Subcellular localization analysis of the closely related Fps/Fes and Fer protein-tyrosine kinases suggests a distinct role for Fps/Fes in vesicular trafficking

The subcellular localizations of the Fps/Fes and closely related Fer cytopl asmic tyrosine kinases were studied using green fluorescent protein (GFP) f usions and confocal fluorescence microscopy. In contrast to previous report s, neither kinase localized to the nucleus. Fer was diffusely cytoplasmic t hroughout the cell cycle. Fps/Fes also displayed a diffuse cytoplasmic loca lization, but in addition it showed distinct accumulations in cytoplasmic v esicles as well as in a perinuclear region consistent with the Gels. This l ocalization was very similar to that of TGN38, a known marker of the trans Golgi. The localization of Fps/Fes and TGN38 were both perturbed by brefeld in A, a fungal metabolite that disrupts the Gels apparatus. Fps/Fes was als o found to colocalize to various extents with several Rab proteins, which a re members of the monomeric G-protein superfamily involved in vesicular tra nsport between specific subcellular compartments. Using Rabs that are invol ved in endocytosis (Rab5B and Rab7) or exocytosis (Rab1A and Rab3A), we sho wed that Fps/Fes is localized in both pathways. These results suggest that Fps/Fes may play a general role in the regulation of vesicular trafficking. (C) 2001 Academic Press.