scholarly journals Melatonin-Mediated Intracellular Insulin during 2-Deoxy-d-glucose Treatment Is Reduced through Autophagy and EDC3 Protein in Insulinoma INS-1E Cells

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Han Sung Kim ◽  
Tae-Young Han ◽  
Yeong-Min Yoo
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Metabolic Pathways ◽  
Mtor Inhibitor ◽  
Glucose Deprivation ◽  
Dependent Manner ◽  
Insulin Production ◽  
Insulin Synthesis ◽  
Dose Dependent ◽  
Rat Insulinoma

2-DG triggers glucose deprivation without altering other nutrients or metabolic pathways and then activates autophagy via activation of AMPK and endoplasmic reticulum (ER) stress. We investigated whether 2-DG reduced intracellular insulin increased by melatonin via autophagy/EDC3 in insulinoma INS-1E cells. p-AMPK and GRP78/BiP level were significantly increased by 2-DG in the presence/absence of melatonin, but IRE1αlevel was reduced in 2-DG treatment. Levels of p85α, p110, p-Akt (Ser473, Thr308), and p-mTOR (Ser2481) were also significantly reduced by 2-DG in the presence/absence of melatonin. Mn-SOD increased with 2-DG plus melatonin compared to groups treated with/without melatonin alone. Bcl-2 was decreased and Bax increased with 2-DG plus melatonin. LC3II level increased with 2-DG treatment in the presence/absence of melatonin. Intracellular insulin production increased in melatonin plus 2-DG but reduced in treatment with 2-DG with/without melatonin. EDC3 was increased by 2-DG in the presence/absence of melatonin. Rapamycin, an mTOR inhibitor, increased GRP78/BiP and EDC3 levels in a dose-dependent manner and subsequently resulted in a decrease in intracellular production of insulin. These results suggest that melatonin-mediated insulin synthesis during 2-DG treatment involves autophagy and EDC3 protein in rat insulinoma INS-1E cells and subsequently results in a decrease in intracellular production of insulin.

scholarly journals Reticulon proteins modulate autophagy of the endoplasmic reticulum in maize endosperm

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Xiaoguo Zhang ◽  
Xinxin Ding ◽  
Richard Scott Marshall ◽  
Julio Paez-Valencia ◽  
Patrick Lacey ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Lipid Droplets ◽  
Autophagic Flux ◽  
Dependent Manner ◽  
Maize Endosperm ◽  
Transmembrane Segments ◽  
C Terminus ◽  
Er Homeostasis ◽  
Dose Dependent

Reticulon (Rtn) proteins shape tubular domains of the endoplasmic reticulum (ER), and in some cases are autophagy receptors for selective ER turnover. We have found that maize Rtn1 and Rtn2 control ER homeostasis and autophagic flux in endosperm aleurone cells, where the ER accumulates lipid droplets and synthesizes storage protein accretions metabolized during germination. Maize Rtn1 and Rtn2 are expressed in the endosperm, localize to the ER, and re-model ER architecture in a dose-dependent manner. Rtn1 and Rtn2 interact with Atg8a using four Atg8-interacting motifs (AIMs) located at the C-terminus, cytoplasmic loop, and within the transmembrane segments. Binding between Rtn2 and Atg8 is elevated upon ER stress. Maize rtn2 mutants display increased autophagy and up-regulation of an ER stress-responsive chaperone. We propose that maize Rtn1 and Rtn2 act as receptors for autophagy-mediated ER turnover, and thus are critical for ER homeostasis and suppression of ER stress.

scholarly journals Activation of Hepatitis B Virus S Promoter by a Cell Type-Restricted IRE1-Dependent Pathway Induced by Endoplasmic Reticulum Stress

2005 ◽  
Vol 25 (17) ◽  
pp. 7522-7533 ◽  
Author(s):  
Zhi-Ming Huang ◽  
Thomas Tan ◽  
Hiderou Yoshida ◽  
Kazutoshi Mori ◽  
Yanjun Ma ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Hepatitis B Virus ◽  
Hepatitis B ◽  
Er Stress ◽  
Transcriptional Activation ◽  
Active Form ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Cell Type ◽  
B Virus

