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Joy Ogbechi, Belinda S Hall, Thomas Sbarrato, Jack Taunton, Anne E Willis, Ronald C Wek, Rachel E Simmonds
Mycolactone is the exotoxin virulence factor of Mycobacterium ulcerans that causes the neglected tropical disease Buruli ulcer. We recently showed it to be a broad spectrum inhibitor of Sec61-dependent co-translational translocation of proteins into the endoplasmic reticulum (ER). An outstanding question is the molecular pathway linking this to its known cytotoxicity. We have now used translational profiling to better understand the reprogramming that occurs in cells exposed to mycolactone. Gene ontology identified enrichment in genes involved in cellular response to stress, and apoptosis signalling among those showing enhanced translation...
March 14, 2018: Cell Death & Disease
Antonello Storniolo, Vincenzo Alfano, Sabino Carbotta, Elisabetta Ferretti, Livia Di Renzo
Sensors of endoplasmic reticulum (ER) stress function in a co-ordinated manner. In the present study we investigated the relationship between IRE1α and PERK pathways and survival of ER stressed U937 cells and BC3 cells. To this end, we investigated the effects of a subcytotoxic concentration of Tunicamycin in IRE1α-proficient and in IRE1α-deficient cells, by pharmacological inhibition with 4μ8 C or down-regulation by specific siRNA. We show that either type of IRE1α deficiency affects eIF2α expression and causes cell death increase...
December 2018: Cell Death Discovery
Prashanth K B Nagesh, Elham Hatami, Pallabita Chowdhury, Vivek K Kashyap, Sheema Khan, Bilal B Hafeez, Subhash C Chauhan, Meena Jaggi, Murali M Yallapu
Endoplasmic reticulum (ER) stress is an intriguing target with significant clinical importance in chemotherapy. Interference with ER functions can lead to the accumulation of unfolded proteins, as detected by transmembrane sensors that instigate the unfolded protein response (UPR). Therefore, controlling induced UPR via ER stress with natural compounds could be a novel therapeutic strategy for the management of prostate cancer. Tannic acid (a naturally occurring polyphenol) was used to examine the ER stress mediated UPR pathway in prostate cancer cells...
March 7, 2018: Cancers
Haibo Ni, Qin Rui, Yitian Xu, Jun Zhu, Fan Gao, Baoqi Dang, Di Li, Rong Gao, Gang Chen
Receptor for activated protein kinase C 1 (RACK1) is a multifaceted scaffolding protein known to be involved in the regulation of signaling events required for neuronal protection. In the present study, we investigated the role of RACK1 in secondary brain injury in a rat traumatic brain injury (TBI) model. A weight-drop TBI model was established in Sprague Dawley rats, and RACK1 in vivo knockdown and overexpression were performed 24 h before TBI insult. The IRE1 inhibitor 3,5-dibromosalicylaldehyde (DBSA) was administered by intracerebroventricular injection 1 h after TBI insult...
March 5, 2018: Experimental Neurology
Gemma Sangüesa, José Carlos Montañés, Miguel Baena, Rosa María Sánchez, Núria Roglans, Marta Alegret, Juan Carlos Laguna
PURPOSE: Sugar-sweetened beverage intake is a risk factor for insulin resistance, dyslipidemia, fatty liver, and steatohepatitis (NASH). Sub-chronic supplementation of liquid fructose, but not glucose, in female rats increases liver and plasma triglycerides without inflammation. We hypothesized that chronic supplementation of fructose would cause NASH and liver insulin resistance. METHODS: We supplemented female Sprague-Dawley rats with water or either fructose or glucose 10% w/v solutions under isocaloric conditions for 7 months...
