Mechanisms, regulation and functions of the unfolded protein response

Sorafenib-associated translation reprogramming in hepatocellular carcinoma cells

Sorafenib (Sfb) is a multikinase inhibitor regularly used for the management of patients with advanced hepatocellular carcinoma (HCC) that has been shown to increase very modestly life expectancy. We have shown that Sfb inhibits protein synthesis at the level of initiation in cancer cells. However, the global snapshot of mRNA translation following Sorafenib-treatment has not been explored so far. In this study, we performed a genome-wide polysome profiling analysis in Sfb-treated HCC cells and demonstrated that, despite global translation repression, a set of different genes remain efficiently translated or are even translationally induced. We reveal that, in response to Sfb inhibition, translation is tuned, which strongly correlates with the presence of established mRNA cis-acting elements and the corresponding protein factors that recognize them, including DAP5 and ARE-binding proteins. At the level of biological processes, Sfb leads to the translational down-regulation of key cellular activities, such as those related to the mitochondrial metabolism and the collagen synthesis, and the translational up-regulation of pathways associated with the adaptation and survival of cells in response to the Sfb-induced stress. Our findings indicate that Sfb induces an adaptive reprogramming of translation and provides valuable information that can facilitate the analysis of other drugs for the development of novel combined treatment strategies based on Sfb therapy.

Single molecular profile of proteins sensing by nanopore technology

The characterization of biological macromolecules such as proteins and their interactions are crucial to understanding biological processes, disease diagnosis, and drug design. With the rapid development of proteomics, nanopore technology has emerged potentially as a single-molecule profile for huge amounts of peptides and proteins defined in the biological system, particularly for protein sequencing. This review focuses on recent advances in nanopore sensing of proteins and peptides, involving protein dynamic interactions, protein fingerprinting, and protein sequencing. These progresses will provide new perspectives to decipher the mechanisms of protein structure and function, and serve much more possible applications.

Developments in the connection between epithelial‑mesenchymal transition and endoplasmic reticulum stress (Review)

Endoplasmic reticulum stress (ERS) and epithelial‑mesenchymal transition (EMT) have important roles in fibrosis and tumour development. Moderate ERS activates cellular defence mechanisms in response to noxious stimuli; however, sustained or overly strong ERS induces apoptosis. In this disease process, EMT induces epithelial cells to acquire the ability to migrate and invade. Reportedly, ERS directly or indirectly regulates EMT processes through multiple mechanisms (such as key transcription factors, signalling pathways, ferroptosis, autophagy and oxidative stress), and both processes form a complex network of interactions. Given the critical roles of ERS and EMT in disease, targeted intervention of these two processes has emerged as a potential therapeutic strategy. In the present study, the molecular interaction mechanism of ERS and EMT was systematically explored, research progress in fibrotic and neoplastic diseases was reviewed and the potential application prospects of related targeted therapies were examined, which may provide new ideas for the development of drugs to reverse fibrosis and treat tumours.

Antimicrobial peptide WK-13-3D promotes apoptosis, autophagy, and ubiquitination in triple-negative breast cancer via binding immunoglobulin protein (BiP)

PURPOSE

To elucidate the inhibitory mechanism of antimicrobial peptide WK-13-3D on triple-negative breast cancer (TNBC) by targeting the binding immunoglobulin protein (BiP), a key endoplasmic reticulum (ER) chaperone regulating unfolded protein response and tumor survival.

METHODS

TNBC cell lines (MDA-MB-231 and MDA-MB-468) were treated with WK-13-3D to assess proliferation, migration, invasion, and apoptosis. Pull-down assays identified interacting proteins, and Western blotting (WB) analyzed alterations in BiP, PERK, eIF2α, p-eIF2α, Caspase3, Cleaved-Caspase3, Bax, LC3, P62, AKT, p-AKT, mTOR, and p-mTOR. Transmission electron microscopy examined intracellular structures, while qPCR measured BiP mRNA levels. The effects of WK-13-3D on BiP ubiquitination were explored via co-immunoprecipitation (Co-IP). Animal tumor models were used to confirm the inhibitory effects, with BiP and Ki67 (a nuclear proliferation marker indicating actively dividing tumor cells) expression analyzed by immunohistochemistry (IHC).

RESULTS

WK-13-3D inhibited TNBC cell proliferation, migration, and invasion, while promoting apoptosis. Pull-down experiments identified 268 interacting proteins, with BiP being the most frequent. Databases (TIMER and TCGA) showed high BiP expression in breast cancer, associated with poor prognosis. WB assays revealed that WK-13-3D activated ER stress-induced apoptosis and autophagy via BiP. Co-IP demonstrated that WK-13-3D mediated BiP ubiquitination at sites 352 and 547 through K6 and K29 chains. IHC analysis further confirmed decreased Ki67 levels in WK-13-3D-treated tumors, reflecting suppressed proliferative activity. Animal experiments confirmed tumor growth inhibition.

CONCLUSION

WK-13-3D promotes apoptosis, autophagy and Ubiquitination in TNBC by modulating BiP.

Endoplasmic reticulum stress regulates swainsonine-induced the autophagy in renal tubular epithelial cells through UPR signaling pathway

Swainsonine (SW), the primary toxic component of locoweed, induces toxic response in grazing livestock. The swainsonine induced toxicity is characterized by symptoms including head tremors, ataxia, and limb paralysis. The mechanisms of the toxicity remained to be investigated. The unfolded protein response (UPR) plays a key role in alleviating endoplasmic reticulum stress (ERS) by reducing protein synthesis and promoting the degradation of misfolded proteins. ERS is closely associated with both the UPR and autophagy activation. However, the involvement of the UPR signaling pathway in SW-induced ERS and autophagy remains unclear. In this study, we demonstrate that SW up-regulates the expression of GRP78, XBP1s, LC3-II/I, and ATG5 in both in vitro and in vivo models, suggesting activation of ERS, UPR, and autophagy. To investigate the molecular mechanisms by which the UPR regulates autophagy under ERS in primary rat renal tubular epithelial cells (RTECs), we observed that inhibiting PERK led to increased levels of p62. Inhibition of ATF6 significantly reduced the up-regulation of LC3-II/I, p62, and ATG5. Furthermore, inhibiting IRE1α significantly decreased the expression of LC3-II/I and p62. These findings suggest that PERK and ATF6 regulate autophagy mainly by modulating the expression of autophagy-related genes, while IRE1α likely regulates these genes through the IRE1α-XBP1 pathway. Additionally, autophagy is directly regulated through the IRE1α-JNK signaling pathway.

Design, synthesis and in vitro and in vivo biological evaluation of matrine derivatives as efficient anticancer agents with the characteristics of endoplasmic reticulum stress induction and apoptosis activation

Natural products have made significant contributions to the prevention and treatment of malignant tumors. However, natural products often suffer from low efficacy and potential toxicity. Therefore, modifying and optimizing lead compounds derived from natural products is a crucial strategy in drug development. In this study, we used matrine as an ideal lead compound and synthesized 27 matrine derivatives by incorporating indole structures with known antitumor activity. The antiproliferative effects of these derivatives were evaluated against human cancer cell lines (A549, HeLa, and Huh-7) and normal human liver cells (LO2). Compared to matrine, most of the derivatives exhibited superior antiproliferative activity. Notably, compound 9q showed significant antiproliferative activity against HeLa cells, with an IC50 value of 4.48 μM, demonstrating approximately 1500-fold greater potency than matrine (IC50 = 6756 μM). Further mechanistic studies revealed that compound 9q inhibited HeLa cell proliferation by modulating the expression of PI3K/AKT and Activating transcription factor 4 (ATF4) proteins. The upregulation of ATF4 promoted the expression of the key endoplasmic reticulum stress (ER stress) protein C/EBP homologous protein (CHOP). In the HeLa xenograft mouse model, compound 9q demonstrated significant anticancer efficacy. Therefore, compound 9q holds promise as a potential lead compound for the development of novel anticancer drugs.

