bims-unfpre 2023-05-07 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2023‒05‒07
fourteen papers selected by
Susan Logue
University of Manitoba

Hydrogen sulfide plays an important role by regulating endoplasmic reticulum stress in myocardial diseases.
Gene deletion of Interleukin-1α reduces ER stress-induced CHOP expression in macrophages and attenuates the progression of atherosclerosis in apoE-deficient mice.
Ufmylation bridges autophagy and ER homeostasis in plants.
Increased activity of IRE1 improves the clinical presentation of EAE.
Activation of ACLY by SEC63 deploys metabolic reprogramming to facilitate hepatocellular carcinoma metastasis upon endoplasmic reticulum stress.
Autophagy and unfolded protein response induction: a crosstalk between street rabies virus and the host.
Structural remodeling of the endoplasmic reticulum in response to extracellular signals requires αTAT1-induced microtubule acetylation.
mTOR inhibition suppresses Myc-driven polyposis by inducing immunogenic cell death.
Endoplasmic Reticulum Stress: A Key Regulator of Cardiovascular Disease.
Atransgenic mouse line for assaying tissue-specific changes in endoplasmic reticulum proteostasis.
Disruption of ER ion homeostasis maintained by an ER anion channel CLCC1 contributes to ALS-like pathologies.
Potent carotenoid astaxanthin expands the anti-cancer activity of cisplatin in human prostate cancer cells.
SEL1L-HRD1 endoplasmic reticulum-associated degradation controls STING-mediated innate immunity by limiting the size of the activable STING pool.
Inhibition of neutrophil extracellular trap formation attenuates NLRP1-dependent neuronal pyroptosis via STING/IRE1α pathway after traumatic brain injury in mice.

Front Pharmacol. 2023 ;14 1172147

Hydrogen sulfide plays an important role by regulating endoplasmic reticulum stress in myocardial diseases.

Huijie Zhao, Xiaodi Fu, Yanting Zhang, Yihan Yang, Honggang Wang.

  Endoplasmic reticulum (ER) is an important organelle for protein translation, folding and translocation, as well as the post-translational modification and assembly of newly synthesized secreted proteins. When the excessive accumulation of misfolded and/or unfolded proteins exceeds the processing capacity of ER, ER stress is triggered. The integrated intracellular signal cascade, namely the unfolded protein response, is induced to avoid ER stress. ER stress is involved in many pathological and physiological processes including myocardial diseases. For a long time, hydrogen sulfide (H2S) has been considered as a toxic gas with the smell of rotten eggs. However, more and more evidences indicate that H2S is an important gas signal molecule after nitric oxide and carbon monoxide, and regulates a variety of physiological and pathological processes in mammals. In recent years, increasing studies have focused on the regulatory effects of H2S on ER stress in myocardial diseases, however, the mechanism is not very clear. Therefore, this review focuses on the role of H2S regulation of ER stress in myocardial diseases, and deeply analyzes the relevant mechanisms so as to lay the foundation for the future researches.

Keywords:  apoptosis; endoplasmic reticulum stress; hydrogen sulfide; myocardial diseases; oxidative stress

DOI:  https://doi.org/10.3389/fphar.2023.1172147
Cytokine. 2023 May 03. pii: S1043-4666(23)00090-X. [Epub ahead of print]167 156212

Gene deletion of Interleukin-1α reduces ER stress-induced CHOP expression in macrophages and attenuates the progression of atherosclerosis in apoE-deficient mice.

Tal Almog, Rom Keshet, Michal Kandel-Kfir, Aviv Shaish, Ron N Apte, Dror Harats, Yehuda Kamari.

