scholarly journals Endoplasmic reticulum stress induces Wfs1 gene expression in pancreatic β-cells via transcriptional activation

2005 ◽  
Vol 153 (1) ◽  
pp. 167-176 ◽  
Author(s):  
Kohei Ueda ◽  
June Kawano ◽  
Komei Takeda ◽  
Toshiaki Yujiri ◽  
Katsuya Tanabe ◽  
...  
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Stress Responses ◽  
Gene Promoter ◽  
Luciferase Reporter ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Min6 Cells ◽  
Insulinoma Cells

Objective: The WFS1 gene encodes an endoplasmic reticulum (ER) membrane-embedded protein. Homozygous WFS1 gene mutations cause Wolfram syndrome, characterized by insulin-deficient diabetes mellitus and optic atropy. Pancreatic β-cells are selectively lost from the patient’s islets. ER localization suggests that WFS1 protein has physiological functions in membrane trafficking, secretion, processing and/or regulation of ER calcium homeostasis. Disturbances or overloading of these functions induces ER stress responses, including apoptosis. We speculated that WFS1 protein might be involved in these ER stress responses. Design and methods: Islet expression of the Wfs1 protein was analyzed immunohistochemically. Induction of Wfs1 upon ER stress was examined by Northern and Western blot analyses using three different models: human skin fibroblasts, mouse pancreatic β-cell-derived MIN6 cells, and Akita mouse-derived Ins2 96Y/Y insulinoma cells. The human WFS1 gene promoter-luciferase reporter analysis was also conducted. Result: Islet β-cells were the major site of Wfs1 expression. This expression was also found in δ-cells, but not in α-cells. WFS1 expression was transcriptionally up-regulated by ER stress-inducing chemical insults. Treatment of fibroblasts and MIN6 cells with thapsigargin or tunicamycin increased WFS1 mRNA. WFS1 protein also increased in response to thapsigargin treatment in these cells. WFS1 gene expression was also increased in Ins2 96Y/Y insulinoma cells. In these cells, ER stress was intrinsically induced by mutant insulin expression. The WFS1 gene promoter-luciferase reporter system revealed that the human WFS1 promoter was activated by chemically induced ER stress in MIN6 cells, and that the promoter was more active in Ins2 96Y/Y cells than Ins2 wild/wild cells. Conclusion: Wfs1 expression, which is localized to β- and δ-cells in pancreatic islets, increases in response to ER stress, suggesting a functional link between Wfs1 and ER stress.

scholarly journals The Orphan Nuclear Receptor NR4A1 Protects Pancreatic β-Cells from Endoplasmic Reticulum (ER) Stress-mediated Apoptosis

2015 ◽  
Vol 290 (34) ◽  
pp. 20687-20699 ◽  
Author(s):  
Cong Yu ◽  
Shang Cui ◽  
Chen Zong ◽  
Weina Gao ◽  
Tongfu Xu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Survivin Promoter ◽  
Min6 Cells ◽  
Chop Expression ◽  
Mouse Islets

The role of NR4A1 in apoptosis is controversial. Pancreatic β-cells often face endoplasmic reticulum (ER) stress under adverse conditions such as high free fatty acid (FFA) concentrations and sustained hyperglycemia. Severe ER stress results in β-cell apoptosis. The aim of this study was to analyze the role of NR4A1 in ER stress-mediated β-cell apoptosis and to characterize the related mechanisms. We confirmed that upon treatment with the ER stress inducers thapsigargin (TG) or palmitic acid (PA), the mRNA and protein levels of NR4A1 rapidly increased in both MIN6 cells and mouse islets. NR4A1 overexpression in MIN6 cells conferred resistance to cell loss induced by TG or PA, as assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and TUNEL assays indicated that NR4A1 overexpression also protected against ER stress-induced apoptosis. This conclusion was further confirmed by experiments exploiting siRNA to knockdown NR4A1 expression in MIN6 cells or exploiting NR4A1 knock-out mice. NR4A1 overexpression in MIN6 cells reduced C/EBP homologous protein (CHOP) expression and Caspase3 activation induced by TG or PA. NR4A1 overexpression in MIN6 cells or mouse islets resulted in Survivin up-regulation. A critical regulatory element was identified in Survivin promoter (−1872 bp to −1866 bp) with a putative NR4A1 binding site; ChIP assays demonstrated that NR4A1 physically associates with the Survivin promoter. In conclusion, NR4A1 protects pancreatic β-cells against ER stress-mediated apoptosis by up-regulating Survivin expression and down-regulating CHOP expression, which we termed as “positive and negative regulation.”

