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Nuclear Translocation of fibroblast growth factor (FGF) receptors in response to FGF-2
1Scripps Research Institute, La Jolla, California 92037, USA.
Abstract:
Members of the FGF family of growth factors localize to the nuclei in a variety of different cell types. To determine whether FGF receptors are also present within nuclei and if this localization is regulated by FGFs, nuclei were prepared from quiescent and FGF-2-treated Swiss 3T3 fibroblasts and examined for the presence of FGF receptors by immunoblotting with an antibody produced against the extracellular domain of FGF receptor-1 (FGFR-1). Little or no FGFR-1 is detected in nuclei prepared from quiescent cells. When cells are treated with FGF-2, however, there is a time- and dose-dependent increase in the association of FGFR-1 immunoreactivity with the nucleus. In contrast, treatment with either EGF or 10% serum does not increase the association of FGFR-1 with the nucleus. When cell surface proteins are labeled with biotin, a biotinylated FGFR-1 is detected in the nuclear fraction prepared from FGF-2-treated, but not untreated, cells indicating that the nuclear-associated FGFR-1 immunoreactivity derives from the cell surface. The presence of FGFR-1 in the nuclei of FGF-2-treated cells was confirmed by immunostaining with a panel of different FGFR-1 antibodies, including one directed against the COOH-terminal domain of the protein. Fractionation of nuclei from FGF-2-treated cells indicates that nuclear FGFR-1 is localized to the nuclear matrix, suggesting that the receptor may play a role in regulating gene activity.
Insights
Fibroblast Growth Factor receptors (FGFRs) are found in cell nuclei after FGF-2 treatment. This nuclear localization of FGFR-1, originating from the cell surface, suggests a role in gene regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Fibroblast Growth Factors (FGFs) are known to localize within cell nuclei.
- The presence and regulation of FGF receptors (FGFRs) within nuclei remain largely uncharacterized.
Purpose of the Study:
- To investigate the presence of FGF receptors (FGFRs) within cell nuclei.
- To determine if FGFs regulate the nuclear localization of FGFRs.
- To explore the potential role of nuclear FGFRs in gene regulation.
Main Methods:
- Preparation of nuclei from quiescent and FGF-2-treated Swiss 3T3 fibroblasts.
- Immunoblotting using antibodies against FGF receptor-1 (FGFR-1) extracellular and COOH-terminal domains.
- Biotinylation of cell surface proteins to trace FGFR-1 origin.
- Nuclear fractionation and immunostaining to confirm nuclear localization and matrix association.
Main Results:
- Little to no FGFR-1 detected in nuclei of quiescent cells.
- FGF-2 treatment induces a time- and dose-dependent increase in nuclear FGFR-1.
- Nuclear FGFR-1 originates from the cell surface, confirmed by biotinylation experiments.
- EGF or serum treatment does not induce nuclear FGFR-1 accumulation.
- Nuclear FGFR-1 localizes to the nuclear matrix in FGF-2-treated cells.
Conclusions:
- FGF-2 treatment promotes the translocation of cell surface FGFR-1 into the nucleus.
- Nuclear FGFR-1 is associated with the nuclear matrix, implying a potential role in gene regulation.
- FGFR nuclear localization is specifically regulated by FGFs, not other growth factors or serum.