XBP-1 regulates a subset of endoplasmic reticulum resident chaperone genes in the unfolded protein response

Magnesium-assisted hydrogen improves isoproterenol-induced heart failure

Heart failure (HF) is a leading cause of mortality among patients with cardiovascular disease and is often associated with myocardial apoptosis and endoplasmic reticulum stress (ERS). While hydrogen has demonstrated potential in reducing oxidative stress and ERS, recent evidence suggests that magnesium may aid in hydrogen release within the body, further enhancing these protective effects. This study aimed to investigate the cardioprotective effects of magnesium in reducing apoptosis and ERS through hydrogen release in a rat model of isoproterenol (ISO)-induced HF. Magnesium was administered orally to ISO-induced HF rats, which improved cardiac function, reduced myocardial fibrosis and cardiac hypertrophy, and lowered the plasma levels of creatine kinase-MB, cardiac troponin-I, and N-terminal B-type natriuretic peptide precursor in ISO-induced HF rats. It also inhibited cardiomyocyte apoptosis by upregulating B-cell lymphoma-2, downregulating Bcl-2-associated X protein, and suppressing ERS markers (glucose-related protein 78, activating transcription factor 4, and C/EBP-homologous protein). Magnesium also elevated hydrogen levels in blood, plasma, and cardiac tissue, as well as in artificial gastric juice and pure water, where hydrogen release lasted for at least four hours. Additionally, complementary in vitro experiments were conducted using H9C2 cardiomyocyte injury models, with hydrogen-rich culture medium as the intervention. Hydrogen-rich culture medium improved the survival and proliferation of ISO-treated H9C2 cells, reduced the cell surface area, inhibited apoptosis, and downregulated ERS pathway proteins. However, the protective effects of hydrogen were negated by tunicamycin (an inducer of ERS) in H9C2 cells. In conclusion, magnesium exerts significant cardioprotection by mitigating ERS and apoptosis through hydrogen release effects in ISO-induced HF.

Do We Know Enough About the Safety Profile of Silver Nanoparticles in Oncology? A Focus on Novel Methods and Approaches

Silver nanoparticles (AgNPs) have emerged as promising agents in cancer diagnostics and/or therapy, demonstrating a lot of possible pharmacological actions. However, understanding the pharmacokinetics and safety profiles of nanoparticles, which is crucial for their clinical application, still raises many questions. Studies indicate that AgNPs can accumulate in tumour tissues, improving drug delivery and specificity. However, their interaction with biological systems necessitates thorough safety evaluations. Classical methods for assessing AgNPs' safety include cytotoxicity assays, genotoxicity tests, and histopathological examinations. However, novel techniques are emerging, such as advanced imaging and biomarker analysis, offering more precise toxicity assessments. Prediction models, including computational simulations and in silico analyses, are being developed to forecast AgNPs' toxicity profiles. These models aim to reduce reliance on animal testing and expedite the evaluation process. To mitigate potential risks associated with nanoparticle-based therapies, strategies such as surface modification, controlled release systems, and targeted delivery are being explored. These methods aim to enhance therapeutic efficacy while minimizing adverse effects. The main aim of this review article is to describe AgNPs from the point of view of their pharmacokinetic/toxicokinetic profile in the light of modern knowledge. Special attention will be given to novel methods for assessing the safety and toxicity profiles of AgNPs, providing insights into their interactions with cancer therapies and their potential clinical applications.

Small protein ERSP encoded by LINC02870 promotes triple negative breast cancer progression via IRE1α/XBP1s activation

Clinical treatment options for triple-negative breast cancer (TNBC) are currently limited to chemotherapy because of a lack of effective therapeutic targets. Recent evidence suggests that long noncoding RNAs (lncRNAs) encode bioactive peptides or proteins, thereby playing noncanonical yet significant roles in regulating cellular processes. However, the potential of lncRNA-translated products in cancer progression remains largely unknown. In this study, we identified a previously undocumented small protein encoded by the lncRNA LINC02870. This protein is localized at the endoplasmic reticulum (ER) and participates in ER stress, thus, we named it the endoplasmic reticulum stress protein (ERSP). ERSP was highly expressed in TNBC tissues, and elevated LINC02870 content was correlated with poor prognosis in TNBC patients. Loss of ERSP inhibited TNBC growth and metastasis both in vitro and in vivo. The pro-oncogenic effects of ERSP could be attributed to its selective activation of the IRE1α/XBP1s branch. ERSP enhances the unfolded protein response (UPR) by interacting with XBP1s, facilitating the nuclear accumulation of XBP1s, thereby promoting the expression of ER stress-related genes. These findings highlight the regulatory role of the lncRNA-encoded protein ERSP in ER stress and suggest that it is a potential therapeutic target for TNBC.

Development of an Adaptive, Economical, and Easy-to-Use SP3-TMT Automated Sample Preparation Workflow for Quantitative Proteomics

Liquid handling robots have been developed to automate various steps of the bottom-up proteomics workflow, however, protocols for the generation of isobarically labeled peptides remain limited. Existing methods often require costly specialty devices and are constrained by fixed workflows. To address this, we developed a cost-effective, flexible, automated sample preparation protocol for TMT-labeled peptides using the Biomek i5 liquid handler (Beckman Coulter). Our approach leverages single-pot solid-phase-enhanced sample preparation with paramagnetic beads to streamline protein cleanup and digestion. The protocol also allows for adjustment of trypsin concentration and peptide-to-TMT ratio to increase throughput and reduce costs, respectively. We compared our automated and manual 18-plex TMT-Pro labeling workflows by monitoring select protein markers of the unfolded protein response in pharmacologically activatable, engineered cell lines. Overall, the automated protocol demonstrated equivalent performance in peptide and protein identifications, digestion and labeling efficiency, and an enhancement in the dynamic range of TMT quantifications. Compared to the manual method, the Biomek protocol significantly reduces hands-on time and minimizes sample handling errors. The 96-well format additionally allows for the number of TMT reactions to be scaled up quickly without a significant increase in user interaction. Our optimized automated workflow enhances throughput, reproducibility, and cost-effectiveness, making it a valuable tool for high-throughput proteomics studies.

Impact of proteostasis workload on sensitivity to proteasome inhibitors in multiple myeloma

Genomic alterations and enormous monoclonal immunoglobulin production cause multiple myeloma to heavily depend on proteostasis mechanisms, including protein folding and degradation. These findings support the use of proteasome inhibitors for treating multiple myeloma and mantle cell lymphoma. Myeloma treatment has evolved, especially with the availability of new drugs, such as proteasome inhibitors, into therapeutic strategies for both frontline and relapsed/refractory disease settings. However, proteasome inhibitors are generally not effective enough to cure most patients. Natural resistance and eventual acquired resistance led to relapsed/refractory disease and poor prognosis. Advances in the understanding of cellular proteostasis and the development of innovative drugs that also target other proteostasis network components offer opportunities to exploit the intrinsic vulnerability of myeloma cells. This review outlines recent findings on the molecular mechanisms regulating cellular proteostasis pathways, as well as resistance, sensitivity, and escape strategies developed against proteasome inhibitors and provides a rationale and examples for novel combinations of proteasome inhibitors with FDA-approved drugs and investigational drugs targeting the NRF1 (NFE2L1)-mediated proteasome bounce-back response, redox homeostasis, heat shock response, unfolding protein response, autophagy, and VCP/p97 to increase proteotoxic stress, which can improve the efficacy of antimyeloma therapy based on proteasome inhibitors.

Cadmium induces autophagy via IRE1 signaling pathway activated by Ca2 + in GC-2spd cells

Cadmium (Cd), an environmental toxicant, accumulates in the human body and damages the male reproductive system. To investigate the molecular mechanisms underlying Cd-induced reproductive toxicity, we used GC-2spd cells and treated them with CdCl2. Additionally, we added 2-APB (an inhibitor of the IP3R) and STF-083010 (an inhibitor of IRE1) to investigate whether they could ameliorate Cd-induced reproductive toxicity. Confocal microscopy and flow cytometry confirmed that CdCl2-treated GC-2spd cells displayed imbalance of calcium homeostasis, with upregulation of the expression of the IP3R, a key pathway for endoplasmic reticulum (ER) Ca2+ release. Furthermore, the ER stress (ERS) effector protein IRE1 expression was also increased, suggesting that Cd activated ERS and the IRE1 pathway by disrupting calcium homeostasis. Previous studies have shown that ERS induces autophagy. We performed the MDC assay to detect autophagosome formation, revealing increased expression of autophagy-related proteins LC3-II/LC3-I and Beclin-1 in response to Cd treatment. In contrast, treatment with 2-APB and STF-083010 inhibited autophagy and mitigated cell death. This inhibitory effect may be due to 2-APB blocking IP3R-mediated Ca2+ release, alleviating imbalance of calcium homeostasis, while STF-083010 inhibits IRE1, restoring ER homeostasis and reducing autophagy. These findings suggest that imbalance of calcium homeostasis activates the IRE1 pathway-mediated ERS, leading to excessive autophagy and male reproductive toxicity. Conversely, the addition of 2-APB and STF-083010 reversed these effects, synergistically restoring intracellular Ca2+ homeostasis and inhibiting ERS to promote cell health. This study provides a new therapeutic strategy for Cd-induced male reproductive disorders.

