Roles of XBP1s in Transcriptional Regulation of Target Genes

Microglial ER stress response via IRE1α regulates diet-induced metabolic imbalance and obesity in mice

BACKGROUND

Chronic high-fat diet (HFD) feeding triggers hypothalamic inflammation and systemic metabolic dysfunction associated with endoplasmic reticulum (ER) stress. Glial cells, specifically microglia and astrocytes, are central mediators of hypothalamic inflammation. However, the role of Inositol-Requiring Enzyme 1α (IRE1α), a primary ER stress sensor, in glial cells and its contributions to metabolic dysfunction remains elusive.

OBJECTIVES

To investigate the role of IRE1α in microglia in mediating HFD-induced metabolic dysfunction.

METHODS

Using novel conditional knockout mouse models (CX3CR1GFPΔIRE1 and TMEM119ERΔIRE1), we deleted IRE1α in immune cells or exclusively in microglia and studied its impact on metabolic health and hypothalamic transcriptional changes in mice fed with HFD for 16 weeks.

RESULTS

Deleting IRE1α in microglia significantly reduced LPS-induced pro-inflammatory cytokine gene expression in vitro. IRE1α deletion in microglia protected male mice from HFD-induced obesity, glucose intolerance, and hypothalamic inflammation, with no metabolic benefits observed in female mice. RNA-sequencing revealed significant transcriptional reprogramming of the hypothalamus, including upregulation of genes related to mitochondrial fatty acid oxidation, metabolic adaptability, and anti-inflammatory responses.

CONCLUSIONS

Our findings reveal that IRE1α-mediated ER stress response in microglia significantly contributes to hypothalamic inflammation and systemic metabolic dysfunction in response to HFD, particularly in males, demonstrating an important role of microglial ER stress response in diet-induced obesity and metabolic diseases.

PSP205, a Novel Phenyl Sulfonyl Piperidine, Induces Apoptotic Cell Death in Colon Cancer by Modulating Coat Protein Complex-Mediated Vesicle Trafficking

The endoplasmic reticulum (ER) stress and autophagic pathways offer attractive targets for the development of new cancer drugs. Here, we identified a novel phenyl sulfonyl piperidine, PSP205, that induces prolonged ER-stress-mediated autophagy and apoptosis in colon cancer cells. Transcriptome analysis of cells exposed to PSP205 unveiled transcriptional upregulation of genes associated with the ER stress response or unfolded protein response (UPR), in addition to vesicle transport. Among the top upregulated genes, DNAJB9, XBP1, PDIA4, HSPA5, SEC24D, and SEC11C are implicated in ER stress. Gene set enrichment analysis revealed the enrichment of gene sets involved in the UPR, mTORC1 signaling, hypoxia, the P53 pathway, apoptosis, and the ER-Golgi-vesicle-mediated transport pathway. Mechanistic studies showed that PSP205 acts on the IRE1-TRAF2-JNK pathway to modulate autophagic flux, leading to macroautophagy, ER-phagy, and deformation of Golgi. Our study also demonstrated that PSP205 decreases the expression of the COPI coat complex subunit beta 2 (COPB2) in the presence of COPB2 siRNA. Furthermore, PSP205 synergistically killed colon cancer cells in combination with proteasome and topoisomerase inhibitors. Cumulatively, our findings suggest that PSP205 targets cancer cells via a novel mechanism, specifically by decreasing the level of COPB2, which has not been extensively studied in the context of cancer therapy development and warrants further investigation.

Amyotrophic Lateral Sclerosis: Focus on Cytoplasmic Trafficking and Proteostasis

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease characterized by the pathological loss of upper and lower motor neurons. Whereas most ALS cases are caused by a combination of environmental factors and genetic susceptibility, in a relatively small proportion of cases, the disorder results from mutations in genes that are inherited. Defects in several different cellular mechanisms and processes contribute to the selective loss of motor neurons (MNs) in ALS. Prominent among these is the accumulation of aggregates of misfolded proteins or peptides which are toxic to motor neurons. These accumulating aggregates stress the ability of the endoplasmic reticulum (ER) to function normally, cause defects in the transport of proteins between the ER and Golgi, and impair the transport of RNA, proteins, and organelles, such as mitochondria, within axons and dendrites, all of which contribute to the degeneration of MNs. Although dysfunction of a variety of cellular processes combines towards the pathogenesis of ALS, in this review, we focus on recent advances concerning the involvement of defective ER stress, vesicular transport between the ER and Golgi, and axonal transport.

The significance of the activating transcription factor 6 gene in the pathogenesis of drug resistant cancer

Chemotherapy remains a cornerstone in cancer therapy, but its effectiveness is often hindered by the development of drug resistance, a significant factor contributing to over 90 % of cancer-related deaths worldwide. A critical aspect of this resistance involves chronic endoplasmic reticulum stress, which activates the unfolded protein response (UPR), mainly through the activation of Activating Transcription Factor 6 (ATF6). Elevated ATF6 expression has been found to correlate with poor survival outcomes and increased resistance to chemotherapy across several malignancies. This study specifically investigates the role of ATF6 in cancer pathogenesis, focusing on its involvement in resistance mechanisms and the progression of the disease. Given the complex interactions between the UPR and other cellular pathways, including the DNA damage response (DDR), our findings emphasize the potential of targeting ATF6 and UPR and DDR pathways as a novel therapeutic strategy. This approach could potentially overcome chemoresistance and improve outcomes in cancer treatment.

Hantaan virus infection induces human mucosal-associated invariant T cell pyroptosis through IRE1α pathway

Hantaan virus (HTNV) triggers an epidemic of hemorrhagic fever with renal syndrome (HFRS), which is predominantly prevalent in Asia. Mucosal-associated invariant T (MAIT) cells, categorized as innate-like T lymphocytes, perform crucial functions in the innate host defense mechanism during virus infection. We previously showed that MAIT cells played antiviral roles in vitro. But marked reduction of MAIT cells was present in the peripheral blood of HFRS patients. Till now, the role of MAIT cells in vivo and the mechanisms of HTNV-induced the MAIT cell deficiency have not yet been fully explored. In this study, by combining the clinical samples, MAIT deficiency mice and in vitro infected MAIT cell models, we find that pyroptosis was the main reason of MAIT cell loss in the peripheral blood of HFRS patients. The molecular mechanisms are related to the overload of calcium in the endoplasmic reticulum (ER) of MAIT cells, which subsequently induces inosital-requiring enzyme-1α (IRE1α)-mediated ER-stress and following pyroptosis. ER-stress inhibitor can reverse the pyroptosis of MAIT cells during HTNV infection. In conclusion, this study firstly reveals the underlying molecular mechanisms for the deficiency of MAIT cells during HTNV infection, and suggests a potential way to stabilize the MAIT cells population in HFRS.

Comprehensive analysis of the xbp1 gene in Pacific abalone Haliotis discus hannai: Structure, expression, and role in heat stress response

The present study explores the x-box binding protein 1 (xbp1) gene in Haliotis discus hannai (Pacific abalone), focusing on its structure, expression, and functional role under heat stress. Southern blot revealed two copies of xbp1 in the intestine and mantle, one in the gill and muscle, and no detection in the digestive gland. mRNA expression level of xbp1 was highest in the gill, followed by the mantle, intestine, and muscle, with the digestive gland showing the lowest expression. Actinomycin D treatment demonstrated that xbp1 mRNA stability varied among tissues, with slower degradation in the gill and mantle, while rapid degradation was observed in the digestive gland. Heat stress caused a 20 bp fragment removal from xbp1 mRNA, producing spliced xbp1 (xbp1s), with a conserved inositol-requiring enzyme 1α (IRE1α) cleavage motif (5'- CAGCACCUGCUGAUCCUCUG -3'). Genome walking was used to obtain the promoter sequences of downstream genes regulated by xbp1s. Through sequence conservation analysis, the binding sites of xbp1s on these promoters were identified in Pacific abalone. Yeast one-hybrid (Y1H) assays confirmed xbp1s binding to these sites, and morpholino oligonucleotides (MO) treatment effectively suppressed xbp1s production. Western blot analysis demonstrated that heat stress induced the expression of HDEL-related proteins, while MO injection significantly reduced their expression under both basal and heat stress conditions. Immunofluorescence analysis revealed decreased endoplasmic reticulum (ER) chaperone glucose-regulated protein 78 (GRP78) levels and increased apoptosis in MO-treated abalone under heat stress, suggesting a compromised ER stress response. These findings underscore XBP1's crucial role in regulating ER stress management and apoptotic processes, providing new insights into the functional significance of xbp1 in abalone's response to thermal stress.

