Extracellular Regulated Kinases 1/2 (ERK1/2) are part of MAPK signal transduction pathways which mediate many of the cell's responses to changes in its environment. Once activated, ERKs affect cell cycle, proliferation, migration, differentiation, transcription, learning and memory. The Ras-Raf-Mek-Erk cascade is involved in more than 30% of all human cancers. As ERKs are activated concomitantly with many other enzymes their relative contribution to the cell's response is not fully understood. Also, the distinct biological function of each ERK isoform is yet to be determined. Several works clearly suggested distinct functions for ERK1 and ERK2 in several experimental systems.
To reveal the biochemical, biological and molecular processes specifically affected by each ERK isoform, we are using intrinsically active variants of ERKs. These variants were isolated via a specific genetic screen that provided ERK molecules which are active independently of any upstream activation.
Transient expression of the variants in HEK 293T cells, showed that all ERK1 variants and most of the ERK2 variants were spontaneously phosphorylated on their phosphorylation lip, even in serum starved cells. Having confirmed that our mutants are spontaneously active, we are now testing whether the variants are integrated in the endogenous pathway and spontaneously phosphorylate endogenous substrates, such as p90RSK. We have also started to monitor the effects of the mutants on proliferation, oncogenic transformation and cell's viability.