Journal articles: 'Facteur de transcription CHOP'

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Chiribau, Calin-Bogdan, Francesca Gaccioli, Charlie C. Huang, Celvie L. Yuan, and Maria Hatzoglou. "Molecular Symbiosis of CHOP and C/EBPβ Isoform LIP Contributes to Endoplasmic Reticulum Stress-Induced Apoptosis." Molecular and Cellular Biology 30, no. 14 (May 17, 2010): 3722–31. http://dx.doi.org/10.1128/mcb.01507-09.

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ABSTRACT Induction of the transcription factor CHOP (CCAAT-binding homologous protein; GADD 153) is a critical cellular response for the transcriptional control of endoplasmic reticulum (ER) stress-induced apoptosis. Upon nuclear translocation, CHOP upregulates the transcription of proapoptotic factors and downregulates antiapoptotic genes. Transcriptional activation by CHOP involves heterodimerization with other members of the basic leucine zipper transcription factor (bZIP) family. We show that the bZIP protein C/EBPβ isoform LIP is required for nuclear translocation of CHOP during ER stress. In early ER stress, LIP undergoes proteasomal degradation in the cytoplasmic compartment. During later ER stress, LIP binds CHOP in both cytoplasmic and nuclear compartments and contributes to its nuclear import. By using CHOP-deficient cells and transfections of LIP-expressing vectors in C/EBPβ−/− mouse embryonic fibroblasts (MEFs), we show that the LIP-CHOP interaction has a stabilizing role for LIP. At the same time, CHOP uses LIP as a vehicle for nuclear import. LIP-expressing C/EBPβ−/− MEFs showed enhanced ER stress-induced apoptosis compared to C/EBPβ-null cells, a finding in agreement with the decreased levels of Bcl-2, a known transcriptional control target of CHOP. In view of the positive effect of CHOP-LIP interaction in mediating their proapoptotic functions, we propose this functional cooperativity as molecular symbiosis between proteins.

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Teske, Brian F., Michael E. Fusakio, Donghui Zhou, Jixiu Shan, Jeanette N. McClintick, Michael S. Kilberg, and Ronald C. Wek. "CHOP induces activating transcription factor 5 (ATF5) to trigger apoptosis in response to perturbations in protein homeostasis." Molecular Biology of the Cell 24, no. 15 (August 2013): 2477–90. http://dx.doi.org/10.1091/mbc.e13-01-0067.

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Environmental stresses that disrupt protein homeostasis induce phosphorylation of eIF2, triggering repression of global protein synthesis coincident with preferential translation of ATF4, a transcriptional activator of the integrated stress response (ISR). Depending on the extent of protein disruption, ATF4 may not be able to restore proteostatic control and instead switches to a terminal outcome that features elevated expression of the transcription factor CHOP (GADD153/DDIT3). The focus of this study is to define the mechanisms by which CHOP directs gene regulatory networks that determine cell fate. We find that in response to proteasome inhibition, CHOP enhances the expression of a collection of genes encoding transcription regulators, including ATF5, which is preferentially translated during eIF2 phosphorylation. Transcriptional expression of ATF5 is directly induced by both CHOP and ATF4. Knockdown of ATF5 increases cell survival in response to proteasome inhibition, supporting the idea that both ATF5 and CHOP have proapoptotic functions. Transcriptome analysis of ATF5-dependent genes reveals targets involved in apoptosis, including NOXA, which is important for inducing cell death during proteasome inhibition. This study suggests that the ISR features a feedforward loop of stress-induced transcriptional regulators, each subject to transcriptional and translational control, which can switch cell fate toward apoptosis.

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Ubeda, Mariano, and Joel F. Habener. "CHOP Transcription Factor Phosphorylation by Casein Kinase 2 Inhibits Transcriptional Activation." Journal of Biological Chemistry 278, no. 42 (July 21, 2003): 40514–20. http://dx.doi.org/10.1074/jbc.m306404200.

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Cazanave, Sophie C., Nafisa A. Elmi, Yuko Akazawa, Steven F. Bronk, Justin L. Mott, and Gregory J. Gores. "CHOP and AP-1 cooperatively mediate PUMA expression during lipoapoptosis." American Journal of Physiology-Gastrointestinal and Liver Physiology 299, no. 1 (July 2010): G236—G243. http://dx.doi.org/10.1152/ajpgi.00091.2010.

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Endoplasmic reticulum (ER) stress-mediated apoptosis is a key feature of hepatocyte cytotoxicity by saturated free fatty acids (FFA). This lipoapoptosis is dependent, in part, on the transcriptional upregulation of the BH3-only protein PUMA (p53 upregulated modulator of apoptosis). Although the activator protein (AP)-1 complex facilitates PUMA expression by saturated FFA, the transcription factor CAAT/enhancer binding homologous protein (CHOP) is also induced by ER stress and promotes apoptosis. To integrate the role of these two transcription factors in ER stress-induced apoptosis, we examined the relative contribution of CHOP and AP-1 in mediating PUMA induction by saturated FFA. Our results demonstrate that short-hairpin RNA-targeted knockdown of CHOP attenuates palmitate-induced apoptosis in Huh-7 cells. Loss of CHOP induction also reduced the increase in PUMA mRNA and protein levels as well as Bax activation by palmitate. No functional CHOP binding sites were identified in the PUMA promoter sequence. Rather, we observed that CHOP physically interacts with the AP-1 complex protein c-Jun upon palmitate treatment, and a CHOP:phosphorylated c-Jun heteromeric complex binds to the AP-1 consensus binding sequence within the PUMA promoter region. Finally, loss of function studies suggest that both transcription factors are necessary for maximal PUMA induction. Collectively, these data suggest that CHOP and AP-1 cooperatively mediate PUMA induction during hepatocyte lipoapoptosis.

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Bruhat, Alain, Céline Jousse, Valérie Carraro, Andreas M. Reimold, Marc Ferrara, and Pierre Fafournoux. "Amino Acids Control Mammalian Gene Transcription: Activating Transcription Factor 2 Is Essential for the Amino Acid Responsiveness of the CHOP Promoter." Molecular and Cellular Biology 20, no. 19 (October 1, 2000): 7192–204. http://dx.doi.org/10.1128/mcb.20.19.7192-7204.2000.

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ABSTRACT In mammals, plasma concentration of amino acids is affected by nutritional or pathological conditions. It has been well established that nutrients, and particularly amino acids, are involved in the control of gene expression. Here we examined the molecular mechanisms involved in the regulation ofCHOP (a CCAAT/enhancer-binding protein [C/EBP]-related gene) expression upon amino acid limitation. We have previously shown that regulation of CHOP mRNA expression by amino acid concentration has both transcriptional and posttranscriptional components. We report the analysis ofcis- and trans-acting elements involved in the transcriptional activation of the human CHOPgene by leucine starvation. Using a transient expression assay, we show that a cis-positive element is essential for amino acid regulation of the CHOP promoter. This sequence is the first described that can regulate a basal promoter in response to starvation for several individual amino acids and therefore can be called an amino acid response element (AARE). In addition, we show that the CHOP AARE is related to C/EBP and ATF/CRE binding sites and binds in vitro the activating transcription factor 2 (ATF-2) in starved and unstarved conditions. Using ATF-2-deficient mouse embryonic fibroblasts and an ATF-2-dominant negative mutant, we demonstrate that expression of this transcription factor is essential for the transcriptional activation of CHOP by leucine starvation. Altogether, these results suggest that ATF-2 may be a member of a cascade of molecular events by which the cellular concentration of amino acids can regulate mammalian gene expression.

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Ubeda, Mariano, Mario Vallejo, and Joel F. Habener. "CHOP Enhancement of Gene Transcription by Interactions with Jun/Fos AP-1 Complex Proteins." Molecular and Cellular Biology 19, no. 11 (November 1, 1999): 7589–99. http://dx.doi.org/10.1128/mcb.19.11.7589.

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ABSTRACT The transcription factor CHOP (C/EBP homologous protein 10) is a bZIP protein induced by a variety of stimuli that evoke cellular stress responses and has been shown to arrest cell growth and to promote programmed cell death. CHOP cannot form homodimers but forms stable heterodimers with the C/EBP family of activating transcription factors. Although initially characterized as a dominant negative inhibitor of C/EBPs in the activation of gene transcription, CHOP-C/EBP can activate certain target genes. Here we show that CHOP interacts with members of the immediate-early response, growth-promoting AP-1 transcription factor family, JunD, c-Jun, and c-Fos, to activate promoter elements in the somatostatin, JunD, and collagenase genes. The leucine zipper dimerization domain is required for interactions with AP-1 proteins and transactivation of transcription. Analyses by electrophoretic mobility shift assays and by an in vivo mammalian two-hybrid system for protein-protein interactions indicate that CHOP interacts with AP-1 proteins inside cells and suggest that it is recruited to the AP-1 complex by a tethering mechanism rather than by direct binding of DNA. Thus, CHOP not only is a negative or a positive regulator of C/EBP target genes but also, when tethered to AP-1 factors, can activate AP-1 target genes. These findings establish the existence of a new mechanism by which CHOP regulates gene expression when cells are exposed to cellular stress.

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Yoshida, Hiderou, Tetsuya Okada, Kyosuke Haze, Hideki Yanagi, Takashi Yura, Manabu Negishi, and Kazutoshi Mori. "ATF6 Activated by Proteolysis Binds in the Presence of NF-Y (CBF) Directly to the cis-Acting Element Responsible for the Mammalian Unfolded Protein Response." Molecular and Cellular Biology 20, no. 18 (September 15, 2000): 6755–67. http://dx.doi.org/10.1128/mcb.20.18.6755-6767.2000.

