Baicalein protects hippocampal neuronal HT22 cells from ER stress‐induced apoptosis by modulating unfolded protein responses‐associated proteins

Abstract Accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress and results in the activation of the unfolded protein response (UPR), which aims at restoring ER homeostasis. However, when the stress is too severe the UPR switches from being a pro-survival response to a pro-death one, and the molecular mechanisms underlying ER stress-mediated death have remained incompletely understood. In this study, we identified receptor interacting protein kinase 1 (RIPK1)—a kinase at the crossroad between life and death downstream of various receptors—as a new regulator of ER stress-induced death. We found that Ripk1-deficient MEFs are protected from apoptosis induced by ER stressors, which is reflected by reduced caspase activation and PARP processing. Interestingly, the pro-apoptotic role of Ripk1 is independent of its kinase activity, is not regulated by its cIAP1/2-mediated ubiquitylation, and does not rely on the direct regulation of JNK or CHOP, two reportedly main players in ER stress-induced death. Instead, we found that ER stress-induced apoptosis in these cells relies on death receptor-independent activation of caspase-8, and identified Ripk1 upstream of caspase-8. However, in contrast to RIPK1-dependent apoptosis downstream of TNFR1, we did not find Ripk1 associated with caspase-8 in a death-inducing complex upon unresolved ER stress. Our data rather suggest that RIPK1 indirectly regulates caspase-8 activation, in part via interaction with the ER stress sensor inositol-requiring protein 1 (IRE1).

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Effects of ER stress on unfolded protein responses, cell survival, and viral replication in primary effusion lymphoma

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2015.12.032 ◽

2016 ◽

Vol 469 (3) ◽

pp. 565-572 ◽

Cited By ~ 9

Author(s):

Zenpei Shigemi ◽

Yusuke Baba ◽

Naoko Hara ◽

Jumpei Matsuhiro ◽

Hiroki Kagawa ◽

...

Keyword(s):

Viral Replication ◽

Er Stress ◽

Cell Survival ◽

Primary Effusion Lymphoma ◽

Unfolded Protein Responses ◽

Unfolded Protein

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The unfolded protein response controls ER stress-induced apoptosis of lung epithelial cells through angiotensin generation

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00449.2015 ◽

2016 ◽

Vol 311 (5) ◽

pp. L846-L854 ◽

Cited By ~ 15

Author(s):

Hang Nguyen ◽

Bruce D. Uhal

Keyword(s):

Epithelial Cells ◽

Er Stress ◽

Unfolded Protein Response ◽

Cathepsin D ◽

Lung Epithelial Cells ◽

Chemical Chaperone ◽

Unfolded Protein ◽

Induced Apoptosis ◽

The Unfolded Protein Response ◽

Protein Response

Recent work from this laboratory showed that endoplasmic reticulum (ER) stress-induced apoptosis of alveolar epithelial cells (AECs) is regulated by the autocrine angiotensin (ANG)II/ANG1-7 system. The proteasome inhibitor MG132 or surfactant protein C (SP-C) BRICHOS domain mutation G100S induced apoptosis in human AECs by activating the proapoptotic cathepsin D and reducing antiapoptotic angiotensin converting enzyme-2 (ACE-2). This study tested the hypothesis that ER stress-induced apoptosis of human AECs might be mediated by influence of the unfolded protein response (UPR) on the autocrine ANGII/ANG1-7 system. A549 cells were challenged with MG132 or SP-C BRICHOS domain mutant G100S to induce ER stress and activation of UPR pathways. The results showed that either MG132 or G100S SP-C mutation activated all three canonical pathways of the UPR (IRE1/XBP1, ATF6, and PERK/eIF2α), which led to a significant increase in cathepsin D or in TACE (an ACE-2 ectodomain shedding enzyme) and eventually caused AEC apoptosis. However, ER stress-induced AEC apoptosis could be prevented by chemical chaperone or by UPR blockers. It is also suggested that ATF6 and IRE1 pathways might play important role in regulation of angiotensin system. These data demonstrate that ER stress induces apoptosis in human AECs through mediation of UPR pathways, which in turn regulate the autocrine ANGII/ANG1-7 system. They also demonstrated that ER stress-induced AEC apoptosis can be blocked by inhibition of UPR signaling pathways.

