Roles of the protein disulphide isomerases AccPDIA1 and AccPDIA3 in response to oxidant stress in Apis cerana cerana

Protein disulphide isomerase (PDI) plays an important role in a variety of physiological processes through its oxidoreductase activity and molecular chaperone activity. In this study, we cloned two PDI family members, AccPDIA1 and AccPDIA3, from Apis cerana cerana. AccPDIA1 and AccPDIA3 had typical sequence features of PDI family members and were constitutively expressed in A. cerana cerana. The expression levels of AccPDIA1 and AccPDIA3 were generally upregulated after treatment with a variety of environmental stress factors. Inhibition assays showed that E. coli expressing recombinant AccPDIA1 and AccPDIA3 proteins was more resistant to oxidative stress than control E. coli. In addition, silencing AccPDIA1 or AccPDIA3 in A. cerana cerana resulted in significant changes in the expression levels of several antioxidant-related genes as well as the enzymatic activities of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) and reduced the survival rate of A. cerana cerana under oxidative stress caused by high temperature. In conclusion, our results suggest that AccPDIA1 and AccPDIA3 may play important roles in the antioxidant activities of A. cerana cerana.

Protein Disulphide Isomerase and NADPH Oxidase 1 Cooperate to Control Platelet Function and Are Associated with Cardiometabolic Disease Risk Factors

Background: Protein disulphide isomerase (PDI) and NADPH oxidase 1 (Nox-1) regulate platelet function and reactive oxygen species (ROS) generation, suggesting potentially interdependent roles. Increased platelet reactivity and ROS production have been correlated with cardiometabolic disease risk factors. Objectives: To establish whether PDI and Nox-1 cooperate to control platelet function. Methods: Immunofluorescence microscopy was utilised to determine expression and localisation of PDI and Nox-1. Platelet aggregation, fibrinogen binding, P-selectin exposure, spreading and calcium mobilization were measured as markers of platelet function. A cross-sectional population study (n = 136) was conducted to assess the relationship between platelet PDI and Nox-1 levels and cardiometabolic risk factors. Results: PDI and Nox-1 co-localized upon activation induced by the collagen receptor GPVI. Co-inhibition of PDI and Nox-1 led to additive inhibition of GPVI-mediated platelet aggregation, activation and calcium flux. This was confirmed in murine Nox-1^−/− platelets treated with PDI inhibitor bepristat, without affecting bleeding. PDI and Nox-1 together contributed to GPVI signalling that involved the phosphorylation of p38 MAPK, p47phox, PKC and Akt. Platelet PDI and Nox-1 levels were upregulated in obesity, with platelet Nox-1 also elevated in hypertensive individuals. Conclusions: We show that PDI and Nox-1 cooperate to control platelet function and are associated with cardiometabolic risk factors.

Protein disulphide isomerase inhibition as a potential cancer therapeutic strategy

The protein disulphide isomerase (PDI) gene family is a large, diverse group of enzymes recognised for their roles in disulphide bond formation within the endoplasmic reticulum (ER). PDI therefore plays an important role in ER proteostasis, however, it also shows involvement in ER stress, a characteristic recognised in multiple disease states, including cancer. While the exact mechanisms by which PDI contributes to tumorigenesis are still not fully understood, PDI exhibits clear involvement in the unfolded protein response (UPR) pathway. The UPR acts to alleviate ER stress through the activation of ER chaperones, such as PDI, which act to refold misfolded proteins, promoting cell survival. PDI also acts as an upstream regulator of the UPR pathway, through redox regulation of UPR stress receptors. This demonstrates the pro‐protective roles of PDI and highlights PDI as a potential therapeutic target for cancer treatment. Recent research has explored the use of PDI inhibitors with PACMA 31 in particular, demonstrating promising anti‐cancer effects in ovarian cancer. This review discusses the properties and functions of PDI family members and focuses on their potential as a therapeutic target for cancer treatment.