Identification of a Selective Pharmacologic IRE1/XBP1s Activator with Enhanced Tissue Exposure

Activation of the IRE1/XBP1s signaling arm of the unfolded protein response (UPR) has emerged as a promising strategy to mitigate etiologically diverse diseases. Despite this promise, few compounds are available to selectively activate IRE1/XBP1s signaling to probe the biologic and therapeutic implications of this pathway in human disease. Recently, we identified the compound IXA4 as a highly selective activator of protective IRE1/XBP1s signaling. While IXA4 has proven useful for increasing IRE1/XBP1s signaling in cultured cells and mouse liver, the utility of this compound is restricted by its limited activity in other tissues. To broaden our ability to pharmacologically interrogate the impact of IRE1/XBP1s signaling in vivo, we sought to identify IRE1/XBP1s activators with greater tissue activity than IXA4. We reanalyzed 'hits' from the high throughput screen used to identify IXA4, selecting compounds from structural classes not previously pursued. We then performed global RNAseq to confirm that these compounds showed transcriptome-wide selectivity for IRE1/XBP1s activation. Functional profiling revealed compound IXA62 as a selective IRE1/XBP1s activator that reduced Aβ secretion from CHO7PA2 cells and enhanced glucose-stimulated insulin secretion from rat insulinoma cells, mimicking the effects of IXA4 in these assays. IXA62 robustly and selectively activated IRE1/XBP1s signaling in the liver of mice dosed compound intraperitoneally or orally. In treated mice, IXA62 showed broader tissue activity, relative to IXA4, inducing expression of IRE1/XBP1s target genes in additional tissues such as kidney and lung. Collectively, our results designate IXA62 as a selective IRE1/XBP1s signaling activating compound with enhanced tissue activity, which increases our ability to pharmacologically probe the biologic significance and potential therapeutic utility of enhancing adaptive IRE1/XBP1s signaling in vivo.

Feedback-responsive cell factories for dynamic modulation of the unfolded protein response

Engineering cell factories that support the production of large quantities of protein therapeutics remains a significant biomanufacturing challenge. The overexpression of secretory proteins causes proteotoxic stress, affecting cell viability and protein productivity. Proteotoxic stress leads to the activation of the Unfolded Protein Response (UPR), a series of signal transduction pathways regulating protein quality control mechanisms aimed at restoring homeostasis. Sustained UPR activation culminates with the induction of apoptosis. Current strategies for enhancing the production of therapeutic proteins have focused on the deregulated modulation of key components of the UPR. These strategies have resulted in limited and often protein-specific improvements as they may lead to adaptation and cell toxicity and do not account for natural population heterogeneities. We report here feedback-responsive cell factories that sense proteotoxic stress and, in response, modulate the UPR to enhance stress attenuation and delay cell death, addressing the limitations of current strategies. We demonstrate that our cell engineering approach enables dynamic UPR modulation upon proteotoxic stress. The sense-and-respond systems that mediate dynamic UPR modulation enhance the production of the therapeutic enzyme tissue plasminogen activator and the bispecific antibody blinatumomab. Our feedback-responsive cell factories provide an innovative strategy for dynamically adjusting the innate cellular stress response and enhancing therapeutic protein manufacturing.

Impact of ER stress and the unfolded protein response on Fabry disease

Fabry disease (FD) is a lysosomal storage disorder caused by pathogenic missense and nonsense variants in the α-galactosidase A (GLA) gene, leading to absent or reduced enzyme activity. The resulting lysosomal accumulation of the substrate globotriaosylceramide leads to progressive renal failure, cardiomyopathy with (malignant) cardiac arrhythmias and progressive heart failure as well as recurrent strokes, which significantly limits the life expectancy of patients affected with FD. There is increasing evidence that pathogenic GLA missense variants as well as formally benign GLA variants can cause retention in the endoplasmic reticulum (ER), resulting in ER stress, which in turn triggers an unfolded protein response (UPR) leading to cellular dysregulation including inflammation, irreversible cell damage, and apoptosis. This review aims to provide an update on the pathogenetic significance of ER stress and UPR in FD, current treatment options, including pharmaceutical and chemical chaperones, and an outlook on current research and future treatment options in FD.

Activation of the endoplasmic reticulum stress regulator IRE1α compromises pulmonary host defenses

The endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1α (IRE1α) is associated with lung infections where innate immune cells are drivers for progression and resolution ammatory cytokinesflammation. Yet, the role of IRE1α in pulmonary innate immune host defense during acute respiratory infection remains unexplored. Here, we found that activation of IRE1α in infected lungs compromises immunity against methicillin-resistant Staphylococcus aureus (MRSA)-induced primary and secondary pneumonia. Moreover, activation of IRE1α in MRSA-infected lungs and alveolar macrophages (AMs) leads to exacerbated production of inflammatory mediators followed by cell death. Ablation of myeloid IRE1α or global IRE1α inhibition confers protection against MRSA-induced pneumonia with improved survival, bacterial clearance, cytokine reduction, and lung injury. In addition, loss of myeloid IRE1α protects mice against MRSA-induced secondary to influenza pneumonia by promoting AM survival. Thus, activation of IRE1α is detrimental to pneumonia, and therefore, it shows potential as a target to control excessive unresolved lung inflammation.

Targeting MTHFD2 alters metabolic homeostasis and synergizes with bortezomib to inhibit multiple myeloma

Multiple myeloma (MM) is an incurable hematologic malignancy. While recent therapies have significantly improved survival in MM patients, drug resistance and refractory phenomenon underscores the urgent need of new therapeutic targets. Methylenetetrahydrofolate dehydrogenase 2(MTHFD2) has been widely reported as a potential and promising anti-cancer target, but its role and underlying mechanisms remain unclear in MM. We aimed to investigate the biologic function and mechanisms of MTHFD2 in MM. First, we demonstrated that MTHFD2 is overexpressed in MM and associated with poor prognosis. We then illustrated that targeting MTHFD2 exhibits anti-MM effects in vitro and in vivo. Mechanistically, targeting MTHFD2 inhibited glycolysis and mitochondrial respiration in MM cells. For the nonmetabolic function of MTHFD2, we found that MTHFD2 knockdown affected the unfolded protein response (UPR) via decreasing expression of the splice form of X-box binding protein 1 (XBP1s). Importantly, the level of MTHFD2 in MM cells was associated with sensitivity of bortezomib, and targeting MTHFD2 synergizes with bortezomib against MM in vitro and in vivo. In summary, our innovative findings suggest that MTHFD2 is a promising target for MM, targeting it alters metabolic homeostasis of MM and synergizes with bortezomib to inhibit MM.

Glucose sensing and the unfolded protein response

The unfolded protein response (UPR) is activated primarily upon alteration of protein folding in the endoplasmic reticulum (ER). This occurs under physiological situations that cause an abrupt increase in protein synthesis, or under redox and metabolic stresses. Among the latter, hyperglycemia and glucose scarcity have been identified as major modulators of UPR signaling. Indeed, the first mammalian UPR effector, the glucose-regulated protein 78, also known as BiP, was identified in response to glucose deprivation. Tunicamycin, arguably the most commonly used drug to induce ER stress responses in vitro and in vivo, is an inhibitor of N-glycosylation. We compile here evidence that the UPR is activated upon physiological and pathological conditions that alter glucose levels and that this is mostly mediated by alterations of protein N-glycosylation, ATP levels, or redox balance. The three branches of the UPR transduced by PERK/ATF4, IRE1/XBP1s, and ATF6, as well as non-canonical ER sensors such as SCAP/SREBP, sense ER protein glycosylation status driven by glucose and other glucose-derived metabolites. The outcomes of UPR activation range from restoring protein N-glycosylation and protein folding flux to stimulating autophagy, organelle recycling, and mitochondrial respiration, and in some cases, cell death. Anabolic responses to glucose levels are also stimulated by glucose through components of the UPR. Therefore, the UPR should be further studied as a potential biomarker and mediator of glucose-associated diseases.