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ABSTRACT Transcription of genes encoding molecular chaperones and folding enzymes in the endoplasmic reticulum (ER) is induced by accumulation of unfolded proteins in the ER. This intracellular signaling, known as the unfolded protein response (UPR), is mediated by thecis-acting ER stress response element (ERSE) in mammals. In addition to ER chaperones, the mammalian transcription factor CHOP (also called GADD153) is induced by ER stress. We report here that the transcription factor XBP-1 (also called TREB5) is also induced by ER stress and that induction of CHOP and XBP-1 is mediated by ERSE. The ERSE consensus sequence is CCAAT-N9-CCACG. As the general transcription factor NF-Y (also known as CBF) binds to CCAAT, CCACG is considered to provide specificity in the mammalian UPR. We recently found that the basic leucine zipper protein ATF6 isolated as a CCACG-binding protein is synthesized as a transmembrane protein in the ER, and ER stress-induced proteolysis produces a soluble form of ATF6 that translocates into the nucleus. We report here that overexpression of soluble ATF6 activates transcription of the CHOP and XBP-1 genes as well as of ER chaperone genes constitutively, whereas overexpression of a dominant negative mutant of ATF6 blocks the induction by ER stress. Furthermore, we demonstrated that soluble ATF6 binds directly to CCACG only when CCAAT exactly 9 bp upstream of CCACG is bound to NF-Y. Based on these and other findings, we concluded that specific and direct interactions between ATF6 and ERSE are critical for transcriptional induction not only of ER chaperones but also of CHOP and XBP-1.

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Ubeda, M., X. Z. Wang, H. Zinszner, I. Wu, J. F. Habener, and D. Ron. "Stress-induced binding of the transcriptional factor CHOP to a novel DNA control element." Molecular and Cellular Biology 16, no. 4 (April 1996): 1479–89. http://dx.doi.org/10.1128/mcb.16.4.1479.

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CHOP (GADD153) is a mammalian nuclear protein that dimerizes with members of the C/EBP family of transcriptional factors. Absent under normal conditions, CHOP is induced by the stress encountered during nutrient deprivation, the acute-phase response, and treatment of cells with certain toxins. The basic region of CHOP deviates considerably in sequence from that of other C/EBP proteins, and CHOP-C/EBP heterodimers are incapable of binding to a common class of C/EBP sites. With respect to such sites, CHOP serves as an inhibitor of the activity of C/EBP proteins. However, recent studies indicate that certain functions of CHOP, such as the induction of growth arrest by overexpression of the wild-type protein and oncogenic transformation by the TLS-CHOP fusion protein, require an intact basic region, suggesting that DNA binding by CHOP may be implicated in these activities. In this study an in vitro PCR-based selection assay was used to identify sequences bound by CHOP-C/EBP dimers. These sequences were found to contain a unique core element PuPuPuTGCAAT(A/C)CCC. Competition in DNA-binding assays, DNase 1 footprint analysis, and methylation interference demonstrate that the binding is sequence specific. Deletions in the basic region of CHOP lead to a loss of DNA binding, suggesting that CHOP participates in this process. Stress induction in NIH 3T3 cells leads to the appearance of CHOP-containing DNA-binding activity. CHOP is found to contain a transcriptional activation domain which is inducible by cellular stress, lending further support to the notion that the protein can function as a positively acting transcription factor. We conclude that CHOP may serve a dual role both as an inhibitor of the ability of C/EBP proteins to activate some target genes and as a direct activator of others.

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Wan, Xiao-shan, Xiang-hong Lu, Ye-cheng Xiao, Yuan Lin, Hong Zhu, Ting Ding, Ying Yang, et al. "ATF4- and CHOP-Dependent Induction of FGF21 through Endoplasmic Reticulum Stress." BioMed Research International 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/807874.

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Fibroblast growth factor 21 (FGF21) is an important endogenous regulator involved in the regulation of glucose and lipid metabolism. FGF21 expression is strongly induced in animal and human subjects with metabolic diseases, but little is known about the molecular mechanism. Endoplasmic reticulum (ER) stress plays an essential role in metabolic homeostasis and is observed in numerous pathological processes, including type 2 diabetes, overweight, nonalcoholic fatty liver disease (NAFLD). In this study, we investigate the correlation between the expression of FGF21 and ER stress. We demonstrated that TG-induced ER stress directly regulated the expression and secretion of FGF21 in a dose- and time-dependent manner. FGF21 is the target gene for activating transcription factor 4 (ATF4) and CCAAT enhancer binding protein homologous protein (CHOP). Suppression of CHOP impaired the transcriptional activation of FGF21 by TG-induced ER stress in CHOP−/− mouse primary hepatocytes (MPH), and overexpression of ATF4 and CHOP resulted in FGF21 promoter activation to initiate the transcriptional programme. In mRNA stability assay, we indicated that ER stress increased the half-life of mRNA of FGF21 significantly. In conclusion, FGF21 expression is regulated by ER stress via ATF- and CHOP-dependent transcriptional mechanism and posttranscriptional mechanism, respectively.

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Netherton, Christopher L., James C. Parsley, and Thomas Wileman. "African Swine Fever Virus Inhibits Induction of the Stress-Induced Proapoptotic Transcription Factor CHOP/GADD153." Journal of Virology 78, no. 19 (October 1, 2004): 10825–28. http://dx.doi.org/10.1128/jvi.78.19.10825-10828.2004.

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ABSTRACT Stress signaling from mitochondria and the endoplasmic reticulum (ER) leads to the induction of the proapoptotic transcription factor CHOP/GADD153. Many viruses use the ER as a site of replication and/or envelopment, and this activity can lead to the activation of ER stress and apoptosis. African swine fever virus (ASFV) is assembled on the cytoplasmic face of the ER and ultimately enveloped by ER membrane cisternae. The virus also recruits mitochondria to sites of viral replication and induces the mitochondrial stress protein hsp60. Here we studied the effects of ASFV on the induction of CHOP/GADD153 in infected cells. Interestingly, unlike other ER-tropic viruses, ASFV did not activate CHOP and was able to inhibit the induction of CHOP/GADD153 by a number of exogenous stimuli.

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Duan, Mengyun, Yuan Yang, Shuang Peng, Xiaoqin Liu, Jixin Zhong, Yurong Guo, Min Lu, et al. "C/EBP Homologous Protein (CHOP) Activates Macrophages and Promotes Liver Fibrosis in Schistosoma japonicum-Infected Mice." Journal of Immunology Research 2019 (December 1, 2019): 1–13. http://dx.doi.org/10.1155/2019/5148575.

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CCAAT/enhancer-binding homologous protein (CHOP), a transcriptional regulator induced by endoplasmic reticulum stress (ER stress) is a pivotal factor in the ER stress-mediated apoptosis pathway. Previous studies have shown that CHOP is involved in the formation of fibrosis in a variety of tissues and is associated with alternative macrophage activation. The role of CHOP in the pathologic effects of liver fibrosis in schistosomiasis has not been reported, and underlying mechanisms remain unclear. This study is aimed at understanding the effect of CHOP on liver fibrosis induced by Schistosoma japonicum (S. japonicum) in vivo and clarifying its mechanism. C57BL/6 mice were infected with cercariae of S. japonicum through the abdominal skin. The liver fibrosis was examined. The level of IL-13 was observed. The expressions of CHOP, Krüppel-like factor 4 (KLF4), signal transducer and activator of transcription 6 (STAT6), phosphorylation STAT6, interleukin-13 receptor alpha 1 (IL-13Rα1), and interleukin-4 receptor alpha (IL-4Rα) were analysed. The eosinophilic granuloma and collagen deposition were found around the eggs in mice infected for 6 and 10 weeks. IL-13 in plasma and IL-13Rα1 and IL-4Rα in liver tissue were significantly increased. The phosphorylated STAT6 was enhanced while Krüppel-like factor 4 (KLF4) was decreased in liver tissue. The expression of CHOP and colocalization of CHOP and CD206 were increased. Overall, these results suggest that CHOP plays a critical role in hepatic fibrosis induced by S. japonicum, likely through promoting alternative activation of macrophages.

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Shiozaki, Yuji, Kayo Okamura, Shohei Kohno, Audrey L. Keenan, Kristina Williams, Xiaoyun Zhao, Wallace S. Chick, Shinobu Miyazaki-Anzai, and Makoto Miyazaki. "The CDK9–cyclin T1 complex mediates saturated fatty acid–induced vascular calcification by inducing expression of the transcription factor CHOP." Journal of Biological Chemistry 293, no. 44 (September 12, 2018): 17008–20. http://dx.doi.org/10.1074/jbc.ra118.004706.

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Vascular calcification (or mineralization) is a common complication of chronic kidney disease (CKD) and is closely associated with increased mortality and morbidity rates. We recently reported that activation of the activating transcription factor 4 (ATF4) pathway through the saturated fatty acid (SFA)-induced endoplasmic reticulum (ER) stress response plays a causative role in CKD-associated vascular calcification. Here, using mouse models of CKD, we 1) studied the contribution of the proapoptotic transcription factor CCAAT enhancer–binding protein homologous protein (CHOP) to CKD-dependent medial calcification, and 2) we identified an additional regulator of ER stress–mediated CHOP expression. Transgenic mice having smooth muscle cell (SMC)–specific CHOP expression developed severe vascular apoptosis and medial calcification under CKD. Screening of a protein kinase inhibitor library identified 16 compounds, including seven cyclin-dependent kinase (CDK) inhibitors, that significantly suppressed CHOP induction during ER stress. Moreover, selective CDK9 inhibitors and CRISPR/Cas9-mediated CDK9 reduction blocked SFA-mediated induction of CHOP expression, whereas inhibitors of other CDK isoforms did not. Cyclin T1 knockout inhibited SFA-mediated induction of CHOP and mineralization, whereas deletion of cyclin T2 and cyclin K promoted CHOP expression levels and mineralization. Of note, the CDK9–cyclin T1 complex directly phosphorylated and activated ATF4. These results demonstrate that the CDK9–cyclin T1 and CDK9–cyclin T2/K complexes have opposing roles in CHOP expression and CKD-induced vascular calcification. They further reveal that the CDK9–cyclin T1 complex mediates vascular calcification through CHOP induction and phosphorylation-mediated ATF4 activation.

