scholarly journals Inhibition of phosphatidylcholine synthesis induces expression of the endoplasmic reticulum stress and apoptosis-related protein CCAAT/enhancer-binding protein-homologous protein (CHOP/GADD153)

2003 ◽  
Vol 369 (3) ◽  
pp. 643-650 ◽  
Author(s):  
Michiel H.M. van der SANDEN ◽  
Martin HOUWELING ◽  
Lambert M.G. van GOLDE ◽  
Arie B. VAANDRAGER
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Er Stress ◽  
Binding Protein ◽  
Related Protein ◽  
Unfolded Proteins ◽  
Homologous Protein ◽  
Er Stress Response ◽  
Enhancer Binding Protein ◽  
Ccaat Enhancer Binding Protein

Inhibition of de novo synthesis of phosphatidylcholine (PC) by some anti-cancer drugs such as hexadecylphosphocholine leads to apoptosis in various cell lines. Likewise, in MT58, a mutant Chinese hamster ovary (CHO) cell line containing a thermo-sensitive mutation in CTP:phosphocholine cytidylyltransferase (CT), an important regulatory enzyme in the CDP-choline pathway, inhibition of PC synthesis causes PC depletion. Cellular perturbations like metabolic insults and unfolded proteins can be registered by the endoplasmic reticulum (ER) and result in ER stress responses, which can lead eventually to apoptosis. In this study we investigated the effect of PC depletion on the ER stress response and ER-related proteins. Shifting MT58 cells to the non-permissive temperature of 40°C resulted in PC depletion via an inhibition of CT within 24h. Early apoptotic features appeared in several cells around 30h, and most cells were apoptotic within 48h. The temperature shift in MT58 led to an increase of pro-apoptotic CCAAT/enhancer-binding protein-homologous protein (CHOP; also known as GADD153) after 16h, to a maximum at 24h. Incubation of wild-type CHO-K1 or CT-expressing MT58 cells at 40°C did not induce differences in CHOP protein levels in time. In contrast, expression of the ER chaperone BiP/GRP78, induced by an increase in misfolded/unfolded proteins, and caspase 12, a protease specifically involved in apoptosis that results from stress in the ER, did not differ between MT58 and CHO-K1 cells in time when cultured at 40°C. Furthermore, heat-shock protein 70, a protein that is stimulated by accumulation of abnormal proteins and heat stress, displayed similar expression patterns in MT58 and K1 cells. These results suggest that PC depletion in MT58 induces the ER-stress-related protein CHOP, without raising a general ER stress response.

scholarly journals Reducing endoplasmic reticulum stress does not improve steatohepatitis in mice fed a methionine- and choline-deficient diet

2012 ◽  
Vol 303 (1) ◽  
pp. G54-G59 ◽  
Author(s):  
Anne S. Henkel ◽  
Amanda M. Dewey ◽  
Kristy A. Anderson ◽  
Shantel Olivares ◽  
Richard M. Green
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Er Stress ◽  
Hepatic Steatosis ◽  
Binding Protein ◽  
Mrna Levels ◽  
Primary Role ◽  
Chemical Chaperones ◽  
Er Stress Response ◽  
Markers Of Inflammation

Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of nonalcoholic steatohepatitis. The ER stress response is activated in the livers of mice fed a methionine- and choline-deficient (MCD) diet, yet the role of ER stress in the pathogenesis of MCD diet-induced steatohepatitis is unknown. Using chemical chaperones on hepatic steatosis and markers of inflammation and fibrosis in mice fed a MCD diet, we aim to determine the effects of reducing ER stress. C57BL/6J mice were fed a MCD diet with or without the ER chemical chaperones 4-phenylbutyric acid (PBA) and tauroursodeoxycholic acid (TUDCA) for 2 wk. TUDCA and PBA effectively attenuated the ER stress response in MCD diet-fed mice, as evidenced by reduced protein levels of phosphorylated eukaryotic initiation factor 2α and phosphorylated JNK and suppression of mRNA levels of CCAAT/enhancer binding protein homologous protein, glucose-regulated protein 78 kDa, and X-box binding protein 1. However, PBA and TUDCA did not decrease MCD diet-induced hepatic steatosis. MCD diet-induced hepatic inflammation, as evidenced by increased plasma alanine aminotransferase and induction of hepatic TNFα expression, was also not reduced by PBA or TUDCA. PBA and TUDCA did not attenuate MCD diet-induced upregulation of the fibrosis-associated genes tissue inhibitor of metalloproteinase-1 and matrix metalloproteinase-9. ER chemical chaperones reduce MCD diet-induced ER stress, yet they do not improve MCD diet-induced hepatic steatosis, inflammation, or activation of genes associated with fibrosis. These data suggest that although the ER stress response is activated by the MCD diet, it does not have a primary role in the pathogenesis of MCD diet-induced steatohepatitis.

scholarly journals Sigmar1 regulates endoplasmic reticulum stress-induced C/EBP-homologous protein expression in cardiomyocytes

2017 ◽  
Vol 37 (4) ◽  
Author(s):  
Shafiul Alam ◽  
Chowdhury S. Abdullah ◽  
Richa Aishwarya ◽  
A. Wayne Orr ◽  
James Traylor ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Er Stress ◽  
Neonatal Rat ◽  
Cellular Toxicity ◽  
Sigma 1 Receptor ◽  
Homologous Protein ◽  
Er Stress Response ◽  
Chop Expression ◽  
Stress Pathway

C/EBP-homologous protein (CHOP) is a ubiquitously expressed stress-inducible transcription factor robustly induced by maladaptive endoplasmic reticulum (ER) stresses in a wide variety of cells. Here, we examined a novel function of Sigma 1 receptor (Sigmar1) in regulating CHOP expression under ER stress in cardiomyocytes. We also defined Sigmar1-dependent activation of the adaptive ER-stress pathway in regulating CHOP expression. We used adenovirus-mediated Sigmar1 overexpression as well as Sigmar1 knockdown by siRNA in neonatal rat ventricular cardiomyocytes (NRCs); to induce ER stress, cardiomyocytes were treated with tunicamycin. Sigmar1-siRNA knockdown significantly increased the expression of CHOP and significantly induced cellular toxicity by sustained activation of ER stress in cardiomyocytes. Sigmar1 overexpression decreased the expression of CHOP and significantly decreased cellular toxicity in cells. Using biochemical and immunocytochemical experiments, we also defined the specific ER-stress pathway associated with Sigmar1-dependent regulation of CHOP expression and cellular toxicity. We found that Sigmar1 overexpression significantly increased inositol requiring kinase 1α (IRE1α) phosphorylation and increased spliced X-box-binding proteins (XBP1s) expression as well as nuclear localization. In contrast, Sigmar1 knockdown significantly decreased IRE1α phosphorylation and decreased XBP1s expression as well as nuclear transport. Taken together, these results indicate that Sigmar1-dependent activation of IRE1α-XBP1s ER-stress response pathways are associated with inhibition of CHOP expression and suppression of cellular toxicity. Hence, Sigmar1 is an essential component of the adaptive ER-stress response pathways eliciting cellular protection in cardiomyocytes.

scholarly journals Genome-wide CRISPR screen identifies suppressors of endoplasmic reticulum stress-induced apoptosis

2019 ◽  
Vol 116 (27) ◽  
pp. 13384-13393 ◽  
Author(s):  
Ronald A. Panganiban ◽  
Hae-Ryung Park ◽  
Maoyun Sun ◽  
Maya Shumyatcher ◽  
Blanca E. Himes ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Er Stress ◽  
Homologous Protein ◽  
Er Stress Response ◽  
Genome Wide ◽  
A Genome ◽  
Crispr Screen ◽  
Induced Apoptosis

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.

scholarly journals The endoplasmic reticulum stress response and diabetic kidney disease

2011 ◽  
Vol 300 (5) ◽  
pp. F1054-F1061 ◽  
Author(s):  
Robyn Cunard ◽  
Kumar Sharma
Keyword(s):  
Endoplasmic Reticulum ◽  
Stress Response ◽  
Kidney Disease ◽  
Er Stress ◽  
Diabetic Kidney Disease ◽  
Protein Translation ◽  
Renal Diseases ◽  
Unfolded Proteins ◽  
Diabetic Kidney ◽  
Er Stress Response

The endoplasmic reticulum (ER) folds and modifies proteins; however, during conditions of cellular stress, unfolded proteins accumulate in the ER and activate the unfolded protein response (UPR). The UPR, also referred to as the ER stress response, activates three distinct signaling cascades that are designed to globally reduce transcription and translation. The three major arms of the mammalian UPR include 1) protein kinase RNA (PKR)-like ER kinase (PERK), 2) inositol-requiring protein-1 (IRE1α), and 3) activating transcription factor-6 (ATF6) pathways. The PERK pathway rapidly attenuates protein translation, whereas the ATF6 and IRE1α cascades transcriptionally upregulate ER chaperone genes that promote proper folding and ER-associated degradation (ERAD) of proteins. This integrated response in turn allows the folding machinery of the ER to catch up with the backlog of unfolded proteins. The ER stress response plays a role in a number of pathophysiological processes, including pancreatic β-cell failure and apoptosis. The goals of the current review are to familiarize investigators with cellular and tissue activation of this response in the rodent and human diabetic kidney. Additionally, we will review therapeutic modulators of the ER stress response and discuss their efficacy in models of diabetic kidney disease. The ER stress response has both protective and deleterious features. A better understanding of the molecular pathways regulated during this process in a cell- and disease-specific manner could reveal novel therapeutic strategies in chronic renal diseases, including diabetic kidney disease.

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