STING is an endoplasmic reticulum adaptor that facilitates innate immune signalling. Nature. 2008;455:674-678. [PMID: 18724357 PMCID: PMC2804933 DOI: 10.1038/nature07317]

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

Zika virus NS4B protein targets TANK-binding kinase 1 and inhibits type I interferon production

BACKGROUND

During viral infections, nucleic acid sensing by intracellular receptors can trigger type I interferon (IFN-I) production, key mediators in antiviral innate immunity. However, many flaviviruses use non-structural proteins to evade immune sensing favoring their survival. These mechanisms remain poorly characterized. Here, we studied the role of Zika virus (ZIKV) NS4B protein in the inhibition of IFN-I induction pathway and its biophysical interaction with host proteins.

METHODS

Using different cell-based assays, we studied the effect of ZIKV NS4B in the activation of interferon regulatory factors (IRFs), NF-κB, cytokines secretion and the expression of interferon-stimulating genes (ISG). We also analyzed the in vitro interaction between recombinant ZIKV NS4B and TANK-binding kinase 1 (TBK1) using surface plasmon resonance (SPR).

RESULTS

Transfection assays showed that ZIKV NS4B inhibits IRFs activation involved in different nucleic acid sensing cascades. Cells expressing NS4B secreted lower levels of IFN-β and IL-6. Furthermore, early induction of ISGs was also restricted by ZIKV NS4B. For the first time, we demonstrate by SPR assays that TBK1, a critical component in IFN-I production pathway, binds directly to ZIKV NS4B (KD of 3.7 × 10-6 M). In addition, we show that the N-terminal region of NS4B is directly involved in this interaction.

CONCLUSIONS

Altogether, our results strongly support that ZIKV NS4B affects nucleic acid sensing cascades and disrupts the TBK1/IRF3 axis, leading to an impairment of IFN-β production.

SIGNIFICANCE

This study provides the first biophysical data of the interaction between ZIKV NS4B and TBK1, and highlights the role of ZIKV NS4B in evading the early innate immune response.

SARS-CoV-2 nonstructural protein 6 triggers endoplasmic reticulum stress-induced autophagy to degrade STING1

ABBREVIATIONS

aa: amino acid; ATF6: activating transcription factor 6; ATG5: autophagy related 5; CCPG1: cell cycle progression 1; CFTR: CF transmembrane conductance regulator; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; CHX: cycloheximide; Co-IP: co-immunoprecipitation; CQ: chloroquine; EIF2A/eIF2α: eukaryotic translation initiation factor 2A; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ER: endoplasmic reticulum; ERN1/IRE1: endoplasmic reticulum to nucleus signaling 1; GFP: green fluorescent protein; HSPA5/GRP78: heat shock protein family A (Hsp70) member 5; HSV-1: herpes simplex virus type 1; IFIT1: interferon induced protein with tetratricopeptide repeats 1; IFNB1/IFN-β: interferon beta 1; IRF3: interferon regulatory factor 3; ISG15: ISG15 ubiquitin like modifier; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; MAVS: mitochondrial antiviral signaling protein; MOI: multiplicity of infection; NFKB/NF-κB: nuclear factor kappa B; NSP6: non-structural protein 6; Δ106-108: deletion of amino acids 106-108 in NSP6 of SARS-CoV-2; Δ105-107: deletion of amino acids 105-107 in NSP6 of SARS-CoV-2; RETREG1/FAM134B: reticulophagy regulator 1; RIGI/DDX58: RNA sensor RIG-I; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1.

TBK1-stabilized ZNF268a recruits SETD4 to methylate TBK1 for efficient interferon signaling

Sufficient activation of interferon signaling is critical for the host to fight against invading viruses, in which post-translational modifications have been demonstrated to play a pivotal role. Here, we demonstrate that the human KRAB-zinc finger protein ZNF268a is essential for virus-induced interferon signaling. We find that cytoplasmic ZNF268a is constantly degraded by lysosome and thus remains low expressed in resting cell cytoplasm. Upon viral infection, TBK1 interacts with cytosolic ZNF268a to catalyze the phosphorylation of Serine 178 of ZNF268a, which prevents the degradation of ZNF268a, resulting in the stabilization and accumulation of ZNF268a in the cytoplasm. Furthermore, we provide evidence that stabilized ZNF268a recruits the lysine methyltransferase SETD4 to TBK1 to induce the mono-methylation of TBK1 on lysine 607, which is critical for the assembly of the TBK1 signaling complex. Notably, ZNF268 S178 is conserved among higher primates but absent in rodents. Meanwhile, rodent TBK1 607th aa happens to be replaced by arginine, possibly indicating a species-specific role of ZNF268a in regulating TBK1 during evolution. These findings reveal novel functions of ZNF268a and SETD4 in regulating antiviral interferon signaling.

At the Crossroads of the cGAS-cGAMP-STING Pathway and the DNA Damage Response: Implications for Cancer Progression and Treatment

The evolutionary conserved DNA-sensing cGAS-STING innate immunity pathway represents one of the most important cytosolic DNA-sensing systems that is activated in response to viral invasion and/or damage to the integrity of the nuclear envelope. The key outcome of this pathway is the production of interferon, which subsequently stimulates the transcription of hundreds of genes. In oncology, the situation is complex because this pathway may serve either anti- or pro-oncogenic roles, depending on context. The prevailing understanding is that when the innate immune response is activated by sensing cytosolic DNA, such as DNA released from ruptured micronuclei, it results in the production of interferon, which attracts cytotoxic cells to destroy tumors. However, in tumor cells that have adjusted to significant chromosomal instability, particularly in relapsed, treatment-resistant cancers, the cGAS-STING pathway often supports cancer progression, fostering the epithelial-to-mesenchymal transition (EMT). Here, we review this intricate pathway in terms of its association with cancer progression, giving special attention to pancreatic ductal adenocarcinoma and gliomas. As the development of new cGAS-STING-modulating small molecules and immunotherapies such as oncolytic viruses involves serious challenges, we highlight several recent fundamental discoveries, such as the proton-channeling function of STING. These discoveries may serve as guiding lights for potential pharmacological advancements.

Alternative splicing variants of stimulator of interferon genes (STING) from Asian seabass (Lates calcarifer) and their immune response against red spotted grouper nervous necrosis virus (RGNNV)

The Stimulator of Interferon Genes (STING, also known as MITA/ERYS/MPYS) is an adaptor molecule that plays a crucial role in the RLR pathway and responds to DNA and RNA viruses. In the present study, we have identified two novel isoforms of STING (the canonical form named as LcSTINGa and its alternative splicing isoform named as LcSTINGb) from teleost Lates calcarifer. LcSTINGa has an ORF of 1230 bp, encoding a 409 amino acid protein, while its alternative splicing variant, LcSTINGb, features an ORF of 987 bp, encoding 328 amino acids. LcSTINGa is predicted to contain four transmembrane helices, whereas LcSTINGb has only two. The Lates STING protein showed about 86.85% identity with Perca flavescens, 86.45% with Seriola and 39.51% with Homo sapiens. The tissue distribution studies revealed that the STING variants were constitutively expressed in all the tissues examined, with the highest expression in blood. In-vivo upregulation of LcSTINGa and LcSTINGb mRNA following immune challenge with poly (I:C), Red-spotted grouper nervous necrosis virus (RGNNV) and zymosan A suggests its significance in the immune response.