Endoplasmic reticulum stress on glioblastoma: Tumor growth promotion and immunosuppression

Exogenous or endogenous factors such as hypoxia, nutritional deficiencies, acidic microenvironments and their own high metabolic demands usually lead to tumor endoplasmic reticulum dysfunction and trigger endoplasmic reticulum stress (ERS). ERS sensors intercept such stress signals, which subsequently initiate the unfolded protein response (UPR), enabling tumor cells to adapt robustly in the hostile environment. Many studies have found that the ERS response affects a variety of tumor-infiltrating immune cells and suppresses their anti-tumor responses through different mechanisms. Given that glioblastoma (GBM) are immunosuppressive "cold tumors" with a poor prognosis. This paper not only discusses the promotion of GBM growth by ERS response, but also reviews the mechanisms by which ERS response promotes an immunosuppressive microenvironment.

Insight into Ca2+- inositol 1,4,5-trisphosphate receptor 2 (IP3R2)-mediated unfolded protein response and apoptosis in scallop Patinopecten yessoensis under high temperature stress

Inositol 1,4,5-trisphosphate receptor 2 (IP3R2) is an essential Ca2+ release channel protein located in the endoplasmic reticulum (ER), and plays a significant role in responding to various environmental stimuli. In the present study, the function of IP3R2 from Yesso scallop Patinopecten yessoensis (PyIP3R2) in regulating the Ca2+-mediated unfolded protein response (UPR) and apoptosis after high temperature (25 °C) treatment was investigated. Three MIR domains, one RYDR_ITPR domain, one RIH_assoc domain and one Ion_trans domain were identified in PyIP3R2. Both D-myo-inositol-1,4,5-triphosphate (IP3, an activator of IP3R) and high temperature significantly upregulated the mRNA expression level of PyIP3R2 and genes related to apoptosis and the UPR, and also increased intracellular Ca2+ content (p < 0.05). Furthermore, the IP3R antagonist 2-aminoethyl diphenylborinate (2-APB) had the opposite effect, decreasing intracellular Ca2+ content and the mRNA expression level of PyIP3R2, glucose regulated protein 78 (PyGRP78) and PyCaspase-3 (p < 0.05). However, the apoptosis rate and Caspase-3 activity remained comparable to those in the injection control group. These findings indicate that PyIP3R2 mediates UPR and apoptosis in scallop haemocytes by regulating Ca2+content and distribution, and providing insight into the cellular responses of scallops to high temperature.

AA147 Alleviates Symptoms in a Mouse Model of Multiple Sclerosis by Reducing Oligodendrocyte Loss

Inflammation-induced oligodendrocyte death and CNS demyelination are key features of multiple sclerosis (MS). Inflammation-triggered endoplasmic reticulum (ER) stress and oxidative stress promote tissue damage in MS and in its preclinical animal model, experimental autoimmune encephalitis (EAE). Compound AA147 is a potent activator of the ATF6 signaling arm of the unfolded protein response (UPR) that can also induce antioxidant signaling through activation of the NRF2 pathway in neuronal cells. Previous work showed that AA147 protects multiple tissues against ischemia/reperfusion damage through ATF6 and/or NRF2 activation; however, its therapeutic potential in neuroinflammatory disorders remains unexplored. Here, we demonstrate that AA147 ameliorated the clinical symptoms of EAE and reduced ER stress, oligodendrocyte loss, and demyelination. Additionally, AA147 suppressed T cells in the CNS without altering the peripheral immune response. Importantly, AA147 significantly increased the expressions of Grp78, an ATF6 target gene, in oligodendrocytes, while enhancing levels of Grp78 as well as Ho-1, an NRF2 target gene, in microglia. In cultured oligodendrocytes, AA147 promoted nuclear translocation of ATF6, but not NRF2. Intriguingly, AA147 altered the microglia activation profile, possibly by triggering the NRF2 pathway. AA147 was not therapeutically beneficial during the acute EAE stage in mice lacking ATF6 in oligodendrocytes, indicating that protection primarily involves ATF6 activation in these cells. Overall, our results suggest AA147 as a potential therapeutic opportunity for MS by promoting oligodendrocyte survival and regulating microglia status through distinct mechanisms.

Pdia3 deficiency exacerbates intestinal injury by disrupting goblet and Paneth cell function during ischemia/reperfusion

Intestinal ischemia/reperfusion (I/R) injury is a severe medical condition associated with high mortality rates due to its disruption of intestinal homeostasis and impairment of mucosal defenses. The intestinal epithelium, particularly goblet and Paneth cells, plays a critical role in maintaining gut barrier integrity. Protein disulfide isomerase A3 (PDIA3) is involved in protein folding within intestinal epithelial cells (IECs) and has been linked to the stress response during I/R injury. This study aims to explore the role of PDIA3 in preserving intestinal integrity and immune function during I/R injury. Our study employed both human and mouse models to investigate PDIA3's expression and function. The correlation between PDIA3 expression and disease severity was analyzed using statistical tests, including Pearson's correlation coefficient. An intestinal I/R model was established in intestinal epithelium-specific conditional knockout mice lacking the Pdia3 gene. Single-cell RNA sequencing, immunohistochemistry, and transcriptomic analysis were used to assess PDIA3 expression in various intestinal cell types and to evaluate its role in epithelial differentiation and immune responses. PDIA3 was found to be highly expressed in healthy IECs, especially in goblet and Paneth cells. Its expression was reduced in patients with mesenteric artery ischemia and Pdia3-deficient mice, leading to severe intestinal damage, including impaired goblet and Paneth cell function, reduced antimicrobial peptide production, and altered gut microbiota. Treatment with recombinant defensin α1, an antimicrobial peptide secreted by Paneth cells, significantly alleviated the adverse effects of Pdia3 deficiency, restoring gut microbiota balance and reducing inflammation in the intestinal I/R injury mice. Taken together, our findings suggest that Pdia3 plays a vital role in maintaining intestinal barrier function and immune defense. Its deficiency exacerbates I/R-induced intestinal damage by impairing epithelial differentiation, mucus production, and antimicrobial peptide secretion. Targeting Pdia3 and associated pathways offers promising therapeutic strategies for mitigating I/R injury and restoring intestinal homeostasis.

Preliminary exploration of endoplasmic reticulum stress transmission in astrocytes and neurons, and its mediators

Unfolded protein response (UPR) signaling in cells stimulates UPR signaling in adjacent cells, facilitating the progression of disease (such as diabetes)by upregulating UPR target genes; however, whether this dissemination occurs between nerve cells, and its molecular basis, is currently unclear. In the present study, the supernatant of endoplasmic reticulum (ER) stress‑induced rat astrocytes was prepared and used to treat rat adrenal pheochromocytoma cell to simulate the propagation of ER stress between nerve cells. Reverse transcription‑quantitative PCR and western blotting were performed to detect the expression levels of mRNAs and protein levels associated with ER stress in cells. The results revealed that ER stress may propagate between rat nerve cells, ultimately leading to apoptosis. Analysis also revealed that the mediators of ER stress transmission were non‑vesicular, oxidative molecules with molecular weights >100 kDa. In conclusion, ER stress propagation may have a role in neuronal death following ER stress in central nervous system diseases, presenting potential novel therapeutic targets for these conditions.

IRE1α/TRAF2/NF-κB pathway promotes apoptosis via regulating inflammatory cytokines and aggravates brain injury after SAH

OBJECTIVES

To investigate the effect of IRE1α/TRAF2/NF-κB pathway on early brain injury.

METHODS

An endovascular puncture model of subarachnoid hemorrhage (SAH) was developed and SAH grading was performed. The following groups of experimental animals were randomly assigned: Blank group, Sham group, SAH+ DMSO group, SAH+STF-083010(IRE1α inhibitor) group, and SAH+BAY11-7082(NF-κB inhibitor) group. Neurological deficits were assessed in the animal models using a modified Garcia score. The expression of IRE1α, GRP78, TRAF2, NF-κB, and caspase3 was measured using western blot analysis. The concentrations of TNF-α, IL-1β and IL-6 were evaluated with ELISA kits. An analysis of neuronal apoptosis was performed using TUNEL staining.

RESULTS

The neurological deficits, expression of IRE1α/TRAF2/NF-κB axis and its related proteins, inflammatory cytokines and apoptosis were increased after SAH, whereas their expressions were suppressed since the inhibition of the IRE1α/TRAF2/NF-κB signal pathway. Moreover, correlation analysis showed that TNF-α, IL-1β and IL-6 were positively correlated with apoptosis.

CONCLUSIONS

The IRE1α/TRAF2/NF-κB signal pathway was activated and promoted apoptosis by promoting the expression of inflammatory cytokines after SAH.

