T-cell Death-associated Gene 51 Expression Research Articles

TDAG51 Attenuates Impaired Lipid Metabolism and Insulin Resistance in Gestational Diabetes Mellitus Through SREBP-1/ANGPTL8 Pathway.

T-cell death-associated gene 51 (TDAG51) belongs to the transcription factor family and is involved in the energy homeostasis of the liver through the regulation of lipogenesis. To evaluate the role of T-cell death-associated gene 51 in gestational diabetes mellitus. Experimental study. A total of 30 patients with GDM were enrolled in the study. TDAG51 expression in patients with gestational diabetes mellitus was assessed by Western blotting and quantitative reverse-transcription polymerase chain reaction. A high-fat and high-sugar diet was used to establish a Gestational diabetes mellitus model. gestational diabetes mellitus mice were injected with lentivirus-mediated overexpression of TDAG51. Blood glucose was measured using a glucometer, and glucose and insulin tolerance tests were performed to detect insulin resistance. Liver and adipose tissues were subjected to hematoxylineosin staining. Cell apoptosis was detected by TUNEL staining. Human villous trophoblast cells (HTR-8/SVneo) were treated with a high-glucose medium to induce gestational diabetes mellitus. TDAG51 was downregulated in gestational diabetes mellitus and high glucose-induced HTR-8/SVneo. TDAG51 overexpression reduced the level of blood glucose, enhanced serum insulin, and attenuated glucose and insulin tolerance in gestational diabetes mellitus mice. TDAG51 overexpression also ameliorated impaired lipid metabolism and alleviated adipocyte hypertrophy and hepatic lipid droplets in gestational diabetes mellitus mice. The expressions of SREBP-1 and ANGPTL8 were upregulated in gestational diabetes mellitus and showed a negative correlation with TDAG51 in patients with gestational diabetes mellitus. TDAG51 increased the expressions of SREBP-1 and ANGPTL8 in gestational diabetes mellitus mice. TDAG51 overexpression reduced cell apoptosis and enhanced cell viability of high glucose-induced HTR-8/SVneo. Ectopic expression of ANGPTL8 attenuated the TDAG51-induced increase in cell viability and decrease in apoptosis in high glucose-induced HTR-8/SVneo. TDAG51 alleviated impaired lipid metabolism and insulin resistance in gestational diabetes mellitus via downregulation of SREBP 1/ANGPTL8 pathway.

T-Cell Death Associated Gene 51 Is a Novel Negative Regulator of PPARγ That Inhibits PPARγ-RXRα Heterodimer Formation in Adipogenesis

The nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) is the master transcriptional regulator in adipogenesis. PPARγ forms a heterodimer with another nuclear receptor, retinoid X receptor (RXR), to form an active transcriptional complex, and their transcriptional activity is tightly regulated by the association with either coactivators or corepressors. In this study, we identified T-cell death-associated gene 51 (TDAG51) as a novel corepressor of PPARγ-mediated transcriptional regulation. We showed that TDAG51 expression is abundantly maintained in the early stage of adipogenic differentiation. Forced expression of TDAG51 inhibited adipocyte differentiation in 3T3-L1 cells. We found that TDAG51 physically interacts with PPARγ in a ligand-independent manner. In deletion mutant analyses, large portions of the TDAG51 domains, including the pleckstrin homology-like, glutamine repeat and proline-glutamine repeat domains but not the proline-histidine repeat domain, are involved in the interaction with the region between residues 140 and 506, including the DNA binding domain, hinge, ligand binding domain and activation function-2 domain, in PPARγ. The heterodimer formation of PPARγ-RXRα was competitively inhibited in a ligand-independent manner by TDAG51 binding to PPARγ. Thus, our data suggest that TDAG51, which could determine adipogenic cell fate, acts as a novel negative regulator of PPARγ by blocking RXRα recruitment to the PPARγ-RXRα heterodimer complex in adipogenesis.

CD10, TDAG51, CK20, AR, INSM1, and Nestin Expression in the Differential Diagnosis of Trichoblastoma and Basal Cell Carcinoma.

