Analysis of epidermal-type transglutaminase (TGase 3) expression in mouse tissues and cell lines

Apelin-13 modulates the endometrial transcriptome of the domestic pig during implantation

BACKGROUND

The peri-implantation period is a critical time during pregnancy that mostly defines the overall litter size. Most authors agree that the highest percentage of embryo mortality occurs during this time. Despite the brevity of the peri-implantation period, it is the most dynamic part of pregnancy in which the sequential and uninterrupted course of several processes is essential to the animal's reproductive success. Also then, the maternal uterine tissues undergo an intensive remodelling process, and their energy demand dramatically increases. It is believed that apelin, a member of the adipokine family, is involved in the control of female reproductive functions in response to the current metabolic state. The verified herein hypothesis assumed the modulatory effect of apelin on the endometrial tissue transcriptome on days 15 to 16 of gestation (beginning of implantation).

RESULTS

The analysis of data obtained during RNA-seq (Illumina HiSeq2500) of endometrial slices treated and untreated with apelin (n = 4 per group) revealed changes in the expression of 68 genes (39 up-regulated and 29 down-regulated in the presence of apelin), assigned to 240 gene ontology terms. We also revealed changes in the frequency of alternative splicing events (397 cases), as well as single nucleotide variants (1,818 cases) in the presence of the adipokine. The identified genes were associated, among others, with the composition of the extracellular matrix, apoptosis, and angiogenesis.

CONCLUSIONS

The obtained results indicate a potential role of apelin in the regulation of uterine tissue remodelling during the peri-implantation period.

Transglutaminase 3 regulates cutaneous squamous carcinoma differentiation and inhibits progression via PI3K-AKT signaling pathway-mediated Keratin 14 degradation

Cutaneous squamous carcinoma is the second most common epithelial malignancy, associated with significant morbidity, mortality, and economic burden. However, the mechanisms underlying cSCC remain poorly understood. In this study, we identified TGM3 as a novel cSCC tumor suppressor that acts via the PI3K-AKT axis. RT-qPCR, IHC and western blotting were employed to assess TGM3 levels. TGM3-overexpression/knockdown cSCC cell lines were utilized to detect TGM3's impact on epithelial differentiation as well as tumor cell proliferation, migration, and invasion in vitro. Additionally, subcutaneous xenograft tumor models were employed to examine the effect of TGM3 knockdown on tumor growth in vivo. Finally, molecular and biochemical approaches were employed to gain insight into the tumor-suppressing mechanisms of TGM3. TGM3 expression was increased in well-differentiated cSCC tumors, whereas it was decreased in poor-differentiated cSCC tumors. Loss of TGM3 is associated with poor differentiation and a high recurrence rate in patients with cSCC. TGM3 exhibited tumor-suppressing activity by regulating cell proliferation, migration, and invasion both in vitro and in vivo. As a novel cSCC tumor differentiation marker, TGM3 expression was positively correlated with cell differentiation. In addition, our results demonstrated an interaction between TGM3 and KRT14 that aids in the degradation of KRT14. TGM3 deficiency disrupts keratinocytes differentiation, and ultimately leads to tumorigenesis. Furthermore, RNA-sequence analysis revealed that loss of TGM3 enhanced EMT via the PI3K-AKT signaling pathway. Deguelin, a PI3K-AKT inhibitor, blocked cSCC tumor growth induced by TGM3 knockdown in vivo. Taken together, TGM3 inhibits cSCC tumor growth via PI3K-AKT signaling, which could also serve as a tumor differentiation marker and a potential therapeutic target for cSCC. Proposed model depicted the mechanism by which TGM3 suppress cSCC development. TGM3 reduces the phosphorylation level of AKT and degrades KRT14. In the epithelial cell layer, TGM3 exhibits a characteristic pattern of increasing expression from bottom to top, while KRT14 and pAKT are the opposite. Loss of TGM3 leads to reduced degradation of KRT14 and activation of pAKT, disrupting keratinocyte differentiation, and eventually resulting in the occurrence of low-differentiated cSCC.

Transglutaminase 3 suppresses proliferation and cisplatin resistance of cervical cancer cells by inactivation of the PI3K/AKT pathway

Recent studies have shown that dysregulation of transglutaminase 3 (TGM3) is related to the aggressive progression of several cancer types. Our study aimed to determine the function of TGM3 in cervical cancer (CC) tumorigenesis. Gene expression profiles GSE63514, GSE9750, GSE46857 and GSE67522 were obtained from the Gene Expression Omnibus (GEO) database. Overlapping differential expressed genes (DEGs) in CC were screened using GEO2R online tool and Venn diagram software. The Kaplan-Meier plotter was used to determine overall survival. TGM3 expression was analyzed based on GEO and The Cancer Genome Atlas (TCGA) databases, qRT-PCR and western blot analyses. Cell proliferation was evaluated by CCK-8 and EdU incorporation assays. The half-maximal inhibitory concentration (IC50) value of cisplatin and cell apoptosis was assessed by CCK-8 and TUNEL assays, respectively. P-glycoprotein (P-gp) expression and the changes of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway were examined using western blot analysis. We identified 3 overlapping DEGs, including TGM3, glutathione peroxidase 3 (GPX3), and alpha B-crystallin (CRYAB), which were downregulated in CC tissues. TGM3 expression was reduced in CC cells and related to the poor prognosis of CC patients. TGM3 overexpression retarded the proliferation, reduced IC50 value of cisplatin, accelerated cisplatin-induced apoptosis, and inhibited cisplatin-induced P-gp level in CC cells. Furthermore, TGM3 overexpression suppressed the PI3K/Akt pathway in CC cells. Moreover, treatment with 740Y-P, a PI3K activator, abolished the effect of TGM3 overexpression on proliferation and cisplatin resistance in CC cells. In conclusion, overexpression of TGM3 suppressed proliferation and cisplatin resistance in CC cells by blocking the PI3K/Akt pathway.

