Reshaping endoplasmic reticulum quality control through the unfolded protein response

Ubiquitin and Ubiquitin-Like Modifications in Organelle Stress Signaling: Ub, Ub, Ub, Ub, Stayin' Alive, Stayin' Alive

Due to various intracellular and external cues, cellular organelles are frequently stressed in both physiological and pathological conditions. Sensing these stresses initiates various signaling pathways which may lead to adaptation of the stressed cells or trigger its their death. At the unicellular level, this stress signaling involves a crosstalk between different organelles. At the multicellular level, such pathways can contribute to indicate the presence of a stressed cell to its neighboring cells. Here, we highlight the crucial and diverse roles played by Ubiquitin and Ubiquitin-like modification in organelle stress signaling.

Excess dietary sodium restores electrolyte and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron

The maintenance of fluid and electrolyte homeostasis by the kidney requires proper folding and trafficking of ion channels and transporters in kidney epithelia. Each of these processes requires a specific subset of a diverse class of proteins termed molecular chaperones. One such chaperone is GRP170, which is an Hsp70-like, endoplasmic reticulum (ER)-localized chaperone that plays roles in protein quality control and protein folding in the ER. We previously determined that loss of GRP170 in the mouse nephron leads to hypovolemia, electrolyte imbalance, and rapid weight loss. In addition, GRP170-deficient mice develop an acute kidney injury (AKI)-like phenotype, typified by tubular injury, elevation of kidney injury markers, and induction of the unfolded protein response (UPR). By using an inducible GRP170 knockout cellular model, we confirmed that GRP170 depletion induces the UPR, triggers apoptosis, and disrupts protein homeostasis. Based on these data, we hypothesized that UPR induction underlies hyponatremia and volume depletion in these rodents and that these and other phenotypes might be rectified by sodium supplementation. To test this hypothesis, control and GRP170 tubule-specific knockout mice were provided a diet containing 8% sodium chloride. We discovered that sodium supplementation improved electrolyte imbalance and kidney injury markers in a sex-specific manner but was unable to restore weight or tubule integrity. These results are consistent with UPR induction contributing to the kidney injury phenotype in the nephron-specific GR170 knockout model and indicate that GRP170 function in kidney epithelia is essential to both maintain electrolyte balance and ER homeostasis.NEW & NOTEWORTHY Loss of the endoplasmic reticulum chaperone, GRP170, results in widespread kidney injury and induction of the unfolded protein response (UPR). We now show that sodium supplementation is able to at least partially restore electrolyte imbalance and reduce kidney injury markers in a sex-dependent manner.

Tauroursodeoxycholic acid targets HSP90 to promote protein homeostasis and extends healthy lifespan

As the elderly population expands, the pursuit of therapeutics to reduce morbidity and extend lifespan has become increasingly crucial. As an FDA-approved drug for chronic cholestatic liver diseases, tauroursodeoxycholic acid (TUDCA), a natural bile acid, offers additional health benefits beyond liver protection. Here, we show that TUDCA extends the lifespan and healthspan of C. elegans. Importantly, oral supplementation of TUDCA improves fitness in old mice, including clinically relevant phenotypes, exercise capacity and cognitive function. Consistently, TUDCA treatment drives broad transcriptional changes correlated with anti-aging characteristics. Mechanistically, we discover that TUDCA targets the chaperone HSP90 to promote its protein refolding activity. This collaboration further alleviates aging-induced endoplasmic reticulum (ER) stress and facilitates protein homeostasis, thus offering resistance to aging. In summary, our findings uncover new molecular links between an endogenous metabolite and protein homeostasis, and propose a novel anti-aging strategy that could improve both lifespan and healthspan.

Unremodeled GPI-anchored proteins at the plasma membrane trigger aberrant endocytosis

The plasma membrane has a complex organization that includes the polarized distribution of membrane proteins and lipids. Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are ubiquitously expressed in eukaryotes and represent a functionally diverse, extensively remodeled, ER-derived group of proteins critical for the organization and function of the plasma membrane. Little is known about how the transport of incompletely remodeled GPI-APs to the plasma membrane affects cell function. Here, we investigated how failure to remodel mannose 2 (Man2) of the GPI moiety impacted endocytic activity on the plasma membrane. We find that Man2 unremodeled GPI-APs increased membrane disorder and generated a stress response that triggered abnormal ubiquitin- and clathrin-dependent endocytosis. The resulting stress-induced endocytosis disrupted the trafficking repertoire of a subset of plasma membrane proteins, which were redirected, via the multivesicular body, to numerous small vacuoles for degradation. Our findings highlight the critical importance of GPI-AP Man2 remodeling for maintaining the integrity and homeostasis of the plasma membrane.

Ginger-Derived Exosome-Like Nanoparticles Loaded With Indocyanine Green Enhances Phototherapy Efficacy for Breast Cancer

PURPOSE

Phototherapy has remarkable advantages in cancer treatment, owing to its high efficiency and minimal invasiveness. Indocyanine green (ICG) plays an important role in photo-mediated therapy. However, it has several disadvantages such as poor stability in aqueous solutions, easy aggregation of molecules, and short plasma half-life. This study aimed to develop an efficient nanoplatform to enhance the effects of photo-mediated therapy.

METHODS

We developed a novel bio-nanoplatform by integrating edible ginger-derived exosome-like nanoparticles (GDNPs) and the photosensitizer, ICG (GDNPs@ICG). GDNPs were isolated from ginger juice and loaded with ICG by co-incubation. The size distribution, zeta potential, morphology, total lipid content, and drug release behavior of the GDNPs@ICG were characterized. The photothermal performance, cellular uptake and distribution, cytotoxicity, anti-tumor effects, and mechanism of action of GDNPs@ICG were investigated both in vitro and in vivo.

RESULTS

GDNPs@ICG were taken up by tumor cells via a lipid-dependent pathway. When irradiated by an 808 nm NIR laser, GDNPs@ICG generated high levels of ROS, MDA, and local hyperthermia within the tumor, which caused lipid peroxidation and ER stress, thus enhancing the photo-mediated breast tumor therapy effect. Furthermore, in vivo studies demonstrated that engineered GDNPs@ICG significantly inhibited breast tumor growth and presented limited toxicity. Moreover, by detecting the expression of CD31, N-cadherin, IL-6, IFN-γ, CD8, p16, p21, and p53 in tumor tissues, we found that GDNPs@ICG substantially reduced angiogenesis, inhibited metastasis, activated the anti-tumor immune response, and promoted cell senescence in breast tumor.

CONCLUSION

Our study demonstrated that the novel bio-nanoplatform GDNPs@ICG enhanced the photo-mediated therapeutic effect in breast tumor. GDNPs@ICG could be an alternative for precise and efficient anti-tumor phototherapy.

Curcumin Attenuates Fumonisin B1-Induced PK-15 Cell Apoptosis by Upregulating miR-1249 Expression to Inhibit the IRE1/MKK7/JNK/CASPASE3 Signaling Pathway

Fumonisin B1 (FB1) is an important toxin which poses global concerns in terms of food safety. Curcumin (Cur), a natural polyphenolic compound, has strong antioxidant and anti-inflammatory effects. Meanwhile, the mechanisms underlying the mitigation of FB1-induced toxicity by Cur are not fully understood, limiting its potential application as a novel feed additive to prevent FB1 toxicity. In this study, porcine kidney cells (PK-15) were used as an experimental model, utilizing mRNA and miRNA transcriptome technologies. The results revealed that Cur upregulated miR-1249 and inhibited the target gene Ern1 in the PK-15 cells, thereby suppressing the IRE1/MKK7/JNK/CASPASE3 endoplasmic reticulum (ER) stress pathway and alleviating FB1-induced cell apoptosis. Cell transfection experiments confirmed that Cur effectively attenuated the apoptosis induced by ER stress following transfection with a miR-1249 inhibitor. Similarly, transfection with a miR-1249 mimic alleviated the ER stress and FB1-induced PK-15 cell apoptosis. These findings reveal that Cur mitigates FB1-induced ER stress and significantly reduces apoptotic damage in porcine kidney cells.

