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LY2087101 and dFBr share transmembrane binding sites in the (?4)3(?2)2 Nicotinic Acetylcholine Receptor.

ABSTRACT: Positive allosteric modulators (PAMs) of nicotinic acetylcholine receptors (nAChRs) have potential therapeutic application in neuropathologies associated with decrease in function or loss of nAChRs. In this study, we characterize the pharmacological interactions of the nAChRs PAM, LY2087101, with the ?4?2 nAChR using mutational and computational analyses. LY2087101 potentiated ACh-induced currents of low-sensitivity (?4)3(?2)2 and high-sensitivity (?4)2(?2)3 nAChRs with similar potencies albeit to a different maximum potentiation (potentiation I max ?=?~840 and 450%, respectively). Amino acid substitutions within the ?4 subunit transmembrane domain [e.g. ?4Leu256 and ?4Leu260 within the transmembrane helix 1 (TM1); ?4Phe316 within the TM3; and ?4Gly613 within TM4] significantly reduced LY2087101 potentiation of (?4)3(?2)2 nAChR. The locations of these amino acid residues and LY2087101 computational docking analyses identify two LY2087101 binding sites: an intrasubunit binding site within the transmembrane helix bundle of ?4 subunit at the level of ?4Leu260/?4Phe316 and intersubunit binding site at the ?4:?4 subunit interface at the level of ?4Leu256/?4Ile315 with both sites extending toward the extracellular end of the transmembrane domain. We also show that desformylflustrabromine (dFBr) binds to these two sites identified for LY2087101. These results provide structural information that are pertinent to structure-based design of nAChR allosteric modulators.

SUBMITTER: Deba F

PROVIDER: S-EPMC5775429 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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LY2087101 and dFBr share transmembrane binding sites in the (α4)3(β2)2 Nicotinic Acetylcholine Receptor.

Deba Farah F Ali Hamed I HI Tairu Abisola A Ramos Kara K Ali Jihad J Hamouda Ayman K AK

Scientific reports 20180119 1

Positive allosteric modulators (PAMs) of nicotinic acetylcholine receptors (nAChRs) have potential therapeutic application in neuropathologies associated with decrease in function or loss of nAChRs. In this study, we characterize the pharmacological interactions of the nAChRs PAM, LY2087101, with the α4β2 nAChR using mutational and computational analyses. LY2087101 potentiated ACh-induced currents of low-sensitivity (α4)3(β2)2 and high-sensitivity (α4)2(β2)3 nAChRs with similar potencies albeit ...[more]

PMID: 29352227

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Project description:Photoreactive derivatives of the general anesthetic etomidate have been developed to identify their binding sites in ?-aminobutyric acid, type A and nicotinic acetylcholine receptors. One such drug, [(3)H]TDBzl-etomidate (4-[3-(trifluoromethyl)-3H-diazirin-3-yl]benzyl-[(3)H]1-(1-phenylethyl)-1H-imidazole-5-carboxylate), acts as a positive allosteric potentiator of Torpedo nACh receptor (nAChR) and binds to a novel site in the transmembrane domain at the ?-? subunit interface. To extend our understanding of the locations of allosteric modulator binding sites in the nAChR, we now characterize the interactions of a second aryl diazirine etomidate derivative, TFD-etomidate (ethyl-1-(1-(4-(3-trifluoromethyl)-3H-diazirin-3-yl)phenylethyl)-1H-imidazole-5-carboxylate). TFD-etomidate inhibited acetylcholine-induced currents with an IC(50) = 4 ?M, whereas it inhibited the binding of [(3)H]phencyclidine to the Torpedo nAChR ion channel in the resting and desensitized states with IC(50) values of 2.5 and 0.7 mm, respectively. Similar to [(3)H]TDBzl-etomidate, [(3)H]TFD-etomidate bound to a site at the ?-? subunit interface, photolabeling ?M2-10 (?Ser-252) and ?Met-295 and ?Met-299 within ?M3, and to a site in the ion channel, photolabeling amino acids within each subunit M2 helix that line the lumen of the ion channel. In addition, [(3)H]TFD-etomidate photolabeled in an agonist-dependent manner amino acids within the ? subunit M2-M3 loop (?Ile-288) and the ? subunit transmembrane helix bundle (?Phe-232 and ?Cys-236 within ?M1). The fact that TFD-etomidate does not compete with ion channel blockers at concentrations that inhibit acetylcholine responses indicates that binding to sites at the ?-? subunit interface and/or within ? subunit helix bundle mediates the TFD-etomidate inhibitory effect. These results also suggest that the ?-? subunit interface is a binding site for Torpedo nAChR negative allosteric modulators (TFD-etomidate) and for positive modulators (TDBzl-etomidate).

Dataset Information

LY2087101 and dFBr share transmembrane binding sites in the (?4)3(?2)2 Nicotinic Acetylcholine Receptor.

Publications

LY2087101 and dFBr share transmembrane binding sites in the (α4)3(β2)2 Nicotinic Acetylcholine Receptor.

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