Mutant superoxide dismutase-1 indistinguishable from wild-type causes ALS

Area of Science:

• Neuroscience
• Genetics
• Biochemistry

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease.
• Mutations in the superoxide dismutase-1 (SOD1) gene are linked to familial ALS.
• Identifying novel SOD1 mutations can elucidate ALS pathogenesis.

Purpose of the Study:

• To investigate a novel SOD1 mutation (c.352C>G, L117V) found in Syrian ALS families.
• To analyze the functional and structural properties of the L117V SOD1 mutant.
• To assess the role of SOD1 stability and misfolding in ALS pathogenesis.

Main Methods:

• Genetic analysis of ALS patients.
• Enzyme activity assays in erythrocytes.
• Protein stability assays under denaturing conditions.
• ELISA to detect misfolded SOD1 species in fibroblast extracts.

Main Results:

• A novel L117V SOD1 mutation was identified in two Syrian ALS families with low disease penetrance and slow progression.
• L117V mutant SOD1 exhibited normal enzymatic activity and structural stability comparable to wild-type SOD1.
• Misfolded SOD1 levels were not elevated in L117V patients, unlike in patients with other known SOD1 mutations.
• Wild-type human SOD1 stability falls within the range of ALS-associated SOD1 variants.

Conclusions:

• SOD1 mutations leading to fully stable proteins are associated with low ALS penetrance.
• The L117V mutation suggests that stable SOD1 variants may contribute to sporadic ALS.
• These findings support a potential role for wild-type SOD1 in general ALS pathogenesis.