Can Molecular Partners Reshape Amyloid Assembly?A Reductionist Investigation of the Influence of a TRA2B-Derived Peptide on tau(297-391) Amyloid Fibrils

Abstract

Tau protein aggregation into amyloid fibrils is a major feature of Alzheimer’s disease. This process can be influenced by the molecular environment of Tau, including interactions with other proteins. Previous work from SwitchLab using a cell-based screening assay identified TRA2B as a potential modulator of Tau aggregation and showed that P12, a TRA2B-derived peptide, can influence this process. This study aimed to characterize the effects of P12 on the assembly of the tau(297–391) fragment using a reductionist in vitro system combining kinetic, biochemical, and microscopic analyses. P12 modified the aggregation profiles of tau(297–391)-containing reactions under different experimental conditions, while preformed P12 assemblies also promoted thioflavin T-positive responses in the presence of tau(297–391). Both tau(297–391) and P12 were simultaneously depleted from the soluble fraction, consistent with their partitioning into sedimentable material. Following optimization of the aggregation conditions, tau(297–391) fibrils displaying a twisted morphology resembling that of Tau filaments observed in Alzheimer’s disease were obtained. Co-incubation with P12 was associated with a different distribution of fibrillar morphologies compared with the individual controls, while nanogold labeling provided preliminary indications of P12 association with fibrillar material. Taken together, these results indicate that P12 can modulate the aggregation behavior and fibrillar morphology of tau(297–391). However, they do not establish whether P12 is incorporated into the same fibrils as tau(297–391) or directly alters the underlying tau(297–391) fold.