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Coutts, Margaret, Kunyuan Cui, Kerry L. Davis, Joan Cleves Keutzer, and Arthur J. Sytkowski. "Regulated Expression and Functional Role of the Transcription Factor CHOP (GADD153) in Erythroid Growth and Differentiation." Blood 93, no. 10 (May 15, 1999): 3369–78. http://dx.doi.org/10.1182/blood.v93.10.3369.410k11_3369_3378.

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The hematopoietic growth factor erythropoietin (Epo) triggers changes in the expression of genes that encode important regulators of erythroid cell growth and differentiation. We now report that Epo markedly upregulates chop (gadd153) expression and that this transcription factor plays a role in erythropoiesis. Using a differential hybridization assay, we isolated a full-length cDNA ofchop as an Epo upregulated gene in Rauscher murine erythroleukemia cells. RNase protection assays demonstrated that Epo or dimethyl sulfoxide induction increased steady-state mRNA levels 10- to 20-fold after 24 to 48 hours. Western blot analysis confirmed a marked increase in CHOP protein. Among the other c/ebp family members, only c/ebp β was also upregulated during erythroid differentiation. Among normal hematopoietic cells examined, steady-state mRNA levels were highest in erythroid cells, with levels peaking during terminal differentiation. Transient overexpression ofchop in Rauscher cells resulted in a significant increase in Epo- or dimethyl sulfoxide (DMSO)-induced hemoglobinization, further linking chop upregulation to erythroid differentiation. Artificial downregulation of chop in normal murine bone marrow cells with antisense oligodeoxynucleotides inhibited colony-forming unit-erythroid (CFU-E)–derived colony growth in a concentration-dependent manner. Burst-forming unit-erythroid (BFU-E)–derived colony growth was not affected. Using a Far Western type of analysis, we detected several potential CHOP binding partners among the nuclear proteins of Rauscher cells. Importantly, the number and relative abundance of these proteins changed with differentiation. The results strongly suggest that CHOP plays a role in erythropoiesis, possibly through interactions with both C/EBP and non-C/EBP family members.

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Huang, Hai-Yan, Xi Li, Mei Liu, Tan-Jing Song, Qun He, Chun-Gu Ma, and Qi-Qun Tang. "Transcription factor YY1 promotes adipogenesis via inhibiting CHOP-10 expression." Biochemical and Biophysical Research Communications 375, no. 4 (October 2008): 496–500. http://dx.doi.org/10.1016/j.bbrc.2008.07.151.

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Attanasio, Sergio, Rosa Ferriero, Gwladys Gernoux, Rossella De Cegli, Annamaria Carissimo, Edoardo Nusco, Severo Campione, et al. "CHOP and c-JUN up-regulate the mutant Z α1-antitrypsin, exacerbating its aggregation and liver proteotoxicity." Journal of Biological Chemistry 295, no. 38 (July 28, 2020): 13213–23. http://dx.doi.org/10.1074/jbc.ra120.014307.

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α1-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop−/− mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop−/− mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter–based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.

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van der Sanden, Michiel H. M., Henriët Meems, Martin Houweling, J. Bernd Helms, and Arie B. Vaandrager. "Induction of CCAAT/Enhancer-binding Protein (C/EBP)-homologous Protein/Growth Arrest and DNA Damage-inducible Protein 153 Expression during Inhibition of Phosphatidylcholine Synthesis Is Mediated via Activation of a C/EBP-activating Transcription Factor-responsive Element." Journal of Biological Chemistry 279, no. 50 (October 4, 2004): 52007–15. http://dx.doi.org/10.1074/jbc.m405577200.

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The gene for the proapoptotic transcription factor CCAAT/enhancer-binding protein (C/EBP)-homologous protein/growth arrest and DNA damage-inducible protein 153 (CHOP/GADD153) is induced by various cellular stresses. Previously, we described that inhibition of phosphatidylcholine (PC) synthesis in MT58 cells, which contain a temperature-sensitive mutation in CTP:phosphocholine cytidylyltransferase (CT), results in apoptosis preceded by the induction of CHOP. Here we report that prevention of CHOP induction, by expression of antisense CHOP, delays the PC depletion-induced apoptotic process. By mutational analysis of the conserved region in the promoter of the CHOP gene, we provide evidence that the C/EBP-ATF composite site, but not the ER stress-responsive element or the activator protein-1 site, is required for the increased expression of CHOP during PC depletion. Inhibition of PC synthesis in MT58 cells also led to an increase in phosphorylation of the stress-related transcription factor ATF2 and the stress kinase JNK after 8 and 16 h, respectively. In contrast, no phosphorylation of p38 MAPK was observed in MT58 cultured at the nonpermissive temperature. Treatment of MT58 cells with the JNK inhibitor SP600125 could rescue the cells from apoptosis but did not inhibit the phosphorylation of ATF2 or the induction of CHOP. Taken together, our results suggest that increased expression of CHOP during PC depletion depends on a C/EBP-ATF element in its promoter and might be mediated by binding of ATF2 to this element.

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Gao, Yan-Yan, Bao-Qin Liu, Zhen-Xian Du, Hai-Yan Zhang, Xiao-Fang Niu, and Hua-Qin Wang. "Implication of Oxygen-Regulated Protein 150 (ORP150) in Apoptosis Induced by Proteasome Inhibitors in Human Thyroid Cancer Cells." Endocrine Reviews 31, no. 5 (October 1, 2010): 779–80. http://dx.doi.org/10.1210/edrv.31.5.9996.

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ABSTRACT Context The inhibition of the 26S proteasome may lead to endoplasmic reticulum stress, which has been shown to be implicated in the antitumoral effects of proteasome inhibitors. Oxygen-regulated protein 150 (ORP150) is an inducible endoplasmic reticulum chaperone that is up-regulated after numerous cellular insults and has a cytoprotective role for the maintenance of cellular viability. Objective The purpose of this study was to determine the involvement of ORP150 in cytotoxicity of thyroid cancer cells mediated by proteasome inhibition. Design The effects of proteasome inhibition on the expression of ORP150 were analyzed using real-time RT-PCR and Western blot. To ascertain the effect of ORP150, cells were transfected with ORP150 plasmid or small interfering RNA (siRNA) against ORP150, apoptotic cells, and induction of CCAAT/enhancer-binding protein homologous transcription factor (CHOP) mediated by proteasome inhibition were investigated. Results ORP150 was induced in thyroid cancer cells after proteasome inhibition. Suppression of activating transcription factor 4 expression by siRNA inhibited the up-regulation of ORP150 mediated by proteasome inhibitors. siRNA for ORP150 stimulated MG132-mediated apoptosis and induction of CHOP, a transcription factor with apoptosis-inducing activity. In contrast, ORP150-overexpressing cells demonstrated less susceptibility to MG132-induced apoptosis and displayed less up-regulation of CHOP. In addition, the sensitizing effect of small interfering ORP150 on apoptosis was suppressed by siRNA for CHOP. Conclusions These results suggest that up-regulation of ORP150 in thyroid cancer cells inhibits MG132-induced apoptosis via suppression of CHOP induction, thereby decreasing the potential antitumor activity of MG132.

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Zhang, Zheng, Xiao-Yan Yang, and David M. Cohen. "Urea-associated oxidative stress and Gadd153/CHOP induction." American Journal of Physiology-Renal Physiology 276, no. 5 (May 1, 1999): F786—F793. http://dx.doi.org/10.1152/ajprenal.1999.276.5.f786.

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Urea treatment (100–300 mM) increased expression of the oxidative stress-responsive transcription factor, Gadd153/CHOP, at the mRNA and protein levels (at ≥4 h) in renal medullary mIMCD3 cells in culture, whereas other solutes did not. Expression of the related protein, CCAAT/enhancer-binding protein (C/EBP-β), was not affected, nor was expression of the sensor of endoplasmic reticulum stress, grp78. Urea modestly increased Gadd153 transcription by reporter gene analysis but failed to influence Gadd153 mRNA stability. Importantly, upregulation of Gadd153 mRNA and protein expression by urea was antioxidant sensitive. Accordingly, urea treatment was associated with oxidative stress, as quantitated by intracellular reduced glutathione content in mIMCD3 cells. In addition, antioxidant treatment partially inhibited the ability of urea to activate transcription of an Egr-1 luciferase reporter gene. Therefore oxidative stress represents a novel solute-signaling pathway in the kidney medulla and, potentially, in other tissues.

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Yang, Hsiang-Yu, Jhao-Ying Chen, Yen-Nien Huo, Pei-Ling Yu, Pei-Zhen Lin, Shih-Che Hsu, Shih-Ming Huang, Chien-Sung Tsai, and Chih-Yuan Lin. "The Role of Sirtuin 1 in Palmitic Acid-Induced Endoplasmic Reticulum Stress in Cardiac Myoblasts." Life 12, no. 2 (January 26, 2022): 182. http://dx.doi.org/10.3390/life12020182.

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Background: Lipotoxicity causes endoplasmic reticulum (ER) stress, leading to cell apoptosis. Sirtuin 1 (Sirt1) regulates gene transcription and cellular metabolism. In this study, we investigated the role of Sirt1 in palmitate-induced ER stress. Methods: Both H9c2 myoblasts and heart-specific Sirt1 knockout mice fed a palmitate-enriched high-fat diet were used. Results: The high-fat diet induced C/EBP homologous protein (CHOP) and activating transcription factor 4 (ATF4) expression in both Sirt1 knockout mice and controls. The Sirt1 knockout mice showed higher CHOP and ATF4 expression compared to those in the control. Palmitic acid (PA) induced ATF4 and CHOP expression in H9c2 cells. PA-treated H9c2 cells showed decreased cytosolic NAD+/NADH alongside reduced Sirt1′s activity. The H9c2 cells showed increased ATF4 and CHOP expression when transfected with plasmid encoding dominant negative mutant Sirt1. Sirt1 activator SRT1720 did not affect CHOP and ATF4 expression. Although SRT1720 enhanced the nuclear translocation of ATF4, the extent of the binding of ATF4 to the CHOP promoter did not increase in PA treated-H9c2 cells. Conclusion: PA-induced ER stress is mediated through the upregulation of ATF4 and CHOP. Cytosolic NAD+ concentration is diminished by PA-induced ER stress, leading to decreased Sirt1 activity. The Sirt1 activator SRT1720 promotes the nuclear translocation of ATF4 in PA-treated H9c2 cells.

