Bax and Bak jointly control survival and dampen the early unfolded protein response in pancreatic β-cells under glucolipotoxic stress

Β Cells ◽

Β Cell ◽

Pancreatic Β Cells ◽

Unfolded Protein ◽

ABSTRACTER stress and apoptosis contribute to the loss of pancreatic β-cells under the pro-diabetic conditions of glucolipotoxicity. Although activation of the canonical pathway of intrinsic apoptosis is known to require Bax and Bak, their individual and combined involvement in glucolipotoxic β-cell death have not been demonstrated. It has also remained an open question if Bax and Bak in β-cells have non-apoptotic roles in mitochondrial function and ER stress signaling, as suggested in other cell types. Using mice with individual or combined β-cell deletion of Bax and Bak, we demonstrated that glucolipotoxic β-cell death in vitro happens in sequential stages; first via non-apoptotic mechanisms and later by apoptosis, which Bax and Bak were redundant in triggering. In contrast, they had non-redundant roles in mediating staurosporine-induced β-cell apoptosis. We further established that Bax and Bak do not affect normal glucose-stimulated β-cell Ca2+ responses, insulin secretion, or in vivo glucose tolerance. Finally, our experiments revealed that Bax and Bak together dampen the unfolded protein response in β-cells during the early stages of chemical- or glucolipotoxicity-induced ER stress. These findings identify novel roles of the canonical apoptosis machinery in modulating stress signals that are important for the pathobiology of β-cells in diabetes.

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

Journal of Endocrinology ◽

10.1677/joe-06-0148 ◽

2007 ◽

Vol 193 (1) ◽

pp. 65-74 ◽

Cited By ~ 70

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.

Coxsackievirus B Tailors the Unfolded Protein Response to Favour Viral Amplification in Pancreatic β Cells

Journal of Innate Immunity ◽

10.1159/000496034 ◽

2019 ◽

Vol 11 (4) ◽

pp. 375-390 ◽

Cited By ~ 5

Author(s):

Maikel L. Colli ◽

Flavia M. Paula ◽

Lorella Marselli ◽

Piero Marchetti ◽

Merja Roivainen ◽

...

Keyword(s):

Cell Death ◽

Er Stress ◽

Pancreatic Β Cell ◽

Β Cells ◽

Β Cell ◽

Unfolded Protein ◽

Islet Inflammation ◽

Type 1 diabetes (T1D) is an autoimmune disease characterized by islet inflammation and progressive pancreatic β cell destruction. The disease is triggered by a combination of genetic and environmental factors, but the mechanisms leading to the triggering of early innate and late adaptive immunity and consequent progressive pancreatic β cell death remain unclear. The insulin-producing β cells are active secretory cells and are thus particularly sensitive to endoplasmic reticulum (ER) stress. ER stress plays an important role in the pathologic pathway leading to autoimmunity, islet inflammation, and β cell death. We show here that group B coxsackievirus (CVB) infection, a putative causative factor for T1D, induces a partial ER stress in rat and human β cells. The activation of the PERK/ATF4/CHOP branch is blunted while the IRE1α branch leads to increased spliced XBP1 expression and c-Jun N-terminal kinase (JNK) activation. Interestingly, JNK1 activation is essential for CVB amplification in both human and rat β cells. Furthermore, a chemically induced ER stress preceding viral infection increases viral replication, in a process dependent on IRE1α activation. Our findings show that CVB tailors the unfolded protein response in β cells to support their replication, preferentially triggering the pro-viral IRE1α/XBP1s/JNK1 pathway while blocking the pro-apoptotic PERK/ATF4/CHOP pathway.

Endoplasmic reticulum stress and the unfolded protein response in pancreatic islet inflammation

Journal of Molecular Endocrinology ◽

10.1530/jme-15-0306 ◽

2016 ◽

Vol 57 (1) ◽

pp. R1-R17 ◽

Cited By ~ 31

Author(s):

Kira Meyerovich ◽

Fernanda Ortis ◽

Florent Allagnat ◽

Alessandra K Cardozo

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Diabetic Patients ◽

Β Cells ◽

Β Cell ◽

Unfolded Protein ◽

Islet Inflammation ◽

Insulin-secreting pancreatic β-cells are extremely dependent on their endoplasmic reticulum (ER) to cope with the oscillatory requirement of secreted insulin to maintain normoglycemia. Insulin translation and folding rely greatly on the unfolded protein response (UPR), an array of three main signaling pathways designed to maintain ER homeostasis and limit ER stress. However, prolonged or excessive UPR activation triggers alternative molecular pathways that can lead to β-cell dysfunction and apoptosis. An increasing number of studies suggest a role of these pro-apoptotic UPR pathways in the downfall of β-cells observed in diabetic patients. Particularly, the past few years highlighted a cross talk between the UPR and inflammation in the context of both type 1 (T1D) and type 2 diabetes (T2D). In this article, we describe the recent advances in research regarding the interplay between ER stress, the UPR, and inflammation in the context of β-cell apoptosis leading to diabetes.

