Figure 5

PTN-induced CDK5 activation depends on PI3K but not c-Src or ERK1/2. (a) CDK5 activity was measured in CDK5 immunoprecipitates from HUVEC previously treated with the following pharmacological inhibitors: SU6656 (10 μΜ), wortmannin (wortmn, 100 nM) or U0126 (20 nM). CDK5 activity was evaluated by using the ADP-Glo Kinase Assay. Results are expressed as mean ± SE (n = 3) of the percent change in CDK5 activity in PTN-stimulated vs the untreated cells (set as default 100%). (b) HUVEC were incubated with PTN (100 ng/ml) in the absence or presence of roscovitine (10 μΜ). Phosphorylation of ERK1/2 was estimated in total cell lysates by Western blot as described in Materials and Methods. Phospho-ERK1/2 (pERK1/2) and total ERK1/2 (tERK1/2) amounts were quantified and the ratio pERK1/2/tERK1/2 was calculated in each lane. Results are expressed as mean ± SE (n = 3) of the percent change in phospho-ERK1/2 relative amounts in PTN-stimulated vs. the untreated cells (set as default 100%). F values of the ANOVA tests are 15.8 for (a) and 7.8 for (b).