  The pathophysiology of atherosclerosis initiation and progression involves many inflammatory cytokines, one of them is interleukin (IL)-1α that has been shown to be secreted by activated macrophages. We have previously shown that IL-1α from bone marrow-derived cells is critical for early atherosclerosis development in mice. It is known that endoplasmic reticulum (ER) stress in macrophages is involved in progression to more advanced atherosclerosis, but it is still unknown whether this effect is mediated through cytokine activation or secretion. We previously demonstrated that IL-1α is required in ER stress-induced activation of inflammatory cytokines in hepatocytes and in the associated induction of steatohepatitis. In the current study, we aimed to examine the potential role of IL-1α in ER stress-induced activation of macrophages, which is relevant to progression of atherosclerosis. First, we demonstrated that IL-1α is required for atherosclerosis development and progression in the apoE knockout (KO) mouse model of atherosclerosis. Next, we showed that ER stress in mouse macrophages results in the protein production and secretion of IL-1α in a dose-dependent manner, and that IL-1α is required in ER stress-induced production of the C/EBP homologous protein (CHOP), a critical step in ER stress-mediated apoptosis. We further demonstrated that IL-1α-dependent CHOP production in macrophages is specifically mediated through the PERK-ATF4 signaling pathway. Altogether, these findings highlight IL-1α as a potential target for prevention and treatment of atherosclerotic cardiovascular disease.

Keywords:  Atherosclerosis; ER Stress; IL-1α; Macrophages; apoE KO

DOI:  https://doi.org/10.1016/j.cyto.2023.156212
Autophagy. 2023 May 01. 1-2

Ufmylation bridges autophagy and ER homeostasis in plants.

Baiying Li, Liwen Jiang.

  The autophagic machinery is highly conserved in eukaryotes. Plants, as sessile organisms, are more susceptible to environmental stresses than animals. Autophagy plays a pivotal role in plant stress responses, but the regulation of autophagic flux in plants remains enigmatic with few autophagic receptors identified. We recently characterized an E3 ligase, the ubiquitin-fold modifier 1 (Ufm1) ligase 1 (Ufl1), as well as its small modifier protein Ufm1, as interactors of the core autophagy-related (ATG) proteins. Mutants of these ufmylation system components are hypersensitive to salt stress and trigger the upregulation of endoplasmic reticulum (ER) stress-responsive genes, as well as the accumulation of ER sheets caused by a defect in reticulophagy. Increased expression of Ufl1, Ufm1 and Ufm1-conjugating enzyme 1 (Ufc1) are also triggered by salt stress in plants. This study identified and demonstrated the participation of ufmylation components in maintaining ER homeostasis by regulating reticulophagy under salt stress in plants.Abbreviations: ATG, autophagy-related; ER, endoplasmic reticulum; LIR, LC3-interacting region; ROS, reactive oxygen species; CDK5RAP3/C53, CDK5 regulatory subunit-associated protein 3; Uba5, Ufm1-activating enzyme 5; Ufc1, Ufm1-conjugating enzyme 1; Ufl1, Ufm1 ligase 1; Ufm1, ubiquitin-fold modifier 1; UPR, unfolded protein response.

Keywords:  Arabidopsis; ER homeostasis; ER stress; autophagy; reticulophagy; salt stress

DOI:  https://doi.org/10.1080/15548627.2023.2203985
bioRxiv. 2023 Apr 20. pii: 2023.04.19.537391. [Epub ahead of print]

Increased activity of IRE1 improves the clinical presentation of EAE.

Valerie Bracchi-Ricard, Kayla Nguyen, Daniela Ricci, Brian Gaudette, Jorge Henao-Meija, Roberta Brambilla, Tetyana Martynyuk, Tali Gidalevitz, David Allman, John R Bethea, Yair Argon.

Activation of the ER stress sensor IRE1α contributes to neuronal development and is known to induce neuronal remodeling in vitro and in vivo . On the other hand, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1α, we used a mouse model expressing a C148S variant of IRE1α with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody-producing cells, but exhibited a strong protective effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Significant improvement in motor function was found in IRE1C148S mice with EAE relative to WT mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of pro-inflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced CNPase levels, suggestiing improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the activation of microglial activation marker IBA1, along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1α activity can be protective in vivo , and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of the ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

DOI: https://doi.org/10.1101/2023.04.19.537391
J Exp Clin Cancer Res. 2023 May 01. 42(1): 108

Activation of ACLY by SEC63 deploys metabolic reprogramming to facilitate hepatocellular carcinoma metastasis upon endoplasmic reticulum stress.

