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Extended structure-mediated activation mechanism of transglutaminase 2 (TG2). a The closed, inactive form of TG2. The catalytic triad, comprising C277, H335, and D358, is buried in TG2. b The extended, active form of TG2. In the opened state, the catalytic nucleophile (C277) is exposed on the surface of TG2. c The location of the active site in the opened and closed forms of TG2. Red-rectangles indicate the active site. Gray ribbon structure and blue surface structure indicated opened and closed form of TG2, respectively. d The binding pocket of a covalently attached inhibitor. The structural study of the complex of TG2 with the covalently attached inhibitor showed that the substrate-binding pocket is relatively flat at one side, although opposite side is well-defined, compared with other enzyme in this families. (Color figure online)
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Transglutaminase 2 (TG2) is a multi-functional protein that has both protein cross-linking and guanosine 5′-triphosphate (GTP) hydrolysis activities. The activities of this protein are controlled by many cellular factors, including calcium (Ca²⁺) and GTP, and have been implicated in several physiological activities, including apoptosis, angiogenesi...
Citations
... TGM2 modulates biological events such as cell survival, differentiation and tumor formation, via multiple enzymatic activities including cross-linking, guanosine 5′-triphosphate (GTP) hydrolysis, scaffolding, protein disulfide isomerization, serotonylation (Farrelly et al., 2019) and protein kinase activity (Greenberg et al., 1991;Nakaoka et al., 1994;Eckert et al., 2014). Notably, Ca 2+ -dependent protein cross-linking activity is one of the main functions of TGM2 and can be negatively regulated by GTP (Lee et al., 2017). TGM2 is a promising drug target considering its important roles in cancer. ...
Transglutaminase 2 (TGM2) is a versatile enzyme that modulates cell survival and differentiation. However, its role in terminal erythroid differentiation is poorly understood. In this study, we investigated the function of TGM2 in primary fetal liver erythroid differentiation. We predicted TGM2 as an upstream regulator via ingenuity pathway analysis (IPA), and found that its expression was increased at both RNA and protein level during terminal erythroid differentiation. TGM2 cross-linking activity inhibitors GK921 and Z-DON suppressed erythroid maturation and enucleation, while its GTPase inhibitor LDN27219 had no such effect. Z-DON treatment arrested differentiation at basophilic erythroblast stage, and interfered with cell cycle progression. RT-PCR demonstrated decreased GATA-1 and KLF1, and disarranged cyclin, CDKI and E2F family genes expression after Z-DON treatment. In conclusion, TGM2 regulates terminal erythroid differentiation through its cross-linking enzyme activity.
... Keratinocyte TG (or TG1) has been detected in the skin epidermis, brain, and myocardial and vascular endothelial cells [10,11]. Tissue TG (TG2), the most studied and ubiquitously expressed TG isoform, is found in diverse types of tissues and cells, including cardiac endothelial cells and fibroblasts, vascular smooth muscle cells, monocytes, and macrophages [12][13][14]. In addition to its transamidase (cross-linking) activity, this multifunctional protein regulates numerous cellular functions such as growth, differentiation, migration, adhesion, survival, apoptosis, and angiogenesis [12][13][14][15]. ...
... Tissue TG (TG2), the most studied and ubiquitously expressed TG isoform, is found in diverse types of tissues and cells, including cardiac endothelial cells and fibroblasts, vascular smooth muscle cells, monocytes, and macrophages [12][13][14]. In addition to its transamidase (cross-linking) activity, this multifunctional protein regulates numerous cellular functions such as growth, differentiation, migration, adhesion, survival, apoptosis, and angiogenesis [12][13][14][15]. A growing body of evidence shows that TG2 is pivotal to the development of cardiac diseases such as myocardial hypertrophy, myocardial infraction and heart failure through its suspected involvement in cardiac fibrosis signalling processes [16]. ...