Trichoblastoma (TB) and basal cell carcinoma (BCC) are 2 different neoplasms composed of basaloid cells and have overlapping histopathological features. We compared the immunoexpression of CD10, T-cell death-associated gene 51 (TDAG51), cytokeratin 20 (CK20), androgen receptor (AR), insulinoma-associated protein 1 (INSM1), and nestin for the differential diagnosis of these tumors. We assessed a total of 27 BCC and 27 TB cases, including 4 TB lesions in nevus sebaceous and 3 malignant TB lesions for CD10, TDAG51, CK20, AR, INSM1, and nestin expression. Staining for CK20, TDAG51, INSM1, and stromal CD10 was significantly more common in TB cases than in BCC cases ( P < .001). Epithelial CD10 and AR staining was significantly more common in BCC cases than in TB cases ( P < .001). The difference between the groups for nestin staining was not significant ( P > .05). Stromal CD10 staining was the most sensitive marker (96.3%) and INSM1 the least sensitive (55.6%) marker for TB. TDAG51 showed 100% specificity for TB. A larger number of CK20 positive cells was found in the cases associated with nevus sebaceous than in the other TBs. All the selected markers except nestin were useful for the differential diagnosis between TB and BCC. CD10 and TDAG51 were more useful than the other markers. The use of CK20 could be preferred in nevus sebaceous lesions. INSM1 was less effective in highlighting Merkel cells within the lesion than CK20.

Restoration of hepatic TDAG51 expression improves insulin signaling and reduces weight gain in mouse models of non‐alcoholic fatty liver disease

The absence of T‐cell death‐associated gene 51 (TDAG51) in mice results in late‐onset insulin resistance (IR), obesity and hepatic steatosis. In support of these findings, mice fed a high fat diet, which leads to IR and obesity, as well as the leptin‐deficient mouse model, a well‐established genetic model of type 2 diabetes and obesity, show significantly diminished hepatic TDAG51 protein levels. Here we report that hepatic TDAG51 protein levels are reduced in multiple mouse models of liver injury and in liver biopsies from patients with non‐alcoholic steatohepatitis. Given that hepatic TDAG51 protein levels decrease under conditions of fatty liver and correlate with IR, we investigated whether restoring hepatic TDAG51 protein levels would reverse hepatic IR. Hepatic expression of a TDAG51‐GFP fusion protein was increased via a liver‐specific adeno‐associated virus (AAV) in both TDAG51 knockout and leptin‐deficient mice. Restoration of hepatic TDAG51 protein increased insulin sensitivity and reduced weight gain compared to mice injected with a control AAV vector encoding only GFP. Specifically, TDAG51 knockout mice expressing ectopic TDAG51 demonstrated: 1) improved Akt473 phosphorylation, 2) reduced expression of diacylglycerol O‐acyltransferase, which catalyzes the final step in triglyceride biosynthesis, and 3) reduced expression of the SREBP‐1c target genes, fatty acid synthase and stearoyl‐CoA desaturase‐1. These findings demonstrate that restoring hepatic TDAG51 in mouse models of metabolic disease and fatty liver improves hepatic insulin signaling and reduces weight gain. However, this protective effect is lost over time, correlates with fatty liver progression and is accompanied by diminished hepatic TDAG51 protein stability. Taken together, these studies suggest that hepatic TDAG51 is an important factor that mediates insulin signaling and weight gain. Future studies aimed at increasing hepatic TDAG51 protein levels and/or stability may represent a new therapeutic opportunity for the amelioration of obesity and augmentation of insulin sensitivity in non‐alcoholic fatty liver disease.Support or Funding InformationR.C.A is supported by grants from the Heart and Stroke Foundation of Ontario and the Canadian Institutes of Health Research. Financial support from St. Joseph's Healthcare Hamilton is also acknowledged. R.C.A. is a Career Investigator of the Heart and Stroke Foundation of Ontario and holds the Amgen Canada Research Chair in Nephrology. K.N.M acknowledges financial support from the William R. Hummel Homocystinuria Research Fund and holds the Ehst‐Hummel‐Kaufmann Family Endowed Chair in Inherited Metabolic Disease. G.R.S is supported by a Canada Research Chair in Metabolism and Obesity, the J. Bruce Duncan Endowed Chair in Metabolic Diseases and grants from the Canadian Institutes of Health Research and Diabetes Canada.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Pleckstrin homology like domain family member, TDAG51, is temporally regulated during skeletal muscle regeneration

