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Objective To perform a meta-analysis that investigates the prevalence and seroprevalence of celiac disease (CD) in Chinese general population and high-risk populations, and to summarize data from a serological survey of high-risk populations in Guangdong, China. Methods We collected data from the serological survey of high-risk populations in Guangdong, China (n = 1390) by testing serum tissue transglutaminase immunoglobulin A (tTG-IgA), deamidated gliadin peptides immunoglobulin A (DGP-IgA) and deamidated gliadin peptides immunoglobulin G (DGP-IgG), and also searched Medline, PubMed, Embase, Cochrane and 3 Chinese databases up to December 20, 2020 to estimate the pooled prevalence and seroprevalence of CD in China. Results In the serological survey, 0.94% (13/1390) individuals were positive for CD antibodies. In a meta-analysis of 18 studies, the seroprevalence of CD in Chinese general population was 0.27% (95% CI, 0.02-0.71). The seroprevalence of CD in Chinese high-risk populations was 8.34% (95% CI, 4.90-12.54), significantly higher than that in general population (OR 7.27, 95% CI, 4.06-13.04). The prevalence of biopsied-proven CD in high-risk Chinese populations was 4.44% (95% CI, 1.53-8.58). The seroprevalence of CD was varying with geographic origin, higher in Northern China than that in Southern China. Conclusions The basis for diagnosis of CD in Chinese patients should be through early case-finding by serological screening in high-risk groups; generous serological testing in patients with vague symptoms, especially in Northern Chinese.

Food allergy has become a major global public health concern. In the past decades, enzymatic crosslinking technique has been employed to mitigate the immunoreactivity of food allergens. It is an emerging non-thermal technique that can serve as a great alternative to conventional food processing approaches in developing hypoallergenic food products, owing to their benefits of high specificity and selectivity. Enzymatic crosslinking via tyrosinase (TYR), laccase (LAC), peroxidase (PO), and transglutaminase (TG) modifies the structural and biochemical properties of food allergens that subsequently cause denaturation and masking of the antigenic epitopes. LAC, TYR, and PO catalyze the oxidation of tyrosine side chains to initiate protein crosslinking, while TG initiates isopeptide bonding between lysine and glutamine residues. Enzymatic treatment produces a high molecular weight crosslinked polymer with reduced immunoreactivity and IgE-binding potential. Crosslinked allergens further inhibit mast cell degranulation due to the lower immunostimulatory potential that assists in the equilibration of T-helper (Th)1/Th2 immunobalance. This review provides an updated overview of the studies carried out in the last decade on the potential application of enzymatic crosslinking for mitigating food allergenicity that can be of importance in the context of developing hypoallergenic/non-allergenic food products.

BACKGROUND Seronegative coeliac disease is poorly defined. AIMS To study clinical phenotypes and long-term outcomes of seronegative coeliac disease in a multicentre cohort over 20 years. METHODS Seronegative coeliac disease was diagnosed in HLA-DQ2/DQ8-positive patients with villous atrophy (VA), negative IgA endomysial (EmA), tissue transglutaminase (tTG) and deamidated-gliadin antibodies (DGP), clinical and histological response to a gluten-free diet (GFD), and no alternative causes for VA. In patients with IgA deficiency, coeliac disease was diagnosed through VA, positive IgG EmA/tTG/DGP and clinical/histological response to a GFD (coeliac disease+IgAd). Patients with seropositive coeliac disease served as controls. RESULTS Of 227 patients previously diagnosed with seronegative coeliac disease, true seronegative coeliac disease was confirmed in 84, coeliac disease+IgAd in 48, and excluded in 55. Lack of follow-up duodenal biopsy precluded diagnosing seronegative coeliac disease in 40 patients. 2084 patients with seropositive coeliac disease served as controls. True seronegative coeliac disease had more severe symptoms at diagnosis and a higher risk of complications (HR 10.87, 95% CI 6.11-19.33, P

Introduction : Transglutaminase 2 (TG2) has been implicated in numerous neurological conditions, including neurodegenerative diseases, multiple sclerosis, and CNS injury. Early studies on the role of TG2 in neurodegenerative conditions focused on its ability to "crosslink" proteins into insoluble aggregates. However, more recent studies have suggested that this is unlikely to be the primary mechanism by which TG2 contributes to the pathogenic processes. Although the specific mechanisms by which TG2 is involved in neurological conditions have not been clearly defined, TG2 regulates numerous cellular processes through which it could contribute to a specific disease. Given the fact that TG2 is a stress-induced gene and elevated in disease or injury conditions, TG2 inhibitors may be useful neurotherapeutics. Areas covered Overview of TG2 and different TG2 inhibitors. A brief review of TG2 in neurodegenerative diseases, multiple sclerosis and CNS injury and inhibitors that have been tested in different models. Database search: https://pubmed.ncbi.nlm.nih.gov prior to July 1, 2021. Expert opinion : Currently, it appears unlikely that inhibiting TG2 in the context of neurodegenerative diseases would be therapeutically advantageous. However, for multiple sclerosis and CNS injuries, TG2 inhibitors may have the potential to be therapeutically useful and thus there is rationale for their further development.

Some food components can regulate the intestinal barrier function. Herein, the effect of transglutaminase-type oligochitosan glycation on caseinate hydrolysate for its ability to maintain intestinal epithelial integrity and the tight junction (TJ) structure was investigated by assessing and comparing the bioactivities of glycated caseinate hydrolysate and caseinate hydrolysate against the lipopolysaccharide-induced barrier damage in the model cells (rat intestinal epithelial IEC-6 cells). The results from liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis demonstrated that oligochitosan glycation occurred at the Gln residues of α-S1-casein and α-S2-casein. The two hydrolysates retarded the lipopolysaccharide cytotoxicity toward IEC-6 cells and enhanced the barrier integrity by increasing the transepithelial electrical resistance or decreasing the paracellular permeability. In addition, these two hydrolysates could upregulate both mRNA and protein expression of three TJ proteins in IEC-6 cells. More importantly, the glycated caseinate hydrolysate had higher potential than caseinate hydrolysate to protect IEC-6 cells against the lipopolysaccharide-induced barrier damage, suggesting that the transglutaminase-mediated oligochitosan glycation of proteins is a useful approach to enforce protein biofunctions in the intestine.

Transglutaminases are protein cross‐linking and protein‐modifying enzymes that have attracted considerable interest due to their causal involvement in various diseases and versatility in industrial applications. In particular, microbial transglutaminases (MTG) from Streptomyces bacteria have managed in recent years to evolve from simple food additives to specialized enzymes for the site‐directed modification of therapeutic proteins. The review summarizes relevant studies from the beginning dealing with the occurrence, production, structure, catalysis, and substrate molecules of MTG enzymes. It also addresses biotechnological procedures with MTG from S. mobaraensis (SmMTG) as the most prominent representative in focus. Reassessment of the available data revealed unexpected insights into catalysis of SmMTG and other transglutaminases, suggesting selection of glutamine donor proteins by subsites at the front vestibule and the existence of distinct lysine pockets. Flexibility of the SmMTG‐accessible glutamine donor substrate regions seems to be more important than the glutamine environment. Nevertheless, residues in close vicinity to glutamines also determine interaction with the SmMTG subsites. The apparent lack of subsites for lysine donor proteins suggests self‐assembly of the substrate proteins prior to enzymatic cross‐linking. The study of natural substrate proteins, especially their mutual interaction, is proposed to further illuminate catalysis of SmMTG. To this end, structure and function of the characterized substrate proteins from S. mobaraensis are discussed in conclusion.

