Mechanism of the N87D mutation in SOD1-atypical amyotrophic lateral sclerosis case report and literature review molecular mechanism of N87D mutation in SOD1.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with unclear pathogenesis. This study aimed to investigate the possible molecular mechanisms of ALS by analyzing protein structure and dynamics in a rapidly progressing ALS patient carrying the N87D mutation. A patient with the N87D mutation experienced rapid disease progression and died within one year. We reviewed all known mutations at the 87th position of the superoxide dismutase (SOD1) gene and the clinical characteristics. To investigate the molecular basis of the severe phenotype, we performed protein structure modeling and molecular dynamics (MD) simulations, and compared wild type homodimers, mutant homodimers, and heterodimers in terms of energy, residue fluctuation, number of hydrogen bonds, radius of gyration (Rg), principal component analysis (PCA), free energy landscape (FEL), the contribution of dimer interface residues, solvent-accessible surface area, and metal ion coordination. Our analysis revealed that patients with mutations at the 87th position of the SOD1 gene typically exhibited rapid disease progression. Protein structure modeling and MD simulations demonstrated that the N87D mutation significantly increased the energy and RMSF of SOD1 heterodimers compared to homodimers. Furthermore, Rg, FEL and PCA analyses showed that the heterodimers had a broader and more unstable conformational energy distribution, along with a stronger tendency for aggregation. Additionally, the N87D mutation disrupted metal ion coordination, further destabilizing the heterodimer and promoting protein misfolding. These findings suggest a potential molecular mechanism underlying ALS and support a protein structure based approach for investigating the pathogenic mechanisms of disease causing mutations.