Local Organization of Biological Membranes Modulates Tau-Lipid Interactions and Fibril formation.

The formation of Tau amyloids is a hallmark of several neurodegenerative diseases, called Tauopathies, including Alzheimer's disease. In different Tauopathies, Tau amyloid filaments adopt a distinct structure, highlighting the existence of disease specific pathways. In this pathological context, lipid metabolism is heavily disrupted, leading to a perturbation of membrane composition. Lipid membranes have been shown to nucleate tau aggregation under some conditions. However, no general model has been established to explain how the organization of the lipid membrane modulates Tau aggregation. Here, we combined biochemistry and biophysical tools, including EPR spectroscopy, to investigate the mechanisms of membrane-induced Tau aggregation. After showing the importance of the electrostatic interaction between Tau and anionic lipids, we investigate how the amount and density of charges influence Tau aggregation. This work allows us to draw a general model where membrane-induced Tau aggregation is a two-step process. First, the binding to the membrane through electrostatic interactions is a necessary but not a sufficient step. Second, the nucleation of Tau amyloids at the membrane surface occurs only when specific conditions are fulfilled, i.e., high surface density altering Tau conformation and spatial proximity between aggregation-prone conformers. A direct implication of this model is that local membrane heterogeneities, such as phase separation or lipid rafting, are strong modulators of Tau aggregation. This work provides the molecular basis to predict how different membrane states regulate Tau aggregation.