Hydrogen sulphide reduces hyperhomocysteinaemia-induced endothelial ER stress by sulfhydrating protein disulphide isomerase to attenuate atherosclerosis

Hyperhomocysteinaemia (HHcy)-impaired endothelial dysfunction including endoplasmic reticulum (ER) stress plays a crucial role in atherogenesis. Hydrogen sulphide (H₂ S), a metabolic production of Hcy and gasotransmitter, exhibits preventing cardiovascular damages induced by HHcy by reducing ER stress, but the underlying mechanism is unclear. Here, we made an atherosclerosis with HHcy mice model by ApoE knockout mice and feeding Pagien diet and drinking L-methionine water. H₂ S donors NaHS and GYY4137 treatment lowered plaque area and ER stress in this model. Protein disulphide isomerase (PDI), a modulation protein folding key enzyme, was up-regulated in plaque and reduced by H₂ S treatment. In cultured human aortic endothelial cells, Hcy dose and time dependently elevated PDI expression, but inhibited its activity, and which were rescued by H₂ S. H₂ S and its endogenous generation key enzyme-cystathionine γ lyase induced a new post-translational modification-sulfhydration of PDI. Sulfhydrated PDI enhanced its activity, and two cysteine-terminal CXXC domain of PDI was identified by site mutation. HHcy lowered PDI sulfhydration association ER stress, and H₂ S rescued it but this effect was blocked by cysteine site mutation. Conclusively, we demonstrated that H₂ S sulfhydrated PDI and enhanced its activity, reducing HHcy-induced endothelial ER stress to attenuate atherosclerosis development.

Potential effect of new (E)-4-hydroxy -N'-(1-(7-hydroxy-2-oxo-2H-chromen-3-yl) ethylidene) benzohydrazide against acute myocardial infarction: Haemodynamic, biochemical and histological studies

This study aimed to explore the cardioprotective effect of new synthesized coumarin (E)-4-hydroxy-N'-(1-(7-hydroxy-2-oxo-2H-chromen-3-yl) ethylidene) benzohydrazide denoted (Hyd.Cou) against myocardial infarction disorders. Male Wistar rats were divided into four groups; Control, isoproterenol (ISO), ISO + Acenocoumarol (Ac) and ISO + Hyd.Cou. Results showed that the ISO group exhibited serious alteration in EGC pattern, significant heart hypertrophy (+33%), haemodynamic disturbance and increase in plasma rate of CK-MB, LDH and troponin-T by 44, 53, and 170%, respectively, as compared to Control. Moreover, isoproterenol induced a rise in plasma angiotensin-converting enzyme activity (ACE) by 49%, dyslipidaemia, and increased thiobarbituric acid-reactive substances (TBARS) by 117% associated with decrease in the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx) by 46% and 58%, respectively in myocardium. Interestingly, the molecular docking calculation demonstrated strong interactions of Hyd.Cou with the receptors of the protein disulphide isomerase (PDI) which could highlight the antithrombotic effect. Moreover, Hyd.Cou improved plasma cardiac dysfunction biomarkers, mitigated the ventricle remodelling process and alleviated heart oxidative stress damage. Overall, Hyd.Cou prevented the heart from the remodelling process through inhibition of ACE activity and oxidative stress improvement.

Molecular docking-assisted screening reveals tannic acid as a natural protein disulphide isomerase inhibitor with antiplatelet and antithrombotic activities

Protein disulphide isomerase (PDI) promotes platelet activation and constitutes a novel antithrombotic target. In this study, we reported that a PDI‐binding plant polyphenol, tannic acid (TA), inhibits PDI activity, platelet activation and thrombus formation. Molecular docking using plant polyphenols from dietary sources with cardiovascular benefits revealed TA as the most potent binding molecule with PDI active centre. Surface plasmon resonance demonstrated that TA bound PDI with high affinity. Using Di‐eosin‐glutathione disulphide fluorescence assay and PDI assay kit, we showed that TA inhibited PDI activity. In isolated platelets, TA inhibited platelet aggregation stimulated by either GPVI or ITAM pathway agonists. Flow cytometry showed that TA inhibited thrombin‐ or CRP‐stimulated platelet activation, as reflected by reduced granule secretion and integrin activation. TA also reduced platelet spreading on immobilized fibrinogen and platelet adhesion under flow conditions. In a laser‐induced vascular injury mouse model, intraperitoneal injection of TA significantly decreased the size of cremaster arteriole thrombi. No prolongation of mouse jugular vein and tail‐bleeding time was observed after TA administration. Therefore, we identified TA from natural polyphenols as a novel inhibitor of PDI function. TA inhibits platelet activation and thrombus formation, suggesting it as a potential antithrombotic agent.