Endoplasmic reticulum stress: A key player in immune cell regulation and autoimmune disorders

The endoplasmic reticulum (ER) is a large organelle, found in all eukaryotes, that is essential for normal cellular function. This function encompasses protein folding and quality control, post-translational modifications, lipid regulation, and the storage of intracellular calcium, among others. These diverse processes are essential for maintaining proteome stability. Therefore, a robust surveillance system is established under stress to ensure cell homeostasis. Sources of stress can originate from the cellular environment, including nutrient deprivation, hypoxia, and low pH, as well as from endogenous signals within the cell, such as metabolic challenges and increased demands for protein production. When cellular homeostasis is altered by one of these triggers, ER primary functions are altered which leads to the accumulation of misfolded proteins. These impaired proteins trigger the activation of the Unfolded Protein Response (UPR) pathway. This response aims at reducing ER stress by implementing the induction of complex programs to restore cell homeostasis. However, extended ER stress can modify the UPR response, shifting its signals from promoting survival to triggering pathways that reprogram or eliminate affected cells.

The unfolded protein response is a potential therapeutic target in pathogenic fungi

Pathogenic fungal infections cause significant morbidity and mortality, particularly in immunocompromised patients. The frequent emergence of multidrug-resistant strains challenges existing antifungal therapies, driving the need to investigate novel antifungal agents that target new molecular moieties. Pathogenic fungi are subjected to various environmental stressors, including pH, temperature, and pharmacological agents, both in natural habitats and the host body. These stressors elevate the risk of misfolded or unfolded protein production within the endoplasmic reticulum (ER) which, if not promptly mitigated, can lead to the accumulation of these proteins in the ER lumen. This accumulation triggers an ER stress response, potentially jeopardizing fungal survival. The unfolded protein response (UPR) is a critical cellular defense mechanism activated by ER stress to restore the homeostasis of protein folding. In recent years, the regulatory role of the UPR in pathogenic fungi has garnered significant attention, particularly for its involvement in fungal adaptation, regulation of virulence, and drug resistance. In this review, we comparatively analyze the UPRs of fungi and mammals and examine the potential utility of the UPR as a molecular antifungal target in pathogenic fungi. By clarifying the specificity and regulatory functions of the UPR in pathogenic fungi, we highlight new avenues for identifying potential therapeutic targets for antifungal treatments.

Cytosolic and endoplasmic reticulum chaperones inhibit wt-p53 to increase cancer cells' survival by refluxing ER-proteins to the cytosol

The endoplasmic reticulum (ER) is an essential sensing organelle responsible for the folding and secretion of almost one-third of eukaryotic cells' total proteins. However, environmental, chemical, and genetic insults often lead to protein misfolding in the ER, accumulating misfolded proteins, and causing ER stress. To solve this, several mechanisms were reported to relieve ER stress by decreasing the ER protein load. Recently, we reported a novel ER surveillance mechanism by which proteins from the secretory pathway are refluxed to the cytosol to relieve the ER of its content. The refluxed proteins gain new prosurvival functions in cancer cells, thereby increasing cancer cell fitness. We termed this phenomenon ER to CYtosol Signaling (or 'ERCYS'). Here, we found that in mammalian cells, ERCYS is regulated by DNAJB12, DNAJB14, and the HSC70 cochaperone SGTA. Mechanistically, DNAJB12 and DNAJB14 bind HSC70 and SGTA - through their cytosolically localized J-domains to facilitate ER-protein reflux. DNAJB12 is necessary and sufficient to drive this phenomenon to increase AGR2 reflux and inhibit wt-p53 during ER stress. Mutations in DNAJB12/14 J-domain prevent the inhibitory interaction between AGR2-wt-p53. Thus, targeting the DNAJB12/14-HSC70/SGTA axis is a promising strategy to inhibit ERCYS and impair cancer cell fitness.

Effects of the Small-Molecule ISRIB on the Rapid and Efficient Myelination of Oligodendrocytes in Human Stem Cell-Derived Cerebral Organoids in Patients With Leukoencephalopathy With Vanishing White Matter

INTRODUCTION

Leukoencephalopathy with vanishing white matter (VWM) is a rare genetic disorder caused by mutations in any one of the EIF2B1-5, which encode subunits of eukaryotic translation initiation factor 2B (eIF2B). Previous studies suggested that the dysfunction of astrocytes played a central role in the pathogenic mechanism of VWM. In addition, eIF2B participates in the unfolded protein response(UPR) by coordinating the integrated stress response (ISR). Higher susceptibility to endoplasmic reticulum stress (ERS) and abnormal overactivation of the unfolded protein response (UPR) were found in VWM, which led to logical deterioration and exacerbation of cell death. There are currently no specific treatments available for VWM.

AIM

Previous studies have successfully constructed three-dimensional brain organoids that can be used to study the development of neuronal cells during brain development. In this study, we aimed to develop a more rapid and efficient brain organoid model that would produce mature astrocytes, oligodendrocytes, and myelin within 8 weeks. The small-molecule ISR inhibitor (ISRIB) is a specific eIF2B activator by inhibiting the phosphorylation of eukaryotic translation initiation factor 2 (eIF2). Thus, ISRIB is used on eIF2B mutant organoids to determine its potential as a therapeutic approach for VWM.

RESULTS

We constructed EIF2B4 and EIF2B5 mutants as well as wild-type rapid myelinating oligodendrocyte brain organoids using human induced pluripotent stem cells (iPSCs). We observed mature astrocytes, oligodendrocytes, and myelin within 8 weeks, greatly shortening the culture period. Compared with the wild type, mutant organoids displayed a smaller size and contained increased immature and dysfunctional astrocytes, oligodendrocytes, and sparse myelin. Abnormal overactivation of the UPR pathway was also present in mutant cerebral organoids. Additionally, we found that the maturation and function of these cells in mutant organoids were significantly improved after ISRIB treatment, which also inhibited hyperactivation of the unfolded protein response (UPR) signaling pathway.

CONCLUSIONS

Our study established a rapid myelinating oligodendrocyte brain model in VWM for the first time, providing a more effective and tractable platform for further study of this condition and other white matter diseases. Furthermore, our findings suggested that ISRIB may have potential as a clinical treatment for VWM.

Role of C/EBP Homologous Protein (CHOP) and Nupr1 Interaction in Endoplasmic Reticulum Stress-Induced Apoptosis of Lens Epithelial Cells

Our study mainly analyzed the mechanism of C/EBP homologous protein (CHOP) and its interacting protein Nupr1 on endoplasmic reticulum stress (ERS) induced lens epithelial cells (LEC) apoptosis. Cell proliferation was detected by CCK-8. Apoptosis was detected by flow cytometry and TUNEL. Nupr1 expression was detected by RT-qPCR. The expressions of CHOP, Nupr1, apoptosis-related protein, and ERS-related protein were detected by Western blot. DCFH-DA probe was used to detect cell ROS. The SOD, GSH-PX, and MDA contents were detected by the kit. Co-IP was used to detect the interaction between CHOP and Nupr1. The morphology of the lens was detected by HE staining. The result shows that Tunicamycin (TU) can induce endoplasmic reticulum stress and apoptosis in LEC in a concentration-dependent manner. TU induction leads to the occurrence of CHOP nuclear translocation. Overexpression of CHOP can further enhance the inhibitory effect of TU on LEC proliferation and the promotion of apoptosis, while knockdown of CHOP has the opposite effect. CHOP and Nupr1 are interacting proteins, and knockdown of Nupr1 or addition of Nupr1 inhibitor ZZW-115 can reverse the effects of TU and overexpression of CHOP, respectively. It has been observed in animal experiments that treatment with oe-CHOP can further aggravate the pathological lesions of the rat lens, while ZZW-115 can reverse the effect of oe-CHOP to a certain extent and improve the lesions of the rat lens. Overall, CHOP interacts with Nupr1 to regulate apoptosis caused by ERS and mediate cataract progression in rats, and this study provides a new potential therapeutic target for the treatment of cataract.