The capacity for skeletal muscle to repair from daily insults as well as larger injuries is a vital component to maintaining muscle health over our lifetime. Given the importance of skeletal muscle for our physical and metabolic well-being, identifying novel factors mediating the growth and repair of skeletal muscle will thus build our foundational knowledge and help lead to potential therapeutic avenues for muscle wasting disorders. To that end, we investigated the expression of T-cell death associated gene 51 (TDAG51) during skeletal muscle repair and studied the response of TDAG51 deficient (TDAG51-/-) mice to chemically-induced muscle damage.TDAG51 mRNA and protein expression within uninjured skeletal muscle is almost undetectable but, in response to chemically-induced muscle damage, protein levels increase by 5 days post-injury and remain elevated for up to 10 days of regeneration. To determine the impact of TDAG51 deletion on skeletal muscle form and function, we compared adult male TDAG51-/- mice with age-matched wild-type (WT) mice. Body and muscle mass were not different between the two groups, however, in situ muscle testing demonstrated a significant reduction in force production both before and after fatiguing contractions in TDAG51-/- mice.During the early phases of the regenerative process (5 days post-injury), TDAG51-/- muscles display a significantly larger area of degenerating muscle tissue concomitant with significantly less regenerating area compared to WT (as demonstrated by embryonic myosin heavy chain expression). Despite these early deficits in regeneration, TDAG51-/- muscles displayed no morphological deficits by 10 days post injury compared to WT mice.Taken together, the data presented herein demonstrate TDAG51 expression to be upregulated in damaged skeletal muscle and its absence attenuates the early phases of muscle regeneration.

Up-regulation of TDAG51 is a dependent factor of LPS-induced RAW264.7 macrophages proliferation and cell cycle progression

Context: As a component of the outer membrane in Gram-negative bacteria, lipopolysaccharide (LPS)-induced proliferation and cell cycle progression of monocytes/macrophages. It has been suggested that the proapoptotic T-cell death-associated gene 51 (TDAG51) might be associated with cell proliferation and cell cycle progression; however, its role in the interaction between LPS and macrophages remains unclear.Objective: We attempted to elucidate the role(s) of TDAG51 played in the interaction between LPS and macrophages.Materials and methods: We investigated TDAG51 expression in RAW264.7 cells stimulated with LPS and examined the effects of RNA interference-mediated TDAG51 down-regulation. We used CCK-8 assay and flow cytometry analysis to evaluate the interaction between TDAG51 and LPS-induced proliferation and cell cycle progression in RAW264.7 cells.Results: Our findings indicate that TDAG51 is up-regulated in LPS-stimulated RAW264.7 cells, the TDAG51 siRNA effectively reduced TDAG51 protein up-regulation following LPS stimulation in RAW264.7 cells, the significant changes of the proliferation and cell cycle progression of RAW264.7 cells in TDAG51 Knockdown RAW264.7 cells treated with LPS were observed.Conclusion: These findings suggested that TDAG51 up-regulation is a dependent event during LPS-mediated proliferation and cell cycle progression, and which increase our understanding of the interaction mechanism between LPS and macrophages.

TDAG51 deficiency promotes oxidative stress-induced apoptosis through the generation of reactive oxygen species in mouse embryonic fibroblasts

Apoptosis has an important role in maintaining tissue homeostasis in cellular stress responses such as inflammation, endoplasmic reticulum stress, and oxidative stress. T-cell death-associated gene 51 (TDAG51) is a member of the pleckstrin homology-like domain family and was first identified as a pro-apoptotic gene in T-cell receptor-mediated cell death. However, its pro-apoptotic function remains controversial. In this study, we investigated the role of TDAG51 in oxidative stress-induced apoptotic cell death in mouse embryonic fibroblasts (MEFs). TDAG51 expression was highly increased by oxidative stress responses. In response to oxidative stress, the production of intracellular reactive oxygen species was significantly enhanced in TDAG51-deficient MEFs, resulting in the activation of caspase-3. Thus, TDAG51 deficiency promotes apoptotic cell death in MEFs, and these results indicate that TDAG51 has a protective role in oxidative stress-induced cell death in MEFs.

Loss of TDAG51 Results in Mature-Onset Obesity, Hepatic Steatosis, and Insulin Resistance by Regulating Lipogenesis

Regulation of energy metabolism is critical for the prevention of obesity, diabetes, and hepatic steatosis. Here, we report an important role for the pleckstrin homology–related domain family member, T-cell death–associated gene 51 (TDAG51), in the regulation of energy metabolism. TDAG51 expression was examined during adipocyte differentiation. Adipogenic potential of preadipocytes with knockdown or absence of TDAG51 was assessed. Weight gain, insulin sensitivity, metabolic rate, and liver lipid content were also compared between TDAG51-deficient (TDAG51−/−) and wild-type mice. In addition to its relatively high expression in liver, TDAG51 was also present in white adipose tissue (WAT). TDAG51 was downregulated during adipogenesis, and TDAG51−/− preadipocytes exhibited greater lipogenic potential. TDAG51−/− mice fed a chow diet exhibited greater body and WAT mass, had reduced energy expenditure, displayed mature-onset insulin resistance (IR), and were predisposed to hepatic steatosis. TDAG51−/− mice had increased hepatic triglycerides and SREBP-1 target gene expression. Furthermore, TDAG51 expression was inversely correlated with fatty liver in multiple mouse models of hepatic steatosis. Taken together, our findings suggest that TDAG51 is involved in energy homeostasis at least in part by regulating lipogenesis in liver and WAT, and hence, may constitute a novel therapeutic target for the treatment of obesity and IR.