FVB But Not B6 Mice Carrying the Thr92Ala-Dio2 Polymorphism Have Impaired Thyroid Hormonogenesis and Goiter

The Thr92Ala-Dio2 polymorphism is prevalent worldwide, with about 50% of the population carrying at least 1 allele. The Ala92-Dio2 allele encodes a less active type 2 deiodinase enzyme and has been associated with neurodegenerative diseases, hypertension, and insulin resistance. To understand why its phenotypic effects are variable across different populations, in this study we examined the impact of genetic background on the Thr92Ala-Dio2 polymorphism. We focused on the thyroid gland of 2 genetically distant mouse strains, the C57BL/6J (B6) and the FVB/N (FVB). While the B6-Ala92-Dio2 mice have no meaningful phenotype, the FVB-Ala92-Dio2 exhibit a goiter (about 2.3-fold heavier thyroid) with an about 1.7-fold enlarged thyroid follicular area and impaired hormonogenesis with reduced thyroglobulin content of T4 and T3, 35% to 50% lower serum T4, and about 3-fold elevated serum TSH levels. Notably, the FVB-Ala92-Dio2 thyroid glands showed transcriptional evidence of endoplasmic reticulum stress, unfolded protein response, autophagy, and apoptosis. Female FVB-Ala92-Dio2 mice exhibited a more pronounced thyroid phenotype than males. These findings underscore the critical role of genetic background in modulating the phenotype outcomes of the Thr92Ala-Dio2 polymorphism and highlight its potential implications for understanding variable disease susceptibility in human populations.

Cellular Stress Responses and Associated Diseases: A Focus on Heat Shock Proteins

Cellular stress response is the response of the cell at molecular level in order to combat various environmental stressors / viral infections. These stressors can be either intra or extracellular. In the beginning of the insult cell tries to recoup from these adverse events by various mechanism like heat shock protein response, unfolded protein response, mitochondrial stress signaling, DNA damage response etc. However, if these stressors exceed the cellular capacity to coup with it, it leads to programmed cell death and senescence. Also, chronic stress and cortisol released in response to cellular stress decreases telomerase activity which is needed to replenish telomeres which are protective casing at the end of a strand of DNA. Too low telomeres lead to cell death or cell become pro-inflammatory leading to aging process and other health associated risks like cardiovascular diseases neurodegenerative diseases, autoimmune diseases, cancers etc.

Differential neuronal vulnerability to C9orf72 repeat expansion driven by Xbp1-induced endoplasmic reticulum-associated degradation

Neurodegenerative diseases are characterized by the localized loss of neurons. Why cell death is triggered only in specific neuronal populations and whether it is the response to toxic insults or the initial cellular state that determines their vulnerability is unknown. To understand individual cell responses to disease, we profiled their transcriptional signatures throughout disease development in a Drosophila model of C9orf72 (G4C2) repeat expansion (C9), the most common genetic cause of frontotemporal dementia and amyotrophic lateral sclerosis. We identified neuronal populations specifically vulnerable or resistant to C9 expression and found an upregulation of protein homeostasis pathways in resistant neurons at baseline. Overexpression of Xbp1s, a key regulator of the unfolded protein response and a central node in the resistance network, rescues C9 toxicity. This study shows that neuronal vulnerability depends on the intrinsic transcriptional state of neurons and that leveraging resistant neurons' properties can boost resistance in vulnerable neurons.

Alterations in ether phospholipids metabolism activate the conserved UPR-Xbp1- PDIA3/ERp60 signaling to maintain intestinal homeostasis

Intestinal epithelium regeneration and homeostasis must be tightly regulated. Alteration of epithelial homeostasis is a major contributing factor to diseases such as colorectal cancer and inflammatory bowel diseases. Many pathways involved in epithelial regeneration have been identified, but more regulators remain undiscovered. Metabolism has emerged as an overlooked regulator of intestinal epithelium homeostasis. Using the model organism Drosophila melanogaster, we found that ether lipids metabolism is required to maintain intestinal epithelial homeostasis. Its dysregulation in intestinal progenitors causes the activation of the unfolded protein response of the endoplasmic reticulum (UPR) that triggers Xbp1 and upregulates the conserved disulfide isomerase PDIA3/ERp60. Activation of the Xbp1-ERp60 signaling causes Jak/Stat-mediated increase in progenitor cells, compromising epithelial barrier function and survival in males but not females. This study identified ether lipids-PDIA3/ERp60 as a key regulator of intestinal progenitor homeostasis in health that, if altered, causes pathological conditions in the intestinal epithelium.

Endoplasmic reticulum stress in acute pancreatitis: Exploring the molecular mechanisms and therapeutic targets

Acute pancreatitis (AP) is associated with multiple cellular mechanisms that trigger and or are triggered by the inflammatory injury and death of the acinar cells. One of the key mechanisms is the endoplasmic reticulum (ER) stress, which manifests as an accumulation of misfolded proteins within ER, an event that has proinflammatory and proapoptotic consequences. Hence, the degree of cell insult during AP could considerably depend on the signaling pathways that are upregulated during ER stress and its resulting dyshomeostasis such as C/EBP homologous protein (CHOP), cJUN NH2-terminal kinase (JNK), nuclear factor kappa B (NF-κB), and NOD-like receptor protein 3 (NLRP3) inflammasome. Exploring these molecular pathways is an interesting area for translational medicine as it may lead to identifying new therapeutic targets in AP. This review of the literature aims to shed light on the different roles of ER stress in the etiopathogenesis and pathogenesis of AP. Then, it specifically focuses on the therapeutic implications of ER stress in this context.

Modulation of Ire1-Xbp1 Defense Pathway in Encephalomyocarditis Virus-Infected HeLa Cells

A key contributor to the pathogenicity of viruses is their interaction with cellular defense mechanisms, including UPR (unfolded protein response) that counteracts the accumulation of misfolded proteins in the endoplasmic reticulum (known as ER stress). One of the UPR branches is mediated by the IRE1 (inositol-requiring enzyme 1) protein, which possesses protein kinase and RNase activities that facilitate the unconventional cytoplasmic splicing of XBP1 mRNA, leading to the upregulation of the XBP1 transcription factor. In this study, we demonstrate that Encephalomyocarditis Virus (Cardiovirus rueckerti) is able to suppress IRE1-dependent XBP1 activation. HeLa cells infection with EMCV resulted in the modulation of phosphorylated IRE1 levels throughout the infection cycle. Viral infection did not result in the accumulation of spliced XBP1 mRNA. Moreover, the addition of a chemical inducer of ER stress (dithiothreitol) to infected cells led to a markedly lower accumulation of spliced XBP1 mRNA as compared to the level of this mRNA in inducer-treated mock-infected cells. Thus, our results demonstrate the ability of picornaviruses to modulate another defensive activity of the host cell.

IRE1 is a promising therapeutic target in pancreatic cancer

[Figure: see text].

Cancer-Targeting Peptides Functionalized With Polyarginine Enables GRP78-Dependent Cell Uptake and siRNA Delivery Within the DU145 Prostate Cancer Cells

This study investigated a peptide-based GRP78-targeting strategy for short-interfering (si) RNA delivery in cancer cells. Synthetic fluorescein-labeled amphiphilic peptides composed of the hydrophobic cell surface (cs) GRP78-targeting and hydrophilic, polycationic arginine-rich cell penetrating peptides demonstrated GRP78-dependent cell uptake in the DU145 prostate cancer cells, and to a lesser extent in the non-cancerous human lung fibroblast WI-38 cell line. Mechanistic studies revealed energy-dependent GRP78 receptor-mediated endocytosis of the GRP78-targeting peptide with polyarginine (W1-R9). The cytosolic accumulation of this peptide underscored its potential utility in siRNA delivery. Peptide:siRNA complexes formed stably condensed nanoparticles, with calcium functioning as an ionic stabilizer and additive promoting endosomal siRNA escape for RNA interference (RNAi) activity. Preliminary peptide-based siRNA transfections in the DU145 cells demonstrated that GRP78 knockdown led to an interplay in between pro-survival and cell death outcomes under ER stress induction. Thus, the GRP78-targeting polyarginine peptides enables efficient cell uptake for specific siRNA delivery in the DU145 cells. This class of bio-active synthetic peptides is important for the investigation of cancer biology, leading to the innovation of cancer-targeted gene delivery and therapy approaches.

