Fig. 8. Expression of FRK-1 causes loss of adhesion in cultured human cells. FRK-1 was transiently expressed from an ecdysone-inducible promoter in HEK293 cells. Cells expressing FRK-1 rounded up and detached from the laminin substrate (A), whereas expression of ß-galactosidase from the same promoter had virtually no effect on adhesion of the cells to the substrate (B). Insets show higher magnification phase contrast micrographs. (C) Quantification of cell adhesion defects resulting from FRK-1 expression. The number of cells remaining attached to substrate was quantified as described in Materials and methods and the values normalized for transformation frequencies (50%) and to the values determined from cells transformed with the empty pIND vector (defined as 100% attached, or 0% floating). Experiments were performed with either fibronectin (Fn) or poly-D-lysine as a substrate. Scale bars: 50 µm.