March 7, 2018: European Journal of Nutrition
Ganesh M Nawkar, Eun Seon Lee, Rahul M Shelake, Joung Hun Park, Seoung Woo Ryu, Chang Ho Kang, Sang Yeol Lee
Maintenance of homeostasis of the endoplasmic reticulum (ER) ensures the balance between loading of nascent proteins and their secretion. Certain developmental conditions or environmental stressors affect protein folding causing ER stress. The resultant ER stress is mitigated by upregulating a set of stress-responsive genes in the nucleus modulating the mechanism of the unfolded protein response (UPR). In plants, the UPR is mediated by two major pathways; by the proteolytic processing of bZIP17/28 and by the IRE1-mediated splicing of bZIP60 mRNA...
2018: Frontiers in Plant Science
Chih-Hang Anthony Tang, Shiun Chang, Adrienne W Paton, James C Paton, Dmitry I Gabrilovich, Hidde L Ploegh, Juan R Del Valle, Chih-Chi Andrew Hu
To relieve endoplasmic reticulum (ER) stress, IRE1 splices XBP1 messenger RNA (mRNA) or engages regulated IRE1-dependent decay (RIDD) of other mRNAs. Upon XBP1 deficiency, IRE1 switches to perform RIDD. We examined IRE1 in XBP1-deficient B cells and discovered that IRE1 undergoes phosphorylation at S729. We generated an anti-phospho-S729 antibody to investigate such phosphorylation. Compared with pharmacological ER stress inducers or Toll-like receptor ligands, the bacterial subtilase cytotoxin has an unusual capability in causing rapid and strong phosphorylation at S729 and triggering B cells to express spliced XBP1...
March 6, 2018: Journal of Cell Biology
Yanfang Wu, Xia Li, Junying Jia, Yanpeng Zhang, Jing Li, Zhengmao Zhu, Huaqing Wang, Jie Tang, Junjie Hu
The accumulation of misfolded proteins in the endoplasmic reticulum (ER) causes ER stress and triggers the unfolded protein response (UPR). Failure to resolve ER stress leads to apoptotic cell death via a yet unclear mechanism. Here, we show that RNF183, a membrane-spanning RING finger protein, localizes to the ER and exhibits classic E3 ligase activities. Sustained ER stress induced by different treatments increases RNF183 protein levels posttranscriptionally in an IRE1α-dependent manner. Activated IRE1 reduces the level of miR-7, which increases the stability of RNF183 transcripts...
March 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
Yuichi Tsuchiya, Michiko Saito, Hiroshi Kadokura, Jun-Ichi Miyazaki, Fumi Tashiro, Yusuke Imagawa, Takao Iwawaki, Kenji Kohno
In mammalian pancreatic β cells, the IRE1α-XBP1 pathway is constitutively and highly activated under physiological conditions. To elucidate the precise role of this pathway, we constructed β cell-specific Ire1α conditional knockout (CKO) mice and established insulinoma cell lines in which Ire1α was deleted using the Cre-loxP system. Ire1α CKO mice showed the typical diabetic phenotype including impaired glycemic control and defects in insulin biosynthesis postnatally at 4-20 weeks. Ire1α deletion in pancreatic β cells in mice and insulinoma cells resulted in decreased insulin secretion, decreased insulin and proinsulin contents in cells, and decreased oxidative folding of proinsulin along with decreased expression of five protein disulfide isomerases (PDIs): PDI, PDIR, P5, ERp44, and ERp46...
March 5, 2018: Journal of Cell Biology
Na Zhao, Jin Cao, Longyong Xu, Qianzi Tang, Lacey E Dobrolecki, Xiangdong Lv, Manisha Talukdar, Yang Lu, Xiaoran Wang, Dorothy Z Hu, Qing Shi, Yu Xiang, Yunfei Wang, Xia Liu, Wen Bu, Yi Jiang, Mingzhou Li, Yingyun Gong, Zheng Sun, Haoqiang Ying, Bo Yuan, Xia Lin, Xin-Hua Feng, Sean M Hartig, Feng Li, Haifa Shen, Yiwen Chen, Leng Han, Qingping Zeng, John B Patterson, Benny Abraham Kaipparettu, Nagireddy Putluri, Frank Sicheri, Jeffrey M Rosen, Michael T Lewis, Xi Chen
The unfolded protein response (UPR) is a cellular homeostatic mechanism that is activated in many human cancers and plays pivotal roles in tumor progression and therapy resistance. However, the molecular mechanisms for UPR activation and regulation in cancer cells remain elusive. Here, we show that oncogenic MYC regulates the inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1 (XBP1) branch of the UPR in breast cancer via multiple mechanisms. We found that MYC directly controls IRE1 transcription by binding to its promoter and enhancer...
