Activation of the p75 Neurotrophin Receptor through Conformational Rearrangement of Disulphide-Linked Receptor Dimers

Abstract

SUMMARY Ligand-mediated dimerization has emerged as a universal mechanism of growth factor receptor activation. Recent structural studies have shown that neurotrophins interact with dimers of the p75 neurotrophin receptor (p75NTR), but the actual mechanism of receptor activation has remained elusive. Here we show that p75NTR forms disulphide-linked dimers independently of neurotrophin binding through the highly conserved Cys257 in its transmembrane domain. Mutation of Cys257 abolished neurotrophin-dependent receptor activity but did not affect downstream signaling by the p75NTR/NgR/Lingo-1 complex in response to MAG, indicating the existence of distinct, ligand-specific activation mechanisms for p75NTR. FRET experiments revealed a close association of p75NTR intracellular domains that was transiently disrupted by conformational changes induced upon NGF binding. Although mutation of Cys257 did not alter the oligomeric state of p75NTR, the mutant receptor was no longer able to propagate conformational changes to the cytoplasmic domain upon ligand binding. We propose that neurotrophins activate p75NTR by a novel mechanism involving rearrangement of disulphide-linked receptor subunits.

Bax transmembrane domain interacts with prosurvival Bcl-2 proteins in biological membranes

“…S2). Interestingly, the amino acid sequences of the Bax, Bcl-x L , and Bcl-2 TMDs (Table 1) revealed central glycine residues as potential sites for strong helix-helix interactions through ridge-into-grove arrangements, as observed for other interacting TMDs (24,(34)(35)(36)(37). These glycine residues are evolutionarily conserved (Fig.…”

Brain-derived Neurotrophic Factor (BDNF) Induces Polarized Signaling of Small GTPase (Rac1) Protein at the Onset of Schwann Cell Myelination through Partitioning-defective 3 (Par3) Protein

“…RNAi Sequences-The Par3 and its control RNAi sequences were published (2), as were the p75 and its control RNAi sequences (12). The oligonucleotides containing the shRNA of the individual RNAi sequences were placed into pSIREN-RetroQ-ZsGreen1 vector (Clontech) using the BamHI and XbaI sites as directed by the vendor.…”

Neurotrophin receptors: Old friends with new partners

“…Neurotrophin-dependent p75 NTR activation involves association of a neurotrophin dimer with CRDs 2-4 of the two extracellular domains of a p75 NTR dimer (He and Garcia, 2004). Recent studies support a model in which neurotrophin binding causes the two extracellular domains of p75 NTR dimers to move closer together, forcing the intracellular domains to splay apart in a snail-tong-like motion centered on the disulfide bond and permitting association of the intracellular domains with the signaling adapter proteins, NRIF and TRAF6 (Vilar et al, 2009a(Vilar et al, , 2009b. Intratransmembrane domain disulfide bonds, such as are present in p75 NTR , have not been described previously in other TNFR-SF family members, or in any other membrane protein for that matter.…”

“…An unusual feature of p75 NTR structure is the existence of a disulfide-linked p75 NTR dimer, formed via cysteinyl residues within the transmembrane domains. This disulfide linkage is required for effective neurotrophin-dependent signaling by p75 NTR (Vilar et al, 2009b). Neurotrophins exist physiologically as stable noncovalently associated dimers (Bothwell and Shooter, 1977).…”