IN VITRO ASSEMBLY OF TAU AGGREGATES AND THEIR INHIBITION BY SMALL MOLECULES

One of the main hallmarks of Alzheimer's Disease (AD) is the hyperphosphorylation of tau, which in turn leads to the formation of neurofibrillary tangles (NFTs) via aggregation of the protein. Another contribution towards AD progression is the failure of metal homeostasis, affecting multiple pathways that lead to neuron degradation. NFTs from post-mortem AD patients have shown the presence of metals, namely Fe²⁺, Cu²⁺, and Zn²⁺¸ suggesting they may influence the formation of the aggregates. Although in vitro studies of tau aggregation have been performed before, with AFM and TEM being used extensively to obtain images of these aggregates, there are very few studies that extensively observe how the presence of metals affect the morphology of the fibers. Here we studied the aggregation of AD-prevalent metals, monitoring the aggregation using ThT fluorescence as well as verifying and identifying any morphology changes using AFM and TEM imaging. Among the metals we used in this study, only a few metals, Zn²⁺ and Cu², have an impact on the morphology of the fibers. With Zn²⁺ exhibiting feature resembling paired helical filaments (PHFs), one of the major morphologies prevalent in AD patients, we decided to further elucidate the structure using cryo-EM. In addition to forming in vitro assembles, we tested the efficacy of urea and thiourea small molecules against tau aggregation, with varying success.