There are synergistic effects of Aβ and tau protein in Alzheimer's disease. Aβ1-42 protofibril seeds induce conversion of human tau protein into β-sheet-rich toxic tau oligomers. However, the molecular mechanisms underlying such a conformational conversion are unclear. Here, we use extensive all atom replica exchange molecular dynamics simulations to investigate the effects of preformed Aβ1-42 protofibril on two monomeric tau constructs: K18 and K19. We found that Aβ oligomer stretches tau conformation and drastically reduces the metastable secondary structures/hydrogen bonding/salt-bridge networks in tau monomers and exposes their fibril nucleating motifs 275VQIINK280 and 306VQIVYK311. Aβ interacting patches around Tyr10/Ile41 contribute significantly to the interactions with K18 and K19. Aβ cross-seeded tau aggregation can adopt a "stretching-and-packing" mechanism, paving the way for the next, prion-like growth step. The results provide a mechanism on the atomic level to experimental observations that tau pathogenesis is promoted by Aβ1-42 but not by Aβ1-40.
- Alzheimer's disease
- tau K18/K19