A novel soybean protein disulphide isomerase family protein possesses dithiol oxidation activity: identification and characterization of GmPDIL6

Secretory and membrane proteins synthesized in the endoplasmic reticulum (ER) are folded with intramolecular disulphide bonds, viz. oxidative folding, catalysed by the protein disulphide isomerase (PDI) family proteins. Here, we identified a novel soybean PDI family protein, GmPDIL6. GmPDIL6 has a single thioredoxin-domain with a putative N-terminal signal peptide and an active centre (CKHC). Recombinant GmPDIL6 forms various oligomers binding iron. Oligomers with or without iron binding and monomers exhibited a dithiol oxidase activity level comparable to those of other soybean PDI family proteins. However, they displayed no disulphide reductase and extremely low oxidative refolding activity. Interestingly, GmPDIL6 was mainly expressed in the cotyledon during synthesis of seed storage proteins and GmPDIL6 mRNA was up-regulated under ER stress. GmPDIL6 may play a role in the formation of disulphide bonds in nascent proteins for oxidative folding in the ER.

Protein disulphide isomerase can predict the clinical prognostic value and contribute to malignant progression in gliomas

Increasing evidence from structural and functional studies has indicated that protein disulphide isomerase (PDI) has a critical role in the proliferation, survival and metastasis of several types of cancer. However, the molecular mechanisms through which PDI contributes to glioma remain unclear. Here, we aimed to investigate whether the differential expression of 17 PDI family members was closely related to the different clinicopathological features in gliomas from The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas data sets. Additionally, four subgroups of gliomas (cluster 1/2/3/4) were identified based on consensus clustering of the PDI gene family. These findings not only demonstrated that a poorer prognosis, higher WHO grade, lower frequency of isocitrate dehydrogenase mutation and higher 1p/19q non‐codeletion status were significantly correlated with cluster 4 compared with the other clusters, but also indicated that the malignant progression of glioma was closely correlated with the expression of PDI family members. Moreover, we also constructed an independent prognostic marker that can predict the clinicopathological features of gliomas. Overall, the results indicated that PDI family members may serve as possible diagnostic markers in gliomas.

Cytoplasmic Restriction of Mutated SOD1 Impairs the DNA Repair Process in Spinal Cord Neurons

Amyotrophic lateral sclerosis (ALS) caused by mutation of superoxide dismutase 1 (SOD1), affects various cellular processes and results in the death of motor neurons with fatal defects. Currently, several neurological disorders associated with DNA damage are known to directly induce neurodegenerative diseases. In this research, we found that cytoplasmic restriction of SOD1G93A, which inhibited the nucleic translocation of SOD1WT, was directly related to increasing DNA damage in SOD1- mutated ALS disease. Our study showed that nucleic transport of DNA repair- processing proteins, such as p53, APEX1, HDAC1, and ALS- linked FUS were interfered with under increased endoplasmic reticulum (ER) stress in the presence of SOD1G93A. During aging, the unsuccessful recognition and repair process of damaged DNA, due to the mislocalized DNA repair proteins might be closely associated with the enhanced susceptibility of DNA damage in SOD1- mutated neurons. In addition, the co-expression of protein disulphide isomerase (PDI) directly interacting with SOD1 protein in neurons enhances the nucleic transport of cytoplasmic- restricted SOD1G93A. Therefore, our results showed that enhanced DNA damage by SOD1 mutation-induced ALS disease and further suggested that PDI could be a strong candidate molecule to protect neuronal apoptosis by reducing DNA damage in ALS disease.

Expression and release of platelet protein disulphide isomerase in patients with haemophilia A

INTRODUCTION

Despite similar residual factor VIII activity, patients with haemophilia A (HA) show significant interindividual variability with regard to bleeding frequency and severity, suggesting that additional factors modulate thrombin generation and fibrin deposition. Protein disulphide isomerase (PDI) is an abundant oxidoreductase that exerts pleiotropic effects in primary and secondary haemostasis and contributes to thrombosis and vascular inflammation.

AIM

We conducted a pilot study to explore a potential role of platelet PDI in patients with HA.

METHODS

Expression and release of platelet PDI were studied by flow cytometry and enzyme-linked immunosorbent assay, respectively.

RESULTS

Compared to healthy male controls (n = 12), patients with HA (n = 24) showed significantly increased expression of PDI antigen on ADP- or TRAP-6-, but not on buffer-treated platelets, a finding that could not be explained by enhanced platelet activation, as indicated by expression of the α-granule protein, CD62P (P-selectin). While platelet agonists did not affect PDI secretion in healthy male controls, increased levels of PDI antigen were found in supernatants of TRAP-6-treated platelets from patients with HA. Importantly, in two patients with exceedingly high TRAP-6-induced PDI release over baseline, findings were consistent when platelets were isolated and stimulated on a separate occasion. No obvious association was found between platelet PDI and bleeding phenotype in this patient cohort.