Age‑related changes in endoplasmic reticulum stress response‑associated protein expression in rat tibial nerves

In age-related peripheral neurodegeneration, changes in the promotion or inhibition of endoplasmic reticulum (ER) stress response related to the ubiquitin-proteasome degradation system (UPS), autophagy and apoptosis signaling factors during aging remain unclear. In the present study, the expression of ER stress response signaling-related protein factors was examined in tibial nerves during aging in rats. Tibial nerves were extracted from continuously housed rats at 20, 50, 70, 90 and 105 weeks of age. Expression of factors associated with ER stress-related degradation, including X-box binding protein 1 (XBP1s), eukaryotic translation initiation factor 2 subunit 1 (eIF2α), Beclin-1 (Becn1), and Caspase-3 (Casp3); ER stress-related repair, including binding immunoglobulin protein [also known as 78 kDa glucose-regulated protein (BiP/GRP78)], protein disulfide isomerase (PDI), brain-derived neurotrophic factor (BDNF) and the inflammatory cytokine IL6, was assessed by western blotting of tibial nerves from rats in each age group. Expression of XBP1s and Becn1, which promote UPS and autophagy, decreased significantly after 50 weeks of age. However, expression of eIF2α and Casp3, which inhibit new protein biosynthesis and promote apoptosis, increased significantly after 50 weeks. Expression of BiP/GRP78 and PDI, which are refolding factors for denatured proteins, showed a significant decrease after 50 (or 70) weeks of age. The expression of BDNF, a ligand protein for the repair cascade, showed a significant increase after 70 weeks of age, while that of IL6 increased significantly after 50 weeks of age. These results indicate that ER stress-related degradation (UPS and autophagy) and refolding repair functions are reduced in rat tibial nerves after 50 weeks, followed by enhanced apoptosis and inflammation. These findings shed light on the progression of age-related peripheral neurodegeneration in rats.

Endoplasmic reticulum stress and unfolded protein response in renal lipid metabolism

The endoplasmic reticulum (ER) is a crucial cellular organelle involved in protein synthesis, folding, modification, and transport. Exposure to internal and external stressors can induce endoplasmic reticulum stress (ERS), leading to abnormal protein folding and ER malfunction. This stress can disrupt lipid synthesis, metabolism, and transport processes. Fatty acid oxidation is the primary energy source for the renal system. When energy intake exceeds the storage capacity of adipose tissue, lipids accumulate abnormally in non-adipose tissues, including kidneys, liver, and pancreas. Lipids accumulate in the kidneys of nearly all cell types, including thylakoid membranous, pedunculated, and proximal renal tubular epithelial cells. Intracellular free fatty acids can significantly disrupt renal lipid metabolism, contributing to ischemia-reperfusion acute kidney injury, diabetic nephropathy, renal fibrosis, and lupus nephritis. Consequently, this study delineated the primary signaling pathways and mechanisms of the ERS-induced unfolded protein response, explored the mechanistic link between ERS and lipid metabolism, and elucidated its role in renal lipid metabolism. This study aimed to offer new perspectives on managing and treating renal disorders.

Targeting p38 MAPK: A potential bridge between ER stress and age-related bone loss

The endoplasmic reticulum (ER) is crucial in the development of numerous age-related bone disorders. Notably, ER stress can precipitate bone loss by orchestrating inflammatory responses, apoptosis, and autophagy through the activation of the p38 MAPK pathway. Age-related bone loss diseases pose a significant burden on society and healthcare as the global population ages. This review provides a comprehensive analysis of recent research advancements, delving into the critical role of ER stress-activated p38 MAPK in inflammation, apoptosis, and autophagy, as well as its impact on bone formation and bone resorption. This review elucidates the molecular mechanisms underlying the involvement of ER stress-activated p38 MAPK in osteoporosis, rheumatoid arthritis, periodontitis, and osteoarthritis and discusses the therapeutic potential of targeting p38 MAPK. Furthermore, this review provides a scientific foundation for new therapeutic strategies by highlighting prospective research directions.

Edaravone mitigates TDP-43 mislocalization in human amyotrophic lateral sclerosis neurons with potential implication of the SIRT1-XBP1 pathway

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron loss along with pathological mislocalization of TAR DNA-binding protein 43 (TDP-43), a protein implicated in RNA metabolism. Although edaravone, a free-radical scavenger, has been approved for ALS treatment, its precise mechanism of action is not fully understood, particularly in relation to TDP-43 pathology. Here, we investigated the effects of edaravone on induced pluripotent stem cell (iPSC)-derived motor neurons in a patient with ALS harboring a TDP-43 mutation. Our results demonstrated that edaravone significantly attenuated neurodegeneration, as evidenced by neurite preservation, neuronal cell death reduction, and correction of aberrant cytoplasmic localization of TDP-43. These neuroprotective effects were not observed with vitamin C, indicating a unique mechanism of action for edaravone, distinct from its antioxidative properties. RNA sequencing revealed that edaravone rapidly modulated gene expression, including protein quality control pathway, such as the ubiquitin-proteasome system. Further analysis identified X-box binding protein (XBP1), a key regulator of the endoplasmic reticulum stress response, as a critical factor in the therapeutic effects of edaravone. This study suggests that edaravone may offer a multifaceted therapeutic approach for ALS by targeting oxidative stress and TDP-43 mislocalization through distinct molecular pathways.

PERK-Olating Through Cancer: A Brew of Cellular Decisions

The type I protein kinase PERK is an endoplasmic reticulum (ER) transmembrane protein that plays a multifaceted role in cancer development and progression, influencing tumor growth, metastasis, and cellular stress responses. The activation of PERK represents one of the three signaling pathways induced during the unfolded protein response (UPR), which is triggered, in particular, in tumor cells that constitutively experience various intracellular and extracellular stresses that impair protein folding within the ER. PERK activation can lead to both pro-survival and proapoptotic outcomes, depending on the cellular context and the extent of ER stress. It helps the reprogramming of the gene expression in cancer cells, thereby ensuring survival in the face of oncogenic stress, such as replicative stress and DNA damage, and also microenvironmental challenges, including hypoxia, angiogenesis, and metastasis. Consequently, PERK contributes to tumor initiation, transformation, adaptation to the microenvironment, and chemoresistance. However, sustained PERK activation in cells can also impair cell proliferation and promote apoptotic death by various interconnected processes, including mitochondrial dysfunction, translational inhibition, the accumulation of various cellular stresses, and the specific induction of multifunctional proapoptotic factors, such as CHOP. The dual role of PERK in promoting both tumor progression and suppression makes it a complex target for therapeutic interventions. A comprehensive understanding of the intricacies of PERK pathway activation and their impact is essential for the development of effective therapeutic strategies, particularly in diseases like cancer, where the ER stress response is deregulated in most, if not all, of the solid and liquid tumors. This article provides an overview of the knowledge acquired from the study of animal models of cancer and tumor cell lines cultured in vitro on PERK's intracellular functions and their impact on cancer cells and their microenvironment, thus highlighting potential new therapeutic avenues that could target this protein.

Do wolframin, P-glycoprotein, and GRP78/BiP cooperate to alter the response of L1210 cells to endoplasmic reticulum stress or drug sensitivity?

In previous research, we revealed that murine leukemia cells L1210 with induced expression of P-glycoprotein (P-gp, a membrane drug transporter, product of the Abcb1 gene) are better able to withstand endoplasmic reticulum (ER) stress (ERS) than their P-gp negative counterparts. This was associated with increased GRP78/BiP expression and modulation of the expression of several other proteins active in the cellular response to ERS (like CHOP, spliced XBP1, 50-kDa ATF6 protein fragment and others) in P-gp positive cells. Wolframin is an ER transmembrane protein, product of the WFS1 gene whose mutations are associated with Wolfram syndrome. However, this protein is frequently overexpressed in cells undergoing ERS and its expression may accompany changes in the above ERS markers. Therefore, our aim in this work was to investigate wolframin expression in P-gp-negative and P-gp-positive murine leukemia L1210 cells in relation to ERS related proteins in normal or ERS condition. We induced ERS in cells either by blocking N-glycosylation in the ER with tunicamycin or by blocking ER Ca2+-ATPase activity with thapsigargin, as known ER stressors. The results of this paper demonstrated increased wolframin expression in P-gp positive cells compared to P-gp negative cells. Immunoprecipitation experiments revealed the formation of complexes between wolframin and ERS related proteins (PERK, ATF6 and GRP78/BiP), the amount of which varied depending on the presence of the above ER stressors.

