Exposure of the Promonocytic Cell Line THP-1 to Escherichia coli Induces IFN-γ-Inducible Lysosomal Thiol Reductase Expression by Inflammatory Cytokines

Nudt15-mediated inflammatory signaling contributes to divergent outcomes in leukemogenesis and hematopoiesis

NUDT15 encodes nucleotide triphosphate diphosphatase that is responsible for metabolizing purine analog drugs, and its genetic mutation results in severe side effects from thiopurine therapy. However, the functions of Nudt15 in leukemic stem cells (LSCs) and hematopoietic stem cells (HSCs) remain unknown. Here we reveal the Nudt15-regulating self-renewal of both mouse LSCs and HSCs. Our data show that Nudt15 negatively regulates murine leukemogenesis and its deficiency prolongs the survival of murine AML recipients by impairing LSC self-renewal, while Nudt15 ablation markedly enhances mouse HSC regenerative potential and self-renewal. Mechanistically, Nudt15 modulates inflammatory signaling in mouse LSCs and HSCs, leading to divergent self-renewal outcomes. Nudt15 depletion inhibits mouse LSC self-renewal by downregulating Ifi30, resulting in elevating intracellular ROS level. Gata2, a key regulator, is required for Nudt15-mediating inflammatory signaling in mouse HSCs. Collectively, our results present new crucial roles of Nudt15 in maintaining the functions of mouse LSC and HSC through inflammatory signaling and have a new insight into clinical implications.

Interferon Gamma Inducible Protein 30: from biological functions to potential therapeutic target in cancers

Interferon Gamma Inducible Protein 30 (IFI30), also known as Gamma-Interferon-Inducible Lysosomal Thiol Reductase (GILT), is predominantly found in lysosomes and the cytoplasm. As the sole enzyme identified to catalyze disulfide bond reduction in the endocytic pathway, IFI30 contributes to both major histocompatibility complex (MHC) class I-restricted antigen cross-presentation and MHC class II-restricted antigen processing by decreasing the disulfide bonds of endocytosed proteins. Remarkably, emerging research has revealed that IFI30 is involved in tumorigenesis, tumor development, and the tumor immune response. Targeting IFI30 may provide new strategies for cancer therapy and improve the prognosis of patients. This review provided a comprehensive overview of the research progress on IFI30 in tumor progression, cellular redox status, autophagy, tumor immune response, and drug sensitivity, with a view to providing the theoretical basis for pharmacological intervention of IFI30 in tumor therapy, particularly in immunotherapy.

Antibacterial responses and functional characterization of the interferon gamma inducible lysosomal thiol reductase (GILT) protein in Chinese mitten crab (Eriocheir sinensis)

The inducible reductase of interferon gamma (IFN- γ), IFN-γ-induced lysosomal thiol reductase (GILT) is important in antiviral immunity, but its mechanism in invertebrate antimicrobial immunity is unclear. We determined that GILT protein was involved in the antibacterial immunity of Chinese mitten crab (Eriocheir sinensis). GILT protein was highly expressed in crab hemocytes and was significantly upregulated 6 h after bacterial stimulation. Recombinant E. sinensis GILT (rEsGILT) contained a CXXS active site that catalyzed disulfide bond reduction. Vibrio parahaemolyticus and Staphylococcus aureus were bound through interaction with peptidoglycan and lipopolysaccharide, respectively, and bacterial agglutination and clearance in the crabs was markedly promoted. Nevertheless, EsGILT exhibited no direct antibacterial or bactericidal activity. EsGILT also promoted crab hemocyte phagocytosis and played an anti-bacterial role, and inhibited hemocyte apoptosis. In summary, EsGILT promoted bacterial agglutination, clearance, and phagocytosis by recognizing and agglutinating pathogenic microorganisms and reduced the apoptosis level, indirectly participating in antibacterial reactions.

Proteotranscriptomic Integration analyses reveals new mechanistic insights regarding Bombyx mori fluorosis

The commercial value of silkworms has been widely explored and the effects of fluoride exposure on silkworms' breeding and silk production cannot be ignored. Bombyx mori is a commonly used model to explore the mechanisms of fluorosis. In the present study, we analyzed the differences in physiological and biochemical indicators after exposing larva to NaF, then evaluated differential genes and proteins. Compared to control, larvae exposed to 600 mg L^-1 NaF presented decreased bodyweight, damaged midgut tissue, and were accompanied by oxidative stress. The RNA-seq showed 1493 differentially expressed genes (574 upregulated and 919 downregulated). Meanwhile, the TMT detected 189 differentially expressed proteins (133 upregulated and 56 downregulated). The integrative analysis led to 4 upregulated and 9 downregulated genes and proteins. Finally, we hypothesized that fluoride exposure might affect the intestinal digestion of silkworms, inhibit the gene expression of detoxification enzymes and stimulate cellular immune responses. Our current findings provided new insights into insect fluorosis.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

A connexin/ifi30 pathway bridges HSCs with their niche to dampen oxidative stress

Reactive oxygen species (ROS) represent a by-product of metabolism and their excess is toxic for hematopoietic stem and progenitor cells (HSPCs). During embryogenesis, a small number of HSPCs are produced from the hemogenic endothelium, before they colonize a transient organ where they expand, for example the fetal liver in mammals. In this study, we use zebrafish to understand the molecular mechanisms that are important in the caudal hematopoietic tissue (equivalent to the mammalian fetal liver) to promote HSPC expansion. High levels of ROS are deleterious for HSPCs in this niche, however this is rescued by addition of antioxidants. We show that Cx41.8 is important to lower ROS levels in HSPCs. We also demonstrate a new role for ifi30, known to be involved in the immune response. In the hematopoietic niche, Ifi30 can recycle oxidized glutathione to allow HSPCs to dampen their levels of ROS, a role that could be conserved in human fetal liver.

Reactive oxygen species (ROS) are metabolic by-products which in excess can be toxic for hematopoietic stem and progenitor cells (HSPCs). Here the authors show that toxic ROS are transferred by expanding HSPCs to the zebrafish developmental niche via connexin Cx41.8, where Ifi30 promotes their detoxification.

GILT in tumor cells improves T cell-mediated anti-tumor immune surveillance

The lysosomal thiol reductase GILT catalyzes the reduction of disulfide bonds of protein antigens, facilitating antigen-presenting cells (APCs) to present antigen to T cells. However, whether GILT expression in tumor cells can be associated with improved T cell-mediated anti-tumor responses remains unknown. Here, we identify that GILT is able to facilitate anti-tumor immune surveillance via promoting MHC class I mediated-antigen presentation in colon carcinoma. By using mice model bearing colon tumors, we find that GILT inhibites tumor growth in vivo with more leucocytes infiltration but has no effect on tumor cell development in vitro in terms of proliferation, cell cycle and migration. Furthermore, by using transgenic OT-I mice, we recognize the tumor-expressing OVA peptide, a surrogate tumor antigen, we find that GILT is capable of enhancing MHC class I mediated antigen presentation and improving specific CD8⁺ T cell anti-tumor responses in murine colon carcinoma. These findings propose the boost of GILT-MHC-I axis in tumors as a viable option for immune system against cancer.

