scholarly journals Distinct roles of activating transcription factor 6 (ATF6) and double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (PERK) in transcription during the mammalian unfolded protein response

2002 ◽  
Vol 366 (2) ◽  
pp. 585-594 ◽  
Author(s):  
Tetsuya OKADA ◽  
Hiderou YOSHIDA ◽  
Rieko AKAZAWA ◽  
Manabu NEGISHI ◽  
Kazutoshi MORI
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Protein Kinase ◽  
Er Stress ◽  
Double Stranded Rna ◽  
Unfolded Protein ◽  
Genes Encoding ◽  
Membrane Bound ◽  
Activating Transcription Factor ◽  
Protein Response

In response to accumulation of unfolded proteins in the endoplasmic reticulum (ER), a homoeostatic response, termed the unfolded protein response (UPR), is activated in all eukaryotic cells. The UPR involves only transcriptional regulation in yeast, and approx. 6% of all yeast genes, encoding not only proteins to augment the folding capacity in the ER, but also proteins working at various stages of secretion, are induced by ER stress [Travers, Patil, Wodicka, Lockhart, Weissman and Walter (2000) Cell (Cambridge, Mass.) 101, 249–258]. In the present study, we conducted microarray analysis of HeLa cells, although our analysis covered only a small fraction of the human genome. A great majority of human ER stress-inducible genes (approx. 1% of 1800 genes examined) were classified into two groups. One group consisted of genes encoding ER-resident molecular chaperones and folding enzymes, and these genes were directly regulated by the ER-membrane-bound transcription factor activating transcription factor (ATF) 6. The ER-membrane-bound protein kinase double-stranded RNA-activated protein kinase-like ER kinase (PERK)-mediated signalling pathway appeared to be responsible for induction of the remaining genes, which are not involved in secretion, but may be important after cellular recovery from ER stress. In higher eukaryotes, the PERK-mediated translational-attenuation system is known to operate in concert with the transcriptional-induction system. Thus we propose that mammalian cells have evolved a strategy to cope with ER stress different from that of yeast cells.

scholarly journals Link between endoplasmic reticulum stress and autophagy in neurodegenerative diseases

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Toru Hosoi ◽  
Jun Nomura ◽  
Keigo Tanaka ◽  
Koichiro Ozawa ◽  
Akinori Nishi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Neurodegenerative Diseases ◽  
Er Stress ◽  
Brain Function ◽  
Review Article ◽  
Double Stranded Rna ◽  
Unfolded Protein ◽  
Activating Transcription Factor ◽  
The Unfolded Protein Response ◽  
Protein Response

AbstractIncreasing evidence suggests that endoplasmic reticulum (ER) stress and autophagy play an important role in regulating brain function. ER stress activates three major branches of the unfolded protein response (UPR) pathways, namely inositol-requiring enzyme-1 (IRE1), double stranded RNA-activated protein kinase (PKR)-like ER kinase (PERK) and activating transcription factor 6 (ATF6)-mediated pathways. Recent studies have suggested that these UPR signals may be linked to autophagy. In this review article, we summarize recent evidence and discuss a possible link between ER stress and autophagy with regard to neurodegenerative diseases. Furthermore, possible pharmacological strategies targeting UPR and autophagy are discussed.

IRE1 and efferent signaling from the endoplasmic reticulum

2000 ◽  
Vol 113 (21) ◽  
pp. 3697-3702 ◽  
Author(s):  
F. Urano ◽  
A. Bertolotti ◽  
D. Ron
Keyword(s):  
Gene Expression ◽  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Er Stress ◽  
Signaling Pathway ◽  
Unfolded Protein ◽  
Genes Encoding ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Stress Signaling Pathway

Genetic analysis of the cellular adaptation to malfolded proteins in the endoplasmic reticulum (the unfolded protein response - UPR) has revealed a novel signaling pathway initiated by activation of IRE1, an ER-resident protein kinase and endonuclease. In yeast, Ire1p activates gene expression by promoting a non-conventional splicing event that converts the mRNA encoding the Hac1p transcription factor from an inefficiently translated inactive mRNA to an actively translated one. Hac1p binds to the promoters of genes encoding chaperones and other targets of the UPR and activates them. Recently, mammalian IRE1 homologues have been identified and their response to ER stress is regulated by binding to the ER chaperone BiP. The mechanisms by which mammalian IRE1 activates gene expression have not been completely characterized and mammalian HAC1 homologues have not been identified. Surprisingly, mammalian IRE1s are able to activate both JUN N-terminal kinases and an alternative ER-stress signaling pathway mediated by the transcription factor ATF6. This indicates that the mammalian UPR is more complex than that found in yeast.

scholarly journals Ceapins are a new class of unfolded protein response inhibitors, selectively targeting the ATF6α branch

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Ciara M Gallagher ◽  
Carolina Garri ◽  
Erica L Cain ◽  
Kenny Kean-Hooi Ang ◽  
Christopher G Wilson ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Proteolytic Processing ◽  
Unfolded Protein ◽  
New Class ◽  
Cancer Models ◽  
Membrane Bound ◽  
The Unfolded Protein Response ◽  
Protein Response

