Mitochondrial proteomics of Drosophila melanogaster expressing the alternative oxidase under different dietary conditions

The mitochondrial oxidative phosphorylation process occurs via the coordinated action of five multienzymatic complexes that constitute the mitochondrial respiratory chain. Dysfunction in these complexes can lead to deficiency in ATP production, in addition to excessive formation of reactive oxygen species, which are related to a large number of diseases. The alternative oxidase (AOX) provides an alternative pathway to electron transfer in the respiratory chain, since it possesses chemical redox function similar to that of complexes III and IV. When AOX was expressed and tested in mitochondria of Drosophila melanogaster, mice and human cells in culture, which naturally do not express this enzyme, there was a decrease in the deleterious effects resulting from mitochondrial dysfunction, indicating its potential therapeutic use. However, AOX does not pump protons into the intermembrane space, and thus may be associated with a decreased membrane potential and ATP production, suggesting the need for nutrient-rich diets for complete development of AOX-expressing model organisms. We conducted developmental assays using nutrient-rich and -restricted diets and we have verified that in the nutritional restriction condition AOX caused an 80% drop in eclosion rate. To understand the molecular mechanisms involved in the observed phenotype, we investigated the pupal mitochondrial proteome in the pre-lethality stage. Data obtained from lines cultivated in a nutrient-rich diet showed that the Krebs cycle and lipid catabolism enzymes are overexpressed. The same pattern was observed for diet-restricted flies, indicating that AOX may lead to a more prominent, but less efficient bioenergetically, consumption of lipid storage obtained in the larval phase. This storage may be insufficient for completing metamorphosis when the flies are cultured in restricted diet. (AU)