Stabilization of dynamic microtubules by mDia1 drives Tau-dependent Aβ1-42 synaptotoxicity

Oligomeric Amyloid beta(1-42) (A beta) plays a crucial synaptotoxic role in Alzheimer's disease, and hyperphosphorylated tau facilitates A beta toxicity. The link between A beta and tau, however, remains controversial. In this study, we find that in hippocampal neurons, A beta acutely induces tubulin posttranslational modifications (PTMs) and stabilizes dynamic microtubules (MTs) by reducing their catastrophe frequency. Silencing or acute inhibition of the formin mDia1 suppresses these activities and corrects the synaptotoxicity and deficits of axonal transport induced by A beta. We explored the mechanism of rescue and found that stabilization of dynamic MTs promotes tau-dependent loss of dendritic spines and tau hyperphosphorylation. Collectively, these results uncover a novel role for mDia1 in A beta-mediated synaptotoxicity and demonstrate that inhibition of MT dynamics and accumulation of PTMs are driving factors for the induction of tau-mediated neuronal damage.