Real-time analysis and direct observations of different superoxide dismutase (SOD1) molecules bindings to aggregates in temporal evolution step

The misfolding and intracellular aggregation of Cu–Zn superoxide dismutase (SOD1) is pathologically key feature of amyotrophic lateral sclerosis (ALS). Although details of the mechanisms continue to be unclear, there are key steps in the possible pathway to the development of ALS. This study focuses on interactions between different SOD1 molecules (A4V apo/holo, and WT apo/holo) and homogeneous aggregates in the temporal evolution step, and a determination of whether any of the SOD1 molecules are reactive to the aggregates with the extent of binding, as determined by surface plasmon resonance (SPR) measurements. Using a kinetic binding model, the association constant of A4V apo was found to be three times larger than that for the WT apo species. Differences in the extent of the interactions were also simultaneously measured and visualized by means of SPR imaging techniques. The SPR-based approach suggests direct correlation between SPR signal and the extent of molecular binding, which can identify the significant contributors to the formation of macroaggregates of SOD1 in the temporal evolution step.

A quantitative and qualitative method for identifying the nature of the aggregation-active superoxide dismutase (SOD1) species in the temporal evolution step by surface plasmon resonance (SPR) measurements is described. Real-time SPR analysis and SPR imaging confirm the presence of an aggregation-prone reactive species of SOD1; mutated and demetalated species significantly contribute to the formation of macroaggregates in the structural evolution of SOD1.Figure optionsDownload as PowerPoint slideHighlights
► Key steps in the temporal evolution of SOD1 to the ALS development are proposed.
► Interactions between various types of SOD1 and aggregates are investigated.
► Types of the SOD1 molecules which are reactive to the aggregates are reported.
► The major factors for the formation of macroaggregates are revealed.