Aflatoxin B1-Induced Apoptosis in Donkey Kidney via EndoG-Mediated Endoplasmic Reticulum Stress

Aflatoxin B1 (AFB1) is a prevalent environmental and forage contaminant that poses significant health risks to both humans and livestock due to its toxic effects on various organs and systems. Among its toxicological effects, nephrotoxicity is a hallmark of AFB1 exposure. However, the precise mechanisms underlying AFB1-induced kidney damage in donkeys remain poorly understood. To investigate this, we established a donkey model exposed to AFB1 by administering a diet supplemented with 1 mg AFB1/kg for 30 days. Kidney apoptosis was assessed using TUNEL staining, while gene expression and protein levels of Endonuclease G (EndoG), as well as genes related to endoplasmic reticulum (ER) stress and apoptosis, were quantified by RT-qPCR and Western blotting. Our findings indicate that AFB1 exposure resulted in significant kidney injury, apoptosis, and oxidative stress. Notably, AFB1 exposure upregulated the expression of EndoG and promoted its translocation to the ER, which subsequently induced ER stress and activated the mitochondrial apoptotic pathway. These results suggest that AFB1-induced kidney damage in donkeys is mediated through the oxidative stress and mitochondrial apoptosis pathways, primarily involving the EndoG-IRE1/ATF6-CHOP signaling axis.

NRF-mediated autophagy and UPR: Exploring new avenues to overcome cancer chemo-resistance

The development of chemo-resistance remains a significant hurdle in effective cancer therapy. NRF1 and NRF2, key regulators of redox homeostasis, play crucial roles in the cellular response to oxidative stress, with implications for both tumor growth and resistance to chemotherapy. This study delves into the dualistic role of NRF2, exploring its protective functions in normal cells and its paradoxical support of tumor survival and drug resistance in cancerous cells. We investigate the interplay between the PERK/NRF signaling pathway, ER stress, autophagy, and the unfolded protein response, offering a mechanistic perspective on how these processes contribute to chemoresistance. Our findings suggest that targeting NRF signaling pathways may offer new avenues for overcoming resistance to chemotherapeutic agents, highlighting the importance of a nuanced approach to redox regulation in cancer treatment. This research provides a molecular basis for the development of NRF-targeted therapies, potentially enhancing the efficacy of existing cancer treatments and offering hope for more effective management of resistant tumors.

Dynamic Modulation of IRE1α-XBP1 Signaling by Adenovirus

The abundant production of foreign proteins and nucleic acids during viral infection elicits a variety of stress responses in host cells. Viral proteins that accumulate in the endoplasmic reticulum (ER) can trigger the unfolded protein response (UPR), a coordinated signaling program that culminates in the expression of downstream genes that collectively restore protein homeostasis. The model pathogen adenovirus serotype 5 (HAdV5) activates the UPR via the signaling axis formed by inositol-requiring enzyme type 1 (IRE1α) and the X-box binding protein 1 (XBP1), a transcription factor required for immune function. Recent studies have suggested that IRE1α-XBP1 activity supports adenovirus replication. Here, we show that HAdV5 exerted opposing effects on IRE1α and XBP1. IRE1α was activated in response to HAdV5, but the production of the XBP1 isoform, XBP1s, was post-transcriptionally blocked. The tumor suppressor p53, which is eliminated by HAdV5 after infection, inhibited IRE1α activation. The de-repression of IRE1α following the degradation of p53 conceivably reflects a novel antiviral mechanism, which HAdV5 ultimately evades by co-opting IRE1α and suppressing XBP1s. Our findings illustrate the opposing mechanisms used by adenoviruses and their host cells to exert control over the UPR, a critical determinant of cell fate.

Epigenetic suppression of creatine kinase B in adipocytes links endoplasmic reticulum stress to obesity-associated inflammation

In white adipose tissue, disturbed creatine metabolism through reduced creatine kinase B (CKB) transcription contributes to obesity-related inflammation. However, the mechanisms regulating CKB expression in human white adipocytes remain unclear. By screening conditions perturbed in obesity, we identified endoplasmic reticulum (ER) stress as a key suppressor of CKB transcription across multiple cell types. Through follow-up studies, we found that ER stress through the IRE1-XBP1s pathway, promotes CKB promoter methylation via the methyltransferase DNMT3A. This epigenetic change represses CKB transcription, shifting metabolism towards glycolysis and increasing the production of the pro-inflammatory chemokine CCL2. We validated our findings in vivo, demonstrating that individuals living with obesity show an inverse relationship between CKB expression and promoter methylation in white adipocytes, along with elevated CCL2 secretion. Overall, our study uncovers a regulatory axis where ER stress drives inflammation in obesity by reducing CKB abundance, and consequently altering the bioenergetic state of the cell.

Upregulation of olfactory receptors and neuronal-associated genes highlights complex immune and neuronal dysregulation in Long COVID patients

A substantial portion of patients infected with SARS-CoV-2 experience prolonged complications, known as Long COVID (LC). A subset of these patients exhibits the most debilitating symptoms, similar to those defined in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). We performed bulk RNA sequencing (RNAseq) on the whole blood of LC with ME/CFS, at least 12 months post-onset of the acute disease, and compared them with controls. We found that LC patients had a distinct transcriptional profile compared to controls. Key findings include the upregulation of genes involved in immune dysregulation and neuronal development, such as Fezf2, BRINP2, HOXC12, MEIS2, ZFHX3, and RELN. These genes are linked to neuroinflammatory responses, cognitive impairments, and hematopoietic disturbances, suggesting ongoing neurological and immune disturbances in LC patients. RELN, encoding the Reelin protein, was notably elevated in LC patients, potentially serving as a biomarker for LC pathogenesis due to its role in inflammation and neuronal function. Immune cell analysis showed altered profiles in LC patients, with increased activated memory CD4 + T cells and neutrophils, and decreased regulatory T cells and NK cells, reflecting immune dysregulation. Changes in cytokine and chemokine expression further underscore the chronic inflammatory state in LC patients. Notably, a unique upregulation of olfactory receptors (ORs) suggest alternative roles for ORs in non-olfactory tissues. Pathway analysis revealed upregulation in ribosomal RNA processing, amino acid metabolism, protein synthesis, cell proliferation, DNA repair, and mitochondrial pathways, indicating heightened metabolic and immune demands. Conversely, downregulated pathways, such as VEGF signaling and TP53 activity, point to impaired tissue repair and cellular stress responses. Overall, our study underscores the complex interplay between immune and neuronal dysfunction in LC patients, providing insights into potential diagnostic biomarkers and therapeutic targets. Future research is needed to fully understand the roles and interactions of these genes in LC pathophysiology.

The Dual Role of Survival Genes in Neurons and Cancer Cells: a Strategic Clinical Application of DX2 in Neurodegenerative Diseases and Cancer

In cancer cells, survival genes contribute to uncontrolled growth and the survival of malignant cells, leading to tumor progression. Neurons are post-mitotic cells, fully differentiated and non-dividing after neurogenesis and survival genes are essential for cellular longevity and proper functioning of the nervous system. This review explores recent research findings regarding the role of survival genes, particularly DX2, in degenerative neuronal tissue cells and cancer cells. Survival gene DX2, an exon 2-deleted splice variant of AIMP2 (aminoacyl-tRNA synthetase-interacting multi-functional protein 2), was found to be overexpressed in various cancer types. The potential of DX2 inhibitors as an anti-cancer drug arises from its unique ability to interact with various oncoproteins, such as KRAS and HSP70. Meanwhile, AIMP2 has been reported as a multifunctional cell death-inducing gene, and survival gene DX2 directly and indirectly inhibits AIMP2-induced cell death. DX2 plays multifaceted survival roles in degenerating neurons via various signaling pathways, including PARP 1, TRAF2, and p53 pathways. It is noteworthy that genes that were previously classified as oncogenes, such as AKT and XBP1, are now being considered as curative transgenes for targeting neurodegenerative diseases. A strategic direction for clinical application of survival genes in neurodegenerative disease and in cancer is justified.

