Figure 2.

MEK inhibitor PD09059 prevents inhibition of CDK by NGF. TRK1 cells were grown for 16 hr in normal growth medium in the presence or absence of 20 nM NGF. Simultaneous to the addition of NGF, cells were treated with vehicle (DMSO, 0.2%) or 40 μM PD98059. The activity of the CDKs was assayed by immunoprecipitation kinase assay (12), using histone H1 (A) or glutathione S-transferase-Rb (aa 379–928) (B) as substrates. Similar results were obtained in at least four independent experiments.