CONCLUSION

Agonist-induced expression and release of platelet PDI were increased in patients with HA. Larger studies are needed to clarify if variations in this platelet response contribute to the diversity in bleeding frequency and severity among patients with congenital factor VIII deficiency.

Secretion of protein disulphide isomerase AGR2 confers tumorigenic properties

The extracellular matrix (ECM) plays an instrumental role in determining the spatial orientation of epithelial polarity and the formation of lumens in glandular tissues during morphogenesis. Here, we show that the Endoplasmic Reticulum (ER)-resident protein anterior gradient-2 (AGR2), a soluble protein-disulfide isomerase involved in ER protein folding and quality control, is secreted and interacts with the ECM. Extracellular AGR2 (eAGR2) is a microenvironmental regulator of epithelial tissue architecture, which plays a role in the preneoplastic phenotype and contributes to epithelial tumorigenicity. Indeed, eAGR2, is secreted as a functionally active protein independently of its thioredoxin-like domain (CXXS) and of its ER-retention domain (KTEL), and is sufficient, by itself, to promote the acquisition of invasive and metastatic features. Therefore, we conclude that eAGR2 plays an extracellular role independent of its ER function and we elucidate this gain-of-function as a novel and unexpected critical ECM microenvironmental pro-oncogenic regulator of epithelial morphogenesis and tumorigenesis.

DOI:http://dx.doi.org/10.7554/eLife.13887.001

Cancer cells multiply abnormally fast and therefore produce protein molecules faster than normal cells. To avoid becoming stressed by this overproduction, cancer cells make use of proteins that fold the new proteins inside the cell. One of these protein folders is called anterior gradient-2 (or AGR2 for short) and is produced at high levels in so-called epithelial cancers, such as breast and lung cancer.

Previous research has shown that AGR2 inside cancer cells can help them grow and survive and AGR2 can also be found outside cells, such as in the blood or the urine of cancer patients. Therefore some researchers have suggested that measuring the levels of AGR2 in bodily fluids may be a useful marker for detecting cancers. Fessart et al. hypothesized that – apart from becoming a promising diagnostic tool – the AGR2 protein itself, specifically when found outside cells, might make cancer cells more aggressive.

Fessart et al. used a range of techniques to test this hypothesis. For example, healthy lung cells and lung cancer cells were grown into miniature replicas of lung organs in the laboratory, and in a key experiment, AGR2 was added to the lung organoids grown from the healthy cells. The addition of AGR2 protein was enough to change the non-tumor organoids into tumor organoids and boosted their growth about ten-fold. Further experiments then revealed that AGR2 also makes cells more invasive and capable of moving, both important features of aggressive cancer cells.

Overall, Fessart et al. have proven that AGR2 is a signalling molecule found outside cancer cells that makes them more aggressive. In future, more research addressing how AGR2 achieves this may lead to new therapeutic strategies against some forms of cancer.

DOI:http://dx.doi.org/10.7554/eLife.13887.002

Immunomodulation mediated through Leishmania donovani protein disulfide isomerase by eliciting CD8+ T-cell in cured visceral leishmaniasis subjects and identification of its possible HLA class-1 restricted T-cell epitopes

Protein disulphide isomerase (PDI) is one of the key enzymes essential for the survival of Leishmania donovani in the host. Our study suggested that PDI is associated with the generation of Th1-type of cellular responses in treated Visceral leishmaniasis (VL) subjects. The stimulation of Peripheral blood mononuclear cells (PBMCs) with recombinant Protein Disulphide Isomerase upregulated the reactive oxygen species generation, Nitric oxide release, IL12 and IFN-γ production indicating its pivotal role in protective immune response. Further, a pre-stimulation of PBMCs with Protein disulphide isomerase induced a strong IFN-γ response through CD8+ T cells in treated VL subjects. These findings also supported through the evidence that this antigen was processed and presented by major histocompatibility complex class I (MHC-1) dependent pathway and had an immunoprophylactic potential which can induce CD8+ T cell protective immune response in MHC class I dependent manner against VL. To find out the possible epitopes that might be responsible for CD8+ T cell specific IFN-γ response, computational approach was adopted. Six novel promiscuous epitopes were predicted to be highly immunogenic and can be presented by 32 different HLA allele to CD8+ T cells. Further investigation will explore more about their immunological relevance and usefulness as vaccine candidates.