Targeting endoplasmic reticulum stress: an innovative therapeutic strategy for podocyte-related kidney diseases

The endoplasmic reticulum (ER) is a vital organelle responsible for protein quality control, including the folding, modification, and transport of proteins. When misfolded or unfolded proteins accumulate in the ER, it triggers endoplasmic reticulum stress (ERS) and activates the unfolded protein response (UPR) to restore ER homeostasis. However, prolonged or excessive ERS can lead to apoptosis. The kidneys play a crucial role in maintaining physiological functions by excreting metabolic waste, regulating blood volume, balancing electrolytes and acid-base levels, and secreting various bioactive substances. Podocytes, epithelial cells situated outside the glomerular basement membrane, are essential for maintaining the structural integrity and permeability of the glomerular filtration barrier. Previous studies have shown that ERS in podocytes can contribute to the development of diseases such as glomerulonephritis, hereditary nephropathy, and diabetic kidney disease, potentially progressing to end-stage renal disease and causing patient mortality. As such, investigating ERS in podocytes has become a key area of focus in kidney disease research. This study examines recent advancements in understanding the effects of excessive ERS on podocytes across various kidney diseases, highlights the role of podocyte ERS in disease progression, and explores the potential therapeutic benefits of targeting the UPR to manage ERS in kidney diseases, thereby providing a scientific basis for clinical interventions.

Spatial covariance reveals isothiocyanate natural products adjust redox stress to restore function in alpha-1-antitrypsin deficiency

Alpha-1 antitrypsin (AAT) deficiency (AATD) is a monogenic disease caused by misfolding of AAT variants resulting in gain-of-toxic aggregation in the liver and loss of monomer activity in the lung leading to chronic obstructive pulmonary disease (COPD). Using high-throughput screening, we discovered a bioactive natural product, phenethyl isothiocyanate (PEITC), highly enriched in cruciferous vegetables, including watercress and broccoli, which improves the level of monomer secretion and neutrophil elastase (NE) inhibitory activity of AAT-Z through the endoplasmic reticulum (ER) redox sensor protein disulfide isomerase (PDI) A4 (PDIA4). The intracellular polymer burden of AAT-Z can be managed by combination treatment of PEITC and an autophagy activator. Using Gaussian process (GP)-based spatial covariance (SCV) (GP-SCV) machine learning to map on a residue-by-residue basis at atomic resolution all variants in the worldwide AATD clinical population, we reveal a global rescue of monomer secretion and NE inhibitory activity for most variants triggering disease. We present a proof of concept that GP-SCV mapping of restoration of AAT variant function serves as a standard model to discover natural products such as the anti-oxidant PEITC that could potentially impact the redox/inflammatory environment of the ER to provide a nutraceutical approach to help minimize disease in AATD patients.

Advancements in the treatment of cerebral ischemia-reperfusion injury: Acupuncture combined with mesenchymal stem cells transplantation

Cerebral ischemia-reperfusion injury (CIRI) constitutes a significant etiology of exacerbated cerebral tissue damage subsequent to intravenous thrombolysis and endovascular mechanical thrombectomy in patients diagnosed with acute ischemic stroke. The treatment of CIRI has been extensively investigated through a multitude of clinical studies. Acupuncture has been demonstrated to be effective in treating CIRI. Recent 5 years studies have identified potential mechanisms of acupuncture, including regulation of autophagy, promotion of angiogenesis, inhibition of inflammation and apoptosis, modulation of cell activation, neuroplasticity regulation, and promotion of nerve regeneration. The transplantation of mesenchymal stem cells (MSCs) can effectively suppress apoptosis, modulate immune responses, and enhance the proliferation and migration of endogenous neural stem cells (NSCs), thereby compensating for the NSCs deficiency following cerebral ischemia/reperfusion injury. The combination of acupuncture and MSCs transplantation demonstrates superiority over individual treatments, significantly enhancing the survival rate of MSCs. Moreover, it facilitates the secretion of various cytokines to promote their homing and differentiation into functional neurons, thereby providing a novel approach for clinical treatment of CIRI.

Acrylamide Induces Antiapoptotic Autophagy and Apoptosis by Activating PERK Pathway in SH-SY5Y Cells

Acrylamide (ACR) is a commonly used organic compound that exhibits evident neurotoxicity in humans. Our previous studies showed that the mechanisms of ACR-caused neurotoxicity included apoptosis, PERK-mediated endoplasmic reticulum stress, and autophagy, but the relationships among them were still unclear. This paper investigated the relationships among apoptosis, autophagy, and the PERK pathway to demonstrate the mechanism of ACR neurotoxicity further. Different doses of ACR were set to value ACR toxicity. Then, a PERK inhibitor and autophagy inhibitor, GSK2606414 and 3-methyladenine (3-MA), were used separately to inhibit the PERK pathway and autophagy activation in SH-SY5Y cells under ACR treatment. With the increase of ACR dose, the apoptotic rate increased in a dose-dependent manner. After the inhibition of the PERK pathway, the activated apoptosis and autophagosome accumulation caused by ACR were alleviated. Under 3-MA and ACR treatment, the autophagy inhibition deteriorated apoptosis in SH-SY5Y cells but had no significant effect on ACR-induced PERK pathway activation; thus, PERK pathway-induced autophagy had an antiapoptotic role in this condition. This paper provides an experimental basis for exploring potential molecular targets to prevent and control ACR toxicity.

Dysregulation of PI4P in the trans Golgi regions activates the mammalian Golgi stress response

The Golgi stress response is an important cytoprotective system that enhances Golgi function in response to cellular demand, while cells damaged by prolonged Golgi stress undergo cell death. OSW-1, a natural compound with anticancer activity, potently inhibits OSBP that transports cholesterol and phosphatidylinositol-4-phosphate (PI4P) at contact sites between the endoplasmic reticulum and the Golgi apparatus. Previously, we reported that OSW-1 induces the Golgi stress response, resulting in Golgi stress-induced transcription and cell death. However, the underlying molecular mechanism has been unknown. To reveal the mechanism of a novel pathway of the Golgi stress response regulating transcriptional induction and cell death (the PI4P pathway), we performed a genome-wide KO screen and found that transcriptional induction as well as cell death induced by OSW-1 was repressed by the loss of regulators of PI4P synthesis, such as PITPNB and PI4KB. Our data indicate that OSW-1 induces Golgi stress-dependent transcriptional induction and cell death through dysregulation of the PI4P metabolism in the Golgi.

Organellar quality control crosstalk in aging-related disease: Innovation to pave the way

Organellar homeostasis and crosstalks within a cell have emerged as essential regulatory and determining factors for the survival and functions of cells. In response to various stimuli, cells can activate the organellar quality control systems (QCS) to maintain homeostasis. Numerous studies have demonstrated that dysfunction of QCS can lead to various aging-related diseases such as neurodegenerative, pulmonary, cardiometabolic diseases and cancers. However, the interplay between QCS and their potential role in these diseases are poorly understood. In this review, we present an overview of the current findings of QCS and their crosstalk, encompassing mitochondria, endoplasmic reticulum, Golgi apparatus, ribosomes, peroxisomes, lipid droplets, and lysosomes as well as the aberrant interplays among these organelles that contributes to the onset and progression of aging-related disorders. Furthermore, potential therapeutic approaches based on these quality control interactions are discussed. Our perspectives can enhance insights into the regulatory networks underlying QCS and the pathology of aging and aging-related diseases, which may pave the way for the development of novel therapeutic targets.

Regulation and function of endoplasmic reticulum autophagy in neurodegenerative diseases

The endoplasmic reticulum, a key cellular organelle, regulates a wide variety of cellular activities. Endoplasmic reticulum autophagy, one of the quality control systems of the endoplasmic reticulum, plays a pivotal role in maintaining endoplasmic reticulum homeostasis by controlling endoplasmic reticulum turnover, remodeling, and proteostasis. In this review, we briefly describe the endoplasmic reticulum quality control system, and subsequently focus on the role of endoplasmic reticulum autophagy, emphasizing the spatial and temporal mechanisms underlying the regulation of endoplasmic reticulum autophagy according to cellular requirements. We also summarize the evidence relating to how defective or abnormal endoplasmic reticulum autophagy contributes to the pathogenesis of neurodegenerative diseases. In summary, this review highlights the mechanisms associated with the regulation of endoplasmic reticulum autophagy and how they influence the pathophysiology of degenerative nerve disorders. This review would help researchers to understand the roles and regulatory mechanisms of endoplasmic reticulum-phagy in neurodegenerative disorders.

