Biswas, S.; Grover, R.; Reuther, C.; Poojari, C.; Shaebani, M. R.; Grünewald, M.; Zablotsky, A.; Hub, J. S.; Diez, S.; John, K.; Schaedel, L.

Microtubules are cytoskeletal filaments that exhibit dynamic tip instability and, as recent discoveries reveal, possess a dynamic lattice undergoing continuous tubulin loss and incorporation. In this study, we investigate the role of tau, a neuronal microtubule-associated protein (MAP) known for its stabilizing effects on microtubules, in modulating lattice dynamics. Using in vitro reconstitution, kinetic Monte Carlo modeling, and molecular dynamics simulations, we reveal that tau, despite lacking enzymatic activity, accelerates tubulin exchange within the lattice, particularly at topological defect sites. Tau appears to stabilize longitudinal tubulin-tubulin interactions while destabilizing lateral ones, thereby enhancing the mobility and repair of lattice defects. These results challenge the traditional view of tau as merely a stabilizer, uncovering its active role in dynamically modulating microtubule lattice structure.