February 26, 2018: Journal of Clinical Investigation
Daniel Hughes, Giovanna R Mallucci
The unfolded protein response (UPR) is a highly conserved protein quality control mechanism, activated in response to Endoplasmic Reticulum (ER) stress. Signaling is mediated through three branches, PERK, IRE1 and ATF6, respectively, that together provide a coordinated response that contributes to overcoming disrupted proteostasis. PERK branch activation predominantly causes a rapid reduction in global rates of translation, whilst the IRE1 and ATF6 branch signaling induce a transcriptional response resulting in expression of chaperones and components of the protein degradation machinery...
February 24, 2018: FEBS Journal
Man Liu, Guangbin Shi, Anyu Zhou, Cassady E Rupert, Kareen L K Coulombe, Samuel C Dudley
RATIONALE: Heart failure is characterized by electrical remodeling that contributes to arrhythmic risk. The unfolded protein response (UPR) is active in heart failure and can decrease protein levels by increasing mRNA decay, accelerating protein degradation, and inhibiting protein translation. OBJECTIVE: Therefore, we investigated whether the UPR downregulated cardiac ion channels that may contribute to arrhythmogenic electrical remodeling. METHODS: Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to study cardiac ion channels...
February 21, 2018: Journal of Molecular and Cellular Cardiology
Stephanie R Harrison, Thomas Scambler, Lylia Oubussad, Chi Wong, Miriam Wittmann, Michael F McDermott, Sinisa Savic
Tumor necrosis factor (TNF)-receptor-associated periodic fever syndrome (TRAPS) is a rare monogenic autoinflammatory disorder characterized by mutations in the TNFRSF1A gene, causing TNF-receptor 1 (TNFR1) misfolding, increased cellular stress, activation of the unfolded protein response (UPR), and hyperresponsiveness to lipopolysaccharide (LPS). Both microRNA (miR)-146a and miR-155 provide negative feedback for LPS-toll-like receptor 2/4 signaling and cytokine production, through regulation of nuclear factor kappa B (NF-κB)...
2018: Frontiers in Immunology
Timothy J Bergmann, Ilaria Fregno, Fiorenza Fumagalli, Andrea Rinaldi, Francesco Bertoni, Paul J Boersema, Paola Picotti, Maurizio Molinari
The stress sensors ATF6, IRE1 and PERK monitor deviations from homeostatic conditions in the endoplasmic reticulum (ER), a protein biogenesis compartment of eukaryotic cells. Their activation elicits unfolded protein responses (UPR) to re-establish proteostasis. UPR have been extensively investigated in cells exposed to chemicals that activate ER stress sensors by perturbing calcium, N-glycans or redox homeostasis. Cell responses to variations in luminal load with unfolded proteins are, in contrast, poorly characterized...
February 16, 2018: Journal of Biological Chemistry
Chi Thanh Mai, Quynh Giang Le, Yuki Ishiwata-Kimata, Hiroshi Takagi, Kenji Kohno, Yukio Kimata
Accumulation of unfolded secretory proteins in the endoplasmic reticulum (ER), namely ER stress, is hazardous to eukaryotic cells and promotes the unfolded protein response (UPR). Ire1 is an ER-located transmembrane protein that senses ER stress and triggers the UPR. According to previous in vitro experiments, 4-phenylbutyrate (4-PBA) works as a chemical molecular chaperone. Since 4-PBA attenuates the UPR in mammalian tissue cultures, this chemical may have clinical potential for restoring ER-stressing conditions...