IFRD1 is required for maintenance of bladder epithelial homeostasis

The maintenance of homeostasis and rapid regeneration of the urothelium following stress are critical for bladder function. Here, we identify a key role for IFRD1 in maintaining urothelial homeostasis in a mouse model. We demonstrate that the murine bladder expresses IFRD1 at homeostasis, particularly in the urothelium, and its loss alters the global transcriptome with significant accumulation of endolysosomes and dysregulated uroplakin expression pattern. We show that IFRD1 interacts with mRNA-translation-regulating factors in human urothelial cells. Loss of Ifrd1 leads to disrupted proteostasis, enhanced endoplasmic reticulum (ER stress) with activation of the PERK arm of the unfolded protein response pathway, and increased oxidative stress. Ifrd1-deficient bladders exhibit urothelial cell apoptosis/exfoliation, enhanced basal cell proliferation, reduced differentiation into superficial cells, increased urothelial permeability, and aberrant voiding behavior. These findings highlight a crucial role for IFRD1 in urothelial homeostasis, suggesting its potential as a therapeutic target for bladder dysfunction.

Canagliflozin treatment prevents follicular exhaustion and attenuates hallmarks of ovarian aging in genetically heterogenous mice

Ovarian aging is characterized by declines in follicular reserve and the emergence of mitochondrial dysfunction, reactive oxygen species production, inflammation, and fibrosis, which eventually results in menopause. Menopause is associated with increased systemic aging and the development of numerous comorbidities; therefore, the attenuation of ovarian aging could also delay systemic aging processes in women. Recent work has established that the anti-diabetic drug Canagliflozin (Cana), a sodium-glucose transporter 2 inhibitor, elicits benefits on aging-related outcomes, likely through the modulation of nutrient-sensing pathways and metabolic homeostasis. Given that nutrient-sensing pathways play a critical role in controlling primordial follicle activation, we sought to determine if chronic Cana administration would delay ovarian aging and curtail the emergence of pathological hallmarks associated with reproductive senescence. We found that mice receiving Cana maintained their ovarian reserve through 12 months of age, which was associated with declines in primordial follicles FoxO3a phosphorylation, a marker of activation, when compared to the age-matched controls. Furthermore, Cana treatment led to decreased collagen, lipofuscin, and T cell accumulation at 12 months of age. Whole ovary transcriptomic and proteomic analyses revealed subtle improvements, predominantly in mitochondrial function and the regulation of cellular proliferation. Pathway analyses of the transcriptomic data revealed a downregulation in cell proliferation and mitochondrial dysfunction signatures, with an upregulation of oxidative phosphorylation. Pathway analyses of the proteomic data revealed declines in signatures associated with PI3K/AKT activity and lymphocyte accumulation. Collectively, we demonstrate that Cana treatment can delay ovarian aging in mice and could potentially have efficacy for delaying ovarian aging in women.

Dynamic modulation of IRE1α-XBP1 signaling by adenovirus

The abundant production of foreign proteins and nucleic acids during viral infection elicits a variety of stress responses in host cells. Viral proteins that accumulate in the endoplasmic reticulum (ER) can trigger the unfolded protein response (UPR), a coordinated signaling program that culminates in the expression of downstream genes that collectively restore protein homeostasis. The model pathogen adenovirus serotype 5 (HAdV5) activates the UPR via the signaling axis formed by inositol-requiring enzyme type 1 (IRE1α) and the X-box binding protein 1 (XBP1), a transcription factor required for immune function. Recent studies have suggested that IRE1α-XBP1 activity supports adenovirus replication. Here, we show that HAdV5 exerted opposing effects on IRE1α and XBP1. IRE1α was activated in response to HAdV5 but the production of the XBP1 isoform, XBP1s, was post-transcriptionally blocked. The tumor suppressor p53, which is eliminated by HAdV5 after infection, inhibited IRE1α activation. The de-repression of IRE1α following the degradation of p53 conceivably reflects a novel antiviral mechanism, which HAdV5 ultimately evades by suppressing XBP1s. Our findings highlight the defective antiviral defenses in cancer cells and further illustrate the opposing mechanisms used by adenoviruses and their host cells to exert control over the UPR, a critical determinant of cell fate.

Exploration of novel 20S proteasome activators featuring anthraquinone structures and their application in hypoxic cardiomyocyte protection

Under hypoxic conditions, the accumulation of misfolded proteins primarily relies on the autonomous activity of 20S proteasome for degradation. The buildup of toxic proteins in cardiomyocyte contribute to various cardiovascular diseases. Therefore, enhancing the 20S proteasome degradation capacity and restoring protein homeostasis in myocardial cells with small molecule activators represent a promising therapeutic strategy for the treatment of ischemic cardiomyopathy. In this study, the lead compound 8016-8398 was identified through virtual screening, and subsequent structure optimization resulted in a series of highly potent 20S proteasome activators. Intracellular protein degradation assessment revealed that these compounds possessed abilities to alleviate endoplasmic reticulum stress, as demonstrated by the luciferase reporter system. Additionally, selected compound B-03 significantly enhanced the survival rate of hypoxic-damaged cardiomyocytes. Mechanistic investigations verified B-03 rescued hypoxic damaged cardiomyocyte through apoptosis inhibition and proliferation promotion.

Endothelial Unfolded Protein Response-Mediated Cytoskeletal Effects

The endothelial semipermeable monolayers ensure tissue homeostasis, are subjected to a plethora of stimuli, and their function depends on cytoskeletal integrity and remodeling. The permeability of those membranes can fluctuate to maintain organ homeostasis. In cases of severe injury, inflammation or disease, barrier hyperpermeability can cause irreparable damage of endothelium-dependent issues, and eventually death. Elucidation of the signaling regulating cytoskeletal structure and barrier integrity promotes the development of targeted pharmacotherapies towards disorders related to the impaired endothelium (e.g., acute respiratory distress syndrome, sepsis). Recent reports investigate the role of unfolded protein response in barrier function. Herein we review the cytoskeletal components, the unfolded protein response function; and their interrelations on health and disorder. Moreover, we emphasize on unfolded protein response modulators, since they ameliorate illness related to endothelial leak.

The role of microRNAs regulation of endoplasmic reticulum stress in ischemia-reperfusion injury: A review

The endoplasmic reticulum (ER) is an important organelle in eukaryotic cells, responsible for a range of biological functions such as the secretion, modification and folding of proteins, maintaining Ca2+ homeostasis and the synthesis of steroids/lipids, secreted proteins and membrane proteins. When cells are affected by internal or external factors, including abnormal energy metabolism, disrupted Ca2+ balance, altered glycosylation, drug toxicity, and so on, the unfolded or misfolded proteins accumulate in the ER, leading to the unfolded protein response (UPR) and ER stress. The abnormal ER stress has been reported to be involved in various pathological processes. MicroRNAs (miRNAs) are non-coding RNAs with the length of approximately 19-25 nucleotides. They control the expression of multiple genes through posttranscriptional gene silencing in eukaryotes or some viruses. Increasing evidence indicates that miRNAs are involved in various cellular functions and biological processes, such as cell proliferation and differentiation, growth and development, and metabolic homeostasis. Hence, miRNAs participate in multiple pathological processes. Recently, many studies have shown that miRNAs play an important role by regulating ER stress in ischemia-reperfusion (I/R) injury, but the relevant mechanisms are not fully understood. In this review, we reviewed the current understanding of ER stress, as well as the biogenesis and function of miRNAs, and focused on the role of miRNAs regulation of ER stress in I/R injury, with the aim of providing new targets for the treatment of I/R injury.

Induction of LARP1B under endoplasmic reticulum stress and its regulatory role in proliferation of esophageal squamous cell carcinoma

Endoplasmic Reticulum Stress (ER stress) is a series of cellular responses activated in response to misfolded and unfolded protein accumulation and calcium imbalance in the ER lumen. Cumulating evidence emphasized the crucial involvement of ER stress in cell survival, death, and proliferation. However, the precise process remained obscure, especially in esophageal squamous cell carcinoma (ESCC). In the present study, LARP1B was detected to be one of the genes with significant differential expression in the ER stress ESCC cell model by RNA sequencing. ESCC cells exposed to ER stress stimulants (thapsigargin and tunicamycin) showed increased expression levels of LARP1B. ER stress initiated the expression of LARP1B through activation of the ERN1-XBP1 pathway, with XBP1 acting as a transcription factor to boost LARP1B transcription. Up-regulation of LARP1B was detected in ESCC tissues and cell lines. Suppression of LARP1B effectively curtailed the growth of cells and hindered the progression of the cell cycle. By detecting the expression of some genes closely related to proliferation and cell cycle regulation, CCND1 was identified as the main contributor to the cell proliferation induced by LARP1B. As an RNA-binding protein, LARP1B has the capability to attach to CCND1 mRNA, thereby increasing its stability. Inhibiting CCND1 might partially counterbalance the proliferation-promoting impact of LARP1B overexpression on ESCC cells. These findings indicate that, upon ER stress, up-regulation of LARP1B, triggered by ERN1-XBP1 pathway, facilitates proliferation of ESCC cells through enhancing the mRNA stability of CCND1, and LARP1B may be used as a potential therapeutic target of ESCC.

