FIGURE 6.

Transfection of a dominant-negative form of MEKK1 (K432M-MEKK1) inhibits JNK phosphorylation, activation of cPLA₂α, and LD biogenesis. CHO-K1 cells were transfected with empty vector or vector encoding K432M-MEKK1. Cells were serum-starved for 24 h and then challenged for 15 min (A and B) or 6 h (C) with 7.5% FBS. A, phosphorylation levels of JNK and cPLA₂α. B, radioactivity released from cells that had been prelabeled during 24 h with 0.5 μCi/ml [³H]AA. C, indirect quantification of LD by flow cytometry. D and E, cells were transfected with empty vector (D) or with vector encoding K432M-MEKK1 (E), stimulated for 6 h with 7.5% FBS, and stained with Nile red for epifluorescence microscopy. Results in B and C are means ± S.E. of three independent experiments. *, significantly different (p < 0.01) from control.