highlighting the intricate regulatory network in antiviral immunity. Consistently, PWWP3A deficiency enhances antiviral responses, and Pwwp3a-/- mice exhibit elevated levels of type I interferons and displayed greater resistance following RNA virus infection. Together, our findings unveil the inhibitory role of PWWP3A in virus-triggered signaling, which provides insights into preventing excessive immune responses.

Enhancing nano-immunotherapy of cancer through cGAS-STING pathway modulation

Activation of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway plays a critical role in cancer immunotherapy due to the secretion of multiple pro-inflammatory cytokines and chemokines. Numerous cGAS-STING agonists have been developed for preclinical and clinical trials in tumor immunity. However, several obstacles, such as agonist molecules requiring multiple doses, rapid degradation and poor targeting, weaken STING activation at the tumor site. The advancement of nanotechnology provides an optimized platform for the clinical application of STING agonists. In this review, we summarize events of cGAS-STING pathway activation, the dilemma of delivering STING agonists, and recent advances in the nano-delivery of cGAS-STING agonist formulations for enhancing tumor immunity. Furthermore, we address the future challenges associated with STING-based therapies and offer insights to guide subsequent clinical applications.

Neuronal STING-GAT1 signaling maintains paclitaxel-induced neuropathic pain in the spinal cord

ABSTRACT

Stimulator of interferon genes (STING), a pivotal immune regulator, has emerged as a contributor to nociception, yet its role in chronic pains remains still unknown. Here, we demonstrate that STING plays a dual role in normal and neuropathic pain in mature male rodents. Stimulator of interferon genes maintains type I interferon (IFN-I) level restraining pain sensitivity in normal and sham control, while activated STING/interferon regulatory factor 3 (IRF3) signaling increases the expression of gamma-aminobutyric acid (GABA) transporter 1 (GAT1) in the spinal cord (SC), thus, generating paclitaxel (PTX)-induced peripheral neuropathy. Genetic interference of STING (STING-/- mice) attenuated PTX-induced mechanical hypersensitivity with attenuated PTX-induced GAT1 increase, preventing PTX-induced increase in tonic GABAA inhibition of the spinal dorsal horn neurons. Stimulator of interferon genes regulates GAT expression through a TANK-binding kinase 1 (TBK1)-IRF3 signaling pathway, with IRF3 as a crucial transcription factor. Silencing neuronal STING, as opposed to its astrocytic counterpart, effectively restrained the PTX-induced mechanical hypersensitivity and GAT1 increase in the SC. Pharmacological inhibition of STING (H-151) efficiently diminished the TBK1/IRF3/GAT1 signaling pathway to alleviate PTX-induced mechanical hypersensitivity. Our findings show that STING-IRF3 serves a dual role: suppressing physiological nociception through IFN-I and acting as a transcriptional regulator of GAT1, contributing to chemotherapy-induced neuropathic pain.

Cyprinid herpesvirus 2 (CyHV-2) ORF67 inhibits IFN expression by competitively obstructing STING phosphorylation

Cyprinid herpesvirus 2 (CyHV-2) caused hematopoietic necrosis in crucian carp (Carassius auratus) has resulted in huge economic losses to the carp aquaculture. Interferon (IFN) response serves as a crucial line of defense for fish against CyHV-2 infection; however, CyHV-2 frequently overcomes this defense, resulting in damage and even substantial mortality. The mechanism by which CyHV-2 evades the fish IFN antiviral response remains unclear. In this study, we chose the open reading frame 67 (ORF67) of CyHV-2 as the target of our research. Firstly, the results of Co-immunoprecipitation (Co-IP) assay and in vitro phosphorylation showed that the ORF67 inhibited the expression of IFN by binding to TBK1-A/B and competitively blocking STING-A/B phosphorylation. Then, we elaborated on the effect of ORF67 on the cell's antiviral function by cytopathic effect (CPE) and immunoblot analysis. In summary, this study has clarified the molecular mechanism of immune evasion by ORF67 through the inhibition of host IFN expression. This research enhances our understanding of the pathogenesis of CyHV-2 and provides theoretical references for the prevention and treatment of hematopoietic necrosis.

STING aggravates ferroptosis-dependent myocardial ischemia-reperfusion injury by targeting GPX4 for autophagic degradation

Despite advancements in interventional coronary reperfusion technologies following myocardial infarction, a notable portion of patients continue to experience elevated mortality rates as a result of myocardial ischemia-reperfusion (MI/R) injury. An in-depth understanding of the mechanisms underlying MI/R injury is crucial for devising strategies to minimize myocardial damage and enhance patient survival. Here, it is discovered that during MI/R, double-stranded DNA (dsDNA)-cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signal accumulates, accompanied by high rates of myocardial ferroptosis. The specific deletion of cgas or Sting in cardiomyocytes, resulting in the inhibition of oxidative stress, has been shown to mitigate ferroptosis and I/R injury. Conversely, activation of STING exacerbates ferroptosis and I/R injury. Mechanistically, STING directly targets glutathione peroxidase 4 (GPX4) to facilitate its degradation through autophagy, by promoting the fusion of autophagosomes and lysosomes. This STING-GPX4 axis contributes to cardiomyocyte ferroptosis and forms a positive feedback circuit. Blocking the STING-GPX4 interaction through mutations in T267 of STING or N146 of GPX4 stabilizes GPX4. Therapeutically, AAV-mediated GPX4 administration alleviates ferroptosis induced by STING, resulting in enhanced cardiac functional recovery from MI/R injury. Additionally, the inhibition of STING by H-151 stabilizes GPX4 to reverse GPX4-induced ferroptosis and alleviate MI/R injury. Collectively, a novel autophagy-dependent ferroptosis mechanism is identified in this study. Specifically, STING autophagy induced by anoxia or ischemia-reperfusion leads to GPX4 degradation, thereby presenting a promising therapeutic target for heart diseases associated with I/R.

