Intact and functional fibroblast growth factor (FGF) receptor-1 trafficks near the nucleus in response to FGF-1.
Exogenous fibroblast growth factor-1 (FGF-1) associates with the nucleus in a receptor-dependent manner during the entire G1 period of the BALB/c 3T3 cell cycle (Zhan, X., Hu, X., Friesel, R., and Maciag, T. (1993) J. Biol. Chem. 268, 9611-9620). To further study the role of the FGF receptor (FGFR) during this translocation, the intracellular fate of FGFR-1 protein and enzymatic activity was examined. Immunoprecipitation using multiple FGFR-1 antibodies followed by an in vitro tyrosine kinase activity assay enabled us to identify FGFR-1 as a 130-kDa phosphotyrosine-containing protein associated with the nuclear fraction of NIH 3T3 cells exposed to FGF-1. While FGFR-1 tyrosine kinase activity could be detected as a nuclear-associated protein after a 2-h exposure of the NIH 3T3 cells to FGF-1, this activity appeared to be maximal in the nuclear fraction between 4 and 12 h after FGF-1 treatment. In addition, analysis by confocal immunofluorescence microscopy of quiescent and FGF-1-stimulated NIH 3T3 cells reveal a prominent perinuclear FGFR-1 staining pattern in the cells exposed to FGF-1 but not in the quiescent population. We also observed FGFR-1 associated with the nuclear fraction in FGFR-1-transfected L6 rat myoblasts, which are known to be refractive to exogenous FGF-1 and express relatively low levels of endogenous FGFR-1. In addition, these cells also exhibited the presence of a 145-kDa phosphoprotein in the nuclear fraction that was recognized by FGFR-1 antibodies. These results suggest that the FGFR-1 may be translocated near the nucleus upon interaction with its ligand during the entire G1 period of the NIH 3T3 cell cycle as a structurally intact and functional tyrosine kinase that may be accessible to perinuclear polypeptides as a regulatory enzyme.
Prudovsky
I
I
Department of Molecular Biology, Holland Laboratory, American Red Cross, Rockville, Maryland 20855.
Savion
N
N
Zhan
X
X
Friesel
R
R
Xu
J
J
Hou
J
J
McKeehan
W L
WL
Maciag
T
T
D016475:3T3 Cells; D000818:Animals; D002451:Cell Compartmentation; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D051379:Mice; D008970:Molecular Weight; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D051496:Receptor, Fibroblast Growth Factor, Type 1; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism*; D011994:Recombinant Proteins
D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D016220:Fibroblast Growth Factor 1; C496349:Fgfr1 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D051496:Receptor, Fibroblast Growth Factor, Type 1