Targeting SERCA2 in Anti-Tumor Drug Discovery

SERCA2, a P-type ATPase located on the endoplasmic reticulum of cells, plays an important role in maintaining calcium balance within cells by transporting calcium from the cytoplasm to the endoplasmic reticulum against its concentration gradient. A multitude of studies have demonstrated that the expression of SERCA2 is abnormal in a wide variety of tumor cells. Consequently, research exploring compounds that target SERCA2 may offer a promising avenue for the development of novel anti-tumor drugs. This review has summarized the anti-tumor compounds targeting SERCA2, including thapsigargin, dihydroartemisinin, curcumin, galangin, etc. These compounds interact with SERCA2 on the endoplasmic reticulum membrane, disrupting intracellular calcium ion homeostasis, leading to tumor cell apoptosis, autophagy and cell cycle arrest, ultimately producing anti-tumor effects. Additionally, several potential research directions for compounds targeting SERCA2 as clinical anti-cancer drugs have been proposed in the review. In summary, SERCA2 is a promising anti-tumor target for drug discovery and development.

Ginsenoside Rg1 improves cigarette smoke-induced ferroptosis in COPD by regulating PERK/ATF4 axis to inhibit endoplasmic reticulum stress

BACKGROUND

Ferroptosis plays a key role in the development of chronic obstructive pulmonary disease (COPD). Whether ginsenoside Rg1 improves cigarette smoke-induced COPD or whether ginsenoside Rg1 improves COPD by inhibiting ferroptosis remains unknown.

METHODS

BEAS-2B cells were exposed to cigarette solution (CSE) for 24 h and treated with ginsenoside Rg1, the ferroptosis inhibitor Fer-1, and the PERK inhibitor GSK. Cell viability, endoplasmic reticulum stress, mitochondrial morphology, membrane potential, reactive oxygen species (ROS), iron levels, and the expression of related proteins were detected using corresponding methods. A COPD mouse model was constructed using cigarette smoke (CS). Ginsenoside Rg1 and GSK were administered via tube feeding 15 days after successful modeling. Mouse lung tissues were evaluated by HE staining. The expression of inflammatory markers, ROS, iron content, and related proteins was detected using corresponding methods.

RESULTS

The results demonstrated that in the CSE-exposed BEAS-2B cell model and CS-induced mouse COPD model, the expression levels of endoplasmic reticulum stress (ERS)-related factors such as GRP78 were increased, while those of the antioxidant markers GPX4 and GSH were significantly decreased. Ginsenoside Rg1 improved emphysema and inflammation by inhibiting ferroptosis in vivo and in vitro. Using a PERK inhibitor, we found that ginsenoside Rg1 inhibited ferroptosis in vivo and in vitro by regulating ERS.

CONCLUSION

This study showed that ginsenoside Rg1 alleviates cigarette smoke-induced COPD by regulating the PERK/ATF4 axis to inhibit ERS and ferroptosis.

Opposing regulation of endoplasmic reticulum retention under stress by ERp44 and PDIA6

Conditions of endoplasmic reticulum (ER) stress reduce protein synthesis by provoking translation regulation, governed by the eIF2α kinase PERK. When PERK is inhibited during ER stress, retention of a selective subset of glycoproteins occurs, a phenomenon we termed selective ER retention (sERr). sERr clients are enriched with tyrosine kinase receptors (RTKs), which form large molecular weight disulfide bonded complexes in the ER. The protein disulfide isomerase ERp44 promotes sERr and increases the size of sERr complexes. Here we show that sERr is reversible upon washout. Pulse chase analyses show that upon recovery, only a small fraction of the sERr complexes disintegrates and contributes to the matured proteins, while most are newly synthesized. Sequential inductions of sERr and washouts demonstrate an accelerated recovery that is dependent on the unfolded protein response transducer IRE1. Since IRE1 regulates the expression level PDIA6, we analyzed its contribution to sERr. We found that PDIA6 and ERp44 constitutively interact by disulfides and have opposite effects on resumed recovery of trafficking following removal of sERr conditions. Deletion of ERp44 accelerates, while deletion of PDIA6 slows down recovery with a minimal effect on total protein synthesis. ERp44 is a primary interactor with sERr clients. When missing, PDIA6 partitions more into sERr complexes. Deletion of the tumor suppressor PTEN, which induces RTK signaling, promoted sERr formation kinetics, and accelerated the recovery, suggesting feedback between RTKs signaling and sERr. This study suggests that sERr, should develop physiologically or pathologically, is counteracted by adaptation responses that involve IRE1 and PDIA6.

Understanding the impact of ER stress on lung physiology

Human lungs consist of a distinctive array of cell types, which are subjected to persistent challenges from chemical, mechanical, biological, immunological, and xenobiotic stress throughout life. The disruption of endoplasmic reticulum (ER) homeostatic function, triggered by various factors, can induce ER stress. To overcome the elevated ER stress, an adaptive mechanism known as the unfolded protein response (UPR) is activated in cells. However, persistent ER stress and maladaptive UPR can lead to defects in proteostasis at the cellular level and are typical features of the lung aging. The aging lung and associated lung diseases exhibit signs of ER stress-related disruption in cellular homeostasis. Dysfunction resulting from ER stress and maladaptive UPR can compromise various cellular and molecular processes associated with aging. Hence, comprehending the mechanisms of ER stress and UPR components implicated in aging and associated lung diseases could enable to develop appropriate therapeutic strategies for the vulnerable population.

A New Insight into the Mechanism of Atrazine-Induced Neurotoxicity: Triggering Neural Stem Cell Senescence by Activating the Integrated Stress Response Pathway

Atrazine (AT), a widely utilized chemical herbicide, causes widespread contamination of agricultural water bodies. Recently, exposure to AT has been linked to the development of age-related neurodegenerative diseases (NDs), suggesting its neurotoxicity potential. As an endocrine disruptor, AT targets the hypothalamus, a crucial part of the neuroendocrine system. However, the toxicological mechanism of AT exposure to the hypothalamus and its correlation with ND development remain unexplored. Our results indicated that AT exposure caused significant morphological and structural damage to the hypothalamus, leading to the loss of mature and intact neurons and microglial activation. Furthermore, hypothalamic neural stem cells (HtNSCs) were recruited to areas of neuronal damage caused by AT. Through in vivo and in vitro experiments, we clarified the outcomes of AT-induced HtNSC recruitment alongside the loss of mature/intact neurons. Mechanistically, AT induces senescence in these recruited HtNSCs by activating integrated stress response signaling. This consequently hinders the repair of damaged neurons by inhibiting HtNSC proliferation and differentiation. Overall, our findings underscore the pivotal role of the integrated stress response pathway in AT-induced HtNSC senescence and hypothalamic damage. Additionally, the present study offers novel perspectives to understand the mechanisms of AT-induced neurotoxicity and provides preliminary evidence linking AT contamination to the development of NDs.

Glomerular Elasticity and Gene Expression Patterns Define Two Phases of Alport Nephropathy

Objectives

To understand the early stages if Alport nephropathy, we characterize the structural, functional, and biophysical properties of glomerular capillaries and podocytes in Col4α3 -/- mice, analyze kidney cortex transcriptional profiles at three time points, and investigate the effects of the ER stress mitigation by TUDCA on these parameters. We use human FSGS associated genes to identify molecular pathways rescued by TUDCA.

