title: Dynamics of the Ras/ERK MAPK cascade as monitored by fluorescent probes.
abstract: To comprehend the Ras/ERK MAPK cascade, which comprises Ras, Raf, MEK, and ERK, several kinetic simulation models have been developed. However, a large number of parameters that are essential for the development of these models are still missing and need to be set arbitrarily. Here, we aimed at collecting these missing parameters using fluorescent probes. First, the levels of the signaling molecules were quantitated. Second, to monitor both the activation and nuclear translocation of ERK, we developed probes based on the principle of fluorescence resonance energy transfer. Third, the dissociation constants of Ras.Raf, Raf.MEK, and MEK.ERK complexes were estimated using a fluorescent tag that can be highlighted very rapidly. Finally, the same fluorescent tag was used to measure the nucleocytoplasmic shuttling rates of ERK and MEK. Using these parameters, we developed a kinetic simulation model consisting of the minimum essential members of the Ras/ERK MAPK cascade. This simple model reproduced essential features of the observed activation and nuclear translocation of ERK. In this model, the concentration of Raf significantly affected the levels of phospho-MEK and phospho-ERK upon stimulation. This prediction was confirmed experimentally by decreasing the level of Raf using the small interfering RNA technique. This observation verified the usefulness of the parameters collected in this study.
authors.affiliation: Department of Signal Transduction, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Suita-shi, Osaka 565-0871, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Fujioka
authors.forename: Kenta
authors.initials: K
authors.lastname: Terai
authors.forename: Reina E
authors.initials: RE
authors.lastname: Itoh
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Aoki
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Shinya
authors.initials: S
authors.lastname: Kuroda
authors.forename: Eisuke
authors.initials: E
authors.lastname: Nishida
authors.forename: Michiyuki
authors.initials: M
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D019556:COS Cells; D018929:Cell Culture Techniques; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D002522:Chlorocebus aethiops; D002999:Clone Cells; D003198:Computer Simulation; D003593:Cytoplasm / Q000201:enzymology / Q000378:metabolism; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000032:analysis* / Q000378:metabolism; D005434:Flow Cytometry; D031541:Fluorescence Resonance Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000032:analysis* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis* / Q000378:metabolism; D008954:Models, Biological; D015336:Molecular Probe Techniques; D015335:Molecular Probes / Q000737:chemistry*; D010766:Phosphorylation; D019908:Proto-Oncogene Proteins c-raf / Q000032:analysis* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D018631:ras Proteins / Q000032:analysis* / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes; D015335:Molecular Probes; D034741:RNA, Small Interfering; D019908:Proto-Oncogene Proteins c-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins