Specific sites within the ligand-binding domain and ion channel linkers modulate NMDA receptor gating.
Gating in the NMDA receptor is initiated in the extracellular ligand-binding domain (LBD) and is ultimately propagated via three linkers-S1-M1, M3-S2, and S2-M4-to the ion channel. M3-S2 directly couples LBD movements into channel gating, but the functional and structural contributions of S1-M1 and S2-M4 to the overall gating process are unknown. A scan of substituted cysteines in and around the NMDA receptor S1-M1 and S2-M4 with a bulky cysteine-reactive reagent identified numerous positions that showed potentiation of glutamate-activated as well as leak currents. As indexed by MK801 (dizocilpine hydrogen maleate), an open channel blocker, this potentiation was attributable to an increase in open probability, an interpretation confirmed for a subset of positions with single-channel recordings. The magnitude of this gating effect, acting through S1-M1 or S2-M4, was dependent on the intrinsic gating properties of the NMDA receptors, being more effective in the inherently low open probability GluN2C- than the higher open probability GluN2A-subunit-containing receptors. For the majority of these potentiation positions, we propose that alteration of gating arises from steric destabilization of contact interfaces where close apposition of the contacting partners is necessary for efficient channel closure. Our results therefore indicate that the NMDA receptor S1-M1 and S2-M4 linkers are dynamic during gating and can modulate the overall energetics of this process. Furthermore, the results conceptualize a mechanistic, as well as a possible structural, framework for pharmacologically targeting the linkers through noncompetitive and subunit-specific modes of action.
Talukder
Iehab
I
Graduate Program in Neuroscience and Department of Neurobiology and Behavior, State University of New York at Stony Brook, Stony Brook, New York 11794-5230, USA.
Borker
Priya
P
Wollmuth
Lonnie P
LP
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000235:genetics; D003545:Cysteine / Q000235:genetics; D016291:Dizocilpine Maleate / Q000494:pharmacology; D005260:Female; D015640:Ion Channel Gating / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D008024:Ligands; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000737:chemistry / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014982:Xenopus laevis
D008024:Ligands; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D003545:Cysteine
J Neurosci. 1999 Aug 15;19(16):6844-54
10436042
J Biol Chem. 2005 Aug 19;280(33):29708-16
15970596
J Pharmacol Exp Ther. 2005 Sep;314(3):961-71
15901795
J Neurosci. 2009 Sep 30;29(39):12045-58
19793963
J Physiol. 2007 May 15;581(Pt 1):107-28
17303642
Neuron. 2002 Jan 3;33(1):75-85
11779481
Neuron. 1998 Feb;20(2):329-39
9491993
Sci STKE. 2004 Oct 19;2004(255):re16
15494561
Mol Pharmacol. 2008 Aug;74(2):454-65
18483226
Psychopharmacology (Berl). 2003 Sep;169(3-4):215-33
12955285
Proc Biol Sci. 1992 Dec 22;250(1329):271-7
1283639
J Gen Physiol. 2007 Jun;129(6):509-25
17504910
Neuron. 1998 Feb;20(2):317-27
9491992
J Neurosci. 2007 Nov 7;27(45):12230-41
17989289
Neuroscientist. 2005 Feb;11(1):37-49
15632277
J Neurosci. 2002 Mar 15;22(6):2044-53
11896144
Mol Pharmacol. 1996 Dec;50(6):1680-8
8967993
Nature. 2009 Jun 4;459(7247):703-7
19404260
Nature. 2002 May 16;417(6886):245-53
12015593
J Physiol. 2009 Oct 1;587(Pt 19):4589-604
19687120
Biophys J. 2004 Mar;86(3):1488-501
14990476
Curr Opin Neurobiol. 2007 Jun;17(3):281-8
17419047
J Neurosci. 1995 Apr;15(4):2788-95
7536820
Nat Neurosci. 2003 Feb;6(2):144-52
12524545
Neuron. 2008 Nov 6;60(3):469-76
18995821
J Physiol. 2008 Sep 15;586(18):4425-39
18635641
Neuron. 1999 Mar;22(3):559-70
10197535
J Neurosci. 2002 Dec 1;22(23):10209-16
12451122
Science. 1992 Jan 24;255(5043):470-2
1346477
Lancet Neurol. 2008 Aug;7(8):742-55
18635022
J Neurosci. 2008 Feb 13;28(7):1546-56
18272676
Biophys J. 1998 Oct;75(4):1801-16
9746522
Nature. 2006 Mar 23;440(7083):456-62
16554805
Curr Opin Neurobiol. 2005 Jun;15(3):282-8
15919192
J Neurosci. 2005 Mar 30;25(13):3312-22
15800186
Neuron. 2005 Oct 20;48(2):279-88
16242408
J Neurosci. 2004 May 19;24(20):4728-36
15152033
Neuron. 1999 Mar;22(3):571-80
10197536
J Neurosci. 2001 Jan 15;21(2):392-400
11160420
Nature. 2009 Dec 10;462(7274):745-56
19946266
Proc Natl Acad Sci U S A. 1988 Feb;85(4):1307-11
2448800
Crit Rev Neurobiol. 2004;16(3):187-224
15701057
Curr Opin Pharmacol. 2007 Feb;7(1):39-47
17088105
Curr Drug Targets. 2007 May;8(5):573-82
17504102
Nat Rev Drug Discov. 2006 Feb;5(2):160-70
16424917