Translocation of fibroblast growth factor-10 and its receptor into nuclei of human urothelial cells.
Fibroblast growth factor-10 (FGF-10), a mitogen for the epithelial cells lining the lower urinary tract, has been identified inside urothelial cells, despite its acknowledged role as an extracellular signaling ligand. Recombinant (r)FGF-10 was determined by fluorescence microscopy optical sectioning to localize strongly to nuclei inside cultured urothelial cells. To clarify the possible role of a nuclear localization signal (NLS) in this translocation, a variant of rFGF-10 was constructed which lacked this sequence. rFGF-10(no NLS) was found in cytoplasm to a far greater degree than rFGF-10, identifying this motif as a possible NLS. Furthermore, this variant displayed poor or non-existent bioactivity compared to the wild-type protein in triggering mitogenesis in quiescent urothelial cells. The presence of rFGF-10(no NLS) in the nucleus suggested that additional interactions were also responsible for the nuclear accumulation of rFGF-10. The FGF-10 receptor was observed in cell nuclei regardless of the presence or concentration of exogenous rFGF-10 ligand. Co-localization studies between rFGF-10 and the FGF-10 receptor revealed a strong intracellular relationship between the two. This co-localization was seen in nuclei for both rFGF-10 and for rFGF-10(no NLS), although the correlation was weaker for rFGF-10(no NLS). These data show that an NLS-like motif of rFGF-10 is a partial determinant of its intracellular distribution and is necessary for its mitogenic activity. These advancements in the understanding of the activity of FGF-10 present an opportunity to engineer the growth factor as a therapeutic agent for the healing of damaged urothelial tissue.
Kosman
Jeffrey
J
Program in Human Urothelial Biology, Seattle Children's Hospital Research Institute, Seattle, Washington, USA.
Carmean
Nicole
N
Leaf
Elizabeth M
EM
Dyamenahalli
Kiran
K
Bassuk
James A
JA
D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051526:Fibroblast Growth Factor 10 / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008958:Models, Molecular; D019913:Nuclear Localization Signals; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D019459:Urothelium / Q000378:metabolism*
C496463:FGF10 protein, human; D051526:Fibroblast Growth Factor 10; D036341:Intercellular Signaling Peptides and Proteins; D019913:Nuclear Localization Signals