Separate Gut Plasma Cell Populations Produce Auto-Antibodies against Transglutaminase 2 and Transglutaminase 3 in Dermatitis Herpetiformis

Dermatitis herpetiformis (DH) is an inflammatory skin disorder often considered as an extra intestinal manifestation of celiac disease (CeD). Hallmarks of CeD and DH are auto-antibodies to transglutaminase 2 (TG2) and transglutaminase 3 (TG3), respectively. DH patients have auto-antibodies reactive with both transglutaminase enzymes. Here it is reported that in DH both gut plasma cells and serum auto-antibodies are specific for either TG2 or TG3 with no TG2-TG3 cross reactivity. By generating monoclonal antibodies from TG3-specific duodenal plasma cells of DH patients, three conformational epitope groups are defined. Both TG2-specific and TG3-specific gut plasma cells have few immunoglobulin (Ig) mutations, and the two transglutaminase-reactive populations show distinct selection of certain heavy and light chain V-genes. Mass spectrometry analysis of TG3-specific serum IgA corroborates preferential usage of IGHV2-5 in combination with IGKV4-1. Collectively, these results demonstrate parallel induction of anti-TG2 and anti-TG3 auto-antibody responses involving separate B-cell populations in DH patients.

Antibody Responses to Transglutaminase 3 in Dermatitis Herpetiformis: Lessons from Celiac Disease

Dermatitis herpetiformis (DH) is the skin manifestation of celiac disease, presenting with a blistering rash typically on the knees, elbows, buttocks and scalp. In both DH and celiac disease, exposure to dietary gluten triggers a cascade of events resulting in the production of autoantibodies against the transglutaminase (TG) enzyme, mainly TG2 but often also TG3. The latter is considered to be the primary autoantigen in DH. The dynamics of the development of the TG2-targeted autoimmune response have been studied in depth in celiac disease, but the immunological process underlying DH pathophysiology is incompletely understood. Part of this process is the occurrence of granular deposits of IgA and TG3 in the perilesional skin. While this serves as the primary diagnostic finding in DH, the role of these immunocomplexes in the pathogenesis is unknown. Intriguingly, even though gluten-intolerance likely develops initially in a similar manner in both DH and celiac disease, after the onset of the disease, its manifestations differ widely.

Transglutaminase 3: The Involvement in Epithelial Differentiation and Cancer

Transglutaminases (TGMs) contribute to the formation of rigid, insoluble macromolecular complexes, which are essential for the epidermis and hair follicles to perform protective and barrier functions against the environment. During differentiation, epidermal keratinocytes undergo structural alterations being transformed into cornified cells, which constitute a highly tough outermost layer of the epidermis, the stratum corneum. Similar processes occur during the hardening of the hair follicle and the hair shaft, which is provided by the enzymatic cross-linking of the structural proteins and keratin intermediate filaments. TGM3, also known as epidermal TGM, is one of the pivotal enzymes responsible for the formation of protein polymers in the epidermis and the hair follicle. Numerous studies have shown that TGM3 is extensively involved in epidermal and hair follicle physiology and pathology. However, the roles of TGM3, its substrates, and its importance for the integument system are not fully understood. Here, we summarize the main advances that have recently been achieved in TGM3 analyses in skin and hair follicle biology and also in understanding the functional role of TGM3 in human tumor pathology as well as the reliability of its prognostic clinical usage as a cancer diagnosis biomarker. This review also focuses on human and murine hair follicle abnormalities connected with TGM3 mutations.

Transglutaminase 3 Reduces the Severity of Psoriasis in Imiquimod-Treated Mouse Skin

Four transglutaminase (TG) isoforms have been detected in epidermal keratinocytes: TG1, TG2, TG3, and TG5. Except for TG1 and TG3, their contribution to keratinocyte development and structure remains undefined. In this paper, we focused on the roles of TG2 and TG3 in imiquimod-induced psoriasis in mouse skin. We evaluated the severity of psoriasis markers in the skin of imiquimod-treated TG3 null and TG2 null mice. Our results showed that compromised TG3KO mouse skin was more responsive than WT or TG2KO mouse skin to the action of the pro-inflammatory drug imiquimod.

Transglutaminases: part I-origins, sources, and biotechnological characteristics

The transglutaminases form a large family of intracellular and extracellular enzymes that catalyze cross-links between protein molecules. Transglutaminases crosslinking properties are widely applied to various industrial processes, to improve the firmness, viscosity, elasticity, and water-holding capacity of products in the food and pharmaceutical industries. However, the extremely high costs of obtaining transglutaminases from animal sources have prompted scientists to search for new sources of these enzymes. Therefore, research has been focused on producing transglutaminases by microorganisms, which may present wider scope of use, based on enzyme-specific characteristics. In this review, we present an overview of the literature addressing the origins, types, reactions, and general characterizations of this important enzyme family. A second review will deal with transglutaminases applications in the area of food industry, medicine, pharmaceuticals and biomaterials, as well as applications in the textile and leather industries.

