title: Ligand-induced internalization of the p75 neurotrophin receptor: a slow route to the signaling endosome.
abstract: The nerve growth factor (NGF) family of neurotrophins binds two classes of cell-surface receptors, trk receptor tyrosine kinases and the shared p75 receptor. Rapid internalization and retrograde trafficking of neurotrophin-trk complexes have been demonstrated in a number of systems and are thought to transmit trophic signals from terminals to neuronal cell bodies. In contrast, the internalization and trafficking of neurotrophin-p75 complexes are not well understood. In this study, we used biotinylated NGF and a fluorescent-labeled anti-p75 antibody to follow the kinetics and route of ligand-induced internalization of the p75 receptor in cycling and differentiated PC12 cells. Binding of neurotrophins to p75 induced internalization at a rate approximately three times slower than that of transferrin and NGF-TrkA complexes in the same cells. The ligand-p75 complex was internalized via clathrin-coated pits into early endosomes and eventually accumulated in recycling endosomes in the cell body and vesicles colabeled by the cholera toxin B-subunit in the growth cones. Both internalized ligand and p75 were protected from proteolytic degradation and accumulated in vesicles that did not undergo acidification. Finally, NGF induced endosomal association of p75 and its MAGE interactors, necdin and NRAGE. These data suggest that signaling endosomes containing activated p75 are involved in neurotrophin signaling, and that such endosomes may be temporally and spatially distinct from those containing trk receptors.
authors.affiliation: Molecular Neurobiology Group, Department of Biological Chemistry, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Francisca C
authors.initials: FC
authors.lastname: Bronfman
authors.forename: Marianna
authors.initials: M
authors.lastname: Tcherpakov
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Jovin
authors.forename: Mike
authors.initials: M
authors.lastname: Fainzilber
mesh_terms: D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001370:Axonal Transport / Q000502:physiology; D001667:Binding, Competitive / Q000187:drug effects / Q000502:physiology; D001710:Biotin / Q000737:chemistry; D019921:Biotinylation; D002352:Carrier Proteins / Q000493:pharmacokinetics; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism*; D005456:Fluorescent Dyes; D007455:Iodine / Q000737:chemistry; D008024:Ligands; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000493:pharmacokinetics; D009363:Neoplasm Proteins; D020932:Nerve Growth Factor / Q000378:metabolism / Q000493:pharmacokinetics; D009414:Nerve Growth Factors / Q000378:metabolism / Q000493:pharmacokinetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D016716:PC12 Cells; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D020800:Receptor, Nerve Growth Factor; D020917:Receptor, trkA; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013347:Subcellular Fractions / Q000737:chemistry; D014168:Transferrin / Q000378:metabolism / Q000493:pharmacokinetics
chemical_list: D000906:Antibodies; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D005456:Fluorescent Dyes; D008024:Ligands; D046911:Macromolecular Substances; C486542:Maged1 protein, rat; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D020800:Receptor, Nerve Growth Factor; D017475:Receptors, Nerve Growth Factor; D014168:Transferrin; C474104:biotinylated nerve growth factor; C069766:necdin; D001710:Biotin; D020932:Nerve Growth Factor; D007455:Iodine; D020917:Receptor, trkA