Abstact

Tubulin-targeting agents such as paclitaxel have been a cornerstone of cancer treatment. However, the molecular basis by which prognosis-associated tubulin isotypes and mutations (that is, variants) affect drug efficacy remains unclear. Here we reveal that evolutionarily conserved tubulin residues modulate the allosteric network to determine paclitaxel efficacy. The paclitaxel resistance of human beta3-tubulin depends on a residue distant from the taxane-binding pocket. The ~2.3 A-resolution cryo-EM microtubule reconstructions demonstrate that the paclitaxel-sensitizing tubulin mutation induces allostery at the paclitaxel-binding site, intertubulin interactions and nucleotide-binding pockets. In particular, the reoriented guanine triphosphate (GTP)-hydrolyzing catalytic alpha-tubulin E254 residue enhances the GTP cap, reducing the catastrophe frequency of dynamic microtubules. Examining genome-edited cancer cells with the paclitaxel-sensitized mutant beta3-tubulin indicates that the affinities of tubulin variants for paclitaxel determine drug efficacy. Our findings provide mechanistic insights into the development of new tubulin-targeting therapeutics not only for cancer but also for tubulinopathies associated with mutations in specific tubulin isotypes.