Our data suggest that the role of mitochondrial ETC function in modulating animal aging is evolutionarily conserved and might also operate in humans. Furthermore, our findings suggest that the longer life span of flies with reduced ETC gene expression cannot simply be attributed to reduced energy production leading to decreased "rate of living."

More than 130 different mutations in the Cu/Zn superoxide dismutase (SOD1) gene have been associated with Amyotrophic lateral sclerosis (ALS) but the mechanism of this toxicity remains controversial. To gain insight into the importance of the zinc site in the pathogenesis of SOD1 in vivo, we generated a Drosophila model with transgenic expression of a zinc-deficient human SOD1. Expression of zinc-deficient SOD1 in Drosophila resulted in a progressive movement defect with associated mitochondrial cristae vacuolization and reductions in ATP levels. Furthermore, these flies are sensitized to mitochondrial toxins, paraquat and zinc. Importantly, we show that the zinc-deficient SOD1-induced motor defect can be ameliorated by supplementing the endogenous fly respiratory chain machinery with the single-subunit NADH–ubiquinone oxidoreductase (Ndi1) from yeast. These results demonstrate that zinc-deficient SOD1 is neurotoxic in vivo and suggest that mitochondrial dysfunction plays a critical role in this toxicity. The robust behavioral, pathological and biochemical phenotypes conferred by zinc-deficient SOD1 in Drosophila have general implications for the role of the zinc ion in both familial and sporadic ALS.