title: Nucleolin regulates phosphorylation and nuclear export of fibroblast growth factor 1 (FGF1).
abstract: Extracellular fibroblast growth factor 1 (FGF1) acts through cell surface tyrosine kinase receptors, but FGF1 can also act directly in the cell nucleus, as a result of nuclear import of endogenously produced, non-secreted FGF1 or by transport of extracellular FGF1 via endosomes and cytosol into the nucleus. In the nucleus, FGF1 can be phosphorylated by protein kinase C δ (PKCδ), and this event induces nuclear export of FGF1. To identify intracellular targets of FGF1 we performed affinity pull-down assays and identified nucleolin, a nuclear multifunctional protein, as an interaction partner of FGF1. We confirmed a direct nucleolin-FGF1 interaction by surface plasmon resonance and identified residues of FGF1 involved in the binding to be located within the heparin binding site. To assess the biological role of the nucleolin-FGF1 interaction, we studied the intracellular trafficking of FGF1. In nucleolin depleted cells, exogenous FGF1 was endocytosed and translocated to the cytosol and nucleus, but FGF1 was not phosphorylated by PKCδ or exported from the nucleus. Using FGF1 mutants with reduced binding to nucleolin and a FGF1-phosphomimetic mutant, we showed that the nucleolin-FGF1 interaction is critical for the intranuclear phosphorylation of FGF1 by PKCδ and thereby the regulation of nuclear export of FGF1.
authors.affiliation: Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Torunn
authors.initials: T
authors.lastname: Sletten
authors.affiliation: Department of Protein Biotechnology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Kostas
authors.affiliation: Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Bober
authors.affiliation: Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Vigdis
authors.initials: V
authors.lastname: Sorensen
authors.affiliation: Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Mandana
authors.initials: M
authors.lastname: Yadollahi
authors.affiliation: Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Sjur
authors.initials: S
authors.lastname: Olsnes
authors.affiliation: Department of Protein Biotechnology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Tomala
authors.affiliation: Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Otlewski
authors.affiliation: Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Zakrzewska
authors.affiliation: Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway.
authors.forename: Antoni
authors.initials: A
authors.lastname: Wiedlocha
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D016220:Fibroblast Growth Factor 1 / Q000032:analysis / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D016601:RNA-Binding Proteins / Q000378:metabolism*; D000097796:Nucleolin
chemical_list: D016220:Fibroblast Growth Factor 1; D016222:Fibroblast Growth Factor 2; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D000097796:Nucleolin