Findings

We define a disease progression timeline in Col4α3 -/- mice. Podocyte injury is evident by 3 months, with glomeruli reaching maximum deformability at 4 months, associated with 40% podocytes loss, followed by progressive capillary stiffening, increasing proteinuria, reduced renal function, inflammatory infiltrates, and fibrosis from months 4 to 7. RNA sequencing at 2, 4, and 7 months reveals increased cytokine and chemokine signaling, matrix and cell injury, and activation of the TNF pathway genes by 7 months, similar to NEPTUNE FSGS cohorts. These features are suppressed by TUDCA.

Conclusions

We define two phases of Col4α3 -/- nephropathy. The first is characterized by podocytopathy, increased glomerular capillary deformability and accelerated podocyte loss, and the second by increased capillary wall stiffening and renal inflammatory and profibrotic pathway activation. Disease suppression by TUDCA treatment identifies potential therapeutic targets for treating Alport and related nephropathies.

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.

Mitochondria remodeling during endometrial stromal cell decidualization

Upon hormonal stimulation, uterine endometrial stromal cells undergo a dramatic morpho-functional metamorphosis that allows them to secrete large amounts of matrix proteins, cytokines, and growth factors. This step, known as decidualization, is crucial for embryo implantation. We previously demonstrated how the secretory pathway is remodelled during this process. Here we show that hormonal stimulation rapidly induces the expression of many mitochondrial genes, encoded in both the mitochondrial and the nuclear genomes. Altogether, the mitochondrial network quadruples its size and establishes more contacts with the ER. This new organization results in the increased respiratory capacity of decidualized cells. These findings reveal how achieving an efficient secretory phenotype requires a radical metabolic rewiring.

Endoplasmic reticulum stress-mediated apoptosis and autophagy in osteoarthritis: From molecular mechanisms to therapeutic applications

Osteoarthritis (OA) is characterized primarily by the degeneration of articular cartilage, with a high prevalence and disability rate. The functional phenotype of chondrocytes, as the sole cell type within cartilage, is vital for OA progression. Due to the avascular nature of cartilage and its limited regenerative capacity, repair following injury poses significant challenges. Various cellular stressors, including hypoxia, nutrient deprivation, oxidative stress, and collagen mutations, can lead to the accumulation of misfolded proteins in the endoplasmic reticulum (ER), resulting in ER stress (ERS). In response to restore ER homeostasis as well as cellular vitality and function, a series of adaptive mechanisms are triggered, including the unfolded protein response, ER-associated degradation, and ER-phagy. Prolonged or severe ERS may exceed the adaptive capacity of cells, leading to dysregulation in apoptosis and autophagy-key pathogenic factors contributing to chondrocyte damage and OA progression. This review examines the relationship between ERS in OA chondrocytes and both apoptosis and autophagy in order to identify potential therapeutic targets and strategies for prevention and treatment of OA.

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

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

Deltamethrin exposure caused renal inflammation and renal fibrosis via upregulating endoplasmic reticulum stress-mediated TXNDC5 level in mice

Deltamethrin (DLM) is a type II pyrethroid insecticide that is extensively applied to agriculture, veterinary medicine and livestock pest control. Excessive accumulation of DLM in the body can lead to nephrotoxicity, but the precise toxic mechanism remains obscure. Therefore, we established in vivo models of DLM-exposed mice for 30 days and in vitro models of DLM-exposed renal tubular epithelial cells of mice. The results revealed adverse effects on renal function in mice exposed to excessive DLM, manifested as endoplasmic reticulum (ER) swelling, local inflammatory infiltration in renal tissue and increased collagen fibers, suggesting renal inflammation and fibrosis, etc. Subsequently, in vivo experiments, we found that DLM exposure increased expression levels of endoplasmic reticulum stress (ERS)-related factors, significantly upregulated the expression of TXNDC5, and enhanced the colocalization of GRP78 with TXNDC5. Notably, DLM exposure also strengthened the co-localization of TXNDC5 with NF-κB p65 and TGF-β1, upregulated the expression levels of TLR4/MYD88/NF-κB and TGF-β/SMAD2/3 pathways, alongside inflammation and fibrosis-related factors, these changes exhibited a dose-dependent effect. Meanwhile, in vitro experiments, the results of ERS, inflammation, and fibrosis-related factor expression levels were consistent with those observed in vivo. In conclusion, our results demonstrated that TXNDC5 might played a certain role in DLM-induced nephrotoxicity. Specifically, DLM exposure could trigger ERS, increase TXNDC5 expression, and promote TLR4/MYD88/NF-κB and TGF-β/Smad2/3 pathways, leading to renal inflammation and fibrosis in mice. These discoveries not only deepen our understanding of DLM toxicity but also provide valuable avenues for exploring mitigation strategies and therapeutic interventions.

Research Progress of Endoplasmic Reticulum Targeting Metal Complexes in Cancer Therapy

The development of anticancer drugs that target different organelles has received extensive attention due to the characteristics of cancer recurrence, metastasis, and drug resistance. The endoplasmic reticulum (ER) is an important structure within the cell that is primarily responsible for protein synthesis, folding, modification, and transport and plays a crucial role in cell function and health. ER stress activation induces cancer cell apoptosis. New anticancer drugs with different anticancer mechanisms and selectivity can be designed because of redox activity, composition diversity, and metal complexes structure regulation. Over the past few decades, dozens of metal complexes have killed cancer cells through ER stress, showing powerful tumor-suppressive effects. This review summarizes the progress of research on anticancer metallic drugs that induce ER stress over the past few years, which is expected to bring more breakthroughs in the field of medicine and life science.

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

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

A ubiquitin-mediated post-translational degradation of Cyp51A contributes to a novel azole resistance mode in Aspergillus fumigatus

The airborne fungus Aspergillus fumigatus is a major pathogen that poses a serious health threat to humans by causing aspergillosis. Azole antifungals inhibit sterol 14-demethylase (encoded by cyp51A), an enzyme crucial for fungal cell survival. However, the most common mechanism of azole resistance in A. fumigatus is associated with the mutations in cyp51A and tandem repeats in its promoter, leading to reduced drug-enzyme interaction and overexpression of cyp51A. It remains unknown whether post-translational modifications of Cyp51A contribute to azole resistance. In this study, we report that the Cyp51A expression is highly induced upon exposure to itraconazole, while its ubiquitination level is significantly reduced by itraconazole. Loss of the ubiquitin-conjugating enzyme Ubc7 confers resistance to multiple azole antifungals but hinders hyphal growth, conidiation, and virulence. Western blot and immunoprecipitation assays show that deletion of ubc7 reduces Cyp51A degradation by impairing its ubiquitination, thereby leading to drug resistance. Most importantly, the overexpression of ubc7 in common environmental and clinical azole-resistant cyp51A isolates partially restores azole sensitivity. Our findings demonstrate a non-cyp51A mutation-based resistance mechanism and uncover a novel role of post-translational modification in contributing to azole resistance in A. fumigatus.

CTGF regulated by ATF6 inhibits vascular endothelial inflammation and reduces hepatic ischemia-reperfusion injury

Vascular endothelial inflammation is crucial in hepatic ischemia-reperfusion injury (IRI). Our previous research has shown that connective tissue growth factor (CTGF), secreted by endothelial cells, protects against acute liver injury, but its upstream mechanism is unclear. We aimed to clarify the protective role of CTGF in endothelial cell inflammation during IRI and reveal the regulation between endoplasmic reticulum stress-induced activating transcription factor 6 (ATF6) and CTGF. Hypoxia/reoxygenation in endothelial cells, hepatic IRI in mice and clinical specimens were used to examine the relationships between CTGF and inflammatory factors and determine how ATF6 regulates CTGF and reduces damage. We found that activating ATF6 promoted CTGF expression and reduced liver damage in hepatic IRI. In vitro, activated ATF6 upregulated CTGF and downregulated inflammation, while ATF6 inhibition had the opposite effect. Dual-luciferase assays and chromatin immunoprecipitation confirmed that activated ATF6 binds to the CTGF promoter, enhancing its expression. Activated ATF6 increases CTGF and reduces extracellular regulated protein kinase 1/2 (ERK1/2) phosphorylation, decreasing inflammatory factors. Conversely, inhibiting ATF6 decreases CTGF and increases the phosphorylation of ERK1/2, increasing inflammatory factor levels. ERK1/2 inhibition reverses this effect. Clinical samples have shown that CTGF increases after IRI, inversely correlating with inflammatory cytokines. Therefore, ATF6 activation during liver IRI enhances CTGF expression and reduces endothelial inflammation via ERK1/2 inhibition, providing a novel target for diagnosing and treating liver IRI.

