N-formyl-Met-Leu-Phe-induced oxidative burst in DMSO-differentiated HL-60 cells requires active Hsp90, but not intact microtubules.

In this study we examined whether microtubules and heat shock protein 90 (Hsp90) are involved in phorbol myristate acetate (PMA) and N-formyl-Met-Leu-Phe (fMLP)-induced oxidative burst in DMSO-differentiated HL-60 cells. Our results showed that microtubule interfering agents, paclitaxel (1-5 microM), colchicine (1-100 microM), nocodazole (1-20 microM), and vincristine (1-50 microM), did not affect either PMA or fMLP-induced oxidative burst. In contrast, radicicol, an inhibitor of Hsp90, inhibited fMLP-induced oxidative burst in time and concentration-dependent manner where IC50 value for 30 min pre-incubation was 16.5 +/- 3.5 microM radicicol. We conclude that both PMA and fMLP-induced oxidative burst in DMSO-differentiated HL-60 cells is microtubule-independent while the latter requires Hsp90 activity.