Cooperation of both, the FKBP_N-like and the DSBA-like, domains is necessary for the correct function of FTS_1067 protein involved in Francisella tularensis virulence and pathogenesis

Francisella tularensis the etiological agent of tularaemia is one of the most infectious human pathogen known. Our knowledge about its key virulence factors has increased recently but it still remains a lot to explore. One of the described essential virulence factors is membrane lipoprotein FTS_1067 (nomenclature of F. tularensis subsp. holarctica strain FSC200) with homology to the protein family of disulphide oxidoreductases DsbA. Lipoprotein consists of two different domains: the C-terminal DsbA_Com1-like domain (DSBA-like) and the N-terminal FKBP-type peptidyl-prolyl cis/trans isomerases (FKBP_N-like). To uncover the biological role of these domains, we created bacterial strain with deletion of the DSBA-like domain. This defect in gene coding for lipoprotein FTS_1067 led to high in vivo attenuation associated with the ability to induce host protective immunity. Analyses performed with the truncated recombinant protein showed that the absence of DSBA-like domain revealed the loss of thiol/disulphide oxidoreductase activity and, additionally, confirmed the role of the FKBP_N-like domain in the FTS_1067 oligomerization and chaperone-like function. Finally, we verified that only full-length form of FTS_1067 recombinant protein possesses the isomerase activity. Based on our results, we proposed that for the correct FTS_1067 protein function both domains are needed.

Heterogeneous nuclear ribonucleoprotein E1 regulates protein disulphide isomerase translation in oxidized low-density lipoprotein-activated endothelial cells

AIMS

Endothelium-derived protein disulphide isomerase (PDI) is required for thrombus formation in vivo. But, how to control PDI overproduction in oxidized low-density lipoprotein (oxLDL)-activated vascular endothelial cells (VECs) is not well understood. In this study, we try to answer this question using our newly identified activator of mTOC1 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2 (3H)-one (3BDO) that has been shown to protect VECs.

METHODS

First, we performed a proteomics analysis on the oxLDL-activated vascular VECs in the presence or absence of 3BDO. Next, we constructed the heterogeneous nuclear ribonucleoprotein E1 (hnRNP E1) mutants at Ser43 and used the RNA-ChIP technique to investigate the relationship between hnRNP E1 and PDI production. Furthermore, we examined the effect of 3BDO on oxLDL-altered phosphorylation of Akt1 and Akt2. Finally, we studied the effect of 3BDO on oxLDL-altered PDI protein level in apolipoprotein E(-/-) mice with advanced atherosclerosis.

RESULTS

In VECs, oxLDL-increased PDI protein level, induced hnRNP E1 phosphorylation at Ser43, suppressed the binding of hnRNP E1 to PDI 5'UTR and induced the phosphorylation of Akt2 but not Akt1. All of these processes were blocked by 3BDO. Importantly, Ser43 mutant of hnRNP E1 inhibited the increase of PDI protein level and the decrease of the binding of hnRNP E1 and PDI 5'UTR induced by oxLDL. Furthermore, 3BDO suppressed oxLDL-induced PDI protein increase in the serum and plaque endothelium of apolipoprotein E(-/-) mice.

CONCLUSION

hnRNP E1 is a new regulator of PDI translation in oxLDL-activated VECs, and 3BDO is a powerful agent for controlling PDI overproduction.

Inhibition of storage pathology in prenatal CLN5-deficient sheep neural cultures by lentiviral gene therapy

The neuronal ceroid lipofuscinoses (NCLs, Batten disease) are inherited neurodegenerative lysosomal storage diseases caused by mutations in several different genes. Mutations in CLN5 cause a variant late-infantile human disease and some cases of juvenile and adult clinical disease. NCLs also occur in animals, and a flock of New Zealand Borderdale sheep with a CLN5 splice-site mutation has been developed for model studies. Dissociated mixed neural cells from CLN5-deficient foetal sheep brains contained no obvious storage bodies at plating but these accumulated rapidly in culture, mainly in microglial cells and also in neurons and astrocytes. Accumulation was very obvious after a week, as monitored by fluorescent microscopy and immunostaining for subunit c of mitochondrial ATP synthase. Photography at intervals revealed the dynamic nature of the cultures and a flow of storage bodies between cells, specifically the phagocytosis of storage-body containing cells by microglia and incorporation of the storage bodies into the host cells. No storage was observed in cultured control cells. Transduction of cell cultures with a lentiviral vector expressing a C-terminal Myc tagged CLN5 resulted in secretion of post-translationally glycosylated and processed CLN5. Transduction of CLN5-deficient cultures with this construct rapidly reversed storage body accumulation, to less than half in only six days. These results show that storage body accumulation is reversible with enzyme correction and support the use of these cultures for testing of therapeutics prior to whole animal studies.

