Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate numerous physiological cell responses including: embryogenesis, cell differentiation, proliferation, migration, apoptosis and death. Extracellular signal-regulated kinases (ERKs) 1 and 2 (ERK1/2), also known as p44 MAPK and p42 MAPK respectively, belong to one of the five major groups of MAPKs. Closely-related ERK1/2 isoforms are uniquely activated by several extracellular signals including growth factors, cytokines, hormones, and neuro-transmitters. Activation of ERK1/2 by the upstream kinases MEK1 and MEK2 occurs via dual phosphorylation on specific threonine (Thr202) and tyrosine (Tyr204) residues on the T*EY* motif. MEK1 and MEK2 are activated through receptors (tyrosine kinases or integrins) via pathways involving adaptor proteins, guanine nucleotide exchange factors, small GTP binding proteins, and MAPKKs. Activated ERK1/2 phosphorylates both, cytosolic (SOS, MNK1/2, RSKs) and nuclear targets. In the nucleus, it affects gene expression and DNA replication by the phosphorylation of MSK 1 and 2 and the transcription factors Elk-1, Sap1, and Sap2. In cultured cells, growth factors or mitogens induce rapid and transient translocation of activated ERK1/2 to nucleus. Different cell lines exhibit various duration, magnitude, and subcellular localization of activated/phosphorylated ERK1/2. The response of the protein may differ even within the same cell line depending on the dose and cell density. Assay Genie's Phospho-ERK1/2 (Thr202/Tyr204) Translocation Assay Kit provides a simple and complete assay in a ready-to-use format to visualize the translocation of activated ERK1/2 between cytoplasmic and nuclear compartments in mammalian cells.

Figures: Tamoxifen-induced translocation of phosphorylated ERK1/2 in MCF-7 cells. MCF-7 cells (1X10 5 cells per well) were grown, fixed and stained according to the included protocol. Figure 1: Cells grown in media supplemented with 10% FBS and treated with a vehicle (A) or 1X Tamoxifen for 20 min (B). Immunofluorescent staining revealed translocation of phosphorylated ERK1/2 from the cytoplasm (A) to nuclei (B). Figure 2: Cells grown in presence of 1% FBS in absence (A) or presence (B) of 1X Tamoxifen for 20 min exhibited translocation of phosphorylated ERK1/2 from nuclei (A) to cytoplasm (B). Bottom panels in Figures 1 and 2 show nuclear staining with DAPI.