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bioRxiv · 10.64898/2026.05.29.728874

α-Synuclein and γ-Tubulin Cooperatively Regulate Activity-Evoked Presynaptic Microtubule Nucleation to Gate Dopamine Release

Comincini, A.·Choi, S. J.·Mosharov, E.·Milanetti, E.·Kanter, E.·Ruocco, G.·Cappelletti, G.·Sulzer, D. L.·Bartolini, F.
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Abstract

-Synuclein has long been implicated in the regulation of synaptic activity, but the molecular basis that underlies this function has been elusive. Here, we identify a microtubule (MT)-dependent mechanism through which -synuclein regulates synaptic dopamine release. Using live imaging of cultured dopaminergic neurons, we visualize dynamic MTs at individual presynaptic boutons and show that neuronal activity triggers local {gamma}-tubulin-dependent MT nucleation. We find that this nucleation is essential for interbouton synaptic vesicle (SV) transport and for sustained dopamine release during high activity. We further discover that -synuclein acts as a positive regulator of presynaptic MT nucleation by binding directly to {gamma}-tubulin and the /{beta}-tubulin heterodimer. Activity-evoked phosphorylation of -synuclein at serine 129, a modification that accumulates in synucleinopathies and a molecular switch for -synuclein binding to synaptic proteins, occurs in the region of /m tubulin binding and is both necessary and sufficient for MT initiation. Our findings reveal a previously unrecognized, activity-dependent role for -synuclein in the nucleation of axonal MTs that enables on-demand SV interbouton redistribution and dopamine release. This mechanism provides a novel molecular link between -synuclein phosphorylation and MT-dependent modulation of dopamine release, offering insight into how its dysregulation may contribute to dopaminergic synaptic dysfunction, a central feature of synucleinopathies.

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Comincini, A., Choi, S. J., Mosharov, E., Milanetti, E., Kanter, E., Ruocco, G., Cappelletti, G., Sulzer, D. L., Bartolini, F.. 2026-06-04. α-Synuclein and γ-Tubulin Cooperatively Regulate Activity-Evoked Presynaptic Microtubule Nucleation to Gate Dopamine Release. https://doi.org/10.64898/2026.05.29.728874

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