Glucose-stimulated Expression of Txnip Is Mediated by Carbohydrate Response Element-binding Protein, p300, and Histone H4 Acetylation in Pancreatic Beta Cells

Abstract

Recently, we identified Txnip (thioredoxin-interacting protein) as a mediator of glucotoxic beta cell death and discovered that lack of Txnip protects against streptozotocin-and obesityinduced diabetes by preventing beta cell apoptosis and preserving endogenous beta cell mass. Txnip has therefore become an attractive target for diabetes therapy, but although we have found that txnip transcription is highly induced by glucose through a unique carbohydrate response element, the factors controlling this effect have remained unknown. Using transient transfection experiments, we now show that overexpression of the carbohydrate response element-binding protein (ChREBP) transactivates the txnip promoter, whereas ChREBP knockdown by small interfering RNA completely blunts glucose-induced txnip transcription. Moreover, chromatin immunoprecipitation demonstrated that glucose leads to a dose-and time-dependent recruitment of ChREBP to the txnip promoter in vivo in INS-1 beta cells as well as human islets. Furthermore, we found that the co-activator and histone acetyltransferase p300 co-immunoprecipitates with ChREBP and also binds to the txnip promoter in response to glucose. Interestingly, this is associated with specific acetylation of histone H4 and recruitment of RNA polymerase II as measured by chromatin immunoprecipitation. Thus, with this study we have identified ChREBP as the transcription factor that mediates glucose-induced txnip expression in human islets and INS-1 beta cells and have characterized the chromatin modification associated with glucose-induced txnip transcription. In addition, the results reveal for the first time that ChREBP interacts with p300. This may explain how ChREBP induces H4 acetylation and sheds new light on glucose-mediated regulation of chromatin structure and transcription.

Role of glucose-6-phosphate and xylulose-5-phosphate in the regulation of glucose-stimulated gene expression in the pancreatic β cell line, INS-1E

“…PKLR is a rate-limiting enzyme in the glycolytic pathway and plays an important role in the regulation of glycolysis and lipogenesis [6,7]. TXNIP has an important role in glucose toxicity in pancreatic β cells [26]. In our study, 2DG and Glc increased the intracellular 2DG6P and G6P contents in INS-1E cells (Fig.…”

“…Pklr and Txnip are well known ChREBP target genes [26,27]. PKLR is a rate-limiting enzyme in the glycolytic pathway and plays an important role in the regulation of glycolysis and lipogenesis [6,7].…”

“…In brief, cells were cultured in 15-cm dishes for 2 d and preincubated in RPMI-1640 media containing 2.5 mM glucose for 24 h. Cells were then cultured under 2.5 or 25 mM Glc, or 25 mM 2DG for 24 h and collected for the ChIP assay. Primer pairs were designed according to a previous study [26].…”

Thioredoxin-interacting Protein (Txnip) Gene Expression

“…Unlike other cell types, which employ MondoA as a transcription factor partner for MLX (18,19), pancreatic cells appear to employ ChREBP as a dominant partner (over MondoA) for MLX on regulating Txnip expression (18,20). In rat insulinoma INS-1 cells, the Txnip expression was also significantly repressed by NaN 3 or rotenone, and the ChREBP protein level was not affected by these inhibitors (Fig.…”

Molecular Cloning and Mrna Expression Analysis of Sichuan White Goose (Anser Cygnoides) Chrebp Gene

“…Its molecular weight is 96 kDa, and it consists of 864 amino acids (Filhouland et al, 2013). This protein was found to bind the carbohydrate response element (ChoRE) and to be involved in the development of metabolic syndromes and glucose-inducible expression of several genes, including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase-1 (SCD1), thioredoxin-interacting protein (TXNIP), and fibroblast growth factor 21 (FGF21) (Katsurada et al, 1990;Lizuka et al, 2008;Cha-Molstad et al, 2009;Pang et al, 2009;Jeong et al, 2011;Zhang et al, 2015). Several lines of evidence suggest that ChREBP interacts with Max-like protein X (Mix) to form a heterodimer, and this ChREBP/Mix heterodimer binds to ChoRE for the activation of the ChoRE-containing promoters in response to high glucose (Stoeckman et al, 2004;Ma et al, 2005;Uyeda et al, 2006).…”