English: S1P activated RhoA primarily at cell periphery. This movie shows time lapse images of an endothelial cell expressing the pTriEx-RhoA FLARE.sc Biosensor used to detect RhoA in its GTP-bound, active form. The top panel shows the CFP channel, the middle panel shows the YFP channel, and the bottom panel portrays the YFP:CFP ratio (FRET) indicating RhoA activation. The frames are at 1 min intervals. S1P (2 μM) was added at time = 0 min. The addition caused an obvious shift in GTP-bound RhoA toward the cell periphery in the first minute after the addition of S1P.