ERO1: A protein disulfide oxidase and H2O2 producer

none1no: Oxidative protein folding in the endoplasmic reticulum (ER) is an essential function of eukaryotic cells that requires the relaying of electrons between the proteinaceous components of the pathway. During this process, protein disulfide isomerase (PDI) chaperones oxidatively fold their client proteins before endoplasmic reticulum oxireductin 1 (ERO1) oxidase transfers electrons from the reduced PDI to the terminal acceptor, which is usually molecular oxygen and is subsequently reduced to H2O2. ERO1 function is essential for disulfide bond formation in yeast, whereas in mammals its function is compensated for by alternative pathways. ERO1 activity is allosterically and transcriptionally regulated by the ER unfolded protein response (UPR). The ER stress-induced upregulation of ERO1 and other genes contributes to a cell's ability to cope with ER stress as a result of an adaptive homeostatic response, but the stress persists if a "maladaptive UPR" fails to reestablish ER homeostasis. As the oxidative activity of ERO1 is related to the production of H2O2 and consequently burdens cells with potentially toxic reactive oxygen species, deregulated ERO1 activity is likely to impair cell fitness under certain conditions of severe ER stress and may therefore lead to a change from an adaptive to a maladaptive UPR. This review summarizes the evidence of the double-edged sword activity of ERO1 by highlighting its role as a protein disulfide oxidase and H2O2 producer.openZito, EsterZito, Este

PRDX4, an endoplasmic reticulum-localized peroxiredoxin at the crossroads between enzymatic oxidative protein folding and nonenzymatic protein oxidation

none1noSignificance: Peroxiredoxin 4 (PRDX4) is an endoplasmic reticulum (ER)-resident peroxiredoxin that has the characteristic of coupling hydrogen peroxide (H(2)O(2)) catabolism with oxidative protein folding. This enzymatic arrangement involves the ingenious use of H(2)O(2) as a substrate to streamline protein metabolism. Recent advances: Mice with compound mutations in Prdx4 and Ero1 have revealed the physiological implication that PRDX4 is a fine-tuned enzymatic mediator of oxidative folding. Remarkably, by simultaneously triggering slow disulfide bond formation and the buildup of H(2)O(2), the lack of PRDX4 and endoplasmic oxidoreductin 1 (ERO1) exposes the thiols of new client proteins to competing H(2)O(2)-mediated oxidation, which leads to an increase in sulfenylated proteins. Such oxygenated thiol derivatives exploit ascorbate as their reductant, thus accelerating its clearance. This relay of events culminates in an altered extracellular matrix (ECM) and a senescent phenotype. Critical issues and future directions: By combining H(2)O(2) metabolism with oxidative folding, PRDX4 protects nascent proteins from an alternative oxidative fate, and cells from the consequences of having misfolded proteins. This highlights the importance of kinetic-regulated disulfide formation at physiological level, and the presence of an exquisite backup system to protect ER redox homeostasis. By altering ECM architecture, ascorbate depletion in the cells triggers an integrated signaling cascade. This sequence of events is part of a multifaceted response linking the ER and the nucleus, which helps cells to overcome ER redox impairment. Furthermore, the relationship between the protein sulfenylation and ascorbate depletion suggests that it would be interesting to explore the metabolism of ascorbate in pathological conditions accompanied by oxidative stress and a defective ECM.openZito, EsterZito, Este

Regulation of redox signaling in HIF-1-dependent tumor angiogenesis

Angiogenesis is the process of blood vessel growth. The angiogenic switch consists of new blood vessel formation that, in carcinogenesis, can lead to the transition from a harmless cluster of dormant cells to a large tumorigenic mass with metastatic potential. Hypoxia, that is, the scarcity of oxygen, is a hallmark of solid tumors to which they adapt by activating hypoxia-inducible factor-1 (HIF-1), a transcription factor triggering de novo angiogenesis. HIF-1 and the angiogenic molecules that are expressed upon its activation are modulated by redox status. Modulations of the redox environment can influence the angiogenesis signaling at different levels, thereby impinging on the angiogenic switch. This review provides a molecular overview of the redox-sensitive steps in angiogenic signaling, the main molecular players involved, and their crosstalk with the unfolded protein response. New classes of inhibitors of these modulators which might act as antiangiogenic drugs in cancer are also discussed

Disulphide production by Ero1alpha-PDI relay is rapid and effectively regulated

The molecular networks that control endoplasmic reticulum (ER) redox conditions in mammalian cells are incompletely understood. Here, we show that after reductive challenge the ER steady-state disulphide content is restored on a time scale of seconds. Both the oxidase Ero1alpha and the oxidoreductase protein disulphide isomerase (PDI) strongly contribute to the rapid recovery kinetics, but experiments in ERO1-deficient cells indicate the existence of parallel pathways for disulphide generation. We find PDI to be the main substrate of Ero1alpha, and mixed-disulphide complexes of Ero1 primarily form with PDI, to a lesser extent with the PDI-family members ERp57 and ERp72, but are not detectable with another homologue TMX3. We also show for the first time that the oxidation level of PDIs and glutathione is precisely regulated. Apparently, this is achieved neither through ER import of thiols nor by transport of disulphides to the Golgi apparatus. Instead, our data suggest that a dynamic equilibrium between Ero1- and glutathione disulphide-mediated oxidation of PDIs constitutes an important element of ER redox homeostasis