Staphylococcus aureus planktonic but not biofilm environment induces an IFN-β macrophage immune response via the STING/IRF3 pathway

Chronic implant-related bone infections are a severe complication in orthopaedic surgery. Biofilm formation on the implant impairs the immune response, leading to bacterial persistence. In a previous study, we found that Staphylococcus aureus (SA) induced interferon regulatory factor 3 (IRF3) activation and Ifnb expression only in its planktonic form but not in the biofilm. The aim of this study was to clarify the role of the stimulator of interferon genes (STING) in this process. We treated RAW 264.7 macrophages with conditioned media (CM) generated from planktonic or biofilm cultured SA in combination with agonists or inhibitors of the cyclic GMP-AMP synthase (cGAS)/STING pathway. We further evaluated bacterial gene expression of planktonic and biofilm SA to identify potential mediators. STING inhibition resulted in the loss of IRF3 activation and Ifnb induction in SA planktonic CM, whereas STING activation induced an IRF3 dependent IFN-β response in SA biofilm CM. The expression levels of virulence-associated genes decreased during biofilm formation, but genes associated with cyclic dinucleotide (CDN) synthesis did not correlate with Ifnb induction. We further observed that cGAS contributed to Ifnb induction by SA planktonic CM, although cGAS activation was not sufficient to induce Ifnb expression in SA biofilm CM. Our data indicate that the different degrees of virulence associated with SA planktonic and biofilm environments result in an altered induction of the IRF3 mediated IFN-β response via the STING pathway. This finding suggests that the STING/IRF3/IFN-β axis is a potential candidate as an immunotherapeutic target for implant-related bone infections.

Mitochondrial DNA Sensing Pathogen Recognition Receptors in Systemic Sclerosis Associated Interstitial Lung Disease: A Review

Purpose of the review

Systemic sclerosis (SSc) is a condition of dermal and visceral scar formation characterized by immune dysregulation and inflammatory fibrosis. Approximately 90% of SSc patients develop interstitial lung disease (ILD), and it is the leading cause of morbidity and mortality. Further understanding of immune-mediated fibroproliferative mechanisms has the potential to catalyze novel treatment approaches in this difficult to treat disease.

Recent findings

Recent advances have demonstrated the critical role of aberrant innate immune activation mediated by mitochondrial DNA (mtDNA) through interactions with toll-like receptor 9 (TLR9) and cytosolic cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS).

Summary

In this review, we will discuss how the nature of the mtDNA, whether oxidized or mutated, and its mechanism of release, either intracellularly or extracellularly, can amplify fibrogenesis by activating TLR9 and cGAS, and the novel insights gained by interrogating these signaling pathways. Because the scope of this review is intended to generate hypotheses for future research, we conclude our discussion with several important unanswered questions.

Identification of TMEM53 as a novel SADS-CoV restriction factor that targets viral RNA-dependent RNA polymerase

ABSTRACTZoonotic transmission of coronaviruses (CoVs) poses a serious public health threat. Swine acute diarrhea syndrome coronavirus (SADS-CoV), originating from a bat HKU2-related CoV, causes devastating swine diseases and poses a high risk of spillover to humans. Currently, licensed therapeutics that can prevent potential human outbreaks are unavailable. Identifying the cellular proteins that restrict viral infection is imperative for developing effective interventions and therapeutics. We utilized a large-scale human cDNA screening and identified transmembrane protein 53 (TMEM53) as a novel cell-intrinsic SADS-CoV restriction factor. The inhibitory effect of TMEM53 on SADS-CoV infection was found to be independent of canonical type I interferon responses. Instead, TMEM53 interacts with non-structural protein 12 (NSP12) and disrupts viral RNA-dependent RNA polymerase (RdRp) complex assembly by interrupting NSP8-NSP12 interaction, thus suppressing viral RdRp activity and RNA synthesis. Deleting the transmembrane domain of TMEM53 resulted in the abrogation of TMEM53-NSP12 interaction and TMEM53 antiviral activity. Importantly, TMEM53 exhibited broad antiviral activity against multiple HKU2-related CoVs. Our findings reveal a novel role of TMEM53 in SADS-CoV restriction and pave the way to host-directed therapeutics against HKU2-related CoV infection.

Anti-triple-negative breast cancer metastasis efficacy and molecular mechanism of the STING agonist for innate immune pathway

BACKGROUND

With high recurrence and metastatic rates, triple-negative breast cancer (TNBC) has few therapy choices. The innate immune stimulator of interferon genes protein (STING) pathway has emerged as a critical foundation for improving anticancer immunotherapy. Although 2',3'-cGAMP has been shown to have therapeutic potential as a STING agonist in subcutaneous solid tumour treatments in mice, the effect of cGAMP in metastatic malignancies has received less attention.

METHODS

Bioluminescence imaging technology was applied to monitor TNBC tumour cell metastasis in living mice. Serum biochemical test and blood routine examination of mice were used to demonstrate cGAMP administration had no toxicity. The activation of DCs and CD8+ T cells was demonstrated by flow cytometry. The pharmacological mechanism of cGAMP for suppressing breast tumour metastasis was also explored.

RESULTS

cGAMP treatment substantially suppressed tumour development and metastasis without adverse effects. cGAMP activated the cGAS-STING-IRF3 pathway, which modified the tumour immune milieu to reverse the Epithelial-Mesenchymal Transition (EMT) and PI3K/AKT pathways and prevent tumour metastasis. It was postulated and proven that cGAMP had a pharmacological mechanism for reducing breast tumour metastasis.

CONCLUSION

The findings suggest that cGAMP could be useful in the immunotherapy of immune-insensitive metastatic breast cancer.

STING activation in TET2-mutated hematopoietic stem/progenitor cells contributes to the increased self-renewal and neoplastic transformation

Somatic loss-of-function mutations of the dioxygenase Ten-eleven translocation-2 (TET2) occur frequently in individuals with clonal hematopoiesis (CH) and acute myeloid leukemia (AML). These common hematopoietic disorders can be recapitulated in mouse models. However, the underlying mechanisms by which the deficiency in TET2 promotes these disorders remain unclear. Here we show that the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) pathway is activated to mediate the effect of TET2 deficiency in dysregulated hematopoiesis in mouse models. DNA damage arising in Tet2-deficient hematopoietic stem/progenitor cells (HSPCs) leads to activation of the cGAS-STING pathway which in turn promotes the enhanced self-renewal and development of CH. Notably, both pharmacological inhibition and genetic deletion of STING suppresses Tet2 mutation-induced aberrant hematopoiesis. In patient-derived xenograft (PDX) models, STING inhibition specifically attenuates the proliferation of leukemia cells from TET2-mutated individuals. These observations suggest that the development of CH associated with TET2 mutations is powered through chronic inflammation dependent on the activated cGAS-STING pathway and that STING may represent a potential target for intervention of relevant hematopoietic diseases.

Chitosan-based nano-micelles for potential anti-tumor immunotherapy: Synergistic effect of cGAS-STING signaling pathway activation and tumor antigen absorption

Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway is an essential DNA-sensing pathway to regulate the innate and adaptive immune response, which plays an important role in tumor immunotherapy. Although the STING agonists can be used, they are limited by their inability to target immune cells and systemic immunotoxicity, calling for novel strategies to accurately and effectively activate the cGAS-STING signaling pathway. Herein, mannose-modified stearic acid-grafted chitosan (M-CS-SA) micelles with the ability to activate the cGAS-STING signaling pathway and absorb tumor antigens were constructed. The chitosan-based nano-micelles showed valid dendritic cell (DCs) targeting and could escape from lysosomes leading to the activation of the cGAS-STING signaling pathway and the maturation of DCs. In addition, a combinatorial therapy was presented based on the programmed administration of oxaliplatin and M-CS-SA. M-CS-SA adsorbed tumor antigens released by chemotherapy to construct an autologous tumor vaccine and built a comprehensive antitumor immune response. In vivo, the combinatorial therapy achieved a tumor inhibition rate of 76.31 % at the oxaliplatin dose of 5 mg/kg and M-CS-SA dose of 15 mg/kg, and increased the CD3+ CD8+ T cell infiltration. This work demonstrated that M-CS-SA and its co-treatment with oxaliplatin showed great potential in tumor immunotherapy.

Smyd3 negatively regulates the anti-viral pathway by promoting TAK1 degradation in teleost fish

IMPORTANCE

In this study, we have found that the existence of Smyd3 promoted the replication of SCRV. Additionally, we report that Smyd3 negatively regulates the NF-κB and IRF3 signaling pathway by facilitating the degradation of TAK1 in fish. Our findings suggest that Smyd3 interacts with TAK1. Further investigations have revealed that Smyd3 specifically mediates K48-linked ubiquitination of TAK1 and enhances TAK1 degradation, resulting in a significant inhibition of the NF-κB and IRF3 signaling pathway. These results not only contribute to the advancement of fish anti-viral immunity but also provide new evidence for understanding the mechanism of TAK1 in mammals.

Membrane traffic governs the STING inflammatory signalling

The cGAS-STING innate immune pathway has recently emerged as a critical driver of inflammation in a variety of settings, such as virus infection, cellular stress and tissue damage. The pathway detects microbial and host-derived double-stranded DNA (dsDNA) in the cytosol, and triggers the production of the type I interferons through the activation of IRF3. The detailed mechanistic and biochemical understanding of the pathway has enabled the development of pharmacological agents for the treatment of chronic inflammation and cancer. STING is an endoplasmic reticulum (ER)-localized transmembrane protein. Upon emergence of cytosolic dsDNA, STING exits the ER and migrates sequentially to the Golgi, recycling endosomes and lysosomes. Importantly, the intracellular translocation of STING is essential for the activation and inactivation of the STING signalling. In this review, I summarize the recent insights into the regulators of the membrane traffic of STING and STING-associated autoinflammatory diseases.

Small molecule modulators of immune pattern recognition receptors

Pattern recognition receptors (PRRs) represent a re-emerging class of therapeutic targets for vaccine adjuvants, inflammatory diseases and cancer. In this review article, we summarize exciting developments in discovery and characterization of small molecule PRR modulators, focusing on Toll-like receptors (TLRs), NOD-like receptors (NLRs) and the cGAS-STING pathway. We also highlight PRRs that are currently lacking small molecule modulators and opportunities for chemical biology and therapeutic discovery.

Regulation of STING activity in DNA sensing by ISG15 modification

Sensing of human immunodeficiency virus type 1 (HIV-1) DNA is mediated by the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling axis. Signal transduction and regulation of this cascade is achieved by post-translational modifications. Here we show that cGAS-STING-dependent HIV-1 sensing requires interferon-stimulated gene 15 (ISG15). ISG15 deficiency inhibits STING-dependent sensing of HIV-1 and STING agonist-induced antiviral response. Upon external stimuli, STING undergoes ISGylation at residues K224, K236, K289, K347, K338, and K370. Inhibition of STING ISGylation at K289 suppresses STING-mediated type Ⅰ interferon induction by inhibiting its oligomerization. Of note, removal of STING ISGylation alleviates gain-of-function phenotype in STING-associated vasculopathy with onset in infancy (SAVI). Molecular modeling suggests that ISGylation of K289 is an important regulator of oligomerization. Taken together, our data demonstrate that ISGylation at K289 is crucial for STING activation and represents an important regulatory step in DNA sensing of viruses and autoimmune responses.

cGAS-STING signaling in the tumor microenvironment

The cGAS-STING signaling is an important pathway involved in the regulation of tumor microenvironment, which affects many cellular functions including immune activation. Its role in combating tumor progression is widely recognized, especially with its function in inducing innate and adaptive immune responses, on which many immunotherapies have been developed. However, a growing number of findings also suggest a diversity of its roles in shaping tumor microenvironment, including functions that promote tumor progression. Here, we summarize the functions of the cGAS-STING signaling in tumor microenvironment to maintain tumor survival and proliferation through facilitating the forming of an immunosuppressive tumor microenvironment and discuss the current advances of STING-related immunotherapies.

Chromosomal Instability-Driven Cancer Progression: Interplay with the Tumour Microenvironment and Therapeutic Strategies

Chromosomal instability (CIN) is a prevalent characteristic of solid tumours and haematological malignancies. CIN results in an increased frequency of chromosome mis-segregation events, thus yielding numerical and structural copy number alterations, a state also known as aneuploidy. CIN is associated with increased chances of tumour recurrence, metastasis, and acquisition of resistance to therapeutic interventions, and this is a dismal prognosis. In this review, we delve into the interplay between CIN and cancer, with a focus on its impact on the tumour microenvironment-a driving force behind metastasis. We discuss the potential therapeutic avenues that have resulted from these insights and underscore their crucial role in shaping innovative strategies for cancer treatment.

PTK2B promotes TBK1 and STING oligomerization and enhances the STING-TBK1 signaling

TANK-binding kinase 1 (TBK1) is a key kinase in regulating antiviral innate immune responses. While the oligomerization of TBK1 is critical for its full activation, the molecular mechanism of how TBK1 forms oligomers remains unclear. Here, we show that protein tyrosine kinase 2 beta (PTK2B) acts as a TBK1-interacting protein and regulates TBK1 oligomerization. Functional assays reveal that PTK2B depletion reduces antiviral signaling in mouse embryonic fibroblasts, macrophages and dendritic cells, and genetic experiments show that Ptk2b-deficient mice are more susceptible to viral infection than control mice. Mechanistically, we demonstrate that PTK2B directly phosphorylates residue Tyr591 of TBK1, which increases TBK1 oligomerization and activation. In addition, we find that PTK2B also interacts with the stimulator of interferon genes (STING) and can promote its oligomerization in a kinase-independent manner. Collectively, PTK2B enhances the oligomerization of TBK1 and STING via different mechanisms, subsequently regulating STING-TBK1 activation to ensure efficient antiviral innate immune responses.

Arabinose- and xylose-modified analogs of 2',3'-cGAMP act as STING agonists

Stimulator of interferon genes (STING) agonists are promising candidates for vaccine adjuvants and antitumor immune stimulants. The most potent natural agonist of STING, 2',3'-cyclic GMP-AMP (2',3'-cGAMP), is subject to nuclease-mediated inherent metabolic instability, thereby placing limits on its clinical efficacy. Here, we report on a new class of chemically synthesized sugar-modified analogs of 2',3'-cGAMP containing arabinose and xylose sugar derivatives that bind mouse and human STING alleles with high affinity. The co-crystal structures demonstrate that such analogs act as 2',3'-cGAMP mimetics that induce the "closed" conformation of human STING. These analogs show significant resistance to hydrolysis mediated by ENPP1 and increased stability in human serum, while retaining similar potency as 2',3'-cGAMP at inducing IFN-β secretion from human THP1 cells. The arabinose- and xylose-modified 2',3'-cGAMP analogs open a new strategy for overcoming the inherent nuclease-mediated vulnerability of natural ribose cyclic nucleotides, with the additional benefit of high translational potential as cancer therapeutics and vaccine adjuvants.

