Mapping the binding site of the neuroprotectant ifenprodil on NMDA receptors.
Ifenprodil is a noncompetitive antagonist of NMDA receptors highly selective for the NMDA receptor 2B (NR2B) subunit. It is widely used as a pharmacological tool to discriminate subpopulations of NMDA receptors, and derivatives are currently being developed as candidate neuroprotectants. Despite numerous studies on the mechanism of action of ifenprodil on NMDA receptors, the structural determinants responsible for the subunit selectivity have not been identified. By combining functional studies on recombinant NMDA receptors and biochemical studies on isolated domains, we now show that ifenprodil binds to the N-terminal leucine/isoleucine/valine-binding protein (LIVBP)-like domain of NR2B. In this domain, several residues, both hydrophilic and hydrophobic, were found to control ifenprodil inhibition. Their location in a modeled three-dimensional structure suggests that ifenprodil binds in the cleft of the LIVBP-like domain of NR2B by a mechanism (Venus-flytrap) resembling that of the binding of Zn on the LIVBP-like domain of NR2A. These results reinforce the proposal that the LIVBP-like domains of NMDA receptors, and possibly of other ionotropic glutamate receptors, bind modulatory ligands. Moreover, they identify the LIVBP-like domain of the NR2B subunit as a promising therapeutic target and provide a framework for designing structurally novel NR2B-selective antagonists.
Laboratoire de Neurobiologie, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8544, Ecole Normale Supérieure, 75005 Paris, France.
Florent
F
Perin-Dureau
Julie
J
Rachline
Jacques
J
Neyton
Pierre
P
Paoletti
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000493:pharmacokinetics*; D016297:Mutagenesis, Site-Directed; D018696:Neuroprotective Agents / Q000493:pharmacokinetics*; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010880:Piperidines / Q000493:pharmacokinetics*; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014357:Trypsin / Q000378:metabolism; D014982:Xenopus laevis
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D018696:Neuroprotective Agents; D010880:Piperidines; D021122:Protein Subunits; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; D014357:Trypsin; C010739:ifenprodil