title: Binding of ArgTX-636 in the NMDA receptor ion channel.
abstract: The N-methyl-d-aspartate receptors (NMDARs) constitute an important class of ligand-gated cation channels that are involved in the majority of excitatory neurotransmission in the human brain. Compounds that bind in the NMDAR ion channel and act as blockers are use- and voltage-dependent inhibitors of NMDAR activity and have therapeutic potential for treatment of a variety of brain diseases or as pharmacological tools for studies of the neurobiological role of NMDARs. We have performed a kinetic analysis of the blocking mechanism of the prototypical polyamine toxin NMDAR ion channel blocker argiotoxin-636 (ArgTX-636) at recombinant GluN1/2A receptors to provide detailed information on the mechanism of block. The predicted binding site of ArgTX-636 is in the pore region of the NMDAR ion channel formed by residues in the transmembrane M3 and the M2 pore-loop segments of the GluN1 and GluN2A subunits. To assess the predicted binding mode in further detail, we performed an alanine- and glycine-scanning mutational analysis of this pore-loop segment to systematically probe the role of pore-lining M2 residues in GluN1 and GluN2A in the channel block by ArgTX-636. Comparison of M2 positions in GluN1 and GluN2A where mutation influences ArgTX-636 potency suggests differential contribution of the M2-loops of GluN1 and GluN2A to binding of ArgTX-636. The results of the mutational analysis are highly relevant for the future structure-based development of argiotoxin-derived NMDAR channel blockers.
authors.affiliation: Department of Drug Design and Pharmacology, University of Copenhagen, 2100 København, Denmark.
authors.forename: Mette H
authors.initials: MH
authors.lastname: Poulsen
authors.affiliation: Department of Drug Design and Pharmacology, University of Copenhagen, 2100 København, Denmark.
authors.forename: Jacob
authors.initials: J
authors.lastname: Andersen
authors.affiliation: Department of Drug Design and Pharmacology, University of Copenhagen, 2100 København, Denmark.
authors.forename: Rune
authors.initials: R
authors.lastname: Christensen
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Kasper B
authors.initials: KB
authors.lastname: Hansen
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Traynelis
authors.affiliation: Department of Drug Design and Pharmacology, University of Copenhagen, 2100 København, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Strømgaard
authors.affiliation: Department of Drug Design and Pharmacology, University of Copenhagen, 2100 København, Denmark. Electronic address: ask@sund.ku.dk.
authors.forename: Anders Skov
authors.initials: AS
authors.lastname: Kristensen
mesh_terms: D000818:Animals; D001665:Binding Sites; D004594:Electrophysiology; D018698:Glutamic Acid / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007210:Indoleacetic Acids / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D016296:Mutagenesis; D009154:Mutation / Q000235:genetics; D018408:Patch-Clamp Techniques; D011073:Polyamines / Q000494:pharmacology*; D011487:Protein Conformation; D021122:Protein Subunits; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000378:metabolism*; D013111:Spider Venoms / Q000494:pharmacology*
chemical_list: D007210:Indoleacetic Acids; D007473:Ion Channels; D011073:Polyamines; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; D013111:Spider Venoms; C558368:argiotoxin-636; D018698:Glutamic Acid
keywords: NMDA receptor; channel block; electrophysiology; glutamate receptor; mutational analysis