c-Myc and ChREBP regulate glucose-mediated expression of the L-type pyruvate kinase gene in INS-1-derived 832/13 cells

Am J Physiol Endocrinol Metab. 2007 Jul;293(1):E48-56. doi: 10.1152/ajpendo.00357.2006. Epub 2007 Mar 6.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / genetics
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / metabolism
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / physiology*
  • Binding Sites / drug effects
  • Cell Line, Tumor
  • Dimerization
  • Gene Expression Regulation, Enzymologic* / drug effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • Glucose / pharmacology
  • Promoter Regions, Genetic / drug effects
  • Proto-Oncogene Proteins c-myc / metabolism
  • Proto-Oncogene Proteins c-myc / physiology*
  • Pyruvate Kinase / genetics*
  • RNA, Small Interfering / pharmacology
  • Rats
  • Transfection

Substances

  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Max protein, rat
  • Mlxipl protein, rat
  • Proto-Oncogene Proteins c-myc
  • RNA, Small Interfering
  • Pyruvate Kinase
  • Glucose