Study on the potential impact of sustained high temperatures during non-breeding season on largemouth bass

With the growing scale of largemouth bass breeding, the demand for seedlings is increasing. As global temperatures rise, it is crucial to study the effects of high temperature their regulatory mechanisms in largemouth bass. In this study, we simulated a high water temperature (28 °C) in the non-breeding season in aquaculture ponds for 28 days to examine the growth, reproduction, metabolism, apoptosis, and methylation markers in largemouth bass; transcriptome analysis was also performed. The results showed no significant difference in body weight between male and female largemouth bass. However, the high-temperature exposed females had reduced growth hormone (GH) and estradiol (E2) levels and elevated cortisol levels. They also showed upregulated expression of AR, cyp19a, igf, fshβ, and lhβ in ovarian tissue. Transcriptomic comparisons between temperature treatments revealed 963 differentially expressed genes in females and 700 in males. Both the ECM receptor interaction and PPAR signaling pathways were significantly enriched. High-temperature enhanced the lipid metabolism process through the PPAR signaling pathway. High temperatures increased oxidative stress in females, which corresponded with increases in SOD, CAT, and GSH-Px, likely to counteract the excess reactive oxygen species. Moreover, endoplasmic reticulum stress was activated, indicated by increases in IRE1 and ATF6, leading to the upregulation of apoptosis-related genes and ovarian cell apoptosis. At high temperature, 5-MC%, demethylase, and methyltransferase were not different in females, while 5-MC% and methyltransferase were higher and demethylase was lower in males. In summary, sustained high temperature affected ovarian development by altering the expression of hormone and gonad related genes and inducing endoplasmic reticulum stress leading to ovarian cell apoptosis. However, low demethylase activity and high genome-wide methylation in the test is suggested that high temperatures may affect testis development via methylation, potentially impacting offspring production.

Dissecting Branch-Specific Unfolded Protein Response Activation in Drug-Tolerant BRAF-Mutant Melanoma using Data-Independent Acquisition Mass Spectrometry

Cells rely on the Unfolded Protein Response (UPR) to maintain ER protein homeostasis (proteostasis) when faced with elevated levels of misfolded and aggregated proteins. The UPR is comprised of three main branches-ATF6, IRE1, and PERK-that coordinate the synthesis of proteins involved in folding, trafficking, and degradation of nascent proteins to restore ER function. Dysregulation of the UPR is linked to numerous diseases, including neurodegenerative disorders, cancer, and diabetes. Despite its importance, identifying UPR targets has been challenging due to their heterogeneous induction, which varies by cell type and tissue. Additionally, defining the magnitude and range of UPR-regulated genes is difficult because of intricate temporal regulation, feedback between UPR branches, and extensive cross-talk with other stress-signaling pathways. To comprehensively identify UPR-regulated proteins and determine their branch specificity, we developed a data-independent acquisition (DIA) liquid-chromatography mass spectrometry (LC-MS) pipeline. Our optimized workflow improved identifications of low-abundant UPR proteins and leveraged an automated SP3-based protocol on the Biomek i5 liquid handler for label-free peptide preparation. Using engineered stable cell lines that enable selective pharmacological activation of each UPR branch without triggering global UPR activation, we identified branch-specific UPR proteomic targets. These targets were subsequently applied to investigate proteomic changes in multiple patient-derived BRAF-mutant melanoma cell lines treated with a BRAF inhibitor (PLX4720, i.e., vemurafenib). Our findings revealed differential regulation of the XBP1s branch of the UPR in the BRAF-mutant melanoma cell lines after PLX4720 treatment, likely due to calcium activation, suggesting that the UPR plays a role as a non-genetic mechanism of drug tolerance in melanoma. In conclusion, the validated branch-specific UPR proteomic targets identified in this study provide a robust framework for investigating this pathway across different cell types, drug treatments, and disease conditions in a high-throughput manner.

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.

Artificial enforcement of the unfolded protein response reduces disease features in multiple preclinical models of ALS/FTD

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are part of a spectrum of diseases that share several causative genes, resulting in a combinatory of motor and cognitive symptoms and abnormal protein aggregation. Multiple unbiased studies have revealed that proteostasis impairment at the level of the endoplasmic reticulum (ER) is a transversal pathogenic feature of ALS/FTD. The transcription factor XBP1s is a master regulator of the unfolded protein response (UPR), the main adaptive pathway to cope with ER stress. Here, we provide evidence of suboptimal activation of the UPR in ALS/FTD models under experimental ER stress. To artificially engage the UPR, we intracerebroventricularly administrated adeno-associated viruses (AAVs) to express the active form of XBP1 (XBP1s) in the nervous system of ALS/FTD models. XBP1s expression improved motor performance and extended lifespan of mutant SOD1 mice, associated with reduced protein aggregation. AAV-XBP1s administration also attenuated disease progression in models of TDP-43 and C9orf72 pathogenesis. Proteomic profiling of spinal cord tissue revealed that XBP1s overexpression improved proteostasis and modulated the expression of a cluster of synaptic and cell morphology proteins. Our results suggest that strategies to improve ER proteostasis may serve as a pan-therapeutic strategy to treat ALS/FTD.

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].

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

Development of an Adaptive, Economical, and Easy-to-Use SP3-TMT Automated Sample Preparation Workflow for Quantitative Proteomics

Liquid handling robots have been developed to automate various steps of the bottom-up proteomics workflow, however, protocols for the generation of isobarically labeled peptides remain limited. Existing methods often require costly specialty devices and are constrained by fixed workflows. To address this, we developed a cost-effective, flexible, automated sample preparation protocol for TMT-labeled peptides using the Biomek i5 liquid handler. Our approach leverages Single-Pot Solid-Phase-Enhanced Sample Preparation (SP3) with paramagnetic beads to streamline protein cleanup and digestion. The protocol also allows for adjustment of trypsin concentration and peptide-to-TMT ratio to increase throughput and reduce costs, respectively. We compared our automated and manual 18-plex TMT-Pro labeling workflows by monitoring select protein markers of the Unfolded Protein Response (UPR) in pharmacologically activatable, engineered cell lines. Overall, the automated protocol demonstrated equivalent performance in peptide and protein identifications, digestion and labeling efficiency, and an enhancement in the dynamic range of TMT quantifications. Compared to the manual method, the Biomek protocol significantly reduces hands-on time and minimizes sample handling errors. The 96-well format additionally allows for the number of TMT reactions to be scaled up quickly without a significant increase in user interaction. Our optimized automated workflow enhances throughput, reproducibility, and cost-effectiveness, making it a valuable tool for high-throughput proteomics studies.

Adaptation of Natural Killer Cells to Hypoxia: A Review of the Transcriptional, Translational, and Metabolic Processes

As important innate immune cells, natural killer (NK) cells play an essential role in resisting pathogen invasion and eliminating transformed cells. However, the hypoxic microenvironment caused by disease conditions is an important physicochemical factor that impairs NK cell function. With the increasing prominence of NK cells in immunotherapy, there has been a surge of interest in developing biological means through which NK cells may overcome the inhibition caused by hypoxia in disease conditions. Although the effects of hypoxic conditions in shaping the functions of NK cells have been increasingly recognized and investigated, reviews have been scantly. A comprehensive understanding of how NK cells adapt to hypoxia can provide valuable insights into how the functional capacity of NK cells may be restored. This review focuses on the functional alterations of NK cells in response to hypoxia. It delineates the mechanisms by which NK cells adapt to hypoxia at the transcriptional, metabolic, translational levels. Furthermore, given the complexity of the hypoxic microenvironment, we also elucidated the effects of key hypoxic metabolites on NK cells. Finally, this review discusses the current clinical therapies derived from targeting hypoxic NK cells. The study of NK cell adaptation to hypoxia has yielded new insights into immunotherapy. These insights may lead to development of novel strategies to improve the treatment of infectious diseases and cancer.

Signaling Pathways Involved in Acute Pancreatitis

Acute pancreatitis (AP) is a common digestive emergency with high morbidity and mortality. Over the past decade, significant progress has been made in understanding the mechanisms of AP, including oxidative stress, disruptions in calcium homeostasis, endoplasmic reticulum stress, inflammatory responses, and various forms of cell death. This review provides an overview of the typical signaling pathways involved and proposes the latest clinical translation prospects. These strategies are important for the early management of AP, preventing multi-organ injury, and improving the overall prognosis of the disease.

