Characterization and expression of gamma-interferon-inducible lysosomal thiol reductase (GILT) gene in rainbow trout (Oncorhynchus mykiss) with implications for GILT in innate immune response

mosGILT controls innate immunity and germ cell development in Anopheles gambiae

Gene-edited mosquitoes lacking a gamma-interferon-inducible lysosomal thiol reductase-like protein, namely (mosGILTnull) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILTnull Anopheles gambiae was therefore compared to wild type (WT) mosquitoes by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILTnull A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg, an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILTnull mosquitoes. These results provide a crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

Functional of tongue sole (Cynoglossus semilaevis) gamma-interferon-inducible lysosomal thiol reductase with implications in innate immune reponse depend on CXXC active site

The enzyme gamma-interferon-inducible lysosomal thiol reductase (GILT) plays an important role in promoting the processing and presentation of major histocompatibility complex (MHC) class II-restricted antigens. It is also involved in MHC I-restricted antigens catalyzing disulfide bond reduction in fishes' adaptive immunity. The open reading frame of tongue sole (Cynoglossus semilaevis) GILT (tsGILT) gene is 771 bp long, encoding 257 amino acids, with a calculated molecular weight of 28.465 kDa and isoelectric point (pI) of 5.35. After induction with lipopolysaccharide, the expression of tsGILT mRNA was upregulated in spleen and kidney and recombinant tsGILT protein transferred to late endosomes and lysosomes in HeLa cells. The refolded tsGILT was capable of catalyzing the reduction of the interchain disulfide bonds against an IgG substrate depend on the active site CXXC motif at residues 75-78. The process of immune response to bacteria challenge needs GILT to catalyze the reduction of disulfide bond and unfolding native protein antigens, promoting their hydrolysis by proteases. Whether a single mutation or a double mutation of active site CXXC at residues75-78, the 3D structure of tsGILT protein has undergone major changes and lost its activity of catalyzing the reduction of the interchain disulfide bonds.

Anopheles gambiae mosGILT regulates innate immune genes and zpg expression

Gene-edited mosquitoes lacking a g amma-interferon-inducible lysosomal thiol reductase-like protein, namely ( mosGILT null ) have lower Plasmodium infection, which is linked to impaired ovarian development and immune activation. The transcriptome of mosGILT null A. gambiae was therefore compared to wild type (WT) by RNA-sequencing to delineate mosGILT-dependent pathways. Compared to WT mosquitoes, mosGILT null A. gambiae demonstrated altered expression of genes related to oogenesis, 20-hydroxyecdysone synthesis, as well as immune-related genes. Serendipitously, the zero population growth gene, zpg , an essential regulator of germ cell development was found to be one of the most downregulated genes in mosGILT null mosquitoes. These results provide the crucial missing link between two previous studies on the role of zpg and mosGILT in ovarian development. This study further demonstrates that mosGILT has the potential to serve as a target for the biological control of mosquito vectors and to influence the Plasmodium life cycle within the vector.

Immune Response of Senegalese Sole against Betanodavirus Mutants with Modified Virulence

Nervous necrosis virus (NNV), genus Betanodavirus, the etiological agent of the viral encephalopathy and retinopathy (VER), presents a genome with two positive-sense single-stranded RNA segments. Striped jack nervous necrosis virus (SJNNV) and red-spotted grouper nervous necrosis virus (RGNNV), together with reassortants RGNNV/SJNNV, are the betanodaviruses predominantly isolated in Southern Europe. An RGNNV/SJNNV reassortant isolated from Senegalese sole (wt160) causes high mortalities in this fish species. This virus presents differences in the sequence of the 3’ non-coding region (NCR) of both segments compared to RGNNV and SJNNV reference strains. Previously, it has been reported that the reversion of two of these differences (nucleotides 1408 and 1412) in the RNA2 3’NCR to the SJNNV-type (recombinant r1408-1412) resulted in a decrease in sole mortality. In the present study, we have applied an OpenArray^® to analyse the involvement of sole immune response in the virulence of several recombinants: the r1408-1412 and two recombinants, developed in the present study, harbouring mutations at positions 3073 and 3093 of RNA1 3’NCR to revert them to RGNNV-type. According to the correlation values and to the number of expressed genes, the infection with the RNA2-mutant provoked the most different immune response compared to the immune response triggered after the infection with the rest of the viruses, and the exclusive and high upregulation of genes related to the complement system. The infection with the RNA1-mutants also provoked a decrease in mortality and their replication was delayed at least 24 h compared to the wt160 replication, which could provoke the lag observed in the immune response. Furthermore, the infection with the RNA1-mutants provoked the exclusive expression of pkr and the downregulation of il17rc.