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Medigeshi, Guruprasad R., Alissa M. Lancaster, Alec J. Hirsch, Thomas Briese, W. Ian Lipkin, Victor DeFilippis, Klaus Früh, Peter W. Mason, Janko Nikolich-Zugich, and Jay A. Nelson. "West Nile Virus Infection Activates the Unfolded Protein Response, Leading to CHOP Induction and Apoptosis." Journal of Virology 81, no. 20 (August 8, 2007): 10849–60. http://dx.doi.org/10.1128/jvi.01151-07.

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ABSTRACT West Nile virus (WNV)-mediated neuronal death is a hallmark of WNV meningitis and encephalitis. However, the mechanisms of WNV-induced neuronal damage are not well understood. We investigated WNV neuropathogenesis by using human neuroblastoma cells and primary rat hippocampal neurons. We observed that WNV activates multiple unfolded protein response (UPR) pathways, leading to transcriptional and translational induction of UPR target genes. We evaluated the role of the three major UPR pathways, namely, inositol-requiring enzyme 1-dependent splicing of X box binding protein 1 (XBP1) mRNA, activation of activating transcription factor 6 (ATF6), and protein kinase R-like endoplasmic reticulum (ER) kinase-dependent eukaryotic initiation factor 2α (eIF2α) phosphorylation, in WNV-infected cells. We show that XBP1 is nonessential or can be replaced by other UPR pathways in WNV replication. ATF6 was rapidly degraded by proteasomes, consistent with induction of ER stress by WNV. We further observed a transient phosphorylation of eIF2α and induction of the proapoptotic cyclic AMP response element-binding transcription factor homologous protein (CHOP). WNV-infected cells exhibited a number of apoptotic phenotypes, such as (i) induction of growth arrest and DNA damage-inducible gene 34, (ii) activation of caspase-3, and (iii) cleavage of poly(ADP-ribose) polymerase. The expression of WNV nonstructural proteins alone was sufficient to induce CHOP expression. Importantly, WNV grew to significantly higher viral titers in chop − / − mouse embryonic fibroblasts (MEFs) than in wild-type MEFs, suggesting that CHOP-dependent premature cell death represents a host defense mechanism to limit viral replication that might also be responsible for the widespread neuronal loss observed in WNV-infected neuronal tissue.

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Nishitoh, H. "CHOP is a multifunctional transcription factor in the ER stress response." Journal of Biochemistry 151, no. 3 (December 30, 2011): 217–19. http://dx.doi.org/10.1093/jb/mvr143.

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Mihailidou, Chrysovalantou, Ioulia Chatzistamou, Athanasios G. Papavassiliou, and Hippokratis Kiaris. "Improvement of chemotherapeutic drug efficacy by endoplasmic reticulum stress." Endocrine-Related Cancer 22, no. 2 (February 10, 2015): 229–38. http://dx.doi.org/10.1530/erc-15-0019.

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Tunicamycin (TUN), an inhibitor of protein glycosylation and therefore a potent stimulator of endoplasmic reticulum (ER) stress, has been used to improve anticancer drug efficacy, but the underlying mechanism remains obscure. In this study, we show that acute administration of TUN in mice induces the unfolded protein response and suppresses the levels of P21, a cell cycle regulator with anti-apoptotic activity. The inhibition of P21 after ER stress appears to be C/EBP homologous protein (CHOP)-dependent because in CHOP-deficient mice, TUN not only failed to suppress, but rather induced the expression of P21. Results of promoter-activity reporter assays using human cancer cells and mouse fibroblasts indicated that the regulation of P21 by CHOP operates at the level of transcription and involves direct binding of CHOP transcription factor to the P21 promoter. The results of cell viability and clonogenic assays indicate that ER-stress-related suppression of P21 expression potentiates caspase activation and sensitizes cells to doxorubicin treatment, while administration of TUN to mice increases the therapeutic efficacy of anticancer therapy for HepG2 liver and A549 lung cancers.

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Wei, Yuhong, Svetlana Puzhko, Martin Wabitsch, and Cynthia Gates Goodyer. "Transcriptional Regulation of the Human Growth Hormone Receptor (hGHR) Gene V2 Promoter by Transcriptional Activators and Repressor." Molecular Endocrinology 23, no. 3 (March 1, 2009): 373–87. http://dx.doi.org/10.1210/me.2008-0190.

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Abstract The V2 transcript is the major ubiquitously expressed human GH receptor (hGHR) mRNA in all tissues examined to date. In a previous investigation, we defined the V2 promoter as TATA-less and exhibiting many characteristics of a housekeeping gene promoter. We also demonstrated that its basal activity is determined by several different cis-regulatory regions within both the promoter and the V2 exon. In the present study, we used luciferase-reporter, site-directed mutagenesis, gel shift, chromatin immunoprecipitation, and quantitative RT-PCR assays to investigate the ability of certain transcription factors to regulate hGHR V2 transcription through these regions in mammalian cells, including human adipocytes. Ets1 was found to transactivate the V2 proximal promoter through specific Ets sites. Two CCAAT/enhancer-binding protein (C/EBP) family members [C/EBP-homologous protein (CHOP) and C/EBPβ] enhanced V2 transcription via different pathways: indirectly, by association with a V2 exon region (CHOP), and directly, using a V2 proximal promoter noncanonical binding site (C/EBPβ). The Notch signaling mediator, Hes1, potently suppressed V2 promoter activity through interaction with two Hes sites within the V2 exon. We propose that these transcriptional factors regulate hGHR V2 expression by acting as downstream nuclear effectors, linking specific signaling cascades (e.g. MAPK and Notch) triggered by different growth factor-, development-, and nutrition- as well as stress-related stimuli. Our data also suggest that these factors are likely to be important in the differentiation-induced increase in V2 mRNA expression in adipocytes, with Ets1 and CHOP functioning at the preadipocyte stage to prepare the cells for differentiation and increasing C/EBPs and decreasing Hes1 levels contributing during adipocyte maturation.

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Zhou, Yong, Xiaoxia Liu, Wenjuan Li, Xiaoyan Sun, and Zhenwei Xie. "Endoplasmic reticulum stress contributes to the pathogenesis of stress urinary incontinence in postmenopausal women." Journal of International Medical Research 46, no. 12 (November 14, 2018): 5269–77. http://dx.doi.org/10.1177/0300060518807602.

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Objective To investigate the relationship between endoplasmic reticulum stress (ERS) and the pathogenesis of stress urinary incontinence (SUI) in postmenopausal women. Methods Anterior vaginal wall tissue was collected from postmenopausal women with SUI and control subjects. Western blotting was performed for glucose-regulated protein (GRP78), inositol-requiring enzyme 1(IRE1), protein kinase-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), C/EBP-homologous protein (CHOP), and B-cell lymphoma 2 (Bcl-2). Additionally, mRNA expression levels of PERK, activating transcription factor 4 (ATF4), and CHOP were examined by real-time polymerase chain reaction. Results GRP78 protein and mRNA expression levels were significantly lower in women with SUI, compared with control subjects. PERK and p-PERK expression levels were higher in women with SUI than in control subjects. However, no differences in IRE1 or ATF6 expression levels were observed in either group. Notably, higher CHOP and lower Bcl-2 protein expression levels were detected in women with SUI, compared with control subjects. Furthermore, PERK, ATF4, and CHOP mRNA expression levels were significantly higher in women with SUI than in control subjects. Conclusions Alterations of ERS markers in SUI suggest that ERS may be involved in the development of SUI in postmenopausal women.

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Wei, Wei, Hongmei Yang, Michael Menconi, Peirang Cao, Chester E. Chamberlain, and Per-Olof Hasselgren. "Treatment of cultured myotubes with the proteasome inhibitor β-lactone increases the expression of the transcription factor C/EBPβ." American Journal of Physiology-Cell Physiology 292, no. 1 (January 2007): C216—C226. http://dx.doi.org/10.1152/ajpcell.00282.2006.

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The role of the proteasome in the regulation of cellular levels of the transcription factor CCAAT/enhancer-binding protein β (C/EBPβ) is poorly understood. We tested the hypothesis that C/EBPβ levels in cultured myotubes are regulated, at least in part, by proteasome activity. Treatment of cultured L6 myotubes, a rat skeletal muscle cell line, with the specific proteasome inhibitor β-lactone resulted in increased nuclear levels of C/EBPβ as determined by Western blotting and immunofluorescent detection. This effect of β-lactone reflected inhibited degradation of C/EBPβ. Surprisingly, the increased C/EBPβ levels in β-lactone-treated myotubes did not result in increased DNA-binding activity. In additional experiments, treatment of the myotubes with β-lactone resulted in increased nuclear levels of growth arrest DNA damage/C/EBP homologous protein (Gadd153/CHOP), a dominant-negative member of the C/EBP family that can form heterodimers with other members of the C/EBP family and block DNA binding. Coimmunoprecipitation and immunofluorescent detection provided evidence that C/EBPβ and Gadd153/CHOP interacted and colocalized in the nuclei of the β-lactone-treated myotubes. When Gadd153/CHOP expression was downregulated by transfection of myotubes with siRNA targeting Gadd153/CHOP, C/EBPβ DNA-binding activity was restored in β-lactone-treated myotubes. The results suggest that C/EBPβ is degraded by a proteasome-dependent mechanism in skeletal muscle cells and that Gadd153/CHOP can interact with C/EBPβ and block its DNA-binding activity. The observations are important because they increase the understanding of the complex regulation of the expression and activity of C/EBPβ in skeletal muscle.