Characterization of Tissue Transglutaminase as a Potential Biomarker for Tissue Response toward Biomaterials

Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial-tissue interactions due to its presence and versatile functions in the extracellular environment. TGase 2 catalyzes the cross-linking of proteins through its Ca²⁺-dependent acyltransferase activity. Moreover, it enhances the interactions between fibronectin and integrins, which in turn mediates the adhesion, migration, and motility of the cells. TGase 2 is also a key player in the pathogenesis of fibrosis. In this study, we investigated whether TGase 2 is present at the biomaterial-tissue interface and might serve as an informative biomarker for the visualization of tissue response toward gelatin-based biomaterials. Two differently cross-linked hydrogels were used, which were obtained by the reaction of gelatin with lysine diisocyanate ethyl ester. The overall expression of TGase 2 by endothelial cells, macrophages, and granulocytes was partly influenced by contact to the hydrogels or their degradation products, although no clear correlation was evidenced. In contrast, the secretion of TGase 2 differed remarkably between the different cells, indicating that it might be involved in the cellular reaction toward gelatin-based hydrogels. The hydrogels were implanted subcutaneously in immunocompetent, hairless SKH1-Elite mice. Ex vivo immunohistochemical analysis of tissue sections over 112 days revealed enhanced expression of TGase 2 around the hydrogels, in particular at days 14 and 21 post-implantation. The incorporation of fluorescently labeled cadaverine derivatives for the detection of active TGase 2 was in accordance with the results of the expression analysis. The presence of an irreversible inhibitor of TGase 2 led to attenuated incorporation of the cadaverines, which verified the catalytic action of TGase 2. Our in vitro and ex vivo results verified TGase 2 as a potential biomarker for tissue response toward gelatin-based hydrogels. In vivo, no TGase 2 activity was detectable, which is mainly attributed to the unfavorable physicochemical properties of the cadaverine probe used.

Tissue and serum expression of TGM-3 may be prognostic marker in patients of oral squamous cell carcinoma undergoing chemo-radiotherapy

Radioresistance is one of the main determinants of treatment outcome in oral squamous cell carcinoma (OSCC), but its prediction is difficult. Several authors aimed to establish radioresistant OSCC cell lines to identify genes with altered expression in response to radioresistance. The development of OSCC is a multistep carcinogenic process that includes activation of several oncogenes and inactivation of tumour suppressor genes. TGM-3 is a tumour suppressor gene and contributes to carcinogenesis process. The aim of this study was to estimate serum and tissue expression of TGM-3 and its correlation with clinico-pathological factors and overall survival in patients of OSCC undergoing chemo-radiotherapy. Tissue expression was observed in formalin fixed tissue biopsies of 96 cases of OSCC and 32 healthy controls were subjected to immunohistochemistry (IHC) by using antibody against TGM-3 and serum level was estimated by ELISA method. mRNA expression was determined by using Real-Time PCR. Patients were followed for 2 year for chemo radiotherapy response. In OSCC, 76.70% cases and in controls 90.62% were positive for TGM-3 IHC expression. TGM-3 expression was cytoplasmic and nuclear staining expressed in keratinized layer, stratum granulosum and stratum spinosum in controls and tumour cells. Mean serum TGM-3 in pre chemo-radiotherapy OSCC cases were 1304.83±573.55, post chemo-radiotherapy samples were 1530.64±669.33 and controls were 1869.16±1377.36, but difference was significant in pre chemo-radiotherapy samples as compared to controls (p<0.018). This finding was also confirmed by real- time PCR analysis in which down regulation (-7.92 fold change) of TGM-3 in OSCC as compared to controls. TGM-3 expression was significantly associated with response to chemo-radiotherapy treatment (p<0.007) and overall survival (p<0.015). Patents having higher level of TGM-3 expression have good response to chemo-radiotherapy and also have better overall survival. TGM-3 may serve as a candidate biomarker for responsiveness to chemo-radiotherapy treatment in OSCC patients.

Expression of Transglutaminase in Foreskin of Children with Balanitis Xerotica Obliterans

Balanitis xerotica obliterans (BXO) is a chronic inflammatory skin disorder of unclear etiology. The etiology and the exact molecular mechanisms underlying the disease are still unknown. The human transglutaminase (TG) family consists of several proteins with catalytic activity essential for biological processes. In the present research we investigated the transcript levels of three TGs in patients operated on for congenital phimosis without or with histologically confirmed BXO; Thirty children with acquired phimosis were enrolled. The removed foreskins were sent both for histological diagnosis and for quantitative real-time PCR to evaluate the transcript levels of keratinocyte (TG1), tissue (TG2), and epidermal (TG3) transglutaminase; We observed a decrease in TG1 and TG3 transcripts by about 70% (p < 0.001) in foreskins from patients with BXO (n = 15) in comparison with patients without BXO (n = 15) and an increase in TG2 mRNA levels by 2.9 folds (p < 0.001); Reduced expression of both TG1 and TG3 was associated with the altered structure of the foreskin in BXO and can be a consequence of damage to keratinocytes. Increased expression of TG2 can be the result of chronic inflammation. TG2 overexpression can play a pivotal role in triggering and maintaining the inflammatory response in BXO patients.

The mouse wellhaarig (we) mutations result from defects in epidermal-type transglutaminase 3 (Tgm3)

The recessive wellhaarig (we) mutations, named for the wavy coat and curly whiskers they generate in homozygotes, have previously been mapped on mouse Chromosome 2. To further limit the possible location of the we locus, we crossed hybrid (C57BL/6×AKR)F1, we(4J)/+ females with AKR, we(4J)/we(4J) mutant males to create a large backcross family that was typed for various microsatellite markers and single-nucleotide polymorphisms (SNPs) that distinguish strains AKR and B6. This analysis restricted the location of we(4J) between sites that flank only one gene known to be expressed in skin: epidermal-type transglutaminase 3 (Tgm3). To test Tgm3 as a candidate for the basis of the wellhaarig phenotype we took two approaches. First, we sequenced all Tgm3 coding regions in mice homozygous for four independent, naturally-occurring wellhaarig alleles (we, we(Bkr), we(3J) and we(4J)) and found distinct defects in three of these mutants. Second, we crossed mice homozygous for an induced mutant allele of Tgm3 (Tgm3(Btlr)) with mice heterozygous for one of the wellhaarig alleles we possess (we(4J) or we(Bkr)) to test for complementation. Because the progeny inheriting both a recessive we allele and a recessive Tgm3(Btlr) allele displayed wavy hair, we conclude that the classic wellhaarig mutations result from defects in Tgm3.

