title: 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.
abstract: Whether glucose-6-phosphate (G6P) or xylulose-5-phosphate (X5P) is the signaling molecule for carbohydrate response element binding protein (ChREBP) transactivation has been controversial. In this study, we tested the role of G6P and X5P in the regulation of ChREBP transactivation in the pancreatic β cell line, INS-1E. In contrast to glucose, which can be converted into both G6P and X5P, 2DG is only converted into 2DG6P. The potency of 2-deoxy-glucose (2DG) to induce Chrebp target mRNA was weaker and less persistent than that of glucose. Moreover, the results from siRNA knockdown of ChREBP, a reporter assay involving the pGL3 promoter with carbohydrate response element (ChoRE), and a ChIP assay with an anti-ChREBP antibody revealed that 2DG does not increase ChREBP transactivity in INS-1E cells. In accordance with these results, transfection of siRNA against Chrebp tended to reduce glucose-stimulated, but not 2DG-stimulated, expression of ChREBP target genes. Conversely, the expression of xylulokinase (Xylb), which converts xylitol to X5P, was much lower than in primary hepatocytes. In INS-1E cells infected by adenovirus bearing Xylb cDNA, xylitol increased expression of ChREBP target genes, although with a weaker potency than glucose. Finally, X5P partly induced ChREBP transactivity in INS-1E cells overexpressing Xylb cDNA. In conclusion, G6P and X5P can activate ChREBP transactivity, but their potencies to induce ChREBP transactivity were much lower than that of glucose, suggesting that other factors such as fructose 2,6-bisphosphate may be needed for full activation of glucose-induced gene expression.
authors.affiliation: Gifu University Hospital Center for Nutritional Support and Infection Control, Gifu 501-1194, Japan. kiizuka@gifu-u.ac.jp
authors.forename: Katsumi
authors.initials: K
authors.lastname: Iizuka
authors.forename: Wudelehu
authors.initials: W
authors.lastname: Wu
authors.forename: Yukio
authors.initials: Y
authors.lastname: Horikawa
authors.forename: Jun
authors.initials: J
authors.lastname: Takeda
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003847:Deoxyglucose / Q000378:metabolism; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism*; D019298:Glucose-6-Phosphate / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D010428:Pentosephosphates / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D015533:Transcriptional Activation; D014993:Xylitol / Q000378:metabolism
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C442825:Mlxipl protein, rat; D010428:Pentosephosphates; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D019298:Glucose-6-Phosphate; C031625:xylulose-5-phosphate; D003847:Deoxyglucose; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D005947:Glucose; D014993:Xylitol