bims-unfpre 2024-06-02 papers

bims-unfpre

Biomed News

on Unfolded protein response

Issue of 2024–06–02
eight papers selected by
Susan Logue, University of Manitoba

Multiple Unfolded Protein Response pathways cooperate to link cytosolic dsDNA release to Stimulator of Interferon Gene (STING) activation.
Insulin-degrading enzyme inhibition increases the unfolded protein response and favours lipid accumulation in the liver.
Emerging insights into the role of NLRP3 inflammasome and endoplasmic reticulum stress in renal diseases.
Protein disulfide isomerase-9 interacts with the lumenal region of the transmembrane endoplasmic reticulum stress sensor kinase, IRE1, to modulate the unfolded protein response in Arabidopsis.
CHOP-mediated IL-23 overexpression does not drive colitis in experimental spondyloarthritis.
The short-chain fatty acid propionate prevents ox-LDL-induced coronary microvascular dysfunction by alleviating endoplasmic reticulum stress in HCMECs.
A novel BAG5 variant impairs the ER stress response pathway, causing dilated cardiomyopathy and arrhythmia.
Targeting Cancer Mitochondria by Inducing an Abnormal Mitochondrial Unfolded Protein Response Leads to Tumor Suppression.

bioRxiv. 2024 May 14. pii: 2024.05.10.593557. [Epub ahead of print]

Multiple Unfolded Protein Response pathways cooperate to link cytosolic dsDNA release to Stimulator of Interferon Gene (STING) activation.

Tiancheng Hu, Yiping Liu, Jeremy Fleck, Cason King, Elaine Schalk, Zhenyu Zhang, Andrew Mehle, Judith A Smith.

The double-stranded DNA (dsDNA) sensor STING has been increasingly implicated in responses to "sterile" endogenous threats and pathogens without nominal DNA or cyclic di-nucleotide stimuli. Previous work showed an endoplasmic reticulum (ER) stress response, known as the unfolded protein response (UPR), activates STING. Herein, we sought to determine if ER stress generated a STING ligand, and to identify the UPR pathways involved. Induction of IFN-β expression following stimulation with the UPR inducer thapsigargin (TPG) or oxygen glucose deprivation required both STING and the dsDNA-sensing cyclic GMP-AMP synthase (cGAS). Furthermore, TPG increased cytosolic mitochondrial DNA, and immunofluorescence visualized dsDNA punctae in murine and human cells, providing a cGAS stimulus. N-acetylcysteine decreased IFN-β induction by TPG, implicating reactive oxygen species (ROS). However, mitoTEMPO, a mitochondrial oxidative stress inhibitor did not impact TPG-induced IFN. On the other hand, inhibiting the inositol requiring enzyme 1 (IRE1) ER stress sensor and its target transcription factor XBP1 decreased the generation of cytosolic dsDNA. iNOS upregulation was XBP1-dependent, and an iNOS inhibitor decreased cytosolic dsDNA and IFN-β, implicating ROS downstream of the IRE1-XBP1 pathway. Inhibition of the PKR-like ER kinase (PERK) pathway also attenuated cytoplasmic dsDNA release. The PERK-regulated apoptotic factor Bim was required for both dsDNA release and IFN-β mRNA induction. Finally, XBP1 and PERK pathways contributed to cytosolic dsDNA release and IFN-induction by the RNA virus, Vesicular Stomatitis Virus (VSV). Together, our findings suggest that ER stressors, including viral pathogens without nominal STING or cGAS ligands such as RNA viruses, trigger multiple canonical UPR pathways that cooperate to activate STING and downstream IFN-β via mitochondrial dsDNA release.

DOI: https://doi.org/10.1101/2024.05.10.593557
Br J Pharmacol. 2024 May 29.

Insulin-degrading enzyme inhibition increases the unfolded protein response and favours lipid accumulation in the liver.

Marine Andres, Nathalie Hennuyer, Khamis Zibar, Marie Bicharel-Leconte, Isabelle Duplan, Emmanuelle Enée, Emmanuelle Vallez, Adrien Herledan, Anne Loyens, Bart Staels, Benoit Deprez, Peter van Endert, Rebecca Deprez-Poulain, Steve Lancel.

