High Resolution Structural Analysis Of ALS‐Associated Mutant SOD1 Inclusion Bodies

Abstract

Inclusion bodies (IBs) – insoluble structures that can form upon overexpression of proteins‐ have wide relevance in research, industrial settings, and disease. In addition to their use in protein purification, IBs provide a tractable model to elucidate the molecular mechanisms of protein aggregation in cells, as also occurs in neurodegenerative disorders such as amyotrophic lateral sclerosis (ALS), Parkinson's, and Alzheimer's diseases. The aggregation of Cu, Zn superoxide dismutase (SOD1) variants is associated with ALS, yet the relationships between mutant characteristics and disease properties remain obscure. Here, we report a systematic investigation of SOD1 IBs using two powerful complementary methods to analyze the structures of these cellular aggregates and their changes upon mutation. Quenched amide hydrogen‐deuterium exchange (HDX) measurements by NMR for individual residues throughout SOD1 reveal IB structural features and similarities, whereas quantitative conformation specific antibody binding assays highlight notable differences in surface features between mutant IBs. Taken together, these data provide a valuable new high‐resolution view of cellular aggregation. These powerful HDX and quantitative antibody binding methods are widely applicable to other proteins to define the molecular determinants of their aggregation and solubility.