Chenyu Hu, Zechang Xin, Xiaoyan Sun, Yang Hu, Chunfeng Zhang, Rui Yan, Yuying Wang, Min Lu, Jing Huang, Xiaojuan Du, Baocai Xing, Xiaofeng Liu.

  BACKGROUND: Tumor cells display augmented capability to maintain endoplasmic reticulum (ER) homeostasis and hijack ER stress pathway for malignant phenotypes under microenvironmental stimuli. Metabolic reprogramming is a well-known hallmark for tumor cells to provide specific adaptive traits to the microenvironmental alterations. However, it's unknown how tumor cells orchestrate metabolic reprogramming and tumor progression in response to ER stress. Herein, we aimed to explore the pivotal roles of SEC63-mediated metabolic remodeling in hepatocellular carcinoma (HCC) cell metastasis after ER stress.METHODS: The expression levels of SEC63 in HCC tissues and adjacent non-cancerous tissues were determined by immunohistochemistry and western blot. The regulatory roles of SEC63 in HCC metastasis were investigated both in vitro and in vivo by RNA-sequencing, metabolites detection, immunofluorescence, and transwell migration/invasion analyses. GST pull-down, immunoprecipitation/mass spectrometry and in vivo ubiquitination/phosphorylation assay were conducted to elucidate the underlying molecular mechanisms.
RESULTS: We identified SEC63 as a new regulator of HCC cell metabolism. Upon ER stress, the phosphorylation of SEC63 at T537 by IRE1α pathway contributed to SEC63 activation. Then, the stability of ACLY was upregulated by SEC63 to increase the supply of acetyl-CoA and lipid biosynthesis, which are beneficial for improving ER capacity. Meanwhile, SEC63 also entered into nucleus for increasing nuclear acetyl-CoA production to upregulate unfolded protein response targets to improve ER homeostasis. Importantly, SEC63 coordinated with ACLY to epigenetically modulate expression of Snail1 in the nucleus. Consequently, SEC63 promoted HCC cell metastasis and these effects were reversed by ACLY inhibition. Clinically, SEC63 expression was significantly upregulated in HCC tissue specimens and was positively correlated with ACLY expression. Importantly, high expression of SEC63 predicted unfavorable prognosis of HCC patients.
CONCLUSIONS: Our findings revealed that SEC63-mediated metabolic reprogramming plays important roles in keeping ER homeostasis upon stimuli in HCC cells. Meanwhile, SEC63 coordinates with ACLY to upregulate the expression of Snail1, which further promotes HCC metastasis. Metastasis is crucial for helping cancer cells seek new settlements upon microenvironmental stimuli. Taken together, our findings highlight a cancer selective adaption to ER stress as well as reveal the potential roles of the IRE1α-SEC63-ACLY axis in HCC treatment.

Keywords:  ACLY; ER stress; Hepatocellular carcinoma; Metabolic reprogramming; Metastasis; SEC63

DOI:  https://doi.org/10.1186/s13046-023-02656-7
Cell Stress Chaperones. 2023 May 03.

Autophagy and unfolded protein response induction: a crosstalk between street rabies virus and the host.

Shima Poorghobadi, Kazem Baesi, Safoora Gharibzadeh, Reza Shirzad, Mohammad S Khosravy, Maryam Fazeli, Farzaneh Sheikholeslami.

  The endoplasmic reticulum (ER) response mechanism to cellular stress is mediated by the unfolded protein response/ER-associated degradation (UPR/ERAD) pathway. A viral infection can trigger ER stress and engage some transcription factors, depending on the host cell and virus type, activating or inhibiting autophagy. The relationship between ER response and autophagy in rabies has not been investigated yet. In the present study, the mouse brain was infected with street rabies virus (SRABV). Total RNA was extracted from the brains of animals, and cDNA was synthesized. Next, real-time PCR assay was performed using specific primers. The expression of hypoxanthine-guanine phosphoribosyltransferase (Hprt), CCAAT/enhancer binding protein homologous protein (CHOP), apoptosis signal-regulating kinase 1 (ASK1), activating transcription factor 6 (ATF6), and caspase 3 (CASP3) genes was also investigated. Based on the results, SRABV caused significant changes in the mRNA expression of ATF6, CHOP, and ASK1 genes in the brains of infected mice in the control group (group V). Treatment of infected cells with the pIRES-EGFP-Beclin-1 vector and rapamycin caused changes in nearly most of the parameters. However, alterations in CASP3 gene expression were only observed when the vector and the virus were simultaneously injected into the cells. Overall, protection and autophagy against cell death induced by SRABV infection can be achieved by activating the ER stress pathway, followed by a marked increase in the expression of ATF6, CHOP, ASK1, and CASP3 genes.