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Lozon, Tricia I., Alison J. Eastman, Gustavo Matute-Bello, Peter Chen, Teal S. Hallstrand, and William A. Altemeier. "PKR-dependent CHOP induction limits hyperoxia-induced lung injury." American Journal of Physiology-Lung Cellular and Molecular Physiology 300, no. 3 (March 2011): L422—L429. http://dx.doi.org/10.1152/ajplung.00166.2010.

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Supplemental O2is commonly employed in patients with respiratory failure; however, hyperoxia is also a potential contributor to lung injury. In animal models, hyperoxia causes oxidative stress in the lungs, resulting in increased inflammation, edema, and permeability. We hypothesized that oxidative stress from prolonged hyperoxia leads to endoplasmic reticulum (ER) stress, resulting in activation of the unfolded protein response (UPR) and induction of CCAAT enhancer-binding protein homologous protein (CHOP), a transcription factor associated with cell death in the setting of persistent ER stress. To test this hypothesis, we exposed the mouse lung epithelial cell line MLE-12 to 95% O2for 8–24 h and evaluated for evidence of UPR induction and CHOP induction. Hyperoxia caused increased CHOP expression without other evidence of UPR activation. Because CHOP expression is preceded by phosphorylation of the α-subunit of the eukaryotic initiation factor-2 (eIF2α), we evaluated the role of double-stranded RNA-activated protein kinase (PKR), a non-UPR-associated eIF2α kinase. Hyperoxia caused PKR phosphorylation, and RNA interference knockdown of PKR attenuated hyperoxia-induced CHOP expression. In vivo, hyperoxia induced PKR phosphorylation and CHOP expression in the lungs without other biochemical evidence for ER stress. Additionally, Ddit3−/−(CHOP-null) mice had increased lung edema and permeability, indicating a previously unknown protective role for CHOP after prolonged hyperoxia. We conclude that hyperoxia increases CHOP expression via an ER stress-independent, PKR-dependent pathway and that increased CHOP expression protects against hyperoxia-induced lung injury.

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Liu, Yan-Yan, Christophe Leboeuf, Jing-Yi Shi, Jun-Min Li, Li Wang, Yang Shen, José-Francisco Garcia, et al. "Rituximab plus CHOP (R-CHOP) overcomes PRDM1-associated resistance to chemotherapy in patients with diffuse large B-cell lymphoma." Blood 110, no. 1 (July 1, 2007): 339–44. http://dx.doi.org/10.1182/blood-2006-09-049189.

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The positive regulatory domain I (PRDM1) is a master regulator in the differentiation of mature B lymphocytes to plasma cells. It has 2 isoforms, PRDM1α and PRDM1β, and is regulated by the transcriptional regulator nuclear factor kappa (NF)–κB. PRDM1 protein expression was recently demonstrated in a subset of diffuse large B-cell lymphoma (DLBCL) with aggressive behavior, a type of lymphoma for which rituximab associated with chemotherapy (R-CHOP) is now widely indicated. Using laser microdissection combined with reverse transcription–polymerase chain reaction (RT-PCR) amplification, PRDM1 gene expression was assessed in 82 DLBCL patients. The results showed that both PRDM1α and PRDM1β transcripts were expressed in microdissected lymphoma cells only in the non–germinal center B-cell–like (non-GCB) subtype of DLBCL. PRDM1β gene expression was correlated with short survival time in the non-GCB patients treated with CHOP but not with R-CHOP. In vitro, B-lymphoma cells resistant to chemotherapy expressed PRDM1β. Rituximab suppressed PRDM1β expression, which was concomitant with NF-κB inactivation. The value of PRDM1β expression as a prognostic marker in non-GCB DLBCL might thus be considered. This study confirms the efficiency of rituximab on DLBCL and allows a better understanding of one of its biologic actions.

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Longe, Harold, Douglas V. Faller, and Gerald V. Denis. "Telomere-Based Pre-Clinical Therapy in a Murine Model of Non-Hodgkin’s Lymphoma of the Diffuse Large B Cell (DLCL)Type." Blood 106, no. 11 (November 16, 2005): 607. http://dx.doi.org/10.1182/blood.v106.11.607.607.

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Abstract The dual bromodomain Brd2 is closely related to the basal transcription factor TAFII250, which is essential for cyclin A transactivation and mammalian cell cycle progression. Constitutive expression of BRD2 (under Eμ control) in the lymphoid lineage of transgenic mice elevates basal transcription of cyclin A, destabilizes the cell cycle and leads to B cell leukemias and lymphomas that are monoclonal, morphologically uniform, transplantable and highly malignant. The surface immunophenotype of the lymphoma cells is: B220+, CD19+, sIgM+, CD5+, CD9+; B7-1 and B7-2 elevated, CD23low; CD11b-, Ly-6G- and CD49b-, supporting lymphoid-restricted lineage; CD117- (c-kit) and CD127- (interleukin-7 receptor α-chain), consistent with mature cells; CD25-, syndecan-1-, and CD69- and exhibit a high IgM/low IgD ratio, which taken together identify a B-1 cell type. Malignant, proliferating cells infiltrate lymph nodes, liver, lung and kidney, and at late stages, cause anemia and a fatal peripheral leukemia over a 14-day time course from tumor cell transplantation to death. Genome-wide transcriptional expression profiling of these lymphoma cells reveals a transcriptional fingerprint that is most similar to human diffuse large B cell lymphoma (DLCL) with an “activated B cell” signature, consistent with histopathology, and establishes a novel murine DLCL model. DLCL is the most common type of non-Hodgkin’s lymphoma (NHL) in humans; all lymphomas combined are the fifth most common type of cancer diagnosed and the sixth most common cause of death in the United States. We treated syngeneic transplanted mice with CHOP (i.e. cyclophosphamide 40 mg/kg i.v., doxorubicin 3.3 mg/kg i.v., vincristine 0.5 mg/kg i.v. and predisone 0.2 mg/kg p.o. every day for 14 days) and monitored individual lymphoma cells, tagged with human-CD4+, by flow cytometry of lymphoid and non-lymphoid organs. In a novel approach, we supplemented CHOP with DNA oligonucleotides that mimic the chromosomal telomere, which we call a “T-oligo.” Normal cells exposed to this drug in vitro undergo transient cell cycle arrest, but DLCL cells undergo p53-dependent apoptosis. The mechanism immediately suggests a novel method of chemotherapy for leukemia and lymphoma to supplement CHOP. In mice treated systemically with CHOP and T-oligo, we observed major reductions in the leukemic burden in peripheral blood, reduced lymphadenopathy, reduced leukemic infiltrates of non-lymphoid organs and splenomegaly in the combined (“CHOP+T”) regimen over CHOP alone. We also confirmed in normal B lymphocytes that T-oligo causes only cell cycle arrest, not apoptosis. Mice likewise showed low toxicity to T-oligo at the effective doses, opening the way to a more extensive pre-clinical trial of this novel approach to NHL therapy.

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Xu, Linhao, Yanli Bi, Yizhou Xu, Yihao Wu, Xiaoxue Du, Yixuan Mou, and Jian Chen. "Suppression of CHOP Reduces Neuronal Apoptosis and Rescues Cognitive Impairment Induced by Intermittent Hypoxia by Inhibiting Bax and Bak Activation." Neural Plasticity 2021 (August 21, 2021): 1–14. http://dx.doi.org/10.1155/2021/4090441.

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Our previous study showed that growth arrest- and DNA damage-inducible gene 153 (GAD153/CHOP) plays an important role in intermittent hypoxia- (IH-) induced apoptosis and impaired synaptic plasticity. This study is aimed at determining which signaling pathway is activated to induce CHOP and the role of this protein in mitochondria-dependent apoptosis induced by IH. In the in vivo study, mice were placed in IH chambers for 8 h daily over a period of 2 weeks; the IH chambers had oxygen (O2) concentrations that oscillated between 10% and 21%, cycling every 90 s. In the in vitro study, PC12 cells were exposed to 21% O2 (normoxia) or 8 IH cycles (25 min at 21% O2 and 35 min at 0.1% O2 for each cycle). After 2 weeks of IH treatment, we observed that the expression levels of phosphorylated protein kinase-like endoplasmic reticulum kinase (p-PERK), activating transcription factor 4 (ATF-4) and phosphorylated eukaryotic initiation factor 2 alpha (p-elf2α), were increased, but the levels of activating transcription factor 6 (ATF-6) and inositol-requiring enzyme 1 (IRE-1) were not increased. GSK2606414, a specific chemical inhibitor of the PERK pathway, reduced the expression of p-PERK, ATF-4, p-elf2α, and CHOP and rescued ER structure. In addition, Bax and Bak accumulated in the mitochondria after IH treatment, which induced cytochrome c release and initiated apoptosis. These effects were prevented by GSK2606414 and CHOP shRNA. Finally, the impaired long-term potentiation and long-term spatial memory in the IH group were rescued by GSK2606414. Together, the data from the in vitro and in vivo experiments indicate that IH-induced apoptosis and impaired synaptic plasticity were mediated by the PERK-ATF-4-CHOP pathway. Suppressing PERK-ATF-4-CHOP signaling pathway attenuated mitochondria-dependent apoptosis by reducing the expression of Bax and Bak in mitochondria, which may serve as novel adjunct therapeutic strategy for ameliorating obstructive sleep apnea- (OSA-) induced neurocognitive impairment.