Endoplasmic reticulum thiol oxidase deficiency leads to ascorbic acid depletion and noncanonical scurvy in mice

none5sì: Endoplasmic reticulum (ER) thiol oxidases initiate a disulfide relay to oxidatively fold secreted proteins. We found that combined loss-of-function mutations in genes encoding the ER thiol oxidases ERO1α, ERO1β, and PRDX4 compromised the extracellular matrix in mice and interfered with the intracellular maturation of procollagen. These severe abnormalities were associated with an unexpectedly modest delay in disulfide bond formation in secreted proteins but a profound, 5-fold lower procollagen 4-hydroxyproline content and enhanced cysteinyl sulfenic acid modification of ER proteins. Tissue ascorbic acid content was lower in mutant mice, and ascorbic acid supplementation improved procollagen maturation and lowered sulfenic acid content in vivo. In vitro, the presence of a sulfenic acid donor accelerated the oxidative inactivation of ascorbate by an H(2)O(2)-generating system. Compromised ER disulfide relay thus exposes protein thiols to competing oxidation to sulfenic acid, resulting in depletion of ascorbic acid, impaired procollagen proline 4-hydroxylation, and a noncanonical form of scurvy.openZito, Ester; Hansen, Henning Gram; Yeo, Giles S H; Fujii, Junichi; Ron, DavidZito, Ester; Hansen, Henning Gram; Yeo, Giles S H; Fujii, Junichi; Ron, Davi

Loss-of-rescue of Ryr1I4895T-related pathology by the genetic inhibition of the ER stress response mediator CHOP

RYR1 is the gene encoding the ryanodine receptor 1, a calcium release channel of the endo/sarcoplasmic reticulum. I4898T in RYR1 is one of the most common mutations that give rise to central core disease (CCD), with a variable phenotype ranging from mild to severe myopathy to lethal early-onset core-rod myopathy. Mice with the corresponding I4895T mutation in Ryr1 present mild myopathy when the mutation is heterozygous while I4895T homozygous is perinatal-lethal. Here we show that skeletal muscles of I4895T homozygous mice at birth present signs of stress of the endoplasmic reticulum (ER stress) and of the related unfolded protein response (UPR) with increased levels of the maladaptive mediators CHOP and ERO1. To gain information on the role of CHOP in the pathogenesis of RYR1I4895T-related myopathy, we generated compound Ryr1I4895T, Chop knock-out (-/-) mice. However, the genetic deletion of Chop, although it attenuates ER stress in the skeletal muscle of the newborns, does not rescue any phenotypic or functional features of Ryr1I4895T in mice: neither the perinatal-lethal phenotype nor the inability of Ryr1I4895T to respond to its agonist caffeine, but protects from ER stress-induced apoptosis. These findings suggest that genetic deletion of the ER stress response mediator CHOP is not sufficient to counteract the pathological Ryr1I4895T phenotype

Tissue-Resident Innate Immune Cell-Based Therapy: A Cornerstone of Immunotherapy Strategies for Cancer Treatment

Cancer immunotherapy has led to impressive advances in cancer treatment. Unfortunately, in a high percentage of patients is difficult to consistently restore immune responses to eradicate established tumors. It is well accepted that adaptive immune cells, such as B lymphocytes, CD4+ helper T lymphocytes, and CD8+ cytotoxic T-lymphocytes (CTLs), are the most effective cells able to eliminate tumors. However, it has been recently reported that innate immune cells, including natural killer cells (NK), dendritic cells (DC), macrophages, myeloid-derived suppressor cells (MDSCs), and innate lymphoid cells (ILCs), represent important contributors to modulating the tumor microenvironment and shaping the adaptive tumor response. In fact, their role as a bridge to adaptive immunity, make them an attractive therapeutic target for cancer treatment. Here, we provide a comprehensive overview of the pleiotropic role of tissue-resident innate immune cells in different tumor contexts. In addition, we discuss how current and future therapeutic approaches targeting innate immune cells sustain the adaptive immune system in order to improve the efficacy of current tumor immunotherapies

The sarcoplasmic reticulum luminal thiol oxidase ERO1 regulates cardiomyocyte excitation-coupled calcium release and response to hemodynamic load

: Two related ER oxidation 1 (ERO1) proteins, ERO1α and ERO1β, dynamically regulate the redox environment in the mammalian endoplasmic reticulum (ER). Redox changes in cysteine residues on intralumenal loops of calcium release and reuptake channels have been implicated in altered calcium release and reuptake. These findings led us to hypothesize that altered ERO1 activity may affect cardiac functions that are dependent on intracellular calcium flux. We established mouse lines with loss of function insertion mutations in Ero1l and Ero1lb encoding ERO1α and ERO1β. The peak amplitude of calcium transients in homozygous Ero1α mutant adult cardiomyocytes was reduced to 42.0 ± 2.2% (n=10, P ≤ 0.01) of values recorded in wild-type cardiomyocytes. Decreased ERO1 activity blunted cardiomyocyte inotropic response to adrenergic stimulation and sensitized mice to adrenergic blockade. Whereas all 12 wild-type mice survived challenge with 4 mg/kg esmolol, 6 of 8 compound Ero1l and Ero1lb mutant mice succumbed to this level of β adrenergic blockade (P ≤ 0.01). In addition, mice lacking ERO1α were partially protected against progressive heart failure in a transaortic constriction model [at 10 wk postprocedure, fractional shortening was 0.31 ± 0.02 in the mutant (n=20) vs. 0.23 ± 0.03 in the wild type (n=18); P ≤ 0.01]. These findings establish a role for ERO1 in calcium homeostasis and suggest that modifying the lumenal redox environment may affect the progression of heart failure