FIGURE 7.

Cer-1-P and CERK stimulate cPLA₂α and induce LD biogenesis. A, Western blots of phospho-JNK and phospho-cPLA₂α from serum-starved CHO-K1 cells that were treated with vehicle, 2.5 μm C₂-ceramide, 2.5 μm Cer-1-P, or 7.5% FBS for 15 min. B, radioactivity released from [³H]AA prelabeled, serum-starved cells that were pretreated for 30 min with MAFP or SP600125, then stimulated for 15 min with C₂-Cer, Cer-1-P, or FBS. C, quantification of LD by flow cytometry after a 6-h treatment with C₂-Cer and Cer-1-P of FBS. D–G, cells were transiently transfected with a plasmid encoding CERK and then maintained in the absence of FBS. Overexpression of CERK increased the phosphorylation of JNK and cPLA₂α (D). CERK-transfected cells were prelabeled for 24 h with [³H]palmitate or with [³H]AA to monitor synthesis of Cer-1-P (E) and cPLA₂α activity (F), respectively. CERK also increased basal levels of LD in the absence of FBS (G). *, significantly different (p < 0.01) from control.