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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. Synopsis: Endoplasmic reticulum (ER) homeostasis is critical for maintaining optimal host immune responses. This study identifies UBAC2 as a phospho-regulated ER-phagy receptor that can suppress the unfolded protein response and sterile inflammation. UBAC2 is an ER resident protein that undergoes autophagic degradation upon binding GABARAP. UBAC2 promotes ER-phagy flux through its LC3-interacting region (LIR). MARK2 phosphorylates UBAC2 at serine 223, resulting in the dimerization of UBAC2 to enhance the ER-phagy process. A somatic mutation near the LIR motif of UBAC2 increases ER stress responses and sterile inflammation. Phosphorylation-induced UBAC2 dimerization facilitates binding to autophagosomal GABARAP and restrains acute ulcerative colitis via ER-phagy. [ABSTRACT FROM AUTHOR]

Loss of Lon1 led to stunted plant growth and accumulation of nuclear‐encoded mitochondrial proteins including Lon1 substrates. However, an in‐depth label‐free proteomics quantification of mitochondrial proteins in lon1 revealed that the majority of mitochondrial‐encoded proteins decreased in abundance. Additionally, we found that lon1 mutants contained protein aggregates in the mitochondrial that were enriched in metabolic enzymes, ribosomal subunits and PPR‐containing proteins of the translation apparatus. These mutants exhibited reduced general mitochondrial translation as well as deficiencies in RNA splicing and editing. These findings support the role of Lon1 in maintaining a functional translational apparatus for mitochondrial‐encoded gene translation. Transcriptome analysis of lon1 revealed a mitochondrial unfolded protein response reminiscent of the mitochondrial retrograde signalling dependent on the transcription factor ANAC017. Notably, lon1 mutants exhibited transiently elevated ethylene production, and the shortened hypocotyl observed in lon1 mutants during skotomorphogenesis was partially alleviated by ethylene inhibitors. Furthermore, the short root phenotype was partially ameliorated by introducing a mutation in the ethylene receptor ETR1. Interestingly, the upregulation of only a select few target genes was linked to ETR1‐mediated ethylene signalling. Together this provides multiple steps in the link between loss of Lon1 and signalling responses to restore mitochondrial protein homoeostasis in plants. Summary statement: Plant Lon1 prevents the aggregation of mitochondrial proteins, including metabolic enzymes and components of the translational apparatus such as ribosomal and PPR proteins. Dysfunctional proteins within these aggregates inhibit the translation of mitochondrial‐encoded genes and trigger unfolded protein responses associated with ANAC017. [ABSTRACT FROM AUTHOR]

Glioblastoma is a highly aggressive brain tumor for which there is no cure. The dire prognosis of this disease is largely attributable to a high level of heterogeneity, including the presence of a subpopulation of tumor‐initiating glioblastoma stem‐like cells (GSCs), which are refractory to chemo‐ and radiotherapy. Here, in an unbiased marine‐derived fungal extract screen, together with bioguided dereplication based on high‐resolution mass spectrometry, we identified malformin C to preferentially induce cell death in patient‐derived GSCs and explore the potential of this cyclic peptide as a therapeutic agent for glioblastoma. Malformin C significantly reduced tumor growth in an in vivo xenograft model of glioblastoma. Using transcriptomics and chemoproteomics, we found that malformin C binds to many proteins, leading to their aggregation, and rapidly induces the unfolded protein response, including autophagy, in GSCs. Crucially, chemical inhibition of translation using cycloheximide rescued malformin C‐induced cell death in GSCs, demonstrating that the proteotoxic effect of the compound is necessary for its cytotoxicity. At the same time, malformin C appears to accumulate in lysosomes, disrupting autophagic flux, and driving cells to death. Supporting this, malformin C synergizes with chloroquine, an inhibitor of autophagy. Strikingly, we observed that autophagic flux is differentially regulated in GSCs compared with normal astrocytes. The sensitivity of GSCs to malformin C highlights the relevance of proteostasis and autophagy as a therapeutic vulnerability in glioblastoma. [ABSTRACT FROM AUTHOR]

Regulating cardiolipin to maintain mitochondrial homeostasis is a promising strategy for addressing Parkinson's disease (PD). Through a comprehensive screening and validation process involving multiple models, ginsenoside Rg3 (Rg3) as a compound capable of enhancing cardiolipin levels is identified. This augmentation in cardiolipin levels fosters mitochondrial homeostasis by bolstering mitochondrial unfolded protein response, promoting mitophagy, and enhancing mitochondrial oxidative phosphorylation. Consequently, this cascade enhances the survival of tyrosine hydroxylase positive (TH+) dopaminergic neurons, leading to an amelioration in motor performance within PD mouse models. Using limited proteolysis–small‐molecule mapping combined with molecular docking analysis, it has confirmed Growth Factor Receptor‐Bound Protein 2 (GRB2) as a molecular target for Rg3. Furthermore, these investigations reveal that Rg3 facilitates the interaction between GRB2 and TRKA (Neurotrophic Tyrosine Kinase, Receptor, Type 1), thus promotes EVI1 (Ecotropic Virus Integration Site 1 Protein Homolog) phosphorylation by ERK, subsequently increases CRLS1 (Cardiolipin Synthase 1) gene expression and boosts cardiolipin synthesis. The absence of GRB2 or CRLS1 significantly attenuates the beneficial effects of Rg3 on PD symptoms. Finally, Tenofovir Disoproxil Fumarate (TDF) that also promotes the binding between GRB2 and TRKA is further identified. The identified compounds, Rg3 and TDF, exhibit promising potential for the prevention of PD by bolstering cardiolipin expression and reinstating mitochondrial homeostasis. [ABSTRACT FROM AUTHOR]

Inherited retinal diseases (IRDs) are a rare group of eye disorders characterized by progressive dysfunction and degeneration of retinal cells. In this study, we characterized the raifteirí (raf) zebrafish, a novel model of inherited blindness, identified through an unbiased ENU mutagenesis screen. A mutation in the largest subunit of the endoplasmic reticulum membrane protein complex, emc1 was subsequently identified as the causative raf mutation. We sought to elucidate the cellular and molecular phenotypes in the emc1−/− knockout model and explore the association of emc1 with retinal degeneration. Visual behavior and retinal electrophysiology assays demonstrated that emc1−/− mutants had severe visual impairments. Retinal histology and morphometric analysis revealed extensive abnormalities, including thinning of the photoreceptor layer, in addition to large gaps surrounding the lens. Notably, photoreceptor outer segments were drastically smaller, outer segment protein expression was altered and hyaloid vasculature development was disrupted. Transcriptomic profiling identified cone and rod‐specific phototransduction genes significantly downregulated by loss of emc1. These data shed light on why emc1 is a causative gene in inherited retinal disease and how outer segment morphogenesis is regulated. [ABSTRACT FROM AUTHOR]

Conserved signaling cascades monitor protein-folding homeostasis to ensure proper cellular function. One of the evolutionary conserved key players is IRE1, which maintains endoplasmic reticulum (ER) homeostasis through the unfolded protein response (UPR). Upon accumulation of misfolded proteins in the ER, IRE1 forms clusters on the ER membrane to initiate UPR signaling. What regulates IRE1 cluster formation is not fully understood. Here, we show that the ER lumenal domain (LD) of human IRE1α forms biomolecular condensates in vitro. IRE1α LD condensates were stabilized both by binding to unfolded polypeptides as well as by tethering to model membranes, suggesting their role in assembling IRE1α into signaling-competent stable clusters. Molecular dynamics simulations indicated that weak multivalent interactions drive IRE1α LD clustering. Mutagenesis experiments identified disordered regions in IRE1α LD to control its clustering in vitro and in cells. Importantly, dysregulated clustering of IRE1α mutants led to defects in IRE1α signaling. Our results revealed that disordered regions in IRE1α LD control its clustering and suggest their role as a common strategy in regulating protein assembly on membranes. Synopsis: Proteotoxic stress causes the endoplasmic reticulum (ER) stress sensor IRE1α to cluster, but the mechanistic basis of its cluster formation remains poorly understood. This study reveals that disordered regions within the protein's ER lumenal domain (LD) mediate its assembly into signaling clusters. IRE1α LD forms biomolecular condensates in solution. Disordered regions within IRE1α LD drive the formation of condensates through weak multivalent interactions. Binding of unfolded polypeptide ligands and membrane-tethering leads to the formation of stable IRE1α LD clusters. The integrity of the disordered regions in its lumenal domain is critical for IRE1α clustering and unfolded protein response (UPR) signaling in cells. The disordered regions of the ER luminal domain of IRE1α form condensates in vitro and control IRE1α clustering and stress signalling in cells. [ABSTRACT FROM AUTHOR]

