STAT1 and STAT3 do not participate in FGF-mediated growth arrest in chondrocytes.
Activating mutations in fibroblast growth factor receptor 3 (FGFR3) cause several human skeletal dysplasias as a result of attenuation of cartilage growth. It is believed that FGFR3 inhibits chondrocyte proliferation via activation of signal transducers and activators of transcription (STAT) proteins, although the exact mechanism of both STAT activation and STAT-mediated inhibition of chondrocyte growth is unclear. We show that FGFR3 interacts with STAT1 in cells and is capable of activating phosphorylation of STAT1 in a kinase assay, thus potentially serving as a STAT1 kinase in chondrocytes. However, as demonstrated by western blotting with phosphorylation-specific antibodies, imaging of STAT nuclear translocation, STAT transcription factor assays and STAT luciferase reporter assays, FGF does not activate STAT1 or STAT3 in RCS chondrocytes, which nevertheless respond to a FGF stimulus with potent growth arrest. Moreover, addition of active STAT1 and STAT3 to the FGF signal, by means of cytokine treatment, SRC-mediated STAT activation or expression of constitutively active STAT mutants does not sensitize RCS chondrocytes to FGF-mediated growth arrest. Since FGF-mediated growth arrest is rescued by siRNA-mediated downregulation of the MAP kinase ERK1/2 but not STAT1 or STAT3, our data support a model whereby the ERK arm but not STAT arm of FGF signaling in chondrocytes accounts for the growth arrest phenotype.
Krejci
Pavel
P
Institute of Experimental Biology, Masaryk University, 61137 Brno, Czech Republic. krejcip@scimuni.cz
Salazar
Lisa
L
Goodridge
Helen S
HS
Kashiwada
Tamara A
TA
Schibler
Matthew J
MJ
Jelinkova
Petra
P
Thompson
Leslie Michels
LM
Wilcox
William R
WR
D001483:Base Sequence; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism / Q000494:pharmacology; D005346:Fibroblast Growth Factors / Q000378:metabolism* / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
D015850:Interleukin-6; D008164:Luminescent Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D016222:Fibroblast Growth Factor 2; D049452:Green Fluorescent Proteins; D005346:Fibroblast Growth Factors; D007371:Interferon-gamma; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3