Ligand-Bound GeneSwitch Causes Developmental Aberrations in Drosophila that Are Alleviated by the Alternative Oxidase.
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ABSTRACT:
SUBMITTER: Andjelkovic A
PROVIDER: S-EPMC5015941 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The xenotopic expression of the alternative oxidase AOX from the tunicate Ciona intestinalis in diverse models of human disease partially alleviates the phenotypic effects of mitochondrial respiratory chain defects. AOX is a non-proton pumping, mitochondrial inner membrane-bound, single-subunit enzyme that can bypass electron transport through the cytochrome segment, providing an additional site for ubiquinone reoxidation and oxygen reduction upon respiratory chain overload. We set out to investigate whether AOX expression in Drosophila could counteract the effects of mitochondrial DNA (mtDNA) replication defects caused by disturbances in the mtDNA helicase or DNA polymerase ?. We observed that the developmental arrest imposed by either the expression of mutant forms of these enzymes or their knockdown was not rescued by AOX. Considering also the inability of AOX to ameliorate the phenotype of tko25t, a fly mutant with mitochondrial translation deficiency, we infer that this alternative enzyme may not be applicable to cases of mitochondrial gene expression defects. Finding the limitations of AOX applicability will help establish the parameters for the future putative use of this enzyme in gene therapies for human mitochondrial diseases.
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Project description:Energetic insufficiency, excess production of reactive oxygen species (ROS), and aberrant signaling partially account for the diverse pathology of mitochondrial diseases. Whether interventions affecting ROS, a regulator of stem cell pools, could modify somatic stem cell homeostasis remains unknown. Previous data from mitochondrial DNA mutator mice showed that increased ROS leads to oxidative damage in erythroid progenitors, causing lifespan-limiting anemia. Also unclear is how ROS-targeted interventions affect terminally differentiated tissues. Here, we set out to test in mitochondrial DNA mutator mice how ubiquitous expression of the Ciona intestinalis alternative oxidase (AOX), which attenuates ROS production, affects murine stem cell pools. We found that AOX does not affect neural stem cells but delays the progression of mutator-driven anemia. Furthermore, when combined with the mutator, AOX potentiates mitochondrial stress and inflammatory responses in skeletal muscle. These differential cell type-specific findings demonstrate that AOX expression is not a global panacea for curing mitochondrial dysfunction. ROS attenuation must be carefully studied regarding specific underlying defects before AOX can be safely used in therapy.
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Project description:Despite the beneficial effects shown when the mitochondrial alternative oxidase AOX from Ciona intestinalis (Tunicata: Ascidiacea) is xenotopically expressed in mammalian and insect models, important detrimental outcomes have also been reported, raising concerns regarding its envisioned deployment as a therapy enzyme for human mitochondrial and related diseases. We have shown previously that AOX-expressing flies present a dramatic drop in pupal viability when the larvae are cultured on a low nutrient (LN) diet, indicating that AOX interferes with normal developmental metabolism. Here, we applied the metabolomics approach to gain insights into the molecular basis of the fatal developmental interaction between AOX expression and LN diet. We investigated the whole-body metabolome of AOX-expressing and control larvae cultured on SD and LN diets.
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