ABSTRACT IRE1-alpha is an integral membrane protein of the endoplasmic reticulum (ER) that is a key sensor in the cellular transcriptional response to stress in the ER. Upon induction of ER stress, IRE1-alpha is activated, resulting in the synthesis of the active form of the transcription factor XBP1 via IRE1-mediated splicing of its mRNA. In this report, we have examined the role of IRE1-alpha and XBP1 in activation of the hepatitis B virus S promoter by ER stress. Cotransfection experiments revealed that overexpression of either IRE1-alpha or XBP1 activated this promoter. Conversely, cotransfected dominant-negative IRE1-alpha or small interfering RNA directed against XBP1 decreased the activation of the S promoter by ER stress, confirming an important role for the IRE1-alpha/XBP1 signaling pathway in activation of the S promoter. However, XBP1 does not bind directly to the S promoter; rather, a novel S promoter-binding complex that does not contain XBP1 is induced in cells undergoing ER stress in an XBP1-dependent manner. This complex, as well as transcriptional activation of the S promoter, is induced by ER stress in hepatocytes but not in fibroblasts, despite the presence of active XBP1 in the latter. Thus, the hepatitis B virus S promoter responds to a novel, cell type-restricted transcriptional pathway downstream of IRE1-alpha and XBP1.

Autophagy triggers endoplasmic reticulum stress and C/EBP homologous protein-mediated apoptosis in OGD/R-treated neurons in a caspase-12-independent manner

2021 ◽  
Author(s):  
Ying Tian ◽  
Liang Wang ◽  
Zhiqiang Qiu ◽  
Yulun Xu ◽  
Rongrong Hua
Keyword(s):  
Endoplasmic Reticulum ◽  
Cortical Neurons ◽  
Neuronal Apoptosis ◽  
Glucose Deprivation ◽  
Oxygen Glucose Deprivation ◽  
Caspase 8 ◽  
Dependent Manner ◽  
Homologous Protein ◽  
Caspase 12 ◽  
Induced Apoptosis

We reported that a high level of autophagy was initiated by oxygen-glucose deprivation (OGD) and was maintained in neurons even after oxygen-glucose deprivation followed by reoxygenation (OGD/R), accompanied by neuronal apoptosis. This study focused on autophagy-induced apoptosis and its signaling network, especially the role of endoplasmic reticulum stress (ERS). Analysis of primary cultured cortical neurons from mice showed that the autophagy-induced apoptosis depended on Caspase-8 and -9 but not Caspase-12. This finding did not mean that the endoplasmic reticulum did not participate in this process. Increases in the levels of endoplasmic reticulum (ER) biomarkers and Binding immunoglobulin protein (BiP) were induced by autophagy in OGD/R-treated neurons. In addition, as an apoptotic transcription factor induced by ER stress, C/EBP homologous protein (CHOP) expression was significantly increased in neurons after OGD/R. This result suggested that the autophagy-Bip-CHOP-caspase (8 and 9)-dependent apoptotic signaling pathway at least partly participated in autophagy-induced apoptosis in primary cortical neurons. It revealed that ER induced apoptosis in neurons suffering from OGD/R injury in an ER stress-CHOP-dependent manner rather than a caspase-12-dependent manner. However, more research on signaling or cross-linking networks and intermediate links are needed. The realization of caspase-12-independent BiP-CHOP neuronal apoptosis pathway has expanded our understanding of the neuronal apoptosis network, which may eventually provide endogenous interventional strategies for OGD/R injury after stroke.

scholarly journals Endoplasmic Reticulum Stress Mediates Vascular Smooth Muscle Cell Calcification via Increased Release of Grp78-Loaded Extracellular Vesicles

2020 ◽  
Author(s):  
Malgorzata Furmanik ◽  
Rick van Gorp ◽  
Meredith Whitehead ◽  
Sadia Ahmad ◽  
Jayanta Bordoloi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Er Stress ◽  
Vascular Calcification ◽  
Bone Mineralization ◽  
Extracellular Vesicle ◽  
Dependent Manner ◽  
The Matrix ◽  
Stress Dependent

