Endoplasmic Reticulum Function Research Articles

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

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. 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. 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. 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. 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.

8596 Brain Type 3 Deiodinase Is Induced in Two Disease Models That Lead to Cognitive Impairment: Liver Dysfunction and Alzheimer Disease

Abstract Disclosure: S. Wajner: None. T. Oliveira: None. M. Dreher: None. R. Ribeiro: None. C. Gonçalves: None. M.R. Alveres-da-Silva: None. Thyroid hormone is the leading regulator of cell energy production in most tissues, mainly the brain. While the activation process of T4 into T3 depends on D1 and D2 deiodinases, type 3 is the main enzyme that inactivates T3. Several mechanisms, among them oxidative stress, led by disease, imbalances and induces D3, diminishing T3 levels. The response of D3 in the brain in the context of different disease models has yet to be studied. Here we evaluated D3 induction in the brain in two animal disease models, one systemic and the other local. Methodology: To the metabolic dysfunction-associated steatosis liver disease model Male/adult Sprague Dawley rats (n=20) were assigned to control group (standard diet-2.93kcal/g) or high-fat-diet group (CDHF-4.3kcal/g). In the streptozotocin-induced (STZ) Alzheimer's model Adult Wistar rats (n=16) were allocated to the control group (5uL of citrate) or 5uL of streptozotocin. Sham animals were used as controls. D3 expression, oxidative stress parameters, endoplasmic stress and mitochondrial amount measured in the brain. Levels of D3 increased in the brain (∼30% in each group, P<0.0001) in both MASLD and STZ groups. Cerebral tissue from both groups had augmented carbonyl levels (P<0.001) and reduced sulfhydryl (P<0.001). Glutathione was diminished. Antioxidant defenses endoplasmic reticulum function and mitochondrial concentration were altered (P=0.001). The augmented T3 inactivation by D3 dysfunction in brain due to oxidative stress disrupts ER-mitochondrial contact interaction, changing the function of organelles in both brain disease models, shedding light to new mechanisms of action of thyroid hormone in severe brain disease. Presentation: 6/3/2024

Discovery and optimization of anthraquinone derivatives containing substituted bisbenzyloxy groups as a novel scaffold damaged endoplasmic reticulum and against hepatocellular carcinoma cells

This paper reports the antitumor activity and possible mechanism of anthraquinone derivatives containing substituted bisbenzyloxy groups. Series of anthraquinone derivatives containing substituted bisbenzyloxy groups were designed and synthesized by etherification and esterification. The antitumor activities of the synthesized substituted bisbenzyloxy anthraquinone derivatives on liver cancer cell Huh7, triple negative breast cancer cell line MDA-MB-231 and lung cancer cell A549 were in the order of methoxy substitution > methyl substitution > chloral substitution. Among these, the Compound KA-MO-g showed strong antitumor activity, especially against liver cancer Huh7 cells. Further studies on the antitumor mechanism showed that the Compound KA-MO-g simultaneously activated three pathways of endoplasmic reticulum stress (ERS), also caused impairment of endoplasmic reticulum (ER) functions, such as glycoprotein synthesis and disulfide bond formation are impeded and caused calcium overload,then increased mitochondrial ROS, damaged of mitochondria, changed of apoptosis-related protein levels, activated Caspase 3, induced the apoptosis of Huh7 cells. Because KA-MO-g showed strong antitumor activity, it is expected to be a new candidate drug for treating liver cancer and is worth further study.

