FIG. 4.

The Stt4-Mss4 phosphoinositide synthesis pathway is necessary for elevated IPC levels observed in csg2Δ cells. (A) Wild-type, aur1^ts, stt4^ts, mss4^ts, csg2Δ, aur1^ts/csg2Δ, stt4^ts/csg2Δ, and mss4^ts/csg2Δ cells were preincubated at 30°C for 10 min and labeled with [³H]serine for 6 h. Sphingolipids were extracted and analyzed by TLC as described in the legend to Fig. 3. (B) Quantification of sphingolipid levels in wild-type, csg2Δ, aur1^ts/csg2Δ, stt4^ts/csg2Δ, and mss4^ts/csg2Δcells that were labeled in panel A. Lipids were recovered from TLC plates by scraping and measured using a scintillation counter. The relative amount of each species was determined as a percentage of that observed in wild-type cells. The data represent the means ± standard errors of the means of results from three independent experiments.