Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.6.5.3 (complex I)
8,901 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been suggested that dystonia is caused by an autosomal gene with reduced penetrance and a consequent biochemical abnormality affecting cell activity within the basal ganglia. No consistent biochemical disturbance has been identified. In the present study, activities of the mitochondrial electron transfer complexes were measured in platelets of 31 patients with idiopathic dystonia. Enzyme assays of these patients were compared to measurements in 28 control subjects. A significant decrease of complex I activity was observed in the majority of the patients, whereas the activities of other electron transfer complexes were normal. The severity of the complex I defect was more pronounced in patients with the segmental or generalized form than in those with focal dystonia. Complex I activity was not age dependent in the patients or control subjects. Although the electron pathway in complex I is disturbed in patients with idiopathic dystonia, complex I protein content seems to be normal. Whether abnormalities of complex I activity play a role in the pathogenesis of idiopathic dystonia remains to be determined.
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PMID:Electron transfer complex I defect in idiopathic dystonia. 144 49

We investigated a family with Leber's hereditary optic neuropathy in which affected individuals were homoplasmic for the point mutation of the NADH-dehydrogenase 4 gene of mitochondrial DNA, described by Wallace and colleagues in 1988. The proband had bilateral optic atrophy, tremor, dystonia, and sharply defined lesions in the putamen on magnetic resonance images. Optic atrophy was found in another 3 of 13 investigated relatives on the maternal side. Additional neurological signs were found but only in patients with optic neuropathy. The morphological appearance and the respiratory chain function of muscle tissue were investigated in the proband, his mother, and 3 siblings. Polarographic measurements revealed complex I deficiency in the 5 investigated subjects. Morphological changes of mitochondria were found in 4 of these subjects. There was no decrease in complex I activity measured as NADH ferricyanide reductase or rotenone-sensitive NADH cytochrome c reductase activities. In other cases with complex I deficiency, good agreement between polarographic and spectrophotometric measurements was found. This study showed that there is decreased activity of complex I of the respiratory chain in muscle and that cerebral striatal lesions occur in Leber's hereditary optic neuropathy with the NADH-dehydrogenase 4 gene point mutation.
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PMID:Leber's hereditary optic neuropathy and complex I deficiency in muscle. 176 94

A novel point mutation in the ND6 subunit of complex I at position 14,459 of the mitochondrial DNA (MTND6*LDY T14459A) was identified as a candidate mutation for the highly tissue-specific disease. Leber's hereditary optic neuropathy plus dystonia. Since the MTND6*LDYT14459A mutation was identified in a single family, other pedigrees with the mutation are needed to confirm its association with the disease. Clinical, biochemical, and genetic characterization is reported in two additional pedigrees. Leber's hereditary optic neuropathy developed in two family members in one pedigree. The daughter had clinically silent basal ganglia lesions. In a second pedigree, a single individual presented with childhood-onset generalized dystonia and bilateral basal ganglia lesions. Patient groups that included individuals with Leigh's disease, dystonia plus complex neurodegeneration, and Leber's hereditary optic neuropathy did not harbor the MTND6*LDYT14459A mutation, suggesting that this mutation displays a high degree of tissue specificity, thus producing a narrow phenotypic range. These results confirm the association of the MTND6*LDYT14459A mutation with Leber's hereditary optic neuropathy and/or dystonia. As the first genetic abnormality that has been identified to cause generalized dystonia, this mutation suggests that nuclear DNA or mitochondrial DNA mutations in oxidative phosphorylation genes are important considerations in the pathogenesis of dystonia.
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PMID:Leber's hereditary optic neuropathy plus dystonia is caused by a mitochondrial DNA point mutation. 765 63

