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Title

Interaction of alpha-conotoxin ImII and its analogs with nicotinic receptors and acetylcholine-binding proteins: additional binding sites on Torpedo receptor

Authors
Kasheverov, Igor E.
Zhmak, Maxim N.
Fish, Alexander
Rucktooa, Prakash
Khruschov, Alexey Yu
Osipov, Alexey V.
Ziganshin, Rustam H.
D'hoedt, Dieter
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Published in Journal of Neurochemistry. 2009, vol. 111, no. 4, p. 934-44
Abstract alpha-Conotoxins interact with nicotinic acetylcholine receptors (nAChRs) and acetylcholine-binding proteins (AChBPs) at the sites for agonists/competitive antagonists. alpha-Conotoxins blocking muscle-type or alpha7 nAChRs compete with alpha-bungarotoxin. However, alpha-conotoxin ImII, a close homolog of the alpha7 nAChR-targeting alpha-conotoxin ImI, blocked alpha7 and muscle nAChRs without displacing alpha-bungarotoxin (Ellison et al. 2003, 2004), suggesting binding at a different site. We synthesized alpha-conotoxin ImII, its ribbon isomer (ImIIiso), 'mutant' ImII(W10Y) and found similar potencies in blocking human alpha7 and muscle nAChRs in Xenopus oocytes. Both isomers displaced [(125)I]-alpha-bungarotoxin from human alpha7 nAChRs in the cell line GH(4)C(1) (IC(50) 17 and 23 microM, respectively) and from Lymnaea stagnalis and Aplysia californica AChBPs (IC(50) 2.0-9.0 microM). According to SPR measurements, both isomers bound to immobilized AChBPs and competed with AChBP for immobilized alpha-bungarotoxin (K(d) and IC(50) 2.5-8.2 microM). On Torpedo nAChR, alpha-conotoxin [(125)I]-ImII(W10Y) revealed specific binding (K(d) 1.5-6.1 microM) and could be displaced by alpha-conotoxin ImII, ImIIiso and ImII(W10Y) with IC(50) 2.7, 2.2 and 3.1 microM, respectively. As alpha-cobratoxin and alpha-conotoxin ImI displaced [(125)I]-ImII(W10Y) only at higher concentrations (IC(50)> or = 90 microM), our results indicate that alpha-conotoxin ImII and its congeners have an additional binding site on Torpedo nAChR distinct from the site for agonists/competitive antagonists.
Keywords Acetylcholine/pharmacologyAmino Acid SequenceAnimalsAplysiaBinding Sites/drug effects/physiologyBinding, Competitive/drug effectsBungarotoxins/metabolismCarrier Proteins/metabolismConotoxins/chemistry/metabolismDose-Response Relationship, DrugHumansInhibitory Concentration 50Iodine Isotopes/metabolismMolecular Sequence DataOocytesRadioligand Assay/methodsReceptors, Nicotinic/genetics/metabolismSerine EndopeptidasesSpectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methodsSurface Plasmon Resonance/methodsTorpedo/metabolismXenopus laevis
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PMID: 19712060
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KASHEVEROV, Igor E. et al. Interaction of alpha-conotoxin ImII and its analogs with nicotinic receptors and acetylcholine-binding proteins: additional binding sites on Torpedo receptor. In: Journal of Neurochemistry, 2009, vol. 111, n° 4, p. 934-44. https://archive-ouverte.unige.ch/unige:5107

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Deposited on : 2010-02-02

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