Discovery of Potent STING Inhibitors Bearing a Difluorobenzodioxol Structural Motif as Potent Anti-Inflammatory Agents

Given the critical role of STING in autoimmune and inflammatory disorders, the development of targeted small-molecule inhibitors has been a promising strategy for the treatment of these diseases. Nevertheless, the currently reported STING inhibitors suffer from limited structural diversity, species sensitivity, and poor activity; therefore, none are suitable for clinical investigation. Herein, we performed a structural modification campaign on the tool compound 6 (H-151) based on its potential metabolic hotspots. Compound 66, bearing a difluorobenzodioxol moiety, was identified as one of the most potent STING inhibitors with IC50 values of 116 and 96.3 nM for h- and m-STING, respectively. This compound exhibited a notable enhancement in metabolic properties, especially in terms of metabolic stability. A mechanism study verified that 66 engaged with STING in a covalent manner akin to that of 6. In both the cisplatin-induced acute kidney injury and TREX1 D18N mouse models, 66 significantly alleviated tissue injury and inflammation.

Cancer-cell-derived cGAMP limits the activity of tumor-associated CD8+ T cells

Using a mouse tumor model with inducible cancer-cell-intrinsic cyclic GMP-AMP (cGAMP) synthase (cGAS) expression, we show that cancer-cell-derived cGAMP is essential and sufficient to trigger a sustained type I interferon response within the tumor microenvironment. This leads to improved CD8+ T cell-dependent tumor restriction. However, cGAMP limits the proliferation, survival, and function of stimulator of IFN genes (STING)-expressing, but not of STING-deficient, CD8+ T cells. In vivo, STING deficiency in CD8+ T cells enhances tumor restriction. Consequently, cancer-cell-derived cGAMP both drives and limits the anti-tumor potential of CD8+ T cells. Mechanistically, T cell-intrinsic STING is associated with pro-apoptotic and antiproliferative gene signatures. Our findings suggest that STING signaling acts as a checkpoint in CD8+ T cells that balances tumor immunity.

Human papillomavirus E1 proteins inhibit RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT signaling pathways to evade innate antiviral immunity

Human papillomavirus (HPV) is a major etiological agent of both malignant and benign lesions, with high-risk types, such as HPV16 and HPV18, being strongly linked to cervical cancer, while low-risk types like HPV11 are associated with benign conditions. While viral proteins such as E6 and E7 are well-established regulators of immune evasion, the role of E1 in modulating the host antiviral responses remains insufficiently characterized. This study investigates the immunomodulatory functions of HPV16 and HPV11 E1 in suppressing innate antiviral immune signaling pathways. Through a combination of RT-qPCR and luciferase reporter assays, we demonstrate that E1 suppresses the production of interferons and interferon-stimulated genes triggered by viral infections and the activation of RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT pathways. Co-immunoprecipitation assays reveal that E1 interacts directly with key signaling molecules within these pathways. E1 also impairs TBK1 and IRF3 phosphorylation and obstructs the nuclear translocation of IRF3, thereby broadly suppressing IFN responses. Additionally, E1 disrupts the JAK-STAT pathway by binding STAT1, which prevents the assembly and nuclear localization of the ISGF3 complex containing STAT1, STAT2, and IRF9, thereby further diminishing antiviral response. These findings establish E1 as a pivotal regulator of immune evasion and suggest its potential as a novel therapeutic target to enhance antiviral immunity in HPV-associated diseases.

Bilirubin metabolism in the liver orchestrates antiviral innate immunity in the body

Bilirubin metabolism crucially maintains normal liver function, but whether it contributes to antiviral immunity remains unknown. Here, we reveal that the liver bilirubin metabolic pathway facilitates antiviral innate immunity of the body. We discovered that viral infection upregulates uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) expression in the liver, which in turn stabilizes IRF3 proteins to promote type I interferon (IFN-I) production. Moreover, we found that serum unconjugated bilirubin (UCB), a unique physiological substrate of UGT1A1, can competitively inhibit the binding of IFN-I to IFN-I receptor 2 (IFNAR2), thus attenuating IFN-I-induced antiviral signaling of the body. Accordingly, effective bilirubin metabolism in the liver promotes antiviral immunity of the body by specifically employing liver UGT1A1-mediated enhancement of IFN-I production and reducing serum bilirubin-mediated inhibition of IFN-I signaling. This study uncovers the significance of bilirubin metabolism in antiviral innate immunity and demonstrates that conventional IFN-I therapy is less efficient for patients with hepatitis B virus (HBV) with high levels of bilirubin.