An increasing number of neurodegenerative diseases seem to be associated with or even due to disturbances of cerebral energy metabolism. One generally accepted example is complex I deficiency in substantia nigra from patients with Parkinson's disease. Reports on a complex I defect in platelets from patients with dystonia led us to check for disturbances of the respiratory chain or of the mitochondrial genome in isolated mitochondria from patients with focal or generalized dystonia. We could not confirm the idea of mitochondrial disturbance in platelets from patients with dystonia because we did not find abnormal enzyme activities or any deletions of the mitochondrial genome. Thus, we do not think that blood cells such as platelets can serve as markers for neurodegenerative disorders such as dystonia.
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PMID:Respiratory chain and mitochondrial deoxyribonucleic acid in blood cells from patients with focal and generalized dystonia. 784 98

We report two brothers with a glutaric aciduria type I (GA-I) identified by Glutaryl-coenzyme A dehydrogenase deficiency in skin fibroblasts. The onset of neurologic abnormalities was at 6 and 9 months of age as an acute Reye-like presentation in one. Because of the hyperlactacidemia, hyperlactatorrachia, mitochondrial abnormalities in muscular cells and a deficiency in complex I and IV of the respiratory chain in isolated mitochondria from muscle, a presumptive diagnosis of Leigh syndrome was made. We analyze the difference between both disorders. GA-I should be suspected in patients with acute dystonia and psychomotor regression, lactic acidosis and hypodensity of the basal ganglia.
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PMID:[Complex I and IV deficits in the mitochondrial respiratory chain in two siblings with type I glutaric aciduria]. 794 28

A major theory regarding the mechanism of neuronal degeneration in several movement disorders is that mitochondrial defects may play a role. Biochemical studies in Parkinson's disease, Huntington's disease, multiple system atrophy, and idiopathic dystonia have shown defects in enzymes of oxidative phosphorylation in postmortem brain tissue, platelets, muscle, or lymphocytes. The basal ganglia and substantia nigra are also particularly susceptible to the accumulation of age-dependent mitochondrial DNA deletions, which may contribute to the delayed onset of movement disorders. The 1-methyl-4-phenyl 1,2,3,6-tetrahydropyridine model of Parkinson's disease involves conversion to 1-methyl-4-phenylpyridinium, which then inhibits complex I of the electron transport chain. Our studies show that the complex II inhibitor 3-nitropropionic acid can closely replicate the neurochemical, histologic, and clinical features of Huntington's disease. The mechanism of neuronal death in both these models may be slow excitotoxicity. Both direct biochemical studies and animal models of movement disorders therefore suggest that mitochondrial dysfunction may play a direct role in their pathogenesis.
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PMID:Mitochondrial dysfunction in movement disorders. 795 42

A five-generation Hispanic family expressing maternally transmitted Leber hereditary optic neuropathy and/or early-onset dystonia associated with bilateral basal ganglia lesions was studied. Buffy coat mitochondrial DNA (mtDNA) from a severely affected child was amplified by the polymerase chain reaction and greater than 90% sequenced. The mtDNA proved to be a Native American haplogroup D genotype and differed from the standard "Cambridge" sequence at 40 nucleotide positions. One of these variants, a G-to-A transition at nucleotide pair (np) 14459, changed a moderately conserved alanine to a valine at NADH dehydrogenase subunit 6 (ND6) residue 72. The np 14459 variant was not found in any of 38 Native American haplogroup D mtDNAs, nor was it detected in 108 Asian, 103 Caucasian, or 99 African mtDNAs. Six maternal relatives in three generations were tested and were found to harbor the mutation, with one female affected with Leber hereditary optic neuropathy being heteroplasmic. Thus, the np 14459 G-to-A missense mutation is specific to this family, alters a moderately conserved amino acid in a complex I gene, is a unique mtDNA variant in Native American haplogroup D, and is heteroplasmic, suggesting that it is the disease-causing mutation.
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PMID:A mitochondrial DNA mutation at nucleotide pair 14459 of the NADH dehydrogenase subunit 6 gene associated with maternally inherited Leber hereditary optic neuropathy and dystonia. 801 39