Analysis of structure-activity relationship of indol-3-yl-N-phenylcarbamic amides as potent STING inhibitors

A structure-activity relationship (SAR) study of stimulator of interferon gene (STING) inhibition was performed using a series of indol-3-yl-N-phenylcarbamic amides and indol-2-yl-N-phenylcarbamic amides. Among these analogs, compounds 10, 13, 15, 19, and 21 inhibited the phosphorylation of STING and interferon regulatory factor 3 (IRF3) to a greater extent than the reference compound, H-151. All five analogs showed stronger STING inhibition than H-151 on the 2',3'-cyclic GMP-AMP-induced expression of interferon regulatory factors (IRFs) in a STINGR232 knock-in THP-1 reporter cell line. The half-maximal inhibitory concentration of the most potent compound, 21, was 11.5 nM. The molecular docking analysis of compound 21 and STING combined with the SAR study suggested that the meta- and para-positions of the benzene ring of the phenylcarbamic amide moiety could be structurally modified by introducing halides or alkyl substituents.

Suppression of Innate Immunity by the Hepatitis C Virus (HCV): Revisiting the Specificity of Host-Virus Interactive Pathways

The hepatitis C virus (HCV) is a major causative agent of hepatitis that may also lead to liver cancer and lymphomas. Chronic hepatitis C affects an estimated 2.4 million people in the USA alone. As the sole member of the genus Hepacivirus within the Flaviviridae family, HCV encodes a single-stranded positive-sense RNA genome that is translated into a single large polypeptide, which is then proteolytically processed to yield the individual viral proteins, all of which are necessary for optimal viral infection. However, cellular innate immunity, such as type-I interferon (IFN), promptly thwarts the replication of viruses and other pathogens, which forms the basis of the use of conjugated IFN-alpha in chronic hepatitis C management. As a countermeasure, HCV suppresses this form of immunity by enlisting diverse gene products, such as HCV protease(s), whose primary role is to process the large viral polyprotein into individual proteins of specific function. The exact number of HCV immune suppressors and the specificity and molecular mechanism of their action have remained unclear. Nonetheless, the evasion of host immunity promotes HCV pathogenesis, chronic infection, and carcinogenesis. Here, the known and putative HCV-encoded suppressors of innate immunity have been reviewed and analyzed, with a predominant emphasis on the molecular mechanisms. Clinically, the knowledge should aid in rational interventions and the management of HCV infection, particularly in chronic hepatitis.

Mechanism and therapeutic potential of targeting cGAS-STING signaling in neurological disorders

DNA sensing is a pivotal component of the innate immune system that is responsible for detecting mislocalized DNA and triggering downstream inflammatory pathways. Among the DNA sensors, cyclic GMP-AMP synthase (cGAS) is a primary player in detecting cytosolic DNA, including foreign DNA from pathogens and self-DNA released during cellular damage, culminating in a type I interferon (IFN-I) response through stimulator of interferon genes (STING) activation. IFN-I cytokines are essential in mediating neuroinflammation, which is widely observed in CNS injury, neurodegeneration, and aging, suggesting an upstream role for the cGAS DNA sensing pathway. In this review, we summarize the latest developments on the cGAS-STING DNA-driven immune response in various neurological diseases and conditions. Our review covers the current understanding of the molecular mechanisms of cGAS activation and highlights cGAS-STING signaling in various cell types of central and peripheral nervous systems, such as resident brain immune cells, neurons, and glial cells. We then discuss the role of cGAS-STING signaling in different neurodegenerative conditions, including tauopathies, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, as well as aging and senescence. Finally, we lay out the current advancements in research and development of cGAS inhibitors and assess the prospects of targeting cGAS and STING as therapeutic strategies for a wide spectrum of neurological diseases.

Lysosomes in senescence and aging

Dysfunction of lysosomes, the primary hydrolytic organelles in animal cells, is frequently associated with aging and age-related diseases. At the cellular level, lysosomal dysfunction is strongly linked to cellular senescence or the induction of cell death pathways. However, the precise mechanisms by which lysosomal dysfunction participates in these various cellular or organismal phenotypes have remained elusive. The ability of lysosomes to degrade diverse macromolecules including damaged proteins and organelles puts lysosomes at the center of multiple cellular stress responses. Lysosomal activity is tightly regulated by many coordinated cellular processes including pathways that function inside and outside of the organelle. Here, we collectively classify these coordinated pathways as the lysosomal processing and adaptation system (LYPAS). We review evidence that the LYPAS is upregulated by diverse cellular stresses, its adaptability regulates senescence and cell death decisions, and it can form the basis for therapeutic manipulation for a wide range of age-related diseases and potentially for aging itself.

Seneca Valley Virus Degrades STING via PERK and ATF6-Mediated Reticulophagy

Seneca Valley Virus (SVV), a member of the Picornaviridae family, is an emerging porcine virus that can cause vesicular disease in pigs. However, the immune evasion mechanism of SVV remains unclear, as does its interaction with other pathways. STING (Stimulator of interferon genes) is typically recognized as a critical factor in innate immune responses to DNA virus infection, but its role during SVV infection remains poorly understood. In the present study, we observed that STING was degraded in SVV-infected PK-15 cells, and SVV replication in the cells was affected when STING was knockdown or overexpressed. The STING degradation observed was blocked when the SVV-induced autophagy was inhibited by using autophagy inhibitors (Chloroquine, Bafilomycin A1) or knockdown of autophagy related gene 5 (ATG5), suggesting that SVV-induced autophagy is responsible for STING degradation. Furthermore, the STING degradation was inhibited when reticulophagy regulator 1 (FAM134B), a reticulophagy related receptor, was knocked down, indicating that SVV infection induces STING degradation via reticulophagy. Further study showed that in eukaryotic translation initiation factor 2 alpha kinase 3 (PERK)/activating transcription factor 6 (ATF6) deficient cells, SVV infection failed to induce reticulophagy-medaited STING degradation, indicating that SVV infection caused STING degradation via PERK/ATF6-mediated reticulophagy. Notably, blocking reticulophagy effectively hindered SVV replication. Overall, our study suggested that SVV infection resulted in STING degradation via PERK and ATF6-mediated reticulophagy, which may be an immune escape strategy of SVV. This finding improves the understanding of the intricate interplay between viruses and their hosts and provides a novel strategy for the development of novel antiviral drugs.

TAK1 is an essential kinase for STING trafficking

The translocation of stimulator of interferon genes (STING) from the endoplasmic reticulum (ER) to the ER-Golgi intermediate compartment (ERGIC) enables its activation. However, the mechanism underlying the regulation of STING exit from the ER remains elusive. Here, we found that STING induces the activation of transforming growth factor beta-activated kinase 1 (TAK1) prior to STING trafficking in a TAK1 binding protein 1 (TAB1)-dependent manner. Intriguingly, activated TAK1 directly mediates STING phosphorylation on serine 355, which facilitates its interaction with STING ER exit protein (STEEP) and thereby promotes its oligomerization and translocation to the ERGIC for subsequent activation. Importantly, activation of TAK1 by monophosphoryl lipid A, a TLR4 agonist, boosts cGAMP-induced antitumor immunity dependent on STING phosphorylation in a mouse allograft tumor model. Taken together, TAK1 was identified as a checkpoint for STING activation by promoting its trafficking, providing a basis for combinatory tumor immunotherapy and intervention in STING-related diseases.

