title: Translocation of FGF-1 and FGF-2 across vesicular membranes occurs during G1-phase by a common mechanism.
abstract: The entry of exogenous fibroblast growth factor 2 (FGF-2) to the cytosolic/nuclear compartment was studied and compared with the translocation mechanism used by FGF-1. To differentiate between external and endogenous growth factor, we used FGF-2 modified to contain a farnesylation signal, a CaaX-box. Because farnesylation occurs only in the cytosol and nucleoplasm, farnesylation of exogenous FGF-2-CaaX was taken as evidence that the growth factor had translocated across cellular membranes. We found that FGF-2 translocation occurred in endothelial cells and fibroblasts, which express FGF receptors, and that the efficiency of translocation was increased in the presence of heparin. Concomitantly with translocation, the 18-kDa FGF-2 was N-terminally cleaved to yield a 16-kDa form. Translocation of FGF-2 required PI3-kinase activity but not transport through the Golgi apparatus. Inhibition of endosomal acidification did not prevent translocation, whereas dissipation of the vesicular membrane potential completely blocked it. The data indicate that translocation occurs from intracellular vesicles containing proton pumps and that an electrical potential across the vesicle membrane is required. Translocation of both FGF-1 and FGF-2 occurred during most of G(1) but decreased shortly before the G(1)-->S transition. A common mechanism for FGF-1 and FGF-2 translocation into cells is postulated.
authors.affiliation: The Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway.
authors.forename: Jedrzej
authors.initials: J
authors.lastname: Małecki
authors.forename: Jørgen
authors.initials: J
authors.lastname: Wesche
authors.forename: Camilla Skiple
authors.initials: CS
authors.lastname: Skjerpen
authors.forename: Antoni
authors.initials: A
authors.lastname: Wiedłocha
authors.forename: Sjur
authors.initials: S
authors.lastname: Olsnes
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002478:Cells, Cultured; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000378:metabolism*; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D016220:Fibroblast Growth Factor 1 / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017368:Protein Prenylation / Q000187:drug effects / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology*; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1; D006493:Heparin; D019869:Phosphatidylinositol 3-Kinases