   BACKGROUND AND PURPOSE: Nonalcoholic fatty liver disease refers to liver pathologies, ranging from steatosis to steatohepatitis, with fibrosis ultimately leading to cirrhosis and hepatocellular carcinoma. Although several mechanisms have been suggested, including insulin resistance, oxidative stress, and inflammation, its pathophysiology remains imperfectly understood. Over the last decade, a dysfunctional unfolded protein response (UPR) triggered by endoplasmic reticulum (ER) stress emerged as one of the multiple driving factors. In parallel, growing evidence suggests that insulin-degrading enzyme (IDE), a highly conserved and ubiquitously expressed metallo-endopeptidase originally discovered for its role in insulin decay, may regulate ER stress and UPR.
EXPERIMENTAL APPROACH: We investigated, by genetic and pharmacological approaches, in vitro and in vivo, whether IDE modulates ER stress-induced UPR and lipid accumulation in the liver.
KEY RESULTS: We found that IDE-deficient mice display higher hepatic triglyceride content along with higher inositol-requiring enzyme 1 (IRE1) pathway activation. Upon induction of ER stress by tunicamycin or palmitate in vitro or in vivo, pharmacological inhibition of IDE, using its inhibitor BDM44768, mainly exacerbated ER stress-induced IRE1 activation and promoted lipid accumulation in hepatocytes, effects that were abolished by the IRE1 inhibitors 4μ8c and KIRA6. Finally, we identified that IDE knockout promotes lipolysis in adipose tissue and increases hepatic CD36 expression, which may contribute to steatosis.
CONCLUSION AND IMPLICATIONS: These results unravel a novel role for IDE in the regulation of ER stress and development of hepatic steatosis. These findings pave the way to innovative strategies modulating IDE to treat metabolic diseases.

Keywords:  MASLD; endoplasmic reticulum stress; insulin‐degrading enzyme; liver; unfolded protein response

DOI:  https://doi.org/10.1111/bph.16436
Int Immunopharmacol. 2024 May 30. pii: S1567-5769(24)00862-2. [Epub ahead of print]136 112342

Emerging insights into the role of NLRP3 inflammasome and endoplasmic reticulum stress in renal diseases.

Yanting Zhang, Shiyun Guo, Xiaodi Fu, Qi Zhang, Honggang Wang.

  NLRP3 inflammasome is a key component of the innate immune system, mediating the activation of caspase-1, and the maturity and secretion of the pro-inflammatory cytokine interleukin (IL)-1beta (IL-1β) and IL-18 to cope with microbial infections and cell injury. The NLRP3 inflammasome is activated by various endogenous danger signals, microorganisms and environmental stimuli, including urate, extracellular adenosine triphosphate (ATP) and cholesterol crystals. Increasing evidence indicates that the abnormal activation of NLRP3 is involved in multiple diseases including renal diseases. Hence, clarifying the mechanism of action of NLRP3 inflammasome in different diseases can help prevent and treat various diseases. Endoplasmic reticulum (ER) is an important organelle which participates in cell homeostasis maintenance and protein quality control. The unfolded protein response (UPR) and ER stress are caused by the excessive accumulation of unfolded or misfolded proteins in ER to recover ER homeostasis. Many factors can cause ER stress, including inflammation, hypoxia, environmental toxins, viral infections, glucose deficiency, changes in Ca2+ level and oxidative stress. The dysfunction of ER stress participates in multiple diseases, such as renal diseases. Many previous studies have shown that NLRP3 inflammasome and ER stress play an important role in renal diseases. However, the relevant mechanisms are not yet fully clear. Herein, we focus on the current understanding of the role and mechanism of ER stress and NLRP3 inflammasome in renal diseases, hoping to provide theoretical references for future related researches.

Keywords:  Acute kidney injury; Apoptosis; Endoplasmic reticulum stress; NLRP3 inflammasome; Renal fibrosis

DOI:  https://doi.org/10.1016/j.intimp.2024.112342
Front Plant Sci. 2024 ;15 1389658

Protein disulfide isomerase-9 interacts with the lumenal region of the transmembrane endoplasmic reticulum stress sensor kinase, IRE1, to modulate the unfolded protein response in Arabidopsis.

Rina Carrillo, Kaela Iwai, Alena Albertson, Gabrielle Dang, David A Christopher.