The p53 target DRAM1 modulates calcium homeostasis and ER stress by promoting contact between lysosomes and the ER through STIM1

It is well established that DNA Damage Regulated Autophagy Modulator 1 (DRAM1), a lysosomal protein and a target of p53, participates in autophagy. The cellular functions of DRAM1 beyond autophagy remain elusive. Here, we show p53-dependent upregulation of DRAM1 in mitochondrial damage-induced Parkinson's disease (PD) models and exacerbation of disease phenotypes by DRAM1. We find that the lysosomal location of DRAM1 relies on its intact structure including the cytosol-facing C-terminal domain. Excess DRAM1 disrupts endoplasmic reticulum (ER) structure, triggers ER stress, and induces protective ER-phagy. Mechanistically, DRAM1 interacts with stromal interacting molecule 1 (STIM1) to tether lysosomes to the ER and perturb STIM1 function in maintaining intracellular calcium homeostasis. STIM1 overexpression promotes cellular health by restoring calcium homeostasis, ER stress response, ER-phagy, and AMP-activated protein kinase (AMPK)-Unc-51 like autophagy activating kinase 1 (ULK1) signaling in cells with excess DRAM1. Thus, by promoting organelle contact between lysosomes and the ER, DRAM1 modulates ER structure and function and cell survival under stress. Our results suggest that DRAM1 as a lysosomal protein performs diverse roles in cellular homeostasis and stress response. These findings may have significant implications for our understanding of the role of the p53/DRAM1 axis in human diseases, from cancer to neurodegenerative diseases.

Discovering common pathogenetic processes between periodontitis and Alzheimer’s disease by bioinformatics and system biology approach

BackgroundThere is increasing evidence that inflammation plays a key role in the pathophysiology of periodontitis (PT) and Alzheimer’s disease (AD), but the roles of inflammation in linking PT and AD are not clear. Our aim is to analyze the potential molecular mechanisms between these two diseases using bioinformatics and systems biology approaches.MethodsTo elucidate the link between PT and AD, we selected shared genes (SGs) with gene-disease-association scores of ≥ 0.1 from the Disease Gene Network (DisGeNET) database, followed by extracting the hub genes. Based on these genes, we constructed gene ontology (GO) enrichment analysis, pathway enrichment analysis, protein-protein interaction (PPI) networks, transcription factors (TFs)-gene networks, microRNAs (miRNAs)-gene regulatory networks, and gene-disease association analyses. Finally, the Drug Signatures database (DSigDB) was utilized to predict candidate molecular drugs related to hub genes.ResultsA total of 21 common SGs between PT and AD were obtained. Cell cytokine activity, inflammatory response, and extracellular membrane were the most important enriched items in GO analysis. Interleukin-10 Signaling, LTF Danger Signal Response Pathway, and RAGE Pathway were identified as important shared pathways. IL6, IL10, IL1B, TNF, IFNG, CXCL8, CCL2, MMP9, TLR4 were identified as hub genes. Both shared pathways and hub genes are closely related to endoplasmic reticulum (ER) stress and mitochondrial dysfunction. Importantly, glutathione, simvastatin, and dexamethasone were identified as important candidate drugs for the treatment of PT and AD.ConclusionsThere is a close link between PT and AD pathogenesis, which may involve in the inflammation, ER and mitochondrial function.

African swine fever virus modulates the endoplasmic reticulum stress-ATF6-calcium axis to facilitate viral replication

ABSTRACT African swine fever (ASF), caused by African swine fever virus (ASFV), is a devastating infectious disease of domestic pigs and wild boar, which threatens the global pig industry. Endoplasmic reticulum (ER) is a multifunctional signaling organelle in eukaryotic cells that is involved in protein synthesis, processing, posttranslational modification and quality control. As intracellular parasitic organisms, viruses have evolved several strategies to modulate ER functions to favor their life cycles. We have previously demonstrated that the differentially expressed genes associated with unfolded protein response (UPR), which represents a response to ER stress, are significantly enriched upon ASFV infection. However, the correlation between the ER stress or UPR and ASFV replication has not been illuminated yet. Here, we demonstrated that ASFV infection induces ER stress both in target cells and in vivo, and subsequently activates the activating transcription factor 6 (ATF6) branch of the UPR to facilitate viral replication. Mechanistically, ASFV infection disrupts intracellular calcium (Ca2+) homeostasis, while the ATF6 pathway facilitates ASFV replication by increasing the cytoplasmic Ca2+ level. More specifically, we demonstrated that ASFV infection triggers ER-dependent Ca2+ release via the inositol triphosphate receptor (IP3R) channel. Notably, we showed that the ASFV B117L protein plays crucial roles in ER stress and the downstream activation of the ATF6 branch, as well as the disruption of Ca2+ homeostasis. Taken together, our findings reveal for the first time that ASFV modulates the ER stress-ATF6-Ca2+ axis to facilitate viral replication, which provides novel insights into the development of antiviral strategies for ASFV.

