CHOP mediates endoplasmic reticulum stress-induced apoptosis in Gimap5-deficient T cells.
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ABSTRACT:
SUBMITTER: Pino SC
PROVIDER: S-EPMC2674944 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:C/EBP-homologous protein (CHOP) is an important component of the endoplasmic reticulum (ER) stress response. We demonstrated the induction of ER stress in response to tunicamycin stimulation, as evidenced by increased expression of chaperone proteins Grp78, Grp94, and enhanced eukaryotic initiation factor 2 subunit 1 (eIF2α) phosphorylation in hepatocellular carcinoma cells. Tunicamycin-induced ER stress resulted in apoptosis and autophagy simultaneously. While inhibition of autophagy mediated by 3-methyladenine pretreatment or direct knockdown of LC3B promoted cell apoptosis, activation of autophagy with rapamycin decreased tunicamycin- induced apoptosis in HCC cells. Furthermore, CHOP was shown to be significantly upregulated upon treatment with tunicamycin in HCC cells. Specific knockdown of CHOP not only enhanced tunicamycin-induced autophagy, but also significantly attenuated ER stress-induced apoptosis in HCC cells. Accordingly, simultaneous inhibition of autophagy in HCC cells with CHOP-knockdown could partially resensitize ER stress-induced apoptosis. Taken together, our data indicate that CHOP may favor ER stress-induced apoptosis in HCC cells via inhibition of autophagy in vitro.
| S-EPMC5571976 | biostudies-literature
Project description:As apoptosis defects limit efficacy of anticancer agents, autophagy has been proposed as a novel strategy for radiotherapy enhancement. We previously showed that caspase-3/7 inhibition induces autophagy and promotes radiosensitivity in vitro and in vivo. Therefore, we further investigated the mechanism by which radiation triggers autophagy in caspase-3/7-deficient cells, and found the involvement of endoplasmic reticulum (ER) stress. The ER activates a survival pathway, the unfolded protein response, which involves ER-localized transmembrane proteins such as protein kinase-like ER kinase (PERK), inositol-requiring enzyme-1 and activating transcription factor-6. In this study, we found that PERK is essential for radiation-induced autophagy and radiosensitivity in caspase-3/7 double-knockout cells. Irradiation of these cells increased expression of phosphorylated-eIF2alpha. Similar results were seen after administration of tunicamycin (TM), a well-known ER stressor. Importantly, we found that the administration of TM with radiation in MCF-7 breast cancer cells, which are lacking functional caspase-3 and relatively resistant to many anticancer agents, enhances radiation sensitivity. Our findings reveal ER stress as a novel potential mechanism of radiation-induced autophagy in caspase-3/7-deficient cells and as a potential strategy to maximize efficiency of radiation therapy in breast cancer.
| S-EPMC2953962 | biostudies-literature
Project description:Bromodomain-containing protein 7 (BRD7) is a tumour suppressor that is known to regulate many pathological processes including cell growth, apoptosis and cell cycle. Endoplasmic reticulum (ER) stress-induced apoptosis plays a key role in diabetic cardiomyopathy (DCM). However, the molecular mechanism of hyperglycaemia-induced myocardial apoptosis is still unclear. We intended to determine the role of BRD7 in high glucose (HG)-induced apoptosis of cardiomyocytes. In vivo, we established a type 1 diabetic rat model by injecting a high-dose streptozotocin (STZ), and lentivirus-mediated short hairpin RNA (shRNA) was used to inhibit BRD7 expression. Rats with DCM exhibited severe myocardial remodelling, fibrosis, left ventricular dysfunction and myocardial apoptosis. The expression of BRD7 was up-regulated in the heart of diabetic rats, and inhibition of BRD7 had beneficial effects against diabetes-induced heart damage. In vitro, H9c2 cardiomyoblasts was used to investigate the mechanism of BRD7 in HG-induced apoptosis. Treating H9c2 cardiomyoblasts with HG elevated the level of BRD7 via activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and increased ER stress-induced apoptosis by detecting spliced/active X-box binding protein 1 (XBP-1s) and C/EBP homologous protein (CHOP). Furthermore, down-regulation of BRD7 attenuated HG-induced expression of CHOP via inhibiting nuclear translocation of XBP-1s without affecting the total expression of XBP-1s. In conclusion, inhibition of BRD7 appeared to protect against hyperglycaemia-induced cardiomyocyte apoptosis by inhibiting ER stress signalling pathway.
