title: Axonal targeting of Trk receptors via transcytosis regulates sensitivity to neurotrophin responses.
abstract: Axonal targeting of trophic receptors is critical for neuronal responses to extracellular developmental cues, yet the underlying trafficking mechanisms remain unclear. Here, we report that tropomyosin-related kinase (Trk) receptors for target-derived neurotrophins are anterogradely trafficked to axons via transcytosis in sympathetic neurons. Using compartmentalized cultures, we show that mature receptors on neuronal soma surfaces are endocytosed and remobilized via Rab11-positive recycling endosomes into axons. Inhibition of dynamin-dependent endocytosis disrupted anterograde transport and localization of TrkA receptors in axons. Anterograde TrkA delivery and exocytosis into axon growth cones is enhanced by nerve growth factor (NGF), acting locally on distal axons. Perturbing endocytic recycling attenuated NGF-dependent signaling and axon growth while enhancing recycling conferred increased neuronal sensitivity to NGF. Our results reveal regulated transcytosis as an unexpected mode of Trk trafficking that serves to rapidly mobilize ready-synthesized receptors to growth cones, thus providing a positive feedback mechanism by which limiting concentrations of target-derived neurotrophins enhance neuronal sensitivity.
authors.affiliation: Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: Ascaño
authors.forename: Alissa
authors.initials: A
authors.lastname: Richmond
authors.forename: Philip
authors.initials: P
authors.lastname: Borden
authors.forename: Rejji
authors.initials: R
authors.lastname: Kuruvilla
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D019921:Biotinylation / Q000379:methods; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D034281:Dynamins / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects*; D005089:Exocytosis / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D020932:Nerve Growth Factor / Q000494:pharmacology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D020917:Receptor, trkA / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D017783:Superior Cervical Ganglion / Q000166:cytology; D013997:Time Factors; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D034281:Dynamins; D049452:Green Fluorescent Proteins; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C485184:enhanced green fluorescent protein