Fibrillar systems in cell motility

Several types of cytoplasmic fibres are found in various cultured fibroblastic and epithelial-like cells (including the BHK-21 and BSC-1 cell lines): microtubules (about 25 nm in diameter), filaments (about 10 nm in diameter) and microfilaments (about 6 nm in diameter). The distribution, coordinated activities and the dynamic nature of these fibres suggest that they function in several aspects of cell motility, including cell spreading, locomotion and changes in cell shape during the normal life cycle. Experiments with cycloheximide indicate that pools of precursors, which might be used to assemble fibres, are available in cells during cell spreading. Colchicine treatment demonstrates that microtubules are important in the formation and maintenance of the shape of fibroblastic cells, but not that of epithelial cells. The use of cytochalasin B and its interactions with the cell surface are also discussed.