Effect of blocking MAPK on EphB2 activation. Immunoprecipitation and Western blot analyses were performed to determine the effect on inhibition of the MAPK pathway with U0126 on the ephrinB1-induced activation of EphB2. The level of EphB2 activation is decreased in the presence of 20 μM U0126 (a and b; quantitation shown in e). The activation of MAPK by EphB2 and blockade by U0126 are shown in c and d; quantitation is shown in f. Error bars indicate range (n = 3). Pi, phosphorylated.