Distribution of transglutaminase family members in mouse whole body sections

Transglutaminases (TGs) comprise a protein family in which the members catalyze the formation of isopeptide bonds between glutamine and lysine residues in various proteins. Eight enzymes have been identified and designated as factor XIII (FXIII) and TG1-7. Expression studies of four major members, i.e., FXIII, TG1, TG2, and TG3, have been performed in a relatively large number of mammalian tissues in comparison with those on the other isozymes. The structural and biochemical characteristics of these individual isozymes and expression analyses of TG family in some tissue extracts have been reported, but there have been no simultaneous comparative analyses of both their mRNA and protein expression patterns in tissues distributions. Thus, we developed novel experimental systems for in situ hybridization using cryofilm attached to whole body sections of neonatal mice, thereby obtaining data regarding the tissue distributions of the major TG isozymes. In this study, we performed the first detailed comparative analysis of the mRNA and protein distribution studies of TG family members in a wide range of mouse tissues. These data will be helpful for elucidating the unknown physiological and pathological functions of TGs.

The UVB-Stimulated Expression of Transglutaminase 1 Is Mediated Predominantly via the NFκB Signaling Pathway: New Evidence of Its Significant Attenuation through the Specific Interruption of the p38/MSK1/NFκBp65 Ser276 Axis

The influence of ultraviolet B (UVB) radiation on transglutaminase 1 (TGase 1), a major factor that regulates skin keratinization, has not been sufficiently characterized especially at the gene or protein level. Thus, we determined whether UVB affects the expression of TGase 1 in human keratinocytes and clarified the intracellular stress signaling mechanism(s) involved. Exposure of human keratinocytes to UVB significantly up-regulated the expression of TGase 1 at the gene and protein levels. Treatment with inhibitors of p38, MEK, JNK or NFκB significantly abolished the UVB-stimulated protein expression of TGase 1. Treatment with astaxanthin immediately after UVB irradiation did not attenuate the increased phosphorylation of Ser536/Ser468NFκBp65, c-Jun, ATK-2 and CK2, and did not abrogate the increased or diminished protein levels of c-Jun/c-Fos or I-κBα, respectively. However, the same treatment with astaxanthin significantly abolished the UVB-stimulated expression of TGase 1 protein, which was accompanied by the attenuated phosphorylation of Thr565/Ser376/Ser360MSK1, Ser276NFκBp65 and Ser133CREB. The MSK1 inhibitor H89 significantly down-regulated the increased protein expression of TGase 1 in UVB-exposed human keratinocytes, which was accompanied by an abrogating effect on the increased phosphorylation of Ser276NFκBp65 and Ser133CREB but not Thr565/Ser376/Ser360MSK1. Transfection of human keratinocytes with MSK1 siRNA suppressed the UVB-stimulated protein expression of TGase 1. These findings suggest that the UVB-stimulated expression of TGase 1 is mediated predominantly via the NFκB pathway and can be attenuated through a specific interruption of the p38/MSK1/NFκBp65Ser276 axis.

Differential expression of transglutaminase genes in patients with chronic periodontitis

OBJECTIVE

Gingival epithelium plays a key role in the protection of oral tissues from microbial challenge, especially during the periodontal disease. This study was aimed to evaluate levels of mRNA transcripts of different forms of transglutaminase in the human gingival tissues from patients with chronic periodontitis and relative controls.

SUBJECTS AND METHODS

This study included 22 patients with chronic periodontitis (CP) and 22 healthy controls. For each patient, the values of probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP) were recorded. Gene expression of transglutaminase 1, transglutaminase 2, transglutaminase 3, and metalloprotease 2 was evaluated by real-time PCR, while that of Factor XIIIA and metalloprotease 9 by RT-PCR.

RESULTS

The values of all the clinical parameters were significantly higher in the CP group than in the healthy control group (P < 0.05). In the CP group, the mRNA expression of transglutaminase 1 and transglutaminase 3 was significantly decreased in comparison with healthy control group. A slight nonsignificant changes of transglutaminase 2 gene expression were observed in samples from CP patients in comparison with controls.

CONCLUSIONS

These observations suggest that transglutaminase gene expression may be modified in response to chronic injury in the damaged gingival and emphasizes the key role of these enzymes in gingival remodelling/healing and adaptive processes.

Functional amyloids in the mouse sperm acrosome

The acrosomal matrix (AM) is an insoluble structure within the sperm acrosome that serves as a scaffold controlling the release of AM-associated proteins during the sperm acrosome reaction. The AM also interacts with the zona pellucida (ZP) that surrounds the oocyte, suggesting a remarkable stability that allows its survival despite being surrounded by proteolytic and hydrolytic enzymes released during the acrosome reaction. To date, the mechanism responsible for the stability of the AM is not known. Our studies demonstrate that amyloids are present within the sperm AM and contribute to the formation of an SDS- and formic-acid-resistant core. The AM core contained several known amyloidogenic proteins, as well as many proteins predicted to form amyloid, including several ZP binding proteins, suggesting a functional role for the amyloid core in sperm-ZP interactions. While stable at pH 3, at pH 7, the sperm AM rapidly destabilized. The pH-dependent dispersion of the AM correlated with a change in amyloid structure leading to a loss of mature forms and a gain of immature forms, suggesting that the reversal of amyloid is integral to AM dispersion.