Transglutiminase-2 (TG2) is a multifunctional enzyme that has been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS) using global knockout mice and TG2 selective inhibitors. Previous studies have identified the expression of TG2 in subsets of macrophages-microglia and astrocytes after EAE. The aims of the current investigation were to examine neuronal expression of TG2 in rodent models of chronic-relapsing and non-relapsing EAE and through co-staining with intracellular and cell death markers, provide insight into the putative role of TG2 in neuronal pathology during disease progression. Here we report that under normal physiological conditions there is a low basal expression of TG2 in the nucleus of neurons, however following EAE or MS, robust induction of cytoplasmic TG2 occurs in most neurons surrounding perivascular lesion sites. Importantly, TG2-positive neurons also labeled for phosphorylated Extracellular signal-regulated kinase 1/2 (ERK1/2) and the apoptotic marker cleaved caspase-3. In white and gray matter lesions, high levels of TG2 were also found within the vasculature and endothelial cells as well as in tissue migrating pericytes or fibroblasts, though rarely did TG2 colocalize with cells identified with glial cell markers (astrocytes, oligodendrocytes and microglia). TG2 induction occurred concurrently with the upregulation of the blood vessel permeability factor and angiogenic molecule Vascular Endothelial Growth Factor (VEGF). Extracellular TG2 was found to juxtapose with fibronectin, within and surrounding blood vessels. Though molecular and pharmacological studies have implicated TG2 in the induction and severity of EAE, the cell autonomous functions of this multifunctional enzyme during disease progression remains to be elucidated.

Background Although specific IgE antibodies reactive to exogenous antigens are found in patients with atopic dermatitis (AD), some patients do not have such antibodies. Autoimmunity has been proposed as a possible mechanism in these patients. Objectives To identify specific IgE antibodies reactive to human transglutaminase 3 (TG3) and tropomysin (TMP) and determine whether auto-reactive T cells are induced by these proteins in patients with AD. Materials & methods Forty-two patients with AD and 27 healthy controls were included in this study. IgE antibodies against recombinant human TG3 and TMP were measured by ELISA. Cross-reactivity between allergens was determined by EdU of peripheral blood mononuclear cells (PBMCs) proliferation assays. T-cell lines were generated from PBMCs in the presence of house dust mites (HDM), TG3 and TMP. TG3/TP-specific T-cell clones were generated from T-cell lines, and were characterized by antigen specificity and cytokine pattern. Results In 12 patients with anti-HDM IgE antibodies, six (50%) had anti-TG3 IgE antibody and four (33.3%) had both anti-TG3 and anti-TMP IgE antibodies. Lymphocyte proliferation was induced in 12 patients by TG3 or TMP. T-cell lines and T-cell clones from PBMCs of patients with AD who had IgE antibody reactive to HDM were fully cross-reactive with TG3 and TMP. These cell clones included both Th1 cell (producing IFN-γ) and Th2 cell (inducing IL-4) responses. TG3-and TMP-specific T-cell clones were not generated from healthy controls. Conclusion Specific IgE antibody and T cell clones reactive to human TG3 and TMP were found in patients with AD, indicating that an autoimmune mechanism might contribute to AD.

Guidelines for celiac disease (CD) testing recommend total serum IgA determination alongside anti-transglutaminase IgA antibodies. It is not well known if lack of serum IgA determination is a common finding in clinical practice. To determine the prevalence of lack of serum IgA determination among patients screened for celiac disease. We identified all subjects who underwent serum anti-transglutaminase IgA and/or other CD-related antibodies determination at a single teaching hospital in Buenos Aires from October 2019 to February 2020. Medical records were reviewed to select adult patients who were tested for celiac disease. The primary outcome was the proportion of patients with inadequate testing for celiac disease due to lack of serum IgA determination. We retrieved the following variables from each patient’s record: age, gender, body mass index, symptoms present at screening, first-grade family history of CD, history of type-1 diabetes mellitus, autoimmune hypothyroidism, Down’s syndrome. Overall, 1122 patients were included for analysis. Lack of serum IgA determination prevalence was 20.49%. Among patients who did have serum IgA determination, the prevalence of IgA deficiency was 5.16%. The following variables were independently associated with a significantly increased odds of serum IgA determination: diarrhea [OR 1.55 (1.01–2.34)] and abdominal pain [OR 2.28 (1.44–3.63)]; higher body mass index [OR 0.91 (0.85–0.98)], osteoporosis [OR 0.49 (0.28–0.89)], hypothyroidism [OR 0.18 (0.07–0.45)], arthralgia/arthritis [OR 0.47 (0.27–0.85)], or testing by endocrinologist [OR 0.46 (0.23–0.91)] and gynecologist [OR 0.14 (0.06–0.31)] were inversely associated. IgA deficiency is not systematically ruled out in a relatively high proportion of patients undergoing serological screening of celiac disease.

BACKGROUNDS The structural and interfacial properties of soybean protein isolate (SPI) after glycosylation by the transglutaminase method were studied. It is hoped that preliminary explorations will find a new food ingredient and broader application of SPI in the food industry. RESULTS The contents of free amino proves that transglutaminase can insert glucosamine into SPI through its transamination, and realize the enzymatic glycosylated SPI. The results of structure properties showed that a decrease in the content of the α-helical structure indicates that the rigid structure of the protein is opened and the flexibility is increased. The blue shift of the maximum fluorescence intensity of soy protein isolate-glucosamine with transglutaminase (SPI-G) indicates the formation of a new substance; scanning electron microscopy shows that the SPI-G powder can be seen at a magnification of 2000×, and the protein structure becomes soft. The results of interfacial properties found that enzymatic protein glycosylation exposes the internal hydrophobic groups of SPI, resulting in increased surface hydrophobicity, increased emulsification and emulsification stability, and reduced surface tension. CONCLUSION It shows that SPI-G effectively improves the interfacial properties of SPI, providing a theoretical basis for the application of enzymatic glycosylation of SPI in the food industry. © 2021 Society of Chemical Industry.

Serological markers are used in the diagnosis of celiac disease. Among these, the most widely used are tissue transglutaminase antibodies (anti-TG2 antibodies). It has been suggested that the mechanisms that are set in motion by malnutrition cause the tight connections between enterocytes to expand, which allows gluten-derived peptides to pass through the epithelium. This causes the production of anti-TG2 antibodies without the presence of celiac disease.The patients who were examined for malnutrition and had their anti-TG2 antibody levels measured at the same time, were accepted into the study. The patients who were investigated for suspected celiac disease, showed no signs of malnutrition, and had their anti-TG2 antibody levels measured were accepted into a control group.The study population consisted of 126 children with mild malnutrition (54.8% female, 7.44 ± 5.38 years); 89 children with moderate malnutrition (54.8% female, 7.62 ± 5.43 years), and a control group of 200 children (53.2% female, 7.72 ± 5.05 years). According to the results, anti-TG2 IgG levels were significantly higher among patients in the mild and moderate malnutrition groups compared to patients in the control group (Malnutrition does not affect anti-TG2 IgA levels in children. However, anti-TG2 IgG levels increase in children suffering from malnutrition. When examining celiac disease, especially in people with a background IgA deficiency, doctors should consider whether malnutrition may be the cause of the increase in serum anti-TG2 IgG levels without celiac disease.