Role of the ubiquitin-proteasome system in brain ischemia: friend or foe?

The ubiquitin-proteasome system (UPS) is a catalytic machinery that targets numerous cellular proteins for degradation, thus being essential to control a wide range of basic cellular processes and cell survival. Degradation of intracellular proteins via the UPS is a tightly regulated process initiated by tagging a target protein with a specific ubiquitin chain. Neurons are particularly vulnerable to any change in protein composition, and therefore the UPS is a key regulator of neuronal physiology. Alterations in UPS activity may induce pathological responses, ultimately leading to neuronal cell death. Brain ischemia triggers a complex series of biochemical and molecular mechanisms, such as an inflammatory response, an exacerbated production of misfolded and oxidized proteins, due to oxidative stress, and the breakdown of cellular integrity mainly mediated by excitotoxic glutamatergic signaling. Brain ischemia also damages protein degradation pathways which, together with the overproduction of damaged proteins and consequent upregulation of ubiquitin-conjugated proteins, contribute to the accumulation of ubiquitin-containing proteinaceous deposits. Despite recent advances, the factors leading to deposition of such aggregates after cerebral ischemic injury remain poorly understood. This review discusses the current knowledge on the role of the UPS in brain function and the molecular mechanisms contributing to UPS dysfunction in brain ischemia with consequent accumulation of ubiquitin-containing proteins. Chemical inhibitors of the proteasome and small molecule inhibitors of deubiquitinating enzymes, which promote the degradation of proteins by the proteasome, were both shown to provide neuroprotection in brain ischemia, and this apparent contradiction is also discussed in this review.

p-Hydroxybenzyl alcohol prevents brain injury and behavioral impairment by activating Nrf2, PDI, and neurotrophic factor genes in a rat model of brain ischemia

The therapeutic goal in treating cerebral ischemia is to reduce the extent of brain injury and thus minimize neurological impairment. We examined the effects of p-hydroxybenzyl alcohol (HBA), an active component of Gastrodia elata Blume, on transient focal cerebral ischemia-induced brain injury with respect to the involvement of protein disulphide isomerase (PDI), nuclear factor-E2-related factor 2 (Nrf2), and neurotrophic factors. All animals were ovariectomized 14 days before ischemic injury. Ischemic injury was induced for 1 h by middle cerebral artery occlusion (MCAO) followed by 24-h reperfusion. Three days before MCAO, the vehicle-treated and the HBA-treated groups received intramuscular sesame oil and HBA (25 mg/kg BW), respectively. 2,3,5-Triphenyltetrazolium chloride (TTC) staining showed decreased infarct volume in the ischemic lesion of HBA-treated animals. HBA pretreatment also promoted functional recovery, as measured by the modified neurological severity score (mNSS; p < 0.05). Moreover, expression of PDI, Nrf2, BDNF, GDNF, and MBP genes increased by HBA treatment. In vitro, H(2)O(2)-induced PC12 cell death was prevented by 24 h HBA treatment, but bacitracin, a PDI inhibitor, attenuated this cytoprotective effect in a dose-dependent manner. HBA treatment for 2 h also induced nuclear translocation of Nrf2, possibly activating the intracellular antioxidative system. These results suggest that HBA protects against brain damage by modulating cytoprotective genes, such as Nrf2 and PDI, and neurotrophic factors.

Disulphide production by Ero1α-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 Ero1α 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 Ero1α, 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.

S-nitrosothiols as selective antithrombotic agents - possible mechanisms

S-nitrosothiols have a number of potential clinical applications, among which their use as antithrombotic agents has been emphasized. This is largely because of their well-documented platelet inhibitory effects, which show a degree of platelet selectivity, although the mechanism of this remains undefined. Recent progress in understanding how nitric oxide (NO)-related signalling is delivered into cells from stable S-nitrosothiol compounds has revealed a variety of pathways, in particular denitrosation by enzymes located at the cell surface, and transport of intact S-nitrosocysteine via the amino acid transporter system-L (L-AT). Differences in the role of these pathways in platelets and vascular cells may in part explain the reported platelet-selective action. In addition, emerging evidence that S-nitrosothiols regulate key targets on the exofacial surfaces of cells involved in the thrombotic process (for example, protein disulphide isomerase, integrins and tissue factor) suggests novel antithrombotic actions, which may not even require transmembrane delivery of NO.