ER stress as a sentinel mechanism for ER Ca2+ homeostasis

Endoplasmic reticulum (ER) stress is triggered upon the interference with oxidative protein folding that aims to produce fully folded, disulfide-bonded and glycosylated proteins, which are then competent to exit the ER. Many of the enzymes catalyzing this process require the binding of Ca2+ ions, including the chaperones BiP/GRP78, calnexin and calreticulin. The induction of ER stress with a variety of drugs interferes with chaperone Ca2+ binding, increases cytosolic Ca2+through the opening of ER Ca2+ channels, and activates store-operated Ca2+ entry (SOCE). Posttranslational modifications (PTMs) of the ER Ca2+ handling proteins through ER stress-dependent phosphorylation or oxidation control these mechanisms, as demonstrated in the case of the sarco/endoplasmic reticulum ATPase (SERCA), inositol 1,4,5 trisphosphate receptors (IP3Rs) or stromal interaction molecule 1 (STIM1). Their aim is to restore ER Ca2+ homeostasis but also to increase Ca2+ transfer from the ER to mitochondria during ER stress. This latter function boosts ER bioenergetics, but also triggers apoptosis if ER Ca2+ signaling persists. ER Ca2+ toolkit oxidative modifications upon ER stress can occur within the ER lumen or in the adjacent cytosol. Enzymes involved in this redox control include ER oxidoreductin 1 (ERO1) or the thioredoxin-family protein disulfide isomerases (PDI) and ERp57. A tight, but adaptive connection between ER Ca2+ content, ER stress and mitochondrial readouts allows for the proper functioning of many tissues, including skeletal muscle, the liver, and the pancreas, where ER stress either maintains or compromises their function, depending on its extent and context. Upon mutation of key regulators of ER Ca2+ signaling, diseases such as muscular defects (e.g., from mutated selenoprotein N, SEPN1/SELENON), or diabetes (e.g., from mutated PERK) are the result.

IRE1β evolves to be a guardian of respiratory and gastrointestinal mucosa

Inositol-requiring enzyme 1 (IRE1), a mediator of the unfolded protein response, shows the highest degree of evolutionary conservation. Vertebrates express two IRE1 paralogs: IRE1α, which is universally expressed and IRE1β, which shows specific expression within mucus secreted cells in respiratory and gastrointestinal tracts. The biological properties and regulation of the two IRE1 duplicates show evolutionary differences. As recently suggested, IRE1β-deficient mice display impairment in secreted protein expression and mucosal homeostasis. Abnormal changes in IRE1β caused by external and internal factors can disrupt mucosal homeostasis and further lead to respiratory and gastrointestinal diseases. Here, we highlight the physiological functions of IRE1β in the respiratory and gastrointestinal tracts in response to environmental microbes, viruses, toxins, and food components.

Central role of the ER proteostasis network in healthy aging

Aging trajectories vary among individuals, characterized by progressive functional decline, often leading to disease states. One of the central hallmarks of aging is the deterioration of proteostasis, where the function of the endoplasmic reticulum (ER) is dramatically affected. ER stress is monitored and adjusted by the unfolded protein response (UPR); a signaling pathway that mediates adaptive processes to restore proteostasis. Studies in multiple model organisms (yeast, worms, flies, and mice) in addition to human tissue indicates that adaptive UPR signaling contributes to healthy aging. Strategies to improve ER proteostasis using small molecules and gene therapy reduce the decline of organ function during normal aging in mammals. This article reviews recent advances in understanding the significance of the ER proteostasis network to normal aging and its relationship with other hallmarks of aging such as senescence.

Compound 4a induces paraptosis in liver cancer through endoplasmic reticulum stress mediated by the calreticulin protein

BACKGROUND AND PURPOSE

Emerging evidence has highlighted that paraptosis may be an effective strategy for treating liver cancer. In our previous studies, Compound 4a induced paraptosis in cancer cells. Here, the characteristics of Compound 4a-induced paraptosis were further revealed and, for the first time, the target and related molecular mechanisms of Compound 4a-induced paraptosis in liver cancer were defined.

EXPERIMENTAL APPROACH

The effects and mechanism of Compound 4a in liver cancer cells were studied in in vitro and in vivo (BALB/c-nude xenograft model) experiments, and the targets of Compound 4a that trigger paraptosis were identified and confirmed via mass spectrometry-based drug affinity responsive target stability (DARTS) analyses, siRNA experiments and a cellular thermal shift assay (CETSA). The function and distribution of calreticulin (CRT) protein were detected via Cal-520 AM and immunofluorescence staining, respectively.

KEY RESULTS

Compound 4a effectively induced paraptosis-like cell death in liver cancer, both in vitro and in vivo, and its effect was comparable with the first-line anti-liver cancer drug oxaliplatin but with a higher safety profile. We identified the CRT protein as a target of Compound 4a, which caused cellular endoplasmic reticulum stress (ERS) and calcium overload. CRT knockdown weakened the anti-liver cancer activity of Compound 4a, which may be related to the inhibition of paraptosis.

CONCLUSION

Compound 4a represents a potentially safe and effective agent for the treatment of liver cancer. The characteristics of Compound 4a-triggered paraptosis was clarified and a unique function of CRT in paraptosis was revealed.

DEPTOR attenuates asthma progression by suppressing endoplasmic reticulum stress through SOD1

Endoplasmic reticulum (ER) stress has been shown to play a pivotal role in the pathogenesis of asthma. DEPTOR (DEP Domain Containing MTOR Interacting Protein) is an endogenous mTOR inhibitor that participates in various physiological processes such as cell growth, apoptosis, autophagy, and ER homeostasis. However, the role of DEPTOR in the pathogenesis of asthma is still unknown. In this study, an ovalbumin (OVA)-induced mice model and IL-13 induced 16HBE cells were used to evaluate the effect of DEPTOR on asthma. A decreased DEPTOR expression was shown in the lung tissues of OVA-mice and IL-13 induced 16HBE cells. Upregulation of DEPTOR attenuated airway goblet cell hyperplasia, inhibited mucus hypersecretion, decreased the expression of mucin MUC5AC, and suppressed the level of inflammatory factors IL-4 and IL-5, which were all induced by OVA treatment. The increased protein expression of ER stress markers GRP78, CHOP, unfolded protein response (UPR) related proteins, and apoptosis markers in OVA mice were also inhibited by DEPTOR overexpression. In IL-13 induced 16HBE cells, overexpression of DEPTOR decreased IL-4, IL-5, and MUC5AC levels, preventing ER stress response and UPR process. Furthermore, from the proteomics results, we identified that SOD1 (Cu/Zn Superoxide Dismutase 1) may be the downstream factor of DEPTOR. Similar to DEPTOR, upregulation of SOD1 alleviated asthma progression. Rescue experiments showed that SOD1 inhibition abrogates the remission effect of DEPTOR on ER stress in vitro. In conclusion, these data suggested that DEPTOR attenuates asthma progression by suppressing endoplasmic reticulum stress through SOD1.

Monitoring Glutathione Content of the Endoplasmic Reticulum under Scrap Leather-Induced Endoplasmic Reticulum Stress via an Endoplasmic Reticulum-Targeted Two-Photon Fluorescent Probe

Maintaining tissue homeostasis necessitates the coordinated efforts of various cell types to regulate inflammation. Endoplasmic reticulum (ER) stress, a hallmark of inflammation, exacerbates tissue pathology in various human diseases. Glutathione (GSH), a pivotal regulator of cellular redox balance, controls disulfide bond formation in the ER, thereby shielding cells from oxidative stress. In this study, we developed a two-photon fluorescent probe, ER-GSH, with specific ER targeting and demonstrated its high sensitivity and rapid response to GSH. Experiments conducted on BV2 cells and a mice model of neuroinflammation induced by scrap leather revealed that inflammatory reactions led to ER stress and a substantial reduction in GSH levels. Notably, the anti-inflammatory drug NS-398 effectively inhibited cell inflammation and ER stress by maintaining GSH levels. These findings underscore the potential therapeutic significance of modulating GSH levels to alleviate the impact of neuroinflammation.