Transglutaminase (TG) isoforms control diverse normal and pathophysiologic processes through their capacity to cross-link extracellular matrix (ECM) proteins. Their functional and signalling roles in cardiac fibrosis remain poorly understood, despite some evidence of TG2 involvement in abnormal ECM remodelling in heart diseases. In this study, we investigated the role of TG1 and TG2 in mediating fibrotic signalling, collagen cross-linking, and cell proliferation in healthy fibroblasts by siRNA-mediated knockdown. siRNA for TG1, TG2 or negative control was transfected into cultured neonatal rat ventricular fibroblasts and cardiomyocytes. mRNA expression of TGs and profibrotic, proliferation and apoptotic markers was assessed by qPCR. Cell proliferation and soluble and insoluble collagen were determined by ELISA and LC-MS/MS, respectively. TG1 and TG2 were both expressed in neonatal rat cardiomyocytes and fibroblasts before transfection. Other TGs were not detected before and after transfection. TG2 was predominantly expressed and more effectively silenced than TG1. Knocking down TG1 or TG2 significantly modified profibrotic markers mRNA expression in fibroblasts, decreasing connective tissue growth factor (CTGF) and increasing transforming growth factor-β1 compared to the negative siRNA control. Reduced expression of collagen 3A1 was found upon TG1 knockdown, while TG2 knockdown raised α-smooth muscle actin expression. TG2 knockdown further increased fibroblast proliferation and the expression of proliferation marker cyclin D1. Lower insoluble collagen content and collagen cross-linking were evidenced upon silencing TG1 or TG2. Transcript levels of collagen 1A1, fibronectin 1, matrix metalloproteinase-2, cyclin E2, and BCL-2-associated X protein/B-cell lymphoma 2 ratio were strongly correlated with TG1 mRNA expression, whereas TG2 expression correlated strongly with CTGF mRNA abundance. These findings support a functional and signalling role for TG1 and TG2 from fibroblasts in regulating key processes underlying myocardial ECM homeostasis and dysregulation, suggesting that these isoforms could be potential and promising targets for the development of cardiac fibrosis therapies.
... TGase2, a member of the transglutaminase family, has emerged as a potential therapeutic target in several diseases including celiac disease, neurodegenerative disorders, cancer, and diabetes-related complications. 18,29,30 Our results showed that vascular dysfunction was suppressed in the retina of diabetic Tgm2 −/− mice compared to diabetic C57BL/6 mice. In contrast, neuronal abnormalities, including upregulation of GFAP and Iba-1 expression and downregulation of GLAST expression, were not affected by disruption of the TGase2 gene in the retina of diabetic Tgm2 −/− mice but were inhibited by Trolox. ...
Diabetic retinopathy (DR) is caused by retinal vascular dysfunction and neurodegeneration. Intraocular delivery of C‐peptide has been shown to be beneficial against hyperglycemia‐induced microvascular leakage in the retina of diabetes; however, the effect of C‐peptide on diabetes‐induced retinal neurodegeneration remains unknown. Moreover, extraocular C‐peptide replacement therapy against DR to avoid various adverse effects caused by intravitreal injections has not been studied. Here, we demonstrate that systemic C‐peptide supplementation using osmotic pumps or biopolymer‐conjugated C‐peptide hydrogels ameliorates neurodegeneration by inhibiting vascular endothelial growth factor‐induced pathological events, but not hyperglycemia‐induced vascular endothelial growth factor expression, in the retinas of diabetic mice. C‐peptide inhibited hyperglycemia‐induced activation of macroglial and microglial cells, downregulation of glutamate aspartate transporter 1 expression, neuronal apoptosis, and histopathological changes by a mechanism involving reactive oxygen species generation in the retinas of diabetic mice, but transglutaminase 2, which is involved in retinal vascular leakage, is not associated with these pathological events. Overall, our findings suggest that systemic C‐peptide supplementation alleviates hyperglycemia‐induced retinal neurodegeneration by inhibiting a pathological mechanism, involving reactive oxygen species, but not transglutaminase 2, in diabetes.