Shared Mechanisms of Blood-Brain Barrier Dysfunction and Neuroinflammation in Coronavirus Disease 2019 and Alzheimer Disease

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has highlighted the virus's impact on the central nervous system and its potential to exacerbate neurodegenerative diseases, like Alzheimer disease (AD). Emerging evidence suggests that SARS-CoV-2 infection contributes to chronic neuroinflammation, a key driver in the etiopathogenesis of AD. Shared mechanisms, including blood-brain barrier (BBB) dysfunction, systemic inflammation, and activation of immune pathways, may link SARS-CoV-2 infection to AD onset and/or progression, particularly among vulnerable individuals, such as those of advanced age. This review explores convergent pathways involving the renin-angiotensin-aldosterone system, Wnt/β-catenin signaling, NF-κB activation, and interferon signaling, focusing on their roles in BBB integrity and neuroinflammation. SARS-CoV-2-mediated angiotensin-converting enzyme 2 depletion disrupts renin-angiotensin-aldosterone system homeostasis, favoring proinflammatory signaling that parallels vascular dysfunction in AD. Dysregulation of Wnt/β-catenin signaling exacerbates BBB permeability, whereas NF-κB and interferon pathways contribute to BBB breakdown and propagate central nervous system inflammation via endothelial and immune cell activation. These interactions may amplify prodromal AD pathology and/or initiate AD pathogenesis. By identifying mechanistic overlaps between COVID-19 and AD, this review underlines the need for therapeutic strategies targeting shared pathways of inflammation and BBB dysfunction. Understanding these connections is critical for mitigating the long-term neurologic sequelae of COVID-19 and reducing the burden of AD.

cGAS-STING signaling in melanoma: regulation and therapeutic targeting

Melanocytes are the source of the skin cancer known as melanoma. It usually affects the viscera, mucous membranes, and skin. Even so, melanoma only makes for 7% of all skin cancer occurrences. By triggering the generation of type I interferons (IFN-I) and inflammatory cytokines upon identifying microbial DNA, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway promotes anti-microbial innate immunity. A growing body of research indicates that antitumor immunity depends on the cGAS-STING axis being activated. The cGAS-STING-regulated downstream cytokines, particularly IFN-I, act as linkages between adaptive and innate immunity. As a result, an increasing amount of research has concentrated on the synthesis and screening of agonists of the STING pathway. As a result, an increasing amount of research has concentrated on the synthesis and screening of agonists of the STING pathway. The many implications of the cGAS-STING pathway in the pathophysiology and therapy of melanoma are thoroughly examined in this study. Our research highlights the significance of the cGAS-STING pathway in melanoma and identifies it as a key target for boosting immunity against tumors.

ZNF593 regulates the cGAS-mediated innate immune response by attenuating cGAS-DNA binding

The enzyme cyclic GMP-AMP synthase (cGAS) is essential for detecting aberrantly located double-stranded DNA (dsDNA) from genomic, mitochondrial, and microbial origins. Through the synthesis of 2'3'-cGAMP, cGAS triggers the activation of the stimulator of interferon genes pathway, which initiates in vivo innate immune responses. Here, we identify zinc finger proteins ZNF593, which translocate from the nucleus to the cytoplasm after viral infection, as a negative regulator of antiviral type I IFN (IFN-I) production. ZNF593 directly binds to cGAS and suppresses its activation by inhibiting the cGAS-dsDNA interaction. ZNF593 deficiency increases IRF3 nuclear translocation and promotes DNA virus-triggered IFN production. Furthermore, ZNF593 deficiency promotes antiviral innate responses in vivo, improving survival rates in mice against HSV-1 infection. We further find that ZNF593 plays a protective role in systemic lupus erythematosus (SLE) pathology. Notably, replenishing ZNF593 effectively reduced IFN production in peripheral blood mononuclear cells (PBMCs) of SLE patients or in the TMPD-induced murine SLE model. Our findings suggest that ZNF593 negatively regulates IFN-β signaling by targeting cGAS activation, providing new insights into the regulatory mechanisms for antiviral defenses and autoimmune diseases.

Human papillomavirus E2 proteins suppress innate antiviral signaling pathways

Human papillomavirus (HPV) is a major cause of cancers and benign lesions. High-risk (HR) types, including HPV16 and HPV18, are strongly implicated in cervical and other malignancies, while low-risk (LR) types, such as HPV11, are predominantly associated with benign conditions. Although the immune evasion of HPV oncoproteins E6 and E7 are extensively studied, the immunomodulatory functions of the E2 protein remain poorly underexplored. This study elucidates the role of HPV11 and HPV16 E2 proteins in modulating innate immune responses, focusing on their interaction with key innate antiviral signaling pathways. We demonstrate that HPV11 and HPV16 E2 proteins effectively suppress the activation of pivotal antiviral signaling pathways, including RIG-I/MDA5-MAVS, TLR3-TRIF, cGAS-STING, and JAK-STAT. Mechanistic analyses reveal that E2 proteins interact with the core components of type I interferon (IFN)-inducing pathways, inhibiting IRF3 phosphorylation and nuclear translocation, thereby attenuating IFN expression. Additionally, E2 disrupts the JAK-STAT signaling cascade by preventing the assembly of the ISGF3 complex, comprising STAT1, STAT2, and IRF9, ultimately inhibiting the transcription of interferon-stimulated genes (ISGs). These findings underscore the broader immunosuppressive role of HPV E2 proteins, complementing the well-established immune evasion mechanisms mediated by E6 and E7. This work advances our understanding of HPV-mediated immune evasion and positions the E2 protein as a promising target for therapeutic strategies aimed at augmenting antiviral immunity in HPV-associated diseases.

