PP1 has no effect on the activation of JNK and p42, p44 MAPK.

BAF/WT cells were stimulated with G-CSF for 10 minutes with or without pretreatment with wortmannin (WM) or PP1. (A) Whole-cell extracts were prepared, and JNK was immunoprecipitated with specific antiserum. The kinase activity of JNK was determined by in vitro kinase assay using ATF2 as a substrate (upper panel). The membrane was subsequently probed for JNK (lower panel). (B) The same cell extracts were also used in Western blot analysis for the determination of p42, p44 MAPK phosphorylation using a phospho-specific antibody (upper panel). Equal loading was confirmed by incubating the membrane with an anti p42, p44 MAPK antibody (lower panel). (C) Whole-cell extracts were also examined for Akt phosphorylation.