Transcriptomics analysis reveals the effect of Pulsatilla decoction butanol extract on endoplasmic reticulum and peroxisome function of Candida albicans in hyphal state

Ethnopharmacological relevanceThe traditional Chinese medicine formula known as Pulsatilla decoction was utilized to treat conditions such as bacterial dysentery, ulcerative colitis, and fungal infections like vulvovaginal candidiasis (VVC) caused by Candida albicans (C. albicans). In our prior research, it was shown that the n-butanol extract from Pulsatilla Decoction (BEPD) exhibited effective inhibition of C. albicans. Nevertheless, the exact mechanism by which BEPD hinders hyphal growth, a critical virulence factor of C. albicans, remains unclear. Aim of the studyIn the present study, the inhibitory effect and mechanism of the BEPD on C. albicans hyphal growth was predicted by transcriptome analysis, and further verified by in vitro and in vivo experiments. Materials and methodsThe BEPD was prepared and C. albicans was cultured to induce the hyphal state. Transcriptome analysis was conducted to predict the significant difference in enrichment genes and signaling pathways in the inhibitory effect of BEPD on C. albicans hyphae. Various methods, such as spot assay, time-growth curve analysis, Confocal laser scanning microscope (CLSM), scanning electron microscope (SEM), transmission electron microscope (TEM), flow cytometry, and spectrophotometer, were used to assess the effect of BEPD on hyphal structure and growth activity, lipid peroxidation level, peroxidase (CAT) activity, superoxide dismutase (SOD) activity, and apoptosis of C. albicans. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was employed to examine the expression levels of genes associated with endoplasmic reticulum and peroxisome function. The VVC model was employed to evaluate the influence of BEPD on the growth of C. albicans hyphae in vivo. ResultThe growth of C. albicans hyphae on solid culture media was significantly inhibited by BEPD. CLSM showed that the length of C. albicans hyphae was decreased and their vitality was lowered. SEM indicated that the hyphae of C. albicans were fractured, while TEM revealed damage to the organelles within the cells. GO enrichment and KEGG pathways analysis from transcriptomic data demonstrated that BEPD effectively suppressed the functioning of the endoplasmic reticulum and peroxisomes in C. albicans hyphae. RT-qPCR verified the decreased expression of genes associated with endoplasmic reticulum and peroxisome function by BEPD. Investigation of the endoplasmic reticulum revealed that BEPD elevated levels of reactive oxygen species (ROS) and apoptosis, indicating endoplasmic reticulum stress, as well as malondialdehyde (MDA), a marker of oxidative stress. Additionally, BEPD was shown to lower the activities of catalase (CAT) and superoxide dismutase (SOD). In animal trials, BEPD effectively hindered the growth of C. albicans hyphae in the vaginas of mice with VVC, thus reducing immune inflammatory damage to the vaginal mucosa of these mice. ConclusionThis study demonstrates that BEPD has an inhibitory effect on hyphae, which are an important virulence factor of C. albicans. This effect may be related to BEPD's inhibitory effect on endoplasmic reticulum (ER) and peroxisome function. The findings suggest that BEPD could potentially play a therapeutic role in C. albicans infectious diseases by inhibiting hyphae.