The membrane-bound transcription factor ATF6α plays a cytoprotective role in the unfolded protein response (UPR), required for cells to survive ER stress. Activation of ATF6α promotes cell survival in cancer models. We used cell-based screens to discover and develop Ceapins, a class of pyrazole amides, that block ATF6α signaling in response to ER stress. Ceapins sensitize cells to ER stress without impacting viability of unstressed cells. Ceapins are highly specific inhibitors of ATF6α signaling, not affecting signaling through the other branches of the UPR, or proteolytic processing of its close homolog ATF6β or SREBP (a cholesterol-regulated transcription factor), both activated by the same proteases. Ceapins are first-in-class inhibitors that can be used to explore both the mechanism of activation of ATF6α and its role in pathological settings. The discovery of Ceapins now enables pharmacological modulation all three UPR branches either singly or in combination.

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

2011 ◽  
Vol 286 (22) ◽  
pp. 20020-20030 ◽  
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 ◽  
Protein Response

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.

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

2019 ◽  
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.

Endoplasmic Reticulum Stress Signaling Pathways: Activation and Diseases

2019 ◽  
Vol 20 (9) ◽  
pp. 935-943 ◽  
Author(s):  
Zhi Zheng ◽  
Yuxi Shang ◽  
Jiahui Tao ◽  
Jun Zhang ◽  
Bingdong Sha
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Misfolded Proteins ◽  
Endogenous Factors ◽  
Unfolded Protein ◽  
Dependent Protein ◽  
Activating Transcription Factor ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Sensor Molecules

Secretory and membrane proteins are folded in the endoplasmic reticulum (ER) prior to their exit. When ER function is disturbed by exogenous and endogenous factors, such as heat shock, ultraviolet radiation, hypoxia, or hypoglycemia, the misfolded proteins may accumulate, promoting ER stress. To rescue this unfavorable situation, the unfolded protein response is activated to reduce misfolded proteins within the ER. Upon ER stress, the ER transmembrane sensor molecules inositol-requiring enzyme 1 (IRE1), RNA-dependent protein kinase (PKR)-like ER kinase (PERK), and activating transcription factor 6, are activated. Here, we discuss the mechanisms of PERK and IRE1 activation and describe two working models for ER stress initiation: the BiP-dependent model and the ligand-driven model. ER stress activation has been linked to multiple diseases, including cancers, Alzheimer’s disease, and diabetes. Thus, the regulation of ER stress may provide potential therapeutic targets for these diseases.

scholarly journals Unfolded Protein Response Pathways Correlatively Modulate Endoplasmic Reticulum Stress Responses in Rat Retinal Müller Cells

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Shengyu Wu ◽  
Xiaolu Zhu ◽  
Biechuan Guo ◽  
Tian Zheng ◽  
Jiangbo Ren ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Endoplasmic Reticulum Stress ◽  
High Glucose ◽  
Müller Cells ◽  
Muller Cells ◽  
Unfolded Protein ◽  
Activating Transcription Factor ◽  
Protein Response

Background. Endoplasmic reticulum stress (ERS) in the retinal Müller cells is a key factor contributing to the retinal inflammation and vascular leakage in diabetic retinopathy (DR). This study was to investigate the underlying mechanisms through which the 3 main unfolded protein response (UPR) pathways regulate ERS and to examine the expression levels of vascular endothelial growth factor (VEGF) in Müller cells in vitro. Methods. Rat Müller cell lines were stimulated with high glucose to mimic a diabetic environment in vitro. PKR-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6) were downregulated or upregulated with shRNA or overexpression plasmids. The transfected Müller cells were cultivated in high glucose medium for 48 hours. Expression of glucose-regulated protein 78 (GRP78), activating transcription factor 4 (ATF4), X-box binding protein 1 (XBP1), ATF6, and VEGF was examined with immunofluorescence and western blot. Results. Our data indicated that ERS was found in both high glucose and osmotic control groups. Overexpression or downregulation of UPR pathways effectively increased or reduced the production of GRP78, ATF4, XBP1, ATF6, and VEGF, respectively. These 3 signaling pathways had similar regulatory effects on VEGF. Conclusion. The 3 UPR-mediated inflammatory pathways were dependent on each other. Inhibition any of these signaling pathways in UPR might be a potential therapeutic target for DR.

scholarly journals Endoplasmic Reticulum Stress-induced mRNA Splicing Permits Synthesis of Transcription Factor Hac1p/Ern4p That Activates the Unfolded Protein Response

1997 ◽  
Vol 8 (10) ◽  
pp. 1845-1862 ◽  
Author(s):  
Tetsushi Kawahara ◽  
Hideki Yanagi ◽  
Takashi Yura ◽  
Kazutoshi Mori
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Intracellular Signaling ◽  
Mrna Splicing ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Precursor Mrna