The STING Signaling: A Novel Target for Central Nervous System Diseases

The canonical cyclic GMP-AMP (cGAMP) synthase (cGAS)-Stimulator of Interferon Genes (STING) pathway has been widely recognized as a crucial mediator of inflammation in many diseases, including tumors, infections, and tissue damage. STING signaling can also be activated in a cGAS- or cGAMP-independent manner, although the specific mechanisms remain unclear. In-depth studies on the structural and molecular biology of the STING pathway have led to the development of therapeutic strategies involving STING modulators and their targeted delivery. These strategies may effectively penetrate the blood-brain barrier (BBB) and target STING signaling in multiple central nervous system (CNS) diseases in humans. In this review, we outline both canonical and non-canonical pathways of STING activation and describe the general mechanisms and associations between STING activity and CNS diseases. Finally, we discuss the prospects for the targeted delivery and clinical application of STING agonists and inhibitors, highlighting the STING signaling pathway as a novel therapeutic target in CNS diseases.

A non-canonical cGAS-STING pathway drives cellular and organismal aging

Accumulation of cytosolic DNA has emerged as a hallmark of aging, inducing sterile inflammation. STING (Stimulator of Interferon Genes) protein translates the sensing of cytosolic DNA by cGAS (cyclic-GMP-AMP synthase) into an inflammatory response. However, the molecular mechanisms whereby cytosolic DNA-induced cGAS-STING pathway leads to aging remain poorly understood. We show that STING does not follow the canonical pathway of activation in human fibroblasts passaged (aging) in culture, senescent fibroblasts, or progeria fibroblasts (from Hutchinson Gilford Progeria Syndrome patients). Despite cytosolic DNA buildup, features of the canonical cGAS-STING pathway like increased cGAMP production, STING phosphorylation, and STING trafficking to perinuclear compartment are not observed in progeria/senescent/aging fibroblasts. Instead, STING localizes at endoplasmic reticulum, nuclear envelope, and chromatin. Despite the non-conventional STING behavior, aging/senescent/progeria cells activate inflammatory programs such as the senescence-associated secretory phenotype (SASP) and the interferon (IFN) response, in a cGAS and STING-dependent manner, revealing a non-canonical pathway in aging. Importantly, progeria/aging/senescent cells are hindered in their ability to activate the canonical cGAS-STING pathway with synthetic DNA, compared to young cells. This deficiency is rescued by activating vitamin D receptor signaling, unveiling new mechanisms regulating the cGAS-STING pathway in aging. Significantly, in HGPS, inhibition of the non-canonical cGAS-STING pathway ameliorates cellular hallmarks of aging, reduces tissue degeneration, and extends the lifespan of progeria mice. Our study reveals that a new feature of aging is the progressively reduced ability to activate the canonical cGAS-STING pathway in response to cytosolic DNA, triggering instead a non-canonical pathway that drives senescence/aging phenotypes.

Significance Statement

Our study provides novel insights into the mechanisms driving sterile inflammation in aging and progeria. We reveal a previously unrecognized characteristic of aging cells: the progressive loss of ability to activate the canonical response to foreign or self-DNA at the cytoplasm. Instead, aging, senescent, and progeria cells activate inflammatory programs via a non-conventional pathway driven by cGAS and the adaptor protein STING. Importantly, pharmacological inhibition of the non-canonical cGAS-STING pathway ameliorates cellular, tissue and organismal decline in a devastating accelerated aging disease (Hutchinson Gilford Progeria Syndrome), highlighting it as a promising therapeutic target for age-related pathologies.

Unleashing the Potential of Metal Ions in cGAS-STING Activation: Advancing Nanomaterial-Based Tumor Immunotherapy

Immunotherapy is a critical modality in cancer treatment with diverse activation pathways. In recent years, the stimulator of interferon genes (STING) signaling pathway has exhibited significant potential in tumor immunotherapy. This pathway exerts notable antitumor effects by activating innate and adaptive immunity and regulating the tumor immune microenvironment. Various metal ions have been identified as effective activators of the STING pathway and, through the design and synthesis of nanodelivery platforms, have been applied in immunotherapy as well as in combination therapies, such as chemotherapy, chemodynamic therapy, photodynamic therapy, and cancer vaccines. Metal nanomaterials showcase unique advantages in immunotherapy; however, there are still aspects that require optimization. This review systematically examines existing metal-based nanomaterials, elaborates on the mechanisms by which different metal ions activate the STING pathway, and discusses their application models in tumor combination therapies. We also provide a comparative analysis of the advantages of metal nanomaterials over other treatment methods. Our exploration highlights the broad application prospects of metal nanomaterials in cancer treatment, offering new insights and directions for the advancement of tumor immunotherapy.