Objective: Vascular calcification is common among aging populations and mediated by vascular smooth muscle cells (VSMCs). The endoplasmic reticulum (ER) is involved in protein folding and ER stress has been implicated in bone mineralization. The role of ER stress in VSMC-mediated calcification is less clear. Approach and Results: mRNA expression of the ER stress markers PERK (PKR (protein kinase RNA)-like ER kinase), ATF (activating transcription factor) 4, ATF6, and Grp78 was detectable in human vessels with levels of PERK decreased in calcified plaques compared to healthy vessels. Protein deposition of Grp78/Grp94 was increased in the matrix of calcified arteries. Induction of ER stress accelerated human primary VSMC-mediated calcification, elevated expression of some osteogenic markers (Runx2, Osterix, ALP, BSP, and OPG), and decreased expression of SMC markers. ER stress potentiated extracellular vesicle (EV) release via SMPD3. EVs from ER stress-treated VSMCs showed increased Grp78 levels and calcification. Electron microscopy confirmed the presence of Grp78/Grp94 in EVs. siRNA knock-down of Grp78 decreased calcification. Warfarin-induced Grp78 and ATF4 expression in rat aortas and VSMCs and increased calcification in an ER stress-dependent manner via increased EV release. Conclusions: ER stress induces vascular calcification by increasing release of Grp78-loaded EVs. Our results reveal a novel mechanism of action of warfarin, involving increased EV release via the PERK-ATF4 pathway, contributing to calcification. This study is the first to show that warfarin induces ER stress and to link ER stress to cargo loading of EVs.

scholarly journals The PERK-Dependent Molecular Mechanisms as a Novel Therapeutic Target for Neurodegenerative Diseases

2020 ◽  
Vol 21 (6) ◽  
pp. 2108 ◽  
Author(s):  
Wioletta Rozpędek-Kamińska ◽  
Natalia Siwecka ◽  
Adam Wawrzynkiewicz ◽  
Radosław Wojtczak ◽  
Dariusz Pytel ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Neurodegenerative Diseases ◽  
Er Stress ◽  
Molecular Mechanisms ◽  
Treatment Strategies ◽  
Stress Conditions ◽  
World Population ◽  
Dependent Manner ◽  
Age Related ◽  
The Unfolded Protein Response

Higher prevalence of neurodegenerative diseases is strictly connected with progressive aging of the world population. Interestingly, a broad range of age-related, neurodegenerative diseases is characterized by a common pathological mechanism—accumulation of misfolded and unfolded proteins within the cells. Under certain circumstances, such protein aggregates may evoke endoplasmic reticulum (ER) stress conditions and subsequent activation of the unfolded protein response (UPR) signaling pathways via the protein kinase RNA-like endoplasmic reticulum kinase (PERK)-dependent manner. Under mild to moderate ER stress, UPR has a pro-adaptive role. However, severe or long-termed ER stress conditions directly evoke shift of the UPR toward its pro-apoptotic branch, which is considered to be a possible cause of neurodegeneration. To this day, there is no effective cure for Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), or prion disease. Currently available treatment approaches for these diseases are only symptomatic and cannot affect the disease progression. Treatment strategies, currently under detailed research, include inhibition of the PERK-dependent UPR signaling branches. The newest data have reported that the use of small-molecule inhibitors of the PERK-mediated signaling branches may contribute to the development of a novel, ground-breaking therapeutic approach for neurodegeneration. In this review, we critically describe all the aspects associated with such targeted therapy against neurodegenerative proteopathies.

scholarly journals Tunicamycin-Induced Endoplasmic Reticulum Stress Mediates Mitochondrial Dysfunction in Human Adipocytes

2020 ◽  
Vol 105 (9) ◽  
pp. 2905-2918
Author(s):  
Laura Jackisch ◽  
Alice M Murphy ◽  
Sudhesh Kumar ◽  
Harpal Randeva ◽  
Gyanendra Tripathi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Mitochondrial Dysfunction ◽  
Oxidative Capacity ◽  
Basal Respiration ◽  
Dependent Manner ◽  
Human Adipocytes ◽  
Mitochondrial Fragmentation ◽  
Dynamic Relationship ◽  
Obese Subjects

Abstract Context Dysfunctional endoplasmic reticulum (ER) and mitochondria are known to contribute to the pathology of metabolic disease. This damage may occur, in part, as a consequence of ER-mitochondria cross-talk in conditions of nutrient excess such as obesity. To date, insight into this dynamic relationship has not been characterized in adipose tissue. Therefore, this study investigated whether ER stress contributes to the development of mitochondrial inefficiency in human adipocytes from lean and obese participants. Methods Human differentiated adipocytes from Chub-S7 cell line and primary abdominal subcutaneous adipocytes from lean and obese participants were treated with tunicamycin to induce ER stress. Key parameters of mitochondrial function were assessed, including mitochondrial respiration, membrane potential (MMP), and dynamics. Results ER stress led to increased respiratory capacity in a model adipocyte system (Chub-S7 adipocytes) in a concentration and time dependent manner (24 h: 23%↑; 48 h: 68%↑, P < 0.001; 72 h: 136%↑, P < 0.001). This corresponded with mitochondrial inefficiency and diminished MMP, highlighting the formation of dysfunctional mitochondria. Morphological analysis revealed reorganization of mitochondrial network, specifically mitochondrial fragmentation. Furthermore, p-DRP1, a key protein in fission, significantly increased (P < 0.001). Additionally, adipocytes from obese subjects displayed lower basal respiration (49%↓, P < 0.01) and were unresponsive to tunicamycin in contrast to their lean counterparts, demonstrating inefficient mitochondrial oxidative capacity. Conclusion These human data suggest that adipocyte mitochondrial inefficiency is driven by ER stress and exacerbated in obesity. Nutrient excess–induced ER stress leads to mitochondrial dysfunction that may therefore shift lipid deposition ectopically and thus have further implications on the development of related metabolic disorders.

