Figure 6.

SK1-A decreases sphingoid base accumulation in NPC1^KO cells. A, SphK1 and S1P lyase enzymatic activity in WT and NPC1^KO CHO cells was measured and normalized to total protein. B, lipids were extracted from WT, NPC1^KO, and NPC1^KI CHO cells, and sphingosine and dihydrosphingosine were measured by LC-ESI-MS/MS. C and D, NPC1^KO CHO cells were treated without or with SK1-A (10 μm) for 24 h. *, p < 0.05 compared with WT; #, p < 0.05 compared with NPC1^KO. C, in vivo SphK activity was determined by LC-ESI-MS/MS quantification of conversion of C17-sphingosine (1 μm) to C17-S1P after 30 min and normalized to total lipid phosphates. *, p < 0.05 compared with WT. D, sphingosine and dihydrosphingosine were measured by LC-ESI-MS/MS. All data are means ± S.D. (error bars) and representative of three independent experiments, each with three biological replicates. *, p < 0.05 compared with WT; #, p < 0.05 compared with NPC1^KO. p values were determined by two-tailed Student's t test (A) or one-way ANOVA followed by Tukey's post hoc analysis (B–D).