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Andrographolide Mitigates Unfolded Protein Response Pathway andApoptosis Involved in Chikungunya virus Infection

Combinatorial Chemistry & High Throughput Screening ◽

10.2174/1386207323999200818165029 ◽

2020 ◽

Vol 23 ◽

Author(s):

Swati Gupta ◽

KP Mishra ◽

Bhuvnesh Kumar ◽

SB Singh ◽

Lilly Ganju

Keyword(s):

Protein Expression ◽

Er Stress ◽

Unfolded Protein Response ◽

Chikungunya Virus ◽

Rna Virus ◽

Apoptosis Pathway ◽

Unfolded Protein ◽

Induced Apoptosis ◽

Protein Response ◽

Upr Pathway

Background: Chikungunya virus (CHIKV) is an arthropod-borne RNA virus which induces host endoplasmic reticulum (ER) stress by accumulating unfolded or misfolded proteins. ER stress activates the unfolded protein response (UPR) pathway to enable proper protein folding and maintain cellular homeostasis. There is no approved drug or vaccine available for CHIKV treatment, therefore, a pharmacological countermeasure is warranted for preventing CHIKV infection. Objective: With a view to find a treatment modality for chikungunya infection, “andrographolide”; a plant-derived diterpenoid with reported antiviral, anti-inflammatory and immunomodulatory effects, was used to investigate its role in chikungunya induced unfolded protein stress and apoptosis. Methods: Cells and supernatant collected on andrographolide and VER-155008; a GRP78 inhibitor, treatment in CHIKV infected and mock-infected THP-1 cells were tested for differential expression of UPR pathway proteins including GRP78, PERK, EIF-2α, IRE-1α, XBP-1 and ATF6. Further, the inflammasome and apoptosis pathway proteins i.e. caspase-1, caspase-3 and PARP were tested by immunoblotting and cytokines i.e. IL-1β, IL-6 and IFN-γ were tested by ELISA. Results: Andrographolide treatment in CHIKV infected THP-1 cells significantly reduced IRE1α and downstream spliced XBP1 protein expression. Further, CHIKV induced apoptosis and viral protein expression was also reduced on andrographolide treatment. A comparative analysis of andrographolide verses VER-155008, confirmed that andrographolide surpasses the effects of VER-155008 in suppressing the CHIKV induced ER stress. Conclusion: The study, therefore, confirms that andrographolide is a potential remedy for chikungunya infection and suppresses CHIKV induced ER stress and apoptosis.

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Dynamic Regulation of Mis-Folded N-CoR by Aberrant Protease and Its Implication in UPR-Induced Apoptosis of APL Cells.

Blood ◽

10.1182/blood.v108.11.4514.4514 ◽

2006 ◽

Vol 108 (11) ◽

pp. 4514-4514

Author(s):

Matiullah Khan

Keyword(s):

Er Stress ◽

Protein S ◽

Spectrometric Analysis ◽

Insoluble Protein ◽

Dynamic Regulation ◽

Paradoxical Response ◽

Unfolded Protein ◽

Folded Proteins ◽

Induced Apoptosis ◽

Protein Response

Abstract We have recently reported that accumulation of mis-folded N-CoR as insoluble protein aggregates in APL cells induces Endoplasmic Reticulum (ER) stress and activates unfolded protein response (UPR). Although, accumulation of mis-folded proteins is known to trigger UPR-induced cytotoxic cell death in several neurodegenerative disorders, APL cells are notably resistant to UPR-induced apoptosis. The molecular basis for the paradoxical response of APL cells to UPR is not known. Here we report that a glyco-protease, selectively expressed in APL cells, regulates APL cells’ response to UPR-induced apoptosis through processing of mis-folded N-CoR protein. Results show that mis-folded N-CoR is cleaved selectively in APL cells, and cellular extracts of APL cells and human primary APL cells contain activity that cleaves N-CoR protein. Purification and spectrometric analysis of N-CoR cleaving activity from an APL cell line reveals that it is a glycoprotein endopeptidase known as OSGEP. Furthermore, the cleavage of N-CoR in APL cells could be blocked by the broad-spectrum protease inhibitor, AEBSF, and by RNAi-mediated down-regulation of OSGEP expression. AEBSF selectively inhibits growth and promotes apoptosis of APL cells, possibly through a mechanism involving AEBSF-induced accumulation of insoluble N-CoR protein and by triggering ER stress. Taken together, these finding suggest that selective induction of protease activity in APL cells may represent a novel cytoprotective component of UPR, which could be exploited by tumor cells to survive the toxic insult of mis-folded protein(s).

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Curcumin abates hypoxia-induced oxidative stress based-ER stress-mediated cell death in mouse hippocampal cells (HT22) by controlling Prdx6 and NF-κB regulation

AJP Cell Physiology ◽

10.1152/ajpcell.00345.2012 ◽

2013 ◽

Vol 304 (7) ◽

pp. C636-C655 ◽

Cited By ~ 50

Author(s):

Bhavana Chhunchha ◽

Nigar Fatma ◽

Eri Kubo ◽

Prerana Rai ◽

Sanjay P. Singh ◽

...

