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Titel    NMDA receptor
Verlag    (Wikipedia)
Datum    27. December 2013
URL    http://en.wikipedia.org/w/index.php?title=NMDA_receptor&oldid=587954024

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Fragmente    5


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1.3.3. NMDA RECEPTOR

The N-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR) is the predominant molecular device for controlling synaptic plasticity and memory function. Activation of NMDRs results in the opening of an ion channel that is nonselective to cations with an equilibrium potential near 0 mV. A property of the NMDA receptor is its voltage-dependent activation, a result of ion channel blocked by extracellular Mg2+ & Zn2+ ions. This allows the flow of Na+ and Ca2+ ions into the cell and K+ out of the cell to be voltage-dependent (Dingledine et al., 1999; Liu et al., 2000; Cull et al., 2001; Paoletti et al., 2007).

NMDA receptor

[...]

The N-methyl-D-aspartate receptor (also known as the NMDA receptor or NMDAR), a glutamate receptor, is the predominant molecular device for controlling synaptic plasticity and memory function.[2]

[...] Activation of NMDA receptors results in the opening of an ion channel that is nonselective to cations with an equilibrium potential near 0 mV. A property of the NMDA receptor is its voltage-dependent activation, a result of ion channel block by extracellular Mg2+ & Zn2+ ions. This allows the flow of Na+ and small amounts of Ca2+ ions into the cell and K+ out of the cell to be voltage-dependent.[3][4][5][6]


2. Clinical Implications of Basic Research: Memory and the NMDA receptors, Fei Li and Joe Z. Tsien, N Engl J Med, 361:302, July 16, 2009

3. Dingledine R, Borges K, Bowie D, Traynelis SF (March 1999). "The glutamate receptor ion channels". Pharmacol. Rev. 51 (1): 7–61. PMID 10049997.

4. Liu Y, Zhang J (October 2000). "Recent development in NMDA receptors". Chin. Med. J. 113 (10): 948–56. PMID 11775847.

5. Cull-Candy S, Brickley S, Farrant M (June 2001). "NMDA receptor subunits: diversity, development and disease". Curr. Opin. Neurobiol. 11 (3): 327–35. doi:10.1016/S0959-4388(00)00215-4. PMID 11399431.

6. Paoletti P, Neyton J (February 2007). "NMDA receptor subunits: function and pharmacology". Curr Opin Pharmacol 7 (1): 39–47. doi:10.1016/j.coph.2006.08.011. PMID 17088105.

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Moreover, calcium flux through NMDARs is thought to be critical in synaptic plasticity, a cellular mechanism for learning and memory. The NMDA receptor is distinct in two ways: first, it is both ligand-gated and voltage-dependent; second, it requires co-activation by two ligands: glutamate and either D-serine or glycine (Kleckner et al., 1988).

The NMDA receptor forms a heterotetramer between two GluN1 and two GluN2 subunits (the subunits were previously denoted as NR1 and NR2), two obligatory NR1 subunits and two regionally localized NR2 subunits. A related gene family of NR3 A and B subunits have an inhibitory effect on receptor activity.

Calcium flux through NMDARs is thought to be critical in synaptic plasticity, a cellular mechanism for learning and memory. The NMDA receptor is distinct in two ways: first, it is both ligand-gated and voltage-dependent; second, it requires co-activation by two ligands: glutamate and either D-serine or glycine.[7]

[...]

The NMDA receptor forms a heterotetramer between two GluN1 and two GluN2 subunits (the subunits were previously denoted as NR1 and NR2), two obligatory NR1 subunits and two regionally localized NR2 subunits. A related gene family of NR3 A and B subunits have an inhibitory effect on receptor activity.


7. Kleckner, N W; Dingledine, R (1988). "Requirement for glycine in activation of NMDA-receptors expressed in Xenopus oocytes.". Science 241 (4867): 835–837. doi:10.1126/science.2841759. PMID 2841759.

