The Scaffold Protein Shoc2/SUR-8 Accelerates the Interaction of Ras and Raf

• Published in: The Journal of biological chemistry 2010-03, Vol.285 (10), p.7818-7826
• Main Authors: Matsunaga-Udagawa, Rie, Fujita, Yoshihisa, Yoshiki, Sayaka, Terai, Kenta, Kamioka, Yuji, Kiyokawa, Etsuko, Yugi, Katsuyuki, Aoki, Kazuhiro, Matsuda, Michiyuki
• Format: Article
• Language: English
• Subjects: Animals; Biosensing Techniques; Cell/Mitogens; Computer Simulation; Enzyme Activation; Epidermal Growth Factor - metabolism; Extracellular Signal-Regulated MAP Kinases - genetics; Extracellular Signal-Regulated MAP Kinases - metabolism; Fluorescence Resonance Energy Transfer; Fluorescence Resonance Energy Transfer - methods; HeLa Cells; Humans; Intracellular Signaling Peptides and Proteins - genetics; Intracellular Signaling Peptides and Proteins - metabolism; Methods/Computer Modeling; Methods/Microscopic Imaging; Mitogen-Activated Protein Kinase Kinases - genetics; Mitogen-Activated Protein Kinase Kinases - metabolism; Phosphorylation; Phosphorylation/Kinases/Serine-Threonine; Protein Binding; Raf; raf Kinases - genetics; raf Kinases - metabolism; Ras; ras Proteins - genetics; ras Proteins - metabolism; RNA Interference; Shoc2/SUR-8; Signal Transduction; Signal Transduction - physiology; Signal Transduction/Protein Kinases/MAP
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.053975

Shoc2/SUR-8 positively regulates Ras/ERK MAP kinase signaling by serving as a scaffold for Ras and Raf. Here, we examined the role of Shoc2 in the spatio-temporal regulation of Ras by using a fluorescence resonance energy transfer (FRET)-based biosensor, together with computational modeling. In epidermal growth factor-stimulated HeLa cells, RNA-mediated Shoc2 knockdown reduced the phosphorylation of MEK and ERK with half-maximal inhibition, but not the activation of Ras. For the live monitoring of Ras binding to Raf, we utilized a FRET biosensor wherein Ras and the Ras-binding domain of Raf were connected tandemly and sandwiched with acceptor and donor fluorescent proteins for the FRET measurement. With this biosensor, we found that Shoc2 was required for the rapid interaction of Ras with Raf upon epidermal growth factor stimulation. To decipher the molecular mechanisms underlying the kinetics, we developed two computational models that might account for the action of Shoc2 in the Ras-ERK signaling. One of these models, the Shoc2 accelerator model, provided a reasonable explanation of the experimental observations. In this Shoc2 accelerator model, Shoc2 accelerated both the association and dissociation of Ras-Raf interaction. We propose that Shoc2 regulates the spatio-temporal patterns of the Ras-ERK signaling pathway primarily by accelerating the Ras-Raf interaction.