Planarian gamma-interferon-inducible lysosomal thiol reductase (GILT) is required for gram-negative bacterial clearance

The powerful regenerative ability of planarians has long been a concern of scientists, but recently, their efficient immune system has attracted more and more attention from researchers. Gamma-interferon-inducible lysosomal thiol reductase (GILT) is related not only to antigen presentation but also to bacteria invasions. But the systematic studies are not yet to be conducted on the relationship between bacterial infection. Our study reveals for the first time that GILT of planarian (DjGILT) plays an essential role in the clearance of Gram-negative bacteria by conducting H₂O₂ concentration in planarians. In animals that DjGILT was silenced, it persisted for up to 9 days before all bacteria were cleared, compared with 6 days of the control group. When infected with E. coli and V. anguillarum, the level of H₂O₂ was significantly increased in DjGILT-silenced planarians, and concomitantly, mRNA level of C-type lectin DjCTL, which modulates agglutination and clearance efficiency of invading bacteria, was decreased. Further study showed that the decrease of H₂O₂ level led to a significant increase in DjCTL transcripts. Collectively, we proposed a mechanism model for the involvement of GILT gene in bacterial elimination. We have for the first time revealed the specific mechanism of GILT in innate immune response against bacterial infection.

IFI30 expression predicts patient prognosis in breast cancer and dictates breast cancer cells proliferation via regulating autophagy

Introduction: Incidence and mortality rates of breast cancer are increasing in women worldwide. Immunotherapy is a relatively popular treatment modality for all malignant tumors including breast cancer in recent years. Interferon γ-inducible protein 30 (IFI30) could catalyze the reduction of disulfide bonds and enhance major histocompatibility complex (MHC) class II-restricted antigen processing. Recent studies showed that IFI30 played an important role in the immune response of malignant tumors. Methods: The Cancer Genome Atlas (TCGA) database and clinical proteomic tumor Analysis consortium (CPTAC) database were applied to predict the role of IFI30 in breast cancer and the relationship between IFI30 and prognosis of breast cancer patients. Then we detected the expression of IFI30 in clinical samples of breast cancer patients, and analyzed the relationship between IFI30 and the prognosis of breast cancer patients. We used lentivirus infection method to construct a stable IFI30 knockdown cell line, and detected the effect of IFI30 in breast cancer cells. Nude mice tumor bearing experiment was performed to investigate the effect of IFI30 on breast cancer cells in vivo. Western blot was used to verify the regulation of autophagy related protein LC3 and p62 by IFI30. Results: We found that IFI30 was highly expressed in breast cancer tissues and was associated with poor outcome of patients. The knockdown of IFI30 could inhibit the proliferation, migration and invasion of breast cancer cells and significantly inhibit tumor growth in vivo. Increased accumulation of LC3-II and p62 suggested impaired autophagy in IFI30 knockdown cells. Discussion: As a result, we suggested that IFI30 might play a key role in the initiation and progression of human breast cancer and might be a new therapeutic target in breast cancer.

GILT restricts the cellular entry mediated by the envelope glycoproteins of SARS-CoV, Ebola virus and Lassa fever virus

Interferons (IFNs) control viral infections by inducing expression of IFN-stimulated genes (ISGs) that restrict distinct steps of viral replication. We report herein that gamma-interferon-inducible lysosomal thiol reductase (GILT), a lysosome-associated ISG, restricts the infectious entry of selected enveloped RNA viruses. Specifically, we demonstrated that GILT was constitutively expressed in lung epithelial cells and fibroblasts and its expression could be further induced by type II interferon. While overexpression of GILT inhibited the entry mediated by envelope glycoproteins of SARS coronavirus (SARS-CoV), Ebola virus (EBOV) and Lassa fever virus (LASV), depletion of GILT enhanced the entry mediated by these viral envelope glycoproteins. Furthermore, mutations that impaired the thiol reductase activity or disrupted the N-linked glycosylation, a posttranslational modification essential for its lysosomal localization, largely compromised GILT restriction of viral entry. We also found that the induction of GILT expression reduced the level and activity of cathepsin L, which is required for the entry of these RNA viruses in lysosomes. Our data indicate that GILT is a novel antiviral ISG that specifically inhibits the entry of selected enveloped RNA viruses in lysosomes via disruption of cathepsin L metabolism and function and may play a role in immune control and pathogenesis of these viruses.

Identification and Characterization of an OSH1 Thiol Reductase from Populus Trichocarpa

Interferon gamma-induced lysosomal thiol reductase (GILT) is abundantly expressed in antigen-presenting cells and participates in the treatment and presentation of antigens by major histocompatibility complex II. Also, GILT catalyzes the reduction of disulfide bonds, which plays an important role in cellular immunity. (1) Background: At present, the studies of GILT have mainly focused on animals. In plants, GILT homologous gene (Arabidopsis thalianaOSH1: AtOSH1) was discovered in the forward screen of mutants with compromised responses to sulphur nutrition. However, the complete properties and functions of poplar OSH1 are unclear. In addition, CdCl2 stress is swiftly engulfing the limited land resources on which humans depend, restricting agricultural production. (2) Methods: A prokaryotic expression system was used to produce recombinant PtOSH1 protein, and Western blotting was performed to identify its activity. In addition, a simplified version of the floral-dip method was used to transform A. thaliana. (3) Results: Here, we describe the identification and characterization of OSH1 from Populus trichocarpa. The deduced PtOSH1 sequence contained CQHGX2ECX2NX4C and CXXC motifs. The transcript level of PtOSH1 was increased by cadmium (Cd) treatment. In addition, recombinant PtOSH1 reduced disulfide bonds. A stress assay showed that PtOSH1-overexpressing (OE) A. thaliana lines had greater resistance to Cd than wild-type (WT) plants. Also, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in PtOSH1-OE plants were significantly higher than those in WT A. thaliana. These results indicate that PtOSH1 likely plays an important role in the response to Cd by regulating the reactive oxygen species (ROS)-scavenging system. (4) Conclusions: PtOSH1 catalyzes the reduction of disulfide bonds and behaves as a sulfhydryl reductase under acidic conditions. The overexpression of PtOSH1 in A. thaliana promoted root development, fresh weight, and dry weight; upregulated the expression levels of ROS scavenging-related genes; and improved the activity of antioxidant enzymes, enhancing plant tolerance to cadmium (Cd) stress. This study aimed to provide guidance that will facilitate future studies of the function of PtOSH1 in the response of plants to Cd stress.