Into the deep: Exploring the molecular mechanisms of hyperactive behaviour induced by three rare earth elements in early life-stages of the deep-sea scavenging amphipod Tmetonyx cicada (Lysianassidae)

With increasing socio-economic importance of the rare earth elements and yttrium (REY), Norway has laid out plans for REY mining, from land-based to deep-sea mining, thereby enhancing REY mobility in the marine ecosystem. Little is known about associated environmental consequences, especially in the deep ocean. We explored the toxicity and modes of action of a light (Nd), medium (Gd) and heavy (Yb) REY-Cl3 at four concentrations (3, 30, 300, and 3000 μg L−1) in the Arcto-boreal deep-sea amphipod Tmetonyx cicada. At the highest concentration, REY solubility was limited and increased with atomic weight (Nd < Gd < Yb). Lethal effects were practically restricted to this treatment, with the lighter elements being more acutely toxic than Yb (from ∼50 % mortality in the Gd-group at dissolved 689–504 μg L−1 to <20 % in the Yb-group at ca. 2000 μg L−1), which could be a function of bioavailability. All three REY induced hyperactivity at the low-medium concentrations. Delving into the transcriptome of T. cicada allowed us to determine a whole array of potential (neurotoxic) mechanisms underlying this behaviour. Gd induced the vastest response, affecting serotonin-synthesis; sphingolipid-synthesis; the renin-angiotensin system; mitochondrial and endoplasmic reticulum functioning (Gd, Nd); and lysosome integrity (Gd, Yb); as well as the expression of hemocyanin, potentially governing REY-uptake (Gd, Yb). While Nd and Yb shared only few pathways, suggesting a link between mode of action and atomic weight/radius, almost all discussed mechanisms imply the disruption of organismal Ca-homeostasis. Despite only fragmental genomic information available for crustaceans to date, our results provide novel insight into the toxicophysiology of REY in marine biota. The neurotoxic/behavioural effects in T. cicada at concentrations with potential environmental relevance warn about the possibility of bottom-up ecological consequences in mining exposed fjords and deep-sea ecosystems, calling for follow-up studies and regulatory measures prior to the onset of REY mining in Norway.

Dysregulation of ceramide metabolism causes phytoceramide-dependent induction of the unfolded protein response.

The unfolded protein response (UPR) detects and mitigates the harmful effects of dysregulated endoplasmic reticulum (ER) function. The UPR has been best characterized as a protein quality control response, and the sole UPR sensor in yeast, Ire1, is known to detect misfolded ER proteins. However, recent work suggests the UPR can also sense diverse defects within the ER membrane, including increased fatty acid saturation and altered phospholipid abundance. These and other lipid-related stimuli have been referred to as lipid bilayer stress and may be sensed independently through Ire1's transmembrane domain. Here, we show that the loss of Isc1, a phospholipase that catabolizes complex ceramides, causes UPR induction, even in the absence of exogenous stress. A series of chemical and genetic approaches identified a requirement for very long-chain fatty acid (VLCFA)-containing phytoceramides for UPR induction. In parallel, comprehensive lipidomics analyses identified large increases in the abundance of specific VLCFA-containing phytoceramides in the isc1Δ mutant. We failed to identify evidence of an accompanying defect in protein quality control or ER-associated protein degradation. These results extend our understanding of lipid bilayer stress in the UPR and provide a foundation for mechanistic investigation of this fascinating intersection between ceramide metabolism, membrane homeostasis, and the UPR.

A deep phenotyping study in mouse and iPSC models to understand the role of oligodendroglia in optic neuropathy in Wolfram syndrome

