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J Biol Chem. 2016 Jun 3;291(23):12346-57. doi: 10.1074/jbc.M116.723585. Epub 2016 Apr 7.

Structural Basis of p75 Transmembrane Domain Dimerization.

Author information

1
From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and.
2
Neurodegeneration Unit, Unidad Funcional de Investigación de Enfermedades Crónicas-Instituto de Salud Carlos III, Crta Majadahonda a Pozuelo km.2 Majadahonda, Madrid 28220, Spain.
3
From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and aars@nmr.ru.
4
Neurodegeneration Unit, Unidad Funcional de Investigación de Enfermedades Crónicas-Instituto de Salud Carlos III, Crta Majadahonda a Pozuelo km.2 Majadahonda, Madrid 28220, Spain mvilar@ibv.csic.es.

Abstract

Dimerization of single span transmembrane receptors underlies their mechanism of activation. p75 neurotrophin receptor plays an important role in the nervous system, but the understanding of p75 activation mechanism is still incomplete. The transmembrane (TM) domain of p75 stabilizes the receptor dimers through a disulfide bond, essential for the NGF signaling. Here we solved by NMR the three-dimensional structure of the p75-TM-WT and the functionally inactive p75-TM-C257A dimers. Upon reconstitution in lipid micelles, p75-TM-WT forms the disulfide-linked dimers spontaneously. Under reducing conditions, p75-TM-WT is in a monomer-dimer equilibrium with the Cys(257) residue located on the dimer interface. In contrast, p75-TM-C257A forms dimers through the AXXXG motif on the opposite face of the α-helix. Biochemical and cross-linking experiments indicate that AXXXG motif is not on the dimer interface of p75-TM-WT, suggesting that the conformation of p75-TM-C257A may be not functionally relevant. However, rather than mediating p75 homodimerization, mutagenesis of the AXXXG motif reveals its functional role in the regulated intramembrane proteolysis of p75 catalyzed by the γ-secretase complex. Our structural data provide an insight into the key role of the Cys(257) in stabilization of the weak transmembrane dimer in a conformation required for the NGF signaling.

KEYWORDS:

dimerization; neurotrophin; nuclear magnetic resonance (NMR); p75 neurotrophin receptor; transmembrane domain; γ-secretase

PMID:
27056327
PMCID:
PMC4933281
DOI:
10.1074/jbc.M116.723585
[Indexed for MEDLINE]
Free PMC Article

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