The functional interaction of 14-3-3 proteins with the ERK1/2 scaffold KSR1 occurs in an isoform-specific manner.
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.
Jagemann
Lucas R
LR
Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, 29071 Málaga, Spain.
Pérez-Rivas
Luís G
LG
Ruiz
E Josué
EJ
Ranea
Juan A
JA
Sánchez-Jiménez
Francisca
F
Nebreda
Angel R
AR
Alba
Emilio
E
Lozano
José
J
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
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