서울대학교 식품생화학 연구실SNU food biochemistry laboratory

Although Cu/Zn superoxide dismutase (SOD1) primarily detoxifies cells by scavenging _{superoxide radical (O2^•-)}, it also contributes to amyotrophic lateral sclerosis (ALS) by generating unusual amyloid filaments. We found that mutant SOD1 variants construct these filaments faster and have smaller cores than those of their wild-type (WT) counterparts. Moreover, in the presence of preformed filaments, the WT SOD1 filament structure was more dominant in shaping the overall filament morphology than the mutant forms. These observations highlight the relationship between filament architecture and assembly speed, with implications for ALS progression and insights into potential therapeutic strategies.

The formation of superoxide dismutase 1 (SOD1) filaments has been implicated in amyotrophic lateral sclerosis (ALS). Although the disulfide bond formed between Cys57 and Cys146 in the active state has been well studied, the role of the reduced cysteine residues, Cys6 and Cys111, in SOD1 filament formation remains unclear. In this study, we investigated the role of reduced cysteine residues by determining and comparing cryoelectron microscopy (cryo-EM) structures of wild-type (WT) and C6A/C111A SOD1 filaments under thiol-based reducing and metal-depriving conditions, starting with protein samples possessing enzymatic activity. The C6A/C111A mutant SOD1 formed filaments more rapidly than the WT protein. The mutant structure had a unique paired-protofilament arrangement, with a smaller filament core than that of the single-protofilament structure observed in WT SOD1. Although the single-protofilament form developed more slowly, cross-seeding experiments demonstrated the predominance of single-protofilament morphology over paired protofilaments, regardless of the presence of the Cys6 and Cys111 mutations. These findings highlight the importance of the number of amino acid residues within the filament core in determining the energy requirements for assembly. Our study provides insights into ALS pathogenesis by elucidating the initiation and propagation of filament formation, which potentially leads to deleterious amyloid filaments.