scholarly journals Increased Post-Hypoxic Oxidative Stress and Activation of the PERK Branch of the UPR in Trap1-Deficient Drosophila melanogaster Is Abrogated by Metformin

2021 ◽  
Vol 22 (21) ◽  
pp. 11586
Author(s):  
Alma Kokott-Vuong ◽  
Jennifer Jung ◽  
Aaron T. Fehr ◽  
Nele Kirschfink ◽  
Rozina Noristani ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Er Stress ◽  
Ros Production ◽  
Loss Of Function ◽  
Protein Kinase R ◽  
Receptor Associated Protein ◽  
Negative Geotaxis ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Hypoxia is known to impair mitochondrial and endoplasmic reticulum (ER) homeostasis. Post-hypoxic perturbations of the ER proteostasis result in the accumulation of misfolded/unfolded proteins leading to the activation of the Unfolded Protein Response (UPR). Mitochondrial chaperone TNF receptor-associated protein 1 (TRAP1) is reported to preserve mitochondrial membrane potential and to impede reactive oxygen species (ROS) production thereby protecting cells from ER stress as well as oxidative stress. The first-line antidiabetic drug Metformin has been attributed a neuroprotective role after hypoxia. Interestingly, Metformin has been reported to rescue mitochondrial deficits in fibroblasts derived from a patient carrying a homozygous TRAP1 loss-of-function mutation. We sought to investigate a putative link between Metformin, TRAP1, and the UPR after hypoxia. We assessed post-hypoxic/reperfusion longevity, mortality, negative geotaxis, ROS production, metabolic activity, gene expression of antioxidant proteins, and activation of the UPR in Trap1-deficient flies. Following hypoxia, Trap1 deficiency caused higher mortality and greater impairments in negative geotaxis compared to controls. Similarly, post-hypoxic production of ROS and UPR activation was significantly higher in Trap1-deficient compared to control flies. Metformin counteracted the deleterious effects of hypoxia in Trap1-deficient flies but had no protective effect in wild-type flies. We provide evidence that TRAP1 is crucially involved in the post-hypoxic regulation of mitochondrial/ER stress and the activation of the UPR. Metformin appears to rescue Trap1-deficiency after hypoxia mitigating ROS production and downregulating the pro-apoptotic PERK (protein kinase R-like ER kinase) arm of the UPR.

scholarly journals Transcription factor ATF4 directs basal and stress-induced gene expression in the unfolded protein response and cholesterol metabolism in the liver

2016 ◽  
Vol 27 (9) ◽  
pp. 1536-1551 ◽  
Author(s):  
Michael E. Fusakio ◽  
Jeffrey A. Willy ◽  
Yongping Wang ◽  
Emily T. Mirek ◽  
Rana J. T. Al Baghdadi ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Transcription Factor ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Cholesterol Metabolism ◽  
Unfolded Protein ◽  
Expression Of Genes ◽  
The Unfolded Protein Response ◽  
Protein Response

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.

scholarly journals Activation of the IRE1α Arm, but not the PERK Arm, of the Unfolded Protein Response Contributes to Fumonisin B1-Induced Hepatotoxicity

Toxins ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 55 ◽  
Author(s):  
Xiaoyi Liu ◽  
Enxiang Zhang ◽  
Shutao Yin ◽  
Chong Zhao ◽  
Lihong Fan ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Liver Toxicity ◽  
Fumonisin B1 ◽  
Critical Event ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Previous studies by us or others have shown that endoplasmic reticulum (ER) stress was activated by fumonisin 1 (FB1) exposure, which is considered to be a critical event in the FB1-induced toxic effect. However, the detailed mechanisms underlying FB1-induced ER stress-mediated liver toxicity remain elusive. The objectives of the present study were designed to address the following issues: (1) the contribution of each arm of the unfolded protein response (UPR); (2) the downstream targets of ER stress that mediated FB1-induced liver toxicity; and (3) the relationship between ER stress and oxidative stress triggered by FB1. We also investigated whether the inhibition of ER stress by its inhibitor could offer protection against FB1-induced hepatotoxicity in vivo, which has not been critically addressed previously. The results showed that the activation of the IRE1α axis, but not of the PERK axis, of UPR contributed to FB1-induced ER stress-mediated hepatocyte toxicity; the activation of the Bax/Bak-mediated mitochondrial pathway lay downstream of IRE1α to trigger mitochondrial-dependent apoptosis in response to FB1; FB1-induced oxidative stress and ER stress augmented each other through a positive feedback mechanism; tauroursodeoxycholic acid (TUDCA)-mediated ER stress inactivation is an effective approach to counteract FB1-induced hepatotoxicity in vivo. The data of the present study allow us to better understand the mechanisms of FB1-induced hepatotoxicity.

No evidence of the unfolded protein response in the placenta of two rodent models of preeclampsia and intrauterine growth restriction

2021 ◽  
Author(s):  
Barbara Denkl ◽  
Nada Cordasic ◽  
Hanna Huebner ◽  
Carlos Menendez-Castro ◽  
Marius Schmidt ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Animal Models ◽  
Er Stress ◽  
Western Blotting ◽  
Intrauterine Growth Restriction ◽  
Rodent Models ◽  
Intrauterine Growth ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

Abstract Introduction In humans, intrauterine growth restriction (IUGR) and preeclampsia (PE) are associated with induction of the unfolded protein response (UPR) and increased placental endoplasmic reticulum (ER) stress. Especially in PE, oxidative stress occurs relative to the severity of maternal vascular underperfusion (MVU) of the placental bed. On the premise that understanding the mechanisms of placental dysfunction could lead to targeted therapeutic options for human IUGR and PE, we investigated the roles of the placental UPR and oxidative stress in two rodent models of these human gestational pathologies. Methods We employed a rat IUGR model of gestational maternal protein restriction, as well as an endothelial nitric oxide synthase knockout mouse model (eNOS−/−) of PE/IUGR. Placental expression of UPR members was analyzed via qRT-PCR (Grp78, Calnexin, Perk, Chop, Atf6, Ern1), immunohistochemistry and Western blotting (Calnexin, ATF6, GRP78, CHOP, phospho-eIF2α, phospho-IRE1). Oxidative stress was determined via Western blotting (3-nitrotyrosine, 4-hydroxy-2-nonenal). Results Both animal models showed a significant reduction of fetal and placental weight. These effects did not induce placental UPR. In contrast to human data, results from our rodent models suggest retention of placental plasticity in the setting of ER stress under an adverse gestational environment. Oxidative stress was significantly increased only in female IUGR rat placentas, suggesting a sexually dimorphic response to maternal malnutrition. Discussion Our study advances understanding of the involvement of the placental UPR in IUGR and PE. Moreover, it emphasizes the appropriate choice of animal models researching various aspects of these pregnancy complications.

scholarly journals Effect of the Unfolded Protein Response and Oxidative Stress on Mutagenesis of CSF3R a Model of Evolution of Severe Congenital Neutropenia to Myelodysplastic Syndrome/Acute Myeloid Leukemia

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 3752-3752
Author(s):  
Adya Sapra ◽  
Roman Jaksik ◽  
Sara Biesiadny ◽  
Hrishikesh M Mehta ◽  
Marek Kimmel ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Acute Myeloid Leukemia ◽  
Er Stress ◽  
Myeloid Leukemia ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Acute Myeloid

Background. Severe congenital neutropenia (SCN) is an inherited bone marrow failure syndrome that can transform to myelodysplastic syndrome/acute myeloid leukemia (MDS/AML). The most common recurrent mutation that causes SCN involve neutrophil elastase (ELANE). Mutations in ELANE result in the unfolded protein response stress. The treatment of choice for SCN is the chronic administration of high-dose granulocyte-colony stimulating factor (G-CSF), which elevates the neutrophil count, helps resolve pre-existing infections, diminishes the number of new infections, and significantly improves the survival and quality of life. G-CSF treatment also leads to enhanced oxidative stress. Long-term survival with G-CSF is frequently associated with development of MDS/AML. Of note, approximately 70% of SCN patients with MDS/AML acquire nonsense mutations in the region of CSF3R that encodes the cytoplasmic domain. These somatic CSF3R mutations are characterized by a truncation variant found in the cytoplasmic domain of the CSF3R and are associated with a hyper-proliferative/impaired differentiative phenotype that might contribute to the MDS/AML transformation. We hypothesize that the terminal exon of CSF3R constitutes a hotspot vulnerable to mutations resulting from excessive oxidative stress or endoplasmic reticulum (ER) stress. Results. Murine factor-dependent Ba/F3 cells were used to measure the effect of induced oxidative or ER stress on the mutation rate involving the hypothesized hotspot of the exogenous human CSF3R, the corresponding region in the endogenous Csf3r, and Runx1 (a transcription factor involved in leukemogenesis). Ba/F3 cells transduced with the cDNA for the hypothesized hotspot of CSF3R (partial C-terminal) fused in-frame with m-NeonGreen, a yellow-green fluorescent protein, were subjected to stress-inducing treatment for 30 days (~51 doubling times). The amplicon-based targeted deep-sequencing data for days 15 and 30 samples showed increased mutagenesis of the coding nucleotide sequences for CSF3R, Csf3r, and Runx1. There was no correlation between the stress-inducing chemical treatments and overall level of mutagenesis in Ba/F3 cells. Interestingly, the GC-rich partial CSF3R region was less mutated as compared to the mNeonGreen region, having much lower GC content. However, analysis of our data, including the site-frequency spectra, indicated effects that may be due to clonal selection, specifically at the Csf3r gene. Conclusion. Our data suggested that oxidative or ER stress induction did not promote genomic instability affecting the 3' exonic end of CSF3R, the endogenous Csf3R, and the endogenous Runx1 in Ba/F3 cells that could account for these targets being mutational hotspots. We conclude that other mechanisms, such as stochastic events, result in mutations of CSF3R drive the evolution of SCN to MDS/AML. Disclosures No relevant conflicts of interest to declare.

scholarly journals Loss of slc39a14 causes simultaneous manganese deficiency and hypersensitivity in zebrafish

2020 ◽  
Author(s):  
Karin Tuschl ◽  
Richard J White ◽  
Leonardo E Valdivia ◽  
Stephanie Niklaus ◽  
Isaac H Bianco ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Differentially Expressed Genes ◽  
Differentially Expressed ◽  
Manganese Deficiency ◽  
Loss Of Function ◽  
Unfolded Protein ◽  
Manganese Neurotoxicity ◽  
Manganese Uptake ◽  
The Unfolded Protein Response ◽  
Protein Response

AbstractMutations in SLC39A14, a manganese uptake transporter, lead to a neurodegenerative disorder characterised by accumulation of manganese in the brain and rapidly progressive dystonia-parkinsonism (Hypermanganesemia with Dystonia 2, HMNDYT2). Similar to the human phenotype, zebrafish slc39a14U801-/- mutants show prominent brain manganese accumulation and abnormal locomotor behaviour. In order to identify novel potential targets of manganese neurotoxicity, we performed transcriptome analysis of individual homozygous mutant and sibling slc39a14U801 zebrafish at five days post fertilisation unexposed and exposed to MnCl2. Anatomical gene enrichment analysis confirmed that differentially expressed genes map to the central nervous system and eye. Biological interpretation of differentially expressed genes suggests that calcium dyshomeostasis, activation of the unfolded protein response, oxidative stress, mitochondrial dysfunction, lysosomal disruption, apoptosis and autophagy, and interference with proteostasis are key events in manganese neurotoxicity. Differential expression of visual phototransduction genes also predicted visual dysfunction in mutant larvae which was confirmed by the absence of visual background adaptation and a diminished optokinetic reflex. Surprisingly, we found a group of differentially expressed genes in mutant larvae that normalised upon MnCl2 treatment suggesting that, in addition to neurotoxicity, manganese deficiency is present either subcellularly or in specific cells or tissues. This may have important implications for treatment as manganese chelation may aggravate neurological symptoms. Our analyses show that slc39a14U801-/- mutant zebrafish present a powerful model to study the cellular and molecular mechanisms underlying disrupted manganese homeostasis.Significance statementManganese neurotoxicity leading to progressive dystonia-parkinsonism is a characteristic feature of Hypermanganesemia with dystonia 2 (HMNDYT2) caused by mutations in SLC39A14, a manganese uptake transporter. Transcriptional profiling in slc39a14U801 loss-of-function zebrafish suggests that, in addition to manganese neurotoxicity, subcellular or cell type specific manganese deficiency contributes to the disease phenotype. Both manganese overload and deficiency appear to be associated with Ca2+ dyshomeostasis. We further demonstrate that activation of the unfolded protein response, oxidative stress, mitochondrial dysfunction, apoptosis and autophagy, and disrupted proteostasis are likely downstream events in manganese neurotoxicity. Our study shows that the zebrafish slc39a14U801 loss-of-function mutant is a powerful model to elucidate the mechanistic basis of diseases affected by manganese dyshomeostasis.