Iron metabolism in rheumatic diseases

Iron is a crucial element for living organism in terms of oxygen transport, hematopoiesis, enzymatic activity, mitochondrial respiratory chain function and also immune system function. The human being has evolved a mechanism to regulate body iron. In some rheumatic diseases such as rheumatoid arthritis (RA), systemic lupus erythematous (SLE), systemic sclerosis (SSc), ankylosing spondylitis (AS), and gout, this balanced iron regulation is impaired. Altered iron homeostasis can contribute to disease progression through ROS production, fibrosis, inflammation, abnormal bone homeostasis, NETosis and cell senescence. In this review, we have focused on the iron metabolism in rheumatic disease and its role in disease progression.

Nimbolide Targeting SIRT1 Protects Against Acetaminophen-Induced Acute Liver Injury by Regulating Oxidative Stress and Endoplasmic Reticulum Stress

Acetaminophen (APAP) is a major cause of acute liver injury (ALI), and N-acetylcysteine is the only approved detoxification drug. Nimbolide (Nim), which is isolated from the neem tree (Azadirachta indica), possesses protective properties against multiple diseases, including pancreatitis, autoimmune hepatitis, arthritis, and diabetic cardiomyopathy. Here, we investigated the protective effect of nimbolide on APAP-induced ALI. Male C57BL/6J mice were used to establish an ALI model via APAP administration (500 mg/kg, i.p.). All the mice received nimbolide (20 mg/kg, i.p.) or a vehicle 2 h before APAP injection. Blood and liver samples were collected at the indicated times. As expected, Nim treatment alleviated APAP-induced liver injury and inflammation in the mice. Moreover, Nim inhibited APAP-induced apoptosis by regulating endoplasmic reticulum (ER) stress. We further revealed that Nim improved mitochondrial function and increased Sirtuin 1 (SIRT1) expression. However, the protective effects of Nim were partially blocked by SIRT1 knockdown via siRNA in vitro. Our study revealed that nimbolide alleviated APAP-induced ALI by inhibiting oxidative stress and ER stress via SIRT1 activation.

Allicin protects against pancreatic damage induced by zearalenone in rats by inhibiting endoplasmic reticulum stress

Zearalenone (ZEL) is a mycotoxin generated by Fusarium fungus. Ingestion of ZEL-contaminated foods by humans or animals can cause major health concerns. This work assessed the protective role of allicin in mitigating pancreatic damage caused by ZEL in rats. The experimental rats were allocated into control, Allicin (45 mg/kg /day), ZEL (20 mg/kg/ day), and Allicin-ZEL groups. The agents were administered orally for six weeks. ZEL enhanced the serum levels of amylase and lipase, oxidative stress parameters, and endoplasmic reticulum (ER) stress biomarkers, along with a marked decrease in the serum level of insulin. The disturbed architecture of pancreatic acini was demonstrated in the form of vacuolation of acini, degenerated acini with pyknotic nuclei, and infiltration around dilated congested blood vessels, in addition to the presence of dilated intralobular ducts with retained secretions. Also, the islet of Langerhans cells showed vacuolation and darkly stained nuclei. Immunohistochemically, a marked rise in the expression of heat shock protein 70 (HSP70) and P53 and a marked decline in insulin expression were demonstrated. Ultrastructurally, the pancreatic acinar cells and islets of Langerhans cells displayed shrunken irregular nuclei with dilated perinuclear cisternae and dilated rER. Interestingly, co-administration of allicin and ZEL greatly mitigated these detrimental effects. In summary, allicin inhibited pancreatic injury induced by ZEL by decreasing oxidative stress, ER stress, and apoptosis.

Unraveling the functional and molecular interplay between cellular senescence and the unfolded protein response

Senescence is a complex cellular state that can be considered as a stress response phenotype. A decade ago, we suggested the intricate connections between unfolded protein response (UPR) signaling and the development of the senescent phenotype. Over the past ten years, significant advances have been made in understanding the multifaceted role of the UPR in regulating cellular senescence, highlighting its contribution to biological processes such as oxidative stress and autophagy. In this updated review, we expand these interconnections with the benefit of new insights, and we suggest that targeting specific components of the UPR could provide novel therapeutic strategies to mitigate the deleterious effects of senescence, with significant implications for age-related pathologies and geroscience.

Potential mechanisms by which Jiawei Lianpu Yin inhibits Helicobacter pylori colonization and alleviates gastric mucosal inflammation and damage: Integrated transcriptomics, network pharmacology, and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Helicobacter pylori (H. pylori) infection is a primary cause of gastric mucosal damage and inflammation, and its persistent presence is recognized as a major risk factor for the development of gastric cancer. Despite available treatments, eradication of H. pylori remains a significant clinical challenge, highlighting the urgent need for new therapeutic agents that can disrupt bacterial colonization and facilitate its elimination. Jiawei Lianpu Yin (JWLPY), a traditional herbal formula composed of natural medicinal substances, has been used to treat gastric disorders related to H. pylori infection. However, the precise mechanisms underlying its therapeutic effects have not yet been fully elucidated.

AIM OF THE STUDY

The aim of this study was to investigate whether JWLPY can inhibit H. pylori colonization, alleviate gastric mucosal inflammation and damage, and to explore its underlying mechanisms of action.

MATERIALS AND METHODS

The effects of JWLPY on H. pylori and gastric mucosal injury were evaluated both in vitro and in vivo, using a rat model of H. pylori induced gastritis and an in vitro model of H. pylori induced damage in human gastric mucosal epithelial cells. The mechanisms of action of JWLPY were further investigated through transcriptomic analysis, network pharmacology, and bioinformatics approaches.

RESULTS

JWLPY inhibited the aggregation of inflammatory cells and preserved the integrity of the mucosal barrier, while reducing autophagy and apoptosis in gastric mucosal epithelial cells. Network pharmacology and transcriptomic analyses revealed that JWLPY promotes the assembly and synthesis of MUC5AC in the endoplasmic reticulum by activating the IRE1 XBP1 signaling pathway. This activation enhances protein folding and assembly processes within the endoplasmic reticulum, thereby inhibiting H. pylori colonization in the gastric mucosa.

CONCLUSION

This study is the first to demonstrate that JWLPY inhibits H. pylori colonization in the gastric mucosa, alleviates gastric inflammation and tissue damage, and holds potential as a therapeutic agent for the treatment of H. pylori related gastritis.

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.

TRx0237 induces apoptosis and enhances anti-PD-1 immunotherapeutic efficacy in anaplastic thyroid Cancer

Anaplastic thyroid cancer (ATC) is a highly malignant and lethal tumor with poor prognosis, but there is a lack of effective treatment strategies. In our study, we screened a drug library and identified that TRx0237, a tau protein inhibitor, showed inhibitory effect on ATC cells. Further research demonstrated that the inhibitory effect of TRx0237 was mainly through the induction of apoptosis via reactive oxygen species (ROS)-mediated endoplasmic reticulum stress pathway. Meanwhile, the pro-apoptosis effect and mechanism of TRx0237 on ATC were verified in xenograft and ATC patient-derived organoids. In addition, TRx0237 significantly upregulated the expression of PD-L1 in ATC, and synergistically enhanced the effect of anti-PD-1 therapy in xenograft and organoids model. Therefore, our study suggests that TRx0237 showed anticancer effects by inducing apoptosis and improving the efficacy of anti-PD-1 immunotherapy. TRx0237 is a potential agent for the treatment of ATC.

Mitochondrial unfolded protein response (UPRmt) as novel therapeutic targets for neurological disorders

Neurological disorders, including brain cancer, neurodegenerative diseases and ischemic/reperfusion injury, pose a significant threat to global human health. Due to the high metabolic demands of nerve cells, mitochondrial dysfunction is a critical feature of these disorders. The mitochondrial unfolded protein response (UPRmt) is an evolutionarily conserved mitochondrial response, which is critical for maintaining mitochondrial and energetic homeostasis under stress. Previous studies have found that UPRmt participates in diverse physiological processes especially metabolism and immunity. Currently, increasing evidence suggest that targeted regulation of UPRmt can also effectively delay the progression of neurological diseases and improve patients' prognosis. This review provides a comprehensive overview of UPRmt in the context of neurological diseases, with a particular emphasis on its regulatory functions. Additionally, we summarize the mechanistic insights into UPRmt in neurological disorders as investigated in preclinical studies, as well as its potential as a therapeutic target in the clinical management of neurological tumors. By highlighting the importance of UPRmt in the complex processes underlying neurological disorders, this review aims to bridge current knowledge gaps and inspire novel therapeutic strategies for these conditions.

