Functional consequences of the 3460-bp mitochondrial DNA mutation associated with Leber’s hereditary optic neuropathy

Complex I is the largest of the mitochondrial respiratory chain proteins, and contains subunits encoded by both mitochondrial and nuclear genomes. Leber’s hereditary optic neuropathy has been clearly linked to mutations of mitochondrial DNA complex I genes, and variable complex I functional defects...

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Bibliographic Details
Published in:Journal of the neurological sciences 1999-05, Vol.165 (1), p.10-17
Main Authors: Cock, H.R, Cooper, J.M, Schapira, A.H.V
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - biosynthesis
Adult
ATP
Biological and medical sciences
Complex I
Diseases of visual field, optic nerve, optic chiasma and optic tracts
DNA, Mitochondrial - genetics
Electron Transport - genetics
Electron Transport - physiology
Electron Transport Complex I
Fibroblasts
Humans
Leber’s hereditary optic neuropathy
Medical sciences
Middle Aged
Mitochondria
Mitochondria, Muscle - chemistry
Mitochondria, Muscle - enzymology
Mitochondrial DNA
Mutation - genetics
NAD - metabolism
NADH, NADPH Oxidoreductases - biosynthesis
NADH, NADPH Oxidoreductases - genetics
Ophthalmology
Optic Atrophies, Hereditary - genetics
Reverse Transcriptase Polymerase Chain Reaction
Rotenone - pharmacology
Uncoupling Agents - pharmacology
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Summary:Complex I is the largest of the mitochondrial respiratory chain proteins, and contains subunits encoded by both mitochondrial and nuclear genomes. Leber’s hereditary optic neuropathy has been clearly linked to mutations of mitochondrial DNA complex I genes, and variable complex I functional defects have been reported. We have confirmed an approximate 60% defect in mitochondrial NADH CoQ1 reductase activity in cultured fibroblasts bearing the 3460-bp G to A mutation within the ND1 gene. However complex I-linked ATP synthesis was found to be normal in these fibroblasts. A 60% rotenone-induced decrease in complex I activity was shown to reduce ATP synthesis in normal fibroblasts, indicating that this level of complex I activity was below the threshold required to affect ATP synthesis. Although 3460 LHON mitochondria were less sensitive to rotenone inhibition, this did not explain the decreased complex I activity as the rotenone insensitive activity was not increased, nor did the inhibitor diphenyleneiodonium inhibit the NADH CoQ1 reductase activity to a greater extent. Decreased NADH cytochrome c reductase activity in cybrids homoplasmic for the 3460 LHON mtDNA mutation confirmed that the decrease in complex I activity was not specific to the assay used and was not caused by inhibitory effects of ubiquinone analogues used in the NADH CoQ1 reductase assay. These findings have important implications for our understanding of complex I dysfunction in the pathogenesis of 3460 Leber’s hereditary optic neuropathy.
ISSN:0022-510X
1878-5883
DOI:10.1016/S0022-510X(99)00088-X