Intermediate filament aggregation: effect on cell topology, cell spreading and surface transport.

When chick fibroblasts are treated with cytochalasin-B and then transferred to medium containing colcemid, they become very flat and acquire corrugations on the apical cell surface. Bundles of intermediate filaments are found beneath the cell membrane in the troughs of the corrugations. When subcultured in colcemid, the cells retain the bundles of intermediate filaments and corrugations, and spread out both on untreated surfaces and on surfaces coated with gold particles. Gold particles are transported over the apical surface and phagocytosed by the cell. There is no accumulation of gold particles on the membrane under which the cables of intermediate filaments lie, and phagocytosed gold is excluded from the area occupied by the cables. These experiments indicate that a cell does not need microtubules and (a normal distribution of) intermediate filaments in order to spread, or to pick up, transport and phagocytose particulate material. The experimental aggregation of intermediate filaments does, however, alter the cell topology and the way in which particles are transported over the surface and ingested.