Mechanistic insights into remodeled Tau-derived PHF6 peptide fibrils by Naphthoquinone-Tryptophan hybrids

Intra-cellular tau protein tangles and extra-cellular β-amyloid plaques are hallmarks of Alzheimer's disease (AD), characterized by the conversion of natively unfolded monomeric protein/peptide into misfolded β-sheet rich aggregates. Therefore, inhibiting the aggregation cascade or disassembling the pre-formed aggregates becomes a pivotal event in disease treatment. In the present study, we show that Naphthoquinone-Tryptophan hybrids, i.e., NQTrp and Cl-NQTrp significantly disrupted the pre-formed fibrillar aggregates of Tau-derived PHF6 (VQIVYK) peptide and full-length tau protein in vitro, in a dose-dependent manner as evident from ThS assay, CD spectroscopy, and TEM. Molecular dynamics simulation of PHF6 oligomers and fibrils with the Naphthoquinone-Tryptophan hybrids provides a possible structure-function based mechanism-of-action, highlighting the role of hydrophobic interaction and hydrogen bond formation during fibril disassembly. These findings signify the effectiveness of NQTrp and Cl-NQTrp in disassembling fibrillar aggregates and may help in designing novel hybrid molecules for AD treatment.