Substrate-dependent cellular behavior of Swiss 3T3 fibroblasts and activation of Rho family during adhesion and spreading processes

Recent biochemical studies revealed that intracellular Rho guanosine triphosphatases (Rho, Rac1, and Cdc42) are key regulatory molecules that link surface receptors to cytoskeletal organization and regulation of cell shape/morphology/motility. In this study, Swiss 3T3 fibroblasts were cultured on three representative substrates [tissue culture polystyrene dishes, nontreated polystyrene, and poly(ethylene terephthalate)] for 24 h after plating. Time-dependent changes in cell shape, morphology, cytoskeletal dynamics, and motility as well as Rho family activities were determined on each substrate. The cells on tissue culture polystyrene and on poly(ethylene terephthalate), which induced rapid and relatively rapid cell spreading, respectively, expressed Rac1 and Cdc42 activities continuously during the observation period. In contrast, such activities were suppressed in cells on polystyrene, which induced slow spreading but the highest cell motility compared with the other two substrates. Although a clear-cut relationship between cellular behavior and Rho family activation was not obtained, substrate-dependent coordinated control of cellular activities by Rho family is discussed.