FIGURE 2.

Effect of SMS1 overexpression on SM and Hex-Cer levels and synthesis. A and B, quantification of sphingomyelin (A) and hexosylceramide (B) species in total lipid extracts of HepG2-SMS1 and control cells by mass spectrometry. C, NBD-ceramide incorporation into glucosylceramide in control and SMS1-overexpressing cells. D and E, effects of GCS inhibition using PDMP on the formation of NBD-glucosylceramide and NBD-SM. PDMP (25 μm) was added 1 h before the addition of NBD-ceramide, and cells were harvested at the indicated time points. Conversion of NBD-Cer to NBD-glucosylceramide or NBD-SM was quantified using HPLC. Data are shown as mean values ± S.D. (error bars) (n = 3 dishes/point). *, p < 0.05; **, p < 0.01; ***, p < 0.001 according to Student's t test. Results were confirmed in two independent experiments.