SOD1 and amyotrophic lateral sclerosis: As a result of being the first protein found to harbor ALS-associated mutations (Rosen et al., 1993), SOD1, in its purified form, has been extensively studied from the perspectives of protein folding, aggregation, and prion-like propagation (McAlary et al., 2019b; Wright et al., 2019; Trist et al., 2020).