title: The functional interaction of 14-3-3 proteins with the ERK1/2 scaffold KSR1 occurs in an isoform-specific manner.
abstract: Identifying 14-3-3 isoform-specific substrates and functions may be of broad relevance to cell signaling research because of the key role played by this family of proteins in many vital processes. A multitude of ligands have been identified, but the extent to which they are isoform-specific is a matter of debate. Herein we demonstrate, both in vitro and in vivo, a specific, functionally relevant interaction of human 14-3-3gamma with the molecular scaffold KSR1, which is mediated by the C-terminal stretch of 14-3-3gamma. Specific binding to 14-3-3gamma protected KSR1 from epidermal growth factor-induced dephosphorylation and impaired its ability to activate ERK2 and facilitate Ras signaling in Xenopus oocytes. Furthermore, RNA interference-mediated inhibition of 14-3-3gamma resulted in the accumulation of KSR1 in the plasma membrane, all in accordance with 14-3-3gamma being the cytosolic anchor that keeps KSR1 inactive. We also provide evidence that KSR1-bound 14-3-3gamma heterodimerized preferentially with selected isoforms and that KSR1 bound monomeric 14-3-3gamma. In sum, we have demonstrated ligand discrimination among 14-3-3 isoforms and shed light on molecular mechanisms of 14-3-3 functional specificity and KSR1 regulation.
authors.affiliation: Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, 29071 Málaga, Spain.
authors.forename: Lucas R
authors.initials: LR
authors.lastname: Jagemann
authors.forename: Luís G
authors.initials: LG
authors.lastname: Pérez-Rivas
authors.forename: E Josué
authors.initials: EJ
authors.lastname: Ruiz
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ranea
authors.forename: Francisca
authors.initials: F
authors.lastname: Sánchez-Jiménez
authors.forename: Angel R
authors.initials: AR
authors.lastname: Nebreda
authors.forename: Emilio
authors.initials: E
authors.lastname: Alba
authors.forename: José
authors.initials: J
authors.lastname: Lozano
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D019281:Dimerization; D006801:Humans; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D020033:Protein Isoforms; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D048948:14-3-3 Proteins; D008024:Ligands; D020033:Protein Isoforms; D011494:Protein Kinases; C097199:KSR-1 protein kinase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3