Manganese Is the Link between Frataxin and Iron-Sulfur Deficiency in the Yeast Model of Friedreich Ataxia

Abstract

Friedreich ataxia is a human neurodegenerative and myocardial disease caused by decreased expression of the mitochondrial protein frataxin. Proteomic analysis of the mutant yeast model of Friedreich ataxia presented in this paper reveals that these cells display increased amounts of proteins involved in antioxidant defenses, including manganese-superoxide dismutase. This enzyme shows, however, lower activity than that found in wild type cells. Our results indicate that this lack of activity is a consequence of cellular manganese deficiency, because in manganese-supplemented cultures, cell manganese content, and manganese-superoxide dismutase activity were restored. One of the hallmarks of Friedreich ataxia is the decreased activity of iron/sulfur-containing enzymes. The activities of four enzymes of this group (aconitase, glutamate synthase, succinate dehydrogenase, and isopropylmalate dehydratase) have been analyzed for the effects of manganese supplementation. Enzyme activities were recovered by manganese treatment, except for aconitase, for which, a specific interaction with frataxin has been demonstrated previously. Similar results were obtained when cells were grown in iron-limited media suggesting that manganese-superoxide dismutase deficiency is a consequence of iron overload. In conclusion, these data indicate that generalized deficiency of iron-sulfur protein activity could be a consequence of manganese-superoxide dismutase deficiency, and consequently, it opens new strategies for Friedreich ataxia treatment.

Frataxin Depletion in Yeast Triggers Up-regulation of Iron Transport Systems before Affecting Iron-Sulfur Enzyme Activities

“…6A). This induction was also observed previously in ⌬yfh1 mutants (17,44) and may be the consequence of the oxidative stress conditions exerted by iron overload. Enzymatic activities were measured using zymograms, which allow a clear differentiation of both isoenzymes (Fig.…”

“…First, we observed the presence of decreased Mn-SOD activity in ⌬yfh1, which compromise the activity of some iron-sulfur-containing enzymes (17). We also observed that decreased activities of SOD1 and SOD2 contribute to oxidative damage to a specific subset of proteins by increasing the presence of chelatable iron in ⌬yfh1 cells (18).…”

“…Also in yeast, aconitase activity is preserved in ⌬yfh1 cells grown under strict anaerobic conditions (16). Moreover, in two previous studies (17,18), we observed that YFH1 null mutations lead to the impairment of superoxide dismutase (SOD) 2 activities. When these activities were restored, the activities of several iron-sulfur-containing enzymes were also recovered, suggesting that ironsulfur deficiency in ⌬yfh1 yeasts is due to the lack of SOD activities.…”

Isc1p Plays a Key Role in Hydrogen Peroxide Resistance and Chronological Lifespan through Modulation of Iron Levels and Apoptosis

“…Iron overload in mitochondria of cells lacking frataxin, a yeast model of Friedreich ataxia, results in MnSOD deficiency and increases oxidative stress sensitivity (Desmyter et al, 2004;Irazusta et al, 2006). However, the analysis of MnSOD showed that its activity was similar in parental and isc1⌬ cells ( Figure 4B).…”

Model-based identification of drug targets that revert disrupted metabolism and its application to ageing

“…The days indication refers to the number of day passed since reaching stationary phase. O 2 À detection was carried out using dihydroethidium 62,63 . One micolitre of cell culture was centrifuged and resuspended in 1 ml PBS buffer plus 0.1% glycerol (4°C).…”