High GILT Expression and an Active and Intact MHC Class II Antigen Presentation Pathway Are Associated with Improved Survival in Melanoma

The MHC class I Ag presentation pathway in melanoma cells has a well-established role in immune-mediated destruction of tumors. However, the clinical significance of the MHC class II Ag presentation pathway in melanoma cells is less clear. In Ag-presenting cells, IFN-γ-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of multiple melanoma Ags. Although not expressed in benign melanocytes of nevi, GILT and MHC class II expression is induced in malignant melanocytes in a portion of melanoma specimens. Analysis of The Cancer Genome Atlas cutaneous melanoma data set showed that high GILT mRNA expression was associated with improved overall survival. Expression of IFN-γ, TNF-α, and IL-1β was positively associated with GILT expression in melanoma specimens. These cytokines were capable of inducing GILT expression in human melanoma cells in vitro. GILT protein expression in melanocytes was induced in halo nevi, which are nevi undergoing immune-mediated regression, and is consistent with the association of GILT expression with improved survival in melanoma. To explore potential mechanisms of GILT's association with patient outcome, we investigated pathways related to GILT function and expression. In contrast to healthy skin specimens, in which the MHC class II pathway was nearly uniformly expressed and intact, there was substantial variation in the MHC class II pathway in the The Cancer Genome Atlas melanoma specimens. Both an active and intact MHC class II pathway were associated with improved overall survival in melanoma. These studies support a role for GILT and the MHC class II Ag presentation pathway in melanoma outcome.

Involvement of gamma interferon inducible lysosomal thiol reductase in the innate immune responses of red swamp crayfish, Procambarus clarkii

The Gamma interferon inducible lysosomal thiol reductase (GILT) plays a key biological role in the immune responses and involves in the processing of class II MHC-restricted antigen by stimulating disulfide bond reduction in mammals. To determine the biological function of GILT in the innate immune system of crustaceans, we sequenced and cloned GILT gene from red swamp crayfish, Procambarus clarkii (Pc-GILT). The deduced amino acid sequence of Pc-GILT contained the putative conserved structures of the GILT family proteins: the GILT signature (CQHGX2ECX2NX4C) sequence and the active site (CXXS) motif. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis suggested that a recombinant Pc-GILT protein was successfully expressed in Escherichia coli (E. coli). Quantitative real-time PCR analysis showed that Pc-GILT transcript level was highest in the hepatopancreas followed by the gut, heart and muscles. Additionally, we analyzed the transcription level of Pc-GILT gene in hepatopancreas of red swamp crayfish under biotic stress conditions. The expression of Pc-GILT gene upregulated after viral (poly I:C) and bacterial (peptidoglycan, lipopolysaccharide) infection. The suppression of Pc-GILT by double stranded RNA influenced the transcript levels of various immune-related genes. These observations indicate that the Pc-GILT probably plays a key biological role in the innate immune responses of red swamp crayfish, since it modulates the expression of genes associated with immune pathways.

Identification and characterization of the interferon-γ-inducible lysosomal thiol reductase gene in Chinese soft-shelled turtle, Pelodiscus sinensis

The reduction of disulfide bonds of exogenous antigens is crucial to the MHC-II class antigen processing and presenting pathway and is catalysed by interferon-γ-inducible lysosomal thiol reductase (GILT). In this study, a reptile GILT gene from Chinese soft-shelled turtle, Pelodiscus sinensis (PsGILT), was identified. The full-length cDNA of PsGILT is 1631 nucleotides (nt), including a 5'-untranslated region (UTR) of 3 nt, a 3'-UTR of 860 nt and an open reading frame (ORF) of 768 nt encoding 255 amino acids (aa). The conserved features in known GILTs, such as signal peptide, CXXC motif, GILT signature sequence, N-glycosylation site and conserved cysteines, were all found in the putative PsGILT protein. Genomic analysis revealed that PsGILT kept the "7 exons and 6 introns" structure of vertebrate GILT genes. PsGILT was expressed in all examined organs/tissues and was mainly expressed in spleen and blood. Increased mRNA expression levels of PsIFN-γ and PsGILT in PBLs were observed after induction with LPS, PolyI:C and recombinant IFN-γ (rIFN-γ). We also tested the reductase activity of rGILT in vitro and found that it could reduce intact human IgG into H chains and L chains. These above results implied that PsGILT may play an important role in resisting bacterial and viral infections, like other vertebrate GILTs.

The phagosome and redox control of antigen processing

In addition to debris clearance and antimicrobial function, versatile organelles known as phagosomes play an essential role in the processing of exogenous antigen in antigen presenting cells. While there has been much attention on human leukocyte antigen haplotypes in the determination of antigenic peptide repertoires, the lumenal biochemistries within phagosomes and endosomes are emerging as equally-important determinants of peptide epitope composition and immunodominance. Recently, the lumenal redox microenvironment within these degradative compartments has been shown to impact two key antigenic processing chemistries: proteolysis by lysosomal cysteine proteases and disulfide reduction of protein antigens. Through manipulation of the balance between oxidative and reductive capacities in the phagosome-principally by modulating NADPH oxidase (NOX2) and γ-interferon-inducible lysosomal thiol reductase (GILT) activities-studies have demonstrated changes to antigen processing patterns leading to modified repertoires of antigenic peptides available for presentation, and subsequently, altered disease progression in T cell-driven autoimmunity. This review focuses on the mechanisms and consequences of redox-mediated phagosomal antigen processing, and the potential downstream implications to tolerance and autoimmunity.

Immune response of interferon-γ-inducible lysosomal thiol reductase (GILT) from Chinese sturgeon (Acipenser sinensis) to microbial invasion and its antioxdative activity in lipopolysaccharides-treated mammalian dentritic cells

Interferon-γ-inducible lysosomal thiol reductase (GILT) plays an important role in the major histocompatibility complex-restricted antigen processing of endocytosed proteins via catalyzing the disulfide bond reduction in the endocytic pathway. Here, the cDNA of Chinese sturgeon (Acipenser sinensis) GILT (CsGILT) was cloned. It contained an open reading frame of 762 nucleotides encoding a protein of 254 amino acids with an estimated molecular weight of 28.1 kDa. The characteristic structural features, including a signature sequence CQHGX2ECX2NX4C, a CXXC motif, two potential N-glycosylation sites, and eight conserved cysteines were detected in the deduced amino acid sequence of CsGILT. CsGILT was widely expressed in Chinese sturgeon with the highest expression in the spleen, and CsGILT mRNA expression was significantly up-regulated when Chinese sturgeons were challenged with polyinosinic polycytidylic acid or Vibrio anguillarum. The recombinant CsGILT displayed obvious thiol reductase activity demonstrated by catalyzing the reduction of mouse IgG(H+L) by dithiothreitol into heavy chain and light chain. CsGILT also displayed significant antioxidant activity in mouse dentritic cells as indicated by its increasing GSH level and GSH/GSSG ratio, decreasing intracellular reactive oxygen species and nitric oxide levels and lipid peroxidation, as well as enhancing the activities of the antioxidative redox enzymes including catalase and superoxide dismutase. Our results suggested an important role for CsGILT in the immune response in Chinese sturgeon to pathogen invasion possibly via a conserved functional mechanism throughout vertebrate evolution, contributing to our understanding the immune biology and protection of Chinese sturgeon.

