title: Expression of alternative oxidase in Drosophila ameliorates diverse phenotypes due to cytochrome oxidase deficiency.
abstract: Mitochondrial dysfunction is a significant factor in human disease, ranging from systemic disorders of childhood to cardiomyopathy, ischaemia and neurodegeneration. Cytochrome oxidase, the terminal enzyme of the mitochondrial respiratory chain, is a frequent target. Lower eukaryotes possess alternative respiratory-chain enzymes that provide non-proton-translocating bypasses for respiratory complexes I (single-subunit reduced nicotinamide adenine dinucleotide dehydrogenases, e.g. Ndi1 from yeast) or III + IV [alternative oxidase (AOX)], under conditions of respiratory stress or overload. In previous studies, it was shown that transfer of yeast Ndi1 or Ciona intestinalis AOX to Drosophila was able to overcome the lethality produced by toxins or partial knockdown of complex I or IV. Here, we show that AOX can provide a complete or substantial rescue of a range of phenotypes induced by global or tissue-specific knockdown of different cIV subunits, including integral subunits required for catalysis, as well as peripheral subunits required for multimerization and assembly. AOX was also able to overcome the pupal lethality produced by muscle-specific knockdown of subunit CoVb, although the rescued flies were short lived and had a motility defect. cIV knockdown in neurons was not lethal during development but produced a rapidly progressing locomotor and seizure-sensitivity phenotype, which was substantially alleviated by AOX. Expression of Ndi1 exacerbated the neuronal phenotype produced by cIV knockdown. Ndi1 expressed in place of essential cI subunits produced a distinct residual phenotype of delayed development, bang sensitivity and male sterility. These findings confirm the potential utility of alternative respiratory chain enzymes as tools to combat mitochondrial disease, while indicating important limitations thereof.
authors.affiliation: Institute of Biomedical Technology and Tampere University Hospital, University of Tampere, FI-33014 Tampere, Finland.
authors.forename: Kia K
authors.initials: KK
authors.lastname: Kemppainen
authors.forename: Juho
authors.initials: J
authors.lastname: Rinne
authors.forename: Ashwin
authors.initials: A
authors.lastname: Sriram
authors.forename: Matti
authors.initials: M
authors.lastname: Lakanmaa
authors.forename: Akbar
authors.initials: A
authors.lastname: Zeb
authors.forename: Tea
authors.initials: T
authors.lastname: Tuomela
authors.forename: Anna
authors.initials: A
authors.lastname: Popplestone
authors.forename: Satpal
authors.initials: S
authors.lastname: Singh
authors.forename: Alberto
authors.initials: A
authors.lastname: Sanz
authors.forename: Pierre
authors.initials: P
authors.lastname: Rustin
authors.forename: Howard T
authors.initials: HT
authors.lastname: Jacobs
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D030401:Cytochrome-c Oxidase Deficiency / Q000150:complications* / Q000235:genetics / Q000378:metabolism; D002658:Developmental Disabilities / Q000209:etiology / Q000517:prevention & control*; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D007248:Infertility, Male / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D019636:Neurodegenerative Diseases / Q000209:etiology / Q000517:prevention & control*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099188:Alternative Oxidase
chemical_list: D003576:Electron Transport Complex IV; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D012333:RNA, Messenger; D000099188:Alternative Oxidase