Figure 2.

MEKK1 is required for JNK activation by proinflammatory stimuli. Wild-type (+/+) and MEKK1-deficient (−/−) ES cells were left untreated or incubated with TNFα (10 ng/ml), IL-1 (10 ng/ml), LPS (15 μg/ml), or dsRNA (5 μg/ml) for the indicated times (min) after which the cells were lysed. Equal amounts (100 μg) of lysates were resolved by SDS/PAGE, transferred to a nitrocellulose membrane, and sequentially probed with antibodies to activated (phosphorylated) JNK (p-JNK) and activated (phosphorylated) ERK (p-ERK). The membranes were stripped and reprobed with antibodies to all JNK and ERK isoforms. Shown are the results of one typical experiment of at least three similar and separate experiments.