Transcriptome profiling of red swamp crayfish (Procambarus clarkii) hepatopancreas in response to lipopolysaccharide (LPS) infection

The RNA-sequencing followed by de novo assembly generated 61,912 unigene sequences of P. clarkii hepatopancreas. Comparison of gene expression between LPS challenged and PBS control samples revealed 2552 differentially expressed genes (DEGs). Of these sequences, 1162 DEGs were differentially up-regulated and 1360 DEGs differentially down-regulated. The DEGs were then annotated against gene ontology (GO) database and Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Some immune-related pathways such as PPAR signaling pathway, lysosome, Chemical carcinogenesis, Peroxisome were predicted by canonical pathways analysis. The reliability of transcriptome data was validated by quantitative real time polymerase chain reaction (qRT-PCR) for the selected genes. The data presented here shed light into antibacterial immune responses of crayfish. In addition, these results suggest that transcriptomic data provides valuable sequence resource for immune-related gene identification and helps to understand P. clarkii immune functions.

Gamma-interferon-inducible lysosomal thiol reductase is upregulated in human melanoma

T-cell-mediated immunity has the ability to produce durable antimelanoma responses, resulting in improved survival of patients with advanced melanoma. Antigen presentation is a key determinant of T-cell responses. Gamma-interferon-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of multiple melanoma antigens to CD4+ T cells. However, GILT expression in melanoma has not been defined. We evaluated GILT and MHC class II expression in human primary and metastatic melanomas and nevi using immunohistochemical analysis. GILT staining in melanocytes was observed in 70% of primary and 58% of metastatic melanomas versus 0% of nevi. When present, the GILT staining intensity in melanocytes was typically faint. Both GILT and MHC class II expression were increased in melanocytes of primary and metastatic melanomas compared with nevi. GILT staining in antigen-presenting cells (APCs) was detected in 100% of primary and metastatic melanomas versus 31% of nevi, and it was typically intense. GILT expression was increased in APCs of primary and metastatic melanomas compared with nevi, whereas MHC class II had equivalent high expression in APCs of all melanocytic lesions. GILT staining in keratinocytes was detected in 67% of primary melanomas versus 14% of nevi and 6% of metastatic melanomas. GILT, but not MHC class II, expression was increased in keratinocytes of primary melanomas compared with nevi and metastases. GILT expression is anticipated to result in improved presentation of melanoma antigens and more effective antimelanoma T-cell responses. GILT expression may be a biomarker of immune recognition of melanoma.

Gram Negative Bacterial Inflammation Ameliorated by the Plasma Protein Beta 2-Glycoprotein I

Lipopolysaccharide (LPS) is a major component of the outer wall of gram negative bacteria. In high doses LPS contributes to the inflammation in gram negative sepsis, and in low doses contributes to the low grade inflammation characteristic of the metabolic syndrome. We wanted to assess the role of beta2-glycoprotein I (β2GPI) a highly conserved plasma protein and its different biochemical forms in a mouse model of LPS systemic inflammation. Normal and β2GPI deficient mice were administered LPS through their veins and assessed for a range of inflammation markers in their blood and liver. Different biochemical forms of β2GPI were measured in normal mice given either saline or LPS. We show that β2GPI has a significant role in inhibiting LPS induced inflammation. In this study we provide some evidence that β2GPI serves a protective role in a mouse model of LPS inflammation. This resolves the controversy of previous studies which used LPS and β2GPI in test tube based models of LPS induced activation of white cells. We also highlight the potential relevance of a newly discovered biochemical form of β2GPI in LPS mediated inflammation and we speculate that this form has a protective role against LPS induced pathology.

The first echinoderm gamma-interferon-inducible lysosomal thiol reductase (GILT) identified from sea cucumber (Stichopus monotuberculatus)

Gamma-interferon-inducible lysosomal thiol reductase (GILT) has been described as a key enzyme that facilitating the processing and presentation of major histocompatibility complex class II-restricted antigen in mammals. In this study, the first echinoderm GILT named StmGILT was identified from sea cucumber (Stichopus monotuberculatus). The StmGILT cDNA is 1529 bp in length, containing a 5'-untranslated region (UTR) of 87 bp, a 3'-UTR of 674 bp and an open reading frame (ORF) of 768 bp that encoding a protein of 255 amino acids with a deduced molecular weight of 27.82 kDa and a predicted isoelectric point of 4.73. The putative StmGILT protein possesses all the main characteristics of known GILT proteins, including a signature sequence, a reductase active site CXXC, twelve conserved cysteines, and two potential N-linked glycosylation sites. For the gene structure, StmGILT contains four exons separated by three introns. In the promoter region of StmGILT gene, an NF-κB binding site and an IFN-γ activation site were found. The thiol reductase activity of recombinant StmGILT protein was also demonstrated in this study. In addition, the highest level of mRNA expression was noticed in coelomocytes of S. monotuberculatus. In in vitro experiments performed in coelomocytes, the expression of StmGILT mRNA was significantly up-regulated by lipopolysaccharides (LPS), inactivated bacteria or polyriboinosinic polyribocytidylic acid [poly (I:C)] challenge, suggested that the sea cucumber GILT might play critical roles in the innate immune defending against bacterial and viral infections.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

Identification of gamma-interferon-inducible lysosomal thiol reductase (GILT) homologues in the fruit fly Drosophila melanogaster

Gamma-interferon-inducible lysosomal thiol reductase (GILT) has been demonstrated to be involved in the immune response to bacterial challenge in various organisms. However, little is known about GILT function in innate immunity. Drosophila has been commonly used as a model for the study of the innate immune response of invertebrates. Here, we identify the CG9796, CG10157, and CG13822 genes of fruit fly Drosophila melanogaster as GILT homologues. All deduced Drosophila GILT coding sequences contained the major characteristic features of the GILT protein family: the GILT signature CQHGX2ECX2NX4C sequence and the active site CXXC or CXXS motif. The mRNA transcript levels of the Drosophila GILT genes were up-regulated after Gram-negative bacteria Escherichia coli DH5α infection. Moreover, a bacterial load assay showed that over-expression of Drosophila GILT in fat body or hemocytes led to a low bacterial colony number whereas knock-down of Drosophila GILT in fat body or hemocytes led to a high bacterial colony number when compared to a wild-type control. These results indicate that the Drosophila GILTs are very likely to play a role in the innate immune response upon bacterial challenge of Drosophila host defense. This study may provide the basis for further study on GILT function in innate immunity.