... This dramatic shift in interactors is most likely related to TG2 pleiotropic functions in and outside the cell [7]. Driven by the cellular state at hand, TG2 localization and conformation changes, related to its catalytically active (open) or inactive (closed) state, lead to different binding partners and/or substrates [7,41]. Of special interest are the identified TG2 binding partners unique to APP23 mice and well-known players in Aβ pathophysiology and neurodegeneration such as the glutamate receptor in the extracellular space or cell membrane compartment [42], and 14-3-3 protein and alpha-B-crystallin in the cell-matrix compartment [29,43,44]. ...
Amyloid-beta (Aβ) deposition in the brain is closely linked with the development of Alzheimer’s disease (AD). Unfortunately, therapies specifically targeting Aβ deposition have failed to reach their primary clinical endpoints, emphasizing the need to broaden the search strategy for alternative targets/mechanisms. Transglutaminase-2 (TG2) catalyzes post-translational modifications, is present in AD lesions and interacts with AD-associated proteins. However, an unbiased overview of TG2 interactors is lacking in both control and AD brain. Here we aimed to identify these interactors using a crossbreed of the AD-mimicking APP23 mouse model with wild type and TG2 knock-out (TG2−/−) mice. We found that absence of TG2 had no (statistically) significant effect on Aβ pathology, soluble brain levels of Aβ1–40 and Aβ1–42, and mRNA levels of TG family members compared to APP23 mice at 18 months of age. Quantitative proteomics and network analysis revealed a large cluster of TG2 interactors involved in synaptic transmission/assembly and cell adhesion in the APP23 brain typical of AD. Comparative proteomics of wild type and TG2−/− brains revealed a TG2-linked pathological proteome consistent with alterations in both pathways. Our data show that TG2 deletion leads to considerable network alterations consistent with a TG2 role in (dys)regulation of synaptic transmission and cell adhesion in APP23 brains.
... TGM2 (transglutaminase 2) is a multifunctional cross-linking enzyme [37] that is involved in many biological processes in the human body [38,39], including the complex process of wound healing [39][40][41][42]. TGM2 causes tissue's resistance to proteolytic degradation and enhances its' mechanical strength [43]. ...
Platelet concentrate products are increasingly used in many medical disciplines due to their regenerative properties. As they contain a variety of chemokines, cytokines, and growth factors, they are used to support the healing of chronic or complicated wounds. To date, underlying cellular mechanisms have been insufficiently investigated. Therefore, we analyzed the influence of Platelet-Released Growth Factors (PRGF) on human dermal fibroblasts. Whole transcriptome sequencing and gene ontology (GO) enrichment analysis of PRGF-treated fibroblasts revealed an induction of several genes involved in the formation of the extracellular matrix (ECM). Real-time PCR analyses of PRGF-treated fibroblasts and skin explants confirmed the induction of ECM-related genes, in particular transforming growth factor beta-induced protein (TGFBI), fibronectin 1 (FN1), matrix metalloproteinase-9 (MMP-9), transglutaminase 2 (TGM2), fermitin family member 1 (FERMT1), collagen type I alpha 1 (COL1A1), a disintegrin and metalloproteinase 19 (ADAM19), serpin family E member 1 (SERPINE1) and lysyl oxidase-like 3 (LOXL3). The induction of these genes was time-dependent and in part influenced by the epidermal growth factor receptor (EGFR). Moreover, PRGF induced migration and proliferation of the fibroblasts. Taken together, the observed effects of PRGF on human fibroblasts may contribute to the underlying mechanisms that support the beneficial wound-healing effects of thrombocyte concentrate products.
... Transglutaminase 2 (TGM2) is a family member of the transglutaminase (TGM) enzymes, which contain 8 kinds of discrepant enzyme subtypes designated as blood coagulation factor XIII and TGM1-7 [10]. TGM2, also known as tissue transglutaminase, is constitutively expressed in various organ-specific cells such as smooth muscle cells and fibroblasts [11]. ...
Background:
Propofol is a known intravenous hypnotic drug used for induction and maintenance of sedation and general anesthesia. Emerging studies also reveal a neuroprotective effect of propofol in diverse diseases of neuronal injuries via modulating microglia activation. In this study, we aimed to uncover the downstream targets of propofol in this process.
Methods:
RNA sequencing analysis to identify genes implicated in the propofol-mediated neuroprotective effect. Quantitative real-time PCR, enzyme-linked immunosorbent assay, and Western blotting analysis were performed to analyze inflammatory gene expression, cytokine levels, and TGM2. BV2 cells and primary microglia were used for functional verification and mechanism studies.
Results:
The multifunctional enzyme transglutaminase 2 (TGM2) was identified as a putative functional mediator of propofol. TGM2 was significantly upregulated in lipopolysaccharide- (LPS-) primed BV2 cells. Genetic silencing of TGM2 abolished LPS-induced microglial activation. Notably, gain-of-function experiments showed that the proinflammatory effects of TGM2 were dependent on its GTP binding activity instead of transamidase activity. Then, TGM2 was revealed to activate the NF-κB signaling pathway to facilitate microglial activation. Propofol can inhibit TGM2 expression and NF-κB signaling in BV2 cells and primary microglia. Ectopic expression of TGM2 or constitutively active IKKβ (CA-IKKβ) can compromise propofol-induced anti-inflammatory effects.
Conclusions:
Our findings suggest that TGM2-mediated activation of NF-κB signaling is an important mechanism in the propofol-induced neuroprotective effect that prevents microglial activation.
... Interestingly, TN-X expression is significantly downregulated during tumor progression in most cancers, and a high TNXB expression correlates with a good survival prognosis [44]. Likewise, a downregulation of TGM2 was found in aggressive tumors and metastasis, while overexpression of TGM2 led to reduction in tumor incidence and progression [45]. Thus, an upregulation of TNXB and TGM2 in RE VFF goes in line with the benign nature of RE pathology, despite yearlong exposure to cigarette smoke and excessive voice abuse [46]. ...
The voice disorder Reinke’s edema (RE) is a smoking- and voice-abuse associated benign lesion of the vocal folds, defined by an edema of the Reinke’s space, accompanied by pathological microvasculature changes and immune cell infiltration. Vocal fold fibroblasts (VFF) are the main cell type of the lamina propria and play a key role in the disease progression. Current therapy is restricted to symptomatic treatment. Hence, there is an urgent need for a better understanding of the molecular causes of the disease. In the present study, we investigated differential expression profiles of RE and control VFF by means of RNA sequencing. In addition, fast gene set enrichment analysis (FGSEA) was performed in order to obtain involved biological processes, mRNA and protein levels of targets of interest were further evaluated. We identified 74 differentially regulated genes in total, 19 of which were upregulated and 55 downregulated. Differential expression analysis and FGSEA revealed upregulated genes and pathways involved in extracellular matrix (ECM) remodeling, inflammation and fibrosis. Downregulated genes and pathways were involved in ECM degradation, cell cycle control and proliferation. The current study addressed for the first time a direct comparison of VFF from RE to control and evaluated immediate functional consequences.
... Despite the variety of activities undertaken by TG2, the biological role of these interactions has not yet been completely clarified [1]. TG2 is abundantly expressed in endothelial cells, macrophages and smooth muscle cells, and is known to be involved in several physiological activities, including immune processes, apoptosis, angiogenesis, wound healing, cellular differentiation, neuronal regeneration, bone development [2], and in several inflammatory, autoimmune, and neoplastic diseases [3]. TG2 is in a closed conformation in normal conditions, maintained by guanosine-5'-triphosphate and integrin bindings. ...