Sirtuin-3 (SIRT3) protects pancreatic β-cells from endoplasmic reticulum (ER) stress-induced apoptosis and dysfunction

2016 ◽  
Vol 420 (1-2) ◽  
pp. 95-106 ◽  
Author(s):  
Hao-Hao Zhang ◽  
Xiao-Jun Ma ◽  
Li-Na Wu ◽  
Yan-Yan Zhao ◽  
Peng-Yu Zhang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Sirtuin 3 ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Induced Apoptosis

scholarly journals Original article. Transcription factors regulate Forkhead box O1 gene promoter activity in pancreatic β-cells

2011 ◽  
Vol 5 (4) ◽  
pp. 433-439 ◽  
Author(s):  
Ying Luo ◽  
Yan Lin ◽  
Xiao Han
Keyword(s):  
Transcription Factors ◽  
Promoter Activity ◽  
Screening Method ◽  
Gene Promoter ◽  
Luciferase Reporter ◽  
Upstream Region ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Forkhead Box ◽  
Foxo1 Gene

Abstract Background: Transcription factors of the Forkhead box O (Fox O) family have important roles in cellular proliferation, apoptosis, differentiation, and stress resistance. In pancreatic β-cells, FoxO1 protein plays an important role in β-cells development. The molecular mechanism of transcriptional regulation of basal FoxO1 gene expression in pancreatic β-cells is not fully understood. Objectives: Explore the potential transcription factors regulating FoxO1 promoter activity using pancreatic β-cell line (RINm5F cells) Methods: Promoter screening method, luciferase reporter gene analysis, transient expression assay system, and deletion analysis of a -974/-18 bp 5’ upstream region of the mouse FoxO1 gene were used in this study. Results: An inhibition domain (-974/-321) and an activation domain (-321/-18) was identified through deletion analysis of a -974/-18 bp 5’ upstream region of the mouse FoxO1 gene. Using the promoter screening method, several transcription factors were selected. Luciferase reporter studies showed that these factors could regulate FoxO1 promoter activity in RINm5F cells. Among these factors, cAMP response-element binding protein (CREB) could positively regulate FoxO1 promoter activity. Signal transducer and activator of transcription 1 (STAT1) played a negative role on FoxO1 promoter. In addition, ETS oncogene family member Elk-1 did not affect the FoxO1 promoter activity. Conclusion: Two transcription factors (CREB and STAT1) could effectively regulate the mouse FoxO1 gene promoter activity.

A novel secretagogin/ATF4 pathway is involved in oxidized LDL-induced endoplasmic reticulum stress and islet β-cell apoptosis

2020 ◽  
Author(s):  
Li Wu ◽  
Yuncheng Lv ◽  
Ying Lv ◽  
Sunmin Xiang ◽  
Zhibo Zhao ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Er Stress ◽  
Cell Apoptosis ◽  
Initiation Factor ◽  
Β Cells ◽  
Β Cell ◽  
Immunoprecipitation Assay ◽  
Min6 Cells ◽  
Stress Markers