Wolfram syndrome (WS) is a rare childhood disease characterized by diabetes mellitus, diabetes insipidus, blindness, deafness, neurodegeneration and eventually early death, due to autosomal recessive mutations in the WFS1 (and WFS2) gene. While it is categorized as a neurodegenerative disease, it is increasingly becoming clear that other cell types besides neurons may be affected and contribute to the pathogenesis. MRI studies in patients and phenotyping studies in WS rodent models indicate white matter/myelin loss, implicating a role for oligodendroglia in WS-associated neurodegeneration. In this study, we sought to determine if oligodendroglia are affected in WS and whether their dysfunction may be the primary cause of the observed optic neuropathy and brain neurodegeneration. We demonstrate that 7.5-month-old Wfs1∆exon8 mice display signs of abnormal myelination and a reduced number of oligodendrocyte precursor cells (OPCs) as well as abnormal axonal conduction in the optic nerve. An MRI study of the brain furthermore revealed grey and white matter loss in the cerebellum, brainstem, and superior colliculus, as is seen in WS patients. To further dissect the role of oligodendroglia in WS, we performed a transcriptomics study of WS patient iPSC-derived OPCs and pre-myelinating oligodendrocytes. Transcriptional changes compared to isogenic control cells were found for genes with a role in ER function. However, a deep phenotyping study of these WS patient iPSC-derived oligodendroglia unveiled normal differentiation, mitochondria-associated endoplasmic reticulum (ER) membrane interactions and mitochondrial function, and no overt signs of ER stress. Overall, the current study indicates that oligodendroglia functions are largely preserved in the WS mouse and patient iPSC-derived models used in this study. These findings do not support a major defect in oligodendroglia function as the primary cause of WS, and warrant further investigation of neurons and neuron-oligodendroglia interactions as a target for future neuroprotective or -restorative treatments for WS.

Krüppel-like factor 6 involvement in the endoplasmic reticulum homeostasis of extravillous trophoblasts

IntroductionTrophoblast homeostasis and differentiation require a proper endoplasmic reticulum (ER) function. The Krüppel-like factor-6 (KLF6) transcription factor modulates trophoblast migration, differentiation, and reactive oxygen species (ROS) production. Since ROS may impact on ER homeostasis, we assessed whether downregulation of KLF6 altered the unfolded protein response (UPR) and cellular process associated with ER homeostasis. Materials and methodsProtein and RNA expression were analyzed by Western blot and qRT-PCR, respectively, in extravillous trophoblast HTR-8/SVneo cells silenced for KLF6. Apoptosis was detected by flow cell cytometry using Annexin V Apoptosis Detection Kit. Protein trafficking was assessed by confocal microscopy of a reporter fluorescent protein whose release from the ER was synchronized. ResultsKLF6 downregulation reduced the expression of BiP, the master regulator of the UPR, at protein, mRNA, and pre-mRNA levels. Ire1α protein, XBP1 splicing, and DNAJB9 mRNA levels were also reduced in KLF6-silenced cells. Instead, PDI, Ero1α, and the p-eIF2α/eIF2α ratio as well as autophagy and proteasome dependent protein degradation remained unchanged while intracellular trafficking was increased. Under thapsigargin-induced stress, KLF6 silencing impaired BiP protein and mRNA expression increase, as well as the activation of the Ire1α pathway, but it raised the p-eIF2α/eIF2α ratio and CHOP protein levels. Nevertheless, apoptosis was not increased. DiscussionResults provide the first evidence of KLF6 as a modulator of the UPR components. The increase in protein trafficking and protection from apoptosis, observed in KLF6-silenced cells, are consistent with its role in extravillous trophoblast migration and differentiation.

Multiomics Analyses Explore the Immunometabolic Interplay in the Liver of White Crucian Carp (Carassius cuvieri) After Aeromonas veronii Challenge.

Aeromonas veronii is one of the predominant pathogenic species that can imperil the survival of farmed fish. However, the interactive networks of immune regulation and metabolic response in A. veronii-infected fish are still unclear. In this investigation, we aimed to explore immunometabolic interplay in white crucian carp (WCC) after the A. veronii challenge. Elevated levels of immune-related genes were observed in various tissues after A. veronii infection, along with the sharp alteration of disease-related enzymatic activities. Besides, decreased levels of antioxidant status were observed in the liver, but most metabolic gene expressions increased dramatically. Multiomics analyses revealed that metabolic products of amino acids, such as formiminoglutamic acid (FIGLU), L-glutamate (L-Glu), and 4-hydroxyhippuric acid, were considered the crucial liver biomarkers in A. veronii-infected WCC. In addition, A. veronii infection may dysregulate endoplasmic reticulum (ER) function to affect the metabolic process of lipids, carbohydrates, and amino acids in the liver of WCC. These results may have a comprehensive implication for understanding immunometabolic response in WCC upon A. veronii infection.