February 14, 2018: FEMS Yeast Research
Zhifen Yang, Jing Zhang, Dadi Jiang, Purvesh Khatri, David E Solow-Cordero, Diego A S Toesca, Constantinos Koumenis, Nicholas C Denko, Amato J Giaccia, Quynh-Thu Le, Albert C Koong
Activation of the unfolded protein response (UPR) signaling pathways is linked to multiple human diseases including cancer. The inositol-requiring kinase 1 (IRE1)-X-box binding protein 1 (XBP1) pathway is the most evolutionarily conserved of the three major signaling branches of the UPR. Here, we performed a genome-wide siRNA screen to obtain a systematic assessment of genes integrated in the IRE1-XBP1 axis. We monitored the expression of an XBP1-luciferase chimeric protein in which luciferase was fused in-frame with the spliced (active) form of XBP1...
February 9, 2018: Molecular Cancer Research: MCR
Amanda Crider, Tyler Nelson, Talisha Davis, Kiley Fagan, Kumar Vaibhav, Matthew Luo, Sunay Kamalasanan, Alvin V Terry, Anilkumar Pillai
Impaired social interaction is a key feature of several major psychiatric disorders including depression, autism, and schizophrenia. While, anatomically, the prefrontal cortex (PFC) is known as a key regulator of social behavior, little is known about the cellular mechanisms that underlie impairments of social interaction. One etiological mechanism implicated in the pathophysiology of the aforementioned psychiatric disorders is cellular stress and consequent adaptive responses in the endoplasmic reticulum (ER) that can result from a variety of environmental and physical factors...
February 12, 2018: Molecular Neurobiology
Huaqing Cui, Mengsheng Deng, Yonglan Zhang, Fei Yin, Jianhui Liu
Altered proteostasis induced by amyloid peptide aggregation and hyperphosphorylation of tau protein, is a prominent feature of Alzheimer's disease, which highlights the occurrence of endoplasmic reticulum stress and triggers the activation of the unfolded protein response (UPR), a signaling pathway that enforces adaptive programs to sustain proteostasis. In this study, we investigated the role of geniposide in the activation of UPR induced by high glucose in primary cortical neurons. We found that high glucose induced a significant activation of UPR, and geniposide enhanced the effect of high glucose on the phosphorylation of IRE1α, the most conserved UPR signaling branch...
February 9, 2018: Neurochemical Research
Mahendra Pal Singh, Anil Kumar Chauhan, Sun Chul Kang
The present study assessed the possible therapeutic potential of a natural flavonoid morin hydrate (MH), against cisplatin (CP) induced toxicity in HEK-293 cells and mice kidney. Herein, we observed that exposure of HEK-293 cells to CP (20 μM, 24 h) reduced the cell viability, and increased the intracellular ROS generation, nuclear DNA damage, Ca++ release, and accumulation of acidic vacuoles. Concomitantly, acute exposure of CP (30 mg/kg, 72 h) to male ICR mice induced histopathological changes in kidney tissue, and alterations in serum creatinine and blood urea nitrogen (BUN) levels...
February 1, 2018: International Immunopharmacology
Yun Zhang, Saiyu Li, Juanjuan Li, Liwen Han, Qiuxia He, Rongchun Wang, Ximin Wang, Kechun Liu
The aims of this study were to investigate the mechanism underlying the developmental toxicity of fine particulate matter (PM2.5) and provide a more thorough understanding of the toxicity of PM2.5 in an ecological environment. Zebrafish embryos at 4 h post-fertilization were exposed to PM2.5 at doses of 200, 300, 400, 500, 600 and 800 μg/mL for 120 h. The mortality, hatching rate, morphology score, body length, locomotor capacity, histological changes, antioxidant defense system, leukocyte migration, inflammation-related gene mRNA expression, endoplasmic reticulum stress (ERS) and autophagy were evaluated to study PM2...
January 25, 2018: Chemosphere
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