Identification of interferon-γ-inducible-lysosomal thiol reductase (GILT) gene from Mefugu (Takifugu obscures) and its immune response to LPS challenge

Interferon-γ-inducible-lysosomal thiol reductase (GILT) plays a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction. In this study, a Mefugu cDNA (ToGILT) encodes a deduced protein of 242 amino acids with a putative molecular weight of 28.6 kDa. It contains typical features of GILT proteins including the signature sequence CQHGX2ECX2NX4C, CXXC motif and other five cysteines. Genomic analysis revealed that ToGILT gene exhibited a similar exon-intron organization to human and mouse GILT. Phylogenetic analysis showed that ToGILT derived from a common ancestor with other vertebrate GILT proteins. The ToGILT mRNA was expressed in a tissue-specific manner and obviously up-regulated in spleen and kidney after LPS induction. These results suggest that ToGILT may be involved in the immune response to bacteria challenge in Takifugu obscurus.

MicroRNAs responsive to Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis LPS modulate expression of genes regulating innate immunity in human macrophages

MicroRNAs (miRNAs) are a class of small, noncoding RNAs that regulate post-transcriptional expression of their respective target genes and are responsive to various stimuli, including LPS. Here we examined the early (4 h) miRNA responses of THP1-differentiated macrophages challenged with LPS derived from the periodontal pathogens, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis or environmentally-modified LPS obtained from P. gingivalis grown in cigarette smoke extract. Predicted miRNA-gene target interactions for LPS-responsive miR-29b and let-7f were confirmed using dual-luciferase assays and by transfection experiments using miRNA mimics and inhibitors. Convergent and divergent miRNA profiles were observed in treated samples where differences in miRNA levels related to the type, concentration and incubation times of LPS challenge. Dual-luciferase experiments revealed miR-29b targeting of interleukin-6 receptorα (IL-6Rα) and IFN-γ inducible protein 30 and let-7f targeting of suppressor of cytokine signaling 4 and thrombospondin-1. Transfection experiments confirmed miR-29b and let-7f modulation of IL-6Rα and SOCS4 protein expression levels, respectively. Thus, we have demonstrated convergent/divergent miRNA responses to wild type LPS and its environmentally-modified LPS, and demonstrate miRNA targeting of key genes linked to inflammation and immunity. Our data indicate that these LPS-responsive miRNAs may play a key role in fine-tuning the host response to periodontal pathogens.

MHC class II-restricted presentation of the major house dust mite allergen Der p 1 Is GILT-dependent: implications for allergic asthma

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is known to reduce disulfide bonds present in proteins internalized by antigen presenting cells, facilitating optimal processing and presentation of peptides on Major Histocompatibility Complex class II molecules, as well as the subsequent activation of CD4-positive T lymphocytes. Here, we show that GILT is required for class II-restricted processing and presentation of immunodominant epitopes from the major house dust mite allergen Der p 1. In the absence of GILT, CD4-positive T cell responses to Der p 1 are significantly reduced, resulting in mitigated allergic airway inflammation in response to Der p 1 and house dust mite extracts in a murine model of asthma.

Expanding roles for GILT in immunity

Gamma-interferon-inducible lysosomal thiol reductase (GILT), a thioredoxin-related oxidoreductase, functions in MHC class II-restricted antigen processing and MHC class I-restricted cross-presentation by reducing disulfide bonds of endocytosed proteins and facilitating their unfolding and optimal degradation. However, recent reports have greatly expanded our understanding of GILT's function. Several studies of GILT and antigen processing have shown that the influence of GILT on the peptide repertoire can alter the character of the immune response and affect central tolerance. Furthermore, a few unexpected roles for GILT have been uncovered: as a host factor for Listeria monocytogenes infection, in the maintenance of cellular glutathione (GSH) levels, and possibly outside the cell, as enzymatically active GILT is secreted by activated macrophages.

Molecular and biological characterization of interferon-γ-inducible-lysosomal thiol reductase gene in zebrafish (Danio rerio)

In mammals, interferon-γ-inducible-lysosomal thiol reductase (GILT) has been demonstrated to play a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. Here, we reported the cloning of a GILT gene homologue from zebrafish (zGILT), a tropical freshwater fish. The full-length cDNA of zGILT gene is 768 nucleotides (nt) encoding a protein of 255 amino acids (aa), with a putative molecular weight of 28.33 kDa. The deduced protein is highly homologous to that of fish and mammalian GILTs and shares 57.1% sequence identity to that of Atlantic salmon and 55.7-21.6% sequence identity to that of various mammals. The deduced protein possesses all the main features characteristic of known GILT proteins including the signature sequence CQHGX2ECX2NX4C spanning residues 117-132, CXXC motif at residues 72-75, one potential sites for N-linked glycosylation at residual positions 54. The zGILT expression is obviously up-regulated in spleen and kidney after immunization with LPS although it also is constitutively expressed in heart, liver, muscle and intestine, suggesting that zGILT may be involved in the immune response to bacterial challenge. The soluble recombinant protein was successfully purified using Ni-nitrilotriacetic acid resin. Recombinant His-zsGILT appeared on SDS-PAGE in the ranges of their estimated size of 18.94-kDa. After purification, further study revealed that zsGILT was capable of catalyzing the reduction of the interchain disulfide bonds intact IgG. These results will allow for further investigation to unravel the role of this key enzyme in class II MHC-restricted antigen processing and to use zebrafish as an in vivo model for related studies.

Transcriptional regulation of IL-17A and other inflammatory markers during the development of soybean meal-induced enteropathy in the distal intestine of Atlantic salmon (Salmo salar L.)

Progression of soybean meal (SBM)-induced enteropathy in Atlantic salmon (Salmo salar L.) distal intestine (DI) was studied to investigate pathophysiological mechanisms and immune responses. Seawater-adapted salmon were fed an extracted SBM-containing diet (200 g kg(-1)) from day 1-21 and compared with fish fed a fishmeal-based diet (day 0). Histological evaluation of the DI revealed signs of inflammation from day 5, which progressively increased in severity and affected more fish with increasing SBM exposure time. The expression profiles of 16 genes were analyzed by quantitative PCR. The pro-inflammatory cytokines interleukin 17A (IL-17A), IL-1β, interferon α (IFNα) and IFNγ, as well as IL-17A receptor, T-cell receptor γ (TCRγ), cluster of differentiation 4α (CD4α), CD8β, transforming growth factor β (TGFβ), trypsin, protease-activated receptor 2 (PAR2) and myeloid differentiation primary response gene 88 (MyD88) were significantly up-regulated during early and/or late inflammation stages, whereas interferon-γ-inducible lysosomal thiol reductase (GILT) was downregulated. Up-regulation of TCRγ from day seven suggests proliferation of intraepithelial γδ T cells. IL-17A, up-regulated by 218-fold during early inflammation, indicates involvement of T helper 17 cells in the pathogenesis of the SBM-induced inflammatory response.