| S-EPMC5431142 | biostudies-literature
Project description:BackgroundThe endoplasmic reticulum (ER) stress response participates in many chronic inflammatory and autoimmune diseases. In the current study, we sought to examine the contribution of ER stress transducers in the pathogenesis of three principal facets of allergic asthma: inflammation, airway fibrosis, and airways hyperresponsiveness.MethodsHouse Dust Mite (HDM) was used as an allergen for in vitro and in vivo challenge of primary human and murine airway epithelial cells. ER stress transducers were modulated using specific small interfering RNAs (siRNAs) in vivo. Inflammation, airway remodeling, and hyperresponsiveness were measured by total bronchoalveolar lavage (BAL) cell counts, determination of collagen, and methacholine responsiveness in mice, respectively.ResultsChallenge of human bronchiolar and nasal epithelial cells with HDM extract induced the ER stress transducer, activating transcription factor 6 α (ATF6α) as well as protein disulfide isomerase, ERp57, in association with activation of caspase-3. SiRNA-mediated knockdown of ATF6α and ERp57 during HDM administration in mice resulted in a decrease in components of HDM-induced ER stress, disulfide mediated oligomerization of Bak, and activation of caspase-3. Furthermore, siRNA-mediated knockdown of ATF6α and ERp57 led to decreased inflammation, airway hyperresponsiveness and airway fibrosis.ConclusionCollectively, our work indicates that HDM induces ER stress in airway epithelial cells and that ATF6α and ERp57 play a significant role in the development of cardinal features of allergic airways disease. Inhibition of ER stress responses may provide a potential therapeutic avenue in chronic asthma and sub-epithelial fibrosis associated with loss of lung function.
| S-EPMC3877992 | biostudies-literature
Project description:Endoplasmic reticulum (ER) is a central organelle in eukaryotic cells that regulates protein synthesis and maturation. Perturbation of ER functions leads to ER stress, which has been previously associated with a broad variety of diseases. ER stress is generally regarded as compensatory, but prolonged ER stress has been involved in apoptosis induced by several cytotoxic agents. Choline kinase α (ChoKα), the first enzyme in the Kennedy pathway, is responsible for the generation of phosphorylcholine (PCho) that ultimately renders phosphatidylcholine. ChoKα overexpression and high PCho levels have been detected in several cancer types. Inhibition of ChoKα has demonstrated antiproliferative and antitumor properties; however, the mechanisms underlying these activities remain poorly understood. Here, we demonstrate that ChoKα inhibitors (ChoKIs), MN58b and RSM932A, induce cell death in cancer cells (T47D, MCF7, MDA-MB231, SW620 and H460), through the prolonged activation of ER stress response. Evidence of ChoKIs-induced ER stress includes enhanced production of glucose-regulated protein, 78 kDa (GRP78), protein disulfide isomerase, IRE1α, CHOP, CCAAT/enhancer-binding protein beta (C/EBPβ) and TRB3. Although partial reduction of ChoKα levels by small interfering RNA was not sufficient to increase the production of ER stress proteins, silencing of ChoKα levels also show a decrease in CHOP overproduction induced by ChoKIs, which suggests that ER stress induction is due to a change in ChoKα protein folding after binding to ChoKIs. Silencing of CHOP expression leads to a reduction in C/EBPβ, ATF3 and GRP78 protein levels and abrogates apoptosis in tumor cells after treatment with ChoKIs, suggesting that CHOP maintains ER stress responses and triggers the pro-apoptotic signal. Consistent with the differential effect of ChoKIs in cancer and primary cells previously described, ChoKIs only promoted a transient and moderated ER stress response in the non-tumorogenic cells MCF10A. In conclusion, pharmacological inhibition of ChoKα induces cancer cell death through a mechanism that involves the activation of exaggerated and persistent ER stress supported by CHOP overproduction.