A Novel Transcription Factor, ERD15 (Early Responsive to Dehydration 15), Connects Endoplasmic Reticulum Stress with an Osmotic Stress-induced Cell Death Signal

Journal of Biological Chemistry ◽

10.1074/jbc.m111.233494 ◽

2011 ◽

Vol 286 (22) ◽

pp. 20020-20030 ◽

Cited By ~ 29

Author(s):

Murilo S. Alves ◽

Pedro A. B. Reis ◽

Silvana P. Dadalto ◽

Jerusa A. Q. A. Faria ◽

Elizabeth P. B. Fontes ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Cell Death ◽

Transcription Factor ◽

Osmotic Stress ◽

Er Stress ◽

Unfolded Protein ◽

Eukaryotic Organisms ◽

As in all other eukaryotic organisms, endoplasmic reticulum (ER) stress triggers the evolutionarily conserved unfolded protein response in soybean, but it also communicates with other adaptive signaling responses, such as osmotic stress-induced and ER stress-induced programmed cell death. These two signaling pathways converge at the level of gene transcription to activate an integrated cascade that is mediated by N-rich proteins (NRPs). Here, we describe a novel transcription factor, GmERD15 (Glycine max Early Responsive to Dehydration 15), which is induced by ER stress and osmotic stress to activate the expression of NRP genes. GmERD15 was isolated because of its capacity to stably associate with the NRP-B promoter in yeast. It specifically binds to a 187-bp fragment of the NRP-B promoter in vitro and activates the transcription of a reporter gene in yeast. Furthermore, GmERD15 was found in both the cytoplasm and the nucleus, and a ChIP assay revealed that it binds to the NRP-B promoter in vivo. Expression of GmERD15 in soybean protoplasts activated the NRP-B promoter and induced expression of the NRP-B gene. Collectively, these results support the interpretation that GmERD15 functions as an upstream component of stress-induced NRP-B-mediated signaling to connect stress in the ER to an osmotic stress-induced cell death signal.

Unfolded Protein Response and Crohn’s Diseases: A Molecular Mechanism of Wound Healing in the Gut

10.20944/preprints202012.0578.v2 ◽

2021 ◽

Author(s):

Chao Li

Keyword(s):

Er Stress ◽

Immune Cell ◽

Macrophage Polarization ◽

Intestinal Epithelial ◽

Unfolded Protein ◽

Endoplasmic reticulum (ER) stress triggers a series of signaling and transcriptional events termed the unfolded protein response (UPR). Severe ER stress is associated with the development of fibrosis in different organs including lung, liver, kidney, heart, and intestine. ER stress is an essential response of epithelial and immune cells in the pathogenesis of inflammatory bowel disease (IBD) including Crohn’s disease. Intestinal epithelial cells are susceptible to ER stress-mediated damage due to secretion of a large amount of proteins that are involved in mucosal defense. In other cells, ER stress is linked to myofibroblast activation, extracellular matrix production, macrophage polarization, and immune cell differentiation. This review focuses on the role of UPR in the pathogenesis in IBD from an immunologic perspective. The roles of macrophage and mesenchymal cells in the UPR from in vitro and in vivo animal models are discussed. The links between ER stress and other signaling pathways such as senescence and autophagy are introduced. Recent advances in the understanding of the epigenetic regulation of UPR signaling are also updated here. The future directions of development of the UPR research and therapeutic strategies to manipulate ER stress levels are also reviewed.

P09.14 Blocking counterregulation of unfolded protein response by targeted protein synthesis inhibition produces highly synergistic cell death in several cancer entities

Journal for ImmunoTherapy of Cancer ◽

10.1136/jitc-2020-itoc7.114 ◽

2020 ◽

Vol 8 (Suppl 2) ◽

pp. A59.1-A59

Author(s):

F Gsottberger ◽

C Meier ◽

S Petkovic ◽

L Mellenthin ◽

M Krumbholz ◽

...

Keyword(s):

