title: An intramembrane aromatic network determines pentameric assembly of Cys-loop receptors.
abstract: Cys-loop receptors are pentameric ligand-gated ion channels (pLGICs) that mediate fast synaptic transmission. Here functional pentameric assembly of truncated fragments comprising the ligand-binding N-terminal ectodomains and the first three transmembrane helices, M1-M3, of both the inhibitory glycine receptor (GlyR) alpha1 and the 5HT(3)A receptor subunits was found to be rescued by coexpressing the complementary fourth transmembrane helix, M4. Alanine scanning identified multiple aromatic residues in M1, M3 and M4 as key determinants of GlyR assembly. Homology modeling and molecular dynamics simulations revealed that these residues define an interhelical aromatic network, which we propose determines the geometry of M1-M4 tetrahelical packing such that nascent pLGIC subunits must adopt a closed fivefold symmetry. Because pLGIC ectodomains form random nonstoichiometric oligomers, proper pentameric assembly apparently depends on intersubunit interactions between extracellular domains and intrasubunit interactions between transmembrane segments.
authors.affiliation: Molecular Pharmacology, RWTH Aachen University of Aachen, Aachen, Germany.
authors.forename: Svenja
authors.initials: S
authors.lastname: Haeger
authors.forename: Dmitry
authors.initials: D
authors.lastname: Kuzmin
authors.forename: Silvia
authors.initials: S
authors.lastname: Detro-Dassen
authors.forename: Niklas
authors.initials: N
authors.lastname: Lang
authors.forename: Michael
authors.initials: M
authors.lastname: Kilb
authors.forename: Victor
authors.initials: V
authors.lastname: Tsetlin
authors.forename: Heinrich
authors.initials: H
authors.lastname: Betz
authors.forename: Bodo
authors.initials: B
authors.lastname: Laube
authors.forename: Günther
authors.initials: G
authors.lastname: Schmalzing
mesh_terms: D000818:Animals; D019295:Computational Biology / Q000379:methods; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004594:Electrophysiology; D006801:Humans; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D016296:Mutagenesis; D021122:Protein Subunits / Q000378:metabolism; D018009:Receptors, Glycine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011985:Receptors, Serotonin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology*
chemical_list: D018076:DNA, Complementary; D007473:Ion Channels; D021122:Protein Subunits; D018009:Receptors, Glycine; D011985:Receptors, Serotonin