Mutations in unfolded protein response regulator ATF6 cause hearing and vision loss syndrome

Activating transcription factor 6 (ATF6) is a key regulator of the unfolded protein response (UPR) and is important for ER function and protein homeostasis in metazoan cells. Patients carrying loss-of-function ATF6 disease alleles develop the cone dysfunction disorder achromatopsia. The effect of loss of ATF6 function on other cell types, organs, and diseases in people remains unclear. Here, we report that progressive sensorineural hearing loss was a notable complaint in some patients carrying ATF6 disease alleles and that Atf6-/- mice also showed progressive auditory deficits affecting both sexes. In mice with hearing deficits, we found disorganized stereocilia on hair cells and focal loss of outer hair cells. Transcriptomics analysis of Atf6-/- cochleae revealed a marked induction of the UPR, especially through the protein kinase RNA-like endoplasmic reticulum kinase (PERK) arm. These findings identify ATF6 as an essential regulator of cochlear health and function. Furthermore, they support the idea that ATF6 inactivation in people causes progressive sensorineural hearing loss as part of a blindness-deafness genetic syndrome targeting hair cells and cone photoreceptors. Last, our genetic findings indicate that ER stress is an important pathomechanism underlying cochlear damage and hearing loss, with clinical implications for patient lifestyle modifications that minimize environmental and physiological sources of ER stress to the ear.

Ironomycin induces mantle cell lymphoma cell death by targeting iron metabolism addiction

Rationale: Mantle-cell lymphoma (MCL) remains an aggressive and incurable cancer. Accumulating evidence reveals that abnormal iron metabolism plays an important role in tumorigenesis and in cancer progression of many tumors. Based on these data, we searched to identify alterations of iron homeostasis in MCL that could be exploited to develop novel therapeutic strategies. Methods: Analysis of the iron metabolism gene expression profile of a cohort of patients with MCL enables the identification of patients with a poor outcome who might benefit from an iron homeostasis-targeted therapy. We analyzed the therapeutic interest of ironomycin, known to sequester iron in the lysosome and to induce ferroptosis. Results: In a panel of MCL cell lines, ironomycin inhibited MCL cell growth at nanomolar concentrations compared with conventional iron chelators. Ironomycin treatment resulted in ferroptosis induction and decreased cell proliferation rate, with a reduced percentage of cells in S-phase together with Ki67 and Cyclin D1 downregulation. Ironomycin treatment induced DNA damage response, accumulation of DNA double-strand breaks, and activated the Unfolded Protein Response (UPR). We validated the therapeutic interest of ironomycin in primary MCL cells of patients. Ironomycin demonstrated a significant higher toxicity in MCL cells compared to normal cells from the microenvironment. We tested the therapeutic interest of combining ironomycin with conventional treatments used in MCL. We identified a synergistic effect when ironomycin is combined with Ibrutinib, Bruton's tyrosine kinase (BTK) inhibitor, associated with a strong inhibition of B-Cell receptor (BCR) signaling. Conclusion: Altogether, these data underline that MCL patients my benefit from targeting iron homeostasis using ironomycin alone or in combination with conventional MCL treatments.

Unfolded protein response modulates Tyrosinase levels and melanin production during melanogenesis

BACKGROUND

Melanocytes protect the body from ultraviolet radiation by synthesizing melanin. Tyrosinase, a key enzyme in melanin production, accumulates in the endoplasmic reticulum (ER) during melanin synthesis, potentially causing ER stress. However, regulating ER function for melanin synthesis has been less studied than controlling Tyrosinase activity.

OBJECTIVE

This study investigates the regulatory mechanisms of melanin production, focusing on ER stress and the ER stress-induced response.

METHODS

B16 mouse melanoma cells induced to undergo melanogenesis were treated with unfolded protein response (UPR) inhibitors or chemical chaperones, and their effects on melanogenesis were analyzed.

RESULTS

During melanogenesis in B16 cells stimulated by alpha-melanocyte-stimulating hormone (α-MSH), ER stress and UPR activation occurred, accompanied by increased Tyrosinase protein. Reducing IRE1 and ATF6 branch activity lowered melanin levels, while chemical chaperone treatment restored melanin production and increased Tyrosinase levels.

CONCLUSION

UPR activation, linked to elevated Tyrosinase levels, influences melanin production during melanogenesis. Modulating UPR can regulate melanin synthesis and provides a potential new approach for treating pigmentation disorders.

Direct inhibition of tumor hypoxia response with synthetic transcriptional repressors

Many oncogenic transcription factors (TFs) are considered to be undruggable because of their reliance on large protein-protein and protein-DNA interfaces. TFs such as hypoxia-inducible factors (HIFs) and X-box-binding protein 1 (XBP1) are induced by hypoxia and other stressors in solid tumors and bind to unfolded protein response element (UPRE) and hypoxia-induced response element (HRE) motifs to control oncogenic gene programs. Here, we report a strategy to create synthetic transcriptional repressors (STRs) that mimic the basic leucine zipper domain of XBP1 and recognize UPRE and HRE motifs. A lead molecule, STR22, binds UPRE and HRE DNA sequences with high fidelity and competes with both TFs in cells. Under hypoxia, STR22 globally suppresses HIF1α binding to HRE-containing promoters and enhancers, inhibits hypoxia-induced gene expression and blocks protumorigenic phenotypes in triple-negative breast cancer (TNBC) cells. In vivo, intratumoral and systemic STR22 treatment inhibited hypoxia-dependent gene expression, primary tumor growth and metastasis of TNBC tumors. These data validate a novel strategy to target the tumor hypoxia response through coordinated inhibition of TF-DNA binding.

IRE1α-XBP1 safeguards hematopoietic stem and progenitor cells by restricting pro-leukemogenic gene programs

Hematopoietic stem cells must mitigate myriad stressors throughout their lifetime to ensure normal blood cell generation. Here, we uncover unfolded protein response stress sensor inositol-requiring enzyme-1α (IRE1α) signaling in hematopoietic stem and progenitor cells (HSPCs) as a safeguard against myeloid leukemogenesis. Activated in part by an NADPH oxidase-2 mechanism, IRE1α-induced X-box binding protein-1 (XBP1) mediated repression of pro-leukemogenic programs exemplified by the Wnt-β-catenin pathway. Transcriptome analysis and genome-wide mapping of XBP1 targets in HSPCs identified an '18-gene signature' of XBP1-repressed β-catenin targets that were highly expressed in acute myeloid leukemia (AML) cases with worse prognosis. Accordingly, IRE1α deficiency cooperated with a myeloproliferative oncogene in HSPCs to cause a lethal AML in mice, while genetic induction of XBP1 suppressed the leukemia stem cell program and activity of patient-derived AML cells. Thus, IRE1α-XBP1 signaling safeguards the integrity of the blood system by restricting pro-leukemogenic programs in HSPCs.

Resilience to Endoplasmic Reticulum Stress Mitigates Calcium-Dependent Membrane Hyperexcitability Underlying Late Disease Onset in SCA6

An enduring puzzle in many inherited neurological disorders is the late onset of symptoms despite expression of function-impairing mutant protein early in life. We examined the basis for onset of impairment in Spinocerebellar ataxia type 6 (SCA6), a canonical late-onset neurodegenerative ataxia which results from a polyglutamine expansion in the voltage gated calcium channel, Cav2.1. Cerebellar Purkinje cell spiking abnormalities are seen concurrent with motor impairment in SCA6 mice but the basis for these changes in spiking is unknown. We identify endoplasmic reticulum (ER) calcium depletion as the cause for Purkinje cell spiking abnormalities and that the impairments in Purkinje cell spiking are unrelated to Cav2.1 ion-flux function. Further, intact inhibitory neurotransmission in the cerebellar cortex is necessary for Purkinje neurons to exhibit spiking abnormalities in SCA6 mice. Based on serial cerebellar transcriptome analysis, we define a mechanism of disease that is related to ER stress. Further, our studies support a model whereby proteotoxicity from misfolded mutant Cav2.1 is mitigated by a HSP90-dependent unfolded protein response (UPR) and that age-related breakdown of this response causes motor dysfunction and aberrant Purkinje cell spiking. Redundant pathways of the UPR mediate this resilience to ER stress. These studies elucidate a mechanism of resilience connecting aberrant proteostasis and calcium-dependent intrinsic membrane hyperexcitability to explain delayed disease onset more widely in age-dependent neurodegenerative disease.

Significance Statement

Advancing age is the single most important risk factor for neurodegenerative disease. Understanding how age intersects with genetic risk is therefore a critical challenge for neurodegenerative disease research. SCA6, a canonical late-onset degenerative cerebellar ataxia, results from a polyQ expansion in the voltage gated calcium channel, Cav2.1, encoded by CACNA1A . We define a mechanism of disease in SCA6 that is related to ER stress and unrelated to impaired calcium flux function of Cav2.1. Age-related decompensation of a HSP90-dependent unfolded protein response leads to disease onset. Mutant Cav2.1 misfolding as the basis for disease in SCA6 provides insight into a novel role for channelopathies to behave as proteinopathies and helps understand resilience to proteotoxicity more widely in adult-onset neurodegenerative disease.