Since suppressor/enhancer of Lin‐12‐like (SEL1L) was cloned in 1997, various pieces of evidence from lower species suggest it plays a significant role in protein degradation via the ubiquitin‐proteasome system. The relevance of SEL1L in many aspects of malignant transformation and tumorigenic events has been the subject of research, which has shown compelling in vitro and in vivo findings relating its altered expression to changes in tumor aggressiveness. The Endoplasmic Reticulum (ER) in tumor cells is crucial for preserving cellular proteostasis by inducing the unfolded protein response (UPR), a stress response. A crucial component of the UPR is ER‐associated degradation (ERAD), which guards against ER stress‐induced apoptosis and the removal of unfolded or misfolded proteins by the ubiquitin‐proteasome system. As a protein stabilizer of HMG‐CoA reductase degradation protein 1 (HRD1), one of the main components of ERAD, SEL1L plays an important role in ER homeostasis. Notably, the expression levels of these two proteins fluctuate independently in various cancer types, yet changes in their expression affect the levels of other associated proteins during cancer pathogenesis. Recent studies have also outlined the function of SEL1L in cancer medication resistance. This review explores the value of targeting SEL1L as a novel treatment approach for cancer, focusing on the molecular processes of SEL1L and its involvement in cancer etiology. [ABSTRACT FROM AUTHOR]

Osteoblasts and osteoclasts collaborate in bone metabolism, facilitating bone development, maintaining normal bone density and strength, and aiding in the repair of pathological damage. Endoplasmic reticulum stress (ERS) can disrupt the intracellular equilibrium between osteoclast and osteoblast, resulting in dysfunctional bone metabolism. The inositol‐requiring enzyme‐1α (IRE1α) pathway—the most conservative unfolded protein response pathway activated by ERS—is crucial in regulating cell metabolism. This involvement encompasses functions such as inflammation, autophagy, and apoptosis. Many studies have highlighted the potential roles of the IRE1α pathway in osteoblasts, chondrocytes, and osteoclasts and its implication in certain bone‐related diseases. These findings suggest that it may serve as a mediator for bone metabolism. However, relevant reviews on the role of the IRE1α pathway in bone metabolism remain unavailable. Therefore, this review aims to explore recent research that elucidated the intricate roles of the IRE1α pathway in bone metabolism, specifically in osteogenesis, chondrogenesis, osteoclastogenesis, and osteo‐immunology. The findings may provide novel insights into regulating bone metabolism and treating bone‐related diseases. [ABSTRACT FROM AUTHOR]

The glucose‐regulated protein 78 (GRP78) is pivotal in endoplasmic reticulum protein homeostasis and the unfolded protein response during cellular stress. Experimental validation has shown its role in SARS‐CoV‐2 attachment and entry. Here, the full GRP78 sequence, adding carbohydrate sugars to nucleotide‐binding domain sites, and conduct molecular dynamics simulations is modeled. Utilizing DeepPurpose virtual screening on the COCONUT database, followed by blind structure‐based screening with AutoDock Vina, top interacting binders is identified. Molecular dynamic simulations with MM/GBSA reveal stable binding of CNP0339053 and CNP0400762 to GRP78 (free energies of −43.5 ±6.7 and −34.8 ±3.9 kcal mol−1, respectively). These compounds hold promise as safe antiviral treatments for COVID‐19. [ABSTRACT FROM AUTHOR]

The transcription factor HSF‐1 (heat shock factor 1) acts as a master regulator of heat shock response in eukaryotic cells to maintain cellular proteostasis. The protein has a protective role in preventing cells from undergoing ageing, and neurodegeneration, and also mediates tumorigenesis. Thus, modulating HSF‐1 activity in humans has a promising therapeutic potential for treating these pathologies. Loss of HSF‐1 function is usually associated with impaired stress tolerance. Contrary to this conventional knowledge, we show here that inactivation of HSF‐1 in the nematode Caenorhabditis elegans results in increased thermotolerance at young adult stages, whereas HSF‐1 deficiency in animals passing early adult stages indeed leads to decreased thermotolerance, as compared to wild‐type. Furthermore, a gene expression analysis supports that in young adults, distinct cellular stress response and immunity‐related signaling pathways become induced upon HSF‐1 deficiency. We also demonstrate that increased tolerance to proteotoxic stress in HSF‐1‐depleted young worms requires the activity of the unfolded protein response of the endoplasmic reticulum and the SKN‐1/Nrf2‐mediated oxidative stress response pathway, as well as an innate immunity‐related pathway, suggesting a mutual compensatory interaction between HSF‐1 and these conserved stress response systems. A similar compensatory molecular network is likely to also operate in higher animal taxa, raising the possibility of an unexpected outcome when HSF‐1 activity is manipulated in humans. [ABSTRACT FROM AUTHOR]

Endoplasmic reticulum stress triggers the unfolded protein response (UPR) to promote cell survival or apoptosis. Transient endoplasmic reticulum stress activation has been reported to trigger megakaryocyte production, and UPR activation has been reported as a feature of megakaryocytic cancers. However, the role of UPR signaling in megakaryocyte biology is not fully understood. We studied the involvement of UPR in human megakaryocytic differentiation using PMA (phorbol 12‐myristate 13‐acetate)‐induced maturation of megakaryoblastic cell lines and thrombopoietin‐induced differentiation of human peripheral blood‐derived progenitors. Our results demonstrate that an adaptive UPR is a feature of megakaryocytic differentiation and that this response is not associated with ER stress‐induced apoptosis. Differentiation did not alter the response to the canonical endoplasmic reticulum stressors DTT or thapsigargin. However, thapsigargin, but not DTT, inhibited differentiation, consistent with the involvement of Ca2+ signaling in megakaryocyte differentiation. [ABSTRACT FROM AUTHOR]

Splicing and endoplasmic reticulum (ER)-proteostasis are two key processes that ultimately regulate the functional proteins that are produced by a cell. However, the extent to which these processes interact remains poorly understood. Here, we identify SNRPB and other components of the Sm-ring, as targets of the unfolded protein response and novel regulators of export from the ER. Mechanistically, The Sm-ring regulates the splicing of components of the ER export machinery, including Sec16A, a component of ER exit sites. Loss of function of SNRPB is causally linked to cerebro-costo-mandibular syndrome (CCMS), a genetic disease characterized by bone defects. We show that heterozygous deletion of SNRPB in mice resulted in bone defects reminiscent of CCMS and that knockdown of SNRPB delays the trafficking of type-I collagen. Silencing SNRPB inhibited osteogenesis in vitro, which could be rescued by overexpression of Sec16A. This rescue indicates that the role of SNRPB in osteogenesis is linked to its effects on ER-export. Finally, we show that SNRPB is a target for the unfolded protein response, which supports a mechanistic link between the spliceosome and ER-proteostasis. Our work highlights components of the Sm-ring as a novel node in the proteostasis network, shedding light on CCMS pathophysiology. Synopsis: RNA splicing and endoplasmic reticulum (ER) proteostasis are key to the overall control of mature protein production rates; however, the interaction between these processes is not well understood. In the following work, the spliceosome is shown to be a target of the unfolded protein response and a regulator of type-I collagen export. Silencing SNRPB and other spliceosome components alters ER export by regulating the splicing of Sec16A Loss of SNRPB results in type-I collagen trafficking defects in cell culture and osteogenesis defects in vivo SNRPB is regulated by the unfolded protein response (UPR) Our work contributes towards a better understanding of cerebro-costo-mandibular syndrome, a disease that is caused by loss of SNRPB Loss of SM-proteins alters the splicing of ER export factors which causes defects in ER-proteostasis and protein secretion. [ABSTRACT FROM AUTHOR]

