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

Study of Cytotoxicity and Internalization of Redox-Responsive Iron Oxide Nanoparticles on PC-3 and 4T1 Cancer Cell Lines

Redox-responsive and magnetic nanomaterials are widely used in tumor treatment separately, and while the application of their combined functionalities is perspective, exactly how such synergistic effects can be implemented is still unclear. This report investigates the internalization dynamics of magnetic redox-responsive nanoparticles (MNP-SS) and their cytotoxicity toward PC-3 and 4T1 cell lines. It is shown that MNP-SS synthesized by covalent grafting of polyethylene glycol (PEG) on the magnetic nanoparticle (MNP) surface via SS-bonds lose their colloidal stability and aggregate fully in a solution containing DTT, and partially in conditioned media, whereas the PEGylated MNP (MNP-PEG) without S-S linker control remains stable under the same conditions. Internalized MNP-SS lose the PEG shell more quickly, causing enhanced magnetic core dissolution and thus increased toxicity. This was confirmed by fluorescence microscopy using MNP-SS dual-labeled by Cy3 via labile disulfide, and Cy5 via a rigid linker. The dyes demonstrated a significant difference in fluorescence dynamics and intensity. Additionally, MNP-SS demonstrate quicker cellular uptake compared to MNP-PEG, as confirmed by TEM analysis. The combination of disulfide bonds, leading to faster dissolution of the iron oxide core, and the high-oxidative potential Fe³⁺ ions can synergically enhance oxidative stress in comparison with more stable coating without SS-bonds in the case of MNP-PEG. It decreases the cancer cell viability, especially for the 4T1, which is known for being sensitive to ferroptosis-triggering factors. In this work, we have shown the effect of redox-responsive grafting of the MNP surface as a key factor affecting MNP-internalization rate and dissolution with the release of iron ions inside cancer cells. This kind of synergistic effect is described for the first time and can be used not only in combination with drug delivery, but also in treatment of tumors responsive to ferroptosis.

Antivirus activity, but not thiolreductase activity, is conserved in interferon-gamma-inducible GILT protein in arthropod

We have previously reported that gamma-interferon inducible lysosomal thiolreductase (GILT) functions as a host defense factor against retroviruses by digesting disulfide bonds on viral envelope proteins. GILT is widely conserved even in plants and fungi as well as animals. The thiolreductase active site of mammalian GILT is composed of a CXXC amino acid motif, whereas the C-terminal cysteine residue is changed to serine in arthropods including shrimps, crabs, and flies. GILT from Penaeus monodon (PmGILT) also has the CXXS motif instead of the CXXC active site. We demonstrate here that a human GILT mutant (GILT C75S) with the CXXS motif and PmGILT significantly inhibit amphotropic murine leukemia virus vector infection in human cells without alterning its expression level and lysosomal localization, showing that the C-terminal cysteine residue of the active site is not required for the antiviral activity. We have reported that human GILT suppresses HIV-1 particle production by digestion of disulfide bonds on CD63. However, GILT C75S mutant and PmGILT did not digest CD63 disulfide bonds, and had no effect on HIV-1 virion production, suggesting that they do not have thiolreductase activity. Taken together, this study found that antiviral activity, but not thiolreductase activity, is conserved in arthropod GILT proteins. This finding provides a new insight that the common function of GILT is antiviral activity in many animals.

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.

Redox-Responsive Polysulfide-Based Biodegradable Organosilica Nanoparticles for Delivery of Bioactive Agents

Design and development of silica nanoparticles (SiO2 NPs) with a controlled degradation profile promises effective drug delivery with a predetermined carrier elimination profile. In this research, we fabricated a series of redox-responsive polysulfide-based biodegradable SiO2 NPs with low polydispersity and with variations in size (average diameters of 58 ± 7, 108 ± 11, 110 ± 9, 124 ± 9, and 332 ± 6 nm), porosity, and composition (disulfide vs tetrasulfide bonds). The degradation kinetics of the nanoparticles was analyzed in the presence of 8 mM glutathione (GSH), mimicking the intracellular reducing condition. Results indicate that porosity and core composition play the predominant roles in the degradation rate of these nanoparticles. The 108 nm mesoporous disulfide-based nanoparticles showed the highest degradation rate among all the synthesized nanoparticles. Transmission electron microscopy (TEM) reveals that nonporous nanoparticles undergo surface erosion, while porous nanoparticles undergo both surface and bulk erosion under reducing environment. The cytotoxicity of these nanoparticles in RAW 264.7 macrophages was evaluated. Results show that all these nanoparticles with the IC50 values ranging from 233 ± 42 to 705 ± 17 μg mL-1 do not have cytotoxic effect in macrophages at concentrations less than 125 μg mL-1. The degradation products of these nanoparticles collected within 15 days did not show cytotoxicity in the same macrophage cell line after 24 h of incubation. In vitro doxorubicin (DOX) release was examined in 108 nm mesoporous disulfide-based nanoparticles in the absence and presence of 8 mM GSH. It was shown that drug release depends on intracellular reducing conditions. Due to their ease of synthesis and scale up, robust structure, and the ability to control size, composition, release, and elimination, biodegradable SiO2 NPs provide an alternative platform for delivery of bioactive and imaging agents.

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.

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.

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.

Evolutionary dynamics of the interferon-induced transmembrane gene family in vertebrates

Vertebrate interferon-induced transmembrane (IFITM) genes have been demonstrated to have extensive and diverse functions, playing important roles in the evolution of vertebrates. Despite observance of their functionality, the evolutionary dynamics of this gene family are complex and currently unknown. Here, we performed detailed evolutionary analyses to unravel the evolutionary history of the vertebrate IFITM family. A total of 174 IFITM orthologous genes and 112 pseudogenes were identified from 27 vertebrate genome sequences. The vertebrate IFITM family can be divided into immunity-related IFITM (IR-IFITM), IFITM5 and IFITM10 sub-families in phylogeny, implying origins from three different progenitors. In general, vertebrate IFITM genes are located in two loci, one containing the IFITM10 gene, and the other locus containing IFITM5 and various numbers of IR-IFITM genes. Conservation of evolutionary synteny was observed in these IFITM genes. Significant functional divergence was detected among the three IFITM sub-families. No gene duplication or positive selection was found in IFITM5 sub-family, implying the functional conservation of IFITM5 in vertebrate evolution, which is involved in bone formation. No IFITM5 locus was identified in the marmoset genome, suggesting a potential association with the tiny size of this monkey. The IFITM10 sub-family was divided into two groups: aquatic and terrestrial types. Functional divergence was detected between the two groups, and five IFITM10-like genes from frog were dispersed into the two groups. Both gene duplication and positive selection were observed in aquatic vertebrate IFITM10-like genes, indicating that IFITM10 might be associated with the adaptation to aquatic environments. A large number of lineage- and species-specific gene duplications were observed in IR-IFITM sub-family and positive selection was detected in IR-IFITM of primates and rodents. Because primates have experienced a long history of viral infection, such rapid expansion and positive selection suggests that the evolution of primate IR-IFITM genes is associated with broad-spectrum antiviral activity.