GABRA1 frameshift variants impair GABAA receptor proteostasis

The gamma-aminobutyric acid type A receptor (GABAAR) is the most common inhibitory neurotransmitter-gated ion channel in the central nervous system. Pathogenic variants in genes encoding GABAAR subunits can cause receptor dysfunction and lead to genetic epilepsy. Frameshift variants in these genes can result in a premature termination codon, producing truncated receptor subunit variants. However, the pathogenic molecular mechanism as well as functional implications of these frameshift variants remains inadequately characterized. This study focused on four clinical frameshift variants of the α1 subunit of GABAAR (encoded by the GABRA1 gene): K401fs (c.1200del), S326fs (c.975del), V290fs (c.869_888del), and F272fs (c.813del). These variants result in the loss of one to three transmembrane helices, whereas wild type α1 has four transmembrane helices. Therefore, these variants serve as valuable models to evaluate membrane protein biogenesis and proteostasis deficiencies of GABAARs. In HEK293T cells, all four frameshift variants exhibit significantly reduced trafficking to the cell surface, resulting in essentially non-functional ion channels. However, the severity of proteostasis deficiency varied among these four frameshift variants, presumably due to their specific transmembrane domain deletions. The variant α1 subunits exhibited endoplasmic reticulum (ER) retention and activated the unfolded protein response (UPR) to varying extents. Our findings revealed that these frameshift variants of GABRA1 utilize overlapping yet distinct molecular mechanisms to impair proteostasis, providing insights into the pathogenesis of GABAAR-associated epilepsy.

The Role of Protein Disulfide Isomerase Inhibitors in Cancer Therapy

Protein disulfide isomerase (PDI) is a member of the mercaptan isomerase family, primarily located in the endoplasmic reticulum (ER). At least 21 PDI family members have been identified. PDI plays a key role in protein folding, correcting misfolded proteins, and catalyzing disulfide bond formation, rearrangement, and breaking. It also acts as a molecular chaperone. Dysregulation of PDI activity is thus linked to diseases such as cancer, infections, immune disorders, thrombosis, neurodegenerative diseases, and metabolic disorders. In particular, elevated intracellular PDI levels can enhance cancer cell proliferation, metastasis, and invasion, making it a potential cancer marker. Cancer cells require extensive protein synthesis, with disulfide bond formation by PDI being a critical producer. Thus, cancer cells have higher PDI levels than normal cells. Targeting PDI can induce ER stress and activate the Unfolded Protein Response (UPR) pathway, leading to cancer cell apoptosis. This review discusses the structure and function of PDI, PDI inhibitors in cancer therapy, and the limitations of current inhibitors, proposing especially future directions for developing new PDI inhibitors.

Dysregulation of Retinal and Photoreceptor Structural Integrity Genes in ATF6-/- Retinal Organoids

ATF6 is a key regulator of the unfolded protein response (UPR) pathway that maintains cellular homeostasis during ER stress. In people, loss of ATF6 function causes cone dysfunction, manifesting as achromatopsia (ACHM). Previously, we generated ACHM retinal organoids (ROs) from patient induced pluripotent stem cells (iPSCs) carrying mutant ATF6 variants and gene-edited ATF6-knockout (KO) human embryonic stem cells (hESCs). ACHM and ATF6-KO ROs both showed severe stunting of cone inner and outer segments. RNA-Seq analysis of ACHM 290-day-old ROs showed downregulated cone gene expression and dysregulated mitochondria and ER stress gene expression. Here, we analyzed RNA-Seq analysis of 203-day-old ATF6-KO ROs. In younger ROs, we found dysregulation of genes involved in retinal and photoreceptor structural integrity, including CRB1, EGFLAM, and VTN. In addition, we found dysregulation of ATF6 and UPR-regulated transcriptional signatures. Dysregulation of retinal and photoreceptor structural integrity genes may underlie the observed stunting of cone inner/outer segments in ATF6-achromatopsia patients.

Reticulophagy and viral infection

All viruses are obligate intracellular parasites that use host machinery to synthesize viral proteins. In infected eukaryotes, viral secreted and transmembrane proteins are synthesized at the endoplasmic reticulum (ER). Many viruses refashion ER membranes into bespoke factories where viral products accumulate while evading host pattern recognition receptors. ER processes are tightly regulated to maintain cellular homeostasis, so viruses must either conform to ER regulatory mechanisms or subvert them to ensure efficient viral replication. Reticulophagy is a catabolic process that directs lysosomal degradation of ER components. There is accumulating evidence that reticulophagy serves as a form of antiviral defense; we call this defense "xERophagy" to acknowledge its relationship to xenophagy, the catabolic degradation of microorganisms by macroautophagy/autophagy. In turn, viruses can subvert reticulophagy to suppress host antiviral responses and support efficient viral replication. Here, we review the evidence for functional interplay between viruses and the host reticulophagy machinery.Abbreviations: AMFR: autocrine motility factor receptor; ARF4: ADP-ribosylation factor 4; ARL6IP1: ADP-ribosylation factor-like 6 interacting protein 1; ATL3: atlastin GTPase 3; ATF4: activating transcription factor 4; ATF6: activating transcription factor 6; BPIFB3: BPI fold containing family B, member 3; CALCOCO1: calcium binding and coiled coil domain 1; CAMK2B: calcium/calmodulin-dependent protein kinase II, beta; CANX: calnexin; CDV: canine distemper virus; CCPG1: cell cycle progression 1; CDK5RAP3/C53: CDK5 regulatory subunit associated protein 3; CIR: cargo-interacting region; CoV: coronavirus; CSNK2/CK2: casein kinase 2; CVB3: coxsackievirus B3; DAPK1: death associated protein kinase 1; DENV: dengue virus; DMV: double-membrane vesicles; EBOV: Ebola virus; EBV: Epstein-Barr Virus; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; EMCV: encephalomyocarditis virus; EMV: extracellular microvesicle; ER: endoplasmic reticulum; ERAD: ER-associated degradation; ERN1/IRE1: endoplasmic reticulum to nucleus signalling 1; EV: extracellular vesicle; EV71: enterovirus 71; FIR: RB1CC1/FIP200-interacting region; FMDV: foot-and-mouth disease virus; HCMV: human cytomegalovirus; HCV: hepatitis C virus; HMGB1: high mobility group box 1; HSPA5/BiP: heat shock protein 5; IFN: interferon; IFNG/IFN-γ: interferon gamma; KSHV: Kaposi's sarcoma-associated herpesvirus; LIR: MAP1LC3/LC3-interacting region; LNP: lunapark, ER junction formation factor; MAP1LC3: microtubule-associated protein 1 light chain 3; MAP3K5/ASK1: mitogen-activated protein kinase kinase kinase 5; MAPK/JNK: mitogen-activated protein kinase; MeV: measles virus; MHV: murine hepatitis virus; NS: non-structural; PDIA3: protein disulfide isomerase associated 3; PRR: pattern recognition receptor; PRRSV: porcine reproductive and respiratory syndrome virus; RB1CC1/FIP200: RB1-inducible coiled-coil 1; RETREG1/FAM134B: reticulophagy regulator 1; RHD: reticulon homology domain; RTN3: reticulon 3; RTN3L: reticulon 3 long; sAIMs: shuffled Atg8-interacting motifs; SARS-CoV: severe acute respiratory syndrome coronavirus; SINV: Sindbis virus; STING1: stimulator of interferon response cGAMP interactor 1; SVV: Seneca Valley virus; SV40: simian virus 40; TEX264: testis expressed gene 264 ER-phagy receptor; TFEB: transcription factor EB; TRAF2: TNF receptor-associated factor 2; UIM: ubiquitin-interacting motif; UFM1: ubiquitin-fold modifier 1; UPR: unfolded protein response; VAPA: vesicle-associated membrane protein, associated protein A; VAPB: vesicle-associated membrane protein, associated protein B and C; VZV: varicella zoster virus; WNV: West Nile virus; XBP1: X-box binding protein 1; XBP1s: XBP1 spliced; xERophagy: xenophagy involving reticulophagy; ZIKV: Zika virus.