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

Ischemia‐reperfusion (I‐R) injury is the most common cause of acute kidney injury. In experiments involving primary human renal proximal tubular epithelial cells (RPTECs) exposed to anoxia‐reoxygenation, we explored the hypothesis that mitochondrial malate dehydrogenase‐2 (MDH‐2) inhibition redirects malate metabolism from the mitochondria to the cytoplasm, towards the malate‐pyruvate cycle and reversed malate‐aspartate shuttle. Colorimetry, fluorometry, and western blotting showed that MDH2 inhibition accelerates the malate‐pyruvate cycle enhancing cytoplasmic NADPH, thereby regenerating the potent antioxidant reduced glutathione. It also reversed the malate‐aspartate shuttle and potentially diminished mitochondrial reactive oxygen species (ROS) production by transferring electrons, in the form of NADH, from the mitochondria to the cytoplasm. The excessive ROS production induced by anoxia‐reoxygenation led to DNA damage and protein modification, triggering DNA damage and unfolded protein response, ultimately resulting in apoptosis and senescence. Additionally, ROS induced lipid peroxidation, which may contribute to the process of ferroptosis. Inhibiting MDH‐2 proved effective in mitigating ROS overproduction during anoxia‐reoxygenation, thereby rescuing RPTECs from death or senescence. Thus, targeting MDH‐2 holds promise as a pharmaceutical strategy against I‐R injury. [ABSTRACT FROM AUTHOR]

Cancer cachexia manifests as whole body wasting, however, the precise mechanisms governing the alterations in skeletal muscle and cardiac anabolism have yet to be fully elucidated. In this study, we explored changes in anabolic processes in both skeletal and cardiac muscles in the Yoshida AH‐130 ascites hepatoma model of cancer cachexia. AH‐130 tumor‐bearing rats experienced significant losses in body weight, skeletal muscle, and heart mass. Skeletal and cardiac muscle loss was associated with decreased ribosomal (r)RNA, and hypophosphorylation of the eukaryotic factor 4E binding protein 1. Endoplasmic reticulum stress was evident by higher activating transcription factor mRNA in skeletal muscle and growth arrest and DNA damage‐inducible protein (GADD)34 mRNA in both skeletal and cardiac muscles. Tumors provoked an increase in tissue expression of interferon‐γ in the heart, while an increase in interleukin‐1β mRNA was apparent in both skeletal and cardiac muscles. We conclude that compromised skeletal muscle and heart mass in the Yoshida AH‐130 ascites hepatoma model involves a marked reduction translational capacity and efficiency. Furthermore, our observations suggest that endoplasmic reticulum stress and tissue production of pro‐inflammatory factors may play a role in the development of skeletal and cardiac muscle wasting. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is the most common age‐related neurodegenerative disorder leading to cognitive decline. Excessive cytosolic calcium (Ca2+) accumulation plays a critical role in the pathogenesis of AD since it activates the NOD‐like receptor family, pyrin domain containing 3 (NLRP3), switches the endoplasmic reticulum (ER) unfolded protein response (UPR) toward proapoptotic signaling and promotes Aβ seeding. Herein, a liposomal nanodrug (felodipine@LND) is developed incorporating a calcium channel antagonist felodipine for Alzheimer's disease treatment through a low‐intensity pulse ultrasound (LIPUS) irradiation‐assisted blood brain barrier (BBB)‐crossing drug delivery. The multifunctional felodipine@LND is effectively delivered to diseased brain through applying a LIPUS irradiation to the skull, which resulted in a series of positive effects against AD. Markedly, the nanodrug treatment switched the ER UPR toward antioxidant signaling, prevented the surface translocation of ER calreticulin (CALR) in microglia, and inhibited the NLRP3 activation and Aβ seeding. In addition, it promoted the degradation of damaged mitochondria via mitophagy, thereby inhibiting the neuronal apoptosis. Therefore, the anxiety‐like behavior and cognitive impairment of 5xFAD mice with AD is significantly ameliorated, which manifested the potential of LIPUS – assisted BBB‐crossing delivery of felodipine@LND to serve as a paradigm for AD therapy based on the well‐recognized clinically available felodipine. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Inositol‐requiring enzyme 1 (IRE1) is an endoplasmic reticulum (ER)‐resident transmembrane protein that senses ER stress and mediates an essential arm of the unfolded protein response (UPR). IRE1 reduces ER stress by upregulating the expression of multiple ER chaperones through activation of X‐box‐binding protein 1 (XBP1). Emerging lines of evidence have revealed that IRE1‐XBP1 axis serves as a multipurpose signal transducer during oncogenic transformation and cancer development. In this study, we explore how IRE1‐XBP1 signaling promotes chemoresistance in lung cancer.The expression patterns of UPR components and MRP1 were examined by Western blot. qRT‐PCR was employed to determine RNA expression. The promoter activity was determined by luciferase reporter assay. Chemoresistant cancer cells were analyzed by viability, apoptosis. CUT & Tag (Cleavage under targets and tagmentation)‐qPCR analysis was used for analysis of DNA‐protein interaction.Here we show that activation of IRE1α‐XBP1 pathway leads to an increase in MDR‐related protein 1 (MRP1) expression, which facilitates drug extrusion and confers resistance to cytotoxic chemotherapy. At the molecular level, XBP1‐induced c‐Myc is necessary for SREBP1 expression, and SREBP1 binds to the MRP1 promoter to directly regulate its transcription.We conclude that IRE1α‐XBP1 had important role in chemoresistance and appears to be a novel prognostic marker for lung cancer. [ABSTRACT FROM AUTHOR]

The impact of primary and secondary injuries of spinal cord injury (SCI) results in the demise of numerous neurons, and there is still no efficacious pharmacological intervention for it. Recently, studies have shown that endoplasmic reticulum stress (ERS) plays a pivotal role in recovery of neurological function after spinal cord injury. As a process to cope with intracellular accumulation of misfolded and unfolded proteins which triggers ERS, the unfolded protein response (UPR) plays an important role in maintaining protein homeostasis. And, a recently disclosed small molecule AA147, which selectively activates activating transcription factor 6 (ATF6), has shown promising pharmacological effects in several disease models. Thus, it seems feasible to protect the neurons after spinal cord injury by modulating UPR. In this study, primary neurons were isolated from E17‐19 C57BL/6J mouse embryos and we observed that AA147 effectively promoted the survival of neurons and alleviated neuronal apoptosis after oxygen–glucose deprivation/reoxygenation (OGD/R) in vitro. This was evident through a decrease in the proportion of PI‐positive and TUNEL‐positive cells, an increase in BCL‐2 expression, and a decrease in the expression of BAX and C‐caspase3. In in‐vivo experiments, these findings were corroborated by TUNEL staining and immunohistochemistry. It was also found that AA147 enhanced three arms of the unfolded protein response with reduced CHOP expression. Besides, AA147 mitigated the accumulation of ROS in neurons probably by upregulating catalase expression. Furthermore, spinal cord injury models of C57BL/6J mice were established and behavioral experiments revealed that AA147 facilitated the recovery of motor function following SCI. Thus, pharmacologic activation of ATF6 represents a promise therapeutic approach to ameliorate the prognosis of SCI. [ABSTRACT FROM AUTHOR]

Post‐transcriptional tRNA modifications contribute to the decoding efficiency of tRNAs by supporting codon recognition and tRNA stability. Recent work shows that the molecular and cellular functions of tRNA modifications and tRNA‐modifying‐enzymes are linked to brain development and neurological disorders. Lack of these modifications affects codon recognition and decoding rate, promoting protein aggregation and translational stress response pathways with toxic consequences to the cell. In this review, we discuss the peculiarity of local translation in neurons, suggesting a role for fine‐tuning of translation performed by tRNA modifications. We provide several examples of tRNA modifications involved in physiology and pathology of the nervous system, highlighting their effects on protein translation and discussing underlying mechanisms, like the unfolded protein response (UPR), ribosome quality control (RQC), and no‐go mRNA decay (NGD), which could affect neuronal functions. We aim to deepen the understanding of the roles of tRNA modifications and the coordination of these modifications with the protein translation machinery in the nervous system. [ABSTRACT FROM AUTHOR]

Obesity is a worldwide multifactorial disease caused by an imbalance in energy metabolism, increasing adiposity, weight gain, and promoting related diseases such as diabetes, cardiovascular diseases, neurodegeneration, and cancer. Recent findings have reported that metabolic stress related to obesity induces a mitochondrial stress response called mitochondrial unfolded protein response (UPRmt), a quality control pathway that occurs in a nuclear DNA–mitochondria crosstalk, causing transduction of chaperones and proteases under stress conditions. The duality of UPRmt signaling, with both beneficial and detrimental effects, acts in different contexts depending on the tissue, cell type, and physiological states, affecting the mitochondrial function and efficiency and the metabolism homeostasis during obesity, which remains not fully clarified. Therefore, this review discusses the most recent findings regarding UPRmt signaling during obesity, bringing an overview of UPRmt across different metabolic tissues. [ABSTRACT FROM AUTHOR]

