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

Vilar M, Charalampopoulos I, Kenchappa RS, Reversi A, Klos-Applequist JM, Karaca E, Simi A, Spuch C, Choi S, Friedman WJ, Ericson J, Schiavo G, Carter BD, Ibáñez CF
J Cell Sci. 2009 122 (Pt 18): 3351-7

PMID: 19706676 · PMCID: PMC2736866 · 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 (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.

MeSH Terms (24)

Amino Acid Sequence Animals Axons Caspase 3 Cell Death Cercopithecus aethiops COS Cells Cross-Linking Reagents Disulfides Humans Intracellular Signaling Peptides and Proteins JNK Mitogen-Activated Protein Kinases Ligands Molecular Sequence Data Mutant Proteins Nerve Growth Factors NF-kappa B Protein Multimerization Protein Transport Rats Receptor, Nerve Growth Factor Receptor-Interacting Protein Serine-Threonine Kinase 2 Signal Transduction TNF Receptor-Associated Factor 6

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