A heteroplasmic G-to-A transition at nucleotide pair (np) 14459 within the mitochondrial DNA (mtDNA)-encoded NADH dehydrogenase subunit 6 (ND6) gene has been identified as the cause of Leber hereditary optic neuropathy (LHON) and/or pediatric-onset dystonia in three unrelated families. This ND6 np 14459 mutation changes a moderately conserved alanine to a valine at amino acid position 72 of the ND6 protein. Enzymologic analysis of mitochondrial NADH dehydrogenase (complex I) with submitochondrial particles isolated from Epstein-Barr virus-transformed lymphoblasts revealed a 60% reduction (P < 0.005) of complex I-specific activity in patient cell lines compared with controls, with no differences in enzymatic activity for complexes II plus III, III and IV. This biochemical defect was assigned to the ND6 np 14459 mutation by using transmitochondrial cybrids in which patient Epstein-Barr virus-transformed lymphoblast cell lines were enucleated and the cytoplasts were fused to a mtDNA-deficient (p 0) lymphoblastoid recipient cell line. Cybrids harboring the np 14459 mutation exhibited a 39% reduction (p < 0.02) in complex I-specific activity relative to wild-type cybrid lines but normal activity for the other complexes. Kinetic analysis of the np 14459 mutant complex I revealed that the Vmax of the enzyme was reduced while the Km remained the same as that of wild type. Furthermore, specific activity was inhibited by increasing concentrations of the reduced coenzyme Q analog decylubiquinol. These observations suggest that the np 14459 mutation may alter the coenzyme Q-binding site of complex I.
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PMID:Use of transmitochondrial cybrids to assign a complex I defect to the mitochondrial DNA-encoded NADH dehydrogenase subunit 6 gene mutation at nucleotide pair 14459 that causes Leber hereditary optic neuropathy and dystonia. 862 78

A rare form of Leber hereditary optic neuropathy (LHON) that is associated with hereditary spastic dystonia has been studied in a large Dutch family. Neuropathy and ophthalmological lesions were present together in some family members, whereas only one type of abnormality was found in others. mtDNA mutations previously reported in LHON were not present. Sequence analysis of the protein-coding mitochondrial genes revealed two previously unreported mtDNA mutations. A heteroplasmic A-->G transition at nucleotide position 11696 in the ND4 gene resulted in the substitution of an isoleucine for valine at amino acid position 312. A second mutation, a homoplasmic T-->A transition at nucleotide position 14596 in the ND6 gene, resulted in the substitution of a methionine for the isoleucine at amino acid residue 26. Biochemical analysis of a muscle biopsy revealed a severe complex I deficiency, providing a link between these unique mtDNA mutations and this rare, complex phenotype including Leber optic neuropathy.
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PMID:Genetic and biochemical impairment of mitochondrial complex I activity in a family with Leber hereditary optic neuropathy and hereditary spastic dystonia. 864 32

A significant proportion of patients with inborn errors of the mitochondrial respiratory chain exhibit movement disorders, particularly dystonia. Point mutations of mitochondrial DNA (mtDNA) are usually expressed systemically, and defects of platelet respiratory chain function have been described in patients with mtDNA mutations and Leber's hereditary optic neuropathy (LHON). Recent reports have documented families with dystonia in association with LHON and mtDNA complex I gene mutations. We have examined mitochondrial function in platelet mitochondria from patients with familial generalized dystonia (linked or not linked to 9q34) and sporadic focal dystonia. We confirm a previous report of a specific complex I defect in patients with sporadic focal dystonia but could not find any abnormality in patients with familial generalized dystonia, linked or not to 9q34. These results support the existence of a mitochondrial deficiency in sporadic focal dystonia and provide a biochemical dimension to the clinical and genetic distinction between focal and generalized familial dystonia.
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PMID:Complex I function in familial and sporadic dystonia. 912 15


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