Autophagy and endoplasmic reticulum (ER) stress are conserved processes that generally promote survival, but can induce cell death when physiological thresholds are crossed. The pro‐survival aspects of these processes are exploited by cancer cells for tumor development and progression. Therefore, anticancer drugs targeting autophagy or ER stress to induce cell death and/or block the pro‐survival aspects are being investigated extensively. Consistently, several phytochemicals have been reported to exert their anticancer effects by modulating autophagy and/or ER stress. Various phytochemicals (e.g., celastrol, curcumin, emodin, resveratrol, among others) activate the unfolded protein response to induce ER stress‐mediated apoptosis through different pathways. Similarly, various phytochemicals induce autophagy through different mechanisms (namely mechanistic target of Rapamycin [mTOR] inhibition). However, phytochemical‐induced autophagy can function either as a cytoprotective mechanism or as programmed cell death type II. Interestingly, at times, the same phytochemical (e.g., 6‐gingerol, emodin, shikonin, among others) can induce cytoprotective autophagy or programmed cell death type II depending on cellular contexts, such as cancer type. Although there is well‐documented mechanistic interplay between autophagy and ER stress, only a one‐way modulation was noted with some phytochemicals (carnosol, capsaicin, cryptotanshinone, guangsangon E, kaempferol, and δ‐tocotrienol): ER stress‐dependent autophagy. Plant extracts are sources of potent phytochemicals and while numerous phytochemicals have been investigated in preclinical and clinical studies, the search for novel phytochemicals with anticancer effects is ongoing from plant extracts used in traditional medicine (e.g., Origanum majorana). Nonetheless, the clinical translation of phytochemicals, a promising avenue for cancer therapeutics, is hindered by several limitations that need to be addressed in future studies. [ABSTRACT FROM AUTHOR]

The endoplasmic reticulum (ER) is a key organelle in eukaryotic cells, responsible for a wide range of vital functions, including the modification, folding, and trafficking of proteins, as well as the biosynthesis of lipids and the maintenance of intracellular calcium homeostasis. A variety of factors can disrupt the function of the ER, leading to the aggregation of unfolded and misfolded proteins within its confines and the induction of ER stress. A conserved cascade of signaling events known as the unfolded protein response (UPR) has evolved to relieve the burden within the ER and restore ER homeostasis. However, these processes can culminate in cell death while ER stress is sustained over an extended period and at elevated levels. This review summarizes the potential role of ER stress and the UPR in determining cell fate and function in various diseases, including cardiovascular diseases, neurodegenerative diseases, metabolic diseases, autoimmune diseases, fibrotic diseases, viral infections, and cancer. It also puts forward that the manipulation of this intricate signaling pathway may represent a novel target for drug discovery and innovative therapeutic strategies in the context of human diseases. [ABSTRACT FROM AUTHOR]

Abnormalities in alternative splicing are a hallmark of cancer formation. In this study, we investigated the role of the splicing factor PHD finger protein 5A (PHF5A) in melanoma. Malignant melanoma is the deadliest form of skin cancer, and patients with a high PHF5A expression show poor overall survival. Our data revealed that an siRNA‐mediated downregulation of PHF5A in different melanoma cell lines leads to massive splicing defects of different tumour‐relevant genes. The loss of PHF5A results in an increased rate of apoptosis by triggering Fas‐ and unfolded protein response (UPR)‐mediated apoptosis pathways in melanoma cells. These findings are tumour‐specific because we did not observe this regulation in fibroblasts. Our study identifies a crucial role of PHF5A as driver for melanoma malignancy and the described underlying splicing network provides an interesting basis for the development of new therapeutic targets for this aggressive form of skin cancer. [ABSTRACT FROM AUTHOR]

Stiffening of the brain extracellular matrix (ECM) in glioblastoma promotes tumor progression. Previously, we discovered that protein kinase R (PKR)‐like endoplasmic reticulum kinase (PERK) plays a role in glioblastoma stem cell (GSC) adaptation to matrix stiffness through PERK/FLNA‐dependent F‐actin remodeling. Here, we examined the involvement of PERK in detecting stiffness changes via focal adhesion complex (FAC) formation. Compared to control GSCs, PERK‐deficient GSCs show decreased vinculin and tensin expression, while talin and integrin‐β1 remain constant. Furthermore, vimentin was also reduced while tubulin increased, and a stiffness‐dependent increase of the differentiation marker GFAP expression was absent in PERK‐deficient GSCs. In conclusion, our study reveals a novel role for PERK in FAC formation during matrix stiffening, which is likely linked to its regulation of F‐actin remodeling. [ABSTRACT FROM AUTHOR]

Summary: IRE1, BI‐1, and bZIP60 monitor compatible plant–potexvirus interactions though recognition of the viral TGB3 protein. This study was undertaken to elucidate the roles of three IRE1 isoforms, the bZIP60U and bZIP60S, and BI‐1 roles in genetic reprogramming of cells during potexvirus infection.Experiments were performed using Arabidopsis thaliana knockout lines and Plantago asiatica mosaic virus infectious clone tagged with the green fluorescent protein gene (PlAMV‐GFP).There were more PlAMV‐GFP infection foci in ire1a/b, ire1c, bzip60, and bi‐1 knockout than wild‐type (WT) plants. Cell‐to‐cell movement and systemic RNA levels were greater bzip60 and bi‐1 than in WT plants. Overall, these data indicate an increased susceptibility to virus infection. Transgenic overexpression of AtIRE1b or StbZIP60 in ire1a/b or bzip60 mutant background reduced virus infection foci, while StbZIP60 expression influences virus movement. Transgenic overexpression of StbZIP60 also confers endoplasmic reticulum (ER) stress resistance following tunicamycin treatment. We also show bZIP60U and TGB3 interact at the ER.This is the first demonstration of a potato bZIP transcription factor complementing genetic defects in Arabidopsis. Evidence indicates that the three IRE1 isoforms regulate the initial stages of virus replication and gene expression, while bZIP60 and BI‐1 contribute separately to virus cell‐to‐cell and systemic movement. [ABSTRACT FROM AUTHOR]

Chemotherapy is a common and effective treatment for cancer, but these drugs are also associated with significant side effects affecting patients' well‐being. One such debilitating side effect is mucositis, characterized by inflammation, ulcerations, and altered physiological functions of the gastrointestinal (GI) tract's mucosal lining. Understanding the mechanisms of chemotherapy‐induced intestinal mucositis (CIM) is crucial for developing effective preventive measures and supportive care. Chemotherapeutics not only target cancer cells but also rapidly dividing cells in the GI tract. These drugs disrupt endoplasmic reticulum (ER) homeostasis, leading to ER‐stress and activation of the unfolded protein response (UPR) in various intestinal epithelial cell types. The UPR triggers signaling pathways that exacerbate tissue inflammation and damage, influence the differentiation and fate of intestinal epithelial cells, and compromise the integrity of the intestinal mucosal barrier. These factors contribute significantly to mucositis development and progression. In this review, we aim to give an in‐depth overview of the role of ER‐stress in mucositis and its impact on GI function. This will provide valuable insights into the underlying mechanisms and highlighting potential therapeutic interventions that could improve treatment‐outcomes and the quality of life of cancer patients. [ABSTRACT FROM AUTHOR]

Aim: Calcineurin inhibitors (CNIs) are the backbone for immunosuppression after solid organ transplantation. Although successful in preventing kidney transplant rejection, their nephrotoxic side effects contribute to allograft injury. Renal parenchymal lesions occur for cyclosporine A (CsA) as well as for the currently favored tacrolimus (Tac). We aimed to study whether chronic CsA and Tac exposures, before reaching irreversible nephrotoxic damage, affect renal compartments differentially and whether related pathogenic mechanisms can be identified. Methods: CsA and Tac were administered chronically in wild type Wistar rats using osmotic minipumps over 4 weeks. Functional parameters were controlled. Electron microscopy, confocal, and 3D‐structured illumination microscopy were used for histopathology. Clinical translatability was tested in human renal biopsies. Standard biochemical, RNA‐seq, and proteomic technologies were applied to identify implicated molecular pathways. Results: Both drugs caused significant albeit differential damage in vasculature and nephron. The glomerular filtration barrier was more affected by Tac than by CsA, showing prominent deteriorations in endothelium and podocytes along with impaired VEGF/VEGFR2 signaling and podocyte‐specific gene expression. By contrast, proximal tubule epithelia were more severely affected by CsA than by Tac, revealing lysosomal dysfunction, enhanced apoptosis, impaired proteostasis and oxidative stress. Lesion characteristics were confirmed in human renal biopsies. Conclusion: We conclude that pathogenetic alterations in the renal compartments are specific for either treatment. Considering translation to the clinical setting, CNI choice should reflect individual risk factors for renal vasculature and tubular epithelia. As a step in this direction, we share protein signatures identified from multiomics with potential pathognomonic relevance. [ABSTRACT FROM AUTHOR]

