title: Ubiquitination of TrkA by Nedd4-2 regulates receptor lysosomal targeting and mediates receptor signaling.
abstract: The nerve growth factor receptor TrkA (tropomyosin-related kinase receptor) participates in the survival and differentiation of several neuronal populations. The C-terminal tail of TrkA contains a PPXY motif, the binding site of the E3 ubiquitin-ligase Nedd4-2 (neural precursor cell expressed, developmentally down-regulated 4-2). In order to analyze the role of Nedd4-2 ubiquitination on TrkA function, we generated three TrkA mutants, by introducing point mutations on conserved hydrophobic amino acids - Leu784 and Val790 switched to Ala. TrkA mutants co-localized and co-immunoprecipitated more efficiently with Nedd4-2 and consequently a strong increase in the basal multimonoubiquitination of the mutant receptors was observed. In addition, we found a decrease in TrkA abundance because of the preferential sorting of mutant receptors towards the late endosome/lysosome pathway instead of recycling back to the plasma membrane. Despite the reduction in the amount of membrane receptor caused by the C-terminal changes, TrkA mutants were able to activate signaling cascades and were even more efficient in promoting neurite outgrowth than the wild-type receptor. Our results demonstrate that the C-terminal tail hydrophobicity of TrkA regulates Nedd4-2 binding and activity and therefore controls receptor turnover. In addition, TrkA multimonoubiquitination does not interfere with the activation of signaling cascades, but rather potentiates receptor signaling leading to differentiation.
authors.affiliation: Institut de Recerca Biomèdica de Lleida (IRBLleida), Universitat de Lleida, Lleida, Spain.
authors.forename: Maya V
authors.initials: MV
authors.lastname: Georgieva
authors.forename: Yolanda
authors.initials: Y
authors.lastname: de Pablo
authors.forename: Daniel
authors.initials: D
authors.lastname: Sanchis
authors.forename: Joan X
authors.initials: JX
authors.lastname: Comella
authors.forename: Marta
authors.initials: M
authors.lastname: Llovera
mesh_terms: D000818:Animals; D001710:Biotin / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics; D047468:Immunoprecipitation / Q000379:methods; D051907:Lysosomal Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D020932:Nerve Growth Factor / Q000494:pharmacology; D016716:PC12 Cells; D011485:Protein Binding / Q000235:genetics; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D020917:Receptor, trkA / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014162:Transfection / Q000379:methods; D054875:Ubiquitination / Q000187:drug effects / Q000502:physiology*; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D001710:Biotin; D003546:Cysteine Endopeptidases; D049452:Green Fluorescent Proteins; D051907:Lysosomal Membrane Proteins; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; C489117:Lamp1 protein, rat; D052118:Lysosomal-Associated Membrane Protein 1; C490359:Casp2 protein, rat