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Molecular interaction of α-conotoxin RgIA with the rat α9α10 nicotinic acetylcholine receptors

Molecular interaction of α-conotoxin RgIA with the rat α9α10 nicotinic acetylcholine receptors
Molecular interaction of α-conotoxin RgIA with the rat α9α10 nicotinic acetylcholine receptors

The α9α10 nicotinic acetylcholine receptor (nAChR) was first identified in the auditory system, where it mediates synaptic transmission between efferent olivocochlear cholinergic fibers and cochlea hair cells. This receptor gained further attention due to its potential role in chronic pain and breast and lung cancers. We previously showed that α-conotoxin (α-CTx) RgIA, one of the few α9α10 selective ligands identified to date, is 300-fold less potent on human versus rat α9α10 nAChR. This species difference was conferred by only one residue in the (-), rather than (+), binding region of the α9 subunit. In light of this unexpected discovery, we sought to determine other interacting residues with α-CTx RgIA. A previous molecular modeling study, based on the structure of the homologous molluscan acetylcholine-binding protein, predicted that RgIA interacts with three residues on the α9(+) face and two residues on the α10(-) face of the α9α10 nAChR. However, mutations of these residues had little or no effect on toxin block of the α9α10 nAChR. In contrast, mutations of homologous residues in the opposing nAChR subunits (α10 E197, P200 and α9 T61, D121) resulted in 19- to 1700-fold loss of toxin activity. Based on the crystal structure of the extracellular domain (ECD) of human α9 nAChR, we modeled the rat α9α10 ECD and its complexes with α-CTx RgIA and acetylcholine. Our data support the interaction of α-CTx RgIA at the α10/α9 rather than the α9/α10 nAChR subunit interface, and may facilitate the development of selective ligands with therapeutic potential.

0026-895X
855-864
Azam, Layla
02b57c90-a424-4614-8aac-28cf70ef988b
Papakyriakou, Athanasios
939bc8c9-1693-4530-9099-c55772b22f1d
Zouridakis, Marios
0e13ec68-376b-4baf-b6d1-44076843f9e4
Giastas, Petros
f2df660e-c366-4932-823a-1b1b78d39951
Tzartos, Socrates J.
e2eca147-25bf-4dbe-b058-9185a2d28ce7
McIntosh, J. Michael
bd2382de-ca43-4f0f-8378-ac19ab78f14c
Azam, Layla
02b57c90-a424-4614-8aac-28cf70ef988b
Papakyriakou, Athanasios
939bc8c9-1693-4530-9099-c55772b22f1d
Zouridakis, Marios
0e13ec68-376b-4baf-b6d1-44076843f9e4
Giastas, Petros
f2df660e-c366-4932-823a-1b1b78d39951
Tzartos, Socrates J.
e2eca147-25bf-4dbe-b058-9185a2d28ce7
McIntosh, J. Michael
bd2382de-ca43-4f0f-8378-ac19ab78f14c

Azam, Layla, Papakyriakou, Athanasios, Zouridakis, Marios, Giastas, Petros, Tzartos, Socrates J. and McIntosh, J. Michael (2015) Molecular interaction of α-conotoxin RgIA with the rat α9α10 nicotinic acetylcholine receptors. Molecular Pharmacology, 87 (5), 855-864. (doi:10.1124/mol.114.096511).

Record type: Article

Abstract

The α9α10 nicotinic acetylcholine receptor (nAChR) was first identified in the auditory system, where it mediates synaptic transmission between efferent olivocochlear cholinergic fibers and cochlea hair cells. This receptor gained further attention due to its potential role in chronic pain and breast and lung cancers. We previously showed that α-conotoxin (α-CTx) RgIA, one of the few α9α10 selective ligands identified to date, is 300-fold less potent on human versus rat α9α10 nAChR. This species difference was conferred by only one residue in the (-), rather than (+), binding region of the α9 subunit. In light of this unexpected discovery, we sought to determine other interacting residues with α-CTx RgIA. A previous molecular modeling study, based on the structure of the homologous molluscan acetylcholine-binding protein, predicted that RgIA interacts with three residues on the α9(+) face and two residues on the α10(-) face of the α9α10 nAChR. However, mutations of these residues had little or no effect on toxin block of the α9α10 nAChR. In contrast, mutations of homologous residues in the opposing nAChR subunits (α10 E197, P200 and α9 T61, D121) resulted in 19- to 1700-fold loss of toxin activity. Based on the crystal structure of the extracellular domain (ECD) of human α9 nAChR, we modeled the rat α9α10 ECD and its complexes with α-CTx RgIA and acetylcholine. Our data support the interaction of α-CTx RgIA at the α10/α9 rather than the α9/α10 nAChR subunit interface, and may facilitate the development of selective ligands with therapeutic potential.

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More information

Accepted/In Press date: 2 March 2015
e-pub ahead of print date: 26 March 2015
Published date: 1 May 2015

Identifiers

Local EPrints ID: 413406
URI: http://eprints.soton.ac.uk/id/eprint/413406
ISSN: 0026-895X
PURE UUID: cd67a14a-a8b9-4021-902b-c803600015c6
ORCID for Athanasios Papakyriakou: ORCID iD orcid.org/0000-0003-3931-6232

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Date deposited: 23 Aug 2017 16:32
Last modified: 26 Nov 2019 01:27

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