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Tchkonia, Tamara, Tamar Pirtskhalava, Thomas Thomou, Mark J. Cartwright, Barton Wise, Iordanes Karagiannides, Alexander Shpilman, Timothy L. Lash, J. David Becherer, and James L. Kirkland. "Increased TNFα and CCAAT/enhancer-binding protein homologous protein with aging predispose preadipocytes to resist adipogenesis." American Journal of Physiology-Endocrinology and Metabolism 293, no. 6 (December 2007): E1810—E1819. http://dx.doi.org/10.1152/ajpendo.00295.2007.

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Fat depot sizes peak in middle age but decrease by advanced old age. This phenomenon is associated with ectopic fat deposition, decreased adipocyte size, impaired differentiation of preadipocytes into fat cells, decreased adipogenic transcription factor expression, and increased fat tissue inflammatory cytokine generation. To define the mechanisms contributing to impaired adipogenesis with aging, we examined the release of TNFα, which inhibits adipogenesis, and the expression of CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP), which blocks activity of adipogenic C/EBP family members, in preadipocytes cultured from young, middle-aged, and old rats. Medium conditioned by fat tissue, as well as preadipocytes, from old rats impeded lipid accumulation by preadipocytes from young animals. More TNFα was released by preadipocytes from old than young rats. Differences in TNFα-converting enzyme, TNFα degradation, or the presence of macrophages in cultures were not responsible. TNFα induced rat preadipocyte CHOP expression. CHOP was higher in undifferentiated preadipocytes from old than younger animals. Overexpression of CHOP in young rat preadipocytes inhibited lipid accumulation. TNFα short interference RNA reduced CHOP and partially restored lipid accumulation in old rat preadipocytes. CHOP normally increases during late differentiation, potentially modulating the process. This late increase in CHOP was not affected substantially by aging: CHOP was similar in differentiating preadipocytes and fat tissue from old and young animals. Hypoglycemia, which normally causes an adaptive increase in CHOP, was less effective in inducing CHOP in preadipocytes from old than younger animals. Thus increased TNFα release by undifferentiated preadipocytes with elevated basal CHOP contributes to impaired adipogenesis with aging.

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Willy, Jeffrey A., Sara K. Young, James L. Stevens, Howard C. Masuoka, and Ronald C. Wek. "CHOP links endoplasmic reticulum stress to NF-κB activation in the pathogenesis of nonalcoholic steatohepatitis." Molecular Biology of the Cell 26, no. 12 (June 15, 2015): 2190–204. http://dx.doi.org/10.1091/mbc.e15-01-0036.

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Free fatty acid induction of inflammation and cell death is an important feature of nonalcoholic steatohepatitis (NASH) and has been associated with disruption of the endoplasmic reticulum and activation of the unfolded protein response (UPR). After chronic UPR activation, the transcription factor CHOP (GADD153/DDIT3) triggers cell death; however, the mechanisms linking the UPR or CHOP to hepatoceullular injury and inflammation in the pathogenesis of NASH are not well understood. Using HepG2 and primary human hepatocytes, we found that CHOP induces cell death and inflammatory responses after saturated free fatty acid exposure by activating NF-κB through a pathway involving IRAK2 expression, resulting in secretion of cytokines IL-8 and TNFα directly from hepatocytes. TNFα facilitates hepatocyte death upon exposure to saturated free fatty acids, and secretion of both IL-8 and TNFα contribute to inflammation. Of interest, CHOP/NF-κB signaling is not conserved in primary rodent hepatocytes. Our studies suggest that CHOP plays a vital role in the pathophysiology of NASH by induction of secreted factors that trigger inflammation and hepatocellular death via a signaling pathway specific to human hepatocytes.

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Yoneshima, Erika, Kuniaki Okamoto, Eiko Sakai, Kazuhisa Nishishita, Noriaki Yoshida, and Takayuki Tsukuba. "The Transcription Factor EB (TFEB) Regulates Osteoblast Differentiation Through ATF4/CHOP-Dependent Pathway." Journal of Cellular Physiology 231, no. 6 (November 20, 2015): 1321–33. http://dx.doi.org/10.1002/jcp.25235.

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Vij, Neeraj, Martha O. Amoako, Steven Mazur, and Pamela L. Zeitlin. "CHOP Transcription Factor Mediates IL-8 Signaling in Cystic Fibrosis Bronchial Epithelial Cells." American Journal of Respiratory Cell and Molecular Biology 38, no. 2 (February 2008): 176–84. http://dx.doi.org/10.1165/rcmb.2007-0197oc.

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Bromati, Carla R., Camilo Lellis-Santos, Tatiana S. Yamanaka, Tatiane C. A. Nogueira, Mauro Leonelli, Luciana C. Caperuto, Renata Gorjão, Adriana R. Leite, Gabriel F. Anhê, and Silvana Bordin. "UPR induces transient burst of apoptosis in islets of early lactating rats through reduced AKT phosphorylation via ATF4/CHOP stimulation of TRB3 expression." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 300, no. 1 (January 2011): R92—R100. http://dx.doi.org/10.1152/ajpregu.00169.2010.

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Endocrine pancreas from pregnant rats undergoes several adaptations that comprise increase in β-cell number, mass and insulin secretion, and reduction of apoptosis. Lactogens are the main hormones that account for these changes. Maternal pancreas, however, returns to a nonpregnant state just after the delivery. The precise mechanism by which this reversal occurs is not settled but, in spite of high lactogen levels, a transient increase in apoptosis was already reported as early as the 3rd day of lactation (L3). Our results revealed that maternal islets displayed a transient increase in DNA fragmentation at L3, in parallel with decreased RAC-alpha serine/threonine-protein kinase (AKT) phosphorylation (pAKT), a known prosurvival kinase. Wortmannin completely abolished the prosurvival action of prolactin (PRL) in cultured islets. Decreased pAKT in L3-islets correlated with increased Tribble 3 (TRB3) expression, a pseudokinase inhibitor of AKT. PERK and eIF2α phosphorylation transiently increased in islets from rats at the first day after delivery, followed by an increase in immunoglobulin heavy chain-binding protein (BiP), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP) in islets from L3 rats. Chromatin immunoprecipitation (ChIP) and Re-ChIP experiments further confirmed increased binding of the heterodimer ATF4/CHOP to the TRB3 promoter in L3 islets. Treatment with PBA, a chemical chaperone that inhibits UPR, restored pAKT levels and inhibited the increase in apoptosis found in L3. Moreover, PBA reduced CHOP and TRB3 levels in β-cell from L3 rats. Altogether, our study collects compelling evidence that UPR underlies the physiological and transient increase in β-cell apoptosis after delivery. The UPR is likely to counteract prosurvival actions of PRL by reducing pAKT through ATF4/CHOP-induced TRB3 expression.

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Fusakio, Michael E., Jeffrey A. Willy, Yongping Wang, Emily T. Mirek, Rana J. T. Al Baghdadi, Christopher M. Adams, Tracy G. Anthony, and Ronald C. Wek. "Transcription factor ATF4 directs basal and stress-induced gene expression in the unfolded protein response and cholesterol metabolism in the liver." Molecular Biology of the Cell 27, no. 9 (May 2016): 1536–51. http://dx.doi.org/10.1091/mbc.e16-01-0039.

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Disturbances in protein folding and membrane compositions in the endoplasmic reticulum (ER) elicit the unfolded protein response (UPR). Each of three UPR sensory proteins—PERK (PEK/EIF2AK3), IRE1, and ATF6—is activated by ER stress. PERK phosphorylation of eIF2 represses global protein synthesis, lowering influx of nascent polypeptides into the stressed ER, coincident with preferential translation of ATF4 (CREB2). In cultured cells, ATF4 induces transcriptional expression of genes directed by the PERK arm of the UPR, including genes involved in amino acid metabolism, resistance to oxidative stress, and the proapoptotic transcription factor CHOP (GADD153/DDIT3). In this study, we characterize whole-body and tissue-specific ATF4-knockout mice and show in liver exposed to ER stress that ATF4 is not required for CHOP expression, but instead ATF6 is a primary inducer. RNA-Seq analysis indicates that ATF4 is responsible for a small portion of the PERK-dependent UPR genes and reveals a requirement for expression of ATF4 for expression of genes involved in oxidative stress response basally and cholesterol metabolism both basally and under stress. Consistent with this pattern of gene expression, loss of ATF4 resulted in enhanced oxidative damage, and increased free cholesterol in liver under stress accompanied by lowered cholesterol in sera.

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Carrière, Audrey, Maria-Carmen Carmona, Yvette Fernandez, Michel Rigoulet, Roland H. Wenger, Luc Pénicaud, and Louis Casteilla. "Mitochondrial Reactive Oxygen Species Control the Transcription Factor CHOP-10/GADD153 and Adipocyte Differentiation." Journal of Biological Chemistry 279, no. 39 (July 20, 2004): 40462–69. http://dx.doi.org/10.1074/jbc.m407258200.

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DeZwaan-McCabe, Diane, Jesse D. Riordan, Angela M. Arensdorf, Michael S. Icardi, Adam J. Dupuy, and D. Thomas Rutkowski. "The Stress-Regulated Transcription Factor CHOP Promotes Hepatic Inflammatory Gene Expression, Fibrosis, and Oncogenesis." PLoS Genetics 9, no. 12 (December 19, 2013): e1003937. http://dx.doi.org/10.1371/journal.pgen.1003937.

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Evens, Andrew M., Laurie H. Sehn, Pedro Farinha, Paul T. Schumacker, Adekunle Raji, Yi Lu, Beverly P. Nelson, Randy D. Gascoyne, and Leo I. Gordon. "Expression of Hypoxia-Inducible Factor (HIF) Is An Independent Favorable Prognostic Factor in Diffuse Large B-Cell Lymphoma (DLBCL) Treated with R-CHOP." Blood 112, no. 11 (November 16, 2008): 479. http://dx.doi.org/10.1182/blood.v112.11.479.479.

