Methylation at a conserved lysine residue modulates tau assembly and cellular functions

The neuronal microtubule-associated protein tau undergoes multiple post-translational modifications, which dynamically modulate its molecular functions and biochemical features in space and time. Among them, we have recently reported that a conserved lysine residue mapping to the microtubule-binding domain of the protein (K306 in mouse and K317 in human) is differentially methylated in a model of chronic autoimmune demyelination. In contrast with other well-studied tau post-translational modifications such as phosphorylation, lysine methylation is far less investigated and its specific impact on tau biology is not fully understood. Here we performed a comprehensive analysis of the effects of K317 methylation on key tau features. By combining in silico simulations with in vitro biochemical assays and live-cell imaging, we show that methylated tau is more prone to self-assembly into insoluble structures. Moreover, we demonstrate that K317 methylation affects the stabilization activity of tau on microtubule dynamics. Lastly, we highlight a role for K317 methylation in regulating both neuronal differentiation and cell proliferation. Altogether, these findings shed light on the biology of an overlooked tau post-translational modification as well as on the fine tuning of tau functionality in health and disease.