Vascular calcification is a prevalent hallmark of cardiovascular risk in elderly and diabetic individuals. Senescent vascular smooth muscle cells (VSMCs) participate in calcification; however, the associated underlying mechanisms remain unknown. Aberrant activation of the cytosolic DNA sensing adaptor stimulator of interferon gene 1 (STING1) caused by cytosolic DNA, particularly that leaked from damaged mitochondria, is a catalyst for aging-related diseases. Although oleoylethanolamide (OEA) is an endogenous bioactive lipid mediator with lipid overload-associated vasoprotective effects, its benefit in diabetic vascular calcification remains uncharacterized. This study focused on the role of STING1 in mitochondrial dysfunction-mediated calcification and premature VMSC senescence in diabetes and the effects of OEA on these pathological processes. In diabetic in vivo rat/mouse aorta calcification models and an in vitro VSMC calcification model induced by Nε-carboxymethyl-lysine (CML), senescence levels, STING1 signaling activation, and mitochondrial damage markers were significantly augmented; however, these alterations were markedly alleviated by OEA, partially in a nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent manner, and similar anti-calcification and senescence effects were observed in STING1-knockout mice and STING1-knockdown VSMCs. Mechanistically, mitochondrial DNA (mtDNA) damage was aggravated by CML in a reactive oxygen species-dependent manner, followed by mtDNA leakage into the cytosol, contributing to VSMC senescence-associated calcification via STING1 pathway activation. OEA treatment significantly attenuated the aforementioned cytotoxic effects of CML by enhancing cellular antioxidant capacity through the maintenance of Nrf2 translocation to the nucleus. Collectively, targeting STING1, a newly defined VSMC senescence regulator, contributes to anti-vascular calcification effects.

Autophagy is a crucial immune defense mechanism that controls the survival and pathogenesis of M. tb by maintaining cell physiology during stress and pathogen attack. The E3-Ub ligases (PRKN, SMURF1, and NEDD4) and autophagy receptors (SQSTM1, TAX1BP1, CALCOCO2, OPTN, and NBR1) play key roles in this process. Galectins (LGALSs), which bind to sugars and are involved in identifying damaged cell membranes caused by intracellular pathogens such as M. tb, are essential. These include LGALS3, LGALS8, and LGALS9, which respond to endomembrane damage and regulate endomembrane damage caused by toxic chemicals, protein aggregates, and intracellular pathogens, including M. tb. They also activate selective autophagy and de novo endolysosome biogenesis. LGALS3, LGALS9, and LGALS8 interact with various components to activate autophagy and repair damage, while CGAS-STING1 plays a critical role in providing immunity against M. tb by activating selective autophagy and producing type I IFNs with antimycobacterial functions. STING1 activates cGAMP-dependent autophagy which provides immunity against various pathogens. Additionally, cytoplasmic surveillance pathways activated by ds-DNA, such as inflammasomes mediated by NLRP3 and AIM2 complexes, control M. tb. Modulation of E3-Ub ligases with small regulatory molecules of LGALSs and TRIM proteins could be a novel host-based therapeutic approach for controlling TB.

STING-associated vasculopathy with onset in infancy (SAVI) is a rare, monogenic interferonopathy caused by gain-of-function variants in STING1 (TMEM173) characterized by systemic inflammation, cutaneous vasculopathy, and interstitial lung disease. We report a case of SAVI attributed to a novel STING1 p.R284T variant who demonstrated characteristic cutaneous features including telangiectasias, livedo and acrocyanotic changes on face and extremities, as well as saddle nose deformity, failure to thrive, inflammatory arthritis and notable lack of pulmonary disease or autoantibody positivity. Due to the risk for progressive and irreversible lung and tissue damage and evolving therapeutic landscape involving the use of Janus kinase inhibitors, it is critical to recognize variable clinical phenotypes to diagnose and consider treatment options for SAVI patients early in their disease course.

Mammalian cells react to the accumulation of double-stranded (ds)DNA in the cytosol by secreting antiviral and proinflammatory cytokines, notably type I interferon (IFN). Recent data reported by Tani et al. demonstrate that overactivation of this pathway is prevented by an adaptive feedback mechanism elicited by type I IFN receptors and executed by the exonuclease three prime repair exonuclease 1 (TREX1).

Extensive studies demonstrate the importance of the STING1 (also known as STING) protein as a signaling hub that coordinates immune and autophagic responses to ectopic DNA in the cytoplasm. Here, we report a nuclear function of STING1 in driving the activation of the transcription factor aryl hydrocarbon receptor (AHR) to control gut microbiota composition and homeostasis. This function was independent of DNA sensing and autophagy and showed competitive inhibition with cytoplasmic cyclic guanosine monophosphate (GMP)-AMP synthase (CGAS)-STING1 signaling. Structurally, the cyclic dinucleotide binding domain of STING1 interacted with the AHR N-terminal domain. Proteomic analyses revealed that STING1-mediated transcriptional activation of AHR required additional nuclear partners, including positive and negative regulatory proteins. Although AHR ligands could rescue colitis pathology and dysbiosis in wild-type mice, this protection was abrogated by mutational inactivation of STING1. These findings establish a key framework for understanding the nuclear molecular crosstalk between the microbiota and the immune system.

