Activation of the ERK1/2 and p38 mitogen-activated protein kinase pathways mediates fibroblast growth factor-induced growth arrest of chondrocytes.
Fibroblast growth factors (FGFs) regulate long bone development by affecting the proliferation and differentiation of chondrocytes. FGF treatment inhibits the proliferation of chondrocytes both in vitro and in vivo, but the signaling pathways involved have not been clearly identified. In this report we show that both the MEK-ERK1/2 and p38 MAPK pathways, but not phospholipase C gamma or phosphatidylinositol 3-kinase, play a role in FGF-mediated growth arrest of chondrocytes. Chemical inhibitors of the MEK1/2 or the p38 MAPK pathways applied to rat chondrosarcoma (RCS) chondrocytes significantly prevented FGF-induced growth arrest. The retinoblastoma family members p107 and p130 were previously shown to be essential effectors of FGF-induced growth arrest in chondrocytes. The dephosphorylation of p107, one of the earliest events in RCS growth arrest, was significantly blocked by MEK1/2 inhibitors but not by the p38 MAPK inhibitors, whereas that of p130, which occurs later, was partially prevented both by the MEK and p38 inhibitors. Furthermore, by expressing the nerve growth factor (NGF) receptor, TrkA, and the epidermal growth factor (EGF) receptor, ErbB1, in RCS cells we show that NGF treatment of the transfected cells caused growth inhibition, whereas EGF did not. FGF- and NGF-induced growth inhibition is accompanied by a strong and sustained activation of ERK1/2 and p38 MAPK and a decrease of AKT phosphorylation, whereas EGF induces a much more transient activation of p38 and ERK1/2 and increases AKT phosphorylation. These results indicate that inhibition of chondrocyte proliferation by FGF requires both ERK1/2 and p38 MAPK signaling and also suggest that sustained activation of these pathways is required to achieve growth inhibition.
Department of Microbiology, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
Angela
A
Raucci
Emmanuel
E
Laplantine
Alka
A
Mansukhani
Claudio
C
Basilico
D000818:Animals; D002352:Carrier Proteins / Q000032:analysis; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000032:analysis; D005346:Fibroblast Growth Factors / Q000494:pharmacology*; D008565:Membrane Proteins / Q000032:analysis; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D020932:Nerve Growth Factor / Q000494:pharmacology; D051966:Phospholipase C gamma; D051381:Rats; D020917:Receptor, trkA; D050794:STAT1 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D050794:STAT1 Transcription Factor; D015534:Trans-Activators; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor; D020932:Nerve Growth Factor; D066246:ErbB Receptors; D020917:Receptor, trkA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma