Effects of antitubulins on the redistribution of crosslinked receptors on the surface of fibroblasts and epithelial cells.

Substrate-attached normal mouse fibroblasts, transformed mouse fibroblasts (L strain), and epithelial cells (MPTR strain) were incubated with two ligands crosslinking different groups of the surface receptors: concanavalin A and cationic ferritin. Surface-attached ligands were revealed by an indirect immunofluorescence method. Incubation of control cells with these ligands induced the patching of corresponding surface receptors and the clearing of these receptors from the surface zones located on the lamellar cytoplasm near cell edges actively protruding pseudopodia. Effects of three antitubulins (microtubule-destroying drugs: Colcemid, colchicine, and vinblastine) on the ligand-induced redistribution of receptors were investigated and compared with the previously described effects of these drugs on the distribution of active cell edges. Incubation of normal and transformed fibroblasts with these antitubulins led to the disappearance of nonactive cell edges; the whole cell perimeter became active. Correspondingly, the clearing pattern of the surface receptors of fibroblasts was altered by antitubulins: the cleared area in antitubulin-treated cells formed a circular band along the whole peripheral cell edge. In epithelial cultures, in contrast to fibroblastic ones, antitubulins changed neither the distribution of the active sites of the surface nor the distribution of the areas cleared of crosslinked receptors. Thus, the specific ability of the surface areas located near the active cell edges to become cleared of crosslinked receptors is characteristic not only for the cells with intact microtubules, but also for the cells with microtubules destroyed with antitubulins.