Keywords:  Autophagy; Host cell; Street rabies virus; Transcription factors; Unfolded protein response

DOI:  https://doi.org/10.1007/s12192-023-01335-y
bioRxiv. 2023 Apr 21. pii: 2023.04.20.537623. [Epub ahead of print]

Structural remodeling of the endoplasmic reticulum in response to extracellular signals requires αTAT1-induced microtubule acetylation.

Hannah R Ortiz, Paola Cruz Flores, Aaron Ramonett, Tasmia Ahmed, Nathan A Ellis, Paul R Langlais, Karthikeyan Mythreye, Nam Y Lee.

Dynamic changes in the endoplasmic reticulum (ER) morphology are central to maintaining cellular homeostasis. Microtubules (MT) facilitate the continuous remodeling of the ER network into sheets and tubules by coordinating with many ER-shaping protein complexes, although how this process is controlled by extracellular signals remains unknown. Here we report that TAK1, a kinase responsive to numerous growth factors and cytokines including TGF-β and TNF-α, triggers ER tubulation by activating αTAT1, an MT-acetylating enzyme that enhances ER-sliding. We show that this TAK1/αTAT-dependent ER remodeling promotes cell survival by actively downregulating BOK, an ER membrane-associated proapoptotic effector. While BOK is normally protected from degradation when complexed with IP3R, it is rapidly degraded upon their dissociation during the ER sheets-to-tubules conversion. These findings demonstrate a distinct mechanism of ligand-induced ER remodeling and suggest that the TAK1/αTAT pathway may be a key target in ER stress and dysfunction.

DOI: https://doi.org/10.1101/2023.04.20.537623
Oncogene. 2023 May 03.

mTOR inhibition suppresses Myc-driven polyposis by inducing immunogenic cell death.

Brian J Leibowitz, Guangyi Zhao, Wenxin Xia, Yuhan Wang, Hang Ruan, Lin Zhang, Jian Yu.

Myc is a key driver of colorectal cancer initiation and progression, but remains a difficult drug target. In this study, we show that mTOR inhibition potently suppresses intestinal polyp formation, regresses established polyps, and prolongs lifespan of APCMin/+ mice. Everolimus in diet strongly reduces p-4EBP1, p-S6, and Myc levels, and induces apoptosis of cells with activated β-catenin (p-S552) in the polyps on day 3. The cell death is accompanied by ER stress, activation of the extrinsic apoptotic pathway, innate immune cell recruitment, and followed by T-cell infiltration on day 14 persisting for months thereafter. These effects are absent in normal intestinal crypts with physiologic levels of Myc and a high rate of proliferation. Using normal human colonic epithelial cells, EIF4E S209A knockin and BID knockout mice, we found that local inflammation and antitumor efficacy of Everolimus requires Myc-dependent induction of ER stress and apoptosis. These findings demonstrate mTOR and deregulated Myc as a selective vulnerability of mutant APC-driven intestinal tumorigenesis, whose inhibition disrupts metabolic and immune adaptation and reactivates immune surveillance necessary for long-term tumor control.

DOI: https://doi.org/10.1038/s41388-023-02706-6
DNA Cell Biol. 2023 May 03.

Endoplasmic Reticulum Stress: A Key Regulator of Cardiovascular Disease.

Zhao Chen, Shi-Liang Zhang.