Cell Death ◽

Protein Synthesis ◽

Therapeutic Window ◽

Protein Synthesis Inhibition ◽

Synthesis Inhibition ◽

Unfolded Protein ◽

BackgroundBecause tumor cells have high proliferation rates the demand for energy on the one hand and proteins on the other hand is high. In line, protein folding machinery of the ER is heavily used. 2-Deoxyglucose (2-DG) not only blocks energy synthesis by inhibiting glycolysis but also blocks synthesis of mannosyl leading to impaired N-linked glycosylation, accumulation of misfolded proteins, and increased unfolded protein response (UPR). However, due to compensatory events, UPR-induced apoptosis is hampered. Therefore, we combined 2-DG with targeted protein synthesis inhibition by immunotoxins, consisting of an antibody and pseudomonas exotoxin, to enhance UPR mediated cell death.Materials and MethodsEstablished cell lines and patient-derived B-ALL samples were treated in vitro with various protein synthesis inhibitors and UPR-inducers. Drug synergy was determined mathematically as fold-increase over additivity. Biochemical studies were performed using western blots. In vivo enhancement was tested using systemic xenograft models.ResultsThe combination of Moxetumomab and 2-DG achieved a two to nine-fold synergy in vitro. Synergy was abrogated by the addition of Mannose suggesting UPR as cause of synergistic cell death. Similarly, Moxetumomab enhanced UPR-inducers Bortezomib and tunicamycin and protein synthesis inhibition by cycloheximide and puromycin enhanced 2-DG suggesting a conserved mechanism. Using HB21, an immunotoxin targeting human transferrin-receptor, breast cancer, hepatocellular carcinoma, and glioblastoma were sensitized to 2-DG induced cell death. Biochemically, 2-DG increased XBP-1-cleavage, expression of pro-apoptotic CHOP and of anti-apoptotic BIP. Moxetumomab, however, blocked the upregulation of BIP while maintaining CHOP correlating with synergistic increase in PARP-cleavage and apoptosis. In two systemic mouse models, bone marrow (BM) lymphoma infiltration was not reduced by 2-DG or tunicamycin alone but was reduced after treatment with Moxetumomab alone by 5-fold in the JeKo-1 and by 16-fold in the Ramos model, respectively. The combination of Moxetumomab and 2-DG achieved a three-fold synergy in the JeKo-1 model and achieved MRD-negative BM status in the Ramos model. Against patient-derived B-ALL of the Burkitt’s type, 2-DG and Moxetumomab were up to 5-fold more active in vitro and up to 7-fold more active in mouse xenografts in vivo.ConclusionsCell death after persisting unfolded protein response is synergistically enhanced by tumor-cell specific inhibition of protein synthesis against four distinct tumor entities at physiologically achievable concentrations. Our approach of immunotoxin-induced targeted protein synthesis inhibition opens a novel, so far undescribed therapeutic window which may warrant clinical evaluation.Disclosure InformationF. Gsottberger: None. C. Meier: None. S. Petkovic: None. L. Mellenthin: None. M. Krumbholz: None. M. Metzler: None. A. Mackensen: None. F. Müller: None.

Dominant negative FADD dissipates the proapoptotic signalosome of the unfolded protein response in diabetic embryopathy

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00215.2015 ◽

2015 ◽

Vol 309 (10) ◽

pp. E861-E873 ◽

Cited By ~ 15

Author(s):

Fang Wang ◽

Hongbo Weng ◽

Michael J. Quon ◽

Jingwen Yu ◽

Jian-Ying Wang ◽

...

Keyword(s):

Er Stress ◽

High Glucose ◽

Dominant Negative ◽

Caspase 8 ◽

Death Domain ◽

Unfolded Protein ◽

Endoplasmic reticulum (ER) stress and caspase 8-dependent apoptosis are two interlinked causal events in maternal diabetes-induced neural tube defects (NTDs). The inositol-requiring enzyme 1α (IRE1α) signalosome mediates the proapoptotic effect of ER stress. Diabetes increases tumor necrosis factor receptor type 1R-associated death domain (TRADD) expression. Here, we revealed two new unfolded protein response (UPR) regulators, TRADD and Fas-associated protein with death domain (FADD). TRADD interacted with both the IRE1α-TRAF2-ASK1 complex and FADD. In vivo overexpression of a FADD dominant negative (FADD-DN) mutant lacking the death effector domain disrupted diabetes-induced IRE1α signalosome and suppressed ER stress and caspase 8-dependent apoptosis, leading to NTD prevention. FADD-DN abrogated ER stress markers and blocked the JNK1/2-ASK1 pathway. Diabetes-induced mitochondrial translocation of proapoptotic Bcl-2 members mitochondrial dysfunction and caspase cleavage were also alleviated by FADD-DN. In vitro TRADD overexpression triggered UPR and ER stress before manifestation of caspase 3 and caspase 8 cleavage and apoptosis. FADD-DN overexpression repressed high glucose- or TRADD overexpression-induced IRE1α phosphorylation, its downstream proapoptotic kinase activation and endonuclease activities, and apoptosis. FADD-DN also attenuated tunicamycin-induced UPR and ER stress. These findings suggest that TRADD participates in the IRE1α signalosome and induces UPR and ER stress and that the association between TRADD and FADD is essential for diabetes- or high glucose-induced UPR and ER stress.

