DISRUPTION OF THE GOLGI-APPARATUS BY BREFELDIN-A BLOCKS CELL POLARIZATION AND INHIBITS DIRECTED CELL-MIGRATION

The role of the Golgi apparatus in the motile activity of fibroblasts was examined with brefeldin A (BFA), which disrupts the Golgi apparatus in a variety of cells. Upon incubation with BFA, Swiss mouse 3T3 fibroblasts lost their typical polarized morphology, in which the leading edge is characterized by intensive lamellipodia formation. BFA affected cell asymmetry as demonstrated by a decrease in the morphometric indices, dispersion, and elongation. After BFA treatment, cells showed little protrusional activity and did not form a dense actin network at the leading edge, and consequently the rate of cell migration into an experimental wound was significantly reduced. In addition, BFA prevented an increase in pseudopodial activity and prevented the formation of long processes induced by phorbol 12-myristate 13-acetate. The effects of BFA on cell shape and protrusional activity were quantitatively similar to those observed with the microtubule-disrupting agent nocodazole, although BFA had no effect on microtubule integrity. These results suggest that the integrity of both the Golgi apparatus and microtubules is necessary for the generation and maintenance of fibroblast asymmetry, which is a prerequisite for directed cell migration.