Paclitaxel induces NM2 ‐dependent cellular contraction through GEF ‐ H1 dissociation from microtubules and RhoA / ROCK activation in cancer cells

In this study, we have investigated the crosstalk between microtubule dynamics and actomyosin contractility in cancer cells treated with taxanes, which are chemotherapeutic agents used to treat solid tumors. We found that paclitaxel (PTXL) induced cell contraction through a mechanism that involved the rapid dissociation of GEF-H1 from microtubules, and the phosphorylation and acute activation of NM2 in a RhoA-dependent manner. Mutation of a major α-tubulin regulatory site (K40R) markedly slowed and reduced the efficiency of PTXL-induced GEF-H1 dissociation, indicating that this site is required for the full, rapid release of GEF-H1 from the microtubule lattice. Inhibitors of tubulin deacetylase HDAC6 promoted a slow release of GEF-H1 from microtubules and a lagged accumulation of phosphorylated NM2. Unexpectedly, depletion of tubulin acetyltransferase αTAT1 also induced NM2 phosphorylation, indicating that microtubule acetylation is involved in the maintenance of contractile homeostasis. Together, these results indicate that PTXL induces rapid cellular contraction dependent on the GEF-H1-RhoA-ROCK axis, in which K40 of α-tubulin gates the efficiency of GEF-H1 dissociation from microtubules, whereas homeostatic, αTAT1-dependent microtubule acetylation maintains appropriate levels of cellular contractility through long-term control of NM2 phosphorylation and actomyosin organization.