FIG. 3.

MEK1 inhibitor UO126 inhibits GH-stimulated phosphorylation of serine 523 in JAK2. (A) 3T3-F442A cells were incubated with vehicle (lanes 1 to 3) or with 10 μM UO126 (lanes 4 to 6) for 30 min. Cells were then treated with vehicle (lanes 1 and 4) or with 500 ng GH/ml for 5 or 10 min (lanes 2 and 3 and lanes 5 and 6). Cell lysates were immunoblotted (IB) with αpS523 JAK2 (top panel), αJAK2 (second panel), αpErk (third panel), or αErk (bottom panel). The migration of JAK2 and the ERKs is indicated. (B) Replicates for the experiment shown in panel A were quantified and normalized to levels of JAK2. Means ± standard errors of the means are shown for n = 4.