Deletion of the yeast homologue of frataxin, YFH1, results in mitochondrial iron accumulation and respiratory deficiency (petite formation). We used a genetic screen to identify mutants that modify iron-associated defects in respiratory activity in Δyfh1 cells. A deletion in the peroxisomal citrate synthase CIT2 in Δyfh1 cells decreased the rate of petite formation. Conversely, overexpression of CIT2 in Δyfh1 cells increased the rate of respiratory loss. Citrate toxicity in Δyfh1 cells was dependent on iron but was independent of mitochondrial respiration. Citrate toxicity was not restricted to iron-laden mitochondria but also occurred when iron accumulated in cytosol because of impaired vacuolar iron storage. These results suggest that high levels of citrate may promote iron-mediated tissue damage.
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