The cGAS-STING pathway in HIV-1 and Mycobacterium tuberculosis coinfection

Mycobacterium tuberculosis (M. tuberculosis) infection is the most common opportunistic infection in human immunodeficiency virus-1 (HIV-1)-infected individuals, and the mutual reinforcement of these two pathogens may accelerate disease progression and lead to rapid mortality. Therefore, HIV-1/M. tuberculosis coinfection is one of the major global public health concerns. HIV-1 infection is the greatest risk factor for M. tuberculosis infection and increases the likelihood of endogenous relapse and exogenous reinfection with M. tuberculosis. Moreover, M. tuberculosis further increases HIV-1 replication and the occurrence of chronic immune activation, accelerating the progression of HIV-1 disease. Exploring the pathogenesis of HIV-1/M. tuberculosis coinfections is essential for the development of novel treatments to reduce the global burden of tuberculosis. Innate immunity, which is the first line of host immune defense, plays a critical role in resisting HIV-1 and M. tuberculosis infections. The role of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway, which is a major DNA-sensing innate immune signaling pathway, in HIV-1 infection and M. tuberculosis infection has been intensively studied. This paper reviews the role of the cGAS-STING signaling pathway in HIV-1 infection and M. tuberculosis infection and discusses the possible role of this pathway in HIV-1/M. tuberculosis coinfection to provide new insight into the pathogenesis of HIV-1/M. tuberculosis coinfection and the development of novel therapeutic strategies.

A novel biosensor for the spatiotemporal analysis of STING activation during innate immune responses to dsDNA

The cGAS-STING signalling pathway has a central role in the innate immune response to extrinsic and intrinsic sources of cytoplasmic dsDNA. At the core of this pathway is cGAS-dependent production of the intra- and extra-cellular messenger cGAMP, which activates STING and leads to IRF3-dependent expression of cytokines and interferons. Despite its relevance to viral and bacterial infections, cell death, and genome instability, the lack of specific live-cell reporters has precluded spatiotemporal analyses of cGAS-STING signalling. Here, we generate a fluorescent biosensor termed SIRF (STING-IRF3), which reports on the functional interaction between activated STING and IRF3 at the Golgi. We show that cells harbouring SIRF react in a time- and concentration-dependent manner both to STING agonists and to microenvironmental cGAMP. We demonstrate that the new biosensor is suitable for single-cell characterisation of immune responses to HSV-1 infection, mtDNA release upon apoptosis, or other sources of cytoplasmic dsDNA. Furthermore, our results indicate that STING signalling is not activated by ruptured micronuclei, suggesting that other cytosolic pattern recognition receptors underlie the interferon responses to chromosomal instability.

Regulation of the cGAS-STING Pathway

The cGAS-cGAMP-STING pathway is essential for immune defense against pathogens. Upon binding DNA, cGAS synthesizes cGAMP, which activates STING, leading to potent innate immune effector responses. However, lacking specific features to distinguish between self and nonself DNA, cGAS-STING immunity requires precise regulation to prevent aberrant activation. Several safeguard mechanisms acting on different levels have evolved to maintain tolerance to self DNA and ensure immune homeostasis under normal conditions. Disruption of these safeguards can lead to erroneous activation by self DNA, resulting in inflammatory conditions but also favorable antitumor immunity. Insights into structural and cellular checkpoints that control and terminate cGAS-STING signaling are essential for comprehending and manipulating DNA-triggered innate immunity in health and disease.

Carnosic Acid Directly Targets STING C-Terminal Tail to Improve STING-Mediated Inflammatory Diseases

cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) signaling plays a vital role in innate immunity, while its deregulation may lead to a wide variety of autoinflammatory and autoimmune diseases. It is essential to identify specifically effective lead compounds to inhibit the signaling. Herein, it is shown that carnosic acid (CA), an active ingredient of medicinal plant Rosmarinus officinalis L., specifically suppressed cGAS-STING pathway activation and the subsequent inflammatory responses. Mechanistically, CA directly bound to STING C-terminal tail (CTT), impeded the recruitment of TANK-binding kinase 1 (TBK1) onto STING signalosome, thereby blocking the phosphorylation of STING and interferon regulatory factor 3 (IRF3) nuclear translocation. Importantly, CA dramatically attenuated STING-mediated inflammatory responses in vivo. Consistently, CA has a salient ameliorative effect on autoinflammatory disease model mediated by Trex1 deficiency, via inhibition of the cGAS-STING signaling. Notably, the study further indicates that phenolic hydroxyl groups are essential for CA-mediated STING inhibitory activity. Collectively, the results thus identify STING as one of the crucial targets of CA for mediating CA's anti-inflammatory activity, and further reveal that STING CTT may be a novel promising target for drug development.

TRIM35 Negatively Regulates the cGAS-STING-Mediated Signaling Pathway by Attenuating K63-Linked Ubiquitination of STING

The cGAS-STING-mediated antiviral response plays an important role in the defense against DNA virus infection. Tripartite motif protein 35 (TRIM35), an E3 ubiquitin ligase, was identified as a positive regulator of RLR-mediated antiviral signaling in our previous study, but the effect of TRIM35 on the cGAS-STING signaling pathway has not been elucidated. Herein, we showed that TRIM35 negatively regulates the cGAS-STING signaling pathway by directly targeting STING. TRIM35 overexpression significantly inhibited the cGAMP-triggered phosphorylation of TBK1 and IRF3, attenuating IFN-β expression and the downstream antiviral response. Mechanistically, TRIM35 colocalized and directly interacted with STING in the cytoplasm. TRM35 removed K63-linked ubiquitin from STING through the C36 and C44 sites in the RING domain, which impaired the interaction of STING with TBK1 or IKKε. In addition, we demonstrated that the RING domain is a key region for the antiviral effects of TIRM35. These results collectively indicate that TRIM35 negatively regulates type I interferon (IFN-I) production by targeting and deubiquitinating STING. TRIM35 may be a potential therapeutic target for controlling viral infection.