Inactivation of the DNA-sensing pathway facilitates oncolytic herpes simplex virus inhibition of pancreatic ductal adenocarcinoma growth

Oncolytic viruses are a new class of therapeutic agents for the treatment of cancer that have shown promising results in clinical trials. Oncolytic virus-mediated tumor rejection is highly dependent on viral replication in tumor cells to induce cell death. However, the antiviral immune response of tumor cells limits the replication capacity of oncolytic viruses. We hypothesized that inhibition of the antiviral immune response in infected cells would enhance the antitumor effect. Here, we confirmed that ablation of the key adaptor protein of cellular immunity, STING, significantly suppressed the antiviral immune response and promoted oncolytic herpes simplex virus-1 (oHSV1) proliferation in tumor cells. In a murine pancreatic ductal adenocarcinoma (PDAC) model, oHSV1 enhanced tumor suppression and prolonged the survival of mice in the absence of STING. On this basis, we further found that the TBK1 inhibitor can also significantly enhance the tumor-control ability of oHSV1. Our studies provide a novel strategy for oncolytic virus therapy by inhibiting the intrinsic antiviral response in solid tumors to improve antitumor efficacy.

'From R-lupus to cancer': Reviewing the role of R-loops in innate immune responses

Cells possess an inherent and evolutionarily conserved ability to detect and respond to the presence of foreign and pathological 'self' nucleic acids. The result is the stimulation of innate immune responses, signalling to the host immune system that defence mechanisms are necessary to protect the organism. To date, there is a vast body of literature describing innate immune responses to various nucleic acid species, including dsDNA, ssDNA and ssRNA etc., however, there is limited information available on responses to R-loops. R-loops are 3-stranded nucleic acid structures that form during transcription, upon DNA damage and in various other settings. Emerging evidence suggests that innate immune responses may also exist for the detection of R-loop related nucleic acid structures, implicating R-loops as drivers of inflammatory states. In this review, we aim to summarise the evidence indicating that R-loops are immunogenic species that can trigger innate immune responses in physiological and pathological settings and discuss the implications of this in the study of various diseases and therapeutic development.

Characterization of STING from common carp (Cyprinus carpio L.) involved in spring viremia of carp virus infection

Stimulator of interferon genes (STING) serve as an endoplasmic reticulum (ER) protein and modulates innate immune responses to viral contagion. Most investigations involving teleost STING antiviral immunity have examined DNA viruses. Therefore, fish STING signaling events against RNA viruses require additional exploration. Here, common carp STING (named CcSTING) was cloned and characterized. The bioinformatics analyses of CcSTING showed evolutionary conservations and were most closely related to other cyprinid STINGs. Immunofluorescence staining discovered that the CcSTING was chiefly placed in the cytoplasm, specifically within the ER. CcSTING was ubiquitously generated in all analyzed organs, with especially strong expression in the gills and head kidney. Spring viremia of carp virus (SVCV) stimulation and poly(I:C) infection induced the generation of CcSTING in immune-associated organs, as well as in peripheral blood leukocytes. Additional investigations revealed that CcSTING overexpression strongly suppressed SVCV replication in EPC cells. Mechanistically, CcSTING enhanced IFN-1 and ISGs expression following SVCV infection. CcSTING also substantially increased both IFN and NF-κB promoter luciferase activity via a dosage-dependent fashion. Lastly, CcSTING significantly up-regulated both TBK1 and p65 phosphorylation. Collectively, these findings demonstrated the critical role and underlying mechanism of fish STING in response to RNA virus.

Reovirus combined with a STING agonist enhances anti-tumor immunity in a mouse model of colorectal cancer

Reovirus, a naturally occurring oncolytic virus, initiates the lysis of tumor cells while simultaneously releasing tumor antigens or proapoptotic cytokines in the tumor microenvironment to augment anticancer immunity. However, reovirus has developed a strategy to evade antiviral immunity via its inhibitory effect on interferon production, which negatively affects the induction of antitumor immune responses. The mammalian adaptor protein Stimulator of Interferon Genes (STING) was identified as a key regulator that orchestrates immune responses by sensing cytosolic DNA derived from pathogens or tumors, resulting in the production of type I interferon. Recent studies reported the role of STING in innate immune responses to RNA viruses leading to the restriction of RNA virus replication. In the current study, we found that reovirus had a reciprocal reaction with a STING agonist regarding type I interferon responses in vitro; however, we found that the combination of reovirus and STING agonist enhanced anti-tumor immunity by enhancing cytotoxic T cell trafficking into tumors, leading to significant tumor regression and survival benefit in a syngeneic colorectal cancer model. Our data indicate the combination of reovirus and a STING agonist to enhance inflammation in the tumor microenvironment might be a strategy to improve oncolytic reovirus immunotherapy.

ARF1 prevents aberrant type I interferon induction by regulating STING activation and recycling

Type I interferon (IFN) signalling is tightly controlled. Upon recognition of DNA by cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING) translocates along the endoplasmic reticulum (ER)-Golgi axis to induce IFN signalling. Termination is achieved through autophagic degradation or recycling of STING by retrograde Golgi-to-ER transport. Here, we identify the GTPase ADP-ribosylation factor 1 (ARF1) as a crucial negative regulator of cGAS-STING signalling. Heterozygous ARF1 missense mutations cause a previously unrecognized type I interferonopathy associated with enhanced IFN-stimulated gene expression. Disease-associated, GTPase-defective ARF1 increases cGAS-STING dependent type I IFN signalling in cell lines and primary patient cells. Mechanistically, mutated ARF1 perturbs mitochondrial morphology, causing cGAS activation by aberrant mitochondrial DNA release, and leads to accumulation of active STING at the Golgi/ERGIC due to defective retrograde transport. Our data show an unexpected dual role of ARF1 in maintaining cGAS-STING homeostasis, through promotion of mitochondrial integrity and STING recycling.

Targeting STING in cancer: Challenges and emerging opportunities

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway is a key pathway through which the host regulates immune responses by recognizing cytoplasmic double-stranded DNA of abnormal origin, and it plays an important role in tumor growth as well as metastasis, with relevant molecular details constantly being explored and updated. The significant immunomodulatory effects make STING an attractive target for cancer immunotherapy, and STING agonists have been receiving great attention for their development and clinical translation. Despite exciting results in preclinical work, the application of STING agonists to cancer therapy remains challenging due to their poor pharmacokinetic and physicochemical properties, as well as toxic side effects they produce. Here, we summarize the dichotomous role of cGAS-STING in cancer and discuss the limitations of cancer immunotherapy based on STING activation as well as feasible strategies to overcome them to achieve tumor regression.

cGAS-STING signaling pathway promotes hypoxia-induced renal fibrosis by regulating PFKFB3-mediated glycolysis

Hypoxia has long been considered to play an active role in the progression of fibrosis in chronic kidney disease, but its specific mechanism is not fully understood. The stimulator of interferon genes (STING) has been a research hotspot in the fields of tumor, immunity, and infection in recent years, and its role in immune and inflammatory responses related to kidney disease has gradually attracted attention. This study mainly explores the role and mechanism of STING in hypoxia-related renal fibrosis. To address this issue, we stimulated human proximal tubular epithelial (HK-2) cells with hypoxia for 48 h to construct cell models. Meanwhile, C57BL/6J male mice were used to establish a renal fibrosis model induced by renal ischemia-reperfusion injury (IRI). In our present study, we found that the GMP-AMP synthase (cGAS)-STING signaling pathway can promote the progression of renal fibrosis after hypoxic exposure, and this effect is closely related to 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 3 (PFKFB3)-mediated glycolysis. Furthermore, inhibition of both STING and its downstream interferon regulatory factor 3 (IRF3) reversed elevated PFKFB3 expression, thereby attenuating hypoxia-induced renal fibrosis. Taken together, our data suggest that the cGAS-STING-IRF3-PFKFB3 signaling pathway activated under hypoxia may provide new ideas and targets for the treatment of early renal fibrosis.

