SOD1 D90A

Superoxide dismutase 1 (SOD1) is an essential antioxidant enzyme that converts harmful superoxide radicals into less toxic molecules, protecting motor neurons and other cells from oxidative damage. Mutations in SOD1 represent the second most common genetic cause of ALS in European populations [1], with the A4V variant being particularly prevalent and aggressive in North American familial ALS cases. The pathogenic classification of A4V by multiple expert panels, combined with its complete absence from population databases, confirms this variant's disease-causing role rather than representing benign variation. The structural prediction of SOD1 A4V achieved an exceptionally high average confidence score of 97.8% (pLDDT), indicating that AlphaFold2 generated a highly reliable model of the protein's three-dimensional architecture. This high confidence across the structure allows for detailed analysis of how the A4V substitution—replacing a small alanine with a larger valine at position 4—might destabilize the protein and promote the misfolding and aggregation that characterizes SOD1-ALS pathology. Such misfolded SOD1 proteins can propagate between cells in a prion-like manner, with experimental studies demonstrating that injection of misfolded SOD1 aggregates can accelerate disease onset in animal models [6]. The clinical significance of identifying SOD1 mutations has increased dramatically with the development of targeted therapies. Tofersen, an antisense oligonucleotide that reduces SOD1 protein production, has been authorized for treating SOD1-ALS and shows promising results in real-world clinical use [2][3][8]. Patients treated with tofersen have shown stabilization or even improvement in motor function, with some Icelandic patients experiencing nonprogressive disease for over two years [8]. These therapeutic advances underscore the importance of prompt genetic screening for SOD1 mutations in ALS patients, as early intervention may offer the best opportunity for disease modification. Beyond motor neuron degeneration, SOD1 mutations appear to affect multiple biological systems. Recent research indicates that SOD1 dysfunction disrupts lipid metabolism and hypothalamic function, potentially explaining metabolic alterations observed in ALS patients [4]. Additionally, SOD1 influences extracellular vesicle dynamics, which may contribute to disease propagation between cells [7]. While gastrointestinal symptoms are common in ALS, studies suggest these may not be directly caused by SOD1 expression in gut tissue itself [5], highlighting the primarily neurological nature of SOD1-mediated disease despite systemic metabolic effects.