Background Studies have indicated that underdiagnosis and diagnostic delay are common in celiac disease. Therefore, it is important to increase our knowledge of what symptoms and biomarkers could identify undiagnosed cases of celiac disease. Methods We screened for celiac disease antibodies in stored blood samples from 16,776 participants in eight population-based studies examined during 1976–2012. Undiagnosed celiac seropositivity was defined as celiac disease antibody positivity (IgG-deamidated gliadin peptide above 10.0 U/mL and/or IgA-tissue transglutaminase (TTG) or IgG-TTG above 7.0 U/mL) without a known diagnosis of celiac disease in the National Patient Register. In all studies general health symptoms were recorded by participant-completed questionnaire, including self-perceived health, tiredness, headache and gastrointestinal symptoms. Furthermore, blood samples were drawn for analyses of biomarkers e.g. hemoglobin, blood glucose, cholesterol, liver parameters and vitamins. The participants with undiagnosed celiac seropositivity were matched by sex, age and study with four controls among the celiac disease antibody negative participants. Results We excluded, five participants with known celiac disease, resulting in a population of 16,771 participants. In this population 1% (169/16,771) had undiagnosed celiac seropositivity. There were no statistically significant differences in symptoms between cases and controls. Undiagnosed celiac seropositivity was associated with low blood cholesterol ( Conclusion In this general population study, undiagnosed cases of celiac seropositivity did not have more symptoms than controls, confirming the diagnostic difficulties of celiac disease and the low prognostic value of symptoms for a diagnosis of celiac disease. Furthermore, decreased levels of cholesterol and/or hemoglobin in the blood were associated with undiagnosed celiac seropositivity.

The tumor microenvironment plays an essential role in supporting glioma stemness and radioresistance. Following radiotherapy, recurrent gliomas form in an irradiated microenvironment. Here we report that astrocytes, when pre-irradiated, increase stemness and survival of cocultured glioma cells. Tumor-naïve brains increased reactive astrocytes in response to radiation, and mice subjected to radiation prior to implantation of glioma cells developed more aggressive tumors. Extracellular matrix derived from irradiated astrocytes were found to be a major driver of this phenotype and astrocyte-derived transglutaminase 2 (TGM2) was identified as a promoter of glioma stemness and radioresistance. TGM2 levels increased after radiation in vivo and in recurrent human glioma, and TGM2 inhibitors abrogated glioma stemness and survival. These data suggest that irradiation of the brain results in the formation of a tumor-supportive microenvironment. Therapeutic targeting of radiation-induced, astrocyte-derived extracellular matrix proteins may enhance the efficacy of standard-of-care radiotherapy by reducing stemness in glioma. Significance: These findings presented here indicate that radiotherapy can result in a tumor-supportive microenvironment, the targeting of which may be necessary to overcome tumor cell therapeutic resistance and recurrence.

Background Traditional soy protein isolate (SPI)-based gel products, such as tofu, are generally produced by heating and by addition of metal salt ions to adjust the hydrophobicity and electrostatic force of soybean protein to facilitate the formation of a uniform network structure. However, the gelation rate of the soy protein gel network structure is difficult to control. Theoretically, epigallocatechin-3-gallate (EGCG) could be used to alter the surface hydrophobicity of thermally-induced SPI to improve their gelation rate and form a more uniform network structure, thus improving SPI-based gel properties (hardness, water-holding capacity and rheological properties). Results An SPI-EGCG complex (SPIE) was prepared, and properties of the resulting gel, following induction of transglutaminase (TG), were evaluated. Results showed that EGCG are bound to thermally-induced SPI primarily via hydrophobic and hydrogen bonding, thus altering the secondary structure composition and reducing surface hydrophobicity of proteins in thermally-induced SPI. Furthermore, the optimum amount of EGCG required to improve the gel strength, water-holding capacity and rheological properties was ≤0.04:1 (SPI 1 g L -1 , EGCG:SPI, w/w). Thermal stability analysis further indicated that EGCG in SPIE was more stable than free EGCG after heating. Conclusion This study demonstrated that EGCG can improve the gel properties of TG-cross-linked SPIE, while EGCG in SPIE exhibits enhanced thermal stability. Additionally, the results of this study provide a novel strategy for the development of SPI-based gel foods with improved gel properties and that are enriched with bioactive compounds. This article is protected by copyright. All rights reserved.

BACKGROUND Although Streptomyces mobaraense transglutaminase (MTG) has been extensively applied to enhance the functional characteristics of soy protein isolate (SPI) through cross-linking, various transglutaminases (TGs) in nature may provide more choice in the food industry. Previous research reported that TG derived from Bacillus subtilis (BTG) exhibited better pH stability and thermostability than MTG. RESULTS An attempt was made to study the influence of BTG induced cross-linking on the properties of SPI. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results indicated that almost all protein constituents (α', α, β, AS, and BS) in SPI could be cross-linked with BTG treatment. The BTG treatment also resulted in a significant increase (*P

The chemical cross-linkers are difficult to be removed from the scaffold materials, which limit their application in tissue engineering; designing an efficient biocompatible hydrogel is though challenging is desirable. The aim of the present study was to immobilize microbial Transglutaminase (MTGase) enzyme on multi-walled carbon nanotubes (MWCNTs) for its application in hydrogel scaffolds designing. MTGase from Streptomyces mobaraensis, a non-toxic biological cross-linker, was employed for a greener approach with enhanced biochemical and structural properties. The maximum immobilization efficiency of 58% was achieved when MTGase was covalently coupled on MWCNTs. The kinetic studies showed 4.76-fold increase in catalytic efficiency and good reusability upto seven cycles. Attachment of enzyme on MWCNTs surface was studied through SEM and FTIR. The immobilized enzyme showed good cross-linking efficiency in gelatin hydrogel scaffold resulting decrease in swelling ratio of hydrogel. Our findings report for the first time the development of novel biocompatible hydrogel scaffolds with immobilized MTGase onto MWCNTS. Inevitable damage of hydrogels are incurred during their applications. To offset the damage of hydrogels, the creation of bioinspired hydrogels emulating native tissue microenvironment is highly significant. Microbial TGase holds promising future with its applicability as a cross-linker of hydrogel scaffolds in the area of tissue engineering.

The crosslinking and related gel properties of 3 wt% gelatin (type-A and type-B) catalyzed by microbial transglutaminase (MTG, dose of 0–20 U/g gelatin) have been investigated. A MTG-depended increase in the molecular weight and mean diameter of both gelatins was observed, where type-A presented a higher crosslinking efficiency than type-B due to more acyl donors of the former. As MTG concentration increased, the surface hydrophobicity and thermal stability of type-A gelatin increased. Textural profile analysis (TPA) of type-A gelatin hydrogel showed a decrease in hardness and slight increase in springiness, while type-B gelatin gel was not affected generally. Rheological measurements confirmed the melting point of type-A gelatin hydrogel continually increased until the disappearance of gel thermo-reversibility at higher MTG levels (≥12 U/g gelatin), while type-B gelatin hydrogel always showed a sol-gel transition, suggesting that the gel performance was depended on the dominance of whether physical crosslinking or chemical crosslinking. Scanning electron microscope (SEM) results showed that the network structure of the type-A gelatin became more irregular as MTG increasing which indicated that introducing additional covalent cross-links within or between gelatin chains had a profound influence on gel's network structure, closely associated with the gel properties mentioned above. In summary, the superiority of type-A in MTG-crosslinking efficiency than type-B, can be used to modulate the physical and mechanical properties of gelatin hydrogel, governing by the combing of weak physical crosslinking and strong covalent crosslinking, which will be suitable for numerous industrial applications.