The tumor microenvironment and dendritic cells: Developers of pioneering strategies in colorectal cancer immunotherapy?

Colorectal cancer (CRC) is the world's third most frequent cancer, and both its incidence and fatality rates are rising. Despite various therapeutic approaches, neither its mortality rate nor its recurrence frequency has decreased significantly. Additionally, conventional treatment approaches, such as chemotherapy and radiotherapy, have several side effects and risks for patients with CRC. Accordingly, the need for alternative and effective treatments for CRC patients is critical. Immunotherapy that utilizes dendritic cells (DCs) harnesses the patient's immune system to combat cancer cells effectively. DCs are the most potent antigen-presenting cells (APCs), which play a vital role in generating anti-cancer T cell responses. A significant barrier to the immune system's ability to eliminate CRC is the establishment of a potent immunosuppressive tumor milieu by malignant cells. Since DCs are frequently defective in this milieu, the tumor setting significantly reduces the effectiveness of DC-based therapy. Determining central mechanisms contributing to tumor growth by unraveling and comprehending the interaction between CRC tumor milieu and DCs may lead to new therapeutic approaches. This study aims to review DC biology and discuss its role in T-cell-mediated anti-tumor immunity, as well as to highlight the immunosuppressive effects of the CRC tumor milieu on the function of DCs. We will also highlight the tumor microenvironment (TME)-related factors that interfere with DC function as a possible therapeutic target to enhance DC-based cell therapy efficacy.

VDAC2 loss elicits tumour destruction and inflammation for cancer therapy

Tumour cells often evade immune pressure exerted by CD8+ T cells or immunotherapies through mechanisms that are largely unclear1,2. Here, using complementary in vivo and in vitro CRISPR-Cas9 genetic screens to target metabolic factors, we established voltage-dependent anion channel 2 (VDAC2) as an immune signal-dependent checkpoint that curtails interferon-γ (IFNγ)-mediated tumour destruction and inflammatory reprogramming of the tumour microenvironment. Targeting VDAC2 in tumour cells enabled IFNγ-induced cell death and cGAS-STING activation, and markedly improved anti-tumour effects and immunotherapeutic responses. Using a genome-scale genetic interaction screen, we identified BAK as the mediator of VDAC2-deficiency-induced effects. Mechanistically, IFNγ stimulation increased BIM, BID and BAK expression, with VDAC2 deficiency eliciting uncontrolled IFNγ-induced BAK activation and mitochondrial damage. Consequently, mitochondrial DNA was aberrantly released into the cytosol and triggered robust activation of cGAS-STING signalling and type I IFN response. Importantly, co-deletion of STING signalling components dampened the therapeutic effects of VDAC2 depletion in tumour cells, suggesting that targeting VDAC2 integrates CD8+ T cell- and IFNγ-mediated adaptive immunity with a tumour-intrinsic innate immune-like response. Together, our findings reveal VDAC2 as a dual-action target to overcome tumour immune evasion and establish the importance of coordinately destructing and inflaming tumours to enable efficacious cancer immunotherapy.

Avian TRIM13 attenuates antiviral innate immunity by targeting MAVS for autophagic degradation

MAVS (mitochondrial antiviral signaling protein) is a crucial adaptor in antiviral innate immunity that must be tightly regulated to maintain immune homeostasis. In this study, we identified the duck Anas platyrhynchos domesticus TRIM13 (ApdTRIM13) as a novel negative regulator of duck MAVS (ApdMAVS) that mediates the antiviral innate immune response. Upon infection with RNA viruses, ApdTRIM13 expression increased, and it specifically binds to ApdMAVS through its TM domain, facilitating the degradation of ApdMAVS in a manner independent of E3 ligase activity. Furthermore, ApdTRIM13 recruits the autophagic cargo receptor duck SQSTM1 (ApdSQSTM1), which facilitates its interaction with ApdMAVS independent of ubiquitin signaling, and subsequently delivers ApdMAVS to phagophores for degradation. Depletion of ApdSQSTM1 reduces ApdTRIM13-mediated autophagic degradation of ApdMAVS, thereby enhancing the antiviral immune response. Collectively, our findings reveal a novel mechanism by which ApdTRIM13 regulates type I interferon production by targeting ApdMAVS for selective autophagic degradation mediated by ApdSQSTM1, providing insights into the crosstalk between selective autophagy and innate immune responses in avian species.Abbreviation: 3-MA: 3-methyladenine; ATG5: autophagy related 5; baf A1: bafilomycin A1; BECN1: beclin 1; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CARD: caspase recruitment domain; co-IP: co-immunoprecipitation; DEFs: duck embryonic fibroblasts; DTMUV: duck Tembusu virus; eGFP: enhanced green fluorescent protein; hpi: hours post infection; IFIH1/MDA5: interferon induced with helicase C domain 1; IFN: interferon; IKBKE/IKKε: inhibitor of nuclear factor kappa B kinase subunit epsilon; IP: immunoprecipitation; IRF7: interferon regulatory factor 7; ISRE: interferon-stimulated response element; mAb: monoclonal antibody; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAVS: mitochondrial antiviral signaling protein; MOI: multiplicity of infection; NBR1: NBR1 autophagy cargo receptor; NFKB: nuclear factor kappa B; pAb: polyclonal antibody; poly(I:C): Polyriboinosinic polyribocytidylic acid; RIGI: RNA sensor RIG-I; RLR: RIGI-like-receptor; SeV: sendai virus; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TAX1BP1: Tax1 binding protein 1; TBK1: TANK binding kinase 1; TCID50: 50% tissue culture infectious dose; TM: tansmembrane; TOLLIP: toll interacting protein; TRIM: tripartite motif containing; UBA: ubiquitin-associated domain; Ub: ubiquitin; VSV: vesicular stomatitis virus; WT: wild type.