scholarly journals Endoplasmic reticulum stress regulates cell injury in lipopolysaccharide-induced nerve cells

2020 ◽  
Vol 48 (9) ◽  
pp. 030006052094976
Author(s):  
Min Li ◽  
Ying Zhang ◽  
Jixing Wang
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Viability ◽  
Er Stress ◽  
Cell Apoptosis ◽  
Caspase 3 ◽  
Cell Injury ◽  
Cell Counting ◽  
Tunel Staining ◽  
Dependent Manner ◽  
Stress Markers

Objective Sepsis-associated encephalopathy (SAE) is a common complication of sepsis, and excessive endoplasmic reticulum (ER) stress is closely correlated with the cell injury caused by sepsis. This study aimed to analyze the possible role of ER stress in SAE cell models. Methods PC12 and MES23.5 cells were treated with increasing concentrations of lipopolysaccharides (LPS). The Cell Counting Kit-8 assay was used to detect cell viability and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was performed to assess cell apoptosis. In addition, the protein expression levels of ER stress markers [GRP78, CHOP, inositol-requiring enzyme 1 (IRE1), and PKR-like ER kinase (PERK)] and apoptosis-related proteins (Bax, Bcl-2, caspase-3, and cleaved caspase-3) were analyzed using western blotting. Results LPS treatment activated ER stress markers in both the PC12 and MES23.5 cells. The overexpression of GRP78 significantly reduced cell viability and enhanced cell apoptosis in a time-dependent manner. An ER stress inhibitor, 4-PBA, significantly enhanced cell viability and inhibited the cell apoptosis induced by LPS. Therefore, an enhanced unfolded protein response (UPR) and UPR suppression may regulate cell apoptosis. Conclusions UPR was shown to be involved in regulating LPS-induced neuron injury. UPR could be a potential therapeutic target in SAE.

scholarly journals Activation of the Endoplasmic Reticulum Stress Response Impacts the NOD1 Signaling Pathway

2019 ◽  
Vol 87 (8) ◽  
Author(s):  
Jonathan M. Mendez ◽  
Lakshmi Divya Kolora ◽  
James S. Lemon ◽  
Steven L. Dupree ◽  
A. Marijke Keestra-Gounder
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Bacterial Infections ◽  
Diaminopimelic Acid ◽  
Endoplasmic Reticulum Stress Response ◽  
Luciferase Reporter ◽  
Epithelial Cell Line ◽  
Dependent Manner ◽  
Raw264.7 Macrophages ◽  
Stimulation Of

ABSTRACT Nucleotide-binding oligomerization domain 1 (NOD1) is an intracellular pattern recognition receptor (PRR) responsible for sensing bacterial peptidoglycan fragments. Stimulation of NOD1 leads to a robust innate immune response via activation of the major transcription factor NF-κB. In addition to peptidoglycan sensing, NOD1 and the closely related PRR NOD2 have been linked to inflammation by responding to the endoplasmic reticulum (ER) stress-induced unfolded protein response (UPR). Here we show that differential ER stress induction renders cells more susceptible to Salmonella enterica serovar Typhimurium infection in a NOD1-dependent manner, measured by increased NF-κB activation and cytokine expression. In HeLa57A cells stably transfected with an NF-κB::luciferase reporter, we show that cells undergoing ER stress induced by thapsigargin display a significant increase in NF-κB activation in response to NOD1 stimulation by C12-iE-DAP (acylated derivative of the iE-DAP dipeptide [gamma-d-glutamyl-meso-diaminopimelic acid]) and the S. Typhimurium effector protein SopE. Tunicamycin-induced ER stress had no effect on NOD1-stimulated NF-κB activation. We further show that the mouse intestinal epithelial cell line MODE-K and RAW264.7 macrophages are more responsive to Salmonella infection when treated with thapsigargin but not with tunicamycin. These profound differences between thapsigargin- and tunicamycin-treated cells upon inflammation suggest that different components downstream of the UPR contribute to NOD1 activation. We found that the NOD1-induced inflammatory response is dependent on protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) activation in conjunction with stimulation of the inositol triphosphate receptor (IP3R). Together, these results suggest that differential UPR activation makes cells more responsive to bacterial infections in a NOD1-dependent manner.

