title: c-Myc and ChREBP regulate glucose-mediated expression of the L-type pyruvate kinase gene in INS-1-derived 832/13 cells.
abstract: Increased glucose flux generates metabolic signals that control transcriptional programs through poorly understood mechanisms. Previously, we demonstrated a necessity in hepatocytes for c-Myc in the regulation of a prototypical glucose-responsive gene, L-type pyruvate kinase (L-PK) (Collier JJ, Doan TT, Daniels MC, Schurr JR, Kolls JK, Scott DK. J Biol Chem 278: 6588-6595, 2003). Pancreatic beta-cells have many features in common with hepatocytes with respect to glucose-regulated gene expression, and in the present study we determined whether c-Myc was required for the L-PK glucose response in insulin-secreting (INS-1)-derived 832/13 cells. Glucose increased c-Myc abundance and association with its heterodimer partner, Max. Manipulations that prevented the formation of a functional c-Myc/Max heterodimer reduced the expression of the L-PK gene. In addition, glucose augmented the binding of carbohydrate response element binding protein (ChREBP), c-Myc, and Max to the promoter of the L-PK gene in situ. The transactivation of ChREBP, but not of c-Myc, was dependent on high glucose concentrations in the contexts of either the L-PK promoter or a heterologous promoter. The glucose-mediated transactivation of ChREBP was independent of mutations that alter phosphorylation sites thought to regulate the cellular location of ChREBP. We conclude that maximal glucose-induced expression of the L-PK gene in INS-1-derived 832/13 cells involves increased c-Myc abundance, recruitment of c-Myc, Max, and ChREBP to the promoter, and a glucose-stimulated increase in ChREBP transactivation.
authors.affiliation: Division of Endocrinology and Metabolism, University of Pittsburgh School of Medicine, E1147 BST, 200 Lothrop St., Pittsburgh, PA 15261, USA.
authors.forename: J Jason
authors.initials: JJ
authors.lastname: Collier
authors.forename: Pili
authors.initials: P
authors.lastname: Zhang
authors.forename: Kim B
authors.initials: KB
authors.lastname: Pedersen
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Burke
authors.forename: John W
authors.initials: JW
authors.lastname: Haycock
authors.forename: Donald K
authors.initials: DK
authors.lastname: Scott
mesh_terms: D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001665:Binding Sites / Q000187:drug effects; D045744:Cell Line, Tumor; D019281:Dimerization; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism / Q000502:physiology*; D011770:Pyruvate Kinase / Q000235:genetics*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D014162:Transfection
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C499329:Max protein, rat; C442825:Mlxipl protein, rat; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D011770:Pyruvate Kinase; D005947:Glucose