Virus-mediated immunosuppression in head and neck cancer

Head and neck cancer is the seventh most common cancer worldwide and its development is associated with viral infection. Human papillomavirus (HPV) is the major cause of oropharyngeal cancer and encodes three known oncoproteins, E5, E6, and E7. Epstein-Barr virus (EBV), which is the causative agent of most nasopharyngeal carcinoma, also employs several immunosuppressive mechanisms that contribute to the development of the disease. In this review, we synthesize and discuss several mechanisms used by these viruses to evade and escape the host immune system. In particular, we focus on the evasive tactics of HPV E5 which, we argue, is critical to establishing persistent infection and the development and progression of carcinomas. Importantly the mechanisms by which these viruses suppress immune responses may also play a key role in resistance to checkpoint blockade immunotherapies and thus impact patient outcomes.

ADSL-generated fumarate binds and inhibits STING to promote tumour immune evasion

Highly aggressive tumours have evolved to restrain the cGAS-STING pathway for immune evasion, and the mechanisms underlying this hijacking remain unknown. Here we demonstrate that hypoxia induces robust STING activation in normal mammary epithelial cells but not in breast cancer cells. Mechanistically, adenylosuccinate lyase (ADSL), a key metabolic enzyme in de novo purine synthesis, is highly expressed in breast cancer tissues and is phosphorylated at T350 by hypoxia-activated IKKβ. Phosphorylated ADSL interacts with STING at the endoplasmic reticulum, where ADSL-produced fumarate binds to STING, leading to the inhibition of cGAMP binding to STING, STING activation and subsequent IRF3-dependent cytokine gene expression. Disrupting the ADSL-STING association promotes STING activation and blunts tumour growth. Notably, a combination treatment with ADSL endoplasmic reticulum translocation-blocking peptide and anti-PD-1 antibody induces an additive inhibitory effect on tumour growth accompanying a substantially increased immune response. Notably, ADSL T350 phosphorylation levels are inversely correlated with levels of STING activation and predicate poor prognosis in patients with breast cancer. These findings highlight a pivotal role of the metabolite fumarate in inhibiting STING activation and uncover new strategies to improve immune-checkpoint therapy by targeting ADSL-moonlighting function-mediated STING inhibition.

Interferon regulatory factor 3 beyond innate immunity: Regulation in obesity and metabolic disorders

Interferon regulatory factor 3 (IRF3) is a transcription factor known primarily for its role in antiviral immunity via regulation of type I interferons (IFNs). Recent research has broadened its significance to encompass metabolic disorders, particularly obesity and diabetes. Obesity is characterized by chronic low-grade inflammation, insulin resistance, and metabolic dysfunction, all of which are increasingly found to be associated with immune signaling pathways. IRF3 has emerged as an important regulator in the development of obesity and type 2 diabetes (T2D), predominantly through its regulation of inflammatory cytokines production in various cells in adipose tissue. In obese individuals, IRF3 is activated in the adipocytes and adipose tissue macrophages, to promote the expression of inflammatory cytokines, thereby contributing to chronic inflammation and exacerbating insulin resistance. Moreover, IRF3 has been linked to mitochondrial dysfunction in hepatic disorders, further amplifying metabolic stress and imbalances associated with obesity. The growing evidence suggests that IRF3 is an important mediator in both immune and metabolic pathways, highlighting its potential as a target for the development of therapeutic interventions for obesity-related inflammation and metabolic dysfunction.

Human coronaviruses: activation and antagonism of innate immune responses

SUMMARYHuman coronaviruses cause a range of respiratory diseases, from the common cold (HCoV-229E, HCoV-NL63, HCoV-OC43, and SARS-CoV-2) to lethal pneumonia (SARS-CoV, SARS-CoV-2, and MERS-CoV). Coronavirus interactions with host innate immune antiviral responses are an important determinant of disease outcome. This review compares the host's innate response to different human coronaviruses. Host antiviral defenses discussed in this review include frontline defenses against respiratory viruses in the nasal epithelium, early sensing of viral infection by innate immune effectors, double-stranded RNA and stress-induced antiviral pathways, and viral antagonism of innate immune responses conferred by conserved coronavirus nonstructural proteins and genus-specific accessory proteins. The common cold coronaviruses HCoV-229E and -NL63 induce robust interferon signaling and related innate immune pathways, SARS-CoV and SARS-CoV-2 induce intermediate levels of activation, and MERS-CoV shuts down these pathways almost completely.