Effects of Stearic Acid on Proliferation, Differentiation, Apoptosis, and Autophagy in Porcine Intestinal Epithelial Cells

2020 ◽  
Vol 20 (2) ◽  
pp. 157-166
Author(s):  
Yuan Yang ◽  
Jin Huang ◽  
Jianzhong Li ◽  
Huansheng Yang ◽  
Yulong Yin
Keyword(s):  
Cell Differentiation ◽  
Epithelial Cells ◽  
Stearic Acid ◽  
Er Stress ◽  
Intestinal Epithelial Cells ◽  
Dependent Manner ◽  
Intestinal Epithelial ◽  
High Concentrations ◽  
Induced Apoptosis ◽  
Dose Dependent

Background: Stearic acid (SA), a saturated long-chain fatty acid consisting of 18 carbon atoms, is widely found in feed ingredients, such as corn, soybeans, and wheat. However, the roles of SA in the renewal of intestinal epithelial cells remain unclear. Methods and Results: In the present study, we found that 0.01-0.1 mM SA promoted IPEC-J2 cell differentiation and did not affect IPEC-J2 cell viability. In addition, the results showed that the viability of IPEC-J2 cells was inhibited by SA in a time- and dose-dependent manner at high concentrations. Flow cytometry and western blot analysis suggested that SA induced apoptosis, autophagy and ER stress in cells. In addition, the amounts of triglyceride were significantly increased upon challenge with SA. Moreover, the decrease in the viability of cells induced by SA could be attenuated by 4-PBA, an inhibitor of ER stress. Conclusion: In summary, SA accelerated IPEC-J2 cell differentiation at 0.01-0.1 mM. Furthermore, SA induced IPEC-J2 cell apoptosis and autophagy by causing ER stress.

scholarly journals Lipid-Induced Endoplasmic Reticulum Stress in Liver Cells Results in Two Distinct Outcomes: Adaptation with Enhanced Insulin Signaling or Insulin Resistance

Endocrinology ◽  
2012 ◽  
Vol 153 (5) ◽  
pp. 2164-2177 ◽  
Author(s):  
Caroline S. Achard ◽  
D. Ross Laybutt
Keyword(s):  
Insulin Resistance ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Insulin Signaling ◽  
Hepg2 Cells ◽  
Glycogen Synthesis ◽  
Liver Cells ◽  
Dependent Manner ◽  
Akt Phosphorylation ◽  
High Level

Chronically elevated fatty acids contribute to insulin resistance through poorly defined mechanisms. Endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) have been implicated in lipid-induced insulin resistance. However, the UPR is also a fundamental mechanism required for cell adaptation and survival. We aimed to distinguish the adaptive and deleterious effects of lipid-induced ER stress on hepatic insulin action. Exposure of human hepatoma HepG2 cells or mouse primary hepatocytes to the saturated fatty acid palmitate enhanced ER stress in a dose-dependent manner. Strikingly, exposure of HepG2 cells to prolonged mild ER stress activation induced by low levels of thapsigargin, tunicamycin, or palmitate augmented insulin-stimulated Akt phosphorylation. This chronic mild ER stress subsequently attenuated the acute stress response to high-level palmitate challenge. In contrast, exposure of HepG2 cells or hepatocytes to severe ER stress induced by high levels of palmitate was associated with reduced insulin-stimulated Akt phosphorylation and glycogen synthesis, as well as increased expression of glucose-6-phosphatase. Attenuation of ER stress using chemical chaperones (trimethylamine N-oxide or tauroursodeoxycholic acid) partially protected against the lipid-induced changes in insulin signaling. These findings in liver cells suggest that mild ER stress associated with chronic low-level palmitate exposure induces an adaptive UPR that enhances insulin signaling and protects against the effects of high-level palmitate. However, in the absence of chronic adaptation, severe ER stress induced by high-level palmitate exposure induces deleterious UPR signaling that contributes to insulin resistance and metabolic dysregulation.

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