Mutating different α-tubulin acetylation sites has distinct effects on axon terminal morphogenesis in Drosophila melanogaster

Microtubules are created from uniform α- and β-tubulin building blocks but typically carry out a variety of specialized functions within a cell. The post-translational modification of tubulin is one means by which microtubule function can be tuned to match different cellular activities. While multiple sites of acetylation have been identified in tubulin, particularly α-tubulin, the effect of acetylation at different sites on microtubule function remains poorly characterized. Here, we took a genetic approach in Drosophila to disrupt three conserved sites of acetylation (K326, K370, K401) in endogenous α-tubulin and characterized the effects on neuronal development. Acetylation-blocking mutagenesis of α-tubulin K326 (K326A) perturbed larval locomotion and reduced axon terminal growth at the neuromuscular junction. These deficits were accompanied by a reduction in stable microtubules, suggesting that the α-tubulin K326A mutation exerts its effect by disrupting microtubule stability. In contrast, mutagenesis of α-tubulin K370 and K401 had virtually no effect on microtubule stability, suggesting that the effects of these mutations on axon terminal morphogenesis and survival may be mediated through a different mechanism. Altogether, the varied effects of these mutations suggests that acetylation at these three different sites may regulate different aspects of microtubule function within developing neurons.