Keyword(s):

Oxidative Stress ◽

Cell Death ◽

Er Stress ◽

Molecular Mechanisms ◽

Stress Proteins ◽

Ht22 Cells ◽

Peroxiredoxin 6 ◽

Homologous Protein ◽

Survival Signaling ◽

Induced Apoptosis

Oxidative stress and endoplasmic reticulum (ER) stress are emerging as crucial events in the etiopathology of many neurodegenerative diseases. While the neuroprotective contributions of the dietary compound curcumin has been recognized, the molecular mechanisms underlying curcumin's neuroprotection under oxidative and ER stresses remains elusive. Herein, we show that curcumin protects HT22 from oxidative and ER stresses evoked by the hypoxia (1% O2 or CoCl2 treatment) by enhancing peroxiredoxin 6 (Prdx6) expression. Cells exposed to CoCl2 displayed reduced expression of Prdx6 with higher reactive oxygen species (ROS) expression and activation of NF-κB with IκB phosphorylation. When NF-κB activity was blocked by using SN50, an inhibitor of NF-κB, or cells treated with curcumin, the repression of Prdx6 expression was restored, suggesting the involvement of NF-κB in modulating Prdx6 expression. These cells were enriched with an accumulation of ER stress proteins, C/EBP homologous protein (CHOP), GRP/78, and calreticulin, and had activated states of caspases 12, 9, and 3. Reinforced expression of Prdx6 in HT22 cells by curcumin reestablished survival signaling by reducing propagation of ROS and blunting ER stress signaling. Intriguingly, knockdown of Prdx6 by antisense revealed that loss of Prdx6 contributed to cell death by sustaining enhanced levels of ER stress-responsive proapoptotic proteins, which was due to elevated ROS production, suggesting that Prdx6 deficiency is a cause of initiation of ROS-mediated ER stress-induced apoptosis. We propose that using curcumin to reinforce the naturally occurring Prdx6 expression and attenuate ROS-based ER stress and NF-κB-mediated aberrant signaling improves cell survival and may provide an avenue to treat and/or postpone diseases associated with ROS or ER stress.

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The balance between adaptive and apoptotic unfolded protein responses regulates β-cell death under ER stress conditions through XBP1, CHOP and JNK

Molecular and Cellular Endocrinology ◽

10.1016/j.mce.2015.06.025 ◽

2015 ◽

Vol 413 ◽

pp. 189-201 ◽

Cited By ~ 52

Author(s):

Jeng Yie Chan ◽

Jude Luzuriaga ◽

Emma L. Maxwell ◽

Phillip K. West ◽

Mohammed Bensellam ◽

...

Keyword(s):

Cell Death ◽

Er Stress ◽

Stress Conditions ◽

Β Cell ◽

Unfolded Protein Responses ◽

Unfolded Protein

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Exploring the Role of Endoplasmic Reticulum Stress in Hepatocellular Carcinoma through the Mining of the Human Protein Atlas

Biology ◽

10.3390/biology10070640 ◽

2021 ◽

Vol 10 (7) ◽

pp. 640

Author(s):

Nataša Pavlović ◽

Femke Heindryckx

Keyword(s):

Endoplasmic Reticulum ◽

Er Stress ◽

Predictive Biomarkers ◽

Human Protein ◽

Disease Stage ◽

Unfolded Protein ◽

Human Protein Atlas ◽

Associated Proteins ◽

Protein Response

Endoplasmic reticulum (ER) stress and actors of unfolded protein response (UPR) have emerged as key hallmarks of hepatocarcinogenesis. Numerous reports have shown that the main actors in the UPR pathways are upregulated in HCC and contribute to the different facets of tumor initiation and disease progression. Furthermore, ER-stress inducers and inhibitors have shown success in preclinical HCC models. Despite the mounting evidence of the UPR’s involvement in HCC pathogenesis, it remains unclear how ER-stress components can be used safely and effectively as therapeutic targets or predictive biomarkers for HCC patients. In an effort to add a clinical context to these findings and explore the translational potential of ER-stress in HCC, we performed a systematic overview of UPR-associated proteins as predictive biomarkers in HCC by mining the Human Protein Atlas database. Aside from evaluating the prognostic value of these markers in HCC, we discussed their expression in relation to patient age, sex, ethnicity, disease stage, and tissue localization. We thereby identified 44 UPR-associated proteins as unfavorable prognostic markers in HCC. The expression of these markers was found to be higher in tumors compared to the stroma of the hepatic HCC patient tissues.