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Abstract HIF is a transcription factor that regulates gene expression in response to decreases in cellular oxygenation (hypoxia). Genes activated by HIF are involved in glycolysis, glucose transport, angiogenesis, cell proliferation, cell migration, cell metabolism, and cell survival. Many of these genes confer protection against the consequences of oxygen deprivation while others enhance resistance to chemotherapy or radiotherapy. Clinically, evidence of elevated HIF protein correlates with poor prognosis in lung, breast, colorectal, brain, pancreatic, ovarian, renal, and bladder cancers. Our preliminary tissue micro array (TMA) data suggested that HIF is frequently stabilized in lymphoma (BJH2008; 141:676), especially among patients with diffuse large B-cell lymphoma (DLBCL). We also found that constitutive expression of HIF-1α and/or HIF-2α is stabilized in a set of established lymphoma cell lines, underscoring the potential impact of HIF in lymphoma. To further investigate the importance of HIF, we examined TMAs for HIF-1α expression from 153 patients with DLBCL treated with CHOP or rituximab-CHOP (R-CHOP) at the BCCA between 1999–2002. Treatment was before (pre-rituximab) and after (post-rituximab) institution of a policy recommending the combination of rituximab with CHOP for all patients with newly diagnosed advanced-stage DLBCL (March 2001). Tissue sections were stained with monoclonal antibody to HIF-1α and expression (nuclear) was scored by computer (Automated Cellular Imaging System) and validated by pathology review. HIF was dichotomized as either negative (neg; no HIF staining) or positive (pos; score of 1 or greater). Of the 153 patients, 78 were consecutively treated with R-CHOP, while 75 had received CHOP. We found HIF pos expression in 63% (49/78) of patients treated with R-CHOP and 59% (44/75) treated with CHOP (p=NS). Further, based on the Hans algorithm, HIF was expressed in 62% of germinal center (GC) patients and 59% of non-GC patients (P=NS). In the R-CHOP group (see Figure 1A and 1B), the 5-year progression-free survival (PFS) was 45% for HIF neg patients vs 62% for HIF pos (log rank p=0.0187); while the 5-year overall survival (OS) was 48% for HIF neg vs 76% for HIF pos (log rank p=0.025). In patients treated with CHOP, there was no difference in outcome between HIF pos and HIF neg subsets. In multivariate analysis in the R-CHOP treated group, controlling for the International Prognostic Index (IPI), HIF pos expression remained a significant independent predictor for OS (p=0.03), while the IPI was of borderline significance (p=0.051). Comparison with other biomarkers showed that HIF did not correlate with expression of bcl-2, CD10, MUM-1, or FOXP1; while a high correlation was detected with bcl-6 and HIF (among HIF pos R-CHOP patients, 94% were bcl-6 pos and 6% were bcl-6 neg; p=0.004). We conclude that expression of HIF-1α is an important and heretofore undiscovered independent favorable prognostic factor for PFS and OS in DLBCL patients treated with R-CHOP, but not in patients treated with CHOP. These data suggest there may be an important biological interaction between CD20 monoclonal antibody-based therapy and HIF or downstream genes regulated by HIF. Further study of this observation is warranted. Figure 1. Survival according to HIF-1α status in patients treated with R-CHOP. Figure 1. Survival according to HIF-1α status in patients treated with R-CHOP.

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GABEEVA, N. G., E. E. ZVONKOV, D. A. KOROLEVA, M. M. CHUKAVINA, T. N. OBUKHOVA, and A. M. KOVRIGINA. "Successful experience of treatment of a patient with generalized non-GCB- DLBCL using the R-mNHL-BFM-90 protocol with lenalidomide: case report and review of literature." Terapevticheskii arkhiv 90, no. 7 (July 15, 2018): 96–101. http://dx.doi.org/10.26442/terarkh201890796-101.

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Diffuse large B-cell lymphoma is categorized by gene expression profiling into germinal center (GCB) and activated B-cell (ABC) subtype, also referred to as non-germinal center B-cell (non-GCB) by immunohistochemistry. ABC DLBCL is characterized by NF-κB pathway activation and high expression of IRF4/MUM1, a key transcription factor in B cell differentiation. Patients with ABC DLBCL have a significantly worse outcome when treated with standard chemotherapy (R-CHOP). Lenalidomide have shown activity in the ABC-DLBCL in combination with R-CHOP. But about 40% of patients remain resistant. We present the experience of treatment of a patient with generalized non-GCB-DLBCL using the intensive protocol R-mNHL-BFM-90 with lenalidomide.

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Wu, Yueh-Lin, Heng Lin, Hsiao-Fen Li, Ming-Jaw Don, Pei-Chih King, and Hsi-Hsien Chen. "Salvia miltiorrhiza Extract and Individual Synthesized Component Derivatives Induce Activating-Transcription-Factor-3-Mediated Anti-Obesity Effects and Attenuate Obesity-Induced Metabolic Disorder by Suppressing C/EBPα in High-Fat-Induced Obese Mice." Cells 11, no. 6 (March 17, 2022): 1022. http://dx.doi.org/10.3390/cells11061022.

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Pharmacological studies indicate that Salvia miltiorrhiza extract (SME) can improve cardiac and blood vessel function. However, there is limited knowledge regarding the effects (exerted through epigenetic regulation) of SME and newly derived single compounds, with the exception of tanshinone IIA and IB, on obesity-induced metabolic disorders. In this study, we administered SME or dimethyl sulfoxide (DMSO) as controls to male C57BL/J6 mice after they were fed a high-fat diet (HFD) for 4 weeks. SME treatment significantly reduced body weight, fasting plasma glucose, triglyceride levels, insulin resistance, and adipogenesis/lipogenesis gene expression in treated mice compared with controls. Transcriptome array analysis revealed that the expression of numerous transcriptional factors, including activating transcription factor 3 (ATF3) and C/EBPα homologous protein (CHOP), was significantly higher in the SME group. ST32db, a novel synthetic derivative similar in structure to compounds from S. miltiorrhiza extract, ameliorates obesity and obesity-induced metabolic syndrome in HFD-fed wild-type mice but not ATF3−/− mice. ST32db treatment of 3T3-L1 adipocytes suppresses lipogenesis/adipogenesis through the ATF3 pathway to directly inhibit C/EBPα expression and indirectly inhibit the CHOP pathway. Overall, ST32db, a single compound modified from S. miltiorrhiza extract, has anti-obesity effects through ATF3-mediated C/EBPα downregulation and the CHOP pathway. Thus, SME and ST32db may reduce obesity and diabetes in mice, indicating the potential of both SME and ST32db as therapeutic drugs for the treatment of obesity-induced metabolic syndrome.

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Bruhat, Alain, Céline Jousse, and Pierre Fafournoux. "Amino acid limitation regulates gene expression." Proceedings of the Nutrition Society 58, no. 3 (August 1999): 625–32. http://dx.doi.org/10.1017/s0029665199000828.

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In mammals, the plasma concentration of amino acids is affected by nutritional or pathological conditions. For example, an alteration in the amino acid profile has been reported when there is a deficiency of any one or more of the essential amino acids, a dietary imbalance of amino acids, or an insufficient intake of protein. We examined the role of amino acid limitation in regulating mammalian gene expression. Depletion of arginine, cystine and all essential amino acids leads to induction of insulin-like growth factor-binding protein-1 (IGFBP-1) mRNA and protein expression in a dose-dependent manner. Moreover, exposure of HepG2 cells to amino acids at a concentration reproducing the amino acid concentration found in portal blood of rats fed on a low-protein diet leads to a significantly higher (P < 0·0002) expression of IGFBP-1. Using CCAAT/enhancer-binding protein homologous protein (CHOP) induction by leucine deprivation as a model, we have characterized the molecular mechanisms involved in the regulation of gene expression by amino acids. We have shown that leucine limitation leads to induction of CHOP mRNA and protein. Elevated mRNA levels result from both an increase in the rate of CHOP transcription and an increase in mRNA stability. We have characterized two elements of the CHOP gene that are essential to the transcriptional activation produced by an amino acid limitation. These findings demonstrate that an amino acid limitation, as occurs during dietary protein deficiency, can induce gene expression. Thus, amino acids by themselves can play, in concert with hormones, an important role in the control of gene expression.

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Zhang, Rui, Jin Sook Kim, Kyoung Ah Kang, Mei Jing Piao, Ki Cheon Kim, and Jin Won Hyun. "Protective Mechanism of KIOM-4 in Streptozotocin-Induced Pancreatic β-Cells Damage Is Involved in the Inhibition of Endoplasmic Reticulum Stress." Evidence-Based Complementary and Alternative Medicine 2011 (2011): 1–10. http://dx.doi.org/10.1155/2011/231938.

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Endoplasmic reticulum stress-mediated apoptosis plays an important role in the destruction of pancreaticβ-cells and contributes to the development of type 1 diabetes. The present study examined the effect of KIOM-4, a mixture of four plant extracts, on streptozotocin- (STZ-) induced endoplasmic reticulum (ER) stress in rat pancreaticβ-cells (RINm5F). KIOM-4 was found to inhibit STZ-induced apoptotic cell death, confirmed by formation of apoptotic bodies and DNA fragmentation. STZ was found to induce the characteristics of ER stress; mitochondrial Ca2+overloading, enhanced ER staining, release of glucose-regulated protein 78 (GRP78), phosphorylation of RNA-dependent protein kinase (PKR) like ER kinase (PERK) and eukaryotic initiation factor-2α(eIF-2α), cleavage of activating transcription factor 6 (ATF6) and caspase 12, and upregulation of CCAAT/enhancer-binding protein-homologous protein (CHOP). However, KIOM-4 attenuated these changes induced by STZ. Furthermore, KIOM-4 suppressed apoptosis induced by STZ in CHOP downregulated cells using CHOP siRNA. These results suggest that KIOM-4 exhibits protective effects in STZ-induced pancreaticβ-cell damage, by interrupting the ER stress-mediated pathway.