Insights into the roles of macrophages in Klebsiella pneumoniae infections: a comprehensive review

Klebsiella pneumoniae (KP) infections represent a significant global health challenge, characterized by severe inflammatory sequelae and escalating antimicrobial resistance. This comprehensive review elucidates the complex interplay between macrophages and KP, encompassing pathogen recognition mechanisms, macrophage activation states, cellular death pathways, and emerging immunotherapeutic strategies. We critically analyze current literature on macrophage pattern recognition receptor engagement with KP-associated molecular patterns. The review examines the spectrum of macrophage responses to KP infection, including classical M1 polarization and the newly described M(Kp) phenotype, alongside metabolic reprogramming events such as glycolytic enhancement and immune responsive gene 1 (IRG1)-itaconate upregulation. We systematically evaluate macrophage fate decisions in response to KP, including autophagy, apoptosis, pyroptosis, and necroptosis. Furthermore, we provide a critical assessment of potential future therapeutic modalities. Given the limitations of current treatment paradigms, elucidating macrophage-KP interactions is imperative. Insights gained from this analysis may inform the development of novel immunomodulatory approaches to augment conventional antimicrobial therapies, potentially transforming the clinical management of KP infections.

IDR-driven TOLLIP condensates antagonize the innate antiviral immunity by promoting the deSUMOylation of MAVS

Mitochondrial antiviral signaling protein (MAVS) is a central adaptor protein in retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling against RNA viral infection. Posttranslational modifications (PTMs) play a critical role in modulating the activity of MAVS. However, how phase separation regulates the PTMs to fine-tune MAVS activation remains to be elucidated. In this study, we identify Toll-interacting protein (TOLLIP) as a negative regulator of RLR signaling. A deficiency of TOLLIP leads to an enhanced type I interferon response upon RNA viral infection. Mice with the deletion of TOLLIP are more resistant to lethal vesicular stomatitis virus (VSV) infection than wild-type counterparts. Mechanistically, TOLLIP forms condensates that rely on its intrinsically disordered region (IDR). TOLLIP condensates interact with SENP1, promote the aggregation of SENP1, and enhance the interaction between SENP1 and MAVS, consequently leading to deSUMOylation and less aggregation of MAVS. Overall, our study reveals the critical role of TOLLIP condensation in regulating the activation of MAVS, emphasizing the complexity of MAVS activity modulation.

Protocol for detection of cGAMP-induced STING oligomerization in cultured cells

STING (stimulator of interferon genes) plays a critical role in the innate immune response, including in viral infection, cancer immunity, and several autoimmune diseases. Here, we present a protocol for detection of STING oligomerization, a critical step in STING activation. We describe steps for expressing STING in HEK293T cells, activating STING by 2'3' cyclic GMP-AMP (cGAMP) treatment, and analyzing STING oligomerization by non-reducing SDS-PAGE and blue native PAGE. This protocol is useful for studies of STING functions, regulation, and dysregulation. For complete details on the use and execution of this protocol, please refer to Liu and Manley.1.

ArfGAP2 promotes STING proton channel activity, cytokine transit, and autoinflammation

Stimulator of interferon genes (STING) transmits signals downstream of the cytosolic DNA sensor cyclic guanosine monophosphate-AMP synthase (cGAS), leading to transcriptional upregulation of cytokines. However, components of the STING signaling pathway, such as IRF3 and IFNAR1, are not essential for autoinflammatory disease in STING gain-of-function (STING-associated vasculopathy with onset in infancy [SAVI]) mice. Recent discoveries revealed that STING also functions as a proton channel that deacidifies the Golgi apparatus. Because pH impacts Golgi enzyme activity, protein maturation, and trafficking, we hypothesized that STING proton channel activity influences multiple Golgi functions. Here, we show that STING-mediated proton efflux non-transcriptionally regulates Golgi trafficking of protein cargos. This process requires the Golgi-associated protein ArfGAP2, a cell-type-specific dual regulator of STING-mediated proton efflux and signaling. Deletion of ArfGAP2 in hematopoietic and endothelial cells markedly reduces STING-mediated cytokine and chemokine secretion, immune cell activation, and autoinflammatory pathology in SAVI mice. Thus, ArfGAP2 facilitates STING-mediated signaling and cytokine release in hematopoietic cells, significantly contributing to autoinflammatory disease pathogenesis.

Cytosolic nucleic acid sensing as driver of critical illness: mechanisms and advances in therapy

Nucleic acids from both self- and non-self-sources act as vital danger signals that trigger immune responses. Critical illnesses such as acute respiratory distress syndrome, sepsis, trauma and ischemia lead to the aberrant cytosolic accumulation and massive release of nucleic acids that are detected by antiviral innate immune receptors in the endosome or cytosol. Activation of receptors for deoxyribonucleic acids and ribonucleic acids triggers inflammation, a major contributor to morbidity and mortality in critically ill patients. In the past decade, there has been growing recognition of the therapeutic potential of targeting nucleic acid sensing in critical care. This review summarizes current knowledge of nucleic acid sensing in acute respiratory distress syndrome, sepsis, trauma and ischemia. Given the extensive research on nucleic acid sensing in common pathological conditions like cancer, autoimmune disorders, metabolic disorders and aging, we provide a comprehensive summary of nucleic acid sensing beyond critical illness to offer insights that may inform its role in critical conditions. Additionally, we discuss potential therapeutic strategies that specifically target nucleic acid sensing. By examining nucleic acid sources, sensor activation and function, as well as the impact of regulating these pathways across various acute diseases, we highlight the driving role of nucleic acid sensing in critical illness.