Glucose sensing by MondoA:Mlx complexes: a role for hexokinases and direct regulation of thioredoxin-interacting protein expression.
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.
Stoltzman
Carrie A
CA
Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112-5550, USA.
Peterson
Christopher W
CW
Breen
Kevin T
KT
Muoio
Deborah M
DM
Billin
Andrew N
AN
Ayer
Donald E
DE
D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism*; D015374:Biosensing Techniques; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D006593:Hexokinase / Q000378:metabolism*; D006801:Humans; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D014158:Transcription, Genetic / Q000187:drug effects
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D002352:Carrier Proteins; C403128:MLX protein, human; C485496:MLXIP protein, human; C486715:TXNIP protein, human; D006593:Hexokinase; D005947:Glucose