Effect of Acetylation on Liquid‐Liquid Phase Separation and Amyloid Fibril Formation of Tau

Abstract

The function of proteins depends on their phase behavior. When the concentration of a protein exceeds a critical value, it may undergo liquid‐liquid phase separation, leading to demixing of proteins from solution. The resulted liquid droplets are dense and protein‐rich. The microtubule associated protein tau can enrich tubulin by forming liquid droplets, which promotes the formation of microtubule bundles. On the other hand, aberrant aggregation of Tau into neurofibrillary tangles correlates with the progressive destruction of nerve cells. Therefore, studying the aggregating mechanism of tau and drug design targeting tau fibrils are critical for the therapy of Alzheimer's disease. Recent studies have shown that lysine acetylation plays an important role in modulating tau aggregation and microtubule assembly. Considering the potential correlations between liquid‐liquid phase separation and amyloid formation, here we investigated the effect of lysine acetylation on the phase behavior and function of tau in vitro. We used site‐directed mutagenesis, light scattering, thioflavin T florescence assay, and microrheology to study the liquid‐liquid phase separation and aggregation of tau. Consistent with previous observations, acetylation on K274/K321 (mimicked by K274Q/K321Q) significantly impaired tau aggregation whereas acetylation on K280/K281/K369 (mimicked by K280Q/K281Q/K369Q) significantly promoted tau filament formation as compared with the WT protein. Although acetylation on K274/K321 and K280/K281/K369 differentially affected tau aggregation, both acetylation patterns promoted liquid‐liquid phase separation of tau. Moreover, microrheology characterization and protein concentration determination showed that the droplets formed by acetylated tau were denser than the WT protein, suggesting that more intermolecular interactions were form upon lysine acetylation. These results show that lysine residues within the MT‐binding repeats regulate the phase behavior of tau via complex interactions.Support or Funding InformationThis work was supported by National Natural Science Foundation of China (Grant number: 21603121) and Hubei University of Technology.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.