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Behrman, Shannon, Diego Acosta-Alvear, and Peter Walter. "A CHOP-regulated microRNA controls rhodopsin expression." Journal of Cell Biology 192, no. 6 (March 14, 2011): 919–27. http://dx.doi.org/10.1083/jcb.201010055.

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Using genome-wide microribonucleic acid (microRNA [miRNA]) expression profiling, bioinformatics, and biochemical analyses, we identified miR-708, an endoplasmic reticulum (ER) stress-inducible miRNA whose expression is regulated by the transcription factor CCAAT enhancer-binding protein homologous protein (CHOP) in vertebrates. miR-708 is encoded within an intron of the CHOP-regulated gene Odz4, a member of the highly conserved teneurin family of developmental regulators. Odz4 and mir-708 expression is coregulated by CHOP, and the two transcripts are coexpressed in the brain and eyes of mice, suggesting common physiological functions in these tissues. We validated rhodopsin as a target of miR-708 through loss- and gain-of-function experiments. Together, our data implicate miR-708 in the homeostatic regulation of ER function in mammalian rod photoreceptors, whereby miR-708 may help prevent an excessive rhodopsin load from entering the ER. Hence, miR-708 may function analogously to other unfolded protein response controls that throttle protein influx into the ER to avoid ER stress through mechanisms, such as general translational attenuation by protein kinase RNA–like ER kinase or membrane-bound messenger RNA decay by inositol-requiring enzyme 1.

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Nicoletti-Carvalho, José Edgar, Tatiane C. Araújo Nogueira, Renata Gorjão, Carla Rodrigues Bromati, Tatiana S. Yamanaka, Antonio Carlos Boschero, Licio Augusto Velloso, Rui Curi, Gabriel Forato Anhê, and Silvana Bordin. "UPR-mediated TRIB3 expression correlates with reduced AKT phosphorylation and inability of interleukin 6 to overcome palmitate-induced apoptosis in RINm5F cells." Journal of Endocrinology 206, no. 2 (May 20, 2010): 183–93. http://dx.doi.org/10.1677/joe-09-0356.

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Unfolded protein response (UPR)-mediated pancreatic β-cell death has been described as a common mechanism by which palmitate (PA) and pro-inflammatory cytokines contribute to the development of diabetes. There are evidences that interleukin 6 (IL6) has a protective action against β-cell death induced by pro-inflammatory cytokines; the effects of IL6 on PA-induced apoptosis have not been investigated yet. In the present study, we have demonstrated that PA selectively disrupts IL6-induced RAC-alpha serine/threonine-protein kinase (AKT) activation without interfering with signal transducer and activator of transcription 3 phosphorylation in RINm5F cells. The inability of IL6 to activate AKT in the presence of PA correlated with an inefficient protection against PA-induced apoptosis. In contrast to PA, IL6 efficiently reduced apoptosis induced by pro-inflammatory cytokines. In addition, we have demonstrated that IL6 is unable to overcome PA-stimulated UPR, as assessed by activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP) expression, X-box binding protein-1 gene mRNA splicing, and pancreatic eukaryotic initiation factor-2α kinase phosphorylation, whereas no significant induction of UPR by pro-inflammatory cytokines was detected. This unconditional stimulation of UPR and apoptosis by PA was accompanied by the stimulation of CHOP and tribble3 (TRIB3) expression, irrespective of the presence of IL6. These findings suggest that IL6 is unable to protect pancreatic β-cells from PA-induced apoptosis because it does not repress UPR activation. In this way, CHOP and ATF4 might mediate PA-induced TRIB3 expression and, by extension, the suppression of IL6 activation of pro-survival kinase AKT.

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Wang, X. Z., and D. Ron. "Stress-Induced Phosphorylation and Activation of the Transcription Factor CHOP (GADD153) by p38 MAP Kinase." Science 272, no. 5266 (May 31, 1996): 1347–49. http://dx.doi.org/10.1126/science.272.5266.1347.

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Goodall, Jane C., Changxin Wu, Yongsheng Zhang, Louise McNeill, Lou Ellis, Vladimir Saudek, and J. S. Hill Gaston. "Endoplasmic reticulum stress-induced transcription factor, CHOP, is crucial for dendritic cell IL-23 expression." Proceedings of the National Academy of Sciences 107, no. 41 (September 27, 2010): 17698–703. http://dx.doi.org/10.1073/pnas.1011736107.

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Her, Guor Mour, Wan-Yu Pai, Chi-Yu Lai, Yang-Wen Hsieh, and Hsi-Wen Pang. "Ubiquitous transcription factor YY1 promotes zebrafish liver steatosis and lipotoxicity by inhibiting CHOP-10 expression." Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 1831, no. 6 (June 2013): 1037–51. http://dx.doi.org/10.1016/j.bbalip.2013.02.002.

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Huang, Xiaoli, Li Li, Linyou Zhang, Zhihong Zhang, Xiaolin Wang, Xuguang Zhang, Liying Hou, and Kun Wu. "Crosstalk between endoplasmic reticulum stress and oxidative stress in apoptosis induced by α-tocopheryl succinate in human gastric carcinoma cells." British Journal of Nutrition 109, no. 4 (June 7, 2012): 727–35. http://dx.doi.org/10.1017/s0007114512001882.

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α-Tocopheryl succinate (α-TOS) has been shown to be a potent apoptosis inducer and growth inhibitor in a variety of cancer cells. Our previous studies showed the important role of endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation in the apoptosis induced by α-TOS. However, the relationship of oxidative stress with ER stress is still controversial. The objective of the present study was to investigate the interplay between the two stress responses induced by α-TOS in SGC-7901 human gastric cancer cells. In response to α-TOS, cytological changes typical of apoptosis, induction of glucose-regulated protein 78 (GRP78) and CCAAT/enhancer-binding protein (C/EBP) homologous protein transcription factor (CHOP), and activation of caspase-4 were observed. And the antioxidant N-acetyl-l-cysteine inhibited induction of both GRP78 and CHOP by α-TOS transcriptionally and translationally. Furthermore, knocking down CHOP by RNA interference decreased ROS generation, increased glutathione level and induced glutathione peroxidase mRNA expression in α-TOS-treated cells, whereas catalase and superoxide dismutases mRNA expression were not altered. The results imply that α-TOS induces ER stress response through ROS production, while CHOP perturbs the redox state of SGC-7901 cells treated with α-TOS.

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Panganiban, Ronald A., Hae-Ryung Park, Maoyun Sun, Maya Shumyatcher, Blanca E. Himes, and Quan Lu. "Genome-wide CRISPR screen identifies suppressors of endoplasmic reticulum stress-induced apoptosis." Proceedings of the National Academy of Sciences 116, no. 27 (June 18, 2019): 13384–93. http://dx.doi.org/10.1073/pnas.1906275116.

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Sensing misfolded proteins in the endoplasmic reticulum (ER), cells initiate the ER stress response and, when overwhelmed, undergo apoptosis. However, little is known about how cells prevent excessive ER stress response and cell death to restore homeostasis. Here, we report the identification and characterization of cellular suppressors of ER stress-induced apoptosis. Using a genome-wide CRISPR library, we screen for genes whose inactivation further increases ER stress-induced up-regulation of C/EBP homologous protein 10 (CHOP)—the transcription factor central to ER stress-associated apoptosis. Among the top validated hits are two interacting components of the polycomb repressive complex (L3MBTL2 [L(3)Mbt-Like 2] and MGA [MAX gene associated]), and microRNA-124-3 (miR-124-3). CRISPR knockout of these genes increases CHOP expression and sensitizes cells to apoptosis induced by multiple ER stressors, while overexpression confers the opposite effects. L3MBTL2 associates with the CHOP promoter in unstressed cells to repress CHOP induction but dissociates from the promoter in the presence of ER stress, whereas miR-124-3 directly targets the IRE1 branch of the ER stress pathway. Our study reveals distinct mechanisms that suppress ER stress-induced apoptosis and may lead to a better understanding of diseases whose pathogenesis is linked to overactive ER stress response.

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Kim, Hyun-Ju, Inamullah Khan, Adnan Shahidullah, Syed Muhammad Ashhad Halimi, Abdur Rauf, Ji-Young Lee, Young-Jin Kim, Bong-Youn Kim, and Wansu Park. "Diospyrin Modulates Inflammation in Poly I:C-Induced Macrophages via ER Stress-Induced Calcium-CHOP Pathway." Processes 8, no. 9 (August 27, 2020): 1050. http://dx.doi.org/10.3390/pr8091050.

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Diospyrin, plant-derived bisnaphthoquinonoid, is known to have anticancer activity. However, pharmacological activity of diospyrin on viral infection is not well known. We investigated effects of diospyrin on macrophages induced by polyinosinic-polycytidylic acid (poly I:C), a mimic of double-stranded viral RNA. Various cytokines, intracellular calcium, nitric oxide (NO), phosphorylated p38 MAPK, and phosphorylated ERK1/2 as well as mRNA expressions of transcription factors were evaluated. Diospyrin significantly reduced NO production, granulocyte-macrophage colony-stimulating factor production, and intracellular calcium release in poly I:C-induced RAW 264.7. The phosphorylation of p38 MAPK and ERK1/2 was also significantly suppressed. Additionally, diospyrin inhibited mRNA levels of nitric oxide synthase 2, C/EBP homologous protein (CHOP), calcium/calmodulin dependent protein kinase II alpha, signal transducers and activators of transcription 1 (STAT1), STAT3, STAT4, Janus kinase 2, first apoptosis signal receptor, c-Jun, and c-Fos in poly I:C-induced RAW 264.7. Taken together, this study represents that diospyrin might have the inhibitory activity against viral inflammation such as excessive production of inflammatory mediators in poly I:C-induced RAW 264.7 via ER stress-induced calcium-CHOP pathway.

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Journal articles on the topic 'Facteur de transcription CHOP'

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