Ligand-independent signaling by disulfide-crosslinked dimers of the p75 neurotrophin receptor

• Published in: Journal of cell science Vol. 122; no. 18; pp. 3351 - 3357
• Main Authors: Vilar, Marçal, Charalampopoulos, Ioannis, Kenchappa, Rajappa S, Reversi, Alessandra, Klos-Applequist, Joanna M, Karaca, Esra, Simi, Anastasia, Spuch, Carlos, Choi, Soyoung, Friedman, Wilma J, Ericson, Johan, Schiavo, Giampietro, Carter, Bruce D, Ibáñez, Carlos F
• Format: Journal Article
• Language: English
• Published: England The Company of Biologists Limited 15.09.2009; Company of Biologists
• Subjects: Amino Acid Sequence; Animals; Axons - drug effects; Axons - metabolism; Caspase 3 - metabolism; Cell Death - drug effects; Cercopithecus aethiops; COS Cells; Cross-Linking Reagents - metabolism; Disulfides - metabolism; Humans; Intracellular Signaling Peptides and Proteins - metabolism; JNK Mitogen-Activated Protein Kinases - metabolism; Ligands; Medicin och hälsovetenskap; Molecular Sequence Data; Mutant Proteins - drug effects; Mutant Proteins - metabolism; Nerve Growth Factors - pharmacology; NF-kappa B - metabolism; Protein Multimerization - drug effects; Protein Transport - drug effects; Rats; Receptor, Nerve Growth Factor - chemistry; Receptor, Nerve Growth Factor - metabolism; Receptor-Interacting Protein Serine-Threonine Kinase 2 - metabolism; Signal Transduction - drug effects; TNF Receptor-Associated Factor 6 - metabolism
• ISSN: 0021-9533; 1477-9137; 1477-9137
• DOI: 10.1242/jcs.055061

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 (p75NTR) forms disulfide-linked dimers at the cell surface independently of ligand binding through Cys257 in its transmembrane domain. Here, we show that crosslinking of p75NTR 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 p75NTR mutants were similar but not identical, suggesting that different configurations of p75NTR dimers might be endowed with different functions. Interestingly, crosslinked p75NTR 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 p75NTR activation by neurotrophins, and reveal a genetic approach to generate gain-of-function receptor variants with distinct functional profiles.