| S-EPMC3847329 | biostudies-literature
Project description:This study was designed to explore the inductive effect of glycated high-density lipoprotein (gly-HDL) on endoplasmic reticulum (ER) stress-C/EBP homologous protein (CHOP)-mediated macrophage apoptosis and its relationship with autophagy. Our results showed that gly-HDL caused macrophage apoptosis with concomitant activation of ER stress pathway, including nuclear translocation of activating transcription factor 6, phosphorylation of protein kinase-like ER kinase (PERK) and eukaryotic translation initiation factor 2α, and CHOP up-regulation, which were inhibited by 4-phenylbutyric acid (PBA, an ER stress inhibitor) and the gene silencing of PERK and CHOP. Similar data were obtained from macrophages treated by HDL isolated from diabetic patients. Gly-HDL induced macrophage autophagy as assessed by up-regulation of beclin-1, autophagy-related gene 5 and microtubule-associated protein one light chain 3-II, which were depressed by PBA and PERK siRNA. Gly-HDL-induced apoptosis, PERK phosphorylation and CHOP up-regulation were suppressed by rapamycin (an autophagy inducer), whereas aggravated by 3-methyladenine (an autophagy inhibitor) and beclin-1 siRNA. Administration of diabetic apoE-/- mice with rapamycin attenuated MOMA-2 and CHOP up-regulation and apoptosis in atherosclerotic lesions. These data indicate that gly-HDL may induce macrophage apoptosis through activating ER stress-CHOP pathway and ER stress mediates gly-HDL-induced autophagy, which in turn protects macrophages against apoptosis by alleviating CHOP pathway.
| S-EPMC6433656 | biostudies-literature
Project description:Unfolded protein response (UPR) is an adaptive reaction for cells to reduce endoplasmic reticulum (ER) stress. In many types of cancers, such as lung cancer and pancreatic cancer, cancer cells may harness ER stress to facilitate their survival and growth. Prion protein (PrP) is a glycosylated cell surface protein that has been shown to be up-regulated in many cancer cells. Since PrP is a protein prone to misfolding, ER stress can result in under-glycosylated PrP, which in turn may activate ER stress. To assess whether ER stress leads to the production of under-glycosylated PrP and whether under-glycosylated PrP may contribute to ER stress thus leading to cancer cell apoptosis, we treated different cancer cells with brefeldin A (BFA), thapsigargin (Thps), and tunicamycin (TM). We found that although BFA, Thps, and TM treatment activated UPR, only ATF4 was consistently activated by these reagents, but not other branches of ER stress. However, the canonical PERK-eIF2α-ATF4 did not account for the observed activation of ATF4 in lung cancer cells. In addition, BFA, but neither Thps nor TM, significantly stimulated the expression of cytosolic PrP. Finally, we found that the levels of PrP contributed to anti-apoptosis activity of BFA-induced cancer cell death. Thus, the pathway of BFA-induced persistent ER stress may be targeted for lung and pancreatic cancer treatment.
| S-EPMC6513834 | biostudies-literature
Project description:In insulin resistant states such as type 2 diabetes, there is a high demand on the β-cell to synthesize and secrete insulin, which challenges the ability of the endoplasmic reticulum (ER) to synthesize and fold nascent proteins. This creates a state of ER stress that triggers a coordinated program referred to as the unfolded protein response (UPR) that attempts to restore ER homeostasis. We identified a role for the p85α regulatory subunit of PI3K to modulate the UPR by promoting the nuclear localization of X-box binding protein 1, a transcription factor central to the UPR. In the present study we demonstrate that reducing p85α expression in β-cells can markedly delay the onset and severity of the diabetic phenotype observed in Akita(+/-) mice, which express a mutant insulin molecule. This is due to a decrease in activation of ER stress-dependent apoptotic pathways and a preservation of β-cell mass and function. These data demonstrate that modulation of p85α can protect pancreatic β-cells from ER stress, pointing to a potentially therapeutic target in diabetic states.
| S-EPMC3903202 | biostudies-literature
Project description:While silica nanoparticles (SiNPs) have wide applications, they inevitably increase atmospheric particulate matter and human exposure to this nanomaterial. Numerous studies have focused on how to disclose SiNP toxicity and on understanding its toxic mechanisms. However, there are few studies in the literature reporting the interaction between endoplasmic reticulum (ER) stress and SiNP exposure, and the corresponding detailed mechanisms have not been clearly determined. In this study, CCK-8 and flow cytometry assays demonstrated that SiNPs gradually decreased cell viability and increased cell apoptosis in RAW 264.7 macrophage cells in dose- and time-dependent manners. Western blot analysis showed that SiNPs significantly activated ER stress by upregulating GRP78, CHOP, and ERO1? expression. Meanwhile, western blot analysis also showed that SiNPs activated the mitochondrial-mediated apoptotic signaling pathway by upregulating BAD and Caspase-3, and downregulating the BCL-2/BAX ratio. Moreover, 4-phenylbutyrate (4-PBA), an ER stress inhibitor, significantly decreased GRP78, CHOP, and ERO1? expression, and inhibited cell apoptosis in RAW 264.7 macrophage cells. Furthermore, overexpression of CHOP significantly enhanced cell apoptosis, while knockdown of CHOP significantly protected RAW 264.7 macrophage cells from apoptosis induced by SiNPs. We found that the CHOP-ERO1?-caspase-dependent apoptotic signaling pathway was activated by upregulating the downstream target protein ERO1? and caspase-dependent mitochondrial-mediated apoptotic signaling pathway by upregulating Caspase-3 and downregulating the ratio of BCL-2/BAX. In summary, ER stress participated in cell apoptosis induced by SiNPs and CHOP regulated SiNP-induced cell apoptosis, at least partly, via activation of the CHOP-ERO1?-caspase apoptotic signaling pathway in RAW 264.7 macrophage cells.
| S-EPMC6929173 | biostudies-literature
Project description:ObjectiveThe present study selected PC12 cells to construct a neuronal injury model induced by glucocorticoids (GC) in vitro, aiming to explore whether the endoplasmic reticulum stress (ERS) PKR-like endoplasmic reticulum kinase (PERK)-activating transcription factor 4 (ATF4)-C/EBP-homologous protein (CHOP) and inositol requirement 1 (IRE1)-apoptosis signal regulating kinase 1 (ASK1)-C-Jun amino-terminal kinase (JNK) signaling pathways are associated with the neuronal injury process induced by GC and provide morphological evidence.MethodsCell models with different doses and different durations of GC exposure were established. The viability of PC12 cells was detected by the CCK-8 assay, and the apoptosis rate of PC12 cells was detected by the flow cytometry assay. The expression of microtubule-associated protein 2 (Map2); glucocorticoids receptor (GR); cellular oncogene fos (C-fos); and ERS-related proteins, glucose-regulated protein 78 (GRP78), p-PERK, p-IRE1, ATF4, ASK1, JNK, and CHOP, was observed by immunofluorescence staining.ResultsThe results of immunofluorescence staining showed that PC12 cells abundantly expressed Map2 and GR. The CCK-8 assay revealed that high-concentration GC exposure significantly inhibited the cell viability of PC12 cells. The flow cytometry assay indicated that high-concentration GC exposure significantly increased the apoptosis rate of PC12 cells. Immunofluorescence staining showed that GC exposure significantly increased the expression of C-fos, GRP78, p-PERK, p-IRE1, ATF4, ASK1, JNK, and CHOP. Treatment with ERS inhibitor 4-phenylbutyric acid (4-PBA) and GR inhibitor RU38486 attenuated related damage and downregulated the expression of the abovementioned proteins.ConclusionHigh-concentration GC exposure can significantly inhibit the viability of PC12 cells and induce apoptosis. PERK-ATF4-CHOP and IRE1-ASK1-JNK pathways are involved in the above damage process.
| S-EPMC7895572 | biostudies-literature