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.

Molecular and biological characterization of gamma-interferon-inducible lysosomal thiol reductase in silver carp (Hypophthalmichthys molitrix)

Gamma-interferon-inducible lysosomal thiol reductase (GILT) plays an important role in the processing of major histocompatibility complex (MHC) class II-restricted antigens by catalyzing disulfide bonds reduction. Herein, a GILT homolog (ScGILT) was identified from silver carp. Its open reading frame covers 771 base pairs, encoding a protein of 256 amino acids that possesses GILT signature sequence CQHGX₂ECX₂NX₄C, active-site CXXC motif, and two potential N-linked glycosylation sites. The predicted tertiary structures of ScGILT and other GILTs were quite similar in shape and positional arrangement of the key motifs. ScGILT mRNA was constitutively expressed in all detected tissues, with high-level expression in fish immune organs, spleen and head kidney. After stimulation with lipopolysaccharide, the expression of ScGILT mRNA significantly increased in spleen and head kidney cells, and ScGILT protein translocated to late endosomes and lysosomes in HeLa cells. Recombinant ScGILT fused with a His₆ tag was expressed and purified, and could reduce the interchain disulfide bonds of IgG at pH 4.5. These results suggested that ScGILT was capable of catalyzing disulfide bonds reduction, and then might play an important role in the processing of MHC class II-restricted antigens in silver carp.

Genomic structure, expression pattern and polymorphisms of GILT in golden pompano Trachinotus ovatus (Linnaeus 1758)

The interferon-g-inducible lysosomal thiol reductase (GILT) plays a significant character in the processing and presentation of MHC class II restricted antigen (Ag) by catalyzing disulfide bond reduction in mammals. To explore the function of GILT in the immune system of fish, we cloned a GILT gene homologue from Trachinotus ovatus, the full-length cDNA of GILT, which consisted of 2, 747 bp with a 771 bp open reading frame, encoding a protein of 256 amino acids. Moreover, similar to other species GILT gene, 7 exons and 6 introns were identified in T. ovatus, the deduced protein also possessed a representative characteristic of known GILT proteins. The result of real-time quantitative PCR showed that GILT mRNA was dramatically expressed in immune-associated tissues, such as spleen (p < 0.01) and kidney (p < 0.05). Bacterial challenge revealed that GILT mRNA level remarkably up-regulation in liver, spleen, kidney and intestine after induction with Photobacterium damsela. Furthermore, based on cloned sequences and genome BLAST, only one SNP site (ToGILT-S1-g.148C>G) was identified, and the allele C was significantly associated with high-susceptibility (HS) group, nevertheless, the allele G was dramatically associated with high-resistance (HR) group, indicating potential application for disease resistant breeding selection in T. ovatus.

