title: FGFR2-Cbl interaction in lipid rafts triggers attenuation of PI3K/Akt signaling and osteoblast survival.
abstract: Fibroblast growth factor receptor (FGFR) signaling plays an important role in skeletogenesis. The molecular mechanisms triggered by activated FGFR in bone forming cells are however not fully understood. In this study, we identify a role for phosphatidylinositol 3-kinase (PI3K) signaling in cell apoptosis induced by FGFR2 activation in osteoblasts. We show that FGFR2 activation leads to decrease PI3K protein levels, resulting in attenuation of PI3K signaling in human osteoblasts. Biochemical and molecular analyses revealed that the attenuated PI3K signaling induced by FGFR2 activation is due to increased Cbl-PI3K molecular interaction mediated by the Cbl Y731 residue, which results in increased PI3K ubiquitination and proteasome degradation. Biochemical and immunocytochemical analyses showed that FGFR2 and Cbl interact in raft micro-domains at the plasma membrane. FGFR2 activation increases FGFR2 and Cbl recruitment in micro-domains, resulting in increased molecular interactions. Consistently, functional analyses showed that the attenuation of PI3K/Akt signaling triggered by FGFR2 activation results in increased osteoblast apoptosis. These results identify a functional molecular mechanism by which activated FGFR2 recruits Cbl in raft micro-domains to trigger PI3K ubiquitination and proteasome degradation, and reveal a novel role for PI3K/Akt attenuation in the control of osteoblast survival by FGFR2 signaling.
authors: INSERM U606 and University Paris 7, Paris, France.
authors: Cécilie
authors: C
authors: Dufour
authors: Hind
authors: H
authors: Guenou
authors: Karim
authors: K
authors: Kaabeche
authors: Daniel
authors: D
authors: Bouvard
authors: Archana
authors: A
authors: Sanjay
authors: Pierre J
authors: PJ
authors: Marie
mesh_terms: D017209:Apoptosis / Q000502:physiology; D002460:Cell Line; D002470:Cell Survival; D006801:Humans; D021962:Membrane Microdomains / Q000378:metabolism*; D009154:Mutation; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000378:metabolism*; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D025801:Ubiquitin; D050721:Proto-Oncogene Proteins c-cbl; D019869:Phosphatidylinositol 3-Kinases; C496353:FGFR2 protein, human; D051497:Receptor, Fibroblast Growth Factor, Type 2; D051057:Proto-Oncogene Proteins c-akt; C067419:CBL protein, human