Senescence in bone marrow mesenchymal stem cells (BMSCs), triggered by excessive oxidative stress, plays a crucial role in the onset of postmenopausal osteoporosis. Recent studies underscore the importance of mitochondrial rehabilitation and quality control as key determinants in the modulation of oxidative stress and cellular senescence. MitoTEMPO, a mitochondria‐targeted antioxidant, has been shown to mitigate the heightened levels of reactive oxygen species (ROS). In our research, we observed that BMSCs from ovariectomized (OVX) rats displayed premature senescence, which was attributed to combined mitochondrial and lysosomal dysfunction, a condition that worsens with extended estrogen deprivation. Treatment with MitoTEMPO effectively reversed these effects, reinstating lysosomal functionality and suppressing the mitochondrial unfolded protein response (UPRmt). Subsequent in vivo experiments corroborated these observations, revealing that MitoTEMPO administration in OVX rats curtailed trabecular bone loss and reduced the expression of p53, HSP60, and CLPP in the trabecular bone region of the proximal tibia. Overall, our findings suggest that MitoTEMPO holds promise as a therapeutic agent to counteract senescence in OVX‐BMSCs, offering a potential strategy for treating postmenopausal osteoporosis. [ABSTRACT FROM AUTHOR]

Aims: Endoplasmic reticulum stress followed by the unfolded protein response is one of the cellular mechanisms contributing to the progression of α‐synuclein pathology in Parkinson's disease and other Lewy body diseases. We aimed to investigate the activation of endoplasmic reticulum stress and its correlation with α‐synuclein pathology in human post‐mortem brain tissue. Methods: We analysed brain tissue from 45 subjects—14 symptomatic patients with Lewy body disease, 19 subjects with incidental Lewy body disease, and 12 healthy controls. The analysed brain regions included the medulla, pons, midbrain, striatum, amygdala and entorhinal, temporal, frontal and occipital cortex. We analysed activation of endoplasmic reticulum stress via levels of the unfolded protein response‐related proteins (Grp78, eIF2α) and endoplasmic reticulum stress‐regulating neurotrophic factors (MANF, CDNF). Results: We showed that regional levels of two endoplasmic reticulum‐localised neurotrophic factors, MANF and CDNF, did not change in response to accumulating α‐synuclein pathology. The concentration of MANF negatively correlated with age in specific regions. eIF2α was upregulated in the striatum of Lewy body disease patients and correlated with increased α‐synuclein levels. We found the upregulation of chaperone Grp78 in the amygdala and nigral dopaminergic neurons of Lewy body disease patients. Grp78 levels in the amygdala strongly correlated with soluble α‐synuclein levels. Conclusions: Our data suggest a strong but regionally specific change in Grp78 and eIF2α levels, which positively correlates with soluble α‐synuclein levels. Additionally, MANF levels decreased in dopaminergic neurons in the substantia nigra. Our research suggests that endoplasmic reticulum stress activation is not associated with Lewy pathology but rather with soluble α‐synuclein concentration and disease progression. [ABSTRACT FROM AUTHOR]

Background: The induction of mitochondrial quality control (MQC) mechanisms is essential for the re‐establishment of mitochondrial homeostasis and cellular bioenergetics during periods of stress. Although MQC activation has cardioprotective effects in various cardiovascular diseases, its precise role and regulatory mechanisms in alcoholic cardiomyopathy (ACM) remain incompletely understood. Methods: We explored whether two mitochondria‐related proteins, phosphoglycerate mutase 5 (Pgam5) and prohibitin 2 (Phb2), influence MQC in male mice during ACM. Results: Myocardial Pgam5 expression was upregulated in a male mouse model of ACM. Notably, following ACM induction, heart dysfunction was markedly reversed in male cardiomyocyte‐specific Pgam5 knockout (Pgam5cKO) mice. Meanwhile, in alcohol‐treated male mouse‐derived neonatal cardiomyocytes, Pgam5 depletion preserved cell survival and restored mitochondrial dynamics, mitophagy, mitochondrial biogenesis and the mitochondrial unfolded protein response (mtUPR). We further found that in alcohol‐treated cardiomyocyte, Pgam5 binds Phb2 and induces its dephosphorylation at Ser91. Alternative transduction of phospho‐mimetic (Phb2S91D) and phospho‐defective (Phb2S9A) Phb2 mutants attenuated and enhanced, respectively, alcohol‐related mitochondrial dysfunction in cardiomyocytes. Moreover, transgenic male mice expressing Phb2S91D were resistant to alcohol‐induced heart dysfunction. Conclusions: We conclude that ACM‐induced Pgam5 upregulation results in Pgam5‐dependent Phb2S91 dephosphorylation, leading to MQC destabilisation and mitochondrial dysfunction in heart. Therefore, modulating the Pgam5/Phb2 interaction could potentially offer a novel therapeutic strategy for ACM in male mice. Highlights: Pgam5 knockout attenuates alcohol‐induced cardiac histopathology and heart dysfunction in male mice.Pgam5 KO reduces alcohol‐induced myocardial inflammation, lipid peroxidation and metabolic dysfunction in male mice.Pgam5 depletion protects mitochondrial function in alcohol‐exposed male mouse cardiomyocytes.Pgam5 depletion normalises MQC in ACM.EtOH impairs MQC through inducing Phb2 dephosphorylation at Ser91.Pgam5 interacts with Phb2 and induces Phb2 dephosphorylation.Transgenic mice expressing a Ser91 phospho‐mimetic Phb2 mutant are resistant to ACM. [ABSTRACT FROM AUTHOR]

Lipid metabolism hinges on a balance between lipogenesis and fatty acid oxidation (FAO). Disruptions in this balance can induce endoplasmic reticulum (ER) stress triggering the unfolded protein response (UPR) and contribute to metabolic diseases. The UPR protein, Luman or CREB3, has recently been implicated in metabolic regulation–CREB3 knockout mice exhibit resistance to diet‐induced obesity and altered insulin sensitivity. Here, we show that CREB3 activated PPARGC1A transcription from a 1 kb promoter region. An increase in CREB3 expression correlated inversely with endogenous PPARGC1A mRNA levels and genes involved in FAO. As PGC‐1α encoded by PPARGC1A is a master regulator of mitochondrial biogenesis and energy homeostasis, these findings demonstrate that CREB3 is a transcriptional regulator of PGC‐1α, underlining the potential role of CREB3 in energy metabolism. [ABSTRACT FROM AUTHOR]

This document provides information about a study on the effectiveness of ruxolitinib cream in treating vitiligo, a chronic autoimmune disease that causes depigmentation on the skin. The study found that repigmentation varied across different body regions, with the face, trunk, and proximal extremities showing better response than bony prominences, hands, and feet. Patients treated with ruxolitinib cream showed improvement in repigmentation over a 52-week period, with the head/neck and trunk responding the best. However, repigmentation of the hands and feet was more challenging. The study suggests that longer-term treatment and combination therapies may be helpful for achieving optimal repigmentation in difficult-to-treat areas. The document also provides information about the authors and their affiliations, as well as potential conflicts of interest. It includes a statement about data availability and an ethics statement regarding the trials conducted. [Extracted from the article]

Endoplasmic reticulum (ER) stress, which ensues from an overwhelming protein folding capacity, activates the unfolded protein response (UPR) in an effort to restore cellular homeostasis. As ER stress is associated with numerous diseases, it is highly important to delineate the molecular mechanisms governing the ER stress to gain insight into the disease pathology. Long non‐coding RNAs, transcripts with a length of over 200 nucleotides that do not code for proteins, interact with proteins and nucleic acids, fine‐tuning the UPR to restore ER homeostasis via various modes of actions. Dysregulation of specific lncRNAs is implicated in the progression of ER stress‐related diseases, presenting these molecules as promising therapeutic targets. The comprehensive analysis underscores the importance of understanding the nuanced interplay between lncRNAs and ER stress for insights into disease mechanisms. Overall, this review consolidates current knowledge, identifies research gaps and offers a roadmap for future investigations into the multifaceted roles of lncRNAs in ER stress and associated diseases to shed light on their pivotal roles in the pathogenesis of related diseases. [ABSTRACT FROM AUTHOR]