Genetic contribution to C-reactive protein levels in severe obesity

Obese individuals are characterized by a chronic, low-grade inflammatory state. Increased levels of C-reactive protein (CRP), a marker of inflammation, have been observed in subjects with the metabolic syndrome. We have previously reported that genes encoding proteins involved in the anti-inflammatory and immune response are differentially expressed in visceral adipose tissue of obese men with or without the metabolic syndrome. Among these genes, the interferon-gamma-inducible protein 30 (IFI30), CD163 molecule (CD163), chemokine (C-X-C motif) ligand 9 (CXCL9) and thymic stromal lymphopoietin (TSLP), were selected for further genetic analyses. The aim of the study was to verify whether IFI30, CD163, CXCL9 and TSLP gene polymorphisms contribute to explain the inter-individual variability of the inflammatory profile of obesity assessed by plasma high-sensitivity CRP concentrations. A total of 1185 severely obese individuals were genotyped for single nucleotide polymorphisms (SNPs) covering most of the sequence-derived genetic variability at the IFI30, CD163, CXCL9 and TSLP gene loci (total of 27 SNPs). Following measurement of plasma CRP levels, subjects were divided into two groups, low vs. high using the median value of plasma CRP levels (8.31 mg/L) as a cutoff point. Genotype frequencies were compared between groups. Associations between genotypes and plasma CRP levels (continuous variable) were also tested after adjustments for age, sex, smoking and BMI. The rs11554159 and rs7125 IFI30 SNPs showed a significant difference in genotype frequencies (p<0.05) between subgroups of low vs. high plasma CRP levels (wild type homozygotes: rs11554159=47% vs. 55%, rs7125=31% vs. 24%, for low vs. high CRP groups, respectively). The association between rs11554159 and CRP levels as a continuous variable remained significant (p=0.004). Both carriers of the GA and AA genotypes demonstrated, on average, a 13% lower CRP levels in comparison with GG homozygotes. No association was observed between SNPs in the CD163, CXCL9 and TSLP genes and CRP levels. The IFI30 rs11554159 polymorphism could partially explain the inter-individual variability observed in the inflammatory profile associated with obesity.

Labile disulfide bonds are common at the leucocyte cell surface

Redox conditions change in events such as immune and platelet activation, and during viral infection, but the biochemical consequences are not well characterized. There is evidence that some disulfide bonds in membrane proteins are labile while others that are probably structurally important are not exposed at the protein surface. We have developed a proteomic/mass spectrometry method to screen for and identify non-structural, redox-labile disulfide bonds in leucocyte cell-surface proteins. These labile disulfide bonds are common, with several classes of proteins being identified and around 30 membrane proteins regularly identified under different reducing conditions including using enzymes such as thioredoxin. The proteins identified include integrins, receptors, transporters and cell-cell recognition proteins. In many cases, at least one cysteine residue was identified by mass spectrometry as being modified by the reduction process. In some cases, functional changes are predicted (e.g. in integrins and cytokine receptors) but the scale of molecular changes in membrane proteins observed suggests that widespread effects are likely on many different types of proteins including enzymes, adhesion proteins and transporters. The results imply that membrane protein activity is being modulated by a 'redox regulator' mechanism.

Disulfide reduction in the endocytic pathway: immunological functions of gamma-interferon-inducible lysosomal thiol reductase

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is constitutively expressed in most antigen presenting cells and is interferon γ inducible in other cell types via signal transducer and activator of transcription 1. Normally, N- and C-terminal propeptides are cleaved in the early endosome, and the mature protein resides in late endosomes and lysosomes. Correspondingly, GILT has maximal reductase activity at an acidic pH. Monocyte differentiation via Toll-like receptor 4 triggers secretion of a disulfide-linked dimer of the enzymatically active precursor, which may contribute to inflammation. GILT facilitates major histocompatibility complex (MHC) class II-restricted processing through reduction of protein disulfide bonds in the endocytic pathway and is hypothesized to expose buried epitopes for MHC class II binding. GILT can also facilitate the transfer of disulfide-containing antigens into the cytosol, enhancing their cross-presentation by MHC class I. A variety of antigens are strongly influenced by GILT-mediated reduction, including hen egg lysozyme, melanocyte differentiation antigens, and viral envelope glycoproteins. In addition, GILT is conserved among lower eukaryotes and likely has additional functions. For example, GILT expression increases the stability of superoxide dismutase 2 and decreases reactive oxygen species, which correlates with decreased cellular proliferation. It is also a critical host factor for infection with Listeria monocytogenes.

Molecular structure, phylogenetic analysis, tissue distribution, and function characterization of interferon-γ-inducible lysosomal thiol reductase (GILT) gene in sheep (Ovis aries)

Interferon-γ-inducible-lysosomal thiol reductase (GILT) plays a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction. In this study, a sheep cDNA, sGILT, encoding GILT protein was isolated from the spleen cDNA library of Ovis aries. It codes for a deduced protein of 244 amino acids with a putative molecular weight of 27.6 kDa, which has all the typical structural features of GILT protein including an active-site CXXC motif, a GILT signature sequence CQHGX(2)ECX(2)NX(4)C, and 5 conserved cysteines. Sequence comparison indicated the amino acid sequence of sGILT showed high identity to cow GILT (93.03%). Phylogenetic analysis showed that sGILT and cow GILT shared the greatest homology. The result of real-time PCR suggested that sGILT mRNA was expressed in a tissue-specific manner and obviously up-regulated in splenocytes and PBMCs after induction with lipopolysaccharide (LPS). Recombinant sGILT fused with His(6) tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. Its expression was confirmed by SDS-PAGE and Western blotting analysis. Thiol reductase activity was assessed using antibody as the substrate. These results suggest that sGILT has the activity of disulfide bond reduction and indicate that sheep also express a protein that has been found to maintain first line of innate immune defense at basal level.

Molecular characterization and expression analysis of interferon-gamma-inducible lysosomal thiol reductase (GILT) gene from pearl oyster Pinctada fucata

Interferon-gamma-inducible lysosomal thiol reductase (GILT) is an important thiol reductase, involved in class, MHC-restricted antigen processing by catalyzing disulfide bond reduction in mammals. Herein, we describe the identification and characterization of pearl oyster Pinctada fucata GILT (designated as poGILT). The poGILT cDNA was 1273bp long and consisted of a 5'-untranslated region (UTR) of 24bp, a 3'-UTR of 484bp with two cytokine RNA instability motifs (ATTTA), and an open reading frame (ORF) of 765bp encoding a polypeptide of 254 amino acids with an estimated molecular mass of 28.9kDa and a theoretical isoelectric point of 7.4. The N-terminus of the poGILT was found to have a putative signal peptide with a cleavage site amino acid position at 19-20. SMART analysis showed that the poGILT contained a GILT active-site C(69)PDC(72) motif and a GILT signature motif C(115)QHGKEECIGNLIETC(130). Homology analysis of the deduced amino acid sequence of the poGILT with other known GILT sequences by MatGAT software revealed that the poGILT shared 42.9-67.3% similarity and 22.9-49.8% identity to the other known GILT sequences. The expression level of poGILT mRNA was higher in digestive gland, moderate in adductor muscle, gills, gonad, intestine and mantle, and lower in hemocytes. The poGILT mRNA expression was significantly up-regulated in gill and digestive gland after LPS or V. alginolyticus stimulation, respectively. These results suggested that the poGILT was a constitutively expressed acute-phase protein, the expression of which can be enhanced after LPS or V. algrinolyticus stimulation, perhaps involved in the innate immune response of pearl oyster.