P.1 and P.2 SARS-CoV-2 Brazilian variants activate the unfolded protein response with a time and pathway specificity

COVID-19 is a human respiratory syndrome caused by the infection of the SARS-CoV-2 virus that has a high rate of infection and mortality. Viruses modulate the host machinery by altering cellular mechanisms that favor their replication. One of the mechanisms that viruses exploit is the protein folding and processing of post-translational modifications that occur in the endoplasmic reticulum (ER). When ER function is impaired, there is an accumulation of misfolded proteins leading to endoplasmic reticulum stress (ER stress). To maintain homeostasis, cells trigger an adaptive signaling mechanism called the Unfolded Protein Response (UPR) which helps cells deal with stress, but under severe conditions, can activate the apoptotic cell death mechanism. This study elucidated an activation of a diversity of molecular mechanisms by Brazilian variants of SARS-CoV-2 by a time-resolved and large-scale characterization of SARS-CoV-2-infected cells proteomics and immunoblotting. Furthermore, it was shown that pharmacological UPR modulation could reduce viral release by counteracting the different viral activations of its cellular response. Analysis of human clinical specimens and disease outcomes focusing on ER stress reinforces the importance of UPR modulation as a host regulatory mechanism during viral infection and could point to novel therapeutic targets. SIGNIFICANCE: Since the emergence of SARS-CoV-2 and the consequent COVID-19 pandemic, the rapid emergence of variants of this new coronavirus has been a cause for concern since many of them have significantly higher rates of transmissibility and virulence, being called Variants of Concern (VOC). In this work, we studied the VOCs Gamma (P.1) and Zeta (P.2), also known as Brazilian variants. Constant evidence has reported that there are particularities related to each variant of SARS-CoV-2, with different rates of transmissibility, replication and modulation of host biological processes being observed, in addition to the mutations present in the variants. For this reason, this work focused on infections caused by the Brazilian variants of SARS-CoV-2 in different cell lines, in which we were able to observe that the infections caused by the variants induced endoplasmic reticulum stress in the infected cells and activated the UPR pathways, presenting specific modulations of each variant in this pathway. Furthermore, transcriptome analysis of patients revealed a correlation between ER-related genes and COVID-19 progression. Finally, we observed that the use of UPR modulators in host cells decreased viral release of all variants without affecting cell viability. The data presented in this work complement the observations of other studies that aim to understand the pathogenicity of SARS-CoV-2 VOCs and possible new therapeutic strategies, mainly targeting biological processes related to the endoplasmic reticulum.

Quiescent cell re-entry is limited by macroautophagy-induced lysosomal damage

To maintain tissue homeostasis, many cells reside in a quiescent state until prompted to divide. The reactivation of quiescent cells is perturbed with aging and may underlie declining tissue homeostasis and resiliency. The unfolded protein response regulators IRE-1 and XBP-1 are required for the reactivation of quiescent cells in developmentally L1-arrested C. elegans. Utilizing a forward genetic screen in C. elegans, we discovered that macroautophagy targets protein aggregates to lysosomes in quiescent cells, leading to lysosome damage. Genetic inhibition of macroautophagy and stimulation of lysosomes via the overexpression of HLH-30 (TFEB/TFE3) synergistically reduces lysosome damage. Damaged lysosomes require IRE-1/XBP-1 for their repair following prolonged L1 arrest. Protein aggregates are also targeted to lysosomes by macroautophagy in quiescent cultured mammalian cells and are associated with lysosome damage. Thus, lysosome damage is a hallmark of quiescent cells, and limiting lysosome damage by restraining macroautophagy can stimulate their reactivation.

ER stress and/or ER-phagy in drug resistance? Three coincidences are proof

Cancer is influenced by the tumor microenvironment (TME), which includes factors such as pH, hypoxia, immune cells, and blood vessels. These factors affect cancer cell growth and behavior. The tumor microenvironment triggers adaptive responses such as endoplasmic reticulum (ER) stress, unfolded protein response (UPR), and autophagy, posing a challenge to cancer treatment. The UPR aims to restore ER homeostasis by involving key regulators inositol-requiring enzyme-1(IRE1), PKR-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Additionally, ER-phagy, a selective form of autophagy, eliminates ER components under stress conditions. Understanding the interplay between hypoxia, ER stress, UPR, and autophagy in the tumor microenvironment is crucial for developing effective cancer therapies to overcome drug resistance. Targeting the components of the UPR and modulating ER-phagy could potentially improve the efficacy of existing cancer therapies. Future research should define the conditions under which ER stress responses and ER-phagy act as pro-survival versus pro-death mechanisms and develop precise methods to quantify ER-phagic flux in tumor cells.

Thioredoxin: a key factor in cold tumor formation and a promising biomarker for immunotherapy resistance in NSCLC

Immune checkpoint blockade (ICB) therapy has shown promising clinical efficacy in cancer treatment, but only a subset of patients experience significant therapeutic responses. Tumor cells respond to internal and external stresses, such as hypoxia and nutrient deprivation, by activating the unfolded protein response (UPR) in the tumor microenvironment. This response helps maintain homeostasis, promoting malignant progression, chemotherapy resistance, and immune escape. In this study, single-cell RNA sequencing (scRNA-seq) data from non-small cell lung cancer (NSCLC) patients treated with ICB revealed upregulation of thioredoxin (TXN) expression in the epithelial tissues of LUAD (lung adenocarcinoma) and LUSC (lung squamous cell carcinoma) patients with minimal pathological remission. High TXN expression was also associated with "cold tumors," characterized by a lack of T cells and low levels of chemokine receptors and immunomodulators. Experimental results showed that TXN was highly expressed in NSCLC tissues, and its knockdown significantly inhibited the proliferation and migration of A549 and SK-MES-1 cells. Furthermore, TXN knockdown enhanced T-cell-mediated cytotoxicity against these tumor cells, suggesting that TXN contributes to immune escape in NSCLC by promoting tumor cell proliferation and migration while inhibiting immune killing. Notably, TXN knockdown also upregulated CD40 expression, indicating that TXN may regulate immune escape in lung cancer through CD40 modulation.

Reprograming gene expression in 'hibernating' C. elegans involves the IRE-1/XBP-1 pathway

In nature, many animals respond to cold by entering hibernation, while in clinical settings, controlled cooling is used in transplantation and emergency medicine. However, the molecular mechanisms that enable cells to survive severe cold are still not fully understood. One key aspect of cold adaptation is the global downregulation of protein synthesis. Studying it in the nematode Caenorhabditis elegans, we find that the translation of most mRNAs continues in the cold, albeit at a slower rate, and propose that cold-specific gene expression is regulated primarily at the transcription level. Supporting this idea, we found that the transcription of certain cold-induced genes is linked to the activation of unfolded protein response (UPR) through the conserved IRE-1/XBP-1 signaling pathway. Our findings suggest that this pathway is triggered by cold-induced perturbations in proteins and lipids within the endoplasmic reticulum, and that its activation is beneficial for cold survival.

Pathogenic missense variants of CSNK2B associated with Poirier-Bienvenu neurodevelopmental disorder impact differently on CK2 holoenzyme formation

Poirier-Bienvenu neurodevelopmental syndrome is a neurodevelopmental disorder associated with de novo variants of the CSNK2B gene, characterized by intellectual disability, developmental delay, frequent seizures and more. While the majority of variants are nonsense variants leading to abortion of protein translation and no or truncated CK2β, many pathogenic missense variants also exist. We investigated the effect of four variants on CK2 holoenzyme formation and activity. We show that variants in the Zinc-finger region leads to reduced protein stability and altered subcellular localization. The instability is partly mediated by proteasomal and lysosomal degradation. We further show that homodimerization of these CK2β variants (p.Arg111Pro, p.Cys137Phe), localized within the Zinc-finger domain, is significantly reduced, while CK2α binding appears not affected. Other variants, p.Asp32Asn and p.Arg86Cys, did not affect stability or CK2β/α binding. For these mutants, the key to understanding the pathological mechanism may depend on external factors, such as altered protein-protein interaction. We conclude that Zinc-finger domain variants appear to destabilize the protein and affect holoenzyme formation, effectively reducing the pool of competent holoCK2. In the context of POBINDS, our findings suggest that Zinc-finger domain variants are likely to affect cells similarly to truncating and splicing variants with reduced translation of full-length CK2β.