Marine sponges are predicted to be winners in the future ocean due to their exemplary adaptive capacity. However, while many sponge groups exhibit tolerance to a wide range of environmental insults, calcifying sponges may be more susceptible to thermo‐acidic stress. To describe the gene regulatory networks that govern the stress response of the calcareous sponge, Leucetta chagosensis (class Calcarea, order Clathrinida), individuals were subjected to warming and acidification conditions based on the climate models for 2100. Transcriptome analysis and gene co‐expression network reconstruction revealed that the unfolded protein response (UPR) was activated under thermo‐acidic stress. Among the upregulated genes were two lineage‐specific homologs of X‐box binding protein 1 (XBP1), a transcription factor that activates the UPR. Alternative dimerization between these XBP1 gene products suggests a clathrinid‐specific mechanism to reversibly sequester the transcription factor into an inactive form, enabling the rapid regulation of pathways linked to the UPR in clathrinid calcareous sponges. Our findings support the idea that transcription factor duplication events may refine evolutionarily conserved molecular pathways and contribute to ecological success. [ABSTRACT FROM AUTHOR]

The disruption of mitochondria‐associated endoplasmic reticulum (ER) membranes (MAMs) plays a relevant role in Alzheimer's disease (AD). MAMs have been implicated in neuronal dysfunction and death since it is associated with impairment of functions regulated in this subcellular domain, including lipid synthesis and trafficking, mitochondria dysfunction, ER stress‐induced unfolded protein response (UPR), apoptosis, and inflammation. Since MAMs play an important role in lipid metabolism, in this study we characterized and investigated the lipidome alterations at MAMs in comparison with other subcellular fractions, namely microsomes and mitochondria, using an in vitro model of AD, namely the mouse neuroblastoma cell line (N2A) over‐expressing the APP familial Swedish mutation (APPswe) and the respective control (WT) cells. Phospholipids (PLs) and fatty acids (FAs) were isolated from the different subcellular fractions and analyzed by HILIC‐LC–MS/MS and GC–MS, respectively. In this in vitro AD model, we observed a down‐regulation in relative abundance of some phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and lysophosphatidylethanolamine (LPE) species with PUFA and few PC with saturated and long‐chain FA. We also found an up‐regulation of CL, and antioxidant alkyl acyl PL. Moreover, multivariate analysis indicated that each organelle has a specific lipid profile adaptation in N2A APPswe cells. In the FAs profile, we found an up‐regulation of C16:0 in all subcellular fractions, a decrease of C18:0 levels in total fraction (TF) and microsomes fraction, and a down‐regulation of 9‐C18:1 was also found in mitochondria fraction in the AD model. Together, these results suggest that the over‐expression of the familial APP Swedish mutation affects lipid homeostasis in MAMs and other subcellular fractions and supports the important role of lipids in AD physiopathology. [ABSTRACT FROM AUTHOR]

Vicinal oxygen chelate (VOC) proteins are members of an enzyme superfamily with dioxygenase or non‐dioxygenase activities. However, the biological functions of VOC proteins in plants are poorly understood. Here, we show that a VOC in Nicotiana benthamiana (NbVOC1) facilitates viral infection. NbVOC1 was significantly induced by infection by beet necrotic yellow vein virus (BNYVV). Transient overexpression of NbVOC1 or its homolog from Beta vulgaris (BvVOC1) enhanced BNYVV infection in N. benthamiana, which required the nuclear localization of VOC1. Consistent with this result, overexpressing NbVOC1 facilitated BNYVV infection, whereas, knockdown and knockout of NbVOC1 inhibited BNYVV infection in transgenic N. benthamiana plants. NbVOC1 interacts with the basic leucine zipper transcription factors bZIP17/28, which enhances their self‐interaction and DNA binding to the promoters of unfolded protein response (UPR)‐related genes. We propose that bZIP17/28 directly binds to the NbVOC1 promoter and induces its transcription, forming a positive feedback loop to induce the UPR and facilitating BNYVV infection. Collectively, our results demonstrate that NbVOC1 positively regulates the UPR that enhances viral infection in plants. [ABSTRACT FROM AUTHOR]

Background: The role of the unfolded protein response (UPR) has been progressively unveiled over the last decade and several studies have investigated its implication in glioblastoma (GB) development. The UPR restores cellular homeostasis by triggering the folding and clearance of accumulated misfolded proteins in the ER consecutive to endoplasmic reticulum stress. In case it is overwhelmed, it induces apoptotic cell death. Thus, holding a critical role in cell fate decisions. Methods: This article, reviews how the UPR is implicated in cell homeostasis maintenance, then surveils the evidence supporting the UPR involvement in GB genesis, progression, angiogenesis, GB stem cell biology, tumor microenvironment modulation, extracellular matrix remodeling, cell fate decision, invasiveness, and grading. Next, it concurs the evidence showing how the UPR mediates GB chemoresistance‐related mechanisms. Results: The UPR stress sensors IRE1, PERK, and ATF6 with their regulator GRP78 are upregulated in GB compared to lower grade gliomas and normal brain tissue. They are activated in response to oncogenes and are implicated at different stages of GB progression, from its genesis to chemoresistance and relapse. The UPR arms can be effectors of apoptosis as mediators or targets. Conclusion: Recent research has established the role of the UPR in GB pathophysiology and chemoresistance. Targeting its different sensors have shown promising in overcoming GB chomo‐ and radioresistance and inducing apoptosis. [ABSTRACT FROM AUTHOR]

The pursuit of enhanced health during aging has prompted the exploration of various strategies focused on reducing the decline associated with the aging process. A key area of this exploration is the management of mitochondrial dysfunction, a notable characteristic of aging. This review sheds light on the crucial role that small molecules play in augmenting healthy aging, particularly through influencing mitochondrial functions. Mitochondrial oxidative damage, a significant aspect of aging, can potentially be lessened through interventions such as coenzyme Q10, alpha‐lipoic acid, and a variety of antioxidants. Additionally, this review discusses approaches for enhancing mitochondrial proteostasis, emphasizing the importance of mitochondrial unfolded protein response inducers like doxycycline, and agents that affect mitophagy, such as urolithin A, spermidine, trehalose, and taurine, which are vital for sustaining protein quality control. Of equal importance are methods for modulating mitochondrial energy production, which involve nicotinamide adenine dinucleotide boosters, adenosine 5′‐monophosphate‐activated protein kinase activators, and compounds like metformin and mitochondria‐targeted tamoxifen that enhance metabolic function. Furthermore, the review delves into emerging strategies that encourage mitochondrial biogenesis. Together, these interventions present a promising avenue for addressing age‐related mitochondrial degradation, thereby setting the stage for the development of innovative treatment approaches to meet this extensive challenge. [ABSTRACT FROM AUTHOR]

Pancreatic β‐cell mass is a critical determinant of insulin secretion. Severe endoplasmic reticulum (ER) stress causes β‐cell apoptosis; however, the mechanisms of progression and suppression are not yet fully understood. Here, we report that the autocrine/paracrine function of insulin reduces ER stress‐induced β‐cell apoptosis. Insulin reduced the ER‐stress inducer tunicamycin‐ and thapsigargin‐induced cell viability loss due to apoptosis in INS‐1 β‐cells. Moreover, the effect of insulin was greater than that of insulin‐like growth factor‐1 at physiologically relevant concentrations. Insulin did not attenuate the ER stress‐induced increase in unfolded protein response genes. ER stress did not induce cytochrome c release from mitochondria. Mitochondrial hyperpolarization was induced by ER stress and prevented by insulin. The protonophore/mitochondrial oxidative phosphorylation uncoupler, but not the antioxidants N‐acetylcysteine and α‐tocopherol, exhibited potential cytoprotection during ER stress. Both procaspase‐12 and cleaved caspase‐12 levels increased under ER stress. The caspase‐12 inhibitor Z‐ATAD‐FMK decreased ER stress‐induced apoptosis. Caspase‐12 overexpression reduced cell viability, which was diminished in the presence of insulin. Insulin decreased caspase‐12 levels at the post‐translational stages. These results demonstrate that insulin protects against ER stress‐induced β‐cell apoptosis in this cell line. Furthermore, mitochondrial hyperpolarization and increased caspase‐12 levels are involved in ER stress‐induced and insulin‐suppressed β‐cell apoptosis. [ABSTRACT FROM AUTHOR]