Transglutaminase regulation of cell function

Transglutaminases (TGs) are multifunctional proteins having enzymatic and scaffolding functions that participate in regulation of cell fate in a wide range of cellular systems and are implicated to have roles in development of disease. This review highlights the mechanism of action of these proteins with respect to their structure, impact on cell differentiation and survival, role in cancer development and progression, and function in signal transduction. We also discuss the mechanisms whereby TG level is controlled and how TGs control downstream targets. The studies described herein begin to clarify the physiological roles of TGs in both normal biology and disease states.

Immunological Detection of Proteolytically Activated Epidermal-type Transglutaminase (TGase 3) Using Cleavage-site-specific Antibody

Transglutaminase 3 (TGase 3), involved in the cross-linking of structural proteins in the epidermis, is activated by limited proteolysis of zymogen into two fragments during keratinocyte differentiation. Using recombinant TGase 3, the N-terminus sequence of the proteolyzed fragment was analyzed. Antibody against the synthetic peptide corresponding to the cleavage site specifically detected the fragment in the mouse forestomach extract.

TGM3, a candidate tumor suppressor gene, contributes to human head and neck cancer

BACKGROUND

In our previous study using oligonucleotide microarrays, we revealed that transglutaminase 3 (TGM3) was remarkably down-regulated in head and neck cancer (HNC). However, the potential of TGM3 as a useful biomarker or molecular target for HNC is unclear.

METHODS

The transcriptional and post-translational status of TGM3 in HNC cell lines and specimens was detected using real-time PCR and western blot analysis. Bisulfate-treated DNA sequencing was used to analyze the molecular mechanism of TGM3 gene silencing. In addition, the effects of TGM3 on the proliferation, colony formation and induction of apoptosis in vitro and tumorigenicity in vivo were investigated through exogenous expression of TGM3 in HNC cells. Immunohistochemistry was used to evaluate TGM3 expression in large HNC samples.

RESULTS

TGM3 was down-regulated in HNC samples and cell lines (P < 0.0001). The hypermethylation of a promoter CpG island was one of the mechanisms of silencing the TGM3 gene in HNC. Exogenous expression of TGM3 in HNC cells could inhibit the proliferation and enhance the apoptosis of HNC cells in vitro and suppress tumor growth in vivo. In addition, TGM3 protein levels were strongly associated with the pathological differentiation of HNC tissues (P = 0.0037). Survival analysis revealed that low TGM3 expression was associated with worse overall survival (P = 0.0002), and TGM3 expression level was an independent predictor in patients with HNC.

CONCLUSIONS

The studies prove that TGM3, as a candidate tumor suppressor, contributes to the carcinogenesis and development of HNC and may serve as a useful biomarker for patients with HNC.

Reduced inflammatory threshold indicates skin barrier defect in transglutaminase 3 knockout mice

Recently, a transglutaminase 3 knockout (TGM3/KO) mouse was generated that showed impaired hair development, but no gross defects in the epidermal barrier, although increased fragility of isolated corneocytes was demonstrated. Here we investigated the functionality of skin barrier in vivo by percutaneous sensitization to FITC in TGM3/KO (n=64) and C57BL/6 wild-type (WT) mice (n=36). Cutaneous inflammation was evaluated by mouse ear swelling test (MEST), histology, serum IgE levels, and by flow cytometry from draining lymph nodes. Inflammation-induced significant MEST difference (P<0.0001) was detected between KO and WT mice and was supported also by histopathology. A significant increase of CD4+ CD25+-activated T cells (P<0.01) and elevated serum IgE levels (P<0.05) in KO mice indicated more the development of FITC sensitization than an irritative reaction. Propionibacter acnes-induced intracutaneous inflammation showed no difference (P=0.2254) between the reactivity of WT and KO immune system. As in vivo tracer, FITC penetration from skin surface followed by two-photon microscopy demonstrated a more invasive percutaneous penetration in KO mice. The clinically uninvolved skin in TGM3/KO mice showed impaired barrier function and higher susceptibility to FITC sensitization indicating that TGM3 has a significant contribution to the functionally intact cutaneous barrier.

Epidermal transglutaminase (TGase 3) is required for proper hair development, but not the formation of the epidermal barrier

Transglutaminases (TGase), a family of cross-linking enzymes present in most cell types, are important in events as diverse as cell-signaling and matrix stabilization. Transglutaminase 1 is crucial in developing the epidermal barrier, however the skin also contains other family members, in particular TGase 3. This isoform is highly expressed in the cornified layer, where it is believed to stabilize the epidermis and its reduction is implicated in psoriasis. To understand the importance of TGase 3 in vivo we have generated and analyzed mice lacking this protein. Surprisingly, these animals display no obvious defect in skin development, no overt changes in barrier function or ability to heal wounds. In contrast, hair lacking TGase 3 is thinner, has major alterations in the cuticle cells and hair protein cross-linking is markedly decreased. Apparently, while TGase 3 is of unique functional importance in hair, in the epidermis loss of TGase 3 can be compensated for by other family members.

[Dermatitis herpetiformis: a review]

BACKGROUND

Dermatitis herpetiformis (DH) is a rare auto-immune bullous disease characterized by its almost constant association to gluten sensitivity.

OBJECTIVE

Review of literature about epidemiology, physiopathology, clinical data and treatment of DH.

METHODS

Research on Medline and Embase database without any time limit until April 2010. Because of the lack of randomized therapeutic trials in DH, retrospective series and case reports have been analyzed.