Codonopsis pilosula polysaccharides alleviate neuronal apoptosis induced by endoplasmic reticulum stress-activated PERK-ATF4-CHOP signaling in APP/PS1 mice

BackgroundCodonopsis polysaccharides (CPPs) shows neuroprotective potential in Alzheimer's disease (AD) and may reduce neuronal apoptosis by modulating endoplasmic reticulum stress (ERS).ObjectiveTo investigate the protective mechanisms of CPPs against neuronal apoptosis in APP/PS1 mice, focusing on the ERS response and the PERK-ATF4-CHOP signaling pathway.MethodsAPP/PS1 mice were orally administered CPPs at different doses. Their learning and memory abilities were evaluated using the Morris water maze (MWM). The integrity of hippocampal neurons and senile plaque deposition were assessed using histopathology, immunohistochemistry, and immunofluorescence. The expression of amyloid-β (Aβ) plaques secretase protein, ERS markers, and apoptosis-related proteins was assessed using western blot analyses. The affinity of the PERK-ATF4-CHOP pathway and CPPs was analyzed and assessed using molecular docking.ResultsMWM testing revealed that CPPs improved the learning and memory abilities of APP/PS1 mice. Histopathological examination confirmed that CPPs reduced hippocampal neuronal apoptosis. Immunohistochemistry and immunofluorescence analysis showed that CPPs decreased Aβ protein expression and ERS. Western blot analysis further confirmed that CPPs reduced the expression of proteins related to Aβ synthesis; downregulated the expression of glucose-regulated protein 78 (GRP78), PERK, ATF4, CHOP, and Bcl-2 associated X protein (Bax), while upregulating the expression of B-cell lymphoma 2 (Bcl-2).ConclusionsThis study demonstrates that CPPs exert neuroprotective effects by targeting the PERK-ATF4-CHOP signaling pathway and alleviating ERS, suggesting a novel approach and potential therapeutic agent for AD treatment.

Ceramide mediates cell-to-cell ER stress transmission by modulating membrane fluidity

Under endoplasmic reticulum (ER) stress (ERS), cells initiate the unfolded protein response (UPR) to maintain ER homeostasis. Recent studies revealed ERS transmission between cells and tissues, by activating the cell-nonautonomous UPR in cells that do not experience ERS directly. Here, we report that ERS triggers a rapid release of ceramide independent of the UPR, but requiring the acid sphingomyelinase activity. Carried by lipoproteins, ceramide is delivered to receiving cells to induce the UPR and regulate cell functions at multiple aspects, including lipid accumulation, cell death, and cytokine production. Mechanistically, extracellular ceramide stimulates ceramide synthesis at the transcription level in receiving cells, leading to ceramide accumulation in the ER so as to reduce membrane fluidity to disrupt ER calcium homeostasis, thus activating the UPR. Sphingomyelin counterbalanced the effect of ceramide. UPR induction is the frontline response to protect cells from ceramide insult. Our study suggests ceramide-mediated ERS transmission as a universal cell-cell communication model regulating a wide range of physiological events.

Identification of Endoplasmic Reticulum Stress-Related Genes in Acute Myocardial Infarction: A Bioinformatics Approach with Experimental Validation

Acute myocardial infarction (AMI) continues to pose a substantial risk to human lives worldwide. Endoplasmic reticulum stress (ERS) is increasingly recognized as one of the potential mechanisms of myocardial injury following AMI. The primary goal of this study is to investigate the correlation between ERS and AMI through machine learning-based bioinformatics analysis, explore key genes, and conduct in vivo and in vitro experimental validation. We performed differential analysis and Weighted Gene Co-expression Network Analysis (WGCNA) on gene expression data from the GEO database (GSE62646). The intersection with ERS-related genes (ERSRGs) was taken to obtain AMI-ERS-related genes (MIEGs), and machine learning algorithms were further used to identify key genes (Hubs) from the MIEGs. The validation set GSE59867 was used to assess the expression levels and predictive capabilities of the Hubs for AMI. An AMI rat model was established to detect the mRNA and protein expression levels of the Hubs. The protein inhibitor of the key gene FURIN was used to treat H9C2 cells under oxygen-glucose deprivation (OGD) to explore the effects of FURIN on ERS and apoptosis. Bioinformatics analysis identified 27 MIEGs, and machine learning further determined 5 Hubs highly associated with AMI and ERS: RELA, FURIN, ERGIC3, TPP1, and BGLAP. The expression of these Hubs was significantly elevated in AMI patients within both the training and validation sets, and the area under the curve (AUC) indicated good diagnostic value. Our experiments confirmed that the mRNA levels of Furin and RelA were significantly elevated in AMI rats. Furin protein was increased in AMI rats and OGD H9C2. Furin inhibitor could alleviate OGD-induced ERS and apoptosis in H9C2. Our study demonstrates that Hubs play a pivotal role in myocardial infarction. Notably, Furin and its mediated ERS and apoptosis are significant in the pathogenesis of AMI, potentially serving as target for AMI diagnosis and treatment.

Gut microbiota modulate intestinal inflammation by endoplasmic reticulum stress-autophagy-cell death signaling axis

The intestinal tract, a complex organ responsible for nutrient absorption and digestion, relies heavily on a balanced gut microbiome to maintain its integrity. Disruptions to this delicate microbial ecosystem can lead to intestinal inflammation, a hallmark of inflammatory bowel disease (IBD). While the role of the gut microbiome in IBD is increasingly recognized, the underlying mechanisms, particularly those involving endoplasmic reticulum (ER) stress, autophagy, and cell death, remain incompletely understood. ER stress, a cellular response to various stressors, can trigger inflammation and cell death. Autophagy, a cellular degradation process, can either alleviate or exacerbate ER stress-induced inflammation, depending on the specific context. The gut microbiome can influence both ER stress and autophagy pathways, further complicating the interplay between these processes. This review delves into the intricate relationship between ER stress, autophagy, and the gut microbiome in the context of intestinal inflammation. By exploring the molecular mechanisms underlying these interactions, we aim to provide a comprehensive theoretical framework for developing novel therapeutic strategies for IBD. A deeper understanding of the ER stress-autophagy axis, the gut microbial-ER stress axis, and the gut microbial-autophagy axis may pave the way for targeted interventions to restore intestinal health and mitigate the impact of IBD.

Molecular mechanisms of endoplasmic reticulum stress-mediated acute kidney injury in juvenile rats and the protective role of mesencephalic astrocyte-derived neurotrophic factor

OBJECTIVES

This study examined the role of endoplasmic reticulum stress in pediatric acute kidney injury and the therapeutic effect of midbrain astrocyte-derived neurotrophic factor.

METHODS

Two-week-old Sprague-Dawley rats were divided into: Sham, ischemia-reperfusion injury-induced acute kidney injury (AKI), mesencephalic astrocyte-derived neurotrophic factor (MANF)-treated, tauroursodeoxycholic acid (TUDCA)-treated. Analyses were conducted 24 h post-treatment. Serum creatinine, cystatin C, Albumin, MANF levels were measured, cytokine concentrations in serum and renal tissues were determined using a Luminex assay. Histopathology was assessed via light and electron microscopy. Western blotting and RT-qPCR analyzed markers for oxidative stress, apoptosis, endoplasmic reticulum (ER) stress, and autophagy. HK-2 cells underwent hypoxia/reoxygenation (H/R) to simulate AKI and were treated with MANF or TUDCA.

RESULTS

AKI rats had increased serum creatinine, cystatin C, and inflammatory cytokines, along with significant renal damage, and showed loose and swollen ER structures, reduced cell proliferation, and elevated levels of IRE1, PERK, ATF6, CHOP, LC3-II/I, KIM-1, TLR4, JNK, and NF-κB. MANF treatment reduced these biomarkers and protein levels, improved ER structure and cell proliferation, alleviated oxidative stress, apoptosis, ER stress, and inhibited JNK/TLR4/NF-κB signaling. In HK-2 cells, MANF reduced ER stress and inflammation post-H/R exposure.