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The Drosophila metallopeptidase superdeath decouples apoptosis from the activation of the ER stress response

10.1101/620492 ◽

2019 ◽

Cited By ~ 1

Author(s):

Rebecca A.S. Palu ◽

Clement Y. Chow

Keyword(s):

Endoplasmic Reticulum ◽

Drosophila Melanogaster ◽

Stress Response ◽

Er Stress ◽

Unfolded Protein ◽

Er Stress Response ◽

Membrane Bound ◽

Induced Apoptosis ◽

The Unfolded Protein Response ◽

Protein Response

ABSTRACTEndoplasmic reticulum (ER) stress-induced apoptosis is a primary cause and modifier of degeneration in a number of genetic disorders. Understanding how genetic variation between individuals influences the ER stress response and subsequent activation of apoptosis could improve individualized therapies and predictions of outcomes for patients. In this study, we find that the uncharacterized, membrane-bound metallopeptidase CG14516 in Drosophila melanogaster, which we rename as SUPpressor of ER stress-induced DEATH (superdeath), plays a role in modifying ER stress-induced apoptosis. We demonstrate that loss of superdeath reduces apoptosis and degeneration in the Rh1G69D model of ER stress through the JNK signaling cascade. This effect on apoptosis occurs without altering the activation of the unfolded protein response (IRE1 and PERK), suggesting that the beneficial pro-survival effects of this response are intact. Furthermore, we show that superdeath functions epistatically upstream of CDK5, a known JNK-activated pro-apoptotic factor in this model of ER stress. We demonstrate that superdeath is not only a modifier of this particular model, but functions as a general modifier of ER stress-induced apoptosis across different tissues and ER stresses. Finally, we present evidence of Superdeath localization to the endoplasmic reticulum membrane. While similar in sequence to a number of human metallopeptidases found in the plasma membrane and ER membrane, its localization suggests that superdeath is orthologous to ERAP1/2 in humans. Together, this study provides evidence that superdeath is a link between stress in the ER and activation of cytosolic apoptotic pathways.SIGNIFICANCE STATEMENTGenetic diseases display a great deal of variability in presentation, progression, and overall outcomes. Much of this variability is caused by differences in genetic background among patients. One process that commonly modifies degenerative disease is the endoplasmic reticulum (ER) stress response. Understanding the genetic sources of variation in the ER stress response could improve individual diagnosis and treatment decisions. In this study, we characterized one such modifier in Drosophila melanogaster, the membrane-bound metallopeptidase CG14516 (superdeath). Loss of this enzyme suppresses a model of ER stress-induced degeneration by reducing cell death without altering the beneficial activation of the unfolded protein response. Our findings make superdeath and its orthologues attractive therapeutic targets in degenerative disease.

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Apelin-13 Inhibits Methylglyoxal-Induced Unfolded Protein Responses and Endothelial Dysfunction via Regulating AMPK Pathway

International Journal of Molecular Sciences ◽

10.3390/ijms21114069 ◽

2020 ◽

Vol 21 (11) ◽

pp. 4069 ◽

Cited By ~ 1

Author(s):

Sujin Kim ◽

Suji Kim ◽

Ae-Rang Hwang ◽

Hyoung Chul Choi ◽

Ji-Yun Lee ◽

...

Keyword(s):

Endothelial Dysfunction ◽

Er Stress ◽

Therapeutic Potential ◽

Ex Vivo ◽

Cardiovascular Complications ◽

Unfolded Protein Responses ◽

Unfolded Protein ◽

Endothelial Apoptosis ◽

Ampk Pathway ◽

Aortic Endothelial

It has been suggested that methylglyoxal (MGO), a glycolytic metabolite, has more detrimental effects on endothelial dysfunction than glucose itself. Recent reports showed that high glucose and MGO induced endoplasmic reticulum (ER) stress and myocyte apoptosis in ischemic heart disease was inhibited by apelin. The goal of the study is to investigate the molecular mechanism by which MGO induces endothelial dysfunction via the regulation of ER stress in endothelial cells, and to examine whether apelin-13, a cytoprotective polypeptide ligand, protects MGO-induced aortic endothelial dysfunction. MGO-induced ER stress and apoptosis were determined by immunoblotting and MTT assay in HUVECs. Aortic endothelial dysfunction was addressed by en face immunostaining and acetylcholine-induced vasodilation analysis with aortic rings from mice treated with MGO in the presence or absence of apelin ex vivo. TUDCA, an inhibitor of ER stress, inhibited MGO-induced apoptosis and reduction of cell viability, suggesting that MGO signaling to endothelial apoptosis is mediated via ER stress, which leads to activation of unfolded protein responses (UPR). In addition, MGO-induced UPR and aortic endothelial dysfunction were significantly diminished by apelin-13. Finally, this study showed that apelin-13 protects MGO-induced UPR and endothelial apoptosis through the AMPK pathway. Apelin-13 reduces MGO-induced UPR and endothelial dysfunction via regulating the AMPK activating pathway, suggesting the therapeutic potential of apelin-13 in diabetic cardiovascular complications.

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