Sef Is a Spatial Regulator for Ras/MAP Kinase Signaling

• DOI: 10.1016/j.devcel.2004.05.019
• Publication Date: 2004-07-13T22:24:08Z
• Authors: Satoru Torii; Morioh Kusakabe; Takuya Yamamoto; Momoko Maekawa; Eisuke Nishida
• Keywords: Cell Nucleus; Mitogen-Activated Protein Kinase Kinases; Cytoplasm; 0303 health sciences; MAP Kinase Signaling System; Active Transport, Cell Nucleus; MAP Kinase Kinase 1; Receptors, Interleukin; Ribosomal Protein S6 Kinases, 90-kDa; DNA-Binding Proteins; Protein Transport; 03 medical and health sciences; Proto-Oncogene Proteins; COS Cells; Chlorocebus aethiops; Animals; Humans; Mitogen-Activated Protein Kinases; Phosphorylation; Developmental Biology; HeLa Cells; Transcription Factors; ets-Domain Protein Elk-1

Spatiotemporal control of the Ras/ERK MAP kinase signaling pathway is among the key mechanisms for regulating a wide variety of cellular processes. In this study, we report that human Sef (hSef), a recently identified inhibitor whose action mechanism has not been fully defined, acts as a molecular switch for ERK signaling by specifically blocking ERK nuclear translocation without inhibiting its activity in the cytoplasm. Thus, hSef binds to activated forms of MEK, inhibits the dissociation of the MEK-ERK complex, and blocks nuclear translocation of activated ERK. Consequently, hSef inhibits phosphorylation and activation of the nuclear ERK substrate Elk-1, while it does not affect phosphorylation of the cytoplasmic ERK substrate RSK2. Downregulation of endogenous hSef by hSef siRNA enhances the stimulus-induced ERK nuclear translocation and the activity of Elk-1. These results thus demonstrate that hSef acts as a spatial regulator for ERK signaling by targeting ERK to the cytoplasm.