RESULTS

DH is related to auto-antibodies against epidermal transglutaminase, which belongs to the same family as tissue transglutaminase, the auto-antigen of celiac disease. Physiopathology is complex, occurring in HLA DQ2 or DQ8 predisposed patients, and implies gluten, immunological reaction in the intestinal wall then in the skin. DH and celiac disease may be encountered in the same family. DH is characterized by a very pruritic microvesicular eruption typically located on elbows, knees and buttocks. Digestive manifestations of celiac disease occur in 15% of cases. Direct immunofluorescence is necessary to confirm the diagnosis, showing granular IgA±C3 deposits in the papillary dermis. Circulating IgA and IgG antiendomysium and antitransglutaminase antibodies are detected in almost all patients at the acute phase and follow the clinical course of the disease. Gastro-intestinal endoscopy with multiple duodenal biopsies shows partial or complete villous atrophy in two thirds of cases, intraepithelial lymphocyte infiltrate in the other cases. Other auto-immune diseases may be associated in 10-20% of cases. The main long-term risk is the occurrence of T or B nodal or intestinal tract lymphoma in 2% of cases (relative risk close to 6 in several studies, but not admitted by all authors), especially if adherence to gluten-free diet is not strict. Treatment is based on dapsone, which is quickly efficient on cutaneous manifestations, but not on the digestive involvement and on strict and definitive gluten-free diet, which cures villous atrophy and reduces the risk of lymphoma.

CONCLUSION

DH is associated to a gluten enteropathy and its physiopathology is better known. Even if the risk of secondary lymphoma seems little, most of the authors recommend a definitive gluten-free diet.

Quantitative proteomics using formalin-fixed paraffin-embedded tissues of oral squamous cell carcinoma

Clinical proteomics using a large archive of formalin-fixed paraffin-embedded (FFPE) tissue blocks has long been a challenge. Recently, a method for extracting proteins from FFPE tissue in the form of tryptic peptides was developed. Here we report the application of a highly sensitive mass spectrometry (MS)-based quantitative proteome method to a small amount of samples obtained by laser microdissection from FFPE tissues. Cancerous and adjacent normal epithelia were microdissected from FFPE tissue blocks of 10 squamous cell carcinomas of the tongue. Proteins were extracted in the form of tryptic peptides and analyzed by 2-dimensional image-converted analysis of liquid chromatography and mass spectrometry (2DICAL), a label-free quantitative proteomics method developed in our laboratory. From a total of 25 018 peaks we selected 72 mass peaks whose expression differed significantly between cancer and normal tissues (P < 0.001, paired t-test). The expression of transglutaminase 3 (TGM3) was significantly down-regulated in cancer and correlated with loss of histological differentiation. Hypermethylation of TGM3 gene CpG islands was observed in 12 oral squamous cell carcinoma (OSCC) cell lines with reduced TGM3 expression. These results suggest that epigenetic silencing of TGM3 plays certain roles in the process of oral carcinogenesis. The method for quantitative proteomic analysis of FFPE tissue described here offers new opportunities to identify disease-specific biomarkers and therapeutic targets using widely available archival samples with corresponding detailed pathological and clinical records.

The cystatin M/E-controlled pathway of skin barrier formation: expression of its key components in psoriasis and atopic dermatitis

BACKGROUND

The antiprotease activity of cystatin M/E regulates skin barrier formation, as it inhibits the activity of cathepsin V, cathepsin L and legumain, thereby controlling the processing of transglutaminase 3. Misregulation of this pathway by unrestrained protease activity, as seen in cystatin M/E-deficient mice, leads to abnormal stratum corneum and hair follicle formation, and severe disturbance of skin barrier function.

OBJECTIVES

Our major aim was to make a quantitative analysis of the expression of all players of this pathway in the epidermis of patients with inflammatory skin diseases. A second aim was to determine if reconstructed human skin could be used as an in vitro model system to investigate this pathway.

METHODS

Autopsy material from normal human tissues, biopsies from normal skin of healthy volunteers, and lesional skin from patients with atopic dermatitis and psoriasis were used to study the expression of the above-mentioned molecules at the mRNA level by quantitative real-time polymerase chain reaction. Localization of the protein was performed by immunofluorescence microscopy, and expression was quantitated by image analysis.

RESULTS

In skin, cystatin M/E is expressed at relatively higher levels than its target proteases, when compared with other tissues, which emphasizes its prominent role in cutaneous biology. We found decreased expression of cystatin M/E and cathepsin V in lesional atopic dermatitis and psoriasis epidermis at the mRNA level as well as the protein level. Cathepsin L and transglutaminase 3 were increased at the transcriptional level; however, this was not reflected by higher protein levels. Interestingly, the expression of all these molecules in reconstructed skin was qualitatively and quantitatively similar to the in vivo situation.

CONCLUSIONS

Disturbance of the cystatin M/E-cathepsin pathway could contribute to the dysregulated skin barrier function observed in inflammatory dermatoses. Human reconstructed skin appears to be a valuable model to study this novel biochemical pathway in vitro.

Transglutaminase activity regulates osteoblast differentiation and matrix mineralization in MC3T3-E1 osteoblast cultures

Transglutaminase (TG) enzymes and protein crosslinking have long been implicated in the formation of mineralized tissues. The aim of this study was to analyze the expression, activity and function of TGs in differentiating osteoblasts to gain further insight into the role of extracellular matrix protein crosslinking in bone formation. MC3T3-E1 (subclone 14) pre-osteoblast cultures were treated with ascorbic acid and beta-glycerophosphate to induce cell differentiation and matrix mineralization. Expression of TG isoforms was analyzed by RT-PCR. TG activity was assessed during osteoblast differentiation by in vitro biochemical assays and by in situ labeling of live cell cultures. We demonstrate that MC3T3-E1/C14 osteoblasts express two TG isoforms--TG2 and FXIIIA. Abundant TG activity was observed during cell differentiation which increased significantly after thrombin treatment, a result confirming the presence of FXIIIA in the cultures. Ascorbic acid treatment, which stimulated collagen secretion and assembly, also stimulated externalization of TG activity, likely from FXIIIA which was externalized upon this treatment as analyzed by immunofluoresence microscopy. Inhibition of TG activity in the cultures by cystamine resulted in complete abrogation of mineralization, attributable to decreased matrix accumulation and an arrested state of osteoblast differentiation as measured by decreased levels of bone sialoprotein, osteocalcin and alkaline phosphatase. Additional functional studies and substrate characterization showed that TG activity was required for the formation of a fibronectin-collagen network during the early stages of matrix formation and assembly. This network, in turn, appeared to be essential for further matrix production and progression of the osteoblast differentiation program, and ultimately for mineralization.

