Tubulin acetylation protects long-lived microtubules against mechanical ageing

Long-lived microtubules endow the eukaryotic cell with long-range transport abilities. While long-lived microtubules are acetylated on Lys40 of alpha-tubulin (aK40), acetylation takes place after stabilizationl and does not protect against depolyrrierization(2). Instead, 01(40 acetylation has been proposed to mechanically stabilize microtubules(3). Yet how modification of alpha K40, a residue exposed to the microtubule lumen and inaccessible to microtubule-associated proteins and motors(1,4), could affect microtubule mechanics remains an open question. Here we develop FRET-based assays that report on the lateral interactions between protofilarnents and find that alpha K40 acetylation directly weakens inter-protofilament interactions. Congruently, alpha K40 acetylation affects two processes largely governed by inter-protofilament interactions, reducing the nucleation frequency and accelerating the shrinkage rate. Most relevant to the biological function of acetylation, rnicrofluidics manipulations demonstrate that alpha K40 acetylation enhances flexibility and confers resilience against repeated mechanical stresses. Thus, unlike deacetylated microtubules that accumulate damage when subjected to repeated stresses, long-lived microtubules are protected from mechanical ageing through their acquisition of alpha K40 acetylatiori. In contrast to other tubulin post-translational modifications that act through rnicrotubule-associated proteins, motors and severing enzymes, intraluminal acetylation directly tunes the compliance and resilience of microtubules.