Quality‐based protein production and degradation in the endoplasmic reticulum (ER) are essential for eukaryotic cell survival. During protein maturation in the ER, misfolded or unassembled proteins are destined for disposal through a process known as ER‐associated degradation (ERAD). EDEM1 is an ERAD‐accelerating factor whose gene expression is upregulated by the accumulation of aberrant proteins in the ER, known as ER stress. Although the role of EDEM1 in ERAD has been studied in detail, the turnover of EDEM1 by intracellular degradation machinery, including the proteasome and autophagy, is not well understood. To clarify EDEM1 regulation in the protein level, degradation mechanism of EDEM1 was examined. Our results indicate that both ERAD and autophagy degrade EDEM1 alike misfolded degradation substrates, although each degradation machinery targets EDEM1 in different folded states of proteins. We also found that ERAD factors, including the SEL1L/Hrd1 complex, YOD1, XTP3B, ERdj3, VIMP, BAG6, and JB12, but not OS9, are involved in EDEM1 degradation in a mannose‐trimming‐dependent and ‐independent manner. Our results suggest that the ERAD accelerating factor, EDEM1, is turned over by the ERAD itself, similar to ERAD clients. [ABSTRACT FROM AUTHOR]

Background: Glucose overload drives diabetic cardiomyopathy by affecting the tricarboxylic acid pathway. However, it is still unknown how cells could overcome massive chronic glucose influx on cellular and structural level. Methods/Materials: Expression profiles of hyperglycemic, glucose transporter‐4 (GLUT4) overexpressing H9C2 (KE2) cardiomyoblasts loaded with 30 mM glucose (KE230L) and wild type (WT) cardiomyoblasts loaded with 30 mM glucose (WT30L) were compared using proteomics, real‐time polymerase quantitative chain reaction analysis, or Western blotting, and immunocytochemistry. Results: The findings suggest that hyperglycemic insulin‐sensitive cells at the onset of diabetic cardiomyopathy present complex changes in levels of structural cell‐related proteins like tissue inhibitor of metalloproteases‐1 (1.3 fold), intercellular adhesion molecule 1 (1.8 fold), type‐IV‐collagen (3.2 fold), chaperones (Glucose‐Regulated Protein 78: 1.8 fold), autophagy (Autophagosome Proteins LC3A, LC3B: 1.3 fold), and in unfolded protein response (UPR; activating transcription factor 6α expression: 2.3 fold and processing: 2.4 fold). Increased f‐actin levels were detectable with glucose overload by immnocytochemistry. Effects on energy balance (1.6 fold), sirtuin expression profile (Sirtuin 1: 0.7 fold, sirtuin 3: 1.9 fold, and sirtuin 6: 4.2 fold), and antioxidant enzymes (Catalase: 0.8 fold and Superoxide dismutase 2: 1.5 fold) were detected. Conclusion: In conclusion, these findings implicate induction of chronic cell distress by sustained glucose accumulation with a non‐compensatory repair reaction not preventing final cell death. This might explain the chronic long lasting pathogenesis observed in developing heart failure in diabetes mellitus. [ABSTRACT FROM AUTHOR]

Summary: The unfolded protein response (UPR) allows cells to cope with endoplasmic reticulum (ER) stress induced by accumulation of misfolded proteins in the ER. Due to its sensitivity to Agrobacterium tumefaciens, the model plant Nicotiana benthamiana is widely employed for transient expression of recombinant proteins of biopharmaceutical interest, including antibodies and virus surface proteins used for vaccine production. As such, study of the plant UPR is of practical significance, since enforced expression of complex secreted proteins often results in ER stress. After 6 days of expression, we recently reported that influenza haemagglutinin H5 induces accumulation of UPR proteins. Since up‐regulation of corresponding UPR genes was not detected at this time, accumulation of UPR proteins was hypothesized to be independent of transcriptional induction, or associated with early but transient UPR gene up‐regulation. Using time course sampling, we here show that H5 expression does result in early and transient activation of the UPR, as inferred from unconventional splicing of NbbZIP60 transcripts and induction of UPR genes with varied functions. Transient nature of H5‐induced UPR suggests that this response was sufficient to cope with ER stress provoked by expression of the secreted protein, as opposed to an antibody that triggered stronger and more sustained UPR activation. As up‐regulation of defence genes responding to H5 expression was detected after the peak of UPR activation and correlated with high increase in H5 protein accumulation, we hypothesize that these immune responses, rather than the UPR, were responsible for onset of the necrotic symptoms on H5‐expressing leaves. [ABSTRACT FROM AUTHOR]

As no study about the combined effect of low levels of Cd2+ with procymidone (PCM) on organs and organisms, we investigated their actions on mouse‐ovary in vivo and in vitro. Four‐week mice were treated with corn oil for the control group, corn oil + 0.0045 mg/L Cd2+ (CdCl2 was dissolved in ultrapure water and freely consumed by mice) for Cd2+ group, 50 mg/kg/d PCM (suspended in corn oil and administered orally to mice) for PCM group, and 50 mg/kg/d PCM + 0.0015 (0.0045 and 0.0135) mg/L Cd2+ for L+ (M+ and H+) PCM group for 21 days. For in vitro experiment, the cultured ovaries were treated with acetone for the control group, 0.1% acetone + 8.4 μg/L Cd2+ for the Cd2+ group, 0.63 mg/L PCM (dissolved in acetone) for the PCM‐group, and 0.63 mg/L PCM + 2.8 (8.4 and 25.2) μg/L Cd2+ for L+ (M+ and H+) PCM group for 7 days. Mouse body weight in each treatment group, the weight and volume of ovaries in all PCM groups were lower than the control. Both in vivo and in vitro, all‐stage follicle numbers were lower in M+PCM and H+PCM groups, whereas the atretic follicles and CASPASE3/8 were higher; meanwhile, lower estradiol and progesterone and higher unfolded protein response (UPR) members in all PCM groups. L+, M+, and H+PCM groups had further ovarian damage and stronger UPR than PCM groups, as did M+PCM groups over Cd2+ groups. It is hypothesized low‐level PCM and Cd2+ may mutually promote each other's triggered UPR and exacerbate ovarian damage. [ABSTRACT FROM AUTHOR]

Biological membranes have a stunning ability to adapt their composition in response to physiological stress and metabolic challenges. Little is known how such perturbations affect individual organelles in eukaryotic cells. Pioneering work has provided insights into the subcellular distribution of lipids in the yeast Saccharomyces cerevisiae, but the composition of the endoplasmic reticulum (ER) membrane, which also crucially regulates lipid metabolism and the unfolded protein response, remains insufficiently characterized. Here, we describe a method for purifying organelle membranes from yeast, MemPrep. We demonstrate the purity of our ER membrane preparations by proteomics, and document the general utility of MemPrep by isolating vacuolar membranes. Quantitative lipidomics establishes the lipid composition of the ER and the vacuolar membrane. Our findings provide a baseline for studying membrane protein biogenesis and have important implications for understanding the role of lipids in regulating the unfolded protein response (UPR). The combined preparative and analytical MemPrep approach uncovers dynamic remodeling of ER membranes in stressed cells and establishes distinct molecular fingerprints of lipid bilayer stress. Synopsis: This study describes a new technology for isolating organelle membranes from yeast, MemPrep. Combined with quantitative lipidomics, MemPrep establishes molecular fingerprints of membrane-based forms of endoplasmic reticulum (ER) stress. MemPrep provides quantitative insight into the compositions of the yeast vacuole and ER membrane. The ER membrane composition is significantly distinct from the whole cell lipidome. Lipid metabolic perturbation causes dramatic changes of the ER membrane composition, which sometimes trigger ER stress. Inositol depletion and prolonged proteotoxic stress lead to distinct lipid fingerprints and membrane proteomes. Increased membrane thickness and low levels of anionic lipids are common denominators of lipid bilayer stress. Combined with proteomics and quantitative lipidomics, this method for purification of specific yeast membranes establishes molecular fingerprints of membrane-based forms of endoplasmic reticulum (ER) stress. [ABSTRACT FROM AUTHOR]

