NADH Shuttling Couples Cytosolic Reductive Carboxylation of Glutamine with Glycolysis in Cells with Mitochondrial Dysfunction

The bioenergetics and molecular determinants of the metabolic response to mitochondrial dysfunction are incompletely understood, in part due to a lack of appropriate isogenic cellular models of primary mitochondrial defects. Here, we capitalize on a recently developed cell model with defined levels of m.8993T>G mutation heteroplasmy, mTUNE, to investigate the metabolic underpinnings of mitochondrial dysfunction. We found that impaired utilization of reduced nicotinamide adenine dinucleotide (NADH) by the mitochondrial respiratory chain leads to cytosolic reductive carboxylation of glutamine as a new mechanism for cytosol-confined NADH recycling supported by malate dehydrogenase 1 (MDH1). We also observed that increased glycolysis in cells with mitochondrial dysfunction is associated with increased cell migration in an MDH1-dependent fashion. Our results describe a novel link between glycolysis and mitochondrial dysfunction mediated by reductive carboxylation of glutamine. [Display omitted] •mTUNE is a new model of tunable mitochondrial dysfunction•Metabolic model predicts link between reductive carboxylation and glycolysis in mTUNE•Reductive carboxylation is regulated by mitochondrial NADH redox state•MDH1 couples reductive carboxylation to glycolysis and supports cell migration The connection between mitochondrial dysfunction and changes in cell metabolism is poorly understood. Capitalizing on a model of mitochondrial DNA mutation, we found that impaired mitochondrial metabolism leads to cytosolic reductive carboxylation of glutamine, which regenerates NADH via malate dehydrogenase to fuel glycolysis. This pathway also supports cell migration.