Signals transmitted by ERK MAP Kinases regulate the functions of multiple substrates present in the nucleus and the cytoplasm. Once phosphorylated, ERKs dimerize. The functions of these dimers had remained elusive until recently when we demonstrated that ERK dimers are assembled using scaffolds proteins as platforms. Dimerization is critical for connecting the scaffolded ERK complex to cognate cytoplasmic substrates. Contrarily, nuclear substrates associate to ERK monomers. These results identify dimerization as a key determinant of the spatial specificity of ERK signals. Moreover, we showed that preventing ERK dimerization, without affecting ERK phosphorylation, is sufficient for attenuating cellular proliferation, transformation, and tumor development. Thus, analyzing ERK dimerization will be an important factor in the future for determining, for example, the real impact on the ERK pathway of some drugs that do not affect ERK phosphorylation. Herein, we describe user-friendly methods for such purpose.
