ERK - Proliferation signaling

Erk1 and Erk2 are proteins of the mitogen-activated protein kinases (MAPKs) family and are major regulators on how cells respond to external factors. Erk signaling is involved in several cell responses, such as proliferation, growth, differentiation, metabolism, migration and survival.

To measure ERK activity in live cells, we employ a fluorescent protein fused to a nuclear export signal (NES) and a nuclear localization signal (NLS) and a specific target sequence for ERK. When ERK phosphorylates this target sequence, the NLS is blocked and the fluorescent protein accumulates in the cytoplasm. The activity is measured by the ratio of cytoplasm to nuclear fluorescence intensity in each individual cell.