FIGURE 2:

S1P produced by RasV12-transformed cells or the surrounding normal cells does not play a positive role in apical extrusion. (A) TLC of sphingolipids extracted from [³H]sphingosine-labeled MDCK cells, MDCK-pTR GFP-RasV12 cells, or the mixture of MDCK and MDCK-pTR GFP-RasV12 cells cultured in the absence or presence of SphKI2. (B) Quantification of the apical extrusion of RasV12 cells. The relatively low frequency of apical extrusion in the absence of SphKI2 may be due to high concentration of dimethyl sulfoxide (0.16%). Data are mean ± SD from three independent experiments.