Molecular Basis of Synergistic Tau Amyloid Core Inhibition by K311/K353 Acetylation via Microsecond MD Simulations

Neurofibrillary tangles, composed of aggregated Tau proteins, are a pathological hallmark of Alzheimer's disease (AD). Within these tangles, the amyloid core is primarily formed by the microtubule-binding (MTB) repeats. Although site-specific acetylation has been implicated in the regulation of Tau aggregation, the atomic-level mechanisms by which individual acetylation events modulate the structure and interactions of amyloid-forming motifs remain incompletely understood. In particular, whether dual acetylation events may act cooperatively during early Tau assembly is still unclear. In this study, we used microsecond-scale all-atom molecular dynamics simulations to systematically examine the dimerization dynamics of the four Tau MTB repeat homodimers (R1-R4). Our simulations suggest that the relatively higher aggregation propensity of R3 and R4 may be associated with amyloidogenic, β-sheet-prone core sequences, in which the key lysine residues K311 and K353 are located. Further analysis indicates that acetylation at these sites attenuates early Tau dimerization: K353 acetylation appears to moderately destabilize the R4 dimer through steric effects and the disruption of intrachain salt bridges, resulting in a more disordered conformational ensemble. K311 acetylation shows a more pronounced inhibitory effect on R3 dimerization by neutralizing the positive charge of K311 and weakening key interchain salt bridges and π-cation interactions associated with the PHF6 motif. Notably, dual acetylation of K311 and K353 in the R3-R4 dimer produces a stronger-than-additive reduction in β-sheet formation. This potential synergistic effect arises from the combined disruption of the hydrophobic core and distal electrostatic interaction networks. In summary, our results provide a molecular-level explanation for how acetylation at K311 and K353 cooperatively modulates Tau dimerization and early amyloid nucleation, offering mechanistic insight into the role of lysine acetylation in Tau aggregation.