title: Leupeptin enhances cell surface localization of fibroblast growth factor receptor 1 in adult sensory neurons by increased recycling.
abstract: Fibroblast growth factors (FGFs) act as trophic factors during development and regeneration of the nervous system. FGFs mediate their responses by activation of four types of FGF receptors (FGFR1-4). FGFR1 is expressed in adult sensory neurons of dorsal root ganglia (DRG), and overexpression of FGFR1 enhances FGF-2-induced elongative axon growth in vitro. Ligand-induced activation of FGFR1 is followed by endocytosis and rapid lysosomal degradation. We previously reported that the lysosomal inhibitor leupeptin prevents degradation of FGFR1 and promotes FGF-2-induced elongative axon growth of DRG neurons overexpressing FGFR1. Therefore, we analyzed the effects of leupeptin on intracellular sorting of FGFR1 in PC12 pheochromocytoma cells and DRG neurons. Leupeptin increased colocalization of FGFR1 with lysosomes. Furthermore, leupeptin enhanced the cell surface localization of FGFR1 by increased receptor recycling and this effect was abolished by the recycling inhibitor monensin. In addition, a lysine mutant of FGFR1, which is preferentially recycled back to the cell surface, promoted elongative axon growth of DRG neurons similar to leupeptin. In contrast, the lysosomal inhibitor bafilomycin had no effect on surface localization of FGFR1, inhibited axon growth of DRG neurons and abolished the effects of leupeptin on receptor recycling. Together, our results strongly imply that increased recycling of FGFR1 promotes axon elongation, but not axonal branching, of adult DRG neurons in vitro.
authors.affiliation: Division of Neuroanatomy, Innsbruck Medical University, Muellerstrasse 59, 6020 Innsbruck, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hausott
authors.forename: Natalie
authors.initials: N
authors.lastname: Vallant
authors.forename: Margit
authors.initials: M
authors.lastname: Hochfilzer
authors.forename: Stefan
authors.initials: S
authors.lastname: Mangger
authors.forename: Regina
authors.initials: R
authors.lastname: Irschick
authors.forename: Ellen Margrethe
authors.initials: EM
authors.lastname: Haugsten
authors.forename: Lars
authors.initials: L
authors.lastname: Klimaschewski
mesh_terms: D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D004705:Endocytosis / Q000187:drug effects; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D007976:Leupeptins / Q000494:pharmacology*; D008247:Lysosomes / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D008985:Monensin / Q000494:pharmacology; D016716:PC12 Cells; D021381:Protein Transport; D051381:Rats; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism*; D011984:Sensory Receptor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D007976:Leupeptins; D018942:Macrolides; D016222:Fibroblast Growth Factor 2; C057620:bafilomycin A; D008985:Monensin; C496350:Fgfr1 protein, rat; D051496:Receptor, Fibroblast Growth Factor, Type 1; C032854:leupeptin