STING1 deficiency ameliorates immune-mediated crescentic glomerulonephritis in mice

Rapidly progressive/crescentic glomerulonephritis (RPGN/CGN) involves the formation of glomerular crescents by maladaptive differentiation of parietal epithelial cells that leads to rapid loss of renal function. The molecular mechanisms of crescent formation are poorly understood. Therefore, new insights into molecular mechanisms could identify alternative therapeutic targets for RPGN/CGN. Analysis of kidney biopsies from patients with RPGN revealed increased interstitial, glomerular, and tubular expression of STING1, an accessory protein of the c-GAS-dependent DNA-sensing pathway, which was also observed in murine nephrotoxic nephritis induced by an anti-GBM antibody. STING1 was expressed by key cell types involved in RPGN and crescent formation such as glomerular parietal epithelial cells, and tubular cells as well as by inflammation accessory cells. In functional in vivo studies, Sting1-/- mice with nephrotoxic nephritis had lower kidney cytokine expression, milder kidney infiltration by innate and adaptive immune cells, and decreased disease severity. Pharmacological STING1 inhibition mirrored these findings. Direct STING1 agonism in parietal and tubular cells activated the NF-κB-dependent cytokine response and the interferon-induced genes (ISGs) program. These responses were also triggered in a STING1-dependent manner by the pro-inflammatory cytokine TWEAK. These results identify STING1 activation as a pathological mechanism in RPGN/CGN and TWEAK as an activator of STING1. Pharmacological strategies targeting STING1, or upstream regulators may therefore be potential alternatives to treat RPGN. © 2023 The Pathological Society of Great Britain and Ireland.

Sonodynamic amplification of cGAS-STING activation by cobalt-based nanoagonist against bone and metastatic tumor

The therapeutic effect of cancer immunotherapy is restrained by limited patient response rate caused by 'cold' tumors with an intrinsically immunosuppressive tumor microenvironment (TME). Activating stimulator of interferon genes (STING) confers promising antitumor immunity even in 'cold' tumors, but the further promotion of STING agonists is hindered by undesirable toxicity, low specificity and lack of controllability. Herein, an ultrasound-controllable cGAS-STING amplifying nanoagonist was constructed by coordinating mitochondria-targeting ligand triphenylphosphonium (TPP) to sonodynamic cobalt organic framework nanosheets (TPP@CoTCPP). The Co ions specifically amplify STING activation only when cytosolic mitochondrial DNA leakage is caused by sonocatalysis-induced ROS production and sensed by cGAS. A series of downstream innate immune proinflammatory responses induced by local cGAS-STING pathway activation under spatiotemporal ultrasound stimulation efficiently prime the antitumor T-cell response against bone metastatic tumor, a typical immunosuppressive tumor. We also found that the coordination of TPP augments the sonodynamic effect of CoTCPP nanosheets by reducing the band gap, improving O2 adsorption and enhancing electron transfer. Overall, our study demonstrates that the targeted and amplified cGAS-STING activation in cancer cell controlled by spatiotemporal ultrasound irradiation boosts high-efficiency sonodynamic-ionicimmunotherapy against immunosuppressive tumor.

Molecular characterization of a novel mitochondrial NOD-like receptor X1 in chicken that negatively regulates IFN-β expression via STING

NOD-like receptor X1 (NLRX1) is known for its unique mitochondrial localization and plays a negative role in innate immunity. The initial characterization and function of chicken NLRX1 remain unclear. Here, chicken mitochondrial-targeted NLRX1 (chNLRX1) protein was identified. It had relatively conserved domains, a unique N-terminal "X" mitochondrial-targeting domain (MT) and 2 highly conserved motifs at positions 510-520 and 412-421. Furthermore, chNLRX1 had a unique 53aa N-terminus-MT consistent with its localization to mitochondria. Additionally, chNLRX1 was observed to reduce the DNA sensing adaptor stimulator of interferon genes (STING)-induced IFN-β by attenuating the STING-TANK-binding kinase 1 (TBK1) interaction, which is a requisite for the STING-TBK1-IFN-β signaling pathway. These results suggested that chNLRX1 negatively regulated type-I interferon production via STING in host innate immunity.

Mitochondrial Impairment: A Link for Inflammatory Responses Activation in the Cardiorenal Syndrome Type 4

Cardiorenal syndrome type 4 (CRS type 4) occurs when chronic kidney disease (CKD) leads to cardiovascular damage, resulting in high morbidity and mortality rates. Mitochondria, vital organelles responsible for essential cellular functions, can become dysfunctional in CKD. This dysfunction can trigger inflammatory responses in distant organs by releasing Damage-associated molecular patterns (DAMPs). These DAMPs are recognized by immune receptors within cells, including Toll-like receptors (TLR) like TLR2, TLR4, and TLR9, the nucleotide-binding domain, leucine-rich-containing family pyrin domain-containing-3 (NLRP3) inflammasome, and the cyclic guanosine monophosphate (cGMP)-adenosine monophosphate (AMP) synthase (cGAS)-stimulator of interferon genes (cGAS-STING) pathway. Activation of these immune receptors leads to the increased expression of cytokines and chemokines. Excessive chemokine stimulation results in the recruitment of inflammatory cells into tissues, causing chronic damage. Experimental studies have demonstrated that chemokines are upregulated in the heart during CKD, contributing to CRS type 4. Conversely, chemokine inhibitors have been shown to reduce chronic inflammation and prevent cardiorenal impairment. However, the molecular connection between mitochondrial DAMPs and inflammatory pathways responsible for chemokine overactivation in CRS type 4 has not been explored. In this review, we delve into mechanistic insights and discuss how various mitochondrial DAMPs released by the kidney during CKD can activate TLRs, NLRP3, and cGAS-STING immune pathways in the heart. This activation leads to the upregulation of chemokines, ultimately culminating in the establishment of CRS type 4. Furthermore, we propose using chemokine inhibitors as potential strategies for preventing CRS type 4.

