CSNK1A1/CK1α suppresses autoimmunity by restraining the CGAS-STING1 signaling

SESN1 negatively regulates STING1 to maintain innate immune homeostasis

STING1 is a central hub protein of CGAS-STING1 signaling which is important signaling axis to sense DNA for the host against pathogens infection through regulating type I interferon (IFN-I) production. However, excessive STING1 activation-induced overproduced IFN-I triggers tissue damage and autoimmune disorders. Thus, the activity of STING1 must be precisely regulated for immune homeostasis. Here, we discovered SESN1 (sestrin 1) as an essential negative regulator of STING1 to maintain immune homeostasis. Upon herpes simplex virus-1 (HSV-1) infection, the expression of SESN1 was downregulated, which enhanced potentiality to virus defense for host. Consistently, SESN1-deficient mice exhibited stronger ability against HSV-1 infection compared to wild-type littermates. Additionally, we found the expression of SESN1 was decreased in systemic lupus erythematosus (SLE) patients and trex1 KO mouse model of autoimmune disease. Intriguingly, the replenishment of SESN1 effectively impressed IFN-I production and autoimmune responses in the PBMCs of human SLE specimens and the trex1 KO mouse model both in vitro and in vivo. Mechanistically, SESN1 targeted STING1 and promoted STING1 autophagic degradation by facilitating the interaction of SQSTM1/p62 and STING1. Together, our study uncovers a crucial role of SESN1 for immune homeostasis to balance anti-virus and autoimmunity by regulating STING1. SESN1 might be a potential therapeutic target for infectious and autoimmune diseases.Abbreviations: BMDMs: bone marrow-derived macrophages; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; HTDNA: herring testes DNA; IFNA4: interferon alpha 4; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISD: interferon stimulatory DNA; ISGs: IFN-stimulated genes; PBMCs: peripheral blood mononuclear cells; RSAD2: radical S-adenosyl methionine domain containing 2; SLE: systemic lupus erythematosus; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1.

Cordycepin ameliorates autoimmunity by promoting STING degradation via autophagy pathway

BACKGROUND AND PURPOSE

Stimulator of interferon response cGAMP interactor 1 (STING), a central hub protein of cyclic GMP-AMP synthase (cGAS)-STING signalling pathway, has a crucial role in regulating type I interferons (IFNs) production and response. Recent studies indicate that excessive activation of STING is strongly associated with autoimmune diseases, including systemic lupus erythematosus (SLE). Searching immunomodulators that negatively regulate STING might greatly contribute to the suppression of autoimmunity.

EXPERIMENTAL APPROACH

The peripheral blood mononuclear cells (PBMCs) of SLE patients, Hela cells, L929 cells and bone marrow-derived macrophages (BMDMs) from mice were used as in vitro models. While, Trex1 KO mouse autoimmune disease model was used as in vivo model. After treatment with cordycepin, a nucleoside from Cordyceps mushrooms, type I IFNs production and response were determined by western blotting, real-time polymerase chain reaction (PCR), dual-luciferase assay, enzyme-linked immunosorbent assay (ELISA), haematoxylin-eosin staining and RNA-seq.

KEY RESULTS

Cordycepin inhibited type I IFNs production and response in human and murine systems following cGAS-STING signalling activation. Importantly, cordycepin markedly attenuates the autoinflammatory and autoimmune responses in Trex1 KO BMDMs and Trex1 KO mice. Furthermore, cordycepin effectively suppressed the production of type I IFNs and interferon-stimulated genes (ISGs) in the PBMCs of SLE patients. Mechanistically, cordycepin promoted STING degradation via autophagy pathway upon DNA stimulation.

CONCLUSION AND IMPLICATIONS

This study shows that cordycepin promotes STING autophagic degradation to alleviate autoimmunity upon DNA stimulation. Cordycepin might be a potential therapeutic candidate for alleviating aberrant type I IFNs in autoimmune and autoinflammatory diseases.

Crucial Roles of RSAD2/viperin in Immunomodulation, Mitochondrial Metabolism and Autoimmune Diseases

Autoimmune diseases are typically characterized by aberrant activation of immune system that leads to excessive inflammatory reactions and tissue damage. Nevertheless, precise targeted and efficient therapies are limited. Thus, studies into novel therapeutic targets for the management of autoimmune diseases are urgently needed. Radical S-adenosyl methionine domain-containing 2 (RSAD2) is an interferon-stimulated gene (ISG) renowned for the antiviral properties of the protein it encodes, named viperin. An increasing number of studies have underscored the new roles of RSAD2/viperin in immunomodulation and mitochondrial metabolism. Previous studies have shown that there is a complex interplay between RSAD2/vipeirn and mitochondria and that binding of the iron-sulfur (Fe-S) cluster is necessary for the involvement of viperin in mitochondrial metabolism. Viperin influences the proliferation and development of immune cells as well as inflammation via different signaling pathways. However, the function of RSAD2/viperin varies in different studies and a comprehensive overview of this emerging theme is lacking. This review will describe the characteristics of RSAD2/viperin, decipher its function in immunometabolic processes, and clarify the crosstalk between RSAD2/viperin and mitochondria. Furthermore, we emphasize the crucial roles of RSAD2 in autoimmune diseases and its potential application value.

Macrophages Unmasked: Their Pivotal Role in Driving Atherosclerosis in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that significantly increases the risk of cardiovascular diseases, particularly atherosclerosis (AS). Understanding the shared pathogenic mechanisms underlying SLE and AS is crucial for developing effective therapeutic strategies. Macrophages, as pivotal immune cells, play a critical role in the initiation and progression of atherosclerotic plaques within the context of SLE. This review delves into the molecular and cellular mechanisms governing macrophage activation and differentiation in response to SLE-related inflammatory mediators, highlighting their roles in lipid metabolism, plaque stability, and immune regulation. Additionally, we discussed the current treatment modalities for SLE and their impact on macrophage functionality, exploring these effects for atherosclerotic progression. By elucidating the intricate relationship between macrophages, SLE pathophysiology, and AS progression, this review underscores the need for a multidisciplinary approach in managing SLE and its cardiovascular complications, aiming to improve patient survival and quality of life through tailored therapeutic interventions addressing both autoimmune and cardiovascular pathologies.

Laminaran potentiates cGAS-STING signaling to enhance antiviral responses

Cyclic GMP-AMP synthase (cGAS)-Stimulator of interferon genes (STING) signaling pathway, an essential element in the innate antiviral immune responses, has emerged as a key component of innate immune system to modulate type I IFNs production and response by recognizing both exogenous and endogenous DNA. Although some cGAS-STING signaling small molecule agonists have been developed, there are few natural polysaccharides reported to activate cGAS-STING signaling for the treatment of infectious diseases. Here, we reported that Laminaran, a low molecular weight β-glucan storage polysaccharide present in brown algae, potentiates cGAS-STING signaling to promote type I IFNs production and antiviral response. Laminaran enhanced cGAS-STING signaling mediated type I IFNs production and response both in human and murine cells upon HSV-1 infection or DNA mimics stimulation. Importantly, we found that Laminaran markedly inhibited Herpes simplex virus-1 (HSV-1) induced death and inflammatory responses and increased the induction of type I IFNs in C57BL/6J mice. Mechanistically, we found Laminaran inhibited autophagy and suppressed STING autophagic degradation to positively regulate cGAS-STING signaling response. Taken together, we uncovered the function of Laminaran in DNA triggered innate immunity by enhancing cGAS-STING signaling response. Laminaran might be a potential therapeutic candidate for viral infectious diseases.

STING exerts antiviral innate immune response by activating pentose phosphate pathway

BACKGROUND

The innate immune system serves as the host's first line of defense against invading pathogens. Stimulator of interferon genes (STING) is a key component of this system, yet its relationship with glucose metabolism, particularly in antiviral immunity, remains underexplored.

METHODS

Metabolomics analysis was used for detecting metabolic alterations in spleens from STING knockout (KO) and wild-type (WT) mice. Co-immunoprecipitation was employed for determining ubiquitination of TKT. Mass spectrometry was used for detecting interaction proteins of STING. Enzyme activity kits were used for detecting the activities of TKT and G6PD.

RESULTS

In this study, we demonstrate that herpes simplex virus (HSV) infection activates the pentose phosphate pathway (PPP) in host cells, thereby initiating an antiviral immune response. Using STING-manipulated cells and systemic knockout mice, we show that STING positively regulates PPP, which, in turn, limits HSV infection. Inhibition of the PPP significantly reduced the production of antiviral immune factors and dampened STING-induced innate immune responses. Mechanistically, we discovered that STING interacts with transketolase (TKT), a key enzyme in the non-oxidative branch of the PPP, and reduces its ubiquitination via the E3 ubiquitin ligase UBE3A, stabilizing TKT. Silencing TKT or inhibiting its activity with oxythiamine diminished antiviral immune factor production.

CONCLUSION

Our findings reveal that the PPP plays a synergistic role in generating antiviral immune factors during viral infection and suggest that PPP activation could serve as an adjunct strategy for antiviral therapy.

New insight in treating autoimmune diseases by targeting autophagy

Autophagy is a highly conserved biological process in eukaryotes, which degrades cellular misfolded proteins, damaged organelles and invasive pathogens in the lysosome-dependent manner. Autoimmune diseases caused by genetic elements, environments and aberrant immune responses severely impact patients' living quality and even threaten life. Recently, numerous studies have reported autophagy can regulate immune responses, and play an important role in autoimmune diseases. In this review, we summarised the features of autophagy and autophagy-related genes, enumerated some autophagy-related genes involved in autoimmune diseases, and further overviewed how to treat autoimmune diseases through targeting autophagy. Finally, we outlooked the prospect of relieving and curing autoimmune diseases by targeting autophagy pathway.

The cGAS-STING/PERK-eIF2α: Individual or Potentially Collaborative Signaling Transduction in Cardiovascular Diseases

Over the past several decades, a canonical pathway called the cyclic GMP-AMP (cGAMP) synthase (cGAS)-stimulator of interferon genes (STING) mediating type I interferon (IFN) release via TANK-binding kinase 1(TBK1) / IFN regulatory factor 3 (IRF3) pathway has been widely investigated and characterized. Unexpectedly, recent studies show that the cGAS-STING noncanonically activates the protein kinase RNA-like ER kinase (PERK)-eukaryotic initiation factor 2α (eIF2α), an essential branch of unfolded protein response (UPR), even before the activation of the TBK1/IRF3 signaling. Additionally, we found that the PERK could regulate the STING signaling besides being modulated by upstream cGAS-STING. However, earlier evidence solely focused on the unidirectional regulation of STING and PERK, lacking their functional crosstalk. Hence, we postulate that there is a complex relationship between the cGAS-STING and PERK-eIF2α pathways and that, through convergent downstream signaling, they may collaboratively contribute to the pathophysiology of cardiovascular diseases (CVDs) via the cGAS-STING/PERK-eIF2α signaling axis. This study provides a novel pathway for the development of CVDs and paves the foundation for potential therapeutic targets for CVDs.

Decoding the connection between SLE and DNA Sensors: A comprehensive review

Systemic lupus erythematosus (SLE) is recognized as a prevalent autoimmune disorder characterized by a multifaceted pathogenesis potentially influenced by a combination of environmental factors, genetic predisposition, and hormonal regulation. The continuous study of immune system activation is especially intriguing. Analysis of blood samples from individuals with SLE reveals an abnormal increase in interferon levels, along with the existence of anti-double-stranded DNA antibodies. This evidence suggests that the development of SLE may be initiated by innate immunity. The presence of abnormal dsDNA fragments can activate DNA sensors within cells, particularly immune cells, leading to the initiation of downstream signaling cascades that result in the upregulation of relevant cytokines and the subsequent initiation of adaptive immune responses, such as B cell differentiation and T cell activation. The intricate pathogenesis of SLE results in DNA sensors exhibiting a wide range of functions in innate immune responses that are subject to variation based on cell types, developmental processes, downstream effector signaling pathways and other factors. The review aims to reorganize how DNA sensors influence signaling pathways and contribute to the development of SLE according to current studies, with the aspiration of furnishing valuable insights for future investigations into the pathological mechanisms of SLE and potential treatment approaches.

VRK1 promotes DNA-induced type I interferon production

BACKGROUND

Type I interferons (IFNs) are an essential class of cytokines with antitumor, antiviral and immunoregulatory effects. However, over-productive the type I IFNs are tightly associated with autoimmune disorders. Thus, the induction of type I interferons is precisely regulated to maintain immune hemostasis. This study aimed to identify a novel regulator of type I interferon signaling.

METHODS AND RESULTS

Primary BMDMs, isolated from mice, and human cell lines (HEK293 cells, Hela cells) and murine cell line (MEF cells) were cultured to generate in vitro models. After knockdown VRK1, real-time PCR and dual-luciferase reporter assay were performed to determine the expression level of the type I IFNs and ISGs following HTDNA and Poly (dA:dT) stimulation. Additionally, cells were treated with the VRK1 inhibitor, and the impact of VRK1 inhibition was detected. Upon HTDNA and Poly (dA:dT) stimulation, knockdown of VRK1 attenuated the induction of the type I IFNs and ISGs. Consistently, VRK-IN-1, a potent and selective VRK1 inhibitor, significantly suppressed the induction of the type I IFNs and ISGs in human and murine cell lines. Further, VRK-IN-1 inhibited induction of the type I IFNs in mouse primary BMDMs. Intriguingly, VRK1 potentiated the cGAS-STING- IFN-I axis response at STING level.

CONCLUSIONS

Our study reveals a novel function of VRK1 in regulating the production of type I IFNs. VRK-IN-1 might be a potential lead compound for suppressing aberrant type I IFNs in autoimmune disorders.