Functional significance of tapasin membrane association and disulfide linkage to ERp57 in MHC class I presentation

Tapasin is disulfide linked to ERp57 within the peptide loading complex. In cell-free assays, a soluble variant of the tapasin/ERp57 dimer recruits MHC class I molecules and promotes peptide binding to them, whereas soluble tapasin alone does not. Here we show that within cells, tapasin conjugation with ERp57 is as critical as its integration into the membrane for efficient MHC class I assembly, surface expression, and Ag presentation to CD8(+) T cells. Elimination of both of these properties severely compromises tapasin function, in keeping with predictions from in vitro studies.

Decreased expression of TGF-beta, GILT and T-cell markers in the early stages of soybean enteropathy in Atlantic salmon (Salmo salar L.)

This study investigated the early expression of T-cell markers and genes potentially involved in the induction of soybean meal (SBM) enteropathy in the distal intestine (DI) of Atlantic salmon (Salmo salar L.). Quantitative PCR was used to study the expression of CD3, CD8beta, transforming growth factor beta (TGF-beta), interferon-gamma-inducible lysosomal thiol reductase (GILT) and interleukin-1beta (IL-1beta) in salmon fed SBM for 1, 3 and 7 days using fish fed fishmeal as controls. In the same tissue, the morphological development of SBM enteropathy was evaluated by routine histology and the presence of T cells was mapped by immunohistochemistry. TGF-beta was significantly down-regulated on all days of feeding SBM. GILT was significantly down-regulated on days 3 and 7 compared to day 1. A depression in the expression of T-cell markers was observed on day 3 whereas increased densities of T cells were observed at the base of mucosal folds after 7 days of feeding SBM. Down-regulation of GILT and TGF-beta may lead to sensitization of intraepithelial lymphocytes and failure to maintain normal mucosal integrity in the DI. These responses are implicated in the pathogenesis of SBM enteropathy in Atlantic salmon.

GILT is a critical host factor for Listeria monocytogenes infection

Listeria monocytogenes is a gram positive, intracellular, food-borne pathogen that can cause severe illness in humans and animals. Upon infection, it is actively phagocytosed by macrophages1. It then escapes from the phagosome, replicates in the cytosol, and subsequently spreads from cell to cell by a non-lytic mechanism driven by actin polymerization2. Penetration of the phagosomal membrane is initiated by the secreted hemolysin listeriolysin O (LLO), which is essential for vacuolar escape in vitro and for virulence in animal models of infection3. Reduction is required to activate the lytic activity of LLO in vitro4–6, and we show here that reduction by the enzyme Gamma-interferon Inducible Lysosomal Thiolreductase (GILT) is responsible for the activation of LLO in vivo. GILT is a soluble thiol reductase expressed constitutively within the lysosomes of antigen presenting cells7, 8, and it accumulates in macrophage phagosomes as they mature into phagolysosomes9. The enzyme is delivered by a mannose-6-phosphate receptor-dependent mechanism to the endocytic pathway, where N- and C-terminal pro-peptides are cleaved to generate a 30 kDa mature enzyme7, 8, 10. The active site of GILT contains two cysteine residues in a CXXC motif that catalyzes the reduction of disulfide bonds7, 8. Mice lacking GILT are deficient in generating MHC class II-restricted CD4⁺ T cell responses to protein antigens that contain disulfide bonds11, 12. Here we show that these mice are resistant to L. monocytogenes infection. Replication of the organism in GILT-negative macrophages, or macrophages expressing an enzymatically inactive GILT mutant, is impaired because of delayed escape from the phagosome. GILT activates LLO within the phagosome by the classical thiol reductase mechanism shared by members of the thioredoxin family. In addition, purified GILT activates recombinant LLO, facilitating membrane permeabilization and red blood cell lysis. The data show GILT is a critical host factor that facilitates L. monocytogenes infection.

B cells induce tolerance by presenting endogenous peptide-IgG on MHC class II molecules via an IFN-gamma-inducible lysosomal thiol reductase-dependent pathway

We have previously demonstrated that splenic B cells, transduced with peptide-IgG fusion proteins, are efficient tolerogenic APCs in vivo. Specific hyporesponsiveness to epitopes encoded in the peptide-IgG fusion protein has been achieved to over one dozen Ags, and clinical efficacy has been established in animal models for several autoimmune diseases and hemophilia. Previous studies also demonstrated that tolerance in this system requires MHC class II expression by the transduced B cells. Yet, the mechanisms of this B cell tolerogenic processing pathway remain unclear. In this study, we show that MHC class II molecules on tolerogenic B cells present epitopes derived from endogenous, but not exogenous (secreted), peptide-IgG fusion protein. These class II epitopes from the IgG fusion protein are processed in lysosomes/endosomes in an IFN-gamma-inducible lysosomal thiol reductase-dependent manner. We suggest that the MHC class II presentation of endogenously produced fusion protein epitopes represents a novel mechanism for tolerance induced by peptide-IgG-transduced B cells. An understanding of this process might provide insights into central and peripheral tolerance induced by other professional and nonprofessional APCs.

The redox activity of ERp57 is not essential for its functions in MHC class I peptide loading

ERp57 is an oxidoreductase that, in conjunction with calnexin and calreticulin, assists disulfide bond formation in folding glycoproteins. ERp57 also forms a mixed disulfide with the MHC class I-specific chaperone tapasin, and this dimeric conjugate edits the peptide repertoire bound by MHC class I molecules. In cells unable to form the conjugate, because of tapasin mutation in human studies or ERp57 deletion in mouse studies, peptide loading is impeded. Subtle differences between the mouse and human systems have been observed. Here, we address these differences and expand the analysis to investigate the role of ERp57 redox functions in MHC class I peptide loading. We show in human cells that in the absence of conjugate formation MHC class I recruitment and/or stabilization in the MHC class I peptide-loading complex is impaired, similar to observations in mouse cells. However, we found no role for the enzymatic activities of either the a or a' domain redox sites of ERp57 in peptide loading. Our data argue that the function of ERp57 in peptide loading is likely caused by other ERp57 functional domains or a combinatorial feature of the tapasin-ERp57 conjugate.