Transglutaminase (TGase) is inextricably associated with plant growth and development. However, the mechanism by which TGase enhances salt tolerance of higher plants under salt stress is poorly understood. In this study, we investigated the effects of NaCl stress and exogenous o-phenanthroline (o-Phen, a metalloprotease inhibitor) on TGase activity, chlorophyll fluorescence parameters, carbohydrates contents, the reactive oxygen species (ROS) scavenging system, and endogenous polyamines (PAs) contents of salt-sensitive ‘Jinyou No. 4′ and salt-tolerant ‘Inbred Line 9930’ cucumber. Salt stress significantly inhibited plant growth of the two cultivars, as well as hindered carbohydrates transport, which was more evident in the salt-sensitive cultivar. TGase activity and expression, ROS scavenging capacity, and bound PAs content were up-regulated by salt stress to some extent, which was more distinct in the salt-tolerant cucumber cultivar. However, o-Phen treatment significantly inhibited TGase expression, and further decreased plant growth and the actual photochemical efficiency of photosystem II in the two cultivars. In addition, application of o-Phen significantly decreased endogenous PAs content in leaves of ‘Jinyou No. 4’ and ‘Inbred Line 9930’ seedlings by 9.60% and 42.32% under NaCl stress, respectively. These results suggested that high activity of TGase increases the salt stress tolerance of cucumber plants by increasing endogenous PAs content and ROS scavenging capacity, and promoting carbon assimilation and photosynthetic products.

Elastic fibres are essential components of all mammalian elastic tissues such as blood vessels, lung and skin, and are critically important for the mechanical properties they endow. The main components of elastic fibres are elastin and fibrillin, where correct formation of elastic fibres requires a fibrillin microfibril scaffold for the deposition of elastin. It has been demonstrated previously that the interaction between fibrillin and tropoelastin, the elastin precursor, increases the rate of assembly of tropoelastin. Furthermore, tropoelastin and fibrillin can be cross-linked by transglutaminase-2, but the function of cross-linking on their elastic properties is yet to be elucidated. Here we show that transglutaminase cross-linking supports formation of a 1:1 stoichiometric fibrillin–tropoelastin complex. SAXS data show that the complex retains features of the individual proteins but is elongated supporting end-to-end assembly. Elastic network models were constructed to compare the dynamics of tropoelastin and fibrillin individually as well as in the cross-linked complex. Normal mode analysis was performed to determine the structures' most energetically favourable, biologically accessible motions which show that within the complex, tropoelastin is less mobile and this molecular stabilisation extends along the length of the tropoelastin molecule to regions remote from the cross-linking site. Together, these data suggest a long-range stabilising effect of cross-linking that occurs due to the covalent linkage of fibrillin to tropoelastin. This work provides insight into the interactions of tropoelastin and fibrillin and how cross-link formation stabilises the elastin precursor so it is primed for elastic fibre assembly., Graphical abstract Unlabelled Image, Highlights • Elastic fibres, essential for mammalian tissue elasticity, contain elastin and fibrillin. • Tissue transglutaminase cross-links fibrillin and tropoelastin to form a complex. • The complex has an elongated structure that supports end-to-end assembly. • Cross-linking restricts the molecular motions of tropoelastin and fibrillin. • Stabilisation may provide an initiating molecular mechanism for elastic fibre assembly.

Background/Purpose Oral cancer is amongst the most prevalent cancers worldwide with rising incidence. Various attempts have been made to elucidate its pathogenesis, and we sought to examine the function of a ubiquitin E3 ligase that was encoded by STUB1. Methods The mRNA expression of STUB1 in oral cancer samples and normal counterparts was determined by qRT-PCR. Numerous assays to assess the features of cancer cells, including self-renewal capacity, invasion and migration abilities were conducted following knockdown or overexpression of STUB1. Results The expression level of STUB1 was reduced in oral cancer, which was associated with a reduced relapse-free survival. Two oral cancer cell lines with low expression of STUB1 (SAS and HSC3) were chosen for the overexpression of STUB1. We showed that ectopic expression of STUB1 led to the downregulation of TGM2, a multifunctional protein that contributed to cancer progression in several cancers. Our results demonstrated that overexpression of STUB1 suppressed the cancer aggressiveness, while restoration of TGM2 reverted the effects. Last, we showed that STUB1 silencing resulted in enhanced cancer features. Conclusion The abnormal downregulation of STUB1 may lessen its suppressive effect on TGM2, which induced the onset or exacerbated the progression of oral cancer. The therapeutic approach to enhance the expression of STUB1 could be a promising direction for cancer therapy.

A cold-active transglutaminase (TGase, EC 2.3.2.13) that catalyzes the reaction of protein glutamine + protein lysine ↔ protein with γ-glutamyl-e-lysine cross-link + NH3 at low temperatures was reported previously. This study verified the thermal stability of the TGase from 0-80 °C. Fluorescence and CD spectra studies confirmed tertiary structural damage at 40 °C, α-helix reduction at 60 °C, and refolding during cooling to 20 °C. The TGase sequence was obtained by transcriptomics and used to build its structure. Its catalytic triad was Cys333-His403-Asp426 and its catalytic process was inferred from the model. Molecular dynamics simulation illustrated that its cold activity resulted from its flexible active site, while high thermostability was conferred by an overall rigid structure, a large amount of stable Val and Lys, and strong electrostatic interactions at the N- and C- terminals. This study fills gaps in the correlation of conformational changes with stability and activity of TGase.

OBJECTIVES: Assessment of adherence to gluten-free diet in celiac disease (CD) is generally recommended. Few data are available about consequences of transition from the referral center to the general pediatrician (GP) once remission is achieved. METHODS: Adherence was assessed in patients referred to the GP for an annual basis follow-up, called back for re-evaluation. Immunoglobulin A (IgA) antitissue transglutaminase (anti-tTG) antibodies and the Biagi score (BS) were determined at last follow-up at the referral center (V1), and at re-evaluation (V2). Patients were classified as adherent (BS 3-4, IgA anti-tTG

Background Prognosis of hepatocellular carcinoma (HCC) remains poor despite significant recent improvement in therapy. Recent studies have reported that transglutaminase 3 (TGM3) plays an important role in several human cancer types. However, the role of TGM3 in HCC have not been previously elucidated. Methods We evaluated the role of TGM3 in regulating HCC cell proliferation, migration, and invasion. We also investigated the prognostic significance of TGM3 in an HCC cohort. Finally, we explored the signalling pathways that TGM3 regulates in HCC. Results We identified TGM3 to be overexpressed in HCC compared to normal tissues. Higher expression of TGM3 predicts poor prognosis in HCC patients. TGM3 knockdown led to decreased HCC cell proliferation, invasion, and xenograft tumour growth. TGM3 depletion inhibited AKT, extracellular signal–regulated kinase (ERK), p65, and glycogen synthase kinase 3β (GSK3β)/β-catenin activation, but promoted levels of cleaved caspase 3. Moreover, TGM3 knockdown cells had increased E-cadherin levels and decreased vimentin levels, suggesting that TGM3 contributes to epithelial–mesenchymal transition (EMT) in HCC. Conclusion Our results suggest that TGM3 controls multiple oncogenic pathways in HCC, thereby contributing to increased cell proliferation and EMT, and TGM3 potentially enhances HCC metastasis. TGM3 may serve as a novel therapeutic target in HCC.

