Acetylated α-tubulin K394 regulates microtubule stability to shape the growth of axon terminals

Microtubules are essential to neuron shape and function. Acetylation of tubulin has the potential to directly tune the behavior and function of microtubules in cells. Although proteomic studies have identified several acetylation sites in α-tubulin, the effects of acetylation at these sites remains largely unknown. This includes the highly conserved residue lysine 394 (K394), which is located at the αβ-tubulin dimer interface. Using a fly model, we show that α-tubulin K394 is acetylated in the nervous system and is an essential residue. We found that an acetylation-blocking mutation in endogenous α-tubulin, K394R, perturbs the synaptic morphogenesis of motoneurons and reduces microtubule stability. Intriguingly, the K394R mutation has opposite effects on the growth of two functionally and morphologically distinct motoneurons, revealing neuron-type-specific responses when microtubule stability is altered. Eliminating the deacetylase HDAC6 increases K394 acetylation, and the over-expression of HDAC6 reduces microtubule stability similar to the K394R mutant. Thus, our findings implicate α-tubulin K394 and its acetylation in the regulation of microtubule stability and suggest that HDAC6 regulates K394 acetylation during synaptic morphogenesis. •α-tubulin K394 is acetylated in the nervous system and is critical to neuronal growth•An acetylation-blocking K39R mutation decreases microtubule stability•The K394R mutation has neuron-type-specific effects on growth•Loss of HDAC6 increases K394 acetylation, indicating that HDAC6 deacetylates K394 Neuronal microtubules are enriched in post-translational modifications, including acetylation. Saunders et al. reveal that a conserved α-tubulin lysine, K394, is acetylated in the fly nervous system, where it regulates neuronal morphogenesis by affecting microtubule stability. Loss- and gain-of-function studies indicate HDAC6 deacetylates K394.