Comparative evaluation of the modulatory role of 1,25-dihydroxy-vitamin D3 on endoplasmic reticulum stress-induced effects in 2D and 3D cultures of the intestinal porcine epithelial cell line IPEC-J2

BACKGROUND

The use of conventional two-dimensional (2D) culture of the porcine intestinal epithelial cell (IEC) line IPEC-J2 in animal nutrition research has the disadvantage that IEC function is studied under unphysiological conditions, which limits the ability of transferring knowledge to the in vivo-situation. Thus, the aim of the present study was to establish a more convincing and meaningful three-dimensional (3D) culture of IPEC-J2 cells, which allows to study cell function in a more tissue-like environment, and to compare the effect of the endoplasmic reticulum (ER) stress inducer tunicamycin (TM) on ER stress indicators and the expression of tight junction proteins (TJP), inflammatory and apoptosis-related genes and the modulatory role of 1,25-dihydroxy-vitamin D3 (1,25D3) on these parameters in 2D and 3D cultures of IPEC-J2 cells.

RESULTS

A published protocol for 3D culture of Caco-2 cells was successfully adopted to IPEC-J2 cells as evident from fully differentiated 3D IPEC-J2 spheroids showing the characteristic spherical architecture with a single layer of IPEC-J2 cells surrounding a central lumen. Treatment of 2D IPEC-J2 cells and 3D IPEC-J2 spheroids with TM for 24 h markedly increased mRNA and/or protein levels of the ER stress target genes, heat shock protein family A (Hsp70) member 5 (HSPA5) and DNA damage inducible transcript 3 (DDIT3), whereas co-treatment with TM and 1,25D3 did not mitigate TM-induced ER stress in IPEC-J2 cells in the 2D and the 3D cell culture. In contrast, TM-induced expression of pro-inflammatory [interleukin-6 (IL6), IL8] and pro-apoptotic genes [BCL2 associated X, apoptosis regulator (BAX), caspase 3 (CASP3), CASP8] and genes encoding TJP [TJP1, claudin 1 (CLDN1), CLDN3, occludin (OCLN), cadherin 1 (CDH1), junctional adhesion molecule 1 (JAM1)] was reduced by co-treatment with TM and 1,25D3 in 3D IPEC-J2 spheroids but not in the 2D cell culture.

CONCLUSIONS

The effect of 1,25D3 in the IPEC-J2 cell culture is dependent on the culture model applied. While 1,25D3 does not inhibit TM-induced expression of genes involved in inflammation, apoptosis and TJP in conventional 2D cultures of IPEC-J2 cells, TM-induced expression of these genes is abrogated by 1,25D3 in the more meaningful 3D IPEC-J2 cell culture model.

Deoxynivalenol-mediated kidney injury via endoplasmic reticulum stress in mice

OBJECTIVE

Deoxynivalenol (DON) is a common fungal toxin that poses significant health risks to humans and animals. The present study aimed to investigate the adverse effects and molecular mechanisms of DON-induced kidney injury.

METHODS

Male C57BL/6 mice aged 5-6 weeks were used to establish a DON-induced acute kidney injury model. Histological analysis, biochemical assays, molecular techniques, Western blot, RNA sequencing, and transmission electron microscopy were employed to analyze kidney damage, inflammation, oxidative stress, apoptosis, and endoplasmic reticulum (ER) stress.

RESULTS

DON disrupted kidney morphology, induced inflammatory cell infiltration, and triggered inflammatory responses. DON increased MDA content while decreasing antioxidant enzyme activity (SOD and CAT). It also triggered apoptosis, evidenced by elevated levels of caspase-12, cleaved caspase-3, and BAX, and reduced levels of Bcl-2. Transcriptomic analysis identified distinct expression patterns in 1756 genes in DON-exposed mouse kidneys, notably upregulating ER stress-related genes. Further investigation revealed ultrastructural changes in the ER and mitochondrial damage induced by DON, along with increased levels of p-IRE1, p-PERK, and their downstream targets, indicating unfolded protein response (UPR) activation in the kidney. The ER stress inhibitor 4-Phenylbutyric acid (4-PBA) significantly mitigated DON-induced ER stress, oxidative damage, apoptosis, tissue injury, ER expansion, and mitochondrial damage.

CONCLUSION

Our findings highlight the role of ER stress in DON-induced kidney injury and the protective effect of 4-PBA against these adverse effects.

The physiological role of the unfolded protein response in the nervous system

The unfolded protein response (UPR) is a cellular stress response pathway activated when the endoplasmic reticulum, a crucial organelle for protein folding and modification, encounters an accumulation of unfolded or misfolded proteins. The UPR aims to restore endoplasmic reticulum homeostasis by enhancing protein folding capacity, reducing protein biosynthesis, and promoting protein degradation. It also plays a pivotal role in coordinating signaling cascades to determine cell fate and function in response to endoplasmic reticulum stress. Recent research has highlighted the significance of the UPR not only in maintaining endoplasmic reticulum homeostasis but also in influencing various physiological processes in the nervous system. Here, we provide an overview of recent findings that underscore the UPR's involvement in preserving the function and viability of neuronal and myelinating cells under physiological conditions, and highlight the critical role of the UPR in brain development, memory storage, retinal cone development, myelination, and maintenance of myelin thickness.

Targeting endoplasmic reticulum stress-induced lymphatic dysfunction for mitigating bisphosphonate-related osteonecrosis

BACKGROUND

Bisphosphonates (BPs) are the first-line treatment to stop bone resorption in diseases, including osteoporosis, Paget's disease, multiple myeloma and bone metastases of cancer. However, BPs-related osteonecrosis of the jaw (BRONJ), characterized by local inflammation and jawbone necrosis, is a severe intractable complication. The cumulative inflammatory burden often accompanies impaired lymphatic drainage, but its specific impact on BRONJ and the underlying mechanisms remain unclear.

METHODS

The mouse BRONJ model was established to assess the integrity and drainage function of lymphatic vessels by tissue clearing techniques, injected indocyanine green lymphatic clearance assay, flow cytometry analysis and histopathological staining. RNA sequencing, metabolome analysis, transmission electron microscopy and Western blotting were utilized to analyze the impacts of Zoledronate acid (ZA) on endoplasmic reticulum stress (ERS) and function of lymphatic endothelial cells (LECs). By constructing Lyve1creERT; SIRT6f/f and Lyve1creERT; ATG5f/f mice, we evaluated the role of ERS-induced LECs apoptosis in the progression of BRONJ. Additionally, we developed a nanoparticle-loaded ZA and rapamycin (ZDPR) to enhance autophagy and evaluated its potential in mitigating BRONJ.

RESULTS

The mouse BRONJ model displayed impaired lymphatic drainage, accompanied by significant local inflammation and bone necrosis. The prolonged stimulation of ZA resulted in the extension of ERS and the inhibition of autophagy in LECs, ultimately leading to apoptosis. Mechanistically, ZA activated XBP1s through the NAD+/SIRT6 pathway, initiating ERS-induced apoptosis in LECs. The conditional knockout mouse models demonstrated that the deletion of SIRT6 or ATG5 significantly worsened lymphatic drainage and inflammatory infiltration in BRONJ. Additionally, the innovative nanoparticle ZDPR alleviated ERS-apoptosis in LECs and enhanced lymphatic function, facilitating inflammation resolution.

CONCLUSION

Our study has elucidated the role of the NAD+/SIRT6/XBP1s pathway in ERS-induced apoptosis in ZA-treated LECs, and further confirmed the therapeutic potential of ZDPR in restoring endothelial function and improving lymphatic drainage, thereby effectively mitigating BRONJ.

