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Aggregation and motor neuron toxicity of an ALS-linked SOD1 mutant independent from wild-type SOD1
L I Bruijn1, M K Houseweart, S Kato
1Ludwig Institute for Cancer Research and Departments of Medicine and Neuroscience, University of California, La Jolla, CA 92093, USA.
Abstract:
Analysis of transgenic mice expressing familial amyotrophic lateral sclerosis (ALS)-linked mutations in the enzyme superoxide dismutase (SOD1) have shown that motor neuron death arises from a mutant-mediated toxic property or properties. In testing the disease mechanism, both elimination and elevation of wild-type SOD1 were found to have no effect on mutant-mediated disease, which demonstrates that the use of SOD mimetics is unlikely to be an effective therapy and raises the question of whether toxicity arises from superoxide-mediated oxidative stress. Aggregates containing SOD1 were common to disease caused by different mutants, implying that coaggregation of an unidentified essential component or components or aberrant catalysis by misfolded mutants underlies a portion of mutant-mediated toxicity.
Insights
Familial amyotrophic lateral sclerosis (ALS) involves motor neuron death from toxic superoxide dismutase 1 (SOD1) mutations. Therapies targeting SOD1 may be ineffective, as toxicity might stem from protein aggregation rather than oxidative stress.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- Familial amyotrophic lateral sclerosis (ALS) is linked to mutations in the superoxide dismutase 1 (SOD1) gene.
- Motor neuron degeneration in ALS is believed to result from toxic properties of mutant SOD1.
Purpose of the Study:
- To investigate the disease mechanism underlying mutant SOD1-mediated toxicity in ALS.
- To determine if SOD1 levels or oxidative stress are primary drivers of motor neuron death.
Main Methods:
- Analysis of transgenic mouse models expressing familial ALS-linked SOD1 mutations.
- Experimentation involving the elimination and elevation of wild-type SOD1 levels.
- Examination of SOD1 aggregate formation in diseased motor neurons.
Main Results:
- Neither eliminating nor increasing wild-type SOD1 affected mutant-mediated disease progression.
- SOD1 aggregates were consistently found in motor neurons affected by various SOD1 mutants.
- The findings suggest that SOD1 mimetics are unlikely to be effective ALS therapies.
Conclusions:
- Mutant SOD1 toxicity in ALS may not primarily arise from superoxide-mediated oxidative stress.
- Protein misfolding, aberrant catalysis, or coaggregation with other cellular components likely contribute to motor neuron death.
- Further research should focus on the aggregation pathways and interactions of misfolded SOD1.