  The problems associated with economic development and social progress have led to an increase in the occurrence of cardiovascular diseases (CVDs), which affect the health of an increasing number of people and are a leading cause of disease and population mortality worldwide. Endoplasmic reticulum stress (ERS), a hot topic of interest for scholars in recent years, has been confirmed in numerous studies to be an important pathogenetic basis for many metabolic diseases and play an important role in maintaining physiological processes. The endoplasmic reticulum (ER) is a major organelle that is involved in protein folding and modification synthesis, and ERS occurs when several physiological and pathological factors allow excessive amounts of unfolded/misfolded proteins to accumulate. ERS often leads to initiation of the unfolded protein response (UPR) in a bid to re-establish tissue homeostasis; however, UPR has been documented to induce vascular remodeling and cardiomyocyte damage under various pathological conditions, leading to or accelerating the development of CVDs such as hypertension, atherosclerosis, and heart failure. In this review, we summarize the latest knowledge gained concerning ERS in terms of cardiovascular system pathophysiology, and discuss the feasibility of targeting ERS as a novel therapeutic target for the treatment of CVDs. Investigation of ERS has immense potential as a new direction for future research involving lifestyle intervention, the use of existing drugs, and the development of novel drugs that target and inhibit ERS.

Keywords:  arrhythmia; atherosclerosis; endoplasmic reticulum stress; hypertension; ischemic cardiomyopathy; unfolded protein response

DOI:  https://doi.org/10.1089/dna.2022.0532
Transgenic Res. 2023 May 03.

Atransgenic mouse line for assaying tissue-specific changes in endoplasmic reticulum proteostasis.

Reinis Svarcbahs, Sarah M Blossom, Helena S Baffoe-Bonnie, Kathleen A Trychta, Lacey K Greer, James Pickel, Mark J Henderson, Brandon K Harvey.

  Maintenance of calcium homeostasis is important for proper endoplasmic reticulum (ER) function. When cellular stress conditions deplete the high concentration of calcium in the ER, ER-resident proteins are secreted into the extracellular space in a process called exodosis. Monitoring exodosis provides insight into changes in ER homeostasis and proteostasis resulting from cellular stress associated with ER calcium dysregulation. To monitor cell-type specific exodosis in the intact animal, we created a transgenic mouse line with a Gaussia luciferase (GLuc)-based, secreted ER calcium-modulated protein, SERCaMP, preceded by a LoxP-STOP-LoxP (LSL) sequence. The Cre-dependent LSL-SERCaMP mice were crossed with albumin (Alb)-Cre and dopamine transporter (DAT)-Cre mouse lines. GLuc-SERCaMP expression was characterized in mouse organs and extracellular fluids, and the secretion of GLuc-SERCaMP in response to cellular stress was monitored following pharmacological depletion of ER calcium. In LSL-SERCaMP × Alb-Cre mice, robust GLuc activity was observed only in the liver and blood, whereas in LSL-SERCaMP × DAT-Cre mice, GLuc activity was seen in midbrain dopaminergic neurons and tissue samples innervated by dopaminergic projections. After calcium depletion, we saw increased GLuc signal in the plasma and cerebrospinal fluid collected from the Alb-Cre and DAT-Cre crosses, respectively. This mouse model can be used to investigate the secretion of ER-resident proteins from specific cell and tissue types during disease pathogenesis and may aid in the identification of therapeutics and biomarkers of disease.

Keywords:  ER calcium sensor; ER stress; Exodosis; Gaussia luciferase; SERCaMP; Secreted ER-resident proteins

DOI:  https://doi.org/10.1007/s11248-023-00349-7
Cell Res. 2023 May 04.

Disruption of ER ion homeostasis maintained by an ER anion channel CLCC1 contributes to ALS-like pathologies.

Liang Guo, Qionglei Mao, Ji He, Xiaoling Liu, Xuejiao Piao, Li Luo, Xiaoxu Hao, Hanzhi Yu, Qiang Song, Bailong Xiao, Dongsheng Fan, Zhaobing Gao, Yichang Jia.