scholarly journals Effectors Targeting the Unfolded Protein Response during Intracellular Bacterial Infection

2021 ◽  
Vol 9 (4) ◽  
pp. 705
Author(s):  
Manal H. Alshareef ◽  
Elizabeth L. Hartland ◽  
Kathleen McCaffrey
Keyword(s):  
Bacterial Infection ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Host Defense ◽  
Effector Proteins ◽  
Dual Nature ◽  
Unfolded Protein ◽  
Bacterial Replication ◽  
The Unfolded Protein Response ◽  
Protein Response

The unfolded protein response (UPR) is a homeostatic response to endoplasmic reticulum (ER) stress within eukaryotic cells. The UPR initiates transcriptional and post-transcriptional programs to resolve ER stress; or, if ER stress is severe or prolonged, initiates apoptosis. ER stress is a common feature of bacterial infection although the role of the UPR in host defense is only beginning to be understood. While the UPR is important for host defense against pore-forming toxins produced by some bacteria, other bacterial effector proteins hijack the UPR through the activity of translocated effector proteins that facilitate intracellular survival and proliferation. UPR-mediated apoptosis can limit bacterial replication but also often contributes to tissue damage and disease. Here, we discuss the dual nature of the UPR during infection and the implications of UPR activation or inhibition for inflammation and immunity as illustrated by different bacterial pathogens.

scholarly journals Confounding Roles of ER Stress and the Unfolded Protein Response in Skeletal Muscle Atrophy

2021 ◽  
Vol 22 (5) ◽  
pp. 2567
Author(s):  
Yann S. Gallot ◽  
Kyle R. Bohnert
Keyword(s):  
Skeletal Muscle ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Smooth Endoplasmic Reticulum ◽  
Skeletal Muscle Atrophy ◽  
Unfolded Protein ◽  
The Individual ◽  
The Unfolded Protein Response ◽  
Protein Response

Skeletal muscle is an essential organ, responsible for many physiological functions such as breathing, locomotion, postural maintenance, thermoregulation, and metabolism. Interestingly, skeletal muscle is a highly plastic tissue, capable of adapting to anabolic and catabolic stimuli. Skeletal muscle contains a specialized smooth endoplasmic reticulum (ER), known as the sarcoplasmic reticulum, composed of an extensive network of tubules. In addition to the role of folding and trafficking proteins within the cell, this specialized organelle is responsible for the regulated release of calcium ions (Ca2+) into the cytoplasm to trigger a muscle contraction. Under various stimuli, such as exercise, hypoxia, imbalances in calcium levels, ER homeostasis is disturbed and the amount of misfolded and/or unfolded proteins accumulates in the ER. This accumulation of misfolded/unfolded protein causes ER stress and leads to the activation of the unfolded protein response (UPR). Interestingly, the role of the UPR in skeletal muscle has only just begun to be elucidated. Accumulating evidence suggests that ER stress and UPR markers are drastically induced in various catabolic stimuli including cachexia, denervation, nutrient deprivation, aging, and disease. Evidence indicates some of these molecules appear to be aiding the skeletal muscle in regaining homeostasis whereas others demonstrate the ability to drive the atrophy. Continued investigations into the individual molecules of this complex pathway are necessary to fully understand the mechanisms.

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