Expression of heat shock transcription factor 1 and its downstream target protein T-cell death associated gene 51 in the spinal cord of a mouse model of amyotrophic lateral sclerosis

Heat shock transcription factor 1 (HSF1) modulates the expression of the cell survival heat shock protein 70 (HSP70) and the cell death T-cell death associated gene 51 (TDAG51) in response to heat shock and various other cell stressors. We previously reported an increase in HSP70 in glial cells of the spinal anterior horn. Here we examined the temporal and spatial changes of HSF1 and TDAG51 expression over the course of motor neuron degeneration in the spinal cord of a mouse model of ALS (G93A-SOD1 Tg mice). The number of glial-like cells expressing HSF1 increased in G93A-SOD1 Tg mice at both early symptomatic (14 weeks) and end stages of disease (18 weeks), while the number of spinal neurons expressing HSF1 decreased. The total level of HSF1 in the anterior lumbar spinal cord was significantly decreased in G93A-SOD1 Tg mice at the end stage of disease. In contrast to HSF1, the level of TDAG51 in the anterior lumbar spinal cord was significantly increased in G93A-SOD1 Tg mice at the end stage of disease. Moreover, TDAG51 progressively increased in glial-like cells in the anterior lumbar spinal cord of G93A-SOD1 Tg mice from the early symptomatic stage, while decreasing in spinal neurons. Taken together, our results suggest that the balance between the cell survival and death signals mediated by HSP70 and TDAG51, respectively, may be disturbed by the altered expression of HSF1 during the progression of disease in this ALS model.

TDAG51 in the anterior temporal neocortex of patients with intractable epilepsy

TDAG51 (T cell death-associated gene 51) is an apoptosis-associated protein. Our aim was to investigate TDAG51 expression in the anterior temporal neocortex of patients with intractable epilepsy (IE), and then to discuss the possible role of TDAG51 in IE. Tissue samples from the anterior temporal neocortex of 33 patients who had surgery for IE were used to detect TDAG51 expression by immunohistochemistry, immunofluorescence, and Western blotting. We compared these tissues with nine histologically normal anterior temporal lobes from intracranial hypertension patients who had decompression procedures. TDAG51 was mainly expressed in the cytoplasm of neurons and glial cells. TDAG51 in IE was significantly higher than that in the controls. These findings were consistently observed using Western blotting, immunofluorescence, and immunohistochemistry techniques. TDAG51 in patients with IE was significantly higher when compared with levels in the controls. This finding suggests TDAG51 is consistent with a possible role of this gene in the evolution of the pathology in IE.

Deficiency in TDAG51 Decreases Atherosclerotic Lesion Development in ApoE-Deficient Mice.

T-cell death associated gene 51 (TDAG51) is a pro-apoptotic gene that can be induced by endoplasmic reticulum (ER) stress agents, including homocysteine, tunicamycin, thapsigargin or dithiothreitol. Our previous studies have demonstrated that transient overexpression of TDAG51 elicited significant changes in cell morphology, decreased cell adhesion and promoted detachment-induced programmed cell death (PCD). In support of these in vitro findings, we have further shown that TDAG51 expression was increased and correlated with PCD in the atherosclerotic lesions from apolipoprotein E (apoE)-deficient mice fed hyperhomocysteinemic diets, compared to mice fed control diet. We designed the current study to investigate the effect of TDAG51 deficiency in the development and progression of atherosclerosis. To assess in vivo significance of TDAG51 on atherosclerosis, we have crossed TDAG51-deficient mice with apoE-deficient mice to obtain double knockout mice. Our findings have demonstrated that TDAG51/apoE-deficient mice have a significant decrease in atherosclerotic lesion area, compared to age- and sex-matched apoE-deficient mice. Total plasma cholesterol and triglycerides as well as lipoprotein profiles were similar in both groups. However, TDAG51/apoE-deficient mice presented with increased hepatic steatosis. Further, a significant upregulation of peroxisome proliferator-activated receptor γ (PPAR-γ), a transcription factor required for adipose tissue formation, was demonstrated in TDAG51-deficient mouse embryonic fibroblasts (MEFs), compared to control wildtype MEFs. Interestingly, earlier studies in mice have reported that overexpression of PPAR-γ decreases atherosclerotic lesion development and increases hepatic steatosis - a phenotype similar to that observed in the mouse deficient in both apoE and TDAG51. Collectively, these findings provide evidence that TDAG51 mediates atherosclerotic lesion development and hepatic steatosis through a mechanism involving PPAR-γ.