  Environmental stressors disrupt secretory protein folding and proteostasis in the endoplasmic reticulum (ER), leading to ER stress. The unfolded protein response (UPR) senses ER stress and restores proteostasis by increasing the expression of ER-resident protein folding chaperones, such as protein disulfide isomerases (PDIs). In plants, the transmembrane ER stress sensor kinase, IRE1, activates the UPR by unconventionally splicing the mRNA encoding the bZIP60 transcription factor, triggering UPR gene transcription. The induced PDIs catalyze disulfide-based polypeptide folding to restore the folding capacity in the ER; however, the substrates with which PDIs interact are largely unknown. Here, we demonstrate that the Arabidopsis PDI-M subfamily member, PDI9, modulates the UPR through interaction with IRE1. This PDI9-IRE1 interaction was largely dependent on Cys63 in the first dithiol redox active domain of PDI9, and Cys233 and Cys107 in the ER lumenal domain of IRE1A and IRE1B, respectively. In vitro and in vivo, PDI9 coimmunoprecipitated with IRE1A and IRE1B. Moreover, the PDI9:RFP and Green Fluorescence Protein (GFP):IRE1 fusions exhibited strong interactions as measured by fluorescence lifetime imaging microscopy-fluorescence resonance energy transfer (FLIM-FRET) when coexpressed in mesophyll protoplasts. The UPR-responsive PDI9 promoter:mCherry reporter and the UPR-dependent splicing of the bZIP60 intron from the mRNA of the 35S::bZIP60-intron:GFP reporter were both significantly induced in the pdi9 mutants, indicating a derepression and hyperactivation of UPR. The inductions of both reporters were substantially attenuated in the ire1a-ire1b mutant. We propose a model in which PDI9 modulates the UPR through two competing activities: secretory protein folding and via interaction with IRE1 to maintain proteostasis in plants.

Keywords:  UPR-regulation; disulfide; endoplasmic reticulum stress; proteostasis; unfolded protein response

DOI:  https://doi.org/10.3389/fpls.2024.1389658
Sci Rep. 2024 05 29. 14(1): 12293

CHOP-mediated IL-23 overexpression does not drive colitis in experimental spondyloarthritis.

Fatemeh Navid, Tejpal Gill, Lilah Fones, Jules D Allbritton-King, Kelly Zhou, Isabel Shen, Jinny Van Doorn, Francesca LiCausi, Antony Cougnoux, Davide Randazzo, Stephen R Brooks, Robert A Colbert.

HLA-B27 is a major risk factor for spondyloarthritis (SpA), yet the underlying mechanisms remain unclear. HLA-B27 misfolding-induced IL-23, which is mediated by endoplasmic reticulum (ER) stress has been hypothesized to drive SpA pathogenesis. Expression of HLA-B27 and human β2m (hβ2m) in rats (HLA-B27-Tg) recapitulates key SpA features including gut inflammation. Here we determined whether deleting the transcription factor CHOP (Ddit3-/-), which mediates ER-stress induced IL-23, affects gut inflammation in HLA-B27-Tg animals. ER stress-mediated Il23a overexpression was abolished in CHOP-deficient macrophages. Although CHOP-deficiency also reduced Il23a expression in immune cells isolated from the colon of B27+ rats, Il17a levels were not affected, and gut inflammation was not reduced. Rather, transcriptome analysis revealed increased expression of pro-inflammatory genes, including Il1a, Ifng and Tnf in HLA-B27-Tg colon tissue in the absence of CHOP, which was accompanied by higher histological Z-scores. RNAScope localized Il17a mRNA to the lamina propria of the HLA-B27-Tg rats and revealed similar co-localization with Cd3e (CD3) in the presence and absence of CHOP. This demonstrates that CHOP-deficiency does not improve, but rather exacerbates gut inflammation in HLA-B27-Tg rats, indicating that HLA-B27 is not promoting gut disease through ER stress-induced IL-23. Hence, CHOP may protect rats from more severe HLA-B27-induced gut inflammation.

DOI: https://doi.org/10.1038/s41598-024-62940-0
PLoS One. 2024 ;19(5): e0304551

The short-chain fatty acid propionate prevents ox-LDL-induced coronary microvascular dysfunction by alleviating endoplasmic reticulum stress in HCMECs.

Dan Hong, Wen Tang, Fei Li, Yating Liu, Xiao Fu, Qin Xu.

Coronary microvascular dysfunction (CMD) is a critical pathogenesis of cardiovascular diseases. Lower endothelial nitric oxide synthase (eNOS) phosphorylation leads to reduced endothelium-derived relaxing factor nitric oxide (NO) generation, causing and accelerating CMD. Endoplasmic reticulum stress (ER stress) has been shown to reduce NO production in umbilical vein endothelial cells. Oxidized low-density lipoprotein (ox-LDL) damages endothelial cell function. However, the relationship between ox-LDL and coronary microcirculation has yet to be assessed. Short-chain fatty acid (SCFA), a fermentation product of the gut microbiome, could improve endothelial-dependent vasodilation in human adipose arterioles, but the effect of SCFA on coronary microcirculation is unclear. In this study, we found ox-LDL stimulated expression of ER chaperone GRP78. Further, we activated downstream PERK/eIF2a, IRE1/JNK, and ATF6 signaling pathways, decreasing eNOS phosphorylation and NO production in human cardiac microvascular endothelial. Furthermore, SCFA-propionate can inhibit ox-LDL-induced eNOS phosphorylation reduction and raise NO production; the mechanism is related to the inhibition of ER stress and downstream signaling pathways PERK/eIF2a, IRE1/JNK, and ATF6. In summary, we demonstrate that ox-LDL induced CMD by activating ER stress, propionate can effectively counteract the adverse effects of ox-LDL and protect coronary microcirculation function via inhibiting ER stress.

