Glutathione-dependent redox status of frataxin-deficient cells in a yeast model of Friedreich’s ataxia

Laboratoire d'Ingénierie des Protéines et Contrôle Métabolique, Département de Biologie des Génomes, Institut Jacques Monod, UMR 7592, CNRS, Universités Paris 6 and 7, 2 Place Jussieu, Tour 43, 75251 Paris Cedex 05, France.
Human Molecular Genetics (Impact Factor: 6.39). 07/2008; 17(18):2790-802. DOI: 10.1093/hmg/ddn178
Source: PubMed


Friedreich's ataxia is a neurodegenerative disease caused by reduced expression of the mitochondrial protein frataxin. The main phenotypic features of frataxin-deficient human and yeast cells include iron accumulation in mitochondria, iron-sulphur cluster defects and high sensitivity to oxidative stress. Glutathione is a major protective agent against oxidative damage and glutathione-related systems participate in maintaining the cellular thiol/disulfide status and the reduced environment of the cell. Here, we present the first detailed biochemical study of the glutathione-dependent redox status of wild-type and frataxin-deficient cells in a yeast model of the disease. There were five times less total glutathione (GSH+GSSG) in frataxin-deficient cells, imbalanced GSH/GSSG pools and higher glutathione peroxidase activity. The pentose phosphate pathway was stimulated in frataxin-deficient cells, glucose-6-phosphate dehydrogenase activity was three times higher than in wild-type cells and this was coupled to a defect in the NADPH/NADP(+) pool. Moreover, analysis of gene expression confirms the adaptative response of mutant cells to stress conditions and we bring evidence for a strong relation between the glutathione-dependent redox status of the cells and iron homeostasis. Dynamic studies show that intracellular glutathione levels reflect an adaptation of cells to iron stress conditions, and allow to distinguish constitutive stress observed in frataxin-deficient cells from the acute response of wild-type cells. In conclusion, our findings provide evidence for an impairment of glutathione homeostasis in a yeast model of Friedreich's ataxia and identify glutathione as a valuable indicator of the redox status of frataxin-deficient cells.

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Available from: Renata Santos
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    • "Total glutathione levels were determined using 20 µg proteins of crude mitochondrial pellet or cytosol from striatum and midbrain with a modified version of the recycling enzymatic assay based on the reduction of each GSSG molecule to give two GSH molecules [51]. Standard curves were obtained with various concentrations of GSSG and the values were thus expressed as GSSG equivalent. "
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    • "RT-qPCR analysis was performed exactly as described previously (21,34). Primer pairs used were: 5′-TCGCGTAAGGAACAGTTAGACA-3′ and 5′-GCTCTGCAGTGGCTTTCTTC-3′ for the APN1 gene; 5′-TAAGGGGCTTTGGACAGAAA-3′ and 5′-ATCATCCGGTGGCAAGAA-3′ for the NTG1 gene and 5′-CCAGGGGTAAGAGGTGTGATT-3′ and 5′-TCCAATTGATGAAATTTGGAAGA-3′ for the NTG2 gene or were described previously for the other genes (21,34). Relative expression was calculated using the equation described (53). "
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    • "Glutathione is a major protective antioxidant in yeast cells. We have shown that Dyfh1 cells have low total glutathione content and a reduced GSH/GSSG ratio [8]. Since the double Dyfh1Dyca1 mutant was more resistant to H 2 O 2 , we tested if glutathione antioxidant defense was altered. "
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