Mitofusin 1 and 2 overexpression reduces AβO-mediated ER stress and apoptosis in N2a APPswe cells.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, and amyloid beta oligomers (AβO), which are pathological markers of AD, are known to be highly toxic. AβO increase mitochondrial dysfunction, which is accompanied by a decrease in mitochondrial fusion. Although mitofusin (Mfn) 1 and Mfn2 are mitochondrial fusion proteins, Mfn2 is known to regulate endoplasmic reticulum (ER) function, as it is located in the ER. Several studies have shown that AβO exacerbates ER stress, however, the exact mechanism requires further elucidation. In this study, we used mouse neuroblastoma cells stably overexpressing the amyloid precursor protein (APP) with the Swedish mutation (N2a APPswe cells) to investigate the role of Mfn in ER stress. Our results revealed that amyloid beta (Aβ) caused cellular toxicity in N2a APPswe cells, upregulated ER stress-related proteins, and promoted ER expansion. The AβO-mediated ER stress was reduced when Mfn1 and Mfn2 were overexpressed. Moreover, Mfn1 and Mfn2 overexpressed resulted in reduced apoptosis of N2a APPswe cells. In conclusion, our results indicate that both Mfn1 and Mfn2 reduce ER stress and apoptosis. Our data provide a foundation for future studies on the roles of Mfn1 and Mfn2 in the molecular mechanisms underlying AβO-mediated ER stress and the pathogenesis of AD.

Endoplasmic Reticulum Stress-Mediated Cell Death in Renal Fibrosis.

The endoplasmic reticulum (ER) is indispensable for maintaining normal life activities. Dysregulation of the ER function results in the accumulation of harmful proteins and lipids and the disruption of intracellular signaling pathways, leading to cellular dysfunction and eventual death. Protein misfolding within the ER disrupts its delicate balance, resulting in the accumulation of misfolded or unfolded proteins, a condition known as endoplasmic reticulum stress (ERS). Renal fibrosis, characterized by the aberrant proliferation of fibrotic tissue in the renal interstitium, stands as a grave consequence of numerous kidney disorders, precipitating a gradual decline in renal function. Renal fibrosis is a serious complication of many kidney conditions and is characterized by the overgrowth of fibrotic tissue in the glomerular and tubular interstitium, leading to the progressive failure of renal function. Studies have shown that, during the onset and progression of kidney disease, ERS causes various problems in the kidneys, a process that can lead to kidney fibrosis. This article elucidates the underlying intracellular signaling pathways modulated by ERS, delineating its role in triggering diverse forms of cell death. Additionally, it comprehensively explores a spectrum of potential pharmacological agents and molecular interventions aimed at mitigating ERS, thereby charting novel research avenues and therapeutic advancements in the management of renal fibrosis.

Melatonin regulates endoplasmic reticulum stress in diverse pathophysiological contexts: A comprehensive mechanistic review.