CONCLUSIONS

MANF treatment alleviates ER stress, oxidative stress, apoptosis, and inflammation in pediatric AKI, improving renal function and morphology.

Pooled tagging and hydrophobic targeting of endogenous proteins for unbiased mapping of unfolded protein responses

To achieve system-level insights into proteome organization, regulation, and function, we developed an approach to generate complex cell pools with endogenously tagged proteins amenable to high-throughput visualization and perturbation. Pooled imaging coupled to in situ barcode sequencing identified the subcellular localization of each HaloTag-tagged protein, and subsequent ligand-induced misfolding of the library followed by single-cell RNA sequencing revealed responses to spatially restricted protein misfolding. These datasets characterized protein quality control responses in previously uninterrogated cellular compartments, and cross-compartment analyses revealed mutually exclusive rather than collaborative responses, whereby the heat shock response (HSR) is induced in some compartments and repressed in others where autophagy genes are induced. We further assign protein quality control functions to previously uncharacterized genes based on shared transcriptional responses to protein misfolding across cellular compartments. Altogether, we present an efficient method for large-scale studies of proteome dynamics, function, and homeostasis.

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.

Characterization and Inhibition of the Chaperone Function of Plasmodium falciparum Glucose-Regulated Protein 94 kDa (Pf Grp94)

Plasmodium falciparum expresses four heat shock protein 90 (Hsp90) members. Among these, one, glucose-regulated protein 94 (PfGrp94), is localized in the endoplasmic reticulum (ER). Both the cytosolic and ER-based Hsp90s are essential for parasite survival under all growth conditions. The cytosolic version has been extensively studied and has been targeted in several efforts through the repurposing of anticancer therapeutics as antimalarial drugs. However, PfGrp94 has not been fully characterized and some of its functions related to the ER stress response are not fully understood. Structural analysis of the recombinant full-length PfGrp94 protein showed a predominantly α-helical secondary structure and its thermal resilience was modulated by 5'-N-ethyl-carboxamide-adenosine (NECA) and nucleotides ATP/ADP. PfGrp94 exhibits ATPase activity and suppressed heat-induced aggregation of a model substrate, malate dehydrogenase, in a nucleotide-dependent manner. However, these PfGrp94 chaperone functions were abrogated by NECA. Molecular docking and molecular dynamics (MD) simulations showed that NECA interacted with unique residues on PfGrp94, which could be potentially exploited for selective drug design. Finally, using parasites maintained at the red blood stage, NECA exhibited moderate antiplasmodial activity (IC50 of 4.3, 7.4, and 10.0 μM) against three different P. falciparum strains. Findings from this study provide the first direct evidence for the correlation between in silico, biochemical, and in vitro data toward utilizing the ER-based chaperone, PfGrp94, as a drug target against the malaria parasites.

The structural and functional dynamics of BiP and Grp94: opportunities for therapeutic discovery

Binding immunoglobulin protein (BiP) and glucose-regulated protein 94 (Grp94) are endoplasmic reticulum (ER)-localized molecular chaperones that ensure proper protein folding and maintain protein homeostasis. However, overexpression of these chaperones during ER stress can contribute to disease progression in numerous pathologies. Although these chaperones represent promising therapeutic targets, their inhibition has been challenged by gaps in understanding of targetable chaperone features and their complex biology. To overcome these challenges, a new assay has been developed to selectively target BiP, and compounds that exploit subtle conformational changes of Grp94 have been designed. This review summarizes recent advances in elucidating structural and functional dynamics of BiP and Grp94. We explore leveraging this information to develop novel therapeutic interventions. Finally, given the recent advances in computing, we discuss how machine learning methods can be used to accelerate drug discovery efforts.

Protective effect of curcumin against endoplasmic reticulum stress and lipid metabolism disorders in AFB1-intoxicated duck liver

Aflatoxin B1 (AFB1) is a stable and highly toxic toxin that causes multi-organ toxicity with sustained ingestion, most typically in the duck liver. Previous research has shown that AFB1 can bring about endoplasmic reticulum stress (ERS) in animals, and ERS is strongly associated with lipid metabolism. However, the relationship between AFB1-induced duck liver toxicity and ERS and lipid metabolism is currently unclear. Great attention has been paid to the prevention and treatment of AFB1 because of its great harm. Curcumin, a natural polyphenol, is notable for its powerful anti-inflammatory and antioxidant properties. Studies have shown curcumin to be protective against afb1-induced avian multi-organ toxicity. However, the effects of curcumin on the liver of ducks exposed to AFB1 are largely unknown. In the present study, we aimed to investigate whether AFB1 exposure induces ERS and lipid metabolism disorders in duck liver, while exploring the positive role of curcumin in it. One-day-old ducks (n = 80) were randomly divided in four groups: control group, AFB1 group (0.1 mg / kg.bw AFB1), Cur group (400 mg/kg curcumin), and AFB1 + Cur group (0.1 mg/kg.bw AFB1 + 400 mg/kg curcumin), and blood and liver were collected for the study after 21 days of continuous administration. Our research has found that AFB1 exposure significantly increases the levels of liver function indicators ALP, AST, and ALT in ducks' serum (P < 0.05). Duck liver undergoes fatty degeneration under the influence of AFB1. Under the effect of curcumin, AFB1-induced structural damage in duck liver was somewhat controlled. Further experimental results showed that AFB1 treatment significantly increased the expression of glucose-regulated protein 78 (P < 0.001), and activated the endoplasmic reticulum stress pathway. Meanwhile, AFB1 inhibited the LKB1-AMPK signaling pathway and disrupted lipid metabolic homeostasis. And curcumin treatment effectively reversed these changes. Overall, our results suggest that curcumin attenuates AFB1-induced hepatotoxicity in ducks by inhibiting ERS and lipid metabolism disorders.

Lithium carbonate exposure disrupts neurodevelopment by perturbing primary cilia and ER homeostasis

Lithium, which is widely used in medicine and batteries, has become increasingly prevalent in the environment, raising concerns about its impact on human health. Lithium carbonate (Li2CO3) is a common treatment and relapse prevention method for bipolar disorder. It can freely cross the placental barrier; however, lithium treatment is accompanied by side effects, particularly in women of reproductive age. Among these, neural tube defects (NTDs) have the most severe impact on nervous system development; however, their underlying mechanisms remain unclear. This study explored the potential mechanisms by which Li2CO3 exposure contributes to NTDs. Pregnant mice were intraperitoneally injected with Li2CO3 (360 mg/kg), which mimicked high-exposure scenarios such as an unintended pregnancy during lithium therapy or exposure to industrial contamination. Embryos were assessed for morphological changes, primary cilia length, and endoplasmic reticulum (ER) homeostasis using histological analysis, scanning electron microscopy, PCR array analysis, immunofluorescence, and quantitative real-time PCR. Network and bioinformatics analyses were used to identify primary molecular targets and pathways. We also evaluated the effects of inositol supplementation on cilia during Li2CO3 exposure. The results revealed that treatment with Li2CO3 at 360 mg/kg induced exencephaly in some embryos, reduced primary cilia length, and dysregulated cilia-associated gene expression in the neural tube. PCR Array, network metabolism, and immunofluorescence analyses revealed that HSP90AB1, a critical regulator of ER homeostasis, was upregulated in Li2CO3-treated embryos with NTDs. Li2CO3 exposure disturbed ER homeostasis in the developing brain. Interestingly, inositol supplementation partially rescued ciliogenesis impairment in lithium-treated NIH3T3 cells. Li2CO3 exposure disrupted primary ciliary development and ER homeostasis in the embryonic neural tube. Maintaining adequate maternal inositol levels during Li2CO3 exposure before and during pregnancy prevents NTDs. These findings help in better understanding and reassessing the risks associated with lithium, especially in terms of maternal and fetal health.

