Subcellular Localization of Thioredoxin/Thioredoxin Reductase System—A Missing Link in Endoplasmic Reticulum Redox Balance
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ABSTRACT:
SUBMITTER: Veszelyi K
PROVIDER: S-EPMC11204020 | biostudies-literature | 2024 Jun
REPOSITORIES: biostudies-literature
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Project description:Many metabolic diseases disrupt endoplasmic reticulum (ER) homeostasis, but little is known about how metabolic activity is communicated to the ER. Here, we show in hepatocytes and other metabolically active cells that decreasing the availability of substrate for the tricarboxylic acid (TCA) cycle diminished NADPH production, elevated glutathione oxidation, led to altered oxidative maturation of ER client proteins, and attenuated ER stress. This attenuation was prevented when glutathione oxidation was disfavored. ER stress was also alleviated by inhibiting either TCA-dependent NADPH production or Glutathione Reductase. Conversely, stimulating TCA activity increased NADPH production, glutathione reduction, and ER stress. Validating these findings, deletion of the Mitochondrial Pyruvate Carrier-which is known to decrease TCA cycle activity and protect the liver from steatohepatitis-also diminished NADPH, elevated glutathione oxidation, and alleviated ER stress. Together, our results demonstrate a novel pathway by which mitochondrial metabolic activity is communicated to the ER through the relay of redox metabolites.
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Project description:Calcium ion (Ca2+) is an important second messenger that regulates numerous cellular functions. Intracellular Ca2+ concentration ([Ca2+]i) is strictly controlled by Ca2+ channels and pumps on the endoplasmic reticulum (ER) and plasma membranes. The ER calcium pump, sarco/endoplasmic reticulum calcium ATPase (SERCA), imports Ca2+ from the cytosol into the ER in an ATPase activity-dependent manner. The activity of SERCA2b, the ubiquitous isoform of SERCA, is negatively regulated by disulfide bond formation between two luminal cysteines. Here, we show that ERdj5, a mammalian ER disulfide reductase, which we reported to be involved in the ER-associated degradation of misfolded proteins, activates the pump function of SERCA2b by reducing its luminal disulfide bond. Notably, ERdj5 activated SERCA2b at a lower ER luminal [Ca2+] ([Ca2+]ER), whereas a higher [Ca2+]ER induced ERdj5 to form oligomers that were no longer able to interact with the pump, suggesting [Ca2+]ER-dependent regulation. Binding Ig protein, an ER-resident molecular chaperone, exerted a regulatory role in the oligomerization by binding to the J domain of ERdj5. These results identify ERdj5 as one of the master regulators of ER calcium homeostasis and thus shed light on the importance of cross talk among redox, Ca2+, and protein homeostasis in the ER.
| S-EPMC5068290 | biostudies-literature
Project description:Correct localization and transmembrane topology are crucial for the proteins residing and functioning in the endoplasmic reticulum (ER). We have developed a rapid and convenient assay, based on the redox-sensitive luciferase from Gaussia princeps (Gluc) and green fluorescence protein (GFP), to determine the localization or topology of ER proteins. Using the tandem Gluc-GFP reporter fused to different positions of a target protein, we successfully characterized the topologies of two ER transmembrane proteins Herp and HRD1 that are involved in the ER quality control system. This assay method may also be applicable to the proteins in secretory pathway, plasma membrane, and other compartments of cells.
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Project description:Reactive oxygen species (ROS) have been implicated as mediators of pancreatic β-cell damage. While β-cells are thought to be vulnerable to oxidative damage, we have shown, using inhibitors and acute depletions, that thioredoxin reductase, thioredoxin, and peroxiredoxins are the primary mediators of antioxidant defense in β-cells. However, the role of this antioxidant cycle in maintaining redox homeostasis and β-cell survival in vivo remains unclear. Here, we generated mice with a β-cell specific knockout of thioredoxin reductase 1 (Txnrd1.fl/fl; Ins1.Cre/+, βKO). Despite blunted glucose-stimulated insulin secretion, knockout mice maintain normal whole body glucose homeostasis. Unlike pancreatic islets with acute Txnrd1 inhibition, βKO islets do not demonstrate increased sensitivity to continuous ROS. RNA-sequencing analysis revealed that Txnrd1-deficient β-cells have increased expression of Nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated genes, and altered expression of genes involved in heme and glutathione metabolism, suggesting an adaptive response. Txnrd1-deficient β-cells also have decreased expression of factors controlling β-cell function and identity which may explain the mild functional impairment. Together, these results suggest that Txnrd1-knockout β-cells compensate for loss of this essential antioxidant pathway by increasing expression of Nrf2-regulated antioxidant genes, allowing for protection from excess ROS at the expense of normal β-cell function and identity.
2022-07-05 | GSE200965 | GEO
Project description:BackgroundEndoplasmic reticulum (ER) stress plays an important role in the occurrence and development of various liver diseases. However, there are no effective prevention and treatment strategies. We aimed to determine the role of heat shock factor 2 binding protein (HSF2BP) in ER stress.MethodsHSF2BP expression in mice and cultured hepatocytes was measured during ER stress induced by tunicamycin, and its importance in ER stress was evaluated in hepatocyte-specific HSF2BP transgenic (TG) and knockout (KO) mice. The effects and mechanisms of HSF2BP on ER stress were further probed in hepatic ischemia-reperfusion (I/R) injury.ResultsHSF2BP expression was significantly upregulated during tunicamycin-induced ER stress in mice and cultured hepatocytes. Liver injury and ER stress were reduced in HSF2BP overexpressing mice after treating with tunicamycin, but were aggravated in HSF2BP knockout mice compared to the controls. In hepatic I/R injury, HSF2BP expression was significantly upregulated, and HSF2BP overexpressing mice had reduced liver injury and inflammation. These improvements were associated with ER stress inhibition. However, these results were reversed in hepatocyte-specific HSF2BP knockout mice. HSF2BP overexpression increased cytoplasmic CDC73 levels and inhibited the JNK signaling pathway. CDC73 knockdown using siRNA eliminated the protection exerted by HSF2BP overexpression in hypoxia/reoxygenation (H/R)-induced ER stress in hepatocytes.ConclusionHSF2BP is a previously uncharacterized regulatory factor in ER stress-likely acts by regulating CDC73 subcellular localization. The feasibility of HSF2BP-targeted treatment in ER stress-related liver disease deserves future research.
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Project description:Ribonucleotide reductase (RNR), the rate-limiting enzyme in DNA synthesis, catalyzes reduction of the different ribonucleotides to their corresponding deoxyribonucleotides. The crucial role of RNR in DNA synthesis has made it an important target for the development of antiviral and anticancer drugs. Taking account of the recent developments in this field of research, this review focuses on the role of thioredoxin and glutaredoxin systems in the redox reactions of the RNR catalysis.
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Project description:The role of general splicing in endoplasmic reticulum (ER)-proteostasis remains poorly understood. Here, we identify SNRPB, a component of the spliceosome, as a novel regulator of export from the ER. Mechanistically, SNRPB regulates the splicing of components of the ER export machinery, including Sec16A, a regulator of ER exit sites. Loss of function of SNRPB is causally linked to cerebro-costo-mandibular syndrome (CCMS), a genetic disease characterized by bone defects. We show that heterozygous deletion of SNRPB in mice resulted in intracellular accumulation of type-1 collagen as well as bone defects reminiscent of CCMS. Silencing SNRPB inhibited osteogenesis in vitro, which could be rescued by overexpression of Sec16A. This indicates that the role of SNRPB in osteogenesis is linked to its effects on ER export. Finally, we show that SNRPB is a target for the unfolded protein response (UPR), which supports a mechanistic link between the spliceosome and ER-proteostasis. Our work highlights SNRPB as a novel node in the proteostasis network, shedding light on CCMS pathophysiology.
2024-10-15 | GSE254122 | GEO
Project description:The involvement the thioredoxin system in radiation resistance was investigated in human lung cancer cells by a combination of ionizing radiation and specific thioredoxin reductase-inhibition by a phosphine gold compound. Gene expression profiles (Human Gene 1.0 ST) of lung cancer cells subjected to ionizing radiation and/or inhibition of thioredoxin reductase were studied. Data analyses were performed using the Affymetrix GeneChip Operating Software (GCOS) Version 1.4.
2010-12-03 | E-GEOD-25814 | biostudies-arrayexpress
Project description:The involvement the thioredoxin system in radiation resistance was investigated in human lung cancer cells by a combination of ionizing radiation and specific thioredoxin reductase-inhibition by a phosphine gold compound.
2010-12-03 | GSE25814 | GEO
Project description:The endoplasmic reticulum (ER) is responsible for protein folding, modification, and trafficking. Accumulation of unfolded or misfolded proteins represents the condition of ER stress and triggers the unfolded protein response (UPR), a key mechanism linking supply of excess nutrients to insulin resistance and type 2 diabetes in obesity. The ER harbors proteins that participate in protein folding including protein disulfide isomerases (PDIs). Changes in PDI activity are associated with protein misfolding and ER stress. Here, we show that thioredoxin-interacting protein (Txnip), a member of the arrestin protein superfamily and one of the most strongly induced proteins in diabetic patients, regulates PDI activity and UPR signaling. We found that Txnip binds to PDIs and increases their enzymatic activity. Genetic deletion of Txnip in cells and mice led to increased protein ubiquitination and splicing of the UPR regulated transcription factor X-box-binding protein 1 (Xbp1s) at baseline as well as under ER stress. Our results reveal Txnip as a novel direct regulator of PDI activity and a feedback mechanism of UPR signaling to decrease ER stress.
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