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Vieira MM, Schmidt J, Ferreira JS, She K, Oku S, Mele M, Santos AE, Duarte CB, Craig AM, Carvalho AL. Multiple domains in the C-terminus of NMDA receptor GluN2B subunit contribute to neuronal death following in vitro ischemia. Neurobiol Dis 2015; 89:223-34. [PMID: 26581639 DOI: 10.1016/j.nbd.2015.11.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 10/23/2015] [Accepted: 11/11/2015] [Indexed: 11/16/2022] Open
Abstract
Global cerebral ischemia induces selective degeneration of specific subsets of neurons throughout the brain, particularly in the hippocampus and cortex. One of the major hallmarks of cerebral ischemia is excitotoxicity, characterized by overactivation of glutamate receptors leading to intracellular Ca(2+) overload and ultimately neuronal demise. N-methyl-d-aspartate receptors (NMDARs) are considered to be largely responsible for excitotoxic injury due to their high Ca(2+) permeability. In the hippocampus and cortex, these receptors are most prominently composed of combinations of two GluN1 subunits and two GluN2A and/or GluN2B subunits. Due to the controversy regarding the differential role of GluN2A and GluN2B subunits in excitotoxic cell death, we investigated the role of GluN2B in the activation of pro-death signaling following an in vitro model of global ischemia, oxygen and glucose deprivation (OGD). For this purpose, we used GluN2B(-/-) mouse cortical cultures and observed that OGD-induced damage was reduced in these neurons, and partially prevented in wild-type rat neurons by a selective GluN2B antagonist. Notably, we found a crucial role of the C-terminal domain of the GluN2B subunit in triggering excitotoxic signaling. Indeed, expression of YFP-GluN2B C-terminus mutants for the binding sites to post-synaptic density protein 95 (PSD95), Ca(2+)-calmodulin kinase IIα (CaMKIIα) or clathrin adaptor protein 2 (AP2) failed to mediate neuronal death in OGD conditions. We focused on the GluN2B-CaMKIIα interaction and found a determinant role of this interaction in OGD-induced death. Inhibition or knock-down of CaMKIIα exerted a neuroprotective effect against OGD-induced death, whereas overexpression of this kinase had a detrimental effect. Importantly, in comparison with neurons overexpressing wild-type CaMKIIα, neurons overexpressing a mutant form of the kinase (CaMKII-I205K), unable to interact with GluN2B, were partially protected against OGD-induced damage. Taken together, our results identify crucial determinants in the C-terminal domain of GluN2B subunits in promoting neuronal death in ischemic conditions. These mechanisms underlie the divergent roles of the GluN2A- and GluN2B-NMDARs in determining neuronal fate in cerebral ischemia.
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Affiliation(s)
- Marta M Vieira
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Jeannette Schmidt
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; PDBEB - Doctoral Program in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Joana S Ferreira
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Kevin She
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Shinichiro Oku
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Miranda Mele
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Armanda E Santos
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal
| | - Carlos B Duarte
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | - Ann Marie Craig
- Brain Research Centre and Department of Psychiatry, University of British Columbia, Vancouver, BC, Canada
| | - Ana Luísa Carvalho
- CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal; Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
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A structural biology perspective on NMDA receptor pharmacology and function. Curr Opin Struct Biol 2015; 33:68-75. [PMID: 26282925 DOI: 10.1016/j.sbi.2015.07.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/08/2015] [Accepted: 07/27/2015] [Indexed: 01/09/2023]
Abstract
N-methyld-aspartate receptors (NMDARs) belong to the large family of ionotropic glutamate receptors (iGluRs), which are critically involved in basic brain functions as well as multiple neurological diseases and disorders. The NMDARs are large heterotetrameric membrane protein complexes. The extensive extracellular domains recognize neurotransmitter ligands and allosteric compounds and translate the binding information to regulate activity of the transmembrane ion channel. Here, we review recent advances in the structural biology of NMDARs with a focus on pharmacology and function. Structural analysis of the isolated extracellular domains in combination with the intact heterotetrameric NMDAR structure provides important insights into how this sophisticated ligand-gated ion channel may function.
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Sirrieh RE, MacLean DM, Jayaraman V. A conserved structural mechanism of NMDA receptor inhibition: A comparison of ifenprodil and zinc. ACTA ACUST UNITED AC 2015; 146:173-81. [PMID: 26170175 PMCID: PMC4516779 DOI: 10.1085/jgp.201511422] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 06/16/2015] [Indexed: 11/30/2022]
Abstract
Zinc and ifenprodil induce similar conformational changes in the NMDA receptor, suggesting a conserved mechanism of inhibition independent of receptor subtype and the site at which the inhibitor binds. N-methyl-d-aspartate (NMDA) receptors, one of the three main types of ionotropic glutamate receptors (iGluRs), are involved in excitatory synaptic transmission, and their dysfunction is implicated in various neurological disorders. NMDA receptors, heterotetramers typically composed of GluN1 and GluN2 subunits, are the only members of the iGluR family that bind allosteric modulators at their amino-terminal domains (ATDs). We used luminescence resonance energy transfer to characterize the conformational changes the receptor undergoes upon binding ifenprodil, a synthetic compound that specifically inhibits activation of NMDA receptors containing GluN2B. We found that ifenprodil induced an overall closure of the GluN2B ATD without affecting conformation of the GluN1 ATD or the upper lobes of the ATDs, the same mechanism whereby zinc inhibits GluN2A. These data demonstrate that the conformational changes induced by zinc and ifenprodil represent a conserved mechanism of NMDA receptor inhibition. Additionally, we compared the structural mechanism of zinc inhibition of GluN1–GluN2A receptors to that of ifenprodil inhibition of GluN1–GluN2B. The similarities in the conformational changes induced by inhibitor binding suggest a conserved structural mechanism of inhibition independent of the binding site of the modulator.
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Affiliation(s)
- Rita E Sirrieh
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
| | - David M MacLean
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
| | - Vasanthi Jayaraman
- Department of Biochemistry and Molecular Biology, Center for Membrane Biology, University of Texas Health Science Center, Houston, TX 77030
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