Signalling by the Unfolded Protein Response (UPR) or by the Death Receptors (DR) are frequently activated towards pro-tumoral outputs in cancer. Herein, we demonstrate that the UPR sensor IRE1 controls the expression of the DR CD95/Fas, and its cell death-inducing ability. Both genetic and pharmacologic blunting of IRE1 activity increased CD95 expression and exacerbated CD95L-induced cell death in glioblastoma (GB) and Triple-Negative Breast Cancer (TNBC) cell lines. In accordance, CD95 mRNA was identified as a target of Regulated IRE1-Dependent Decay of RNA (RIDD). Whilst CD95 expression is elevated in TNBC and GB human tumours exhibiting low RIDD activity, it is surprisingly lower in XBP1s-low human tumour samples. We show that IRE1 RNase inhibition limited CD95 expression and reduced CD95-mediated hepatic toxicity in mice. In addition, overexpression of XBP1s increased CD95 expression and sensitized GB and TNBC cells to CD95L-induced cell death. Overall, these results demonstrate the tight IRE1-mediated control of CD95-dependent cell death in a dual manner through both RIDD and XBP1s, and they identify a novel link between IRE1 and CD95 signalling. Synopsis: Dual regulation of Cell Death Receptor CD95 signalling by ER stress sensor IRE1. IRE1, a mediator of the unfolded protein response (UPR), governs CD95/Fas expression and CD95L-induced cell death in opposing ways. IRE1 can induce CD95 expression to promote CD95L-induced cell death via the transcription factor XBP1s in triple-negative breast cancer (TNBC) and glioblastoma (GB) cells. IRE1 can also repress CD95 expression to limit CD95L-induced cell death through RIDD activity, which cleaves CD95 mRNA in both TNBC and GB cells. The net effect of these opposing mechanisms depends on the cellular context. IRE1 controls CD95 signalling in vivo. Activation of RIDD or XBP1s downstream of IRE1 dually correlates with CD95 mRNA expression in human TNBC and GB tumours. Dual regulation of Cell Death Receptor CD95 signaling by ER stress sensor IRE1. IRE1, a mediator of the unfolded protein response (UPR), governs CD95/Fas expression and CD95L-induced cell death in opposing ways. [ABSTRACT FROM AUTHOR]

S‐adenosylmethionine (SAM), generated from methionine and ATP by S‐adenosyl methionine synthetase (SAMS), is the universal methyl group donor required for numerous cellular methylation reactions. In Caenorhabditis elegans, silencing sams‐1, the major isoform of SAMS, genetically or via dietary restriction induces a robust mitochondrial unfolded protein response (UPRmt) and lifespan extension. In this study, we found that depleting SAMS‐1 markedly decreases mitochondrial SAM levels. Moreover, RNAi knockdown of SLC‐25A26, a carrier protein responsible for transporting SAM from the cytoplasm into the mitochondria, significantly lowers the mitochondrial SAM levels and activates UPRmt, suggesting that the UPRmt induced by sams‐1 mutations might result from disrupted mitochondrial SAM homeostasis. Through a genetic screen, we then identified a putative mitochondrial tRNA methyltransferase TRMT‐10C.2 as a major downstream effector of SAMS‐1 to regulate UPRmt and longevity. As disruption of mitochondrial tRNA methylation likely leads to impaired mitochondrial tRNA maturation and consequently reduced mitochondrial translation, our findings suggest that depleting mitochondrial SAM level might trigger UPRmt via attenuating protein translation in the mitochondria. Together, this study has revealed a potential mechanism by which SAMS‐1 regulates UPRmt and longevity. [ABSTRACT FROM AUTHOR]

Canine demodicosis is a prevalent skin disease caused by overpopulation of a commensal species of Demodex mite, yet its precise cause remains unknown. Research suggests that T‐cell exhaustion, increased immunosuppressive cytokines, induction of regulatory T cells and increased expression of immune checkpoint inhibitors may contribute to its pathogenesis. This study aimed to gain a deeper understanding of the molecular changes occurring in canine demodicosis using mass spectrometry and pathway enrichment analysis. The results indicate that endoplasmic reticulum stress promotes canine demodicosis through regulation of three linked signalling pathways: eIF2, mTOR, and eIF4 and p70S6K. These pathways are involved in the modulation of Toll‐like receptors, most notably TLR2, and have been shown to play a role in the pathogenesis of skin diseases in both dogs and humans. Moreover, these pathways are also implicated in the promotion of immunosuppressive M2 phenotype macrophages. Immunohistochemical analysis, utilising common markers of dendritic cells and macrophages, verified the presence of M2 macrophages in canine demodicosis. The proteomic analysis also identified immunological disease, organismal injury and abnormalities and inflammatory response as the most significant underlying diseases and disorders associated with canine demodicosis. This study demonstrates that Demodex mites, through ER stress, unfolded protein response and M2 macrophages contribute to an immunosuppressive microenvironment, thereby assisting in their proliferation. [ABSTRACT FROM AUTHOR]

Background: Adenoid tissue is a first‐line host defense secondary lymphoid organ, especially in childhood. The endoplasmic reticulum (ER) is required to maintain balanced cellular activity. With impaired ER functions, protein accumulation occurs, resulting in ER stress, which plays a role in the etiopathogenesis of many diseases. Objective: We aimed to investigate the relationship between ER stress and adenoid tissue disorders, thereby elucidating the mechanisms of immunity‐related diseases. Methods: Fifty‐four pediatric patients (>3 years old) who underwent adenoidectomy for chronic adenoiditis (CA) or adenoid hypertrophy (AH) were enrolled in this prospective, parallel‐group clinical study. Adenoids were divided into two groups (CA or AH) based on their size and evaluated for ER stress pathway and apoptosis pathway markers by Real‐time PCR and Western blot analysis. Results: ER stress pathway markers significantly differed between the CA and AH groups. Children with CA had higher ER stress marker levels than the AH group (p <.001 for ATF‐4, ATF‐6, and GRP78, and p <.05 for EDEM1, CHOP, EIF2AK3, ERNI, and GRP94). Apoptosis pathway marker levels (BAX and BCL‐2) were not different between groups. Conclusions: ER stress contributes to the etiopathogenesis of adenoid tissue diseases and the pathogenesis of adenoid tissue disorders, which are part of the immune response. These results may guide the development of new and alternative treatments for immune system disorders. [ABSTRACT FROM AUTHOR]

The lower respiratory system serves as the target and barrier for beta‐coronavirus (beta‐CoV) infections. In this study, we explored beta‐CoV infection dynamics in human bronchial epithelial (HBE) organoids, focusing on HCoV‐OC43, SARS‐CoV, MERS‐CoV, and SARS‐CoV‐2. Utilizing advanced organoid culture techniques, we observed robust replication for all beta‐CoVs, particularly noting that SARS‐CoV‐2 reached peak viral RNA levels at 72 h postinfection. Through comprehensive transcriptomic analysis, we identified significant shifts in cell population dynamics, marked by an increase in goblet cells and a concurrent decrease in ciliated cells. Furthermore, our cell tropism analysis unveiled distinct preferences in viral targeting: HCoV‐OC43 predominantly infected club cells, while SARS‐CoV had a dual tropism for goblet and ciliated cells. In contrast, SARS‐CoV‐2 primarily infected ciliated cells, and MERS‐CoV showed a marked affinity for goblet cells. Host factor analysis revealed the upregulation of genes encoding viral receptors and proteases. Notably, HCoV‐OC43 induced the unfolded protein response pathway, which may facilitate viral replication. Our study also reveals a complex interplay between inflammatory pathways and the suppression of interferon responses during beta‐CoV infections. These findings provide insights into host‐virus interactions and antiviral defense mechanisms, contributing to our understanding of beta‐CoV infections in the respiratory tract. [ABSTRACT FROM AUTHOR]

Obesity has been identified as an independent risk factor for severe outcomes in humans with coronavirus disease 2019 (COVID‐19) and other infectious diseases. Here, we established a mouse model of COVID‐19 using the murine betacoronavirus, mouse hepatitis virus 1 (MHV‐1). C57BL/6 and C3H/HeJ mice exposed to MHV‐1 developed mild and severe disease, respectively. Obese C57BL/6 mice developed clinical manifestations similar to those of lean controls. In contrast, all obese C3H/HeJ mice succumbed by 8 days postinfection, compared to a 50% mortality rate in lean controls. Notably, both lean and obese C3H/HeJ mice exposed to MHV‐1 developed lung lesions consistent with severe human COVID‐19, with marked evidence of diffuse alveolar damage (DAD). To identify early predictive biomarkers of worsened disease outcomes in obese C3H/HeJ mice, we sequenced RNA from whole blood 2 days postinfection and assessed changes in gene and pathway expression. Many pathways uniquely altered in obese C3H/HeJ mice postinfection aligned with those found in humans with severe COVID‐19. Furthermore, we observed altered gene expression related to the unfolded protein response and lipid metabolism in infected obese mice compared to their lean counterparts, suggesting a role in the severity of disease outcomes. This study presents a novel model for studying COVID‐19 and elucidating the mechanisms underlying severe disease outcomes in obese and other hosts. [ABSTRACT FROM AUTHOR]