Neuromyelitis optica/Devic's disease: gene expression profiling of brain lesions

Neuromyelitis optica (NMO), also known as Devic's disease, is an inflammatory demyelinating disease that affects selectively the optic nerves and the spinal cord, possibly mediated by an immune mechanism distinct from that of multiple sclerosis (MS). Recent studies indicate that NMO also involves the brain. Here, we studied gene expression profile of brain lesions of a patient with NMO by using DNA microarray, along with gene expression profile of the brains of Parkinson disease and amyotrophic lateral sclerosis patients. We identified more than 200 genes up-regulated in NMO brain lesions. The top 20 genes were composed of the molecules closely associated with immune regulation, among which marked up-regulation of interferon gamma-inducible protein 30 (IFI30), CD163, and secreted phosphoprotein 1 (SPP1, osteopontin) was validated by real time RT-PCR, Northern blot and Western blot analysis. Pathologically, CD68(+) macrophages and microglia expressed intense immunoreactivities for IFI30 and CD163 in NMO lesions, consisting of inflammatory demyelination, axonal loss, necrosis, cavity formation, and vascular fibrosis. KeyMolnet, a bioinformatics tool for analyzing molecular interaction on the curated knowledge database, suggested that the molecular network of up-regulated genes in NMO brain lesions involves transcriptional regulation by the nuclear factor-kappaB (NF-kappaB) and B-lymphocyte-induced maturation protein-1 (Blimp-1). These results suggest that profound activation of the macrophage-mediated proinflammatory immune mechanism plays a pivotal role in development of NMO brain lesions.

Predominant release of lysosomal enzymes by newborn rat microglia after LPS treatment revealed by proteomic studies

Growing evidence suggest that microglia may play an important role in the pathogenesis of neurodegenerative disease including Parkinson's disease, Alzheimer's disease, and so forth. The activation of microglia may cause neuronal damage through the release of reactive oxygen species and proinflammatory cytokines. However, the early response of microglial cells remains unclear before cells can secrete the proinflammatory cytokines. Here, a time course analysis showed the earliest expression of inducible nitric oxide synthase and cyclooxygenase-2 at 3 and 24 h following lipopolysaccharide (LPS) treatment. To further define initial response proteins of microglia after LPS treatment, we utilized a novel mass spectrometry-based quantitative proteomic technique termed SILAC (for stable isotope labeling by amino acids in cell culture) to compare the protein profiles of the cell culture-conditioned media of 1 h LPS-treated microglia as compared with controls. The proteomic analysis identified 77 secreted proteins using SignalP; of these, 28 proteins were associated with lysosome of cells and 13 lysosome-related proteins displayed significant changes in the relative abundance after 1 h LPS treatment. Four proteins were further evaluated with Western blot, demonstrating good agreement with quantitative proteomic data. These results suggested that microglia first released some lysosomal enzymes which may be involved in neuronal damage process. Furthermore, ammonium chloride, which inhibits microglia lysosomal enzyme activity, could prevent microglia from causing neuronal injury. Hence, in addition to the numerous novel proteins that are potentially important in microglial activation-mediated neurodegeneration revealed by the search, the study has indicated that the early release of lysosomal enzymes in microglial cells would contribute to LPS-activated inflammatory response.

The grateful dead: damage-associated molecular pattern molecules and reduction/oxidation regulate immunity

The response to pathogens and damage in plants and animals involves a series of carefully orchestrated, highly evolved, molecular mechanisms resulting in pathogen resistance and wound healing. In metazoans, damage- or pathogen-associated molecular pattern molecules (DAMPs, PAMPs) execute precise intracellular tasks and are also able to exert disparate functions when released into the extracellular space. The emergent consequence for both inflammation and wound healing of the abnormal extracellular persistence of these factors may underlie many clinical disorders. DAMPs/PAMPs are recognized by hereditable receptors including the Toll-like receptors, the NOD1-like receptors and retinoic-acid-inducible gene I-like receptors, as well as the receptor for advanced glycation end products. These host molecules 'sense' not only pathogens but also misfolded/glycated proteins or exposed hydrophobic portions of molecules, activating intracellular cascades that lead to an inflammatory response. Equally important are means to not only respond to these molecules but also to eradicate them. We have speculated that their destruction through oxidative mechanisms normally exerted by myeloid cells, such as neutrophils and eosinophils, or their persistence in the setting of pathologic extracellular reducing environments, maintained by exuberant necrotic cell death and/or oxidoreductases, represent important molecular means enabling chronic inflammatory states.

Molecular cloning and expression analysis of interferon-gamma-inducible-lysosomal thiol reductase gene in orange-spotted grouper, Epinephelus coioides

In mammals, interferon-gamma-inducible-lysosomal thiol reductase (GILT) has been demonstrated to play a key role in the processing and presentation of MHC class II-restricted antigen (Ag) by catalyzing disulfide bond reduction, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. In this study a cDNA containing the orange-spotted grouper GILT (OsgGILT) coding sequence has been cloned and its complete sequence determined. The full-length cDNA of OsgGILT gene is 1066 bp nucleotides (nt) encoding a protein of 260 amino acids (aa), with a putative molecular weight of 28.7 kDa. The deduced OsgGILT possesses the typical structural feature of mammalian GILT, including an active-site CXXC motif, a GILT signature sequence CQHGX(2)ECX(2)NX(4)C, and 10 conserved cysteines. The result of real-time PCR showed that OsgGILT mRNA was expressed in heart, liver, brain, gill, kidney and muscle and more highly expressed in spleen. The OsgGILT expression is obviously up-regulated in spleen and kidney after induction with LPS, these results suggest that OsgGILT may be involved in the immune response to LPS challenge in orange-spotted grouper.

Molecular cloning and expression analysis of interferon-γ inducible lysosomal thiol reductase (GILT)-like cDNA from disk abalone (Haliotis discus discus)

Interferon Gamma (IFN-gamma) Inducible Lysosomal Thiol reductase (GILT) has been described as a key enzyme in processing and presentation of major histocompatibility complex (MHC) class II restricted antigen (Ag) by catalyzing disulfide bond (S-S) reduction in mammals. Abalone GILT-like (AbGILT) full-length cDNA was isolated from the normalized disk abalone cDNA library. The 807-bp AbGILT cDNA consists of an open reading frame of 684-bp, encoding 228 amino acid residues. The predicted AbGILT protein has a molecular weight of 25kDa and an isoelectric point of 7.8. The N-terminus of the AbGILT was found to have a putative signal peptide with a cleavage site amino acid position at 19-20. AbGILT contains two active site C-XX-C motifs, ((23)CLDC(26) and (46)CPYC(49)) which motif is highly conserved in GILT protein family. AbGILT exhibited a characteristic GILT signature sequence (92)CQHGX(2)ECX(2)NX(4)C(107) and 12 cysteine residues representing 5% in the mature peptide. Phylogenetic analysis showed that AbGILT has been derived from a common ancestor with other GILT proteins. RT-PCR results showed that AbGILT expression was up-regulated in the gill, mantle and digestive tract 24h post injection of phytohemagglutinin (PHA) while Vibrio alginolyticus up-regulation appeared in the gill and digestive tract after 48h. In contrast, AbGILT expression was not up-regulated by poly inosinic-cytidylic acid (poly I:C) during the 48h induction. However, AbGILT was constitutively expressed in gill, mantle, and digestive tract tissues suggesting that it may maintain first line of innate immune defense at basal level in disk abalone.