Reorganization of actin in K-562 and HL-60 cells treated with taxol.

Influence of taxol, microtubular poison, has been studied on distribution of actin. K-562 and HL-60 cells were treated with taxol in a range of concentrations 0.02-10 microM for 72 hours. The reorganization of F-actin was dependent on its dose. Phalloidin conjugated to TRITC was used to evaluate actin distribution by classical fluorescence and confocal microscopy. Actin was visualized at ultrastructural level by using a postembedding streptavidin-gold method. The treatment of K-562 and HL-60 cells with 2-10 microM of taxol resulted in an increase of F- actin in the cytoplasm, with intense labeling as a ring close to surface of the cell. In HL-60 cells a concentration of F- actin at the site of apoptotic bodies was often observed. Immunogold labeling of actin was localized in the nuclei and cytoplasm in control cells and cells treated with all doses of taxol. At higher doses, compaction of chromatin in the nucleus with strong actin labeling was observed. These observations at the ultrastructural level suggest actin involvement in chromatin reorganization during the process of apoptosis. The present study demonstrated a dose dependent reorganization of actin after treatment with taxol.