Translokin is an intracellular mediator of FGF-2 trafficking.
Basic fibroblast growth factor (bFGF or FGF-2) exerts its pleiotropic activities both as an exogenous and an intracellular factor. FGF-1 and FGF-2 are prototypes for this dual signalling, but the mechanisms of their intracellular actions remain unknown. Here we show that Translokin, a cytoplasmic protein of relative molecular mass 55,000 (M(r) 55K), interacts specifically with the 18K form of FGF-2. Translokin is ubiquitously expressed and colocalizes with the microtubular network. As Translokin does not interact with FGF-1, we used a strategy based on FGF-1-FGF-2 chimaeras to map the interacting regions in FGF-2 and to generate Nb1a2, a non-interacting variant of FGF-2. Although most of the FGF-2 properties are preserved in Nb1a2, this variant is defective in intracellular translocation and in stimulating proliferation. The fusion of a nuclear localization signal to Nb1a2 restores its mitogenic activity and its nuclear association. Inhibiting Translokin expression by RNA interference reduces the translocation of FGF-2 without affecting the intracellular trafficking of FGF-1. Our data show that the nuclear association of internalized FGF-2 is essential for its mitogenic activity and that Translokin is important in this translocation pathway.
Bossard
Carine
C
INSERM U589, IFR 31, Institut Louis Bugnard, CHU Rangueil, Bat L3, 31403 Toulouse, Cedex 04, France.
Laurell
Henrik
H
Van den Berghe
Loïc
L
Meunier
Sylvain
S
Zanibellato
Catherine
C
Prats
Hervé
H
D016475:3T3 Cells; D021581:Active Transport, Cell Nucleus / Q000235:genetics*; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D019556:COS Cells; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000235:genetics; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D005057:Eukaryotic Cells / Q000166:cytology / Q000378:metabolism*; D016220:Fibroblast Growth Factor 1 / Q000235:genetics / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins; D021381:Protein Transport / Q000235:genetics*; D034622:RNA Interference / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics
C474610:CEP57 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C482107:Tsp57 protein, mouse; D016222:Fibroblast Growth Factor 2; D016220:Fibroblast Growth Factor 1