CD40 Induces Unfolded Protein Response, Upregulation of VEGF, and Vascular Leakage in Diabetic Retinopathy

The unfolded protein response (UPR) drives events that promote diabetic retinopathy, including vascular endothelial growth factor (VEGF) upregulation in Müller cells. How UPR is activated in vivo in the diabetic retina is not well understood. CD40 is required for development of diabetic retinopathy, but whether CD40 mediates activation of UPR sensors is unknown. CD40 ligation in Müller cells caused phospholipase Cγ1 (PLCγ1)-dependent activation of UPR sensors (PERK, IRE1α, and ATF6α) and VEGF production dependent on PLCγ1 and UPR sensors. Diabetic Cd40-/- mice did not exhibit UPR activation or VEGF upregulation in the retina. These responses were restored in diabetic Cd40-/- mice rescued to express wild-type CD40 in Müller cells but not in mice rescued to express a CD40 mutation unable to recruit TRAF2/3. Intravitreal administration of a cell-permeable CD40-TRAF2/3-disrupting peptide reduced UPR activation, VEGF upregulation, and vascular leakage in diabetic mice. CD40 and TRAF2 in Müller cells from patients with diabetic retinopathy colocalized with activated UPR sensors and VEGF. Our study indicates that CD40 (via TRAF2/3 signaling) is an inducer of UPR activation that triggers VEGF production in Müller cells. This work uncovered inhibition of CD40-TRAF2/3 signaling as a potential approach to impair UPR activation, VEGF upregulation, and vascular leakage in diabetic retinopathy.

ARTICLE HIGHLIGHTS

Endoplasmic reticulum stress as a driver and therapeutic target for kidney disease

The endoplasmic reticulum (ER) has crucial roles in metabolically active cells, including protein translation, protein folding and quality control, lipid biosynthesis, and calcium homeostasis. Adverse metabolic conditions or pathogenic genetic variants that cause misfolding and accumulation of proteins within the ER of kidney cells initiate an injurious process known as ER stress that contributes to kidney disease and its cardiovascular complications. Initiation of ER stress activates the unfolded protein response (UPR), a cellular defence mechanism that functions to restore ER homeostasis. However, severe or chronic ER stress rewires the UPR to activate deleterious pathways that exacerbate inflammation, apoptosis and fibrosis, resulting in kidney injury. This insidious crosstalk between ER stress, UPR activation, oxidative stress and inflammation forms a vicious cycle that drives kidney disease and vascular damage. Furthermore, genetic variants that disrupt protein-folding mechanisms trigger ER stress, as evidenced in autosomal-dominant tubulointerstitial kidney disease and Fabry disease. Emerging therapeutic strategies that enhance protein-folding capacity and reduce the burden of ER stress have shown promising results in kidney diseases. Thus, integrating knowledge of how genetic variants cause protein misfolding and ER stress into clinical practice will enhance treatment strategies and potentially improve outcomes for various kidney diseases and their vascular complications.

Targeting polyunsaturated fatty acids desaturase FADS1 inhibits renal cancer growth via ATF3-mediated ER stress response

OBJECTIVE

Fatty Acid Desaturase 1 (FADS1) is a rate-limiting enzyme controlling the bioproduction of long-chain polyunsaturated fatty acids (PUFAs). Increasing studies suggest that FADS1 is a potential cancer target. Our previous research has demonstrated the significant role of FADS1 in cancer biology and patient survival, especially in kidney cancers. We aim to explore the underlying mechanism in this study.

METHOD AND RESULTS

We found that pharmacological inhibition or knockdown of the expression of FADS1 significantly reduced the intracellular conversion of long-chain PUFAs, effectively inhibits renal cancer cell proliferation, and induces cell cycle arrest. The stable knockdown of FADS1 also significantly inhibits tumor formation in vivo. Mechanistically, we showed that while FADS1 inhibition induces endoplasmic reticulum (ER) stress, FADS1 expression is augmented by ER-stress inducer, suggesting a necessary role of PUFA production in response to ER stress. FADS1-inhibition sensitized cellular response to ER stress inducers, leading to cell apoptosis. Also, FADS1 inhibition-induced ER stress leads to activation of the PERK/eIF2α/ATF4/ATF3 pathway. Inhibiting PERK or knockdown of ATF3 rescued FADS1 inhibition-induced ER stress and cell growth suppression, while ATF3-overexpression aggravates the FADS1 inhibition-induced cell growth suppression and leads to cell death. Metabolomic analysis revealed that FADS1 inhibition results in decreased level of UPD-N-Acetylglucosamine, a critical mediator of the unfolded protein response, as well as impaired biosynthesis of nucleotides, possibly accounting for the cell cycle arrest.

CONCLUSION

Our findings suggest that PUFA desaturation is crucial for rescuing cancer cells from persistent ER stress, supporting FADS1 as a new therapeutic target.

Proteostasis regulation of GABAA receptors in neuronal function and disease

The γ-aminobutyric acid type A receptors (GABAARs) are ligand-gated anion channels that mediate fast inhibitory neurotransmission in the mammalian central nervous system. GABAARs form heteropentameric assemblies comprising two α1, two β2, and one γ2 subunits as the most common subtype in mammalian brains. Proteostasis regulation of GABAARs involves subunit folding within the endoplasmic reticulum, assembling into heteropentamers, receptor trafficking to the cell surface, and degradation of terminally misfolded subunits. As GABAARs are surface proteins, their trafficking to the plasma membrane is critical for proper receptor function. Thus, variants in the genes encoding GABAARs that disrupt proteostasis result in various neurodevelopmental disorders, ranging from intellectual disability to idiopathic generalized epilepsy. This review summarizes recent progress about how the proteostasis network regulates protein folding, assembly, degradation, trafficking, and synaptic clustering of GABAARs. Additionally, emerging pharmacological approaches that restore proteostasis of pathogenic GABAAR variants are presented, providing a promising strategy to treat related neurological diseases.

Pre-clinical model of dysregulated FicD AMPylation causes diabetes by disrupting pancreatic endocrine homeostasis

The bi-functional enzyme FicD catalyzes AMPylation and deAMPylation of the endoplasmic reticulum chaperone BiP to modulate ER homeostasis and the unfolded protein response (UPR). Human hFicD with an arginine-to-serine mutation disrupts FicD deAMPylation activity resulting in severe neonatal diabetes. We generated the mFicDR371S mutation in mice to create a pre-clinical murine model for neonatal diabetes. We observed elevated BiP AMPylation levels across multiple tissues and signature markers for diabetes including glucose intolerance and reduced serum insulin levels. While the pancreas of mFicDR371S mice appeared normal at birth, adult mFicDR371S mice displayed disturbed pancreatic islet organization that progressed with age. mFicDR371S mice provide a preclinical mouse model for the study of UPR associated diabetes and demonstrate the essentiality of FicD for tissue resilience.

Redox regulation of lung endothelial PERK, unfolded protein response (UPR) and proliferation via NOX1: Targeted inhibition as a potential therapy for PAH

AIMS

Reactive oxygen species (ROS) play an important role in the pathogenesis of pulmonary arterial hypertension (PAH) and NADPH oxidases (NOXs) as sources of ROS are implicated in the development of the disease. We previously showed that NOX isozyme 1 (NOX1)-derived ROS contributes to pulmonary vascular endothelial cell (EC) proliferation in response to PAH triggers in vitro. However, whether and how NOX1 is involved in PAH in vivo have not been explored nor has NOX1 been examined as a viable and effective therapeutic disease target.

METHODS AND RESULTS

Herein, infusion of mice exposed to Sugen/hypoxia (10 % O2) with a specific NOX1 inhibitor, NOXA1ds, delivered via osmotic minipumps (i.p.), significantly suppressed pathological changes in hemodynamic parameters characteristic of PAH. Furthermore, lungs of human patients with idiopathic PAH (iPAH) and exploratory RNA-seq analysis of hypoxic human pulmonary ECs, in which NOX1 was suppressed, were probed. The findings showed a clear indication of NOX1 in the promotion of both protein disulfide isomerase (PDI) and the unfolded protein response (UPR; in particular, the PERK arm of the pathway including eIF2α and ATF4) leading to proliferation. In aggregate, these results are consistent with a causal role for NOX1 in the development of mouse and human PAH and reveal a novel and mechanistic pathway by which NOX1 activates the UPR response during EC proliferation.

CONCLUSION

NOX1 promotes phenotypic changes in ECs that are pivotal to proliferation and PAH through activation of the UPR. Taken together, our results are consistent with selective inhibition of NOX1 as a novel modality for attenuating PAH.

