FIGURE 7.

Rap mediates the cell adhesion. A, schematic presentation of the signal relay from activated EP4 to Rap and cell invasion. AA, arachidonic acid; AC, adenylyl cyclase. B, effect of Rap activity on cell adhesion. RCC7 cells stably expressing empty vector (EV) or the GAP domain (GAP-WT) of Rap1GAP were suspended in starvation medium supplemented, or not, with PGE₂ or FBS. Adherent cells were stained with crystal violet and dye absorbance was measured at a wavelength of 570 nm. Data are presented as fold-increase above basal, where the basal absorbance in untreated cells is assigned a value of 1.0. Data shown represent the mean ± S.E. from three separate experiments. *, p < 0.05 versus nonstimulated (NS) control values. EV and GAP-WT denote, respectively, RCC7 cells stably expressing empty vector and GAP domain of Rap1GAP. C, effect of PGE₂ on E-cadherin expression. RCC7 cells were treated, or not, with PGE₂ for 24 h and lysates were analyzed by Western blotting for expression of E-cadherin (upper panel) and GAPDH (lower panel) proteins.