The endoplasmic reticulum (ER) is crucial for protein quality control, and disruptions in its function can lead to various diseases. ER stress triggers an adaptive response called the unfolded protein response (UPR), which can either restore cellular homeostasis or induce cell death. Melatonin, a safe and multifunctional compound, shows promise in controlling ER stress and could be a valuable therapeutic agent for managing the UPR. By regulating ER and mitochondrial functions, melatonin helps maintain cellular homeostasis via reduction of oxidative stress, inflammation, and apoptosis. Melatonin can directly or indirectly interfere with ER-associated sensors and downstream targets of the UPR, impacting cell death, autophagy, inflammation, molecular repair, among others. Crucially, this review explores the mechanistic role of melatonin on ER stress in various diseases including liver damage, neurodegeneration, reproductive disorders, pulmonary disease, cardiomyopathy, insulin resistance, renal dysfunction, and cancer. Interestingly, while it alleviates the burden of ER stress in most pathological contexts, it can paradoxically stimulate ER stress in cancer cells, highlighting its intricate involvement in cellular homeostasis. With numerous successful studies using in vivo and in vitro models, the continuation of clinical trials is imperative to fully explore melatonin's therapeutic potential in these conditions.

Fam134c and Fam134b shape axonal endoplasmic reticulum architecture in vivo

Endoplasmic reticulum (ER) remodeling is vital for cellular organization. ER-phagy, a selective autophagy targeting ER, plays an important role in maintaining ER morphology and function. The FAM134 protein family, including FAM134A, FAM134B, and FAM134C, mediates ER-phagy. While FAM134B mutations are linked to hereditary sensory and autonomic neuropathy in humans, the physiological role of the other FAM134 proteins remains unknown. To address this, we investigate the roles of FAM134 proteins using single and combined knockouts (KOs) in mice. Single KOs in young mice show no major phenotypes; however, combined Fam134b and Fam134c deletion (Fam134b/cdKO), but not the combination including Fam134a deletion, leads to rapid neuromuscular and somatosensory degeneration, resulting in premature death. Fam134b/cdKO mice show rapid loss of motor and sensory axons in the peripheral nervous system. Long axons from Fam134b/cdKO mice exhibit expanded tubular ER with a transverse ladder-like appearance, whereas no obvious abnormalities are present in cortical ER. Our study unveils the critical roles of FAM134C and FAM134B in the formation of tubular ER network in axons of both motor and sensory neurons.

MoSey1 regulates the unfolded protein response, appressorium development, and pathogenicity of Magnaporthe oryzae

Endoplasmic reticulum (ER) is an enclosed three-dimensional eukaryotic membrane network composed of flattened sacs. Fusion of homologous membranes to the ER membrane is essential for the maintenance of this network structure. In yeast, ER membrane fusion is mediated by Sey1p, whose paralogues function distinctly in different species. In this study, we investigated the biological functions of MoSEY1 in the devastating rice blast fungus Magnaporthe oryzae by functional genomic approach. Compared to wild type, deletion of MoSEY1 considerably decreased the growth and conidia production of M. oryzae. Additionally, the absence of MoSEY1 delayed appressorium formation and invasive hyphae growth. The appressorium function was also impaired in ΔMosey1 mutant. Subcellular localization analysis revealed that MoSey1 is localized at the ER. The ΔMosey1 mutant showed augmented sensitivity to ER stress. Additionally, we found that MoSey1 regulated the unfolded protein response, autophagy, and protein secretion in M. oryzae. In conclusion, our study unveiled the involvement of MoSey1 in the development, pathogenesis, and ER functions in M. oryzae.

Impact of DEHP on mitochondria-associated endoplasmic reticulum membranes and reproductive toxicity in ovary

Di(2-ethylhexyl) phthalate (DEHP) is a widely recognized environmental endocrine disruptor that potentially impacts female reproductive function, although the specific mechanisms leading to such impairment remain unclear. A growing body of research has revealed that the endoplasmic reticulum and mitochondrial function significantly influence oocyte quality. The structure of mitochondria-associated endoplasmic reticulum membranes (MAMs) is crucial for facilitating the exchange of Ca2+, lipids, and metabolites. This study aimed to investigate the alterations in the composition and function of MAMs after DEHP exposure and to elucidate the underlying mechanisms of ovarian toxicity. The female mice were exposed to DEHP at doses of 5 and 500 mg/kg/day for one month. The results revealed that DEHP exposure led to reduced serum anti-Müllerian hormone levels and increased atretic follicles in mice. DEHP induced endoplasmic reticulum stress and disrupted calcium homeostasis in oocytes. Furthermore, DEHP impaired the mitochondrial function of oocytes and reduced their membrane potential, and promoting apoptosis. Similar results were observed in human granulosa cells after exposure to mono-(2-ethylhexyl) phthalate (MEHP, metabolites of DEHP) in vitro. Proteomic analysis and transmission electron microscopy revealed modifications in the functional proteins and structure of the MAMs, and the suppression of oxidative phosphorylation pathways. The findings of this investigation provide a new perspective on the mechanism underlying the reproductive toxicity of DEHP in females.

