Tau amyloidogenesis begins with a loss of its conformational polymorphism

Abstract

Knowledge on the molecular bases of early amyloid assembly is fundamental to understand its structure-dysfunction relationship during disease progression.Tauopathies, a well-defined set of neurodegenerative disorders that includes Alzheimer's disease, are characterized by the pathological amyloid aggregation of tau.However, the underlying molecular mechanisms that trigger tau aggregation and toxicity are poorly understood. Here, using a single-molecule approach, AFM-based single molecule-force spectroscopy (AFM-SMFS), combined with a proteinengineering mechanical protection strategy, we have analyzed the fluctuations of the conformational space of tau during the start of its pathological amyloid assembly.Specifically, we have analyzed the region that includes the four tau microtubule-binding repeats, known to play a key role on tau aggregation. We find that, unlike other amyloid-forming proteins, tau aggregation is accompanied by a decrease of conformational polymorphism, which is driven by amyloid-promoting factors, such as the ∆ 280K and P301L mutations, linked to Frontotemporal Dementia-17, or by specific chemical conditions. Such perturbations have distinct effects and lead to different tau (aggregate) structures. In addition to providing insight into how tau aggregates in a context dependent manner, these findings may help delve into how protein aggregationbased diseases, like Alzheimer´s, might be treated using monomer fluctuations as a pharmacological target.