KEY POINTS

Bisphosphonate-induced lymphatic drainage impairment exacerbates bone necrosis. Zoledronate acid triggers endoplasmic reticulum stress and apoptosis in lymphatic endothelial cells via the NAD+/SIRT6/XBP1s pathway. Novel nanoparticle-loaded Zoledronate acid and rapamycin enhances autophagy, restores lymphatic function, and mitigates bisphosphonates-related osteonecrosis of the jaw progression.

ER-phagy restrains inflammatory responses through its receptor UBAC2

ER-phagy, a selective form of autophagic degradation of endoplasmic reticulum (ER) fragments, plays an essential role in governing ER homeostasis. Dysregulation of ER-phagy is associated with the unfolded protein response (UPR), which is a major clue for evoking inflammatory diseases. However, the molecular mechanism underpinning the connection between ER-phagy and disease remains poorly defined. Here, we identified ubiquitin-associated domain-containing protein 2 (UBAC2) as a receptor for ER-phagy, while at the same time being a negative regulator of inflammatory responses. UBAC2 harbors a canonical LC3-interacting region (LIR) in its cytoplasmic domain, which binds to autophagosomal GABARAP. Upon ER-stress or autophagy activation, microtubule affinity-regulating kinase 2 (MARK2) phosphorylates UBAC2 at serine (S) 223, promoting its dimerization. Dimerized UBAC2 interacts more strongly with GABARAP, thus facilitating selective degradation of the ER. Moreover, by affecting ER-phagy, UBAC2 restrains inflammatory responses and acute ulcerative colitis (UC) in mice. Our findings indicate that ER-phagy directed by a MARK2-UBAC2 axis may provide targets for the treatment of inflammatory disease.

RHBDF1 promotes PERK expression through the JNK/FoxO3 pathway in breast cancer cells

Human rhomboid family-1 ( RHBDF1) gene is recognized as an oncogene involved in breast cancer development. Previous studies have indicated that RHBDF1 contributes significantly to endoplasmic reticulum (ER) protein homeostasis by stabilizing the binding immunoglobulin protein (BiP) and promoting the unfolded protein response (UPR). Here, we report a relationship between RHBDF1 and the ER stress sensors PERK, IRE1, and ATF6. We show that RHBDF1 deficiency in breast cancer cells results in decreased levels of PERK, pPERK, and peIF2α. These protein levels can be restored in RHBDF1-deficient breast cancer cells by artificial overexpression of RHBDF1 but not IRE1 or ATF6. Additionally, we show that the transcription factor FoxO3 is essential for the RHBDF1-mediated production of PERK. Subsequent analysis reveals that RHBDF1 activates JNK, which causes FoxO3 to translocate into the cell nucleus. These findings demonstrate that RHBDF1 supports the UPR by upregulating the PERK/peIF2α pathway via the JNK/FoxO3 axis and that the functions of RHBDF1 are essential for preserving the homeostasis of ER proteins.

The role of lipase maturation factor 1 in hypertriglyceridaemia and atherosclerosis: An update

Lipase maturation factor 1 is an endoplasmic reticulum-resident transmembrane protein, which acts as a critical chaperone necessary for the folding, dimerisation, and secretion of lipases. In this review, we summarise data about the recently revealed role of lipase maturation factor 1 in endoplasmic reticulum redox homeostasis, its novel interaction partners among oxidoreductases and lectin chaperones, and the identification of fibronectin and the low-density lipoprotein receptor as novel non-lipase client proteins of lipase maturation factor 1. Additionally, the role of lipase maturation factor 1-derived circular RNA in atherosclerosis progression via the miR-125a-3p/vascular endothelial growth factor A\Fibroblast Growth Factor 1 axis is discussed. Finally, we focus on the causative role of lipase maturation factor 1 variants in the development of hypertriglyceridaemia - a type of dyslipidaemia that significantly contributes to the development of atherosclerosis and other cardiovascular diseases via different mechanisms.

Multi-omics analyses were combined to construct ubiquitination-related features in colon adenocarcinoma and identify ASNS as a novel biomarker

Background

As one of the malignant tumors with the highest incidence and fatality in the world, colon adenocarcinoma (COAD) has a very complex pathogenic mechanism, which has not yet been fully elucidated. Ubiquitin can regulate cell proliferation, cell cycle, apoptosis, DNA damage repair, and other processes by changing the activity of substrate proteins or causing ubiquitin-proteasome degradation. These are the key links in the pathogenesis of COAD, and ubiquitin plays an important role in the occurrence and development of COAD.

Methods

We integrated transcriptomics, single-cell and clinical omics, and TCGA and GEO databases of COAD patient data. Cox and Lasso regression was employed to assess ubiquitination genes in COAD for generating ubiquitination-related features. The aim was to evaluate the prognostic value of these features for tumors and their impact on the immune microenvironment. At the same time, the expression level of model genes was further analyzed using single-cell data. Finally, the expression and function of ASNS, a key gene for this trait, were detected in vitro.

Results

In our study, based on identifiable changes in the expression of marker genes, this feature can be used to classify patients with COAD. Kaplan-Meier survival analysis indicated that those with elevated risk scores in each cohort experienced inferior outcomes. There is good validation in both the training queue and the validation queue. The results of the immune infiltration analysis showed that the immune infiltration rate was significantly increased in the high-risk group. After the knockdown of ASNS, an important gene in the signature, the activity and migration capacity of SW620 and RKO cell lines and colony formation capacity were dramatically reduced in cell tests.

Conclusion

We screened ubiquitination-related genes and constructed ubiquitination-related features, which can be used as reliable prognostic indicators of COAD. ASNS was identified as a possible biomarker for COAD.

Unstressing the Reticulum: Nutritional Strategies for Modulating Endoplasmic Reticulum Stress in Obesity

The progression of obesity involves several molecular mechanisms that are closely associated with the pathophysiological response of the disease. Endoplasmic reticulum (ER) stress is one such factor. Lipotoxicity disrupts endoplasmic reticulum homeostasis in the context of obesity. Furthermore, it induces ER stress by activating several signaling pathways via inflammatory responses and oxidative stress. ER performs crucial functions in protein synthesis and lipid metabolism; thus, triggers such as lipotoxicity can promote the accumulation of misfolded proteins in the organelle. The accumulation of these proteins can lead to metabolic disorders and chronic inflammation, resulting in cell death. Thus, alternatives, such as flavonoids, amino acids, and polyphenols that are associated with antioxidant and anti-inflammatory responses have been proposed to attenuate this response by modulating ER stress via the administration of nutrients and bioactive compounds. Decreasing inflammation and oxidative stress can reduce the expression of several ER stress markers and improve clinical outcomes through the management of obesity, including the control of body weight, visceral fat, and lipid accumulation. This review explores the metabolic changes resulting from ER stress and discusses the role of nutritional interventions in modulating the ER stress pathway in obesity.

Chaperone BiP controls ER stress sensor Ire1 through interactions with its oligomers

The complex multistep activation cascade of Ire1 involves changes in the Ire1 conformation and oligomeric state. Ire1 activation enhances ER folding capacity, in part by overexpressing the ER Hsp70 molecular chaperone BiP; in turn, BiP provides tight negative control of Ire1 activation. This study demonstrates that BiP regulates Ire1 activation through a direct interaction with Ire1 oligomers. Particularly, we demonstrated that the binding of Ire1 luminal domain (LD) to unfolded protein substrates not only trigger conformational changes in Ire1-LD that favour the formation of Ire1-LD oligomers but also exposes BiP binding motifs, enabling the molecular chaperone BiP to directly bind to Ire1-LD in an ATP-dependent manner. These transient interactions between BiP and two short motifs in the disordered region of Ire1-LD are reminiscent of interactions between clathrin and another Hsp70, cytoplasmic Hsc70. BiP binding to substrate-bound Ire1-LD oligomers enables unfolded protein substrates and BiP to synergistically and dynamically control Ire1-LD oligomerisation, helping to return Ire1 to its deactivated state when an ER stress response is no longer required.