Bombyx mori UFBP1 regulates apoptosis and promotes BmNPV proliferation by affecting the expression of ER chaperone BmBIP

Ubiquitin-fold modifier 1 (UFM1) is attached to protein substrates through the sequential activity of an E1 (UBA5) - E2 (UFC1) - E3 (UFL1) cascade. UFBP1 is a conserved UFL1-interacting protein in mammals. However, to date, no study has been conducted on UFBP1 in silkworm. In this study, we identified a UFBP1 ortholog in the B. mori genome. Spatiotemporal expression profiles showed that BmUFBP1 expression was high in the midgut and fatbody, and at the moth stage. BmUFBP1 knockdown inhibited ER chaperone BmBIP expression and BmNPV proliferation, while BmUFBP1 overexpression increased BmNPV proliferation, and BmBIP rescued BmUFBP1-regulated BmNPV proliferation. Mechanistically, Apoptosis and ATF6 signaling are involved in BmUFBP1-regulated BmBIP expression and BmNPV proliferation. These results suggest that BmUFBP1 facilitates BmNPV proliferation via ATF6-BIP signaling, and provide a potential molecular target for BmNPV prevention and silkworm breeding.

Inhibition of IRE1α/XBP1 axis alleviates LPS-induced acute lung injury by suppressing TXNIP/NLRP3 inflammasome activation and ERK/p65 signaling pathway

BACKGROUND

Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a devastating clinical syndrome with high incidence and mortality rates. IRE1α-XBP1 pathway is one of the three major signaling axes of endoplasmic reticulum stress that is involved in inflammation, metabolism, and immunity. The role and potential mechanisms of IRE1α-XBP1 axis in ALI/ARDS has not well understood.

METHODS

The ALI murine model was established by intratracheal administration of lipopolysaccharide (LPS). Hematoxylin and eosin (H&E) staining and analysis of bronchoalveolar lavage fluid (BALF) were used to evaluate degree of lung injury. Inflammatory responses were assessed by ELISA and RT-PCR. Apoptosis was evaluated using TUNEL staining and western blot. Moreover, western blot, immunohistochemistry, and immunofluorescence were applied to test expression of IRE1α, XBP1, NLRP3, TXNIP, IL-1β, ERK1/2 and NF-κB p65.

RESULTS

The expression of IRE1α significantly increased after 24 h of LPS treatment. Inhibition of the IRE1α-XBP1 axis with 4µ8C notably improved LPS-induced lung injury and inflammatory infiltration, reduced the levels of IL-6, IL-1β, and TNF-α, and decreased cell apoptosis as well as the activation of the NLRP3 inflammasome. Besides, in LPS-stimulated Beas-2B cells, both 4µ8C and knockdown of XBP1 diminished the mRNA levels of IL-6 and IL-1B, inhibited cell apoptosis and reduced the protein levels of TXNIP, NLRP3 and secreted IL-1β. Mechanically, the phosphorylation and nuclear translocation of ERK1/2 and p65 were significantly suppressed by 4µ8C and XBP1 knockdown.

CONCLUSIONS

In summary, our findings suggest that IRE1α-XBP1 axis is crucial in the pathogenesis of ALI/ARDS, whose suppression could mitigate the pulmonary inflammatory response and cell apoptosis in ALI through the TXNIP/NLRP3 inflammasome and ERK/p65 signaling pathway. Our study may provide new evidence that IRE1α-XBP1 may be a promising therapeutic target for ALI/ARDS.

Endoplasmic reticulum stress triggers unfolded protein response as an antiviral strategy of teleost erythrocytes

Introduction

Fish nucleated red blood cells (RBCs), also known as erythrocytes, play a crucial role in maintaining immune system balance by modulating protein expression in response to various stimuli, including viral attack. This study explores the intriguing behavior of rainbow trout RBCs when faced with the viral hemorrhagic septicemia virus (VHSV), focusing on the endoplasmic reticulum (ER) stress and the unfolded protein response (UPR).

Methods

Rainbow trout RBCs were Ficoll-purified and exposed to ultraviolet (UV)-inactivated VHSV or live VHSV at different multiplicities of infection (MOIs). Using cryo-soft X-ray tomography (cryo-SXT), we uncovered structural and cellular modifications in RBCs exposed to UV-inactivated VHSV. Moreover, RBCs were treated with 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, to investigate its effect on viral replication. Quantitative real-time PCR was also used to analyze the expression of genes related to the UPR and other related cellular pathways.

Results and discussion

Beyond their antiviral response, RBCs undergo notable intracellular changes to combat the virus. Cryo-SXT highlighted a significant increase in the ER volume. This increase is associated with ER stress and the activation of the UPR pathway. Interestingly, VHSV replication levels augmented in RBCs under ER-stress inhibition by 4-PBA treatment, suggesting that rainbow trout RBCs tune up ER stress to control viral replication. Therefore, our findings suggested the induction of ER stress and subsequent activation UPR signaling in the antiviral response of RBCs to VHSV. The results open a new line of investigation to uncover additional mechanisms that may become novel cellular targets for the development of RBC-targeted antiviral strategies.

Tongguanteng injection exerts anti-osteosarcoma effects through the ER stress-associated IRE1/CHOP pathway

BACKGROUND

In China, Tongguanteng injection (TGT) is widely used in the treatment or adjuvant treatment of various types of cancer. However, the effect and mechanism of TGT in osteosarcoma is not clear.

METHODS

The 143B and MG-63 cells were treated with different concentrations of TGT. Cell proliferation, migration, invasion and apoptosis were detected using CCK8 assay, transwell assay and flow cytometry. Differentially expressed genes (DEGs) were screened using RNA sequencing (RNA-seq). The identified mRNA and protein expression associated with the IRE1/CHOP pathway was validated by RT-PCR and western blot assay. To explore the underlying mechanisms, 4-phenylbutyric acid (4-PBA) was selected as a specific endoplasmic reticulum (ER) stress inhibitor. Small interfering RNA (siRNA) or pEX-3-ERN1 plasmid was transfected into 143B cells to silence or overexpress IRE1, respectively. The potential downstream proteins, including CHOP, and apoptosis associated proteins, caspase-3 and PARP1 were determined. Furthermore, the effect of TGT was demonstrated in 143B cell tumor-bearing mice in vivo. H&E staining, TUNEL staining and immunohistochemistry were conducted in tumor tissues obtained from the xenograft mouse model.

RESULTS

TGT was shown to dramatically suppress the proliferation, migration and invasion, and induce apoptosis of osteosarcoma 143B and MG-63 cells in vitro. The identified DEGs included HSPA5 (encoding BiP) and ERN1 (encoding the IRE1 protein), as well as apoptosis-associated gene DDIT3 (encoding the CHOP protein). The term "IRE1-mediated unfolded protein response" was screened to be the most enriched biological process GO term. The expression of ER stress-associated proteins including ATF6, BiP, p-IRE1, XBP1s and CHOP, as well as apoptosis-associated cleaved caspase-3 and cleaved PARP1 proteins, was significantly upregulated by TGT treatment in osteosarcoma 143B cells, suggesting that TGT might promote the apoptosis of osteosarcoma 143B cells through the IRE1/CHOP pathway. Furthermore, knocking down IRE1 with si-IRE1 or inhibiting of ER stress with 4-PBA suppressed the expression of ATF6, BiP, XBP1s and CHOP induced by TGT, as well as the expression of cleaved caspase-3 and cleaved PARP1. On the contrary, overexpressing IRE1 promoted CHOP expression and induced osteosarcoma cell apoptosis. Consistent with in vitro results, TGT dramatically inhibited the tumor growth and promoted the expression of p-IRE1 and CHOP in tumor-bearing mice.

CONCLUSION

The findings suggest that TGT exerts an anti-osteosarcoma effect in vitro and in vivo. The underlying mechanism might be associated with the activation of IRE1/CHOP pathway in ER stress. Our findings suggest that targeting IRE1/CHOP pathway might be a potential novel approach for osteosarcoma treatment.

