FIGURE 3:

S1P from the outer environment positively regulates the apical extrusion of RasV12-transformed cells. (A) Measurement of endogenously secreted or exogenous S1P by mass spectrometry. MDCK cells and MDCK-pTR GFP-RasV12 cells were cultured alone or cocultured in the absence of FCS. The S1P concentration in the conditioned medium from each condition is compared with that in the 10% FCS–containing medium by mass spectrometry. Data are mean ± SD from three independent experiments. (B) Effect of depletion of lipids from FCS on the apical extrusion of RasV12 cells surrounded by normal MDCK cells. Data are mean ± SD from two independent experiments. *p = 0.0027, **p = 0.010. (C) Effect of exogenously added S1P on the apical extrusion of RasV12 cells surrounded by normal MDCK cells. Data are mean ± SD from three independent experiments. *p = 0.012, **p = 0.0039, ***p = 0.012. (D) Effect of exogenously added S1P in the absence or presence of JTE013 on the apical extrusion of RasV12 cells surrounded by normal MDCK cells. Data are mean ± SD from three independent experiments. *p = 0.0039. (E) Effect of exogenously added S1P on the apical extrusion of RasV12 cells surrounded by normal MDCK cells or S1PR2-knockdown MDCK cells. Data are mean ± SD from three independent experiments. *p = 0.0039. n.s., not significant (D, E).