Chronic Epinephrine-Induced Endoplasmic Reticulum and Oxidative Stress Impairs Pancreatic β-Cells Function and Fate.

Epinephrine influences the function of pancreatic β-cells, primarily through the α2A-adrenergic receptor (α2A-AR) on their plasma membrane. Previous studies indicate that epinephrine transiently suppresses insulin secretion, whereas prolonged exposure induces its compensatory secretion. Nonetheless, the impact of epinephrine-induced α2A-AR signaling on the survival and function of pancreatic β-cells, particularly the impact of reprogramming after their removal from sustained epinephrine stimulation, remains elusive. In the present study, we applied MIN6, a murine insulinoma cell line, with 3 days of high concentration epinephrine incubation and 2 days of standard incubation, explored cell function and activity, and analyzed relevant regulatory pathways. The results showed that chronic epinephrine incubation led to the desensitization of α2A-AR and enhanced insulin secretion. An increased number of docked insulin granules and impaired Syntaxin-2 was found after chronic epinephrine exposure. Growth curve and cell cycle analyses showed the inhibition of cell proliferation. Transcriptome analysis showed the occurrence of endoplasmic reticulum stress (ER stress) and oxidative stress, such as the presence of BiP, CHOP, IRE1, ATF4, and XBP, affecting cellular endoplasmic reticulum function and survival, along with UCP2, OPA1, PINK, and PRKN, associated with mitochondrial dysfunction. Consequently, we conclude that chronic exposure to epinephrine induces α2A-AR desensitization and leads to ER and oxidative stress, impairing protein processing and mitochondrial function, leading to modified pancreatic β-cell secretory function and cell fate.

A series of pyrimidine-based antifungals with anti-mold activity disrupt ER function in Aspergillus fumigatus.

Fungal infections are a major contributor to morbidity and mortality among immunocompromised populations. Moreover, fungal disease caused by molds are difficult to treat and are associated with particularly high mortality. To address the need for new mold-active antifungal drugs, we performed a high-throughput screen with Aspergillus fumigatus, the most common pathogenic mold. We identified a novel, pyrimidine-based chemical scaffold with broad-spectrum antifungal activity including activity against several difficult-to-treat molds. A chemical genetics screen of Saccharomyces cerevisiae suggested that this compound may target the endoplasmic reticulum (ER) and perturb ER function and/or homeostasis. Consistent with this model, this compound induces the unfolded protein response and inhibits secretion of A. fumigatus collagenases. Initial cytotoxicity and pharmacokinetic studies show favorable features including limited mammalian cell toxicity and bioavailability in vivo. Together, these data support the further medicinal chemistry and pre-clinical development of this pyrimidine scaffold toward more effective treatments for life-threatening invasive mold infections.IMPORTANCEInvasive fungal diseases are life-threatening infections caused by fungi in immunocompromised individuals. Currently, there are only three major classes of antifungal drugs available to treat fungal infections; however, these options are becoming even more limited with the global emergence of antifungal drug resistance. To address the need for new antifungal therapies, we performed a screen of chemical compounds and identified a novel molecule with antifungal activity. Initial characterization of this compound shows drug-like features and broad-spectrum activity against medically important fungi. Together, our results support the continued development of this compound as a potential future therapy for these devastating fungal infections.