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[Multiple] receptor isoforms with distinct brain distributions and functional properties arise by selective splicing of the NR1 transcripts and differential expression of the NR2 subunits. There are eight variants of the NR1 subunit produced by alternative splicing of GRIN1 (Stephenson et al., 2006): NR1-1a, NR1-1b; NR1-1a is the most abundantly expressed form. NR1-2a, NR1-2b; NR1-3a, NR1-3b; NR1-4a, NR1-4b; GluN2: NR2 subunit in vertebrates and invertebrates. While a single NR2 subunit is found in invertebrate organisms, four distinct isoforms of the NR2 subunit are expressed in vertebrates and are referred to with the nomenclature NR2A through D (coded by GRIN2A, GRIN2B, GRIN2C, GRIN2D). Each NR2 subunit has a different intracellular C-terminal domain that can interact with different sets of signaling molecules (Ryan et al., 2009). Unlike NR1 subunits, NR2 subunits are expressed differentially across various cell types and control the electrophysiological properties of the NMDA receptor. One particular subunit, NR2B, is mainly present in immature neurons and in extrasynaptic locations, and contains the binding-site for the selective inhibitor ifenprodil. Whereas NR2B is predominant in the early postnatal brain, the number of NR2A subunits grows, and eventually NR2A subunits outnumber NR2B. This is called NR2B-NR2A developmental switch, and is notable because of the different kinetics each NR2 subunit lends to the receptor (Liu et al., 2004). For instance, greater ratios of the NR2B subunit leads to NMDA receptors which remain open longer compared to those with more NR2A. This may in part account for greater memory abilities in the immediate postnatal period compared to late in life, which is the principle behind genetically-altered 'doogie mice'. The NR2B and NR2A subunits also have differential roles in mediating excitotoxic neuronal death (Liu et al., 2007). The developmental switch in subunit composition is thought to explain the developmental changes in NMDA neurotoxicity (Zhou et al., 2006). Disruption of the gene for NR2B in mice causes perinatal lethality, whereas the disruption of NR2A gene produces viable mice, although with impaired hippocampal plasticity (Sprengel et al., 1998). One study suggests that Reelin may play a role in the NMDA receptor maturation by increasing the NR2B subunit mobility (Groc et al., 2007).

Each receptor subunit has modular design and each structural module also represents a functional unit: 1) The extracellular domain contains two globular structures: a modulatory domain and a ligand-binding domain. NR1 subunits bind the co-agonist glycine and NR2 subunits bind the neurotransmitter glutamate.

Multiple receptor isoforms with distinct brain distributions and functional properties arise by selective splicing of the NR1 transcripts and differential expression of the NR2 subunits.

Each receptor subunit has modular design and each structural module also represents a functional unit:

  • The extracellular domain contains two globular structures: a modulatory domain and a ligand-binding domain. NR1 subunits bind the co-agonist glycine and NR2 subunits bind the neurotransmitter glutamate.

[...]

There are eight variants of the NR1 subunit produced by alternative splicing of GRIN1:[8]

  • NR1-1a, NR1-1b; NR1-1a is the most abundantly expressed form.
  • NR1-2a, NR1-2b;
  • NR1-3a, NR1-3b;
  • NR1-4a, NR1-4b;

GluN2

Wc 022a source.png

NR2 subunit in vertebrates (left) and invertebrates (right). Ryan et al., 2008

While a single NR2 subunit is found in invertebrate organisms, four distinct isoforms of the NR2 subunit are expressed in vertebrates and are referred to with the nomenclature NR2A through D(coded by GRIN2A, GRIN2B, GRIN2C, GRIN2D). [...] More importantly, each NR2 subunit has a different intracellular C-terminal domain that can interact with different sets of signalling molecules.[10] Unlike NR1 subunits, NR2 subunits are expressed differentially across various cell types and control the electrophysiological properties of the NMDA receptor. One particular subunit, NR2B, is mainly present in immature neurons and in extrasynaptic locations, and contains the binding-site for the selective inhibitor ifenprodil.

Whereas NR2B is predominant in the early postnatal brain, the number of NR2A subunits grows, and eventually NR2A subunits outnumber NR2B. This is called NR2B-NR2A developmental switch, and is notable because of the different kinetics each NR2 subunit lends to the receptor.[11] For instance, greater ratios of the NR2B subunit leads to NMDA receptors which remain open longer compared to those with more NR2A.[12] This may in part account for greater memory abilities in the immediate postnatal period compared to late in life, which is the principle behind genetically-altered 'doogie mice'.

[...]