An intracellular signaling from the endoplasmic reticulum (ER) to the nucleus, called the unfolded protein response (UPR), is activated when unfolded proteins are accumulated in the ER under a variety of stress conditions (“ER stress”). We and others recently identified Hac1p/Ern4p as a transcription factor responsible for the UPR inSaccharomyces cerevisiae. It was further reported that Hac1p (238 aa) is detected only in ER-stressed cells, and its expression is mediated by unconventional splicing ofHAC1 precursor mRNA. The splicing replaces the C-terminal portion of Hac1p; it was proposed that precursor mRNA is also translated but the putative product of 230 aa is rapidly degraded by the ubiquitin–proteasome pathway. We have identified and characterized the same regulated splicing and confirmed its essential features. Contrary to the above proposal, however, we find that the 238-aa product of mature mRNA and the 230-aa-type protein tested are highly unstable with little or no difference in stability. Furthermore, we demonstrate that the absence of Hac1p in unstressed cells is due to the lack of translation of precursor mRNA. We conclude that Hac1p is synthesized as the result of ER stress-induced mRNA splicing, leading to activation of the UPR.

Endoplasmic reticulum stress signaling: the microRNA connection

2013 ◽  
Vol 304 (12) ◽  
pp. C1117-C1126 ◽  
Author(s):  
Marion Maurel ◽  
Eric Chevet
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Small Noncoding Rnas ◽  
Unfolded Protein ◽  
Transcriptional Reprogramming ◽  
Stress Sensors ◽  
Activating Transcription Factor ◽  
Stress Dependent ◽  
Protein Response ◽  
Er Homeostasis

The endoplasmic reticulum (ER)-induced unfolded protein response (ERUPR) is an adaptive mechanism that is activated upon accumulation of misfolded proteins in the ER and aims at restoring ER homeostasis. The ERUPR is transduced by three major ER-resident stress sensors, namely PKR-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol requiring enzyme 1 (IRE1). Activation of these ER stress sensors leads to transcriptional reprogramming of the cells. Recently, microRNAs (miRNAs), small noncoding RNAs that generally repress gene expression, have emerged as key regulators of ER homeostasis and important players in ERUPR-dependent signaling. Moreover, the miRNAs biogenesis machinery appears to also be regulated upon ER stress. Herein we extensively review the relationships existing between “canonical” ERUPR signaling, control of ER homeostasis, and miRNAs. We reveal an intricate signaling network that might confer specificity and selectivity to the ERUPR in tissue- or stress-dependent fashion. We discuss these issues in the context of the physiological and pathophysiological roles of ERUPR signaling.

scholarly journals Aging and Hypercholesterolemia Differentially Affect the Unfolded Protein Response in the Vasculature of ApoE −/− Mice

2021 ◽  
Author(s):  
Yuxiang Zhou ◽  
Xueping Wan ◽  
Kerstin Seidel ◽  
Mo Zhang ◽  
Jena B. Goodman ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Endoplasmic Reticulum Stress ◽  
Protein Disulfide Isomerase ◽  
Disulfide Isomerase ◽  
Unfolded Protein ◽  
Activating Transcription Factor ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Protein Disulfide

Background Persistent activation of endoplasmic reticulum stress and the unfolded protein response (UPR) induces vascular cell apoptosis, contributing to atherogenesis. Aging and hypercholesterolemia are 2 independent proatherogenic factors. How they affect vascular UPR signaling remains unclear. Methods and Results Transcriptome analysis of aortic tissues from high fat diet–fed and aged ApoE −/− mice revealed 50 overlapping genes enriched for endoplasmic reticulum stress‐ and UPR‐related pathways. Aortae from control, Western diet (WD)–fed, and aged ApoE −/− mice were assayed for (1) 3 branches of UPR signaling (pancreatic ER eIF2‐alpha kinase /alpha subunit of the eukaryotic translation initiation factor 1/activating transcription factor 4, inositol‐requiring enzyme 1 alpha/XBP1s, activating transcription factor 6); (2) UPR‐mediated protective adaptation (upregulation of immunoglobulin heavy chain‐binding protein and protein disulfide isomerase); and (3) UPR‐mediated apoptosis (induction of C/EBP homologous transcription factor, p‐JNK, and cleaved caspase‐3). Aortic UPR signaling was differentially regulated in the aged and WD‐fed groups. Consumption of WD activated all 3 UPR branches; in the aged aorta, only the ATF6α arm was activated, but it was 10 times higher than that in the WD group. BiP and protein disulfide isomerase protein levels were significantly decreased only in the aged aorta despite a 5‐fold increase in their mRNA levels. Importantly, the aortae of aged mice exhibited a substantially enhanced proapoptotic UPR compared with that of WD‐fed mice. In lung tissues, UPR activation and the resultant adaptive/apoptotic responses were not significantly different between the 2 groups. Conclusions Using a mouse model of atherosclerosis, this study provides the first in vivo evidence that aging and an atherogenic diet activate differential aortic UPR pathways, leading to distinct vascular responses. Compared with dietary intervention, aging is associated with impaired endoplasmic reticulum protein folding and increased aortic apoptosis.

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