Tubulin-Binding Region Modulates Cholesterol-Triggered Aggregation of Tau Proteins

A hallmark of Alzheimer disease (AD) and tauopathies, severe neurodegenerative diseases, is the progressive aggregation of Tau, also known as microtubule-associated Tau protein. Full-length Tau1-441, also known as 2N4R, contains two N-terminal inserts that bind to tubulin. This facilitates the self-assembly of tubulin simultaneously enhancing stability of cell microtubules. Other Tau isoforms have one (1N4R) or zero (0N4R) N-terminal inserts, which makes 2N4R Tau more and 0N4R less effective in promoting microtubule self-assembly. A growing body of evidence indicates that lipids can alter the aggregation rate of Tau isoforms. However, the role of N-terminal inserts in Tau-lipid interactions remains unclear. In this study, we utilized a set of biophysical methods to determine the extent to which N-terminal inserts alter interactions of Tau isoforms with cholesterol, one of the most important lipids in plasma membranes. Our results showed that 2 N insert prevents amyloid-driven aggregation of Tau at the physiological concentration of cholesterol, while the absence of this N-terminal repeat (1N4R and 0N4R Tau) resulted in the self-assembly of Tau into toxic amyloid fibrils. We also found that the presence of cholesterol in the lipid bilayers caused a significant increase in the cytotoxicity of 1N4R and 0N4R Tau to neurons. This effect was not observed for 2N4R Tau fibrils formed in the presence of lipid membranes with low, physiological, and elevated concentrations of cholesterol. Using molecular assays, we found that Tau aggregates primarily exert cytotoxicity by damaging cell endosomes, endoplasmic reticulum, and mitochondria.

Roles of X-box binding protein 1 in liver pathogenesis

The prevalence of drug-induced liver injury (DILI) and viral liver infections presents significant challenges in modern healthcare and contributes to considerable morbidity and mortality worldwide. Concurrently, metabolic dysfunctionassociated steatotic liver disease (MASLD) has emerged as a major public health concern, reflecting the increasing rates of obesity and leading to more severe complications such as fibrosis and hepatocellular carcinoma. X-box binding protein 1 (XBP1) is a distinct transcription factor with a basic-region leucine zipper structure, whose activity is regulated by alternative splicing in response to disruptions in endoplasmic reticulum (ER) homeostasis and the unfolded protein response (UPR) activation. XBP1 interacts with a key signaling component of the highly conserved UPR and is critical in determining cell fate when responding to ER stress in liver diseases. This review aims to elucidate the emerging roles and molecular mechanisms of XBP1 in liver pathogenesis, focusing on its involvement in DILI, viral liver infections, MASLD, fibrosis/cirrhosis, and liver cancer. Understanding the multifaceted functions of XBP1 in these liver diseases offers insights into potential therapeutic strategies to restore ER homeostasis and mitigate liver damage.

Thioctic acid shield against lipopolysaccharide depression and endoplasmic reticulum stress: GR7M/Homer/ATF6 signaling

Aim: Endoplasmic reticulum stress triggers neuronal unfolded protein accumulation, contributing to the pathophysiology of depression psychiatric illnesses.Materials & methods: The brain-derived neurotrophic factor (BDNF), metabotropic glutamate receptor type 7 (GRM7), phosphoinisitol kinase-3 (PIK3), serine/threonine kinase 1 (AKT) and Homer1 may afford an important signaling pathways in LPS induced depression rat model. Herein, thioctic acid, Burdock and propolis therapeutic index on lipopolysaccharide (LPS)-induced depression was monitored. BDNF/PI3K/GR7M/ATF6/CHOP/XBP/AKT/Homer-1 signaling pathways also opened a novel avenue in the integration of synaptic neurotransmission.Results: The aforementioned treatments elevated GR7M/BDNF/GABA gene expression meanwhile decreased reactive oxygen species generation (Malondialdehyde/glutathione reductase/Total antioxidant capacity) and reduced the expression of ATF6/CHOP/PI3K/AKT/XBP/Homer-1 post LPS elevation.Conclusion: Thioctic acid, propolis and Burdock are prospective therapeutic agents via GRM7/BDNF/AKT/PI3K/ATF6/XBP/homer -1 signaling pathways in LPS-induced depression.

Visualizing ER-phagy and ER architecture in vivo

ER-phagy is an evolutionarily conserved mechanism crucial for maintaining cellular homeostasis. However, significant gaps persist in our understanding of how ER-phagy and the ER network vary across cell subtypes, tissues, and organs. Furthermore, the pathophysiological relevance of ER-phagy remains poorly elucidated. Addressing these questions requires developing quantifiable methods to visualize ER-phagy and ER architecture in vivo. We generated two transgenic mouse lines expressing an ER lumen-targeting tandem RFP-GFP (ER-TRG) tag, either constitutively or conditionally. This approach enables precise spatiotemporal measurements of ER-phagy and ER structure at single-cell resolution in vivo. Systemic analysis across diverse organs, tissues, and primary cultures derived from these ER-phagy reporter mice unveiled significant variations in basal ER-phagy, both in vivo and ex vivo. Furthermore, our investigation uncovered substantial remodeling of ER-phagy and the ER network in different tissues under stressed conditions such as starvation, oncogenic transformation, and tissue injury. In summary, both reporter models represent valuable resources with broad applications in fundamental research and translational studies.

Protein Glycosylation Patterns Shaped By the IRE1-XBP1s Arm of the Unfolded Protein Response

The unfolded protein response (UPR) is a sensing and signaling pathway that surveys the endoplasmic reticulum (ER) for protein folding challenges and responds whenever issues are detected. UPR activation leads to upregulation of secretory pathway chaperones and quality control factors, as well as reduces the nascent protein load on the ER, thereby restoring and maintaining proteostasis. This paradigm-defining view of the role of the UPR is accurate, but it elides additional key functions of the UPR in cell biology. In particular, recent work has revealed that the UPR can shape the structure and function of N- and O-glycans installed on ER client proteins. This crosstalk between the UPR's response to protein misfolding and the regulation of glycosylation remains insufficiently understood. Still, emerging evidence makes it clear that the UPR, and particularly the IRE1-XBP1s arm of the UPR, may be a central regulator of protein glycosylation with important biological consequences. In this review, we discuss the crosstalk between proteostasis, the UPR, and glycosylation, present progress towards understanding biological functions of this crosstalk, and examine potential roles in diseases such as cancer.

AKT kinases as therapeutic targets

AKT, or protein kinase B, is a central node of the PI3K signaling pathway that is pivotal for a range of normal cellular physiologies that also underlie several pathological conditions, including inflammatory and autoimmune diseases, overgrowth syndromes, and neoplastic transformation. These pathologies, notably cancer, arise if either the activity of AKT or its positive or negative upstream or downstream regulators or effectors goes unchecked, superimposed on by its intersection with a slew of other pathways. Targeting the PI3K/AKT pathway is, therefore, a prudent countermeasure. AKT inhibitors have been tested in many clinical trials, primarily in combination with other drugs. While some have recently garnered attention for their favorable profile, concern over resistance and off-target effects have continued to hinder their widespread adoption in the clinic, mandating a discussion on alternative modes of targeting. In this review, we discuss isoform-centric targeting that may be more effective and less toxic than traditional pan-AKT inhibitors and its significance for disease prevention and treatment, including immunotherapy. We also touch on the emerging mutant- or allele-selective covalent allosteric AKT inhibitors (CAAIs), as well as indirect, novel AKT-targeting approaches, and end with a briefing on the ongoing quest for more reliable biomarkers predicting sensitivity and response to AKT inhibitors, and their current state of affairs.

Astaxanthin inhibits apoptosis in a cell model of tauopathy by attenuating endoplasmic reticulum stress and unfolded protein response

The accumulation of misfolded proteins is a common pathological characteristic shared by many neurodegenerative diseases including Alzheimer's disease and Parkinson's disease. The disruption of proteostasis triggers endoplasmic reticulum (ER) stress, during which the unfolded protein response (UPR) is initiated by the activation of protein kinase R-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6). These three branches of UPR signals act in concert to reduce the levels of abnormal proteins and restore ER homeostasis. However, the overactivation of UPR impairs cell function and induces apoptosis, which has been implicated in neurodegeneration. Astaxanthin is a xanthophyll carotenoid which has been shown to have neuroprotective effects in both cell and animal models; however, its effects on ER stress and UPR induced by disrupted proteostasis remain unclear. In this study, the effects of astaxanthin on ER stress and cytotoxicity were investigated in N2a cells stably expressing the pro-aggregant tau repeat domain carrying FTDP-17 mutation ΔK280 (Tau4RDΔK280). The results demonstrated that astaxanthin significantly inhibited Tau4RDΔK280-induced loss of cell viability and apoptosis, attenuating Tau4RDΔK280-induced caspase-3 activation and decrease of Bcl-2. Further studies revealed that astaxanthin treatment alleviated Tau4RDΔK280-induced ER stress and suppressed the activation of PERK, IRE1 and ATF6 signaling pathways. These findings suggested that astaxanthin might inhibit Tau4RDΔK280-induced cytotoxicity by attenuating UPR and ER stress. In addition, astaxanthin treatment resulted in a great reduction in the production of intracellular reactive oxygen species and a significant decrease in calcium influx induced by Tau4RDΔK280, which also contributed to the protective effects of astaxanthin against Tau4RDΔK280-induced cytotoxicity.