Although anion channel activities have been demonstrated in sarcoplasmic reticulum/endoplasmic reticulum (SR/ER), their molecular identities and functions remain unclear. Here, we link rare variants of Chloride Channel CLIC Like 1 (CLCC1) to amyotrophic lateral sclerosis (ALS)-like pathologies. We demonstrate that CLCC1 is a pore-forming component of an ER anion channel and that ALS-associated mutations impair channel conductance. CLCC1 forms homomultimers and its channel activity is inhibited by luminal Ca2+ but facilitated by phosphatidylinositol 4,5-bisphosphate (PIP2). We identified conserved residues D25 and D181 in CLCC1 N-terminus responsible for Ca2+ binding and luminal Ca2+-mediated inhibition on channel open probability and K298 in CLCC1 intraluminal loop as the critical PIP2-sensing residue. CLCC1 maintains steady-state [Cl-]ER and [K+]ER and ER morphology and regulates ER Ca2+ homeostasis, including internal Ca2+ release and steady-state [Ca2+]ER. ALS-associated mutant forms of CLCC1 increase steady-state [Cl-]ER and impair ER Ca2+ homeostasis, and animals with the ALS-associated mutations are sensitized to stress challenge-induced protein misfolding. Phenotypic comparisons of multiple Clcc1 loss-of-function alleles, including ALS-associated mutations, reveal a CLCC1 dosage dependence in the severity of disease phenotypes in vivo. Similar to CLCC1 rare variations dominant in ALS, 10% of K298A heterozygous mice developed ALS-like symptoms, pointing to a mechanism of channelopathy dominant-negatively induced by a loss-of-function mutation. Conditional knockout of Clcc1 cell-autonomously causes motor neuron loss and ER stress, misfolded protein accumulation, and characteristic ALS pathologies in the spinal cord. Thus, our findings support that disruption of ER ion homeostasis maintained by CLCC1 contributes to ALS-like pathologies.

DOI: https://doi.org/10.1038/s41422-023-00798-z
J Nat Med. 2023 May 02.

Potent carotenoid astaxanthin expands the anti-cancer activity of cisplatin in human prostate cancer cells.

Yalcin Erzurumlu, Deniz Catakli, Hatice Kubra Dogan.

  Prostate cancer (PCa) is the second most common type of cancer and the sixth cause of death in men worldwide. Radiotherapy and immunotherapy are commonly used in treating PCa, but understanding the crosstalk mechanisms of carcinogenesis and new therapeutic approaches is essential for supporting poor diagnosis and existing therapies. Astaxanthin (ASX) is a member of the xanthophyll family that is an oxygenated derivative of carotenoids whose synthesis is in plant extracts from lycopene. ASX has protective effects on various diseases, such as Parkinson's disease and cancer by showing potent antioxidant and anti-inflammatory properties. However, there is an ongoing need for a detailed investigation of the molecular mechanism of action to expand its therapeutic use. In the present study, we showed the new regulatory role of ASX in PCa cells by affecting the unfolded protein response (UPR) signaling, autophagic activity, epithelial-mesenchymal transition (EMT) and regulating the expression level of angiogenesis-related protein vascular endothelial growth factor A (VEGF-A), proto-oncogene c-Myc and prostate-specific antigen (PSA). Additionally, we determined that it exhibited synergistic action with cisplatin and significantly enhanced apoptotic cell death in PCa cells. Present findings suggest that ASX may be a potent adjuvant therapeutic option in PCa treatment when used alone or combined with chemotherapeutics. Schematic illustration of the biochemical activity of astaxanthin and its combination with cisplatin.

Keywords:  Apoptosis; Astaxanthin; Autophagy; Prostate cancer; Unfolded protein response

DOI:  https://doi.org/10.1007/s11418-023-01701-1
Nat Cell Biol. 2023 May 04.

SEL1L-HRD1 endoplasmic reticulum-associated degradation controls STING-mediated innate immunity by limiting the size of the activable STING pool.

Yewei Ji, Yuan Luo, Yating Wu, Yao Sun, Lianfeng Zhao, Zhen Xue, Mengqi Sun, Xiaoqiong Wei, Zinan He, Shuangcheng Alivia Wu, Liangguang Leo Lin, You Lu, Lei Chang, Fei Chen, Siyu Chen, Wei Qian, Xiaoxi Xu, Shengnuo Chen, Dongli Pan, Zhangsen Zhou, Sheng Xia, Chih-Chi Andrew Hu, Tingbo Liang, Ling Qi.

