Glucose-6-Phosphate Upregulates Txnip Expression by Interacting With MondoA

Area of Science:

• Cellular metabolism
• Molecular biology
• Gene regulation

Background:

• Glucose metabolism is central to cellular energy production and biosynthesis.
• Glycolysis and the pentose phosphate pathway initiate with glucose phosphorylation to glucose-6-phosphate (G6P).
• The transcription factor MondoA/Mlx plays a role in cellular stress responses and metabolic regulation.

Purpose of the Study:

• To investigate the role of glucose-6-phosphate (G6P) in regulating the MondoA/Mlx transcription factor.
• To elucidate the mechanism by which G6P influences gene expression, specifically Txnip.
• To characterize the structural basis of G6P binding to MondoA.

Main Methods:

• Endogenous knockdown experiments to assess the necessity of G6P.
• Electrophoretic Mobility Shift Assay (EMSA) to confirm G6P binding to MondoA/Mlx.
• In silico molecular modeling, docking, and binding free energy calculations to predict MondoA structure and G6P interaction.
• Free energy decomposition and mutational analyses to identify key residues involved in G6P binding.

Main Results:

• Glucose-6-phosphate (G6P) was confirmed as the metabolic intermediate that activates the MondoA/Mlx heterocomplex.
• G6P binding to MondoA/Mlx directly leads to the upregulation of Txnip gene expression.
• Structural and computational analyses revealed specific residues (GKL139-141) in MondoA critical for G6P binding and activation.

Conclusions:

• Glucose-6-phosphate (G6P) acts as a direct metabolic sensor for the MondoA/Mlx transcription factor.
• The MondoA/Mlx-G6P interaction is a key regulatory step controlling Txnip expression.
• Understanding this signaling pathway provides insights into glucose metabolism and cellular stress responses.