Since tissue transglutaminase-2 (TG2) can represent a marker of inflammation for some gastrointestinal (GI) diseases, we aimed to evaluate TG2 and inflammatory markers? mucosal content in gastric antrum biopsies to shed light on the histological and biochemical background of chronic gastritis inflammation. Fifty-one of 78 patients who underwent upper GI endoscopy (UGIE) for dyspeptic symptoms, had a gastric biopsy. The symptom profile was assessed by a GI symptom rating scale (GSRS) score. Thirtyfive patients (69%) showed chronic gastritis. TG2, interleukin-6 (IL)-6, IL-8, IL-10, tumor necrosis factor (TNF)-?, lipopolysaccharides (LPS) and toll-like receptor (TLR)-4 were evaluated in serum and the culture medium of gastric biopsies. TG2, IL-8, IL-10, TLR-4 and TNF-? were significantly higher in active chronic gastritis than in the inactive one and were linked to macrophage concentration. IL-6 was significantly lower in the active form of chronic gastritis than in the inactive one and negatively correlated with TG2. Lastly, IL- 10 significantly correlated with the macrophage score. TG2 can exert an active role in chronic gastritis pathogenesis by cooperating with different markers of inflammation. It seems that TG2 can represent a possible therapeutic target for modulating inflammation and disease progression.
... Transglutaminase-2 (TGM2 or TG2, also named tissue glutaminase) is a multifunctional protein [50] that has cross-linking and hydrolysis activity, is enrolled in many biological processes in the human body [51,52] and is implicated in the complex wound healing process [52][53][54][55]. TGM2 enhanced the proteolytic resistance and strength of the collagen matrix [56] and promotes angiogenesis and wound healing [51,57]. ...
Platelet-released growth factor (PRGF) is a thrombocyte concentrate lysate which, like its clinically equivalent variations (e.g., Vivostat PRF® (platelet-rich fibrin)), is known to support the healing of chronic and hard-to-heal wounds. However, studies on the effect of PRGF on keratinocytes remain scarce. This study aims to identify genes in keratinocytes that are significantly influenced by PRGF. Therefore, we performed a whole transcriptome and gene ontology (GO) enrichment analysis of PRGF-stimulated human primary keratinocytes. This revealed an increased expression of genes involved in extracellular matrix (ECM) organization. Real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) analysis confirmed the PRGF-mediated induction of selected ECM-related factors such as transforming growth factor beta-induced protein, fibronectin 1, matrix metalloproteinase-9, transglutaminase 2, fermitin family member 1, collagen type I alpha 1 and collagen type XXII alpha 1. PRGF-induced expression of the above factors was influenced by blockade of the epidermal growth factor receptor (EGFR), a receptor playing a crucial role in wound healing. A differential induction of the investigated factors was also detected in skin explants exposed to PRGF and in experimentally generated in vivo wounds treated with Vivostat PRF®. Together, our study indicates that the induction of ECM-related factors may contribute to the beneficial wound-healing effects of PRGF-based formulations.
... Human TGase2 comprises 687 amino acids (~70 kDa) and has a four-domain organization. It contains the N-terminal β-sandwich domain, the catalytic core domain containing the catalytic triad, and two β-barrel domains (β-barrel1 and β-barrel2) [16]. Using this domain organization, TGase2 performs multiple functions; it acts as a GTPase [17][18][19], kinase [20,21], protein disulfide isomerase [22], and scaffolding factor [23], and performs the traditional activity of cross-linking by transamidation. ...
... Cross-linking, deamination, and amine incorporation activities are the main functions of TGase2, GTPase, disulfide isomerase, and kinase. Scaffolding activities are also reported as minor functions of TGase2 [16,57]. The principal transamidation activity is performed by the catalytic triad, composed of C277, H335, and D358, on the active site of TGase2. ...
Human transglutaminase 2 (TGase2) has various functions, including roles in various cellular processes such as apoptosis, development, differentiation, wound healing, and angiogenesis, and is linked to many diseases such as cancer. Although TGase2 has been considered an optimized drug target for the treatment of cancer, fibrosis, and neurodegenerative disorders, it has been difficult to generate TGase2-targeted drugs for clinical use because of the relatively flat and broad active site on TGase2. To design more specific and powerful inhibitors, detailed structural information about TGase2 complexed with various effector and inhibitor molecules is required. In this review, we summarized the current structural studies on TGase2, which will aid in designing drugs that can overcome the aforementioned limitations.