Stimulator of interferon genes (STING) orchestrates the production of proinflammatory cytokines in response to cytosolic double-stranded DNA; however, the pathophysiological significance and molecular mechanism underlying the folding and maturation of nascent STING protein at the endoplasmic reticulum (ER) remain unknown. Here we report that the SEL1L-HRD1 protein complex-the most conserved branch of ER-associated degradation (ERAD)-is a negative regulator of the STING innate immunity by ubiquitinating and targeting nascent STING protein for proteasomal degradation in the basal state. SEL1L or HRD1 deficiency in macrophages specifically amplifies STING signalling and immunity against viral infection and tumour growth. Mechanistically, nascent STING protein is a bona fide substrate of SEL1L-HRD1 in the basal state, uncoupled from ER stress or its sensor inositol-requiring enzyme 1α. Hence, our study not only establishes a key role of SEL1L-HRD1 ERAD in innate immunity by limiting the size of the activable STING pool, but identifies a regulatory mechanism and therapeutic approach to targeting STING.

DOI: https://doi.org/10.1038/s41556-023-01138-4
Front Immunol. 2023 ;14 1125759

Inhibition of neutrophil extracellular trap formation attenuates NLRP1-dependent neuronal pyroptosis via STING/IRE1α pathway after traumatic brain injury in mice.

Yiyao Cao, Mingming Shi, Liang Liu, Yan Zuo, Haoran Jia, Xiaobin Min, Xilei Liu, Zhijuan Chen, Yuan Zhou, Shenghui Li, Guili Yang, Xiao Liu, Quanjun Deng, Fanglian Chen, Xin Chen, Shu Zhang, Jianning Zhang.

  Introduction: Increased neutrophil extracellular trap (NET) formation has been reported to be associated with cerebrovascular dysfunction and neurological deficits in traumatic brain injury (TBI). However, the biological function and underlying mechanisms of NETs in TBI-induced neuronal cell death are not yet fully understood.Methods: First, brain tissue and peripheral blood samples of TBI patients were collected, and NETs infiltration in TBI patients was detected by immunofluorescence staining and Western blot. Then, a controlled cortical impact device was used to model brain trauma in mice, and Anti-Ly6G, DNase, and CL-amidine were given to reduce the formation of neutrophilic or NETs in TBI mice to evaluate neuronal death and neurological function. Finally, the pathway changes of neuronal pyroptosis induced by NETs after TBI were investigated by administration of peptidylarginine deiminase 4 (a key enzyme of NET formation) adenovirus and inositol-requiring enzyme-1 alpha (IRE1α) inhibitors in TBI mice.
Results: We detected that both peripheral circulating biomarkers of NETs and local NETs infiltration in the brain tissue were significantly increased and had positive correlations with worse intracranial pressure (ICP) and neurological dysfunction in TBI patients. Furthermore, the depletion of neutrophils effectively reduced the formation of NET in mice subjected to TBI. we found that degradation of NETs or inhibition of NET formation significantly inhibited nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing 1 (NLRP1) inflammasome-mediated neuronal pyroptosis after TBI, whereas these inhibitory effects were abolished by cyclic GMP-AMP (cGAMP), an activator of stimulating Interferon genes (STING). Moreover, overexpression of PAD4 in the cortex by adenoviruses could aggravate NLRP1-mediated neuronal pyroptosis and neurological deficits after TBI, whereas these pro-pyroptotic effects were rescued in mice also receiving STING antagonists. Finally, IRE1α activation was significantly upregulated after TBI, and NET formation or STING activation was found to promote this process. Notably, IRE1α inhibitor administration significantly abrogated NETs-induced NLRP1 inflammasome-mediated neuronal pyroptosis in TBI mice.
Discussion: Our findings indicated that NETs could contribute to TBI-induced neurological deficits and neuronal death by promoting NLRP1-mediated neuronal pyroptosis. Suppression of the STING/ IRE1α signaling pathway can ameliorate NETs-induced neuronal pyroptotic death after TBI.

Keywords:  IRE1α; NLRP1; STING; neutrophil extracellular trap; pyroptosis; traumatic brain injury

DOI:  https://doi.org/10.3389/fimmu.2023.1125759