Background aims The pro-regeneration capabilities of olfactory ensheathing cells (OECs) remain controversial. However, little is known regarding whether the transplantation of activated OECs by curcumin (CCM) elicits neural regeneration and functional recovery after spinal cord injury (SCI) in rats, and the possible molecular mechanisms have never been investigated. Methods Primary OECs were treated with 1μM CCM for 1–3 days. Concomitantly, activated OECs were transplanted into the traumatic spinal cord of Sprague Dawley rats. One to 9 weeks after surgery, the assessment of behavior recovery was made using the Basso, Beattie and Bresnahan (BBB) locomotor scale; electrophysiology tests, such as somatosensory evoked potential (SEP) and motor evoked potential (MEP); and the cylinder test. Pathological study, including hematoxylin and eosin staining and immunofluorescence staining for neurofilaments (NFs), was conducted at 5 weeks post-surgery. In addition, activation profiles of OECs by CCM stimulus were assessed and levels of transglutaminase-2 (TG2) and phosphatidylserine receptor (PSR) in OECs stimulated by CCM were further determined. Results CCM remarkably enhanced OEC proliferation, improved cell viability and strengthened secretion of neurotrophins and anti-inflammatory factors. In addition, the levels of TG2 and PSR in CCM-treated OECs were significantly elevated. More importantly, beyond 1 week post-transplantation of CCM-treated OECs into lesioned spinal cord, BBB score and cylinder test score were significantly higher than that seen in the other three groups and a more postponed latent SEP and MEP period was noted. Furthermore, 5 weeks later, numerous, well-arranged NF-positive nerve fibers, lesions with less cavities and reduced levels of pro-inflammatory cytokines were found in activated OEC implantation groups. In addition, the number of NF-positive fibers was significantly improved and the number and area of both cavities and gliotic scars were remarkably decreased compared with the corresponding controls. Conclusions Transplantation of OECs activated by CCM promotes neural regeneration and functional recovery following SCI, the underlying mechanisms of which are intimately associated with the elevated production of neurotrophic factors and anti-inflammatory factors in OECs stimulated by CCM as well as reduced pro-inflammatory cytokines from the post-contusion spinal cord. In addition, OECs activated by CCM were mediated through TG2 and PSR.

Human Leukocyte Antigen (HLA)-DQ2 and HLA-DQ8 are genetic risk factors for Type 1 Diabetes Mellitus (T1DM) and Celiac disease (CD) in Caucasians, but their association with Taiwanese Han population is unknown. We screened 532 Taiwanese T1DM patients for CD biomarkers including anti-tissue transglutaminase (TGM2), anti-gliadin and anti-neoepitope antibodies (Abs), sequencing DQB1 genotypes, and characterized the TGM2 Abs. We report that 3.76% of Taiwanese patients had TGM2-Abs and all had no CD's symptoms. In contrast to Caucasian's CD patients, DQ2/DQ8 only constituted ~4/5 of TGM2-Abs positive patients, while the other ~1/5 patients belonged to different HLA genotypes. Either anti-gliadin or anti-neoepitope Abs coexisted with ~3/4 of TGM2-Abs positive patients that were likely due to gluten-ingestion, while the cause of TGM2-Abs production for other ~1/4 of patients was unknown. Purified anti-TGM2 IgA (TGA) and anti-TGM2 IgG (TGG) could bind on endothelial cells surface, recognized native better than denatured forms of TGM2, and TGA inhibited TGM2's transamidation activity by up to 80% but TGG had no effects. Epitope mapping of all TGM2-Abs positive sera demonstrated that TGM2-Abs had heterogeneity in specificities. This is the first study on the differences between Taiwanese Han group and Caucasian in HLA genotypes and properties of TGM2-Abs.

Protein ubiquitination is one of the most prevalent post-translational modifications, controlling virtually every process in eukaryotic cells. Recently, the Legionella effector MavC was found to mediate a unique ubiquitination through transglutamination, linking ubiquitin (Ub) to UBE2N through UbGln40 in a process that can be inhibited by another Legionella effector, Lpg2149. Here, we report the structures of MavC/UBE2N/Ub ternary complex, MavC/UBE2N-Ub (product) binary complex, and MavC/Lpg2149 binary complex. During the ubiquitination, the loop containing the modification site K92 of UBE2N undergoes marked conformational change, and Lpg2149 inhibits this ubiquitination through competing with Ub to bind MavC. Moreover, we found that MavC itself also exhibits weak deubiquitinase activity towards this non-canonical ubiquitination. Together, our study not only provides insights into the mechanism and inhibition of this transglutaminase-induced ubiquitination by MavC, but also sheds light on the future studies into UBE2N inhibition by this modification and deubiquitinases of this unique ubiquitination., The Legionella effector MavC catalyses the ubiquitination of the E2 enzyme UBE2N in the host cell through a transglutamination reaction, which can be inhibited by the Legionella effector Lpg2149. Here, the authors provide mechanistic insights into these processes by determining the crystal structures of the MavC/UBE2N/Ub ternary complex, the MavC/UBE2N-Ub product complex and the MavC/Lpg2149 complex.

Site-specific bioconjugation technologies are frequently employed to generate homogeneous antibody-drug conjugates (ADCs) and are generally considered superior to stochastic approaches like lysine coupling. However, most of the technologies developed so far require undesired manipulation of the antibody sequence or its glycan structures. Herein, we report the successful engineering of microbial transglutaminase enabling efficient, site-specific conjugation of drug-linker constructs to position HC-Q295 of native, fully glycosylated IgG-type antibodies. ADCs generated via this approach demonstrate excellent stability

As cartilage is incapable of self-healing upon severe degeneration because of the lack of blood vessels, cartilage tissue engineering is gaining importance in the treatment of cartilage defects. This study was designed to improve cartilage tissue regeneration by expressing tissue transglutaminase variant 2 (TGM2_v2) in mesenchymal stem cells (MSC) derived from bone marrow of rats. For this purpose, rat MSCs transduced with TGM2_v2 were grown and differentiated on three-dimensional polybutylene succinate (PBSu) and poly-l-lactide (PLLA) blend scaffolds. The transduced cells could not only successfully express the short form transglutaminase-2, but also deposited the protein onto the scaffolds. In addition, they could spontaneously produce cartilage-specific proteins without any chondrogenic induction, suggesting that TGM2_v2 expression provided the cells the ability of chondrogenic differentiation. PBSu:PLLA scaffolds loaded with TGM2_v2 expressing MSCs could be used in repair of articular cartilage defects.

Horse milk is a valuable raw material and a very attractive alternative for scientific research to address the issue of cow milk (CM) allergy due to its protein profile. A decrease in immunoreactive properties can be achieved by thermal, enzymatic, and hydrolytic processing. Therefore, the aim of this study was to explore the possibility of reducing the immunoreactivity of horse milk proteins by microbial transglutaminase (TG) polymerization. To determine how TG linking alters immunoreactivity under simulated digestion of the examined milk, analyses were performed before, during, and after digestion. The dose-dependent (1, 10, and 100 U) effects of microbial TG on horse and cow milk were analyzed. A consecutive 3-stage digestion was simulated with salivary, gastric, and intestinal fluids. The effects of digestion were analyzed by SDS-PAGE, particle size analysis, and size-exclusion chromatography. Immunoreactivity was assessed using competitive ELISA (β-lactoglobulin and α-casein) and immunodot (sera from 7 patients aged 3 to 13 years who are allergic to CM proteins). Horse milk contained almost half of the amount of total proteins in CM. The dose 1 U/g of total milk protein changed the immunoreactivity of both cow and horse milk. With increasing TG doses, α-casein immunoreactivity increased, and β-lactoglobulin decreased. After total digestion, horse milk was characterized by 2.4-fold lower average IgE and 4.8-fold lower IgG reactivity than CM. We found that TG alters the IgE and IgG reactivity of CM after in vitro digestion. Horse milk was less reactive to IgE and IgG than was CM, with animal and patient sera. The effect of TG on immunoreactivity depends on enzyme quantity and milk protein type. The diet based on modified horse milk proteins could be an alternative for some patients with CM protein allergy; however, confirmation through clinical trials is needed.