TDAG51 Mediates the Effects of Insulin-like Growth Factor I (IGF-I) on Cell Survival

Insulin-like growth factor-I (IGF-I) receptors and insulin receptors belong to the same subfamily of receptor tyrosine kinases and share a similar set of intracellular signaling pathways, despite their distinct biological actions. In the present study, we evaluated T cell death-associated gene 51 (TDAG51), which we previously identified by cDNA microarray analysis as a gene specifically induced by IGF-I. We characterized the signaling pathways by which IGF-I induces TDAG51 gene expression and the functional role of TDAG51 in IGF-I signaling in NIH-3T3 (NWTb3) cells, which overexpress the human IGF-I receptor. Treatment with IGF-I increased TDAG51 mRNA and protein levels in NWTb3 cells. This effect of IGF-I was specifically mediated by the IGF-IR, because IGF-I did not induce TDAG51 expression in NIH-3T3 cells overexpressing a dominant-negative IGF-I receptor. Through the use of specific inhibitors of various protein kinases, we found that IGF-I induced TDAG51 expression via the p38 MAPK pathway. The ERK, JNK, and phosphatidylinositol 3-kinase pathways were not involved in IGF-I-induced regulation of TDAG51. To assess the role of TDAG51 in IGF-I signaling, we used small interfering RNA (siRNA) expression vectors directed at two different target sites to reduce the level of TDAG51 protein. In cells expressing these siRNA vectors, TDAG51 protein levels were decreased by 75-80%. Furthermore, TDAG51 siRNA expression abolished the ability of IGF-I to rescue cells from serum starvation-induced apoptosis. These findings suggest that TDAG51 plays an important role in the anti-apoptotic effects of IGF-I.

Regulation of T-cell death-associated gene 51 (TDAG51) expression in human T-cells.

T-cell death-associated gene 51 (TDAG51) has been described to regulate T-cell receptor/CD3-dependent induction of CD95/Fas and subsequent activation-induced cell death (AICD) in a murine T-cell hybridoma. Using well-defined pharmacological inhibitors, we investigated the regulation of TDAG51 expression in human T-cells and the correlation with cell death. TDAG51 was induced in resting T-cells, lymphoid cell lines and AICD-susceptible as well as AICD-resistant T-cell clones, and induction was inhibited by MAP-kinase inhibitors and PKC inhibitor Gö6983. No correlation between the effects of inhibitors on TDAG51 expression and cell death was observed. The constitutive TDAG51 expression in five pancreatic carcinoma cell lines was reduced by MAP-kinase inhibitors but not by Gö6983. Furthermore, the inducible overexpression of TDAG51 in TetOn Jurkat cells did not modulate cellular proliferation, phorbolester/ionomycin-induced growth arrest, or the expression of various cell surface molecules. Our results indicate that the expression of TDAG51 in human T-cells does not correlate with AICD.

TDAG51 Is Induced by Homocysteine, Promotes Detachment-mediated Programmed Cell Death, and Contributes to the Development of Atherosclerosis in Hyperhomocysteinemia

Hyperhomocysteinemia is an independent risk factor for cardiovascular disease and accelerates atherosclerosis in apoE-/- mice. Despite the observations that homocysteine causes endoplasmic reticulum (ER) stress and programmed cell death (PCD) in cultured human vascular endothelial cells, the cellular factors responsible for this effect and their relevance to atherogenesis have not been completely elucidated. We report here that homocysteine induces the expression of T-cell death-associated gene 51 (TDAG51), a member of the pleckstrin homology-related domain family, in cultured human vascular endothelial cells. This effect was observed for other ER stress-inducing agents, including dithiothreitol and tunicamycin. TDAG51 expression was attenuated in homozygous A/A mutant eukaryotic translation initiation factor 2 alpha mouse embryonic fibroblasts treated with homocysteine or tunicamycin, suggesting that ER stress-induced phosphorylation of eukaryotic translation initiation factor 2 alpha is required for TDAG51 transcriptional activation. Transient overexpression of TDAG51 elicited significant changes in cell morphology, decreased cell adhesion, and promoted detachment-mediated PCD. In support of these in vitro findings, TDAG51 expression was increased and correlated with PCD in the atherosclerotic lesions from apoE-/- mice fed hyperhomocysteinemic diets, compared with mice fed a control diet. Collectively, these findings provide evidence that TDAG51 is induced by homocysteine, promotes detachment-mediated PCD, and contributes to the development of atherosclerosis observed in hyperhomocysteinemia.