title: Structural Basis of p75 Transmembrane Domain Dimerization.
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.
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and.
authors.forename: Kirill D
authors.initials: KD
authors.lastname: Nadezhdin
authors.affiliation: Neurodegeneration Unit, Unidad Funcional de Investigación de Enfermedades Crónicas-Instituto de Salud Carlos III, Crta Majadahonda a Pozuelo km.2 Majadahonda, Madrid 28220, Spain.
authors.forename: Irmina
authors.initials: I
authors.lastname: García-Carpio
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Goncharuk
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and.
authors.forename: Konstantin S
authors.initials: KS
authors.lastname: Mineev
authors.affiliation: From the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow 117997, Russian Federation and aars@nmr.ru.
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Arseniev
authors.affiliation: 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.
authors.forename: Marçal
authors.identifier: 0000-0002-9376-6544
authors.initials: M
authors.lastname: Vilar
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D015153:Blotting, Western; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008055:Lipids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008823:Micelles; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D000072417:Protein Domains; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D059748:Proteolysis; D020800:Receptor, Nerve Growth Factor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D008055:Lipids; D008565:Membrane Proteins; D008823:Micelles; D020800:Receptor, Nerve Growth Factor; D003545:Cysteine
keywords: dimerization; neurotrophin; nuclear magnetic resonance (NMR); p75 neurotrophin receptor; transmembrane domain; γ-secretase