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Frataxin-deficient cardiomyocytes present an altered thiol-redox state which targets actin and pyruvate dehydrogenase.

ABSTRACT: Friedreich ataxia (FA) is a cardioneurodegenerative disease caused by deficient frataxin expression. This mitochondrial protein has been related to iron homeostasis, energy metabolism, and oxidative stress. Previously, we set up a cardiac cellular model of FA based on neonatal rat cardiac myocytes (NRVM) and lentivirus-mediated frataxin RNA interference. These frataxin-deficient NRVMs presented lipid droplet accumulation, mitochondrial swelling and signs of oxidative stress. Therefore, we decided to explore the presence of protein thiol modifications in this model. With this purpose, reduced glutathione (GSH) levels were measured and the presence of glutathionylated proteins was analyzed. We observed decreased GSH content and increased presence of glutahionylated actin in frataxin-deficient NRVMs. Moreover, the presence of oxidized cysteine residues was investigated using the thiol-reactive fluorescent probe iodoacetamide-Bodipy and 2D-gel electrophoresis. With this approach, we identified two proteins with altered redox status in frataxin-deficient NRVMs: electron transfer flavoprotein-ubiquinone oxidoreductase and dihydrolipoyl dehydrogenase (DLDH). As DLDH is involved in protein-bound lipoic acid redox cycling, we analyzed the redox state of this cofactor and we observed that lipoic acid from pyruvate dehydrogenase was more oxidized in frataxin-deficient cells. Also, by targeted proteomics, we observed a decreased content on the PDH A1 subunit from pyruvate dehydrogenase. Finally, we analyzed the consequences of supplementing frataxin-deficient NRVMs with the PDH cofactors thiamine and lipoic acid, the PDH activator dichloroacetate and the antioxidants N-acetyl cysteine and Tiron. Both dichloroacetate and Tiron were able to partially prevent lipid droplet accumulation in these cells. Overall, these results indicate that frataxin-deficient NRVMs present an altered thiol-redox state which could contribute to the cardiac pathology.

SUBMITTER: Purroy R

PROVIDER: S-EPMC7152683 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Frataxin-deficient cardiomyocytes present an altered thiol-redox state which targets actin and pyruvate dehydrogenase.

Purroy Rosa R Medina-Carbonero Marta M Ros Joaquim J Tamarit Jordi J

Redox biology 20200405

Friedreich ataxia (FA) is a cardioneurodegenerative disease caused by deficient frataxin expression. This mitochondrial protein has been related to iron homeostasis, energy metabolism, and oxidative stress. Previously, we set up a cardiac cellular model of FA based on neonatal rat cardiac myocytes (NRVM) and lentivirus-mediated frataxin RNA interference. These frataxin-deficient NRVMs presented lipid droplet accumulation, mitochondrial swelling and signs of oxidative stress. Therefore, we decide ...[more]

PMID: 32279039

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Project description:The pyruvate dehydrogenase complex (PDHC) catalyzes the oxidative decarboxylation of pyruvate, yielding acetyl coenzyme A (acetyl-CoA) and CO2 The PDHC-deficient Corynebacterium glutamicum ΔaceE strain therefore lacks an important decarboxylation step in its central metabolism. Additional inactivation of pyc, encoding pyruvate carboxylase, resulted in a >15-h lag phase in the presence of glucose, while no growth defect was observed on gluconeogenetic substrates, such as acetate. Growth was successfully restored by deletion of ptsG, encoding the glucose-specific permease of the phosphotransferase system (PTS), thereby linking the observed phenotype to the increased sensitivity of the ΔaceE Δpyc strain to glucose catabolism. In this work, the ΔaceE Δpyc strain was used to systematically study the impact of perturbations of the intracellular CO2/HCO3- pool on growth and anaplerotic flux. Remarkably, all measures leading to enhanced CO2/HCO3- levels, such as external addition of HCO3-, increasing the pH, or rerouting metabolic flux via the pentose phosphate pathway, at least partially eliminated the lag phase of the ΔaceE Δpyc strain on glucose medium. In accordance with these results, inactivation of the urease enzyme, lowering the intracellular CO2/HCO3- pool, led to an even longer lag phase, accompanied by the excretion of l-valine and l-alanine. Transcriptome analysis, as well as an adaptive laboratory evolution experiment with the ΔaceE Δpyc strain, revealed the reduction of glucose uptake as a key adaptive measure to enhance growth on glucose-acetate mixtures. Taken together, our results highlight the significant impact of the intracellular CO2/HCO3- pool on metabolic flux distribution, which becomes especially evident in engineered strains exhibiting low endogenous CO2 production rates, as exemplified by PDHC-deficient strains.IMPORTANCE CO2 is a ubiquitous product of cellular metabolism and an essential substrate for carboxylation reactions. The pyruvate dehydrogenase complex (PDHC) catalyzes a central metabolic reaction contributing to the intracellular CO2/HCO3- pool in many organisms. In this study, we used a PDHC-deficient strain of Corynebacterium glutamicum, which additionally lacked pyruvate carboxylase (ΔaceE Δpyc). This strain featured a >15-h lag phase during growth on glucose-acetate mixtures. We used this strain to systematically assess the impact of alterations in the intracellular CO2/HCO3- pool on growth in glucose-acetate medium. Remarkably, all measures enhancing CO2/HCO3- levels successfully restored growth. These results emphasize the strong impact of the intracellular CO2/HCO3- pool on metabolic flux, especially in strains exhibiting low endogenous CO2 production rates.

Dataset Information

Frataxin-deficient cardiomyocytes present an altered thiol-redox state which targets actin and pyruvate dehydrogenase.

Publications

Frataxin-deficient cardiomyocytes present an altered thiol-redox state which targets actin and pyruvate dehydrogenase.

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