Abstract Excessive accumulation of cholesterol in β cells initiates endoplasmic reticulum (ER) stress and associated apoptosis. We have reported that excessive uptake of cholesterol by MIN6 cells decreases the expression of secretagogin (SCGN) and then attenuates insulin secretion. Here, we aimed to determine whether cholesterol-induced SCGN decrease is involved in the modulation of ER stress and apoptosis in pancreatic β cells. In this study, MIN6 cells were treated with oxidized low-density lipoprotein (ox-LDL) for 24 h, and then intracellular lipid droplets and cell apoptosis were quantified, and SCGN and ER stress markers were identified by western blot analysis. Furthermore, small interfer RNA (siRNA)-mediated SCGN knockdown and recombinant plasmid-mediated SCGN restoration experiments were performed to confirm the role of SCGN in ER stress and associated cell apoptosis. Finally, the interaction of SCGN with ATF4 was computationally predicted and then validated by a co-immunoprecipitation assay. We found that ox-LDL treatment increased the levels of ER stress markers, such as phosphorylated protein kinase-like endoplasmic reticulum kinase, phosphorylated eukaryotic initiation factor 2 alpha, activating transcription factor 4 (ATF4), and transcription factor CCAAT-enhancer-binding protein homologous protein, and promoted MIN6 cell apoptosis; in addition, the expression of SCGN was downregulated. siRNA-mediated SCGN knockdown exacerbated β-cell ER stress by increasing ATF4 expression. Pretreatment of MIN6 cells with the recombinant SCGN partly antagonized ox-LDL-induced ER stress and apoptosis. Furthermore, a co-immunoprecipitation assay revealed an interaction between SCGN and ATF4 in MIN6 cells. Taken together, these results demonstrated that pancreatic β-cell apoptosis induced by ox-LDL treatment can be attributed, in part, to an SCGN/ATF4-dependent ER stress response.

scholarly journals Protection of pancreatic β-cells by exendin-4 may involve the reduction of endoplasmic reticulum stress; in vivo and in vitro studies

2007 ◽  
Vol 193 (1) ◽  
pp. 65-74 ◽  
Author(s):  
Shin Tsunekawa ◽  
Naoki Yamamoto ◽  
Katsura Tsukamoto ◽  
Yuji Itoh ◽  
Yukiko Kaneko ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Er Stress ◽  
Islet Cells ◽  
Binding Protein ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells

The aim of this study was to investigate the in vivo and in vitro effects of exendin-4, a potent glucagon-like peptide 1 agonist, on the protection of the pancreatic β-cells against their cell death. In in vivo experiments, we used β-cell-specific calmodulin-overexpressing mice where massive apoptosis takes place in their β-cells, and we examined the effects of chronic treatment with exendin-4. Chronic and s.c. administration of exendin-4 reduced hyperglycemia. The treatment caused significant increases of the insulin contents of the pancreas and islets, and retained the insulin-positive area. Dispersed transgenic islet cells lived only shortly, and several endoplasmic reticulum (ER) stress-related molecules such as immunoglobulin-binding protein (Bip), inositol-requiring enzyme-1α, X-box-binding protein-1 (XBP-1), RNA-activated protein kinase-like endoplasmic reticulum kinase, activating transcription factor-4, and C/EBP-homologous protein (CHOP) were more expressed in the transgenic islets. We also found that the spliced form of XBP-1, a marker of ER stress, was also increased in β-cell-specific calmodulin-overexpressing transgenic islets. In the quantitative real-time PCR analyses, the expression levels of Bip and CHOP were reduced in the islets from the transgenic mice treated with exendin-4. These findings suggest that excess of ER stress occurs in the transgenic β-cells, and the suppression of ER stress and resultant protection against cell death may be involved in the anti-diabetic effects of exendin-4.

scholarly journals γ-Oryzanol Protects Pancreatic β-Cells Against Endoplasmic Reticulum Stress in Male Mice

Endocrinology ◽  
2015 ◽  
Vol 156 (4) ◽  
pp. 1242-1250 ◽  
Author(s):  
Chisayo Kozuka ◽  
Sumito Sunagawa ◽  
Rei Ueda ◽  
Moritake Higa ◽  
Hideaki Tanaka ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Insulin Secretion ◽  
Er Stress ◽  
High Fat Diet ◽  
Diabetic Mice ◽  
High Fat ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Glucose Stimulated Insulin Secretion