Proteomic analysis of global alteration of protein expression in squamous cell carcinoma of the esophagus

Squamous cell carcinoma of the esophagus (ESCC), a major subtype of esophageal carcinoma, is one of the aggressive cancers with worst prognosis in the world. The dismal outcome of ESCC is attributed to multiple reasons including its aggressive nature, largely unknown molecular mechanism of its progression, and the lack of biomarkers for early detection and effective prediction of its clinical behavior. To identify proteins with prognostic and/or predictive value, we applied a proteomics strategy to quantify proteins differentially expressed in ESCC using matched samples of carcinoma and adjacent normal epithelial cells. The analysis led to identification of 28 proteins aberrantly expressed in cancer cells with changes of at least three-fold in ESCC relative to normal squamous epithelial cells. These changes represent functional alterations of essential proteins for normal cellular physiology, accounting for many cellular changes involved in development of ESCC, including cell transformation, loss of differentiation, tumor growth, apoptosis, tumor invasion, and cell metabolism. The differentially expressed proteins shed new insights on the mechanism of tumorigenesis and provide candidate biomarkers for early detection of ESCC.

Tissue transglutaminase during mouse central nervous system development: lack of alternative RNA processing and implications for its role(s) in murine models of neurotrauma and neurodegeneration

Tissue transglutaminase (tTG) is a member of a multigene family principally involved in catalyzing the formation of protein cross-links. Unlike other members of the transglutaminase family, tTG is multifunctional since it also serves as a guanosine triphosphate (GTP) binding protein (Galpha(h)) and participates in cell adhesion. Different isoforms of tTG can be produced by proteolysis or alternative splicing. We find that tTG mRNA is expressed at low levels in the mouse CNS relative to other tissues, and at lower levels in the CNS of mouse in comparison to that of human or rat. tTG mRNA levels are higher in the heart compared to the CNS, for example, and much higher in the liver. Within the CNS, tTG message is lowest in the adult cerebellum and thalamus and highest in the frontal cortex and striatum. In the hippocampus, tTG expression is highest during embryonic development and falls off dramatically after 1 week of life. We did not find alternative splicing of the mouse tTG. At the protein level, the predominant isoform is approximately 62 kDa. In summary, tTG, an important factor in neuronal survival, is expressed at low levels in the mouse CNS and, unlike rat and human tTG, does not appear to be regulated by alternative splicing. These findings have implications for analyses of rodent tTG expression in human neurodegenerative and neurotrauma models where alternative processing may be an attractive pathogenetic mechanism. They further impact on drug discovery paradigms, where modulation of activity may have therapeutic value.

Transglutaminase 3 expression in C57BL/6J mouse embryo epidermis and the correlation with its differentiation

Epidermal-type transglutaminase 3 (TGM3) is involved in the cross-linking of structural proteins to form the cornified envelope in the epidermis. In the present study, we detected the expression of TGM3 in the mouse embryo using RT-PCR. TGM3 mRNA is weakly presented from E11.5 to E14.5 and increases significantly from E15.5 to birth. Then we determined the spatial and temporal expression pattern of TGM3 in the skin and other organs by in situ hybridization. We found a deprivation of TGM3 in skin at E11.5, while a rich supply in periderm cells and a weak expression in basal cells from E12.5 to E14.5. From the period of E15.5 to E16.5, after keratinization in the epidermis, TGM3 was expressed in the granular and cornified layers. The electron microscopic observation of the C57BL/6J mouse limb bud skin development provided several morphological evidences for the epidermal differentiation. The above findings suggest that the expression of TGM3 plays a important role in the epidermis differentiation in embryogenesis.

The emerging structural understanding of transglutaminase 3

Transglutaminases (TGase; protein-glutamine: amine gamma-glutamyl-transferase) are a family of calcium-dependent acyl-transfer enzymes ubiquitously expressed in mammalian cells and responsible for catalyzing covalent cross-links between proteins or peptides. A series of recent crystal structures have revealed the overall architecture of TGase enzymes, and provided a deep look at their active site, calcium and magnesium ions, and the manner by which guanine nucleotides interact with this enzyme. These structures, backed with extensive biochemical studies, are providing new insights as to how access to the enzyme's active site may be gated through the coordinated changes in cellular calcium and magnesium concentrations and GTP/GDP. Calcium-activated TGase 3 can bind, hydrolyze, and is inhibited by GTP, despite lacking structural homology with other GTP binding proteins. A structure based sequence homology among the TGase enzyme family shows that these essential structural features are shared among other members of the TGase family.

Developmental regulation of tissue transglutaminase in the mouse forebrain

Tissue transglutaminase (tTG) is a multifunctional enzyme that catalyzes both transamidation and GTPase reactions. In cell culture models tTG-mediated transamidation positively regulates many processes that occur in vivo during the mammalian brain growth spurt (BGS), including neuronal differentiation, neurite outgrowth, synaptogenesis and cell death mechanisms. However, little is known about the levels of tTG expression and transglutaminase (TG) activity during mammalian brain development. In this study, C57BL/6 mouse forebrains were collected at embryonic day (E) 12, E14, E17, postnatal day (P) 0, P7 and P56 and analyzed for tTG expression and TG activity. RT-PCR analysis demonstrated that tTG mRNA content increases during mouse forebrain development, whereas immunoblot analysis demonstrated that tTG protein content decreases during this time. TG activity was low in prenatal mouse forebrain but increased fivefold to peak at P0, which corresponds with the beginning of the mouse BGS. Further analysis demonstrated that the lack of temporal correlation between tTG protein content and TG activity is the result of an endogenous inhibitor of tTG that is present in prenatal but not postnatal mouse forebrain. These results demonstrate for the first time that tTG enzymatic activity in the mammalian forebrain is developmentally regulated by post-translational mechanisms.