In order to find a connection between the alteration of oral tissues and genetic predisposition to inflammatory and destructive processes in oral media, the cytokine profile of the oral fluid of clinically healthy individuals was determined for various blood group affiliations according to the AB0 system. The group-specific features of individuals with B(III) blood group were revealed: an increase of 32,5% in the content of interleukin-6 and 63,1% in the content of interleukin-8 compared with similar data for people with 0(I), A(II), AB(IV) blood groups, which can predispose to the greatest activity of the inflammatory process in the oral cavity in individuals with antigen B. Confirmation of this fact is an increase of IgA antibodies to gliadin in the blood among patients with chronic generalized periodontitis with B(III) blood group, up to 5,00 U/ml (p

OBJECTIVES The aim of the study was to describe diagnostic criteria used in children with coeliac disease (CD) and selective IgA deficiency; to determine if the publication of the 2012 ESPGHAN criteria prompted any changes; to evaluate the evolution of serological markers. METHODS Multicenter, retrospective, descriptive study of a cohort of children under 15 years with selective IgA deficiency diagnosed with CD (January 2006 to December 2016). Demographic, clinical, genetic, histological and IgG-based antibodies were collected at diagnosis and follow-up. RESULTS Eighty-six children were included, 60 diagnosed after the guide. Two groups were established: G1 (n = 63) and G2 (n = 23) with or without diagnostic biopsy respectively. In G1: 87.3% were symptomatic, 87.3% had human leukocyte antigan (HLA) DQ2/DQ8 typing (all positive), all had IgG serology positive (71.5% ATG, 35% EMA, 19% DPG, 9.5% AGA), and all had villous atrophy (Marsh-Oberhuber 2-3). Follow-up data were available in 58 children, 34 after 2 years on a gluten-free diet. Fifty-two percentage remained ATG IgG-positive despite good dietary adherence and symptom remission. Regarding G2: all were diagnosed post-2012, had typical symptoms, HLA DQ2/DQ8 positive and ATG IgG × 10 ULN. Additionally, EMA IgG was performed in 14 (60%), all positive. CONCLUSIONS In our cohort of children with selective IgA deficiency and diagnosed with CD, children without a diagnostic biopsy suggests that IgG serology was considered the equivalent as IgA isotype, even when this is not addressed in the aforementioned guidelines. Great heterogeneity was observed in the IgG serology used at diagnosis. After 2 years of a gluten-free diet, half of children remained with a positive serology.

This study aims to investigate the prevalence of islet autoantibodies and other organ-specific autoantibodies in type 1 diabetes mellitus (T1DM) patients and characterize their clinical features. Glutamic acid decarboxylase antibody (GADA), insulinoma antigen 2 antibody (IA-2A), zinc transporter 8 antibody (ZnT8A) and tetraspanin7 antibody (TSPAN7A) were assayed by radioligand or luciferase immunoprecipitation system assays in 205 newly diagnosed acute-onset T1DM patients and 170 healthy controls. Other organ-specific autoantibodies, including thyroid peroxidase antibody (TPOA), thyroglobulin antibody (TGA), tissue transglutaminase antibody (tTGA) and 21-hydroxylase antibody (21-OHA), were also measured. The prevalence of GADA, IA-2A, ZnT8A, TSPAN7A, TPOA, TGA and 21-OHA was higher in T1DM patients than in healthy controls. The combinational assay of various islet autoantibodies could increase the frequency of autoantibody positivity in T1DM to 85.4%. GADA+ IA-2A+ T1DM patients preferentially had TPOA and TGA, while IA-2A+ patients often had tTGA. Patients positive for two or more islet autoantibodies often had TPOA and TGA. BMI of multiple islet autoantibody-positive patients was lower than that of patients with single or no islet autoantibodies, and there were no significant differences in C-peptide and glycated hemoglobin between patients positive for islet autoantibodies combined with other organ-specific antibodies and noncombined patients. Younger female patients who were islet autoantibody positive were more likely to have TPOA and TGA. The frequency of Graves' disease was much higher in T1DM patients than in healthy controls. T1DM usually occurs together with other organ-specific autoantibodies. Measuring of other organ-specific autoantibodies will be beneficial for T1DM patients.

Nattokinase is a thrombolytic enzyme obtained from Japanese traditional food natto for prevention and cure of thrombosis-related cardiovascular diseases. However, the effectiveness of nattokinase through oral intake is limited, due to the loss of thrombolytic activity in the acidic gastric juice. In this study, we develop a functional oral delivery system of nattokinase, in which chitosan microparticles were used as the carrier core to load nattokinase via genipin crosslinking and then covered by a casein-based protective shell via transglutaminase (TG) crosslinking. The results of in vitro and in vivo assays, in the aspects of bioactivity, release dynamics, and therapeutic effects, indicated that the bilayer shell-core structure could protect loaded nattokinase from destruction in the gastric juice and achieve its controlled-release in the intestine. This work demonstrates the availability of bilayer shell-core structure design in oral delivery of nattokinase and shows its high potential for application as an anti-thrombosis functional food additive.

We report a water-soluble and non-toxic method to incorporate additional extracellular matrix proteins into gelatin hydrogels, while obviating the use of chemical crosslinkers such as glutaraldehyde. Gelatin hydrogels were fabricated using a range of gelatin concentrations (4%-10%) that corresponded to elastic moduli of approximately 1 kPa-25 kPa, respectively, a substrate stiffness relevant for multiple cell types. Microbial transglutaminase was then used to enzymatically crosslink a layer of laminin on top of gelatin hydrogels, resulting in 2-component gelatin-laminin hydrogels. Human induced pluripotent stem cell derived spinal spheroids readily adhered and rapidly extended axons on GEL-LN hydrogels. Axons displayed a more mature morphology and superior electrophysiological properties on GEL-LN hydrogels compared to the controls. Schwann cells on GEL-LN hydrogels adhered and proliferated normally, displayed a healthy morphology, and maintained the expression of Schwann cell specific markers. Lastly, skeletal muscle cells on GEL-LN hydrogels achieved long-term culture for up to 28 days without delamination, while expressing higher levels of terminal genes including myosin heavy chain, MyoD, MuSK, and M-cadherin suggesting enhanced maturation potential and myotube formation compared to the controls. Future studies will employ the superior culture outcomes of this hybrid substrate for engineering functional neuromuscular junctions and related organ on a chip applications.

The rheological behavior, assembly measurements, thermal stability, molecular conformation, and molecular interactions of myofibrillar proteins (MP) modified by transglutaminase (TGase) and epigallocatechin-3-gallate (EGCG) were investigated. Fluorescence and ultraviolet spectra showed that TGase and ECCG quenched the endogenous fluorescence of MP and improved the exposure of chromophoric and hydrophobic groups of MP caused by unraveling the tertiary structure. TGase and EGCG treatment increased the α-helix and β-turn contents and the structure became more ordered. It also increased the thermal stability of MP and the storage modulus of MP gels as reflected in the rheological and thermal properties tests. Meanwhile, changes in SDS-PAGE, FT-IR, and sulfhydryl contents showed that TGase increased the disulfide bond contents, whereas it decreased after EGCG was added, suggesting that EGCG could react with MP via non-covalent and covalent interactions. Assembly measurements illustrated that TGase increased the turbidity and particle size of MP, while TGase and EGCG treatment accelerated MP aggregation and it was associated with the increase in the EGCG concentration, which was further confirmed by SEM and AFM. This work could contribute new insights into the synergistic effect of TGase and EGCG on modifying MP and guide for its application in surimi processing.