A statistical mechanics investigation of unfolded protein response across organisms

Living systems rely on coordinated molecular interactions, especially those related to gene expression and protein activity. The Unfolded Protein Response is a crucial mechanism in eukaryotic cells, activated when unfolded proteins exceed a critical threshold. It maintains cell homeostasis by enhancing protein folding, initiating quality control, and activating degradation pathways when damage is irreversible. This response functions as a dynamic signaling network, with proteins as nodes and their interactions as edges. We analyze these protein-protein networks across different organisms to understand their intricate intra-cellular interactions and behaviors. In this work, analyzing twelve organisms, we assess how fundamental measures in network theory can individuate seed proteins and specific pathways across organisms. We employ network robustness to evaluate and compare the strength of the investigated protein-protein interaction networks, and the structural controllability of complex networks to find and compare the sets of driver nodes necessary to control the overall networks. We find that network measures are related to phylogenetics, and advanced network methods can identify main pathways of significance in the complete Unfolded Protein Response mechanism.

Exploring paraptosis as a therapeutic approach in cancer treatment

A variety of cell death pathways play critical roles in the onset and progression of multiple diseases. Paraptosis, a unique form of programmed cell death, has gained significant attention in recent years. Unlike apoptosis and necrosis, paraptosis is characterized by cytoplasmic vacuolization, swelling of the endoplasmic reticulum and mitochondria, and the absence of caspase activation. Numerous natural products, synthetic compounds, and newly launched nanomedicines have been demonstrated to prime cell death through the paraptotic program and may offer novel therapeutic strategies for cancer treatment. This review summarizes recent findings, delineates the intricate network of signaling pathways underlying paraptosis, and discusses the potential therapeutic implications of targeting paraptosis in cancer treatment. The aim of this review is to expand our understanding of this unique cell death process and explore the potential therapeutic implications of targeting paraptosis in cancer treatment.

Potential mitochondrial ROS-mediated damage induced by chitosan nanoparticles bee venom-loaded on cancer cell lines

Recently, numerous studies have confirmed the importance of chitosan nanoparticles (CNP) as a viable drug delivery carrier for increasing the efficacy of anticancer drugs in cancer treatment. It is a macromolecule and natural biopolymer compound, more stable and safer in use than metal nanoparticles. Bee venom (BV), a form of defense venom, has been shown to have anti-tumor, neuroprotective, anti-inflammatory, analgesic, and anti-infectivity properties. Moreover, the regulation of cell death has been linked to reactive oxygen species (ROS)-mediated cell apoptosis, which induces mitochondrial damage and ER stress through oxidative stress events. Therefore, this study aimed to illustrate the ROS-mediated effect on the cancer cells treatment with CNP-loaded BV (CNP-BV) and explained the adverse effects of ROS generation on Mitochondria and ER. We have found that the targeted CNP-BV were high in cytotoxicity against MCF-7 (IC50 437.2 μg/mL) and HepG2 (IC50 109.5 μg/mL) through the induction of massive generation of ROS, which in turn results in activating the mitochondrial cascade and ER stress. These results highlighted the role of ROS generation in inducing apoptosis in cancer cells.

Elucidation of the role of XBP1 in the progression of complete hydatidiform mole to invasive mole through RNA-seq

OBJECTIVE

A complete hydatidiform mole (CHM) is a common disease and is known to develop post-molar gestational trophoblast neoplasia (GTN). However, the molecular mechanisms underlying the progression of CHM to post-molar GTN remain largely unknown. In this study, we investigated the molecular factors associated with the progression using RNA-seq.

METHODS

We included 13 patients with CHM and performed RNA-seq using freshly frozen samples. We identified differentially expressed genes between patients who developed GTN (GTN group) and those who achieved spontaneous remission after uterine evacuation (SR group), and performed pathway analysis. Then, functional analyses were performed on choriocarcinoma (JAR and JEG-3) and CHM (Hmol1-3B and Hmol1-2C) cells. Moreover, we evaluated the in vivo tumorigenicity of XBP1-overexpressed Hmol1-3B cells.

RESULTS

The gene expression profiles were separated into two groups, and an upstream regulator analysis was performed using 281 differentially expressed genes. We focused on transcription factors and identified that 33 transcription factors were activated in the GTN group. Then, excluding those with low expression levels in clinical samples and cell lines, XBP1 was selected for further analysis. Additionally, XBP1 downregulation significantly decreased the migration and invasive abilities of choriocarcinoma cells, whereas XBP1 overexpression significantly increased the migration and invasive abilities of CHM cells. Furthermore, animal experiments showed that tumor weight and blood human chorionic gonadotropin (hCG) levels were significantly higher in the XBP1-overexpressing Hmol1-3B-bearing mice than those in the control mice.

CONCLUSION

RNA-seq identified XBP1 as a key factor in post-molar GTN, suggesting it contributes to the development of post-molar GTN.

Quantitative proteomics reveals the mechanism of endoplasmic reticulum stress-mediated pulmonary fibrosis in mice

Pulmonary fibrosis is a progressive disease that can lead to respiratory failure. Many types of cells are involved in the progression of pulmonary fibrosis. This study utilized quantitative proteomics to investigate the mechanism of TGF-β-induced fibrosis-like changes in mouse epithelial cells. Our findings revealed that TGF-β significantly impacted biological processes related to the endoplasmic reticulum, mitochondrion, and ribonucleoprotein complex. Pull-down assay coupled with proteomics identified 114 proteins that may directly interact with TGF-β, and their functions were related to mitochondria, translation, ubiquitin ligase conjugation, mRNA processing, and actin binding. Among them, 17 molecules were also found in different expression proteins (DEPs) of quantitative proteomic, such as H1F0, MED21, SDF2L1, DAD1, and TMX1. Additionally, TGF-β decreased the folded structure and the number of ribosomes in the endoplasmic reticulum and increased the expression of key proteins in the unfolded protein response, including HRD1, PERK, and ERN1. Overall, our study suggested that TGF-β induced fibrotic changes in mouse lung epithelial cells by ER stress and initiated the unfolded protein response through the PRKCSH/IRE1 and PERK/GADD34/CHOP signaling pathways.

Scalable identification of lineage-specific gene regulatory networks from metacells with NetID

The identification of gene regulatory networks (GRNs) is crucial for understanding cellular differentiation. Single-cell RNA sequencing data encode gene-level covariations at high resolution, yet data sparsity and high dimensionality hamper accurate and scalable GRN reconstruction. To overcome these challenges, we introduce NetID leveraging homogenous metacells while avoiding spurious gene-gene correlations. Benchmarking demonstrates superior performance of NetID compared to imputation-based methods. By incorporating cell fate probability information, NetID facilitates the prediction of lineage-specific GRNs and recovers known network motifs governing bone marrow hematopoiesis, making it a powerful toolkit for deciphering gene regulatory control of cellular differentiation from large-scale single-cell transcriptome data.

RTP801 interacts with the tRNA ligase complex and dysregulates its RNA ligase activity in Alzheimer's disease

RTP801/REDD1 is a stress-responsive protein overexpressed in neurodegenerative diseases such as Alzheimer's disease (AD) that contributes to cognitive deficits and neuroinflammation. Here, we found that RTP801 interacts with HSPC117, DDX1 and CGI-99, three members of the tRNA ligase complex (tRNA-LC), which ligates the excised exons of intron-containing tRNAs and the mRNA exons of the transcription factor XBP1 during the unfolded protein response (UPR). We also found that RTP801 modulates the mRNA ligase activity of the complex in vitro since RTP801 knockdown promoted XBP1 splicing and the expression of its transcriptional target, SEC24D. Conversely, RTP801 overexpression inhibited the splicing of XBP1. Similarly, in human AD postmortem hippocampal samples, where RTP801 is upregulated, we found that XBP1 splicing was dramatically decreased. In the 5xFAD mouse model of AD, silencing RTP801 expression in hippocampal neurons promoted Xbp1 splicing and prevented the accumulation of intron-containing pre-tRNAs. Finally, the tRNA-enriched fraction obtained from 5xFAD mice promoted abnormal dendritic arborization in cultured hippocampal neurons, and RTP801 silencing in the source neurons prevented this phenotype. Altogether, these results show that elevated RTP801 impairs RNA processing in vitro and in vivo in the context of AD and suggest that RTP801 inhibition could be a promising therapeutic approach.

