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CuZn-superoxide dismutase in D90A heterozygotes from recessive and dominant ALS pedigrees.
Umeå University, Faculty of Medicine, Medical Biosciences, Clinical chemistry.
Umeå University, Faculty of Medicine, Medical Biosciences, Clinical chemistry.
Umeå University, Faculty of Medicine, Pharmacology and Clinical Neuroscience.
Umeå University, Faculty of Medicine, Pharmacology and Clinical Neuroscience.
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2002 (English)In: Neurobiology of Disease, ISSN 0969-9961, Vol. 10, no 3, 327-333 p.Article in journal (Refereed) Published
Abstract [en]

Mutations in CuZn-superoxide dismutase (CuZn-SOD) have been linked to ALS. In most cases ALS is inherited as a dominant trait and there is marked reduction in CuZn-SOD activity in samples from the patients. The D90A mutation, however, mostly causes ALS as a recessive trait and shows near normal CuZn-SOD activity. A few familial and sporadic ALS cases heterozygous for the D90A mutation have also been found. Haplotype analysis of both types of D90A families has suggested that all recessive cases share a common founder and may carry a protective factor located close to the D90A mutant CuZn-SOD locus. To search for effects of a putative protective factor we analysed erythrocytes from D90A heterozygous individuals for SOD activity by a direct assay, subunit composition by immunoblotting, and zymogram pattern formed by isoelectric focusing and SOD staining. Included were heterozygotes from 17 recessive families, and from 2 dominant families and 4 apparently sporadic cases. The CuZn-SOD activity in the recessive and dominant groups was found to be equal, and 95% of controls. The ratio between mutant and wildtype subunits was likewise equal and 0.8:1 in both groups. The zymograms revealed multiple bands representing homo- and heterodimers. There were, however, no differences between the groups in patterns or in ratios between the molecular forms. In conclusion we find no evidence from analyses in erythrocytes that the putative protective factor in recessive families acts by simply downregulating the synthesis or altering the molecular structure or turnover of the mutant enzyme.

Place, publisher, year, edition, pages
2002. Vol. 10, no 3, 327-333 p.
URN: urn:nbn:se:umu:diva-27728DOI: 10.1006/nbdi.2002.0508PubMedID: 12270693OAI: diva2:277426
Available from: 2009-11-18 Created: 2009-11-18 Last updated: 2009-11-18
In thesis
1. Superoxide dismutase 1 and amyotrophic lateral sclerosis
Open this publication in new window or tab >>Superoxide dismutase 1 and amyotrophic lateral sclerosis
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Superoxid dismutas 1 och amyotrofisk lateralskleros
Abstract [en]

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons in the spinal cord, brain stem and motor cortex, leading to paralysis, respiratory failure and death. In about 5% of ALS cases, the disease is associated with mutations in the CuZn-superoxide dismutase (hSOD1) gene. As a rule, ALS caused by hSOD1 mutations is inherited dominantly and the mutant hSOD1s cause ALS by the gain of a noxious property.

The present study focused on two hSOD1 mutations with widely differing characters. In Scandinavia, ALS caused by the D90A mutation is inherited in a recessive pattern. Elsewhere, families with dominant inheritance have been found. The properties of D90A mutant hSOD1 are very similar to those of the wild-type protein. The G127insTGGG (G127X) mutation causes a 21 amino acid C-terminal truncation which probably results in an unstable protein.

The aim of this thesis was to generate transgenic mice expressing D90A and G127X mutant hSOD1s and to compare these mice with each other and with mice expressing other mutant hSOD1s, in search of a common noxious property. The findings were also compared with the results from studies of human CNS tissue.

The cause of the different inheritance patterns associated with D90A mutant hSOD1 was investigated by analyzing erythrocytes from heterozygous individuals from dominant and recessive pedigrees. There was no evidence that a putative protective factor in recessive pedigrees acts by down-regulating the synthesis of D90A mutant hSOD1.

In cerebrospinal fluid, there was no difference in hSOD1 content between homozygous D90A patients, ALS patients without hSOD1 mutations and controls. hSOD1 cleaved at the N-terminal end was found in both controls and D90A patients, but the proportion was significantly larger in the latter group. This indicates a difference in degradation routes between mutant and wild-type hSOD1.

Both D90A and G127X transgenic mice develop an ALS-like phenotype. Similar to humans, the levels of D90A protein were high. The levels of G127X hSOD1 were very low in the tissues but enriched in the CNS. Similarly, in an ALS patient heterozygous for G127X hSOD1, the levels of the mutant protein were overall very low, but highest in affected CNS areas. Despite the very different levels of mutant hSOD1, both D90A and G127X transgenic mice developed similar levels of detergent-resistant aggregates in the spinal cord when terminally ill. Surprisingly, mice overexpressing wild-type hSOD1 also developed detergent-resistant aggregates, although less and later. Most of the hSOD1 in the CNS of transgenic mice was inactive due to deficient copper charging or because of reduced affinity for the metal. The stabilizing intrasubunit disulfide bond of hSOD1 was partially or completely absent in the different hSOD1s. Both these alterations could increase the propensity of mutant hSOD1s to misfold and form aggregates.

The results presented here suggest that the motor neuron degeneration caused by mutant hSOD1s may be attributable to long-term exposure to misfolded, aggregation-prone, disulfide-reduced hSOD1s and that the capacity to degrade such hSOD1s is lower in susceptible CNS areas compared with other tissues. The data also suggest that wild-type hSOD1 has the potential to participate in the pathogenesis of sporadic ALS.

Place, publisher, year, edition, pages
Umeå: Medicinsk biovetenskap, 2005. 119 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 981
Neurosciences, aggregates, ALS, amyotrophic lateral sclerosis, cerebrospinal fluid, disulfide-reduced, inclusions, misfolded, protective factor, SOD1, transgenic, Neurovetenskap
National Category
Research subject
Clinical Chemistry
urn:nbn:se:umu:diva-611 (URN)91-7305-936-6 (ISBN)
Public defence
2005-11-04, Sal B, 9 tr, 1D, Tandläkarhögskolan, 90185 NUS, Umeå, 13:00 (English)
Available from: 2005-10-13 Created: 2005-10-13 Last updated: 2009-11-18Bibliographically approved

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