Dynamics and allosteric potential of the AMPA receptor N-terminal domain

• Published in: The EMBO journal Vol. 30; no. 5; pp. 972 - 982
• Main Authors: Sukumaran, Madhav, Rossmann, Maxim, Shrivastava, Indira, Dutta, Anindita, Bahar, Ivet, Greger, Ingo H
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 02.03.2011; Nature Publishing Group UK; Blackwell Publishing Ltd; Nature Publishing Group
• Subjects: Allosteric Regulation; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid - metabolism; Amino Acid Sequence; AMPA receptor allostery; AMPA receptor function; Calcium - metabolism; Cell Membrane - metabolism; Cellular biology; Crystallography, X-Ray; Electrophysiology; GluA3 N-terminal domain structure; Humans; Ion Channels; Molecular biology; Molecular Sequence Data; Neurobiology; NTD ligand; Protein Conformation; Protein Multimerization; Protein Subunits; Protein Transport; Proteins; Receptors, AMPA - chemistry; Receptors, AMPA - metabolism; Sequence Homology, Amino Acid; Signal transduction; Ultracentrifugation; AMPA receptor allostery; NTD ligand; AMPA receptor function; GluA3 N‐terminal domain structure
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2011.17

Glutamate‐gated ion channels (ionotropic glutamate receptors, iGluRs) sense the extracellular milieu via an extensive extracellular portion, comprised of two clamshell‐shaped segments. The distal, N‐terminal domain (NTD) has allosteric potential in NMDA‐type iGluRs, which has not been ascribed to the analogous domain in AMPA receptors (AMPARs). In this study, we present new structural data uncovering dynamic properties of the GluA2 and GluA3 AMPAR NTDs. GluA3 features a zipped‐open dimer interface with unconstrained lower clamshell lobes, reminiscent of metabotropic GluRs (mGluRs). The resulting labile interface supports interprotomer rotations, which can be transmitted to downstream receptor segments. Normal mode analysis reveals two dominant mechanisms of AMPAR NTD motion: intraprotomer clamshell motions and interprotomer counter‐rotations, as well as accessible interconversion between AMPAR and mGluR conformations. In addition, we detect electron density for a potential ligand in the GluA2 interlobe cleft, which may trigger lobe motions. Together, these data support a dynamic role for the AMPAR NTDs, which widens the allosteric landscape of the receptor and could provide a novel target for ligand development. The crystal structure of the AMPA receptor subunit GluA3 N‐terminal domain (NTD) reveals unexpected structural flexibility of the NTD that might affect ion channel activity.