title: The alternative oxidase, a tool for compensating cytochrome c oxidase deficiency in human cells.
abstract: In plants as well as in a number of micro-organisms, and in several animal phyla, but not in mammals, the alternative oxidase (AOX) possibly by-passes the cytochrome segment of the respiratory chain. The AOX is located at the inner surface of the inner mitochondrial membrane, being activated by over-reduction of the quinone pool and accumulation of keto-acids such as pyruvate. Since these conditions are frequently encountered in patients with mitochondrial diseases, we hypothesized that the expression of the ascidian Ciona intestinalis AOX might alleviate the consequences of a blockade of the cytochrome segment of the respiratory chain in human cells. We previously expressed the C. intestinalis AOX in human embryonic kidney (HEK 293-T-derived) cells conferring cyanide-resistance to cell respiration without any detectable detrimental effect (Hakkaart et al. 2006). We have now expressed the AOX in human cultured fibroblasts either with a functional respiratory chain (foreskin immortalized fibroblasts, BJ1-htert) or presenting a cytochrome c oxidase deficiency resulting from an impaired heme aa3 biogenesis. We used immortalized COX15-deficient skin fibroblasts from a patient who died from an early fatal cardiomyopathy. We found that the expression of the AOX in these cells was well tolerated and corrected for the various consequences of the cytochrome c oxidase deficiency in COX15-mutant cells, i.e. decreased cell respiration, glucose and pyruvate dependency. We thus validated our hypothesis that AOX could compensate for cytochrome c oxidase deficiency in human cells.
authors.affiliation: Inserm, U676 and Université Paris 7, Faculté de Médecine Denis Diderot, Paris, France.
authors.forename: Emmanuel P
authors.initials: EP
authors.lastname: Dassa
authors.forename: Eric
authors.initials: E
authors.lastname: Dufour
authors.forename: Sergio
authors.initials: S
authors.lastname: Goncalves
authors.forename: Howard T
authors.initials: HT
authors.lastname: Jacobs
authors.forename: Pierre
authors.initials: P
authors.lastname: Rustin
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D049109:Cell Proliferation / Q000187:drug effects; D019069:Cell Respiration / Q000187:drug effects; D002938:Ciona intestinalis / Q000201:enzymology; D003470:Culture Media; D003486:Cyanides / Q000633:toxicity; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D052816:Foreskin; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D024101:Mitochondrial Proteins; D010084:Oxidation-Reduction / Q000187:drug effects; D010088:Oxidoreductases / Q000378:metabolism*; D010940:Plant Proteins; D013379:Substrate Specificity / Q000187:drug effects; D000099188:Alternative Oxidase
chemical_list: D003470:Culture Media; D003486:Cyanides; D003576:Electron Transport Complex IV; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D000099188:Alternative Oxidase