title: Ligand-independent signaling by disulfide-crosslinked dimers of the p75 neurotrophin receptor.
abstract: Dimerization is recognized as a crucial step in the activation of many plasma membrane receptors. However, a growing number of receptors pre-exist as dimers in the absence of ligand, indicating that, although necessary, dimerization is not always sufficient for signaling. The p75 neurotrophin receptor (p75(NTR)) forms disulfide-linked dimers at the cell surface independently of ligand binding through Cys257 in its transmembrane domain. Here, we show that crosslinking of p75(NTR) dimers by cysteine-scanning mutagenesis results in constitutive, ligand-independent activity in several pathways that are normally engaged upon neurotrophin stimulation of native receptors. The activity profiles of different disulfide-crosslinked p75(NTR) mutants were similar but not identical, suggesting that different configurations of p75(NTR) dimers might be endowed with different functions. Interestingly, crosslinked p75(NTR) mutants did not mimic the effects of the myelin inhibitors Nogo or MAG, suggesting the existence of ligand-specific activation mechanisms. Together, these results support a conformational model of p75(NTR) activation by neurotrophins, and reveal a genetic approach to generate gain-of-function receptor variants with distinct functional profiles.
authors.affiliation: Division of Molecular Neurobiology, Department of Neuroscience, Karolinska Institute, 17177 Stockholm, Sweden.
authors.forename: Marçal
authors.initials: M
authors.lastname: Vilar
authors.forename: Ioannis
authors.initials: I
authors.lastname: Charalampopoulos
authors.forename: Rajappa S
authors.initials: RS
authors.lastname: Kenchappa
authors.forename: Alessandra
authors.initials: A
authors.lastname: Reversi
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Klos-Applequist
authors.forename: Esra
authors.initials: E
authors.lastname: Karaca
authors.forename: Anastasia
authors.initials: A
authors.lastname: Simi
authors.forename: Carlos
authors.initials: C
authors.lastname: Spuch
authors.forename: Soyoung
authors.initials: S
authors.lastname: Choi
authors.forename: Wilma J
authors.initials: WJ
authors.lastname: Friedman
authors.forename: Johan
authors.initials: J
authors.lastname: Ericson
authors.forename: Giampietro
authors.initials: G
authors.lastname: Schiavo
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Carter
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Ibáñez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism; D019556:COS Cells; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002522:Chlorocebus aethiops; D003432:Cross-Linking Reagents / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008024:Ligands; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009414:Nerve Growth Factors / Q000494:pharmacology; D055503:Protein Multimerization / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D020800:Receptor, Nerve Growth Factor / Q000737:chemistry* / Q000378:metabolism*; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D004220:Disulfides; D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D050505:Mutant Proteins; D016328:NF-kappa B; D009414:Nerve Growth Factors; D020800:Receptor, Nerve Growth Factor; D048029:TNF Receptor-Associated Factor 6; D053475:Receptor-Interacting Protein Serine-Threonine Kinase 2; D048031:JNK Mitogen-Activated Protein Kinases; D053148:Caspase 3
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