Effect of radiation fractionation on IDO1 via the NF-κB/COX2 axis in non-small cell lung cancer

Radiotherapy (RT) is the mainstay treatment modality for lung cancer. We recently reported that conventionally fractionated radiotherapy (CRT) with daily fractionation of 2Gy significantly increased the activity of indoleamine 2,3-dioxygenase (IDO1), a known immune checkpoint, which predicted poorer long-term survival in patients with non-small cell lung cancer (NSCLC), while stereotactic body radiotherapy (SBRT) using fractionation size of 10Gy did not increase IDO1 activity and had better survival. Here we hypothesized that the hypofractionated SBRT kind of dose fraction stimulates host antitumor immunity via downregulating IDO1 in which CRT could not. We tested this hypothesis in vitro and in vivo using 10Gyx1 and 2Gyx8 fractionations in the laboratory. The results demonstrated that, although there was an initial downregulation after RT, the expression of IDO1 was ultimately upregulated by both fractionation regimens. The 10Gyx1 regimen had minimum upregulation, while the 2Gyx8 regimen significantly increased in IDO1 expression which was positively correlated with the elevated expressions of p-NF-κB and COX2. Pharmacological inhibition of COX2 abolished RT-induced IDO1 expression. Furthermore, the IDO1 inhibitor, D-1-methyl-tryptophan (D-1MT), exerted RT-related tumor-killing effects in the NSCLC cell lines and mouse models. These findings suggest that, in addition to being an immune suppressor, IDO1 may serve as an adaptive resistance factor in RT. Furthermore, an unappreciated mechanism may exist, where a larger fraction size might be superior to conventional sizes in cancer treatment. This study may provide a rationale for future research in using IDO1 as a biomarker to personalize RT dose fractionation and COX2 inhibitor to decrease radiation immune suppression from CRT.

Reverse thiophosphorylase activity of a glycoside phosphorylase in the synthesis of an unnatural Manβ1,4GlcNAc library

β-Mannosides are ubiquitous in nature, with diverse roles in many biological processes. Notably, Manβ1,4GlcNAc a constituent of the core N-glycan in eukaryotes was recently identified as an immune activator, highlighting its potential for use in immunotherapy. Despite their biological significance, the synthesis of β-mannosidic linkages remains one of the major challenges in glycoscience. Here we present a chemoenzymatic strategy that affords a series of novel unnatural Manβ1,4GlcNAc analogues using the β-1,4-d-mannosyl-N-acetyl-d-glucosamine phosphorylase, BT1033. We show that the presence of fluorine in the GlcNAc acceptor facilitates the formation of longer β-mannan-like glycans. We also pioneer a "reverse thiophosphorylase" enzymatic activity, favouring the synthesis of longer glycans by catalysing the formation of a phosphorolysis-stable thioglycoside linkage, an approach that may be generally applicable to other phosphorylases.

STING-driven activation of T cells: relevance for the adoptive cell therapy of cancer

Adoptive cell therapy (ACT) can successfully treat hematopoietic cancers but lacks efficacy against solid tumors. This is due to insufficient T cell infiltration, high tumor heterogeneity, frequent antigen loss with subsequent tumor escape, and the immunosuppressive tumor microenvironment (TME). Alternative methods to boost the anticancer efficacy of adoptively transferred cells are actively pursued. Among adjuvants that are utilized to stimulate anticancer immune responses, ligands of the stimulator of interferon genes (STING) pathway have received increasing attention. STING activation can trigger dendritic cell (DC) activation and endogenous immune responses, thereby preventing tumor escape. Activation of the STING pathway in the context of ACT was accordingly associated with improved T cell trafficking and persistence in the TME combined with the reduced presence of immunosuppressive cells. Recent findings also suggest cell-intrinsic effects of STING ligands on T cells. Activation of the STING signaling pathway was in this regard shown to enhance effector functions of CD4+ and CD8+ T cells, suggesting that the STING signaling could be exploited to harness T cell anticancer functions. In this review, we will discuss how the STING signaling can be used to enhance the anticancer efficacy of ACT.

Systemic administration of STING agonist promotes myeloid cells maturation and antitumor immunity through regulating hematopoietic stem and progenitor cell fate

STING is a pivotal mediator of effective innate and adaptive anti-tumor immunity; however, intratumoral administration of STING agonists have shown limited therapeutic benefit in clinical trials. The systemic effect of the intravenous delivery of STING agonists in cancer is not well-defined. Here, we demonstrated that systemic administration of STING agonist inhibited melanoma growth, improved inflammatory effector cell infiltration, and induced bone marrow mobilization and extramedullary hematopoiesis, causing widespread changes in immune components in the peripheral blood. The systemically administered STING agonist promoted HSC expansion and influenced lineage fate commitment, which was manifested as the differentiation of HSPCs was skewed toward myeloid cells at the expense of B-cell lymphopoiesis and erythropoiesis. Transcriptome analysis revealed upregulation of myeloid lineage differentiation-related and type I interferon-related genes. This myeloid-biased differentiation promoted the production and maturation of myeloid cells toward an activated phenotype. Furthermore, depletion of Gr-1+ myeloid cells attenuated the anti-tumor immunity of STING agonist. Our findings reveal the anti-tumor mechanism of systemic administration of STING agonist that involves modulating HSPC differentiation and promoting myeloid cells maturation. Our study may help explain the limited clinical activity of STING agonists administered intratumorally.

Stimulator of interferon genes (STING): Key therapeutic targets in ischemia/reperfusion injury

The Stimulator of Interferon Genes (STING) is predominantly expressed in immune cells, including macrophages, natural killer cells, dendritic cells, and T cells, functioning as a pattern recognition receptor. STING activation upon detecting cytosolic DNA released from damaged cells initiates downstream pathways, leading to the production of inflammatory cytokines such as IFNs, IL-6, and TNF-α. Dysregulated STING activation has been implicated in inflammatory and metabolic diseases. Ischemia/reperfusion injury (I/RI) is common in stroke, acute myocardial infarction, organ transplantation, and surgeries for certain end-stage diseases. Recent studies suggest that STING could be a novel therapeutic target for I/RI treatment. In this review, we provide a concise overview of the cGAS-STING signaling pathway's general functions and summarize STING's role in I/RI across various organs, including the heart, liver, kidney, and lung. Moreover, we explore potential therapeutic approaches for I/RI by targeting STING.

Mitophagy involved the biological processes of hormones

Mitochondria fulfill vital functions in energy production, maintaining ion balance, and facilitating material metabolism. Mitochondria are sacrificed to protect cells or induce apoptosis when the body is under stress. The regulatory pathways of mitophagy include both ubiquitin-dependent and non-dependent pathways. The involvement of mitophagy has been demonstrated in the onset and progression of numerous diseases, highlighting its significant role. Endocrine hormones are chemical substances secreted by endocrine organs or endocrine cells, which participate in the regulation of physiological functions and internal environmental homeostasis of the body. Imbalances in endocrine hormones contribute to the development of various diseases. However, the precise impact of mitophagy on the physiological and pathological processes involving endocrine hormones remains unclear. This article aims to comprehensively overview recent advancements in understanding the mechanisms through which mitophagy regulates endocrine hormones.

Effector memory T cells induce innate inflammation by triggering DNA damage and a non-canonical STING pathway in dendritic cells

Cognate interaction between CD4+ effector memory T (TEM) cells and dendritic cells (DCs) induces innate inflammatory cytokine production, resulting in detrimental autoimmune pathology and cytokine storms. While TEM cells use tumor necrosis factor (TNF) superfamily ligands to activate DCs, whether TEM cells prompt other DC-intrinsic changes that influence the innate inflammatory response has never been investigated. We report the surprising discovery that TEM cells trigger double-strand DNA breaks via mitochondrial reactive oxygen species (ROS) production in interacting DCs. Initiation of the DNA damage response in DCs induces activation of a cyclic guanosine monophosphate (GMP)-AMP synthase (cGAS)-independent, non-canonical stimulator of interferon genes (STING)-TNF receptor-associated factor 6 (TRAF6)-nuclear factor κB (NF-κB) signaling axis. Consequently, STING-deficient DCs display reduced NF-κB activation and subsequent defects in transcriptional induction and functional production of interleukin-1β (IL-1β) and IL-6 following their interaction with TEM cells. The discovery of TEM cell-induced innate inflammation through DNA damage and a non-canonical STING-NF-κB pathway presents this pathway as a potential target to alleviate T cell-driven inflammation in autoimmunity and cytokine storms.