In wound healing, the TG2 enzyme plays a dual functional role. TG2 has been shown to regulate extracellular matrix (ECM) stabilization by its transamidase activity while increasing cell migration by acting as a cell adhesion molecule. In this process, nitric oxide (NO) plays a particularly important role by nitrosylation of free cysteine ​​residues on TG2, leading to the irreversible inactivation of the catalytic activity. In this study, transfected fibroblasts expressing TG2 under the control of the tetracycline-off promoter were treated with NO donor S-nitroso-N-acetyl penicillamine (SNAP) to analyze the interplay between NO and TG2 in the regulation of cell migration/invasion as well as TGF-β1-dependent MMP activation. Our results demonstrated that inhibition of TG2 cross-linking activity by SNAP promoted the migration and invasion capacity of fibroblasts by hindering TG2-mediated TGF-β1 activation. While the inhibition of TG2 activity by NO downregulated the biosynthesis and activity of MMP-2 and MMP-9, that of MMP-1a and MMP-13 was shown to be upregulated in a TGF-β1-dependent manner under the same conditions. In the presence of SNAP, interaction of TG2 with its cell surface binding partners Integrin-β1 and Syndecan-4 was reduced, which was paralleled by an increase in TG2 and PDGF association. These findings suggests that migratory phenotype of fibroblasts can be regulated by the interplay between nitric oxide and TG2 activity.

Transglutaminase (TG) from Streptomyces mobaraensis has been widely used in the food industry. It is secreted naturally as an inactive zymogen, which is then activated by the removal of the N-terminal pro-peptide. In this study, the mtg gene from S. mobaraensis was expressed in a food-grade strain of bacterium, Bacillus subtilis. When its native signal peptide was replaced by signal peptide SacB (SPsacB) and the pro-peptide was replaced by that derived from S. hygroscopicus, an extracellular activity of 16.1 U/mg was observed. A modified Saccharomyces cerevisiae vacuolar ATPase subunit (VMA) intein was introduced into the zymogen to simplify its activation process by controlling temperature. When the cleavage site in the C-terminal of VMA was placed between the pro-peptide and core domain, the activation process was carried out at 18 °C. Promoter replacement further increased the enzymatic activity. Finally, the extracellular enzymatic activity reached 2.6 U/mg under the control of the constitutive promoter PyvyD. This is the first report on the extracellular production of active-form Streptomyces TG in B. subtilis without splicing with the cleavage enzyme.

The detailed pathogenesis of eosinophilic bronchitis (EB) remains unclear. Transglutaminase 2 (TG2) has been implicated in many respiratory diseases including asthma. Herein, we aim to assess preliminarily the relationship of TG2 with EB in the context of the development of an appropriate EB model through ovalbumin (OVA) sensitization and challenge in the C57BL/6 mouse strain. Our data lead us to propose a 50 μg dose of OVA challenge as appropriate to establish an EB model in C57BL/6 mice, whereas a challenge with a 400 μg dose of OVA significantly induced asthma. Compared to controls, TG2 is up-regulated in the airway epithelium of EB mice and EB patients. When TG2 activity was inhibited by cystamine treatment, there were no effects on airway responsiveness; in contrast, the lung pathology score and eosinophil counts in bronchoalveolar lavage fluid were significantly increased whereas the cough frequency was significantly decreased. The expression levels of interleukin (IL)-4, IL-13, IL-6, mast cell protease7 and the transient receptor potential (TRP) ankyrin 1 (TRPA1), TRP vanilloid 1 (TRPV1) were significantly decreased. These data open the possibility of an involvement of TG2 in mediating the increased cough frequency in EB through the regulation of TRPA1 and TRPV1 expression. The establishment of an EB model in C57BL/6 mice opens the way for a genetic investigation of the involvement of TG2 and other molecules in this disease using KO mice, which are often generated in the C57BL/6 genetic background.

Transglutaminases are protein modifying enzymes involved in physiological and pathological processes with potent therapeutic possibilities. Human TG4, also called prostate transglutaminase, is frequently associated with pathological symptoms and particularly with cancer invasiveness. Although rodent TG4 is well characterised, bio-chemical characteristics of human TG4 that could help the understanding of its way of action are not published. First, we analysed proteomics databases and found that TG4 protein is present in human tissues beyond the prostate. Then, we studied in vitro the transamidase activity of human TG4 and its regulation using the microtiter plate method. Human TG4 has low transamidase activity which prefers slightly acidic pH and a reducing environment. It is enhanced by submicellar concentrations of SDS suggesting that membrane proximity is an important regulatory event. Human TG4 does not bind GTP as tested by GTP-agarose and BODIPY-FL-GTPγS binding, and its proteolytic activation by dispase or when expressed in AD-293 cells was not observed either. We identified several potential human TG4 glutamine donor substrates in the AD-293 cell extract by biotin-pentylamine incorporation and mass spectrometry. Several of these potential substrates are involved in cell-cell interaction, adhesion and proliferation, suggesting that human TG4 could become an anticancer therapeutic target.

Mammalian transglutaminases (TGs) catalyze calcium-dependent irreversible posttranslational modifications of proteins and their enzymatic activities contribute to the pathogenesis of several human neurodegenerative diseases. Although different transglutaminases are found in many different tissues, the TG6 isoform is mostly expressed in the CNS. The present study was embarked on/undertaken to investigate expression, distribution and activity of transglutaminases in Huntington disease transgenic rodent models, with a focus on analyzing the involvement of TG6 in the age- and genotype-specific pathological features relating to disease progression in HD transgenic mice and a tgHD transgenic rat model using biochemical, histological and functional assays. Our results demonstrate the physical interaction between TG6 and (mutant) huntingtin by co-immunoprecipitation analysis and the contribution of its enzymatic activity for the total aggregate load in SH-SY5Y cells. In addition, we identify that TG6 expression and activity are especially abundant in the olfactory tubercle and piriform cortex, the regions displaying the highest amount of mHTT aggregates in transgenic rodent models of HD. Furthermore, mHTT aggregates were colocalized within TG6-positive cells. These findings point towards a role of TG6 in disease pathogenesis via mHTT aggregate formation.

Microbial transglutaminase (MTGase) is an enzyme widely used in the dairy sector to improve the functional properties of protein-based products via the formation of a network between protein molecules. The aim of this study involving cheese from the milk of donkeys was to evaluate the effects of treatment with MTGase at the concentrations of 0 (control), 5, 8 and 10 U/g milk protein on the cheese-making process parameters, as well as the physical and chemical characteristics of the resulting cheese. MTGase influenced the time of gel formation from rennet addition (P < 0.05), with a delay at the two highest concentrations, accompanied by a lower (P < 0.01) pH of cheese and the lowest (P < 0.01) loss in cheese weight at 24 h of storage. The highest gel viscosity (P < 0.01) was observed at the highest concentration of the enzyme, reaching the value of 70 mPa⋅sec after 60 min. The chemical composition and color of the cheeses were not significantly affected by the inclusion of MTGase, regardless of the enzyme concentration. These findings may be of relevance in adapting the cheese-making process and might help in the design of new dairy products from donkey's milk.

Transglutaminase 2 (TG2) is a highly expressed mammalian enzyme whose biological function is unclear, although its catalytic activity in the small intestine appears necessary for celiac disease (CeD) pathogenesis. While TG2 activity is reversibly regulated by multiple allosteric mechanisms, their roles under fluctuating physiological conditions are not well understood. Here we demonstrate that extracellular TG2 activity is competitively controlled by the mutually exclusive binding of a high-affinity Ca(2+) ion or the formation of a strained disulfide bond. Binding of Ca(2+) at the high-affinity site does not activate TG2 per se, but it protects against oxidative enzyme deactivation while preserving the ability of Ca(2+) ions to occupy weaker binding sites capable of allosteric TG2 activation. In contrast, disulfide bond formation competitively occludes the high-affinity Ca(2+) site while resulting in complete TG2 inactivation. Because both outcomes are comparably favorable under typical extracellular conditions, subtle changes in the availability of redox catalysts or promoters in the extracellular matrix can dramatically alter steady-state TG2 activity. Thus, TG2 harbors a molecular “OR” gate that determines its catalytic fate upon export from cells.