Abstract Endoplasmic reticulum (ER) stress is profoundly involved in dysfunction of β-cells under high-fat diet and hyperglycemia. Our recent study in mice showed that γ-oryzanol, a unique component of brown rice, acts as a chemical chaperone in the hypothalamus and improves feeding behavior and diet-induced dysmetabolism. However, the entire mechanism whereby γ-oryzanol improves glucose metabolism throughout the body still remains unclear. In this context, we tested whether γ-oryzanol reduces ER stress and improves function and survival of pancreatic β-cells using murine β-cell line MIN6. In MIN6 cells with augmented ER stress by tunicamycin, γ-oryzanol decreased exaggerated expression of ER stress-related genes and phosphorylation of eukaryotic initiation factor-2α, resulting in restoration of glucose-stimulated insulin secretion and prevention of apoptosis. In islets from high-fat diet-fed diabetic mice, oral administration of γ-oryzanol improved glucose-stimulated insulin secretion on following reduction of exaggerated ER stress and apoptosis. Furthermore, we examined the impact of γ-oryzanol on low-dose streptozotocin-induced diabetic mice, where exaggerated ER stress and resultant apoptosis in β-cells were observed. Also in this model, γ-oryzanol attenuated mRNA level of genes involved in ER stress and apoptotic signaling in islets, leading to amelioration of glucose dysmetabolism. Taken together, our findings demonstrate that γ-oryzanol directly ameliorates ER stress-induced β-cell dysfunction and subsequent apoptosis, highlighting usefulness of γ-oryzanol for the treatment of diabetes mellitus.

scholarly journals AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells

2020 ◽  
Vol 40 (11) ◽  
Author(s):  
Zhechu Peng ◽  
Richa Aggarwal ◽  
Ni Zeng ◽  
Lina He ◽  
Eileen X. Stiles ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Adaptive Response ◽  
Metabolic Stress ◽  
Cell Phenotype ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Α Subunit ◽  
Growth And Survival

ABSTRACT Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.

scholarly journals NR4A1 enhances MKP7 expression to diminish JNK activation induced by ROS or ER-stress in pancreatic β cells for surviving

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Ze-qing Pu ◽  
Tian-fu Yu ◽  
Dong Liu ◽  
Cheng-wen Jin ◽  
Esha Sadiq ◽  
...  
Keyword(s):  
Er Stress ◽  
Binding Sites ◽  
Mrna Level ◽  
Wild Type ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Min6 Cells ◽  
Adverse Conditions ◽  
Chronic Hyperglycemia ◽  
Jnk Activation

AbstractUnder adverse conditions, such as sustained or chronic hyperglycemia or hyperlipidemia, ROS (reactive oxygen species) or/and ER-stress (endoplasmic reticulum stress) will be induced in pancreatic β cells. ROS or ER-stress damages β-cells even leads to apoptosis. Previously we found ROS or ER-stress resulted in JNK activation in β cells and overexpressing NR4A1 in MIN6 cells reduced JNK activation via modulating cbl-b expression and subsequent degrading the upstream JNK kinase (MKK4). To search other possible mechanisms, we found the mRNA level and protein level of MKP7 (a phosphatase for phospho-JNK) were dramatic reduced in pancreatic β cells in the islets from NR4A1 KO mice compared with that from wild type mice. To confirm what we found in animals, we applied pancreatic β cells (MIN6 cells) and found that the expression of MKP7 was increased in NR4A1-overexpression MIN6 cells. We further found that knocking down the expression of MKP7 increased the p-JNK level in pancreatic β cells upon treatment with TG or H2O2. After that, we figured out that NR4A1 did enhance the transactivation of the MKP7 promoter by physical association with two putative binding sites. In sum, NR4A1 attenuates JNK phosphorylation incurred by ER-stress or ROS partially via enhancing MKP7 expression, potentially decreases pancreatic β cell apoptosis induced by ROS or ER-stress. Our finding provides a clue for diabetes prevention.

scholarly journals Testosterone Protects Against Glucotoxicity-Induced Apoptosis of Pancreatic β-Cells (INS-1) and Male Mouse Pancreatic Islets

Endocrinology ◽  
2013 ◽  
Vol 154 (11) ◽  
pp. 4058-4067 ◽  
Author(s):  
Wanthanee Hanchang ◽  
Namoiy Semprasert ◽  
Thawornchai Limjindaporn ◽  
Pa-thai Yenchitsomanus ◽  
Suwattanee Kooptiwut
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
High Glucose ◽  
Male Mouse ◽  
Glucose Medium ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Stress Markers ◽  
High Glucose Medium ◽  
Cells Cultured