Paneth cell TNF signaling induces gut bacterial translocation and sepsis

The cytokine tumor necrosis factor (TNF) plays important roles in limiting infection but is also linked to sepsis. The mechanisms underlying these paradoxical roles are unclear. Here, we show that TNF limits the antimicrobial activity of Paneth cells (PCs), causing bacterial translocation from the gut to various organs. This TNF-induced lethality does not occur in mice with a PC-specific deletion in the TNF receptor, P55. In PCs, TNF stimulates the IFN pathway and ablates the steady-state unfolded protein response (UPR), effects not observed in mice lacking P55 or IFNAR1. TNF triggers the transcriptional downregulation of IRE1 key genes Ern1 and Ern2, which are key mediators of the UPR. This UPR deficiency causes a significant reduction in antimicrobial peptide production and PC antimicrobial activity, causing bacterial translocation to organs and subsequent polymicrobial sepsis, organ failure, and death. This study highlights the roles of PCs in bacterial control and therapeutic targets for sepsis.

IRE1α inhibitor enhances paclitaxel sensitivity of triple-negative breast cancer cells

PURPOSE

Breast cancer is the most commonly diagnosed cancer in women, and triple-negative breast cancer (TNBC) accounts for approximately 15%-20% of all breast cancers. TNBC is highly invasive and malignant. Due to the lack of relevant receptor markers, the prognosis of TNBC is poor and the five-year survival rate is low. Paclitaxel is the first-line drug for the treatment of TNBC, which can inhibit cell mitosis. However, many patients develop drug resistance during treatment, leading to chemotherapy failure. Therefore, finding new therapeutic combinations to overcome TNBC drug resistance can provide new strategies for improving the survival rate of TNBC patients.

METHODS

Cell viability assay, RT-qPCR, Colony formation assay, Western blot, and Xenogeneic transplantation methods were used to investigate roles and mechanisms of IRE1α/XBP1s pathway in the paclitaxel-resistant TNBC cells, and combined paclitaxel and IRE1α inhibitor in the treatment of TNBC was examined in vitro and in vivo.

RESULTS

We found activation of UPR in paclitaxel-resistant cells, confirming that IRE1α/XBP1 promotes paclitaxel resistance in TNBC. In addition, we demonstrated that the combination of paclitaxel and IRE1α inhibitors can synergistically inhibit the proliferation of TNBC tumors both in vitro and in vivo,suggesting that IRE1α inhibitors combined with paclitaxel may be a new treatment option for TNBC.

CONCLUSIONS

In this study, we demonstrated the important role of IRE1α signaling in mediating paclitaxel resistance and identified that combination therapies targeting IRE1α signaling could overcome paclitaxel resistance and enhance chemotherapy efficacy.

MiR-34c-5p Inhibition Affects Bax/Bcl2 Expression and Reverses Bortezomib Resistance in Multiple Myeloma Cells

Developing resistance to anticancer drugs complicates the clinical treatment of multiple myeloma patients. Previous studies revealed a link between the unfolded protein response (UPR) and miRNAs with acquired drug resistance. This study aimed to determine the expression profile of XBP1, hsa-miR-34c-5p, hsa-miR-214, and hsa-miR-30c-2* in resistant and sensitive multiple myeloma cell lines to a proteasome inhibitor, bortezomib. After establishing bortezomib-resistant cells, the expression level of XBP1, hsa-miR-214, hsa-miR-34c-5p, and hsa-miR-30c-2* in both cell lines were assessed by qRT-PCR. Hsa-miR-34c-5p was suppressed to study its effect on the expression profile of Bax/Bcl-2. Statistical analysis was done by t-test in two clinically resistant and sensitive cells to bortezomib. MTT assay confirmed the creation of the resistant cell line. The qRT-PCR screening showed a significant difference between XBP1 and miR-34c-5p levels in resistant and sensitive cells. Following hsa-miR-34c-5p blockage, while Bax was overexpressed, Bcl-2 expression was reduced in the resistant cell line, overcoming cells resistant to bortezomib. Our findings demonstrate miR-34c-5p is differentially expressed between bortezomib-sensitive and -resistant MM cells. Inhibiting miR-34c-5p re-sensitized resistant cells to bortezomib by modulating Bax/Bcl-2 expression, suggesting this miRNA regulates apoptosis and drug resistance and may be a promising therapeutic target for overcoming proteasome inhibitor resistance in MM.

FGF23 and Cell Stress in SaOS-2 Cells-A Model Reflecting X-Linked Hypophosphatemia Dynamics

Our study investigates the impact of FGF23 overexpression on SaOS-2 cells to elucidate its role in cellular stress and morphology, contributing to the understanding of skeletal pathologies like X-linked hypophosphatemia (XLH). Using transmission electron microscopy and protein analysis (Western blot), we analyzed the rough endoplasmic reticulum (rER) and mitochondria in SaOS-2 cells with FGF23 overexpression compared to controls. We found significant morphological changes, including enlarged and elongated rER and mitochondria, with increased contact zones, suggesting enhanced interaction and adaptation to elevated protein synthesis and secretion demands. Additionally, we observed higher apoptosis rates of the cells after 24-72 h in vitro and upregulated proteins associated with ER stress and apoptosis, such as CHOP, XBP1 (spliced and unspliced), GRP94, eIF2α, and BAX. These findings indicate a robust activation of the unfolded protein response (UPR) and apoptotic pathways due to FGF23 overexpression. Our results highlight the critical role of ER and mitochondrial interactions in cellular stress responses and provide new insights into the mechanistic link between FGF23 signaling and cellular homeostasis. In conclusion, our study underscores the importance of analyzing UPR-related pathways in the development of therapeutic strategies for skeletal and systemic diseases and contributes to a broader understanding of diseases like XLH.

UPF3B modulates endoplasmic reticulum stress through interaction with inositol-requiring enzyme-1α

The unfolded protein response (UPR) is a conserved and adaptive intracellular pathway that relieves the endoplasmic reticulum (ER) stress by activating ER transmembrane stress sensors. As a consequence of ER stress, the inhibition of nonsense-mediated mRNA decay (NMD) is due to an increase in the phosphorylation of eIF2α, which has the effect of inhibiting translation. However, the role of NMD in maintaining ER homeostasis remains unclear. In this study, we found that the three NMD factors, up-frameshift (UPF)1, UPF2, or UPF3B, were required to negate the UPR. Among these three NMD factors, only UPF3B interacted with inositol-requiring enzyme-1α (IRE1α). This interaction inhibited the kinase activity of IRE1α, abolished autophosphorylation, and reduced IRE1α clustering for ER stress. BiP and UPF3B jointly control the activation of IRE1α on both sides of the ER membrane. Under stress conditions, the phosphorylation of UPF3B was increased and the phosphorylated sites were identified. Both the UPF3BY160D genetic mutation and phosphorylation at Thr169 of UPF3B abolished its interaction with IRE1α and UPF2, respectively, leading to activation of ER stress and NMD dysfunction. Our study reveals a key physiological role for UPF3B in the reciprocal regulatory relationship between NMD and ER stress.

Disentangling cell-intrinsic and extrinsic factors underlying evolution

A key goal of developmental biology is to determine the extent to which cells and organs develop autonomously, as opposed to requiring interactions with other cells or environmental factors. Chimeras have played a foundational role in this by enabling qualitative classification of cell-intrinsically vs. extrinsically driven processes. Here, we extend this framework to precisely decompose evolutionary divergence in any quantitative trait into cell-intrinsic, extrinsic, and intrinsic-extrinsic interaction components. Applying this framework to thousands of gene expression levels in reciprocal rat-mouse chimeras, we found that the majority of their divergence is attributable to cell-intrinsic factors, though extrinsic factors also play an integral role. For example, a rat-like extracellular environment extrinsically up-regulates the expression of a key transcriptional regulator of the endoplasmic reticulum (ER) stress response in some but not all cell types, which in turn strongly predicts extrinsic up-regulation of its target genes and of the ER stress response pathway as a whole. This effect is also seen at the protein level, suggesting propagation through multiple regulatory levels. Applying our framework to a cellular trait, neuronal differentiation, revealed a complex interaction of intrinsic and extrinsic factors. Finally, we show that imprinted genes are dramatically mis-expressed in species-mismatched environments, suggesting that mismatch between rapidly evolving intrinsic and extrinsic mechanisms controlling gene imprinting may contribute to barriers to interspecies chimerism. Overall, our conceptual framework opens new avenues to investigate the mechanistic basis of developmental processes and evolutionary divergence across myriad quantitative traits in any multicellular organism.