Transglutaminase 2 (TG2) is a ubiquitously expressed enzyme catalyzing the crosslinking between Gln and Lys residues and involved in various pathophysiological events. Besides this crosslinking activity, TG2 functions as a deamidase, GTPase, isopeptidase, adapter/scaffold, protein disulfide isomerase, and kinase. It also plays a role in the regulation of hypusination and serotonylation. Through these activities, TG2 is involved in cell growth, differentiation, cell death, inflammation, tissue repair, and fibrosis. Depending on the cell type and stimulus, TG2 changes its subcellular localization and biological activity, leading to cell death or survival. In normal unstressed cells, intracellular TG2 exhibits a GTP-bound closed conformation, exerting prosurvival functions. However, upon cell stimulation with Ca2+ or other factors, TG2 adopts a Ca2+-bound open conformation, demonstrating a transamidase activity involved in cell death or survival. These functional discrepancies of TG2 open form might be caused by its multifunctional nature, the existence of splicing variants, the cell type and stimulus, and the genetic backgrounds and variations of the mouse models used. TG2 is also involved in the phagocytosis of dead cells by macrophages and in fibrosis during tissue repair. Here, we summarize and discuss the multifunctional and controversial roles of TG2, focusing on cell death/survival and fibrosis.

The method of tumor microenvironment (TME)-responsive aggregation has become a promising approach to enhance treatment effect by improving the accumulation of nanoparticles in tumors. The enzymatic cross-linking strategy has widely attracted attention owing to its good aggregation stability and biocompatibility. However, the enzymes in nontumor tissue can also catalyze the cross-linking reaction and reduce accumulation of nanoparticles in tumor. In this work, a "dual key"-responsive strategy is utilized to construct a transglutaminase (TGase)/pH-responsive radiosensitizer (Au@TAcoGal) with specific aggregation behavior in hepatic tumor cells. Au@TAcoGal can retain its stability in blood circulation (pH 7.4) even in the presence of TGase in plasma. On reaching tumor sites, it can be endocytosed by hepatoma cells by the active targeting of phenylboronic acid (PBA) and aggregated under acidity and overexpression of TGase in cells. Due to its specific accumulation in hepatoma cells, radiotherapy can be operated under a lower dose of X-ray. The results show that the cellular accumulation of Au@TAcoGal increases by 30-70%, and the cell survival rate is less than 25% under X-ray irradiation. The antineoplastic results show that Au@TAcoGal exhibits a higher therapeutic effect, and the tumor inhibition rate can reach 84.21%.

The changes in digestibility of TG-treated myofibrillar protein (MP), soybean protein isolate (SPI) and mixed proteins were evaluated by measuring liberation of primary amino groups, monitoring structural changes and investigating peptide fingerprints. TG treatment generally increased gastric digestion of treated proteins, possibly due to the structural changes occurred during TG treatment. In contrast, the initial intestinal digestion was suppressed by TG treatment. Compared with MP, the digestibility and peptide composition of SPI were affected by TG treatment to a larger degree, possibly due to the higher level of glutamine in SPI. Peptidomics analysis indicated that the changes in peptide composition of digests of TG-treated samples were related with the loss of Lys residues during TG treatment. Larger quantities of bioactive peptides KIEFEQFLPM, EVHEPEEKPRPK and TVKEDQVFPMNPPK were released after digestion of TG-treated MP. These results highlighted the complex and substantial influence of TG treatment on the digestibility of dietary proteins.

The classical neurotransmitter serotonin or 5-hydroxytryptamine (5-HT), synthesized from tryptophan, can be produced both centrally and peripherally. Through binding to functionally distinct receptors, serotonin is profoundly implicated in a number of fundamental physiological processes and pathogenic conditions. Recently, serotonin has been found covalently incorporated into proteins, a newly identified post-translational modification termed serotonylation. Transglutaminases (TGMs), especially TGM2, are responsible for catalyzing the transamidation reaction by transferring serotonin to the glutamine residues of target proteins. Small GTPases, extracellular matrix protein fibronectin, cytoskeletal proteins and histones are the most reported substrates for serotonylation, and their functions are triggered by this post-translational modification. This Review highlights the roles of serotonylation in physiology and diseases and provides perspectives for pharmacological interventions to ameliorate serotonylation for disease treatment.

Several environmental, genetic, and immune factors create a “perfect storm” for the development of coeliac disease: the antigen gluten, the strong association of coeliac disease with HLA, the deamidation of gluten peptides by the enzyme transglutaminase 2 (TG2) generating peptides that bind strongly to the predisposing HLA-DQ2 or HLA-DQ8 molecules, and the ensuing unrestrained T cell response. T cell immunity is at the center of the disease contributing to the inflammatory process through the loss of tolerance to gluten and the differentiation of HLA-DQ2 or HLA-DQ8-restricted anti-gluten inflammatory CD4+ T cells secreting pro-inflammatory cytokines and to the killing of intestinal epithelial cells by cytotoxic intraepithelial CD8+ lymphocytes. However, recent studies emphasize that the individual contribution of each of these cell subsets is not sufficient and that interactions between these different populations of T cells and the simultaneous activation of innate and adaptive immune pathways in distinct gut compartments are required to promote disease immunopathology. In this review, we will discuss how tissue destruction in the context of coeliac disease results from the complex interactions between gluten, HLA molecules, TG2, and multiple innate and adaptive immune components.

Background Terminally differentiated keratinocytes acquire corneocyte protein envelopes (CPE) complexed with corneocyte lipid envelopes (CLE). These two structural components of the corneocyte envelopes (CEs) undergo maturation by gaining in hydrophobicity, rigidity and surface area. Linoleoyl acylceramides are processed by 12R‐lipoxygenase (12R‐LOX) and other enzymes before transglutaminase (TG) attaches ω‐hydroxyceramides to involucrin in the CPE. Concurrently, structural proteins are cross‐linked by TG that has been activated by cathepsin D (CathD). Objectives The primary aim of this work was to demonstrate the impact of relative humidity (RH) during ex vivo CE maturation. Low, optimal and high RH were selected to investigate the effect of protease inhibitors (PIs) on CE maturation and TG activity; in addition, 12R‐LOX and CathD activity were measured at optimal RH. Finally, the effect of glycerol on ex vivo CE maturation was tested at low, optimal and high RH. Methods The first and ninth tape strip of photo‐exposed (PE) cheek and photo‐protected (PP) post‐auricular sites of healthy volunteers were selected. Ex vivo CE maturation was assessed via the relative CE maturity (RCEM) approach based on CE rigidity and hydrophobicity. The second and eighth tapes were exposed to RH in the presence of inhibitors. Results Irrespective of tape stripping depth, CEs from PE samples attained CE rigidity to the same extent as mature CEs from the PP site, but such improvement was lacking for CE hydrophobicity. 70% RH was optimal for ex vivo CE maturation. The inhibition of 12R‐LOX activity resulted in enhanced CE rigidity which was reduced by the TG inhibitor. CE hydrophobicity remained unchanged during ex vivo maturation in the presence of TG or 12R‐LOX inhibition. CE hydrophobicity was enhanced in the presence of glycerol at 44% RH and 100% RH but not at 70% RH. Furthermore, TG activity was significantly diminished at 100% RH compared to the commercial inhibitor LDN‐27219. However, a protease inhibitor mix reversed the negative effect of overhydration. Conclusion The study adds to the understanding of the roles of 12R‐LOX and TG activity in CE maturation and gives further insight into the effect of glycerol on the SC., A cocktail of protease inhibitor prior to ex vivo maturation shows a humidity‐dependent effect on TG activity with the biggest impact on samples ex vivo matured at 100% RH. Data are shown in mean ± SD (n = 6) with one‐way ANOVA with Holm–Sidak's post‐test; *P ≤ 0.05, **P ≤ 0.01 or ***P ≤ 0.001.