ERK1 and ERK2 (also known as MAPK3 and MAPK1) are 44- and 42-kDa Ser/Thr kinases, respectively. They are part of the Ras-Raf-ERK signal transduction cascade often found downstream of growth factor receptor activation. ERK1 and ERK2 were initially isolated and cloned as kinases activated in response to insulin and NGF. They are expressed in most, if not all, mammalian tissues. Dual threonine and tyrosine phosphorylation activate both ERKs, at Thr202/Tyr204 for human ERK1 and Thr185/Tyr187 for human ERK2.
Image: Stimulation of ERK1/2 phosphorylation by NDMC in NG108-15 cells. (a) Immunofluorescence analysis of phospho-ERK1/2 immunoreactivity. Cells were serum-starved for 12 h and then treated with either vehicle (control), 10 M NDMC, 1 M NTI, and NTI+NDMC for 20 min, fixed and immunostained with anti-phospho-ERK1/2 antibody followed by FITC-conjugated secondary antibody. Results are representative of three similar experiments. (b) Western blot analysis of phospho-ERK1/2 immunoreactivity. Serum-starved cells were treated for 20 min with vehicle (lane 1), 10 M NDMC (lane 2), 1 M NTI (lane 3), and NTI+NDMC (lane 4). Thereafter, cell extracts were prepared and equal amounts of proteins (30 g) were loaded in each lane. Samples were subjected to immunoblotting with either anti-phospho-ERK1/2 antibody (top) or anti-ERK1 antibody (bottom). Results are representative of three similar experiments. (c) Densitometric analysis of immunoreactive phospho-ERK1/2 bands. The optical density of the phospho-ERK1/2 bands for each drug treatment was normalized to the density of the corresponding ERK1 band and is reported as percent of control. Values are the meanSEM of three experiments. *p<0.05 vs control, NS p>0.05 vs control by one-way ANOVA followed by Dunnett's test.