Signal transduction pathway of human fibroblast growth factor receptor 3. Identification of a novel 66-kDa phosphoprotein

J Biol Chem. 1997 Mar 7;272(10):6621-8. doi: 10.1074/jbc.272.10.6621.


Stimulation of fibroblast growth factor receptor 3 (FGFR3) results in a variety of functional effects, including regulation of epithelial cell growth and differentiation. In order to characterize the signaling pathway through which FGFR3 regulates cell growth, L6 cells lacking any endogenous FGFR were stably transfected with the two different human isoforms, FGFR3 IIIb and FGFR3 IIIc, that result from alternative splicing of exon III of the FGFR3 gene encoding the ligand binding domain. Expression of FGFR3 IIIc in stably transfected L6 cells conferred growth responses to several members of the FGF family including FGF-1, -2, -4, and -6, while FGFR3 IIIb-expressing cells responded only to FGF-1. Activation of FGFR3 upon ligand binding resulted in activation of mitogen-activated protein kinase pathway. FGFR3 utilizes two different pools of adapter protein GRB2 to link to Ras. Activated FGFR3 predominantly interacts with GRB2.Sos in complex with a previously identified 90-kDa protein and designated protein 80K-H. In addition, 80K-H.GRB2. Sos complex was found to contain a novel 66-kDa protein. Tyrosine phophorylation of the 66-kDa protein was dependent on ligand activation of FGFR3, suggesting that the 66-kDa protein may play an important role in FGFR3-specific signaling. In addition to this unique pathway, FGFR3 also links to GRB2.Sos complex via the adapter protein Shc. Furthermore, activated FGFR3 was not able to induce dissociation of GRB2.Sos complex following Sos phosphorylation. In summary, FGFR3 signaling pathway utilizes two GRB2-containing complexes; Shc.GRB2.Sos and 80K-H.pp66.GRB2.Sos; these two complexes may alternatively link FGFG3 to mitogen-activated protein kinase. Finally, activated FGFR3 was also found to result in phosphorylation of phospholipase C-gamma but reduced phosphorylation of c-Src.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing*
  • Adaptor Proteins, Vesicular Transport*
  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism
  • GRB2 Adaptor Protein
  • Humans
  • Isoenzymes / physiology
  • Membrane Proteins / metabolism
  • Phospholipase C gamma
  • Phosphoproteins / physiology*
  • Phosphoserine / metabolism
  • Phosphothreonine / metabolism
  • Phosphotyrosine / metabolism
  • Protein Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases*
  • Proteins / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-raf
  • Proto-Oncogene Proteins pp60(c-src) / metabolism
  • Rats
  • Receptor, Fibroblast Growth Factor, Type 3
  • Receptors, Fibroblast Growth Factor / physiology*
  • Shc Signaling Adaptor Proteins
  • Signal Transduction
  • Son of Sevenless Proteins
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Transfection
  • Type C Phospholipases / physiology


  • Adaptor Proteins, Signal Transducing
  • Adaptor Proteins, Vesicular Transport
  • GRB2 Adaptor Protein
  • GRB2 protein, human
  • Grb2 protein, rat
  • Isoenzymes
  • Membrane Proteins
  • Phosphoproteins
  • Proteins
  • Proto-Oncogene Proteins
  • Receptors, Fibroblast Growth Factor
  • SHC1 protein, human
  • Shc Signaling Adaptor Proteins
  • Shc1 protein, rat
  • Son of Sevenless Proteins
  • Src Homology 2 Domain-Containing, Transforming Protein 1
  • Phosphothreonine
  • Phosphoserine
  • Phosphotyrosine
  • FGFR3 protein, human
  • Protein-Tyrosine Kinases
  • Receptor, Fibroblast Growth Factor, Type 3
  • Proto-Oncogene Proteins pp60(c-src)
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-raf
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Type C Phospholipases
  • Phospholipase C gamma