The CGAS (cyclic GMP-AMP synthase)-STING1 (stimulator of interferon response cGAMP interactor 1) pathway is an important innate immune pathway that induces proinflammatory cytokine production following stimulation with dsDNA > 45 bp. We recently identified a class of ~ 20-40 bp small cytosolic dsDNA (scDNA) that blocks CGAS-STING1 activation. In this punctum, we discuss the mechanism underlying the inhibition of CGAS-STING1 activation via scDNA. scDNA binds to CGAS but cannot activate its enzymatic activity. It competes with dsDNA > 45 bp for binding with CGAS to inhibit CGAS-STING1 activation. Moreover, scDNA activates macroautophagy/autophagy and induces the autophagic degradation of STING1 and long dsDNA. Autophagy then increases scDNA levels, driving a feedback loop that accelerates the degradation of STING1 and long cytosolic dsDNA. These findings reveal that mutual communication between scDNA and autophagy inhibits CGAS-STING1 activation following stimulation with dsDNA > 45 bp.

STING1 (stimulator of interferon response cGAMP interactor 1) is the quintessential protein in the CGAS-STING1 signaling pathway, crucial for the induction of type I IFN (interferon) production and eliciting innate immunity. Nevertheless, the overactivation or sustained activation of STING1 has been closely associated with the onset of autoimmune disorders. Notably, the majority of these disorders manifest as an upregulated expression of type I interferons and IFN-stimulated genes (ISGs). Hence, strict regulation of STING1 activity is paramount to preserve immune homeostasis. Here, we reported that CSNK1A1/CK1α, a serine/threonine protein kinase, was essential to prevent the overactivation of STING1-mediated type I IFN signaling through autophagic degradation of STING1. Mechanistically, CSNK1A1 interacted with STING1 upon the CGAS-STING1 pathway activation and promoted STING1 autophagic degradation by enhancing the phosphorylation of SQSTM1/p62 at serine 351 (serine 349 in human), which was critical for SQSTM1-mediated STING1 autophagic degradation. Consistently, SSTC3, a selective CSNK1A1 agonist, significantly attenuated the response of the CGAS-STING1 signaling by promoting STING1 autophagic degradation. Importantly, pharmacological activation of CSNK1A1 using SSTC3 markedly repressed the systemic autoinflammatory responses in the trex1-/- mouse autoimmune disease model and effectively suppressed the production of IFNs and ISGs in the PBMCs of SLE patients. Taken together, our study reveals a novel regulatory role of CSNK1A1 in the autophagic degradation of STING1 to maintain immune homeostasis. Manipulating CSNK1A1 through SSTC3 might be a potential therapeutic strategy for alleviating STING1-mediated aberrant type I IFNs in autoimmune diseases.Abbreviations: BMDMs: bone marrow-derived macrophages; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; HTDNA: herring testes DNA; IFIT1: interferon induced protein with tetratricopeptide repeats 1; IFNA4: interferon alpha 4; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISD: interferon stimulatory DNA; ISGs: IFN-stimulated genes; MEFs: mouse embryonic fibroblasts; 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.

Type I interferon (IFN) is a class of proinflammatory cytokines with a dual role on malignant transformation, tumor progression, and response to therapy. On the one hand, robust, acute, and resolving type I IFN responses have been shown to mediate prominent anticancer effects, reflecting not only their direct cytostatic/cytotoxic activity on (at least some) malignant cells, but also their pronounced immunostimulatory functions. In line with this notion, type I IFN signaling has been implicated in the antineoplastic effects of various immunogenic therapeutics, including (but not limited to) immunogenic cell death (ICD)-inducing agents and immune checkpoint inhibitors (ICIs). On the other hand, weak, indolent, and non-resolving type I IFN responses have been demonstrated to support tumor progression and resistance to therapy, reflecting the ability of suboptimal type I IFN signaling to mediate cytoprotective activity, promote stemness, favor tolerance to chromosomal instability, and facilitate the establishment of an immunologically exhausted tumor microenvironment. Here, we review fundamental aspects of type I IFN signaling and their context-dependent impact on malignant transformation, tumor progression, and response to therapy.

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.

SMAD4 is a tumour suppressor and an important regulator of tumour immune scape which is downregulated in cholangiocarcinoma (CCA). STING1 is a vital sensing factor of abnormal DNA; however, the correlation between SMAD4 and STING1 and the role of the SMAD4-STING1 interaction in the progression of CCA have not yet been evaluated. Public database was analysed to reveal the expression of SMAD4 and STING1. A cohort comprising 50 iCCA, 113 pCCA and 119 dCCA patients was assembled for the study. Immunohistochemistry was employed to evaluate the expression levels of STING1 and SMAD4. In vitro transwell and CCK8 assays, along with luciferase reporter assay, were conducted to analyse the potential regulatory mechanisms of SMAD4 on the expression of STING1. Expression of SMAD4 and STING1 were downregulated in CCA tumours and STING1 expression correlated with SMAD4 expression. The overexpression of SMAD4 was found to suppress the migration, invasion and proliferation capabilities of CCA cells; whereas, the knockdown of SMAD4 enhanced these abilities. Furthermore, it was observed that SMAD4 translocated into the nucleus following TGF-β1 stimulation. Knockdown of SMAD4 resulted in the inhibition of STING1 transcriptional activity, whereas the overexpression of SMAD4 promoted the transcriptional activity of STING1. Clinically, low STING1 and SMAD4 expression indicated poor prognosis in CCA, and simultaneously low expression of STING1 and SMAD4 predicts poorer patient survival. SMAD4 regulates the expression of STING1 through its transcription regulating function. Dual low expression of STING1 and SMAD4 had more power in predicting patient survival. These results indicate that SMAD4-silenced CCA may downregulate its STING1 expression to adapt to the immune system.