Dermatitis herpetiformis: close to unravelling a disease

Dermatitis herpetiformis is characterised by granular IgA precipitates in the papillary dermis. In contrast to other autoimmune blistering diseases, where tissue-deposited and circulating autoantibodies recognise the same target within the skin, in dermatitis herpetiformis a serum IgA reacting with a component of the healthy papillary dermis has not been detected. Recently, the antigenic specificity of pathognomic skin-bound IgA has been clarified: the immune precipitates contain epidermal transglutaminase, an enzyme not previously detected in the papillary region of normal skin. Furthermore, serum IgA in dermatitis herpetiformis has been found to bind epidermal transglutaminase. These findings may relate to the fact, that dermatitis herpetiformis is associated with gluten sensitive enteropathy, coeliac disease, which is characterised by IgA type autoantibodies to a closely related enzyme, tissue transglutaminase. The two transglutaminases are highly homologous, and therefore, cross reactivity of the two antibodies might explain why patients with gluten sensitive enteropathy, with or without skin disease, generally have serum autoantibodies to both enzymes. There is growing evidence that dermatitis herpetiformis should be considered as the skin manifestation of gluten sensitivity developing in those patients with mild coeliac disease, who produce epidermal transglutaminase autoantibodies of high avidity and affinity. Both the skin and the small bowel diseases are gluten dependent and are strongly associated with HLA DQ with no genetic differences to explain the two phenotypes. The question should be asked whether the rash in dermatitis herpetiformis is a classic autoimmune blistering disease or whether it has an immune complex basis, which is the most likely alternative.

Validity of mouse models for the study of tissue transglutaminase in neurodegenerative diseases

Tissue transglutaminase (tTG) is a multifunctional enzyme that catalyzes peptide cross-linking and polyamination reactions, and also is a signal-transducing GTPase. tTG protein content and enzymatic activity are upregulated in the brain in Huntington's disease and in other neurological diseases and conditions. Since mouse models are currently being used to study the role of tTG in Huntington's disease and other neurodegenerative diseases, it is critical that the level of its expression in the mouse forebrain be determined. In contrast to human forebrain where tTG is abundant, tTG can only be detected in mouse forebrain by immunoblotting a GTP-binding-enriched protein fraction. tTG mRNA content and transamidating activity are approximately 70% lower in mouse than in human forebrain. However, tTG contributes to the majority of transglutaminase activity within mouse forebrain. Thus, although tTG is expressed at lower levels in mouse compared with human forebrain, it likely plays important roles in neuronal function.

Analysis of epidermal-type transglutaminase (transglutaminase 3) in human stratified epithelia and cultured keratinocytes using monoclonal antibodies

BACKGROUND

Epidermal-type transglutaminase (TGase 3) is involved in the cross-linking of structural proteins in the epidermis, which results in the formation of the cornified envelope. TGase 3 is activated by limited proteolysis of a 77 kDa zymogen during keratinocyte differentiation.

OBJECTIVE

To characterize the expression of TGase 3 in human epidermis and cultured keratinocytes, we established specific monoclonal antibodies against the TGase 3.

METHODS

Recombinant proteins for human TGase 3 produced in bacteria and baculovirus-infected insect cells were purified as an antigen. Hybridomas are established and used for characterization of expression in epidermis and keratinocytes.

RESULTS

Four antibodies were generated against recombinant human TGase 3, which reacted with the 77 kDa zymogen and in some cases either the 47 or 30 kDa active proteolytic fragments. In human epidermis and cultured keratinocytes, only the zymogen form of TGase 3 was detected. Immunohistochemical analysis of the skin revealed that the enzyme is present in the cells of the granular and cornified layers consistent with its role in cornified envelope formation. In cultured keratinocytes, TGase 3 was expressed in differentiating cells coincident with profilaggrin and keratin 10 expressions.

CONCLUSION

Using monoclonal antibody against human TGase 3, we showed the expression of TGase 3 in upper layers of epidermis. TGase 3 displayed a diffuse cytoplasmic distribution in vitro consistent with its proposed role in the early phase of cornified cell envelope assembly in the cytoplasm.

Epidermal transglutaminase (TGase 3) is the autoantigen of dermatitis herpetiformis

Gluten sensitivity typically presents as celiac disease, a common chronic small intestinal disorder. However, in certain individuals it is associated with dermatitis herpetiformis, a blistering skin disease characterized by granular IgA deposits in the papillary dermis. While tissue transglutaminase has been implicated as the major autoantigen of gluten sensitive disease, there has been no explanation as to why this condition appears in two distinct forms. Here we show that while sera from patients with either form of gluten sensitive disease react both with tissue transglutaminase and the related enzyme epidermal (type 3) transglutaminase, antibodies in patients having dermatitis herpetiformis show a markedly higher avidity for epidermal transglutaminase. Further, these patients have an antibody population specific for this enzyme. We also show that the IgA precipitates in the papillary dermis of patients with dermatitis herpetiformis, the defining signs of the disease, contain epidermal transglutaminase, but not tissue transglutaminase or keratinocyte transglutaminase. These findings demonstrate that epidermal transglutaminase, rather than tissue transglutaminase, is the dominant autoantigen in dermatitis herpetiformis and explain why skin symptoms appear in a proportion of patients having gluten sensitive disease.