The D129L protein of African swine fever virus interferes with the binding of transcriptional coactivator p300 and IRF3 to prevent beta interferon induction

IMPORTANCE

African swine fever (ASF) is an acute, hemorrhagic, and severe porcine infectious disease caused by African swine fever virus (ASFV). ASF outbreaks severely threaten the global pig industries and result in serious economic losses. No safe and efficacious commercial vaccine is currently available except in Vietnam. To date, large gaps in the knowledge concerning viral biological characteristics and immunoevasion strategies have hindered the ASF vaccine design. In this study, we demonstrate that pD129L negatively regulates the type I interferon (IFN) signaling pathway by interfering with the interaction of the transcriptional coactivator p300 and IRF3, thereby inhibiting the induction of type I IFNs. This study reveals a novel immunoevasion strategy employed by ASFV, shedding new light on the intricate mechanisms for ASFV to evade the host immune responses.

Mosquito-borne flaviviruses and type I interferon: catch me if you can!

Mosquito-borne flaviviruses include many viruses that are important human pathogens, including Yellow fever virus, Dengue virus, Zika virus and West Nile virus. While these viruses have long been confined to tropical regions, they now pose a global public health concern, as the geographical distribution of their mosquito vectors has dramatically expanded. The constant threat of flavivirus emergence and re-emergence underlines the need for a better understanding of the relationships between these viruses and their hosts. In particular, unraveling how these viruses manage to bypass antiviral immune mechanisms could enable the design of countermeasures to limit their impact on human health. The body's first line of defense against viral infections is provided by the interferon (IFN) response. This antiviral defense mechanism takes place in two waves, namely the induction of type I IFNs triggered by viral infection, followed by the IFN signaling pathway, which leads to the synthesis of interferon-stimulated genes (ISGs), whose products inhibit viral replication. In order to spread throughout the body, viruses must race against time to replicate before this IFN-induced antiviral state hinders their dissemination. In this review, we summarize our current knowledge on the multiple strategies developed by mosquito-borne flaviviruses to interfere with innate immune detection and signaling pathways, in order to delay, if not prevent, the establishment of an antiviral response.

The role of cGAS-STING signaling in pulmonary fibrosis and its therapeutic potential

Pulmonary fibrosis is a progressive and ultimately fatal lung disease, exhibiting the excessive production of extracellular matrix and aberrant activation of fibroblast. While Pirfenidone and Nintedanib are FDA-approved drugs that can slow down the progression of pulmonary fibrosis, they are unable to reverse the disease. Therefore, there is an urgent demand to develop more efficient therapeutic approaches for pulmonary fibrosis. The intracellular DNA sensor called cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) synthase (cGAS) plays a crucial role in detecting DNA and generating cGAMP, a second messenger. Subsequently, cGAMP triggers the activation of stimulator of interferon genes (STING), initiating a signaling cascade that leads to the stimulation of type I interferons and other signaling molecules involved in immune responses. Recent studies have highlighted the involvement of aberrant activation of cGAS-STING contributes to fibrotic lung diseases. This review aims to provide a comprehensive summary of the current knowledge regarding the role of cGAS-STING pathway in pulmonary fibrosis. Moreover, we discuss the potential therapeutic implications of targeting the cGAS-STING pathway, including the utilization of inhibitors of cGAS and STING.

Structural basis for recruitment of TASL by SLC15A4 in human endolysosomal TLR signaling

Toll-like receptors (TLRs) are a class of proteins that play critical roles in recognizing pathogens and initiating innate immune responses. TASL, a recently identified innate immune adaptor protein for endolysosomal TLR7/8/9 signaling, is recruited by the lysosomal proton-coupled amino-acid transporter SLC15A4, and then activates IRF5, which in turn triggers the transcription of type I interferons and cytokines. Here, we report three cryo-electron microscopy (cryo-EM) structures of human SLC15A4 in the apo monomeric and dimeric state and as a TASL-bound complex. The apo forms are in an outward-facing conformation, with the dimeric form showing an extensive interface involving four cholesterol molecules. The structure of the TASL-bound complex reveals an unprecedented interaction mode with solute carriers. During the recruitment of TASL, SLC15A4 undergoes a conformational change from an outward-facing, lysosomal lumen-exposed state to an inward-facing state to form a binding pocket, allowing the N-terminal helix of TASL to be inserted into. Our findings provide insights into the molecular basis of regulatory switch involving a human solute carrier and offers an important framework for structure-guided drug discovery targeting SLC15A4-TASL-related human autoimmune diseases.

Whole-Genome Resequencing Reveals Selection Signatures of Abigar Cattle for Local Adaptation

Over time, indigenous cattle breeds have developed disease resistance, heat tolerance, and adaptability to harsh environments. Deciphering the genetic mechanisms underlying adaptive traits is crucial for their improvement and sustainable utilization. For the first time, we performed whole-genome sequencing to unveil the genomic diversity, population structure, and selection signatures of Abigar cattle living in a tropical environment. The population structure analysis revealed that Abigar cattle exhibit high nucleotide diversity and heterozygosity, with low runs of homozygosity and linkage disequilibrium, suggesting a genetic landscape less constrained by inbreeding and enriched by diversity. Using nucleotide diversity (Pi) and population differentiation (FST) selection scan methods, we identified 83 shared genes that are likely associated with tropical adaption. The functional annotation analysis revealed that some of these genes are potentially linked to heat tolerance (HOXC13, DNAJC18, and RXFP2), immune response (IRAK3, MZB1, and STING1), and oxidative stress response (SLC23A1). Given the wider spreading impacts of climate change on cattle production, understanding the genetic mechanisms of adaptation of local breeds becomes crucial to better respond to climate and environmental changes. In this context, our finding establishes a foundation for further research into the mechanisms underpinning cattle adaptation to tropical environments.

GAS-STING: a classical DNA recognition pathways to tumor therapy

Cyclic GMP-AMP synthetase (cGAS), recognized as the primary DNA sensor within cells, possesses the capability to identify foreign DNA molecules along with free DNA fragments. This identification process facilitates the production of type I IFNs through the activator of the interferon gene (STING) which induces the phosphorylation of downstream transcription factors. This action characterizes the most archetypal biological functionality of the cGAS-STING pathway. When treated with anti-tumor agents, cells experience DNA damage that triggers activation of the cGAS-STING pathway, culminating in the expression of type I IFNs and associated downstream interferon-stimulated genes. cGAS-STING is one of the important innate immune pathways,the role of type I IFNs in the articulation between innate immunity and T-cell antitumour immunity.type I IFNs promote the recruitment and activation of inflammatory cells (including NK cells) at the tumor site.Type I IFNs also can promote the activation and maturation of dendritic cel(DC), improve the antigen presentation of CD4+T lymphocytes, and enhance the cross-presentation of CD8+T lymphocytes to upregulating anti-tumor responses. This review discussed the cGAS-STING signaling and its mechanism and biological function in traditional tumor therapy and immunotherapy.