DOI: https://doi.org/10.1371/journal.pone.0304551
Sci Rep. 2024 05 25. 14(1): 11980

A novel BAG5 variant impairs the ER stress response pathway, causing dilated cardiomyopathy and arrhythmia.

Rutairat Wongong, Anusak Kijtawornrat, Chalurmpon Srichomthong, Siraprapa Tongkobpeth, Phichittra Od-Ek, Adjima Assawapitaksakul, Natarin Caengprasath, Apichai Khongphatthanayothin, Thantrira Porntaveetus, Vorasuk Shotelersuk.

  Pathogenic BAG5 variants recently linked to dilated cardiomyopathy (DCM) prompt further investigation into phenotypic, mutational, and pathomechanistic aspects. We explored the clinical and molecular characteristics of DCM associated with BAG5 variants, uncovering the consistently severe manifestations of the disease and its impact on the endoplasmic reticulum (ER) stress response. The analysis involved three siblings affected by DCM and arrhythmia, along with their four unaffected siblings, their unaffected father, and their mother who exhibited arrhythmia. The parents were consanguineous. Exome and Sanger sequencing identified a novel BAG5 variant, c.444_445delGA (p.Lys149AsnfsTer6), homozygous in affected siblings and heterozygous in parents and unaffected siblings. We generated heterozygous and homozygous Bag5 point mutant knock-in (KI) mice and evaluated cardiac pathophysiology under stress conditions, including tunicamycin (TN) administration. Bag5-/- mice displayed no abnormalities up to 12 months old and showed no anomalies during an exercise stress test. However, following TN injection, Bag5-/- mice exhibited significantly reduced left ventricular fractional shortening (LVFS) and ejection fraction (LVEF). Their cardiac tissues exhibited a notable increase in apoptotic cells, despite non-distinctive changes in CHOP and GRP78 levels. Interestingly, only Bag5 KI male mice demonstrated arrhythmia, which was more pronounced in Bag5-/- than in Bag5+/-males. Here, our study reveals a novel BAG5 mutation causing DCM by impairing the ER stress response, with observed sex-specific arrhythmia differences.

Keywords:  BAG5; Cardiac arrhythmia; Dilated cardiomyopathy; Endoplasmic reticulum stress; Tunicamycin; Unfolded protein response

DOI:  https://doi.org/10.1038/s41598-024-62764-y
Int J Med Sci. 2024 ;21(7): 1204-1212

Targeting Cancer Mitochondria by Inducing an Abnormal Mitochondrial Unfolded Protein Response Leads to Tumor Suppression.

Baoxiao Wang, Wenjun Chen, Qiqi Huang, Ye Chen, Yajing Wang.

  The mitochondrial unfolded protein response (UPRmt) is a pivotal cellular mechanism that ensures mitochondrial homeostasis and cellular survival under stress conditions. This study investigates the role of UPRmt in modulating the response of nasopharyngeal carcinoma cells to cisplatin-induced stress. We report that the inhibition of UPRmt via AEB5F exacerbates cisplatin cytotoxicity, as evidenced by increased lactate dehydrogenase (LDH) release and apoptosis, characterized by a surge in TUNEL-positive cells. Conversely, the activation of UPRmt with oligomycin attenuates these effects, preserving cell viability and reducing apoptotic markers. Immunofluorescence assays reveal that UPRmt activation maintains mitochondrial membrane potential and ATP production in the presence of cisplatin, countering the rise in reactive oxygen species (ROS) and inhibiting caspase-9 activation. These findings suggest that UPRmt serves as a cytoprotective mechanism in cancer cells, mitigating cisplatin-induced mitochondrial dysfunction and apoptosis. The data underscore the therapeutic potential of modulating UPRmt to improve the efficacy and reduce the side effects of cisplatin chemotherapy. This study provides a foundation for future research on the exploitation of UPRmt in cancer treatment, with the aim of enhancing patient outcomes by leveraging the cellular stress response pathways.

Keywords:  mitochondria, cisplatin, oxidative stress; mitochondrial unfolded protein response; nasopharyngeal carcinoma

DOI:  https://doi.org/10.7150/ijms.95624