UPS-dependent strategies of protein quality control degradation

The degradation of damaged proteins is critical for tissue integrity and organismal health because damaged proteins have a high propensity to form aggregates. E3 ubiquitin ligases are key regulators of protein quality control (PQC) and mediate the selective degradation of damaged proteins, a process termed 'PQC degradation' (PQCD). The degradation signals (degrons) that trigger PQCD are based on hydrophobic sites that are normally buried within the native protein structure. However, an open question is how PQCD-specialized E3 ligases distinguish between transiently misfolded proteins, which can be efficiently refolded, and permanently damaged proteins, which must be degraded. While significant progress has been made in characterizing degradation determinants, understanding the key regulatory signals of cellular and organismal PQCD pathways remains a challenge.

Identification and validation of endoplasmic reticulum stress-related genes in patients with steroid-induced osteonecrosis of the femoral head

Steroid-induced osteonecrosis of the femoral head (SONFH) is a debilitating condition caused by long-term corticosteroid use, leading to impaired blood flow and bone cell death. The disruption of cellular processes and promotion of apoptosis by endoplasmic reticulum stress (ERS) is implicated in the pathogenesis of SONFH. We identified ERS-associated genes in SONFH and investigated their potential as therapeutic targets. We analysed the GSE123568 GEO dataset to identify differentially expressed genes (DEGs) related to ERS in SONFH. We conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, identified hub genes by protein-protein interaction (PPI) analyses, and evaluated their functions by gene set enrichment analysis (GSEA). We constructed mRNA-miRNA networks, identified potential therapeutics, and assessed immune cell infiltration. We performed cross-validation using the GEO dataset GSE74089, qRT-PCR on clinical samples from patients with SONFH and controls, and a receiver operating characteristic (ROC) curve analysis to assess the diagnostic performance of the hub genes. We identified 195 ERS-related genes in SONFH, which were primarily involved in oxidative stress, immune responses, and metabolic pathways. The PPI network suggested CXCL8, STAT3, IL1B, TLR4, PTGS2, TLR2, CASP1, CYBB, CAT, and HOMX1 to be key hub genes, which were shown by GSEA to be involved in biological pathways related to metabolism, immune modulation, and cellular integrity. We also identified 261 microRNAs (miRNAs) as well as drugs such as dibenziodolium and N-acetyl-L-cysteine that modulated inflammatory responses in SONFH. Twenty-two immune cell subtypes showed significant correlations, such as a positive correlation between activated mast cells and Tregs, and patients with SONFH had fewer dendritic cells than controls. The hub genes CYBB and TLR4 showed significant correlations with M1 macrophages and CD8 T cells, respectively. Cross-validation and qRT-PCR confirmed the upregulation of STAT3, IL1B, TLR2, and CASP1 in patients with SONFH, validating the bioinformatics findings. An ROC curve analysis confirmed the diagnostic potential of the hub genes. The top 10 hub genes show promise as ERS-related diagnostic biomarkers for SONFH. We discovered that 261 miRNAs, including hsa-miR-23, influence these genes and identified potential therapeutics such as dibenziodolium and simvastatin. Immune profiling indicated altered immune functions in SONFH, with significant correlations among immune cell types. Validation confirmed the upregulation of STAT3, IL1B, TLR2 and CASP1, which had diagnostic potential. The findings suggest potential diagnostic markers and therapeutic targets for SONFH.

Epigenetic regulation of global proteostasis dynamics by RBBP5 ensures mammalian organismal health

Proteostasis is vital for cellular health, with disruptions leading to pathologies including aging, neurodegeneration and metabolic disorders. Traditionally, proteotoxic stress responses were studied as acute reactions to various noxious factors; however, recent evidence reveals that many proteostasis stress-response genes exhibit ~12-hour ultradian rhythms under physiological conditions in mammals. These rhythms, driven by an XBP1s-dependent 12h oscillator, are crucial for managing proteostasis. By exploring the chromatin landscape of the murine 12h hepatic oscillator, we identified RBBP5, a key subunit of the COMPASS complex writing H3K4me3, as an essential epigenetic regulator of proteostasis. RBBP5 is indispensable for regulating both the hepatic 12h oscillator and transcriptional response to acute proteotoxic stress, acting as a co-activator for proteostasis transcription factor XBP1s. RBBP5 ablation leads to increased sensitivity to proteotoxic stress, chronic inflammation, and hepatic steatosis in mice, along with impaired autophagy and reduced cell survival in vitro. In humans, lower RBBP5 expression is associated with reduced adaptive stress-response gene expression and hepatic steatosis. Our findings establish RBBP5 as a central regulator of proteostasis, essential for maintaining mammalian organismal health.

Krüppel-like transcription factor 14 alleviates alveolar epithelial cell senescence by inhibiting endoplasmic reticulum stress in pulmonaryfibrosis

Pulmonary fibrosis (PF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia, occurring primarily in older adults with poor prognosis. Alveolar epithelial cell (AEC) senescence is the critical pathological mechanism of PF. However, the molecular mechanisms regulating AEC senescence in PF are incompletely understood. Herein, we provided evidence to support the function of Krüppel-like factor 14 (KLF14), a novel Krüppel-like transcription factor, in the regulation of AEC senescence during PF. We confirmed that the expression of KLF14 was up-regulated in PF patients and mice treated with bleomycin (BLM). KLF14 knockdown resulted in more pronounced structural disruption of the lung tissue and swelling of the alveolar septum, which led to significantly increased mortality in BLM-induced PF mice. Mechanistically, RNA-seq analysis indicated that KLF14 decreased the senescence of AECs by inhibiting endoplasmic reticulum (ER) stress. Furthermore, the pharmacological activation of KLF14 conferred protection against PF in mice. In conclusion, our findings reveal a protective role for KLF14 in preventing AECs from senescence and shed light on the development of KLF14-targeted therapeutics for PF.

Endoplasmic reticulum stress response pathway-mediated cell death in ovarian cancer

The endoplasmic reticulum (ER) is one of the largest organelles, and Endoplasmic Reticulum Stress Response Pathway is a series of responses triggered by the homeostatic imbalance of the ER and the state in which unfolded or misfolded proteins accumulate in the ER, which can trigger cell death. Cell death plays a crucial role in the development of diseases such as gynecological oncology. Herein, we review the current research on the response and ovarian cancer, discussing the key sensors (IRE1, PERK, ATF6), and the conditions under which it occurs (Ca2+ homeostasis disruption, hypoxia, others). Using the response as a starting point, provide a comprehensive overview of the relationship with the four types of cell death (apoptosis, autophagy, immunogenic cell death, paraptosis) in an attempt to provide new targeted therapeutic strategies for the organelle-Endoplasmic Reticulum Stress Response Pathway-cell death in ovarian cancer therapy.

QRICH1 suppresses pediatric T-cell acute lymphoblastic leukemia by inhibiting GRP78

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that commonly affects children and adolescents with a poor prognosis. The terminal unfolded protein response (UPR) is an emerging anti-cancer approach, although its role in pediatric T-ALL remains unclear. In our pediatric T-ALL cohort from different centers, a lower QRICH1 expression was found associated with a worse prognosis of pediatric T-ALL. Overexpression of QRICH1 significantly inhibited cell proliferation and stimulated apoptosis of T-ALL both in vitro and in vivo. Upregulation of QRICH1 significantly downregulated 78 KDa glucose-regulated protein (GRP78) and upregulated CHOP, thus activating the terminal UPR. Co-overexpression of GRP78 in T-ALL cells overexpressing QRICH1 partially reverted the inhibited proliferation and stimulated apoptosis. QRICH1 bound to the residues Asp212 and Glu155 of the nucleotide-binding domain (NBD) of GRP78, thereby inhibiting its ATP hydrolysis activity. In addition, QRICH1 was associated with endoplasmic reticulum (ER) stress in T-ALL, and overexpression of QRICH1 reversed drug resistance. Overall, low QRICH1 expression is an independent risk factor for a poor prognosis of pediatric T-ALL. By inhibiting GRP78, QRICH1 suppresses pediatric T-ALL.