Unfolded Protein Response and Crohn’s Diseases: A Molecular Mechanism of Wound Healing in the Gut

Gastrointestinal Disorders ◽

10.3390/gidisord3010004 ◽

2021 ◽

Vol 3 (1) ◽

pp. 31-43

Author(s):

Chao Li

Keyword(s):

Er Stress ◽

Immune Cell ◽

Macrophage Polarization ◽

Intestinal Epithelial ◽

Unfolded Protein ◽

Endoplasmic reticulum (ER) stress triggers a series of signaling and transcriptional events termed the unfolded protein response (UPR). Severe ER stress is associated with the development of fibrosis in different organs, including lung, liver, kidney, heart, and intestine. ER stress is an essential response of epithelial and immune cells in the pathogenesis of Inflammatory Bowel Disease (IBD), including Crohn’s disease (CD). Intestinal epithelial cells are susceptible to ER stress-mediated damage due to secretion of a large amount of proteins that are involved in mucosal defense. In other cells, ER stress is linked to myofibroblast activation, extracellular matrix production, macrophage polarization, and immune cell differentiation. This review focuses on the role of the UPR in the pathogenesis in IBD from an immunologic perspective. The roles of macrophage and mesenchymal cells in the UPR from in vitro and in vivo animal models are discussed. The links between ER stress and other signaling pathways, such as senescence and autophagy, are introduced. Recent advances in the understanding of the epigenetic regulation of the UPR signaling are also updated here. The future directions of development of the UPR research and therapeutic strategies to manipulate ER stress levels are also reviewed.

The Role of Mitochondrial Dysfunction and ER Stress in TDP-43 and C9ORF72 ALS

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.653688 ◽

2021 ◽

Vol 15 ◽

Author(s):

Ruxandra Dafinca ◽

Paola Barbagallo ◽

Kevin Talbot

Keyword(s):

Er Stress ◽

Mitochondrial Dysfunction ◽

Nucleocytoplasmic Transport ◽

Cellular Processes ◽

Unfolded Protein ◽

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the motor system with complex determinants, including genetic and non-genetic factors. Despite this heterogeneity, a key pathological signature is the mislocalization and aggregation of specific proteins in the cytoplasm, suggesting that convergent pathogenic mechanisms focusing on disturbances in proteostasis are important in ALS. In addition, many cellular processes have been identified as potentially contributing to disease initiation and progression, such as defects in axonal transport, autophagy, nucleocytoplasmic transport, ER stress, calcium metabolism, the unfolded protein response and mitochondrial function. Here we review the evidence from in vitro and in vivo models of C9ORF72 and TDP-43-related ALS supporting a central role in pathogenesis for endoplasmic reticulum stress, which activates an unfolded protein response (UPR), and mitochondrial dysfunction. Disruption in the finely tuned signaling between the ER and mitochondria through calcium ions may be a crucial trigger of mitochondrial deficits and initiate an apoptotic signaling cascade, thus acting as a point of convergence for multiple upstream disturbances of cellular homeostasis and constituting a potentially important therapeutic target.

MANF regulates unfolded protein response and neuronal survival through its ER-located receptor IRE1α

10.1101/2020.09.22.307744 ◽

2020 ◽

Author(s):

Vera Kovaleva ◽

Li-Ying Yu ◽

Larisa Ivanova ◽

Jinhan Nam ◽

Ave Eesmaa ◽

...

Keyword(s):

Er Stress ◽

Neuronal Cell ◽

Direct Interaction ◽

Cell Types ◽

Dopamine Neurons ◽

Unfolded Protein ◽

AbstractMesencephalic astrocyte-derived neurotrophic factor (MANF) is an endoplasmic reticulum (ER)-located protein with cytoprotective effects in numerous cell types in vitro and in models of neurodegeneration and diabetes in vivo. So far, the exact mode of its action has remained elusive and plasma membrane or ER-located receptors of MANF have not been identified. We have found that MANF can directly interact with transmembrane unfolded protein response (UPR) receptor IRE1α and compete with the major ER chaperone BiP (GRP78) for the interaction with IRE1α. With lower affinities MANF can also interact with other UPR receptors, PERK and ATF6. Using molecular modeling and mutagenesis analysis, we have identified the exact structural MANF regions involved in its binding to the luminal domain of IRE1α. MANF attenuates UPR signaling by decreasing IRE1α oligomerization and IRE1α phosphorylation. MANF mutant deficient in IRE1α binding cannot regulate IRE1α oligomerization and fails to protect neurons from ER stress induced death. Importantly, we found that MANF-IRE1α interaction is also crucial for the survival promoting action of MANF for dopamine neurons in an animal model of Parkinson’s disease. Our data reveal a novel mechanism of IRE1α regulation during ER stress and demonstrate the intracellular mode of action of MANF as a modulator of UPR and neuronal cell survival through the direct interaction with IRE1α and regulation of its activity. Furthermore, our data explain why MANF in contrast to other growth factors has no effects on naive cells and rescues only ER stressed or injured cells.