Getting to know adenosine deaminase 2 deficiency inside and out

Ten years after the description of the first cohorts of patients with adenosine deaminase (ADA2) deficiency (DADA2), the pathomechanisms underlying the disease on a cellular level remain poorly understood. With the establishment of the lysosomal localization of the ADA2 protein and its involvement in nucleic acid sensing, the pathophysiologic focus has shifted to the inside of the cell. At the same time, extracellular (serum) ADA2 enzyme activity continues to be the diagnostic reference standard in patients with suspected DADA2. The diverse clinical phenotype and weak genotype-phenotype correlations further complicate the identification of shared cellular mechanisms that cause inflammation, immunodeficiency, and bone marrow failure in the absence of functional ADA2. This review inspects the characteristics of the ADA2 protein and its proposed function. The latter is discussed in the context of possible mechanisms driving the clinical phenotype in patients lacking functional ADA2. We discuss established processes and introduce unexplored pathways in the pathogenesis of DADA2.

Pathophysiological underpinnings of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is emerging as the leading cause of chronic liver disease worldwide, reflecting the global epidemics of obesity, metabolic syndrome, and type 2 diabetes. Beyond its strong association with excess adiposity, MASLD encompasses a heterogeneous population that includes individuals with normal body weight ("lean MASLD") highlighting the complexity of its pathogenesis. This disease results from a complex interplay between genetic susceptibility, epigenetic modifications, and environmental factors, which converge to disrupt metabolic homeostasis. Adipose tissue dysfunction and insulin resistance trigger an overflow of lipids to the liver, leading to mitochondrial dysfunction, oxidative stress, and hepatocellular injury. These processes promote hepatic inflammation and fibrogenesis, driven by cross talk among hepatocytes, immune cells, and hepatic stellate cells, with key contributions from gut-liver axis perturbations. Recent advances have unraveled pivotal molecular pathways, such as transforming growth factor-β signaling, Notch-induced osteopontin, and sphingosine kinase 1-mediated responses, that orchestrate fibrogenic activation. Understanding these interconnected mechanisms is crucial for developing targeted therapies. This review integrates current knowledge on the pathophysiology of MASLD, emphasizing emerging concepts such as lean metabolic dysfunction-associated steatohepatitis (MASH), epigenetic alterations, hepatic extracellular vesicles, and the relevance of extrahepatic signals. It also discusses novel therapeutic strategies under investigation, aiming to provide a comprehensive and structured overview of the evolving MASLD landscape for both basic scientists and clinicians.

Endoplasmic reticulum stress disrupts signaling via altered processing of transmembrane receptors

Cell communication systems based on polypeptide ligands use transmembrane receptors to transmit signals across the plasma membrane. In their biogenesis, receptors depend on the endoplasmic reticulum (ER)-Golgi system for folding, maturation, transport and localization to the cell surface. ER stress, caused by protein overproduction and misfolding, is a well-known pathology in neurodegeneration, cancer and numerous other diseases. How ER stress affects cell communication via transmembrane receptors is largely unknown. In disease models of multiple myeloma, chronic lymphocytic leukemia and osteogenesis imperfecta, we show that ER stress leads to loss of the mature transmembrane receptors FGFR3, ROR1, FGFR1, LRP6, FZD5 and PTH1R at the cell surface, resulting in impaired downstream signaling. This is caused by downregulation of receptor production and increased intracellular retention of immature receptor forms. Reduction of ER stress by treatment of cells with the chemical chaperone tauroursodeoxycholic acid or by expression of the chaperone protein BiP resulted in restoration of receptor maturation and signaling. We show a previously unappreciated pathological effect of ER stress; impaired cellular communication due to altered receptor processing. Our findings have implications for disease mechanisms related to ER stress and are particularly important when receptor-based pharmacological approaches are used for treatment.

Fullerenols hijack lysosomes to disrupt inter-organellar crosstalk and block autophagy pre-activated by mTOR inhibitors for cancer cell PANoptosis

Subcellular inter-organellar crosstalk among lysosome, endoplasmic reticulum (ER), and mitochondrion is crucial for cancer cell survival and is a promising target in cancer treatment; however, efficiently disrupting these interactive networks is challenging. Herein, a communication interception strategy is presented, which specifically disrupts inter-organellar crosstalk by lysosomal contents leakage along with their trajectory and pre-activates autophagic flux to augment the lysosome-associated autophagy blocking for preventing the self-repair of this subcellular disorder. Briefly, fullerenols containing multiple hydroxyl groups (MF) tear the lysosomal phospholipid membrane through direct interaction, which causes lysosomal contents (calcium ions and cathepsins) to leak into the cytoplasm, subsequently leading to endoplasmic reticulum stress and mitochondrial dysfunction with redox imbalance and metabolic reprogramming. mTOR inhibitors activate and amplify autophagy, then impaired lysosomes prevent their fusion with autophagosome, and thus autophagy is paralyzed along with autolysosome accumulation. Consequently, the cellular homeostasis is compromised by destroyed inter-organellar networks without self-repair by autophagy, thereby triggering PANoptotic processes and leading to a remarkable anti-tumor therapeutic efficacy in vitro and in vivo. This strategy demonstrates the selective cytotoxicity of non-toxic nanomaterials that interfere with subcellular inter-organellar crosstalk, offering a novel method for designing tumor therapies.

Palmitic acid-induced insulin resistance triggers granulosa cell senescence by disruption of the UPRmt/mitophagy/lysosome axis

Insulin resistance (IR) is the main pathological feature of polycystic ovary syndrome (PCOS), but the adverse impacts of IR on ovary and granulosa cells (GCs) are unknown. Therefore, the role of palmitic acid (PA) induced IR in GCs, and a mitochondrial proteostasis and mitochondrial homeostasis control system, the mitochondrial unfolded protein response (UPRmt)/mitophagy/lysosome axis were investigated to uncover the side effect and the mechanism of IR on GCs. Our results revealed that IR in GC was successfully constructed by 100 μM PA treatment accompanied with cell senescence. In addition, mitochondrial function was impaired by IR-induced GC senescence accompanied by significantly increased reactive oxygen species (ROS) and decreased mitochondrial membrane potential, and mitochondrial proteostasis was impaired by a dysfunctional UPRmt and increased protein aggregation, leading to more unfolded and misfolded proteins accumulating in mitochondria. Mitochondrial homeostasis was maintained by the mitophagy/lysosome degradation system, although mitophagy was significantly increased, lysosomes were damaged; hence, malfunctional mitochondria were not cleared by the mitophagy/lysosome degradation system, more ROS were produced by malfunctional mitochondria. Therefore, accelerated GC senescence was triggered by excessive ROS, and reversed by the mitophagy inhibitor cyclosporin A (CsA) accompanied with reduced IR. Additionally, the mice were administered with PA, and results revealed that the accelerated ovarian aging was caused by PA, which might be attributed to GC senescence. In conclusion, GC senescence was triggered in PA-induced IR by disruption of the UPRmt/mitophagy/lysosome axis, and IR induced GC senescence was reversed by the CsA.

Differential unfolded protein response regulation in KRAS silencing sensitive and innately resistant colorectal cancer cells

Despite the development of mutant-selective KRAS inhibitors, colorectal cancer (CRC) responses remain limited, with stable disease and rapid recurrence being common outcomes. The molecular mechanisms enabling CRC cells to tolerate KRAS inhibition and ultimately develop resistance remain poorly understood. Here, we investigated early transcriptional and proteomic responses to KRAS silencing in 3D CRC cell line spheroid models, aiming to identify pathways associated with sensitivity or resistance to KRAS blockade. Cell lines were stratified into KRAS silencing-sensitive (HCT116 and SW480) and -resistant (LS174T and SW837) groups based on spheroid growth, cell cycle progression, and apoptosis induction. Transcriptional profiling revealed the unfolded protein response (UPR) and WNT/β-catenin signaling as pathways specifically upregulated in KRAS silencing-sensitive cells and downregulated in resistant cells. Proteomic analysis of membrane-enriched fractions further supported UPR deregulation, showing a pronounced downregulation of translation-related proteins in sensitive cells. Functional assays validated that the sensitive cell line HCT116 exhibits reduced protein aggregation and lower translational capacity upon KRAS knockdown, consistent with UPR activation. Pharmacological inhibition of IRE1α-mediated UPR signaling did not revert KRAS silencing-induced cell cycle arrest or apoptosis in this cell line. Collectively, our results highlight the UPR activation as an early adaptive response of KRAS-dependent CRC cells to KRAS silencing.