The NR2B and NR2A subunits also have differential roles in mediating excitotoxic neuronal death.[13] The developmental switch in subunit composition is thought to explain the developmental changes in NMDA neurotoxicity.[14] Disruption of the gene for NR2B in mice causes perinatal lethality, whereas the disruption of NR2A gene produces viable mice, although with impaired hippocampal plasticity.[15] One study suggests that reelin may play a role in the NMDA receptor maturation by increasing the NR2B subunit mobility.[16]


8. Stephenson FA (November 2006). "Structure and trafficking of NMDA and GABAA receptors". Biochem. Soc. Trans. 34 (Pt 5): 877–81. doi:10.1042/BST0340877. PMID 17052219.

10. Ryan, T. J. & Grant, S. G. N. (2009) The origin and evolution of synapses (vol 10, pg 701, 2009). Nat Rev Neurosci 10, Doi 10.1038/Nrn2748

11. Liu XB, Murray KD, Jones EG (October 2004). "Switching of NMDA receptor 2A and 2B subunits at thalamic and cortical synapses during early postnatal development". J. Neurosci. 24 (40): 8885–95. doi:10.1523/JNEUROSCI.2476-04.2004. PMID 15470155.

12. last, first (April 2000). "title". Scientific American.

13. Liu Y, Wong TP, Aarts M, Rooyakkers A, Liu L, Lai TW, Wu DC, Lu J, Tymianski M, Craig AM, Wang YT (March 2007). "NMDA receptor subunits have differential roles in mediating excitotoxic neuronal death both in vitro and in vivo". J. Neurosci. 27 (11): 2846–57. doi:10.1523/JNEUROSCI.0116-07.2007. PMID 17360906.

14. Zhou M, Baudry M (March 2006). "Developmental changes in NMDA neurotoxicity reflect developmental changes in subunit composition of NMDA receptors". J. Neurosci. 26 (11): 2956–63. doi:10.1523/JNEUROSCI.4299-05.2006. PMID 16540573.

15. Sprengel R. et al. (1998). "Importance of the intracellular domain of NR2 subunits for NMDA receptor function in vivo". Cell 92: 279–289.

16. Groc L, Choquet D, Stephenson FA, Verrier D, Manzoni OJ, Chavis P (2007). "NMDA receptor surface trafficking and synaptic subunit composition are developmentally regulated by the extracellular matrix protein Reelin". J. Neurosci. 27 (38): 10165–75. doi:10.1523/JNEUROSCI.1772-07.2007. PMID 17881522.

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[2) The agonist-binding] module links to a membrane domain, which consists of three trans-membrane segments and a re-entrant loop reminiscent of the selectivity filter of potassium channels. The membrane domain contributes residues to the channel pore and is responsible for the receptor's high-unitary conductance, high-calcium permeability, and voltage-dependent magnesium block. Each subunit has an extensive cytoplasmic domain, which contain residues that can be directly modified by a series of protein kinases and protein phosphatases, as well as residues that interact with a large number of structural, adaptor, and scaffolding proteins. .
  • The agonist-binding module links to a membrane domain, which consists of three trans-membrane segments and a re-entrant loop reminiscent of the selectivity filter of potassium channels.
  • The membrane domain contributes residues to the channel pore and is responsible for the receptor's high-unitary conductance, high-calcium permeability, and voltage-dependent magnesium block.
  • Each subunit has an extensive cytoplasmic domain, which contain residues that can be directly modified by a series of protein kinases and protein phosphatases, as well as residues that interact with a large number of structural, adaptor, and scaffolding proteins.
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The glycine-binding modules of the NR1 and NR3 subunits and the glutamate-binding module of the NR2A subunit have been expressed as soluble proteins, and their three-dimensional structure has been solved at atomic resolution by x-ray crystallography. This has revealed a common fold with amino acid-binding bacterial proteins and with the glutamate-binding module of AMPA-receptors and kainate-receptors. The glycine-binding modules of the NR1 and NR3 subunits and the glutamate-binding module of the NR2A subunit have been expressed as soluble proteins, and their three-dimensional structure has been solved at atomic resolution by x-ray crystallography. This has revealed a common fold with amino acid-binding bacterial proteins and with the glutamate-binding module of AMPA-receptors and kainate-receptors.
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