Molecular structure and functional characterization of the gamma-interferon-inducible lysosomal thiol reductase (GILT) gene in largemouth bass (Microptenus salmoides)

The enzyme gamma-interferon-inducible lysosomal thiol reductase (GILT) plays a role in facilitating the processing and presentation of major histocompatibility complex (MHC) class II-restricted antigens and is also involved in MHC I-restricted antigens in adaptive immunity catalyzing disulfide bond reduction in mammals. In this study, we cloned a GILT gene homolog from largemouth bass (designated 'lbGILT'), a freshwater fish belonging to Perciformes and known for its nutritive value. We obtained the full-length cDNA of lbGILT by reverse transcription PCR and rapid amplification of cDNA ends. This cDNA is comprised of a 5'-untranslated region (UTR) of 87 bp, a 3'-UTR of 189 bp, and an open reading frame of 771 bp. It encodes a protein of 256 amino acids with a deduced molecular weight of 28.548 kDa and a predicted isoelectric point of 5.62. The deduced protein possesses the typical structural features of known GILTs, including an active site motif, two potential N-linked glycosylation sites, a GILT signature sequence, and six conserved cysteines. Tissue-specific expression of lbGILT was shown by real-time quantitative PCR. The expression of lbGILT mRNA was obviously up regulated in spleen and kidney after induction with lipopolysaccharide. Recombinant lbGILT was produced as an inclusion body with a His6 tag in ArcticExpress (DE3), and the protein was then washed, solubilized, and refolded. The refolded lbGILT showed reduction activity against an IgG substrate. These results suggest that lbGILT plays a role in innate immunity.

Identification of interferon-γ-inducible-lysosomal thiol reductase (GILT) gene in goldfish (Carassius auratus) and its immune response to LPS challenge

The interferon-γ-inducible lysosomal thiol reductase (GILT) has been demonstrated to play an important role in the processing and presentation of MHC class II restricted antigen (Ag) by catalyzing disulfide bond reduction. In this study, we cloned a GILT gene homolog from goldfish (designated gGILT), a kind of precious freshwater fish with high market value. The open reading frame of gGILT consists of 756 bases encoding a protein of 251 amino acids with an estimated molecular mass of 27.8 kDa and a theoretical isoelectric point of 5.24. The deduced protein possesses the typical structural features of known GILT proteins, including an active-site motif, a GILT signature sequence, and 10 conserved cysteines. RT-PCR results showed that gGILT and gIFN-γ (goldfish IFN-γ) mRNA were expressed in a tissue-specific manner and obviously up-regulated in splenocytes and the cells from head kidney after induction with LPS. Recombinant gGILT fused with His6 tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. Further study revealed that gGILT was capable of catalyzing the reduction of the interchain disulfide bonds from intact IgG. This study shows that gGILT may be involved in the immune response to bacteria challenge and maintain first line of innate immune defense at basal level in goldfish. It also provides the basis for investigating on the role of GILT using goldfish as an animal model.

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.

Molecular cloning, expression and functional characterization of interferon-γ-inducible lysosomal thiol reductase (GILT) gene from mandarin fish (Siniperca chuatsi)

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, thus unfolding native protein Ag and facilitating subsequent cleavage by proteases. For this important function in the immune system, we cloned a GILT gene homologue from mandarin fish (designated mGILT), a kind of precious freshwater fish with high market value. Through reverse transcription PCR and rapid amplification of cDNA ends (RACE) strategies, we obtained the full-length cDNA of mGILT, which consists of 1008 bp with a 771 bp open reading frame, encoding a protein of 256 amino acids, with a putative molecular weight of 28.47 kDa. The deduced protein possesses the typical structural features of known GILT proteins, including an active-site motif, a GILT signature sequence, and 6 conserved cysteines. The result of real-time quantitative PCR showed that mGILT mRNA was expressed in a tissue-specific manner. In addition, the expression of mGILT mRNA was obviously up-regulated in splenocytes and kidney after induction with lipopolysaccharide (LPS). Recombinant mGILT fused with His6 tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified using Ni-nitrilotriacetic acid resin. Further study revealed that mGILT exhibit thiol reductase activity on IgG substrate. These results suggest mGILT is highly likely to play a role in the immune responses in mandarin fish.