Male hypogonadism associates with type 2 diabetes, and T can protect pancreatic β-cells from glucotoxicity. However, the protective mechanism is still unclear. This study thus aims to examine the antiapoptotic mechanism of T in pancreatic β cells cultured in high-glucose medium. T (0.0005–2 μg/mL) was added to INS-1 cells cultured in basal glucose or high-glucose media. Then cellular apoptosis, oxidative stress, and cell viability were measured. Endoplasmic reticulum (ER) stress markers and sensors and the antiapoptotic protein (B-cell lymphoma 2) were investigated by real-time PCR and Western blot analysis. ER stress markers were also measured in male mouse pancreatic islet cultured in similar conditions. T (0.05 and 0.5 μg/mL) did not have any effect on apoptosis and viability of INS-1 cells cultured in basal glucose medium, but it could reduce apoptosis and increase viability of INS-1 cells cultured in high-glucose medium. The protective effect of T is diminished by androgen receptor inhibitor. T (0.05 μg/mL) could significantly reduce nitrotyrosine levels, mRNA, and protein levels of the ER stress markers and sensor those that were induced when INS-1 cells were cultured in high-glucose medium. It could also significantly increase the survival proteins, sarco/endoplasmic reticulum Ca2+ ATPase-2, and B-cell lymphoma 2 in INS-1 cells cultured in the same conditions. Similarly, it could reduce ER stress markers and increase sarco/endoplasmic reticulum Ca2+ ATPase protein levels in male mouse pancreatic islets cultured in high-glucose medium. T can protect against male pancreatic β-cell apoptosis from glucotoxicity via the reduction of both oxidative stress and ER stress.

scholarly journals Hedgehog Signaling Regulation of Homeodomain Protein Islet Duodenum Homeobox-1 Expression in Pancreatic β-Cells*

Endocrinology ◽  
2001 ◽  
Vol 142 (3) ◽  
pp. 1033-1040 ◽  
Author(s):  
Melissa K. Thomas ◽  
Jee H. Lee ◽  
Naina Rastalsky ◽  
Joel F. Habener
Keyword(s):  
Gene Expression ◽  
Transcriptional Activation ◽  
Gene Promoter ◽  
Insulin Gene ◽  
Reporter Construct ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Insulin Promoter ◽  
Insulin Gene Expression ◽  
Hh Signaling

Abstract Insulin gene expression in pancreatic β-cells is regulated by signals from developmental morphogen proteins known as hedgehogs (Hhs). By analyzing 5′-deletion insulin promoter-reporter constructs in transient transfections of clonal INS-1 β-cells, we located activating Hh-responsive regions within the rat insulin I promoter that include the glucose-response elements Far (E2) and Flat (A2/A3). Activation of Hh signaling in INS-1 cells by ectopic Hh expression increased (and inhibition of Hh signaling with the Hh-specific inhibitor cyclopamine decreased) transcriptional activation of a multimerized FarFlat enhancer-reporter construct. In DNA-binding studies, nuclear extracts from INS-1 cells activated by ectopic Hh expression increased (and extracts from INS-1 cells treated with cyclopamine decreased) protein binding to a radiolabeled FarFlat oligonucleotide probe. An antiserum directed against the transcription factor islet duodenum homeobox-1 (IDX-1), a regulator of pancreas development and activator of the insulin gene promoter, attenuated the binding activity of Hh-responsive protein complexes. Nuclear IDX-1 protein levels on Western blots were increased by ectopic Hh expression, thereby providing a mechanism for Hh-mediated regulation of the insulin promoter. Addition of cyclopamine to INS-1 cells decreased IDX-1 messenger RNA expression. In transient transfections of a− 4.5-kb mouse IDX-1 promoter-reporter construct, ectopic Hh expression increased (and cyclopamine administration decreased) transcriptional activation of the IDX-1 promoter in a dose-dependent manner. Thus, the IDX-1 gene is a direct regulatory target of Hh signaling in insulin-producing pancreatic β-cells. We propose that Hh signaling activates the insulin gene promoter indirectly via the direct activation of IDX-1 expression. Because IDX-1 gene expression is essential for insulin gene expression, pancreatic β-cell development, and normal glucose homeostasis, our findings that Hh signaling regulates IDX-1 expression in the endocrine pancreas suggest possible novel therapeutic approaches for diabetes mellitus.

Sign in / Sign up

Export Citation Format

Share Document