Herbimycin- and wortmannin-sensitive activation of SEK and JNK is an early event in LPS-induced signal transduction.

(A) Quiescent BAC-1.2F5 cells were stimulated with 1.5 μg/mL LPS at 37°C for different times before solubilization. The presence of the phosphorylated, active forms of SEK (phSEK) and JNK (phJNK) and of their unmodified forms was detected by immunoblotting with the corresponding antibodies. The band labeled phJNK1 + 2 consists of co-migrating, phosphorylated forms of both kinases. (B) Inhibition of tyrosine kinases was performed by treating the cells with herbimycin A (4 μg/mL for 4 hours) before stimulation with LPS (15 minutes). (C) Cells were incubated with wortmannin (WM, 100 nmol/L, 20 minutes) before a 15-minute stimulation with 1.5 μg/mL LPS.