Boutoual 2018 Scientific Reports
|Boutoual, R., Meseguer, S., Villarroya, M., Martin-Hernandez, E., Errami, M., Martin, M. A., Casado, M., and Armengod, M. E. (2018) Defects in the mitochondrial-tRNA modification enzymes MTO1 and GTPBP3 promote different metabolic reprogramming through a HIF-PPARgamma-UCP2-AMPK axis. Scientific reports 8, 1163|
Abstract: Human proteins MTO1 and GTPBP3 are thought to jointly catalyze the modification of the wobble uridine in mitochondrial tRNAs. Defects in each protein cause infantile hypertrophic cardiomyopathy with lactic acidosis. However, the underlying mechanisms are mostly unknown. Using fibroblasts from an MTO1 patient and MTO1 silenced cells, we found that the MTO1 deficiency is associated with a metabolic reprogramming mediated by inactivation of AMPK, down regulation of the uncoupling protein 2 (UCP2) and transcription factor PPARγ, and activation of the hypoxia inducible factor 1 (HIF-1). As a result, glycolysis and oxidative phosphorylation are uncoupled, while fatty acid metabolism is altered, leading to accumulation of lipid droplets in MTO1 fibroblasts. Unexpectedly, this response is different from that triggered by the GTPBP3 defect, as GTPBP3-depleted cells exhibit AMPK activation, increased levels of UCP2 and PPARγ, and inactivation of HIF-1. In addition, fatty acid oxidation and respiration are stimulated in these cells. Therefore, the HIF-PPARγ-UCP2-AMPK axis is operating differently in MTO1- and GTPBP3-defective cells, which strongly suggests that one of these proteins has an additional role, besides mitochondrial-tRNA modification. This work provides new and useful information on the molecular basis of the MTO1 and GTPBP3 defects and on putative targets for therapeutic intervention.
• Keywords: Rare diseases; Mitochondrial diseases; OXPHOS diseases; Mitochondrial translation diseases; MnmE; MnmG; tRNA modification; Oxygen consumption rate; Fatty acid oxidation; Glycolysis; OXPHOS uncoupling; Lipotoxicity; Hypertrophic cardiomyopathy; Lactic acidosis
• O2k-Network Lab: Salvador Meseguer (CIPF-Valencia) and Marta Casado (IBV-Valencia)
Labels: MiParea: Respiration, mtDNA;mt-genetics, Patients Pathology: Cardiovascular Stress:Mitochondrial disease Organism: Human Tissue;cell: Other cell lines, Fibroblast Preparation: Intact cells, Permeabilized cells Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase, Uncoupling protein Regulation: ATP production, Coupling efficiency;uncoupling, Inhibitor, Substrate, Uncoupler, Fatty acid Coupling state: LEAK, ROUTINE, OXPHOS, ET Pathway: F, S, Gp HRR: Oxygraph-2k