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

Abstract

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 thelamelar cytoplasm near cell edges actively protruding pseudo dia. Effects of three antitubu ins (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.Crosslinking of surface receptors by polyvalent ligands, such as lectins or antibodies, may lead to redistribution of these receptors: patches of receptors are formed, and certain zones of the surface are cleared of these patches; this second process is often designated as capping (1-3). Experiments with substrate-attached fibroblasts and epithelial cells have shown that only specific zones of the cell surface are cleared of the receptors crosslinked by concanavalin A (Con A) (4-7). These are the zones of substrate-attached lamellar cytoplasm located near active cell edges, i.e., near the edges where pseudopodia and ruffles are continuously formed. This paper describes the results of experiments testing the effects of three different microtubule-destroying drugs (antitubulins including colchicine, Colcemid, and vinblastine) on the redistribution of crosslinked surface receptors of fibroblasts and epithelial cells. As previously described (8), incubation of fibroblasts with these antitubilins leads to disappearance of the nonactive parts of the cell edges; all of the external edge of these cells becomes active. In contrast, distribution of stable and active edges in the sheets of cultured epithelial cells is not altered by antitubulins. Correspondingly, localization of the surface zones cleared of crosslinked receptors is altered by antitubulins ...

Correlation between actin polymerization and surface receptor segregation in neuroblastoma cells treated with concanavalin A

“…From the finding that actin accumulates in lymphocytes in the same regions as receptor caps (Gabbiani et al, 1977;Oliver et al, 1977;Toh and Hard, 1977) it has been claimed that receptor patches are actively collected into a cap through their association with membrane-linked actin filaments which participate in an actinmyosin sliding filament mechanism (Edelman, 1976;Nicolson and Poste, 1976;Bourguignon and Singer, 1977;Vasiliev and Gelfand, 1977). While the presently available data points to an involvement of actin in receptor movement there exists so far no conclusive evidence for the direct association of membrane receptors with subcortical actin filaments.…”

“…Earlier studies have indicated loss of Con A receptors from the leading edge regions of fibroblasts and epithelial cells both under normal conditions (Abercrombie et al, 1972;Vasiliev et al, 1976) and in the presence of drugs which disrupt microtubules (Domnina et al, 1977). But a correlation between this phenomenon and the ultrastructure and extent of the underlying cortical filament web was not made.…”

“…But a correlation between this phenomenon and the ultrastructure and extent of the underlying cortical filament web was not made. In the experiments of Domnina et al, (1977), a lack of receptor sites for Con A on the peripheral lamellae was interpreted in terms of a centripetal clearing of surface receptors. Such a clearing has also been indicated in ultrathin sections of fibroblasts using the peroxidase, technique for the labelling of Con A receptors (Abercrombie et al, 1972).…”

“…This has been most clearly demonstrated in substrate-bound fibroblasts and epithelial cells, which show an inward flow of membrane and concanavalin A (Con A) receptors on the dorsal surface of their leading lamella (Abercrombie et al, 1970(Abercrombie et al, , 1972Harris and Dunn, 1972;Vasiliev and Gelfand, 1977). Recently we have been able to show, in studies of negatively stained cell monolayers, that the leading lamella in fibroblasts (Small and Celis, 1978) and neuroblastoma cells consists of a broad planar web of actin filaments and microspikes of colinear actin filaments singly polarized with respect to the direction of cell movement.…”

Primary and secondary chick heart fibroblasts: Fast and slow‐moving cells show no significant difference in microtubule dynamics

“…However, the results for epithelial cells show conflicting data. Whereas the polarized morphology of some epithelial cells is disrupted by the addition of such MT-specific drugs [Domnina et al, 1985 al., 19851, other reports have found that there is no dependence upon an intact MT network for the maintenance of a polarized morphology [Di Pasquale, 1975;Downie, 1975;Domnina et al, 1977;Chernoff and Overton, 1979;Euteneuer and Schliwa, 1984;Middleton et al, 19881. Recently, Middleton et al [ 19891 described that drug-induced depolymerization blocked the polarized movements of 2" but not 1" chick heart fibroblasts. 2" CHFs are derived from 1" CHFs as a result of either culture over 48 h or passaging but have rather different characteristics.…”