Constitutive phosphorylation of ERK1 and ERK2 in v-fes–overexpressing macrophages.

VFB or KB cells were incubated for 16 to 18 hours in DMEM supplemented with 10% FBS and lysed. Equal amounts of proteins were separated by SDS-PAGE in a 12.5% gel and immunoblotted with polyclonal α-pERK antibody (A) or, after stripping, α-ERK antibody (B) or in a 15% gel and immunoblotted with α-ERK antibody (C). Arrows indicate the positions of ERK, pERK, or ERK* (migration-retarded ERK) bands.