Fig. 1.

SGMS1^GT cells have reduced levels of SM. (A) Schematic representation of the SM biosynthesis pathway in mammalian cells. SGMS1-deficient KBM7 cells and myriocin, an SPT inhibitor (marked in box) show a block in sphingolipid biosynthesis. (B) RT-PCR analysis showing the absence of the SGMS1 transcript in SGMS1^GT cells. (C) Autoradiogram of a TLC separation of lipid extracts of KBM7 and SGMS1^GT cells metabolically labeled with the SM precursor [¹⁴C]-choline. (D) Quantification of the [¹⁴C]-SM and [¹⁴C]-PC signals from [¹⁴C]-choline labeling experiment in C. (E and F) Total lipids were extracted from KBM7 and SGMS1^GT cells and subjected to MS/MS. Levels of sphingolipids (E) and glycerophospholipids (F) are expressed as mole percent of total lipid analyzed. (G) Total phosphate and cholesterol levels of KBM7 and SGMS1^GT cells were determined and presented as mole percent relative to the control. Error bars represent SD of three (D) or two (E–G) independent experiments. Cer, ceramide; PC, phosphatidylcholine; PS, phosphatidylserine; PI, phosphatidylinositol.