Characterization of HSP27 phosphorylation induced by microtubule interfering agents: implication of p38 signalling pathway.

Vincristine and paclitaxel are widely used antitumoral drugs that interfere with microtubule dynamics. We have previously demonstrated that vincristine induces phosphorylation of HSP27 at serine 82 in MCF-7 cells. In this report, we show that vincristine also causes phosphorylation of serines 78 and 15. Moreover, we demonstrate that phosphorylation of this chaperone is induced by the p38 signalling pathway while the JNK pathway is not implicated. Differences between vincristine and paclitaxel treatments are also appreciated. Thus, while vincristine induces a strong phosphorylation of the three serines, paclitaxel induces a weak phosphorylation of serine 78 and has no effect over serines 82 and 15 phosphorylation. Interestingly, pre-treatment of cells with a ten-fold excess of paclitaxel abolishes vincristine-induced phosphorylation of HSP27.