title: Potentiation of alpha7 nicotinic acetylcholine receptors via an allosteric transmembrane site.
abstract: Positive allosteric modulators of alpha7 nicotinic acetylcholine receptors (nAChRs) have attracted considerable interest as potential tools for the treatment of neurological and psychiatric disorders such as Alzheimer's disease and schizophrenia. However, despite the potential therapeutic usefulness of these compounds, little is known about their mechanism of action. Here, we have examined two allosteric potentiators of alpha7 nAChRs (PNU-120596 and LY-2087101). From studies with a series of subunit chimeras, we have identified the transmembrane regions of alpha7 as being critical in facilitating potentiation of agonist-evoked responses. Furthermore, we have identified five transmembrane amino acids that, when mutated, significantly reduce potentiation of alpha7 nAChRs. The amino acids we have identified are located within the alpha-helical transmembrane domains TM1 (S222 and A225), TM2 (M253), and TM4 (F455 and C459). Mutation of either A225 or M253 individually have particularly profound effects, reducing potentiation of EC(20) concentrations of acetylcholine to a tenth of the level seen with wild-type alpha7. Reference to homology models of the alpha7 nAChR, based on the 4A structure of the Torpedo nAChR, indicates that the side chains of all five amino acids point toward an intrasubunit cavity located between the four alpha-helical transmembrane domains. Computer docking simulations predict that the allosteric compounds such as PNU-120596 and LY-2087101 may bind within this intrasubunit cavity, much as neurosteroids and volatile anesthetics are thought to interact with GABA(A) and glycine receptors. Our findings suggest that this is a conserved modulatory allosteric site within neurotransmitter-gated ion channels.
authors.affiliation: Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Gareth T
authors.initials: GT
authors.lastname: Young
authors.forename: Ruud
authors.initials: R
authors.lastname: Zwart
authors.forename: Alison S
authors.initials: AS
authors.lastname: Walker
authors.forename: Emanuele
authors.initials: E
authors.lastname: Sher
authors.forename: Neil S
authors.initials: NS
authors.lastname: Millar
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000495:Allosteric Site; D000596:Amino Acids / Q000235:genetics; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007555:Isoxazoles / Q000494:pharmacology; D051379:Mice; D008958:Models, Molecular; D050506:Mutant Chimeric Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009865:Oocytes / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C508388:1-(5-chloro-2,4-dimethoxyphenyl)-3-(5-methylisoxazol-3-yl)urea; D000596:Amino Acids; C579167:Chrna7 protein, human; C579166:Chrna7 protein, mouse; C579165:Chrna7 protein, rat; D007555:Isoxazoles; D050506:Mutant Chimeric Proteins; D010671:Phenylurea Compounds; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor
references.citation: J Biol Chem. 1998 Feb 6;273(6):3314-9
references.pmid: 9452448
references.citation: Biochemistry. 2007 Sep 11;46(36):10296-307
references.pmid: 17685589
references.citation: Mol Pharmacol. 1994 Feb;45(2):212-20
references.pmid: 7509438
references.citation: J Comput Chem. 2007 Apr 30;28(6):1145-52
references.pmid: 17274016
references.citation: Mol Pharmacol. 2007 Sep;72(3):715-24
references.pmid: 17565004
references.citation: Nature. 2003 Jun 26;423(6943):949-55
references.pmid: 12827192
references.citation: Biochem Pharmacol. 2007 Oct 15;74(8):1155-63
references.pmid: 17707779
references.citation: Nature. 1997 Sep 25;389(6649):385-9
references.pmid: 9311780
references.citation: Nature. 2006 Nov 23;444(7118):486-9
references.pmid: 17108970
references.citation: J Neurobiol. 2002 Dec;53(4):447-56
references.pmid: 12436412
references.citation: J Mol Biol. 1965 May;12:88-118
references.pmid: 14343300
references.citation: Proc Natl Acad Sci U S A. 1996 Mar 5;93(5):1853-8
references.pmid: 8700848
references.citation: Biochem Pharmacol. 2007 Oct 15;74(8):1092-101
references.pmid: 17662959
references.citation: Biochem Soc Trans. 2003 Aug;31(Pt 4):869-74
references.pmid: 12887324
references.citation: J Mol Model. 2006 Feb;12(3):366-72
references.pmid: 16372175
references.citation: Eur J Biochem. 1993 Sep 1;216(2):671-7
references.pmid: 8375401
references.citation: Neuropharmacology. 2006 Feb;50(2):174-81
references.pmid: 16225893
references.citation: J Mol Biol. 2007 Jun 15;369(4):895-901
references.pmid: 17481657
references.citation: FEBS Lett. 2006 Feb 20;580(5):1447-50
references.pmid: 16460734
references.citation: Science. 1991 Oct 18;254(5030):432-7
references.pmid: 1718042
references.citation: Trends Neurosci. 2004 Jun;27(6):329-36
references.pmid: 15165737
references.citation: Trends Mol Med. 2008 Mar;14(3):93-102
references.pmid: 18262468
references.citation: Br J Pharmacol. 2007 Oct;152(4):501-12
references.pmid: 17721553
references.citation: Trends Neurosci. 1995 Mar;18(3):121-7
references.pmid: 7754520
references.citation: Biophys J. 2005 Jun;88(6):3954-65
references.pmid: 15805177
references.citation: Mol Pharmacol. 2007 Feb;71(2):389-97
references.pmid: 17065235
references.citation: J Mol Biol. 2005 Mar 4;346(4):967-89
references.pmid: 15701510
references.citation: J Med Chem. 2005 Jul 28;48(15):4705-45
references.pmid: 16033252
references.citation: J Neurosci. 2005 Apr 27;25(17):4396-405
references.pmid: 15858066
references.citation: Proc Natl Acad Sci U S A. 2007 May 8;104(19):8059-64
references.pmid: 17470817
references.citation: Nature. 1995 Jan 5;373(6509):37-43
references.pmid: 7800037
references.citation: Biochem Pharmacol. 2007 Oct 15;74(8):1182-91
references.pmid: 17714691
references.citation: Science. 2005 Jun 3;308(5727):1424-8
references.pmid: 15933191
references.citation: J Pharmacol Exp Ther. 2007 Oct;323(1):294-307
references.pmid: 17625074
references.citation: Proc Natl Acad Sci U S A. 2006 Nov 7;103(45):16965-70
references.pmid: 17077146
references.citation: Neuron. 1990 Dec;5(6):847-56
references.pmid: 1702646
references.citation: J Biol Chem. 2004 Apr 23;279(17):17640-9
references.pmid: 14761946
references.citation: Nature. 1993 Dec 2;366(6454):479-83
references.pmid: 8247158
references.citation: J Mol Biol. 2006 Jan 13;355(2):310-24
references.pmid: 16307758
references.citation: Behav Brain Res. 2000 Aug;113(1-2):43-56
references.pmid: 10942031
references.citation: J Pharmacol Exp Ther. 2006 Sep;318(3):1108-17
references.pmid: 16738207