Abstract
Glucose and glutamine are abundant nutrients required for cell growth, yet how cells sense and adapt to changes in their levels is not well understood. The MondoA transcription factor forms a heterocomplex with its obligate partner Mlx to regulate approximately 75% of glucose-dependent transcription. By mediating glucose-induced activation of thioredoxin-interacting protein (TXNIP), MondoA:Mlx complexes directly repress glucose uptake. We show here that glutamine inhibits transcriptional activation of TXNIP by triggering the recruitment of a histone deacetylase-dependent corepressor to the amino terminus of MondoA. Therefore, in the presence of both glucose and glutamine, TXNIP expression is low, which favors glucose uptake and aerobic glycolysis; the Warburg effect. Consistent with MondoA functioning upstream of TXNIP, MondoA knockdown reduces TXNIP expression, elevates glucose uptake and stimulates cell proliferation. Although glutamine has many intracellular fates, a cell permeable analog of a tricarboxylic acid cycle (TCA) intermediate, alpha-ketoglutarate, also blocks the transcriptional activity of MondoA at the TXNIP promoter and stimulates glucose uptake. Together our data suggest that glutamine-dependent mitochondrial anapleurosis dictates glucose uptake and aerobic glycolysis by blocking MondoA:Mlx-dependent transcriptional activation of TXNIP. We propose that this previously unappreciated coordination between glutamine and glucose utilization defines a metabolic checkpoint that restricts cell growth when subthreshold levels of these essential nutrients are available.