Glucose sensing by MondoA:Mlx complexes: a role for hexokinases and direct regulation of thioredoxin-interacting protein expression

Proc Natl Acad Sci U S A. 2008 May 13;105(19):6912-7. doi: 10.1073/pnas.0712199105. Epub 2008 May 5.

Abstract

Glucose is a fundamental metabolite, yet how cells sense and respond to changes in extracellular glucose concentration is not completely understood. We recently reported that the MondoA:Mlx dimeric transcription factor directly regulates glycolysis. In this article, we consider whether MondoA:Mlx complexes have a broader role in sensing and responding to glucose status. In their latent state, MondoA:Mlx complexes localize to the outer mitochondrial membrane, yet shuttle between the mitochondria and the nucleus. We show that MondoA:Mlx complexes accumulate in the nucleus in response to glucose and 2-deoxyglucose (2-DG). Furthermore, nuclear localization of MondoA:Mlx depends on the enzymatic activity of hexokinases. These enzymes catalyze conversion of glucose to glucose-6-phosphate (G6P), which is the first step in the glycolytic pathway. Together, these findings suggest that MondoA:Mlx monitors intracellular G6P concentration and translocates to the nucleus when levels of this key metabolite increase. Transcriptional profiling experiments demonstrate that MondoA is required for >75% of the 2-DG-induced transcription signature. We identify thioredoxin-interacting protein (TXNIP) as a direct and glucose-regulated MondoA:Mlx transcriptional target. Furthermore, MondoA:Mlx complexes, via their regulation of TXNIP, are potent negative regulators of glucose uptake. These studies suggest a key role for MondoA:Mlx complexes in the adaptive transcriptional response to changes in extracellular glucose concentration and peripheral glucose uptake.

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 / metabolism*
  • Biosensing Techniques*
  • Carrier Proteins / genetics*
  • Carrier Proteins / metabolism
  • Cell Line
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Gene Expression Regulation* / drug effects
  • Glucose / metabolism*
  • Glucose / pharmacology
  • Hexokinase / metabolism*
  • Humans
  • Protein Transport / drug effects
  • Rats
  • Transcription, Genetic / drug effects

Substances

  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Carrier Proteins
  • MLX protein, human
  • MLXIP protein, human
  • TXNIP protein, human
  • Hexokinase
  • Glucose