Potential of natural drug modulation of endoplasmic reticulum stress in the treatment of myocardial injury

Myocardial injury (MI) is a common occurrence in clinical practice caused by various factors such as ischemia, hypoxia, infection, metabolic abnormalities, and inflammation. Such damages are characterized by a reduction in myocardial function and cardiomyocyte death that can result in dangerous outcomes such as cardiac failure and arrhythmias. An endoplasmic reticulum stress (ERS)-induced unfolded protein response (UPR) is triggered by several stressors, and its intricate signaling networks are instrumental in both cell survival and death. Cardiac damage frequently triggers ERS in response to different types of injuries and stress. High levels of ERS can exacerbate myocardial damage by inducing necrosis and apoptosis. To target ERS in MI prevention and treatment, current medical research is focused on identifying effective therapy approaches. Traditional Chinese medicine (TCM) is frequently used because of its vast range of applications and low risk of adverse effects. Various studies have demonstrated that active components of Chinese medicines, including polyphenols, saponins, and alkaloids, can reduce myocardial cell death, inflammation, and modify the ERS pathway, thus preventing and mitigating cardiac injury. Thus, this paper aims to provide a new direction and scientific basis for targeting ERS in MI prevention and treatment. We specifically summarize recent research progress on the regulation mechanism of ERS in MI by active ingredients of TCM.

Eicosanoids Signals in SARS-CoV-2 Infection: A Foe or Friend

SARS-CoV-2 mediated infection instigated a scary pandemic state since 2019. They created havoc comprising death, imbalanced social structures, and a wrecked global economy. During infection, the inflammation and associated cytokine storm generate a critical pathological situation in the human body, especially in the lungs. By the passage of time of infection, inflammatory disorders, and multiple organ damage happen which might lead to death, if not treated properly. Until now, many pathological parameters have been used to understand the progress of the severity of COVID-19 but with limited success. Bioactive lipid mediators have the potential of initiating and resolving inflammation in any disease. The connection between lipid storm and inflammatory states of SARS-CoV-2 infection has surfaced and got importance to understand and mitigate the pathological states of COVID-19. As the role of eicosanoids in COVID-19 infection is not well defined, available information regarding this issue has been accumulated to address the possible network of eicosanoids related to the initiation of inflammation, promotion of cytokine storm, and resolution of inflammation, and highlight possible strategies for treatment and drug discovery related to SARS-CoV-2 infection in this study. Understanding the involvement of eicosanoids in exploration of cellular events provoked by SARS-CoV-2 infection has been summarized as an important factor to deescalate any upcoming catastrophe imposed by the lethal variants of this micro-monster. Additionally, this study also recognized the eicosanoid based drug discovery, treatment, and strategies for managing the severity of SARS-COV-2 infection.

Sestrin2 serves as a scaffold protein to maintain cardiac energy and metabolic homeostasis during pathological stress

Cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality worldwide. Metabolic imbalances and pathological stress often contribute to increased mortality. Sestrin2 (Sesn2) is a stress-inducible protein crucial in maintaining cardiac energy and metabolic homeostasis under pathological conditions. Sesn2 is upregulated in response to various stressors, including oxidative stress, hypoxia, and energy depletion, and mediates multiple cellular pathways to enhance antioxidant defenses, promote autophagy, and inhibit inflammation. This review explores the mechanisms through which Sesn2 regulates these pathways, focusing on the AMPK-mTORC1, Sesn2-Nrf2, and HIF1α-Sesn2 pathways, among others. We can identify the potential therapeutic targets for treating CVDs and related metabolic disorders by comprehending these complex mechanisms. Sesn2's unique ability to respond thoroughly to metabolic challenges, oxidative stress, and inflammation makes it a promising prospect for enhancing cardiac health and resilience against pathological stress.

Landscape transcriptomic analysis of bovine follicular cells during key phases of ovarian follicular development

BACKGROUND

There are many gaps in our understanding of the mechanisms involved in ovarian follicular development in cattle, particularly regarding follicular deviation, acquisition of ovulatory capacity, and preovulatory changes. Molecular evaluations of ovarian follicular cells during follicular development in cattle, especially serial transcriptomic analyses across key growth phases, have not been reported. This study aims to address this gap by analyzing gene expression using RNA-seq in granulosa and antral cells recovered from ovarian follicular fluid during critical phases of ovarian follicular development in Holstein cows.

RESULTS

Integrated analysis of gene ontology (GO), gene set enrichment (GSEA), protein-protein interaction (PPI), and gene topology identified that differentially expressed genes (DEGs) in the largest ovarian follicles at deviation (Dev) were primarily involved in FSH-negative feedback, steroidogenesis, cell proliferation, apoptosis, and the prevention of early follicle rupture. In contrast, DEGs in the second largest follicles (DevF2) were mainly related to loss of cell viability, apoptosis, and immune cell invasion. In the dominant (PostDev) and preovulatory (PreOv) follicles, DEGs were associated with vascular changes and inflammatory responses.

CONCLUSIONS

The transcriptome of ovarian follicular fluid cells had a predominance of granulosa cells in the dominant follicle at deviation, with upregulation of genes involved in cell viability, steroidogenesis, and apoptosis prevention, whereas in the non-selected follicle there was upregulation of cell death-related transcripts. Immune cell transcripts increased significantly after deviation, particularly in preovulatory follicles, indicating strong intrafollicular chemotactic activity. We inferred that immune cell invasion occurred despite an intact basal lamina, contributing to follicular maturation.

Exploring Endocannabinoid System: Unveiling New Roles in Modulating ER Stress

The endoplasmic reticulum (ER) is the organelle mainly involved in maintaining cellular homeostasis and driving correct protein folding. ER-dependent defects or dysfunctions are associated with the genesis/progression of several pathological conditions, including cancer, inflammation, and neurodegenerative disorders, that are directly or indirectly correlated to a wide set of events collectively named under the term "ER stress". Despite the recent increase in interest concerning ER activity, further research studies are needed to highlight all the mechanisms responsible for ER failure. In this field, recent discoveries paved the way for the comprehension of the strong interaction between ER stress development and the endocannabinoid system. The activity of the endocannabinoid system is mediated by the activation of cannabinoid receptors (CB), G protein-coupled receptors that induce a decrease in cAMP levels, with downstream anti-inflammatory effects. CB activation drives, in most cases, the recovery of ER homeostasis through the regulation of ER stress hallmarks PERK, ATF6, and IRE1. In this review, we focus on the CB role in modulating ER stress, with particular attention to the cellular processes leading to UPR activation and oxidative stress response extinguishment, and to the mechanisms underlying natural cannabinoids' modulation of this complex cellular machine.

High-grade serous ovarian cancer development and anti-PD-1 resistance is driven by IRE1α activity in neutrophils

High-grade serious ovarian cancer (HGSOC) is an aggressive malignancy that remains refractory to current immunotherapies. While advanced stage disease has been extensively studied, the cellular and molecular mechanisms that promote early immune escape in HGSOC remain largely unexplored. Here, we report that primary HGSO tumors program neutrophils to inhibit T cell anti-tumor function by activating the endoplasmic reticulum (ER) stress sensor IRE1α. We found that intratumoral neutrophils exhibited overactivation of ER stress response markers compared with their counterparts at non-tumor sites. Selective deletion of IRE1α in neutrophils delayed primary ovarian tumor growth and extended the survival of mice with HGSOC by enabling early T cell-mediated tumor control. Notably, loss of IRE1α in neutrophils sensitized tumor-bearing mice to PD-1 blockade, inducing HGSOC regression and long-term survival in ~ 50% of the treated hosts. Hence, neutrophil-intrinsic IRE1α facilitates early adaptive immune escape in HGSOC and targeting this ER stress sensor might be used to unleash endogenous and immunotherapy-elicited immunity that controls metastatic disease.