Acetylcholine-Binding Protein Engineered to Mimic the α4-α4 Binding Pocket in α4β2 Nicotinic Acetylcholine Receptors Reveals Interface Specific Interactions Important for Binding and Activity

TY - JOUR

T1 - Acetylcholine-Binding Protein Engineered to Mimic the α4-α4 Binding Pocket in α4β2 Nicotinic Acetylcholine Receptors Reveals Interface Specific Interactions Important for Binding and Activity

AU - Shahsavar, Azadeh

AU - Ahring, Philip K

AU - Olsen, Jeppe A

AU - Krintel, Christian

AU - Kastrup, Jette S

AU - Balle, Thomas

AU - Gajhede, Michael

N1 - Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

PY - 2015/10/1

Y1 - 2015/10/1

N2 - Neuronal α4β2 nicotinic acetylcholine receptors are attractive drug targets for psychiatric and neurodegenerative disorders and smoking cessation AIDS. Recently, a third agonist binding site between two a4 subunits in the (α4)3(β2)2 receptor subpopulation was discovered. In particular, three residues, H142, Q150, and T152, were demonstrated to be involved in the distinct pharmacology of the α 4- α 4 versus α 4- β 2 binding sites. To obtain insight into the three-dimensional structure of the a4-a4 binding site, a surrogate protein reproducing α 4- α 4 binding characteristics was constructed by introduction of three point mutations, R104H, L112Q, and M114T, into the binding pocket of Lymnaea stagnalis acetylcholine-binding protein (Ls-AChBP). Cocrystallization with two agonists possessing distinct pharmacologic profiles, NS3920 [1-(6-bromopyridin-3-yl)-1,4-diazepane] and NS3573 [1-(5-ethoxypyridin-3-yl)-1,4-diazepane], highlights the roles of the three residues in determining binding affinities and functional properties of ligands at the a4-a4 interface. Confirmed by mutational studies, our structures suggest a unique ligandspecific role of residue H142 on the a4 subunit. In the cocrystal structure of the mutated Ls-AChBP with the high-efficacy ligand NS3920, the corresponding histidine forms an intersubunit bridge that reinforces the ligand-mediated interactions between subunits. The structures further reveal that the binding site residues gain different and ligand-dependent interactions that could not be predicted based on wild-type Ls-AChBP structures in complex with the same agonists. The results show that an unprecedented correlation between binding in engineered AChBPs and functional receptors can be obtained and provide new opportunities for structure-based design of drugs targeting specific nicotinic acetylcholine receptor interfaces.

AB - Neuronal α4β2 nicotinic acetylcholine receptors are attractive drug targets for psychiatric and neurodegenerative disorders and smoking cessation AIDS. Recently, a third agonist binding site between two a4 subunits in the (α4)3(β2)2 receptor subpopulation was discovered. In particular, three residues, H142, Q150, and T152, were demonstrated to be involved in the distinct pharmacology of the α 4- α 4 versus α 4- β 2 binding sites. To obtain insight into the three-dimensional structure of the a4-a4 binding site, a surrogate protein reproducing α 4- α 4 binding characteristics was constructed by introduction of three point mutations, R104H, L112Q, and M114T, into the binding pocket of Lymnaea stagnalis acetylcholine-binding protein (Ls-AChBP). Cocrystallization with two agonists possessing distinct pharmacologic profiles, NS3920 [1-(6-bromopyridin-3-yl)-1,4-diazepane] and NS3573 [1-(5-ethoxypyridin-3-yl)-1,4-diazepane], highlights the roles of the three residues in determining binding affinities and functional properties of ligands at the a4-a4 interface. Confirmed by mutational studies, our structures suggest a unique ligandspecific role of residue H142 on the a4 subunit. In the cocrystal structure of the mutated Ls-AChBP with the high-efficacy ligand NS3920, the corresponding histidine forms an intersubunit bridge that reinforces the ligand-mediated interactions between subunits. The structures further reveal that the binding site residues gain different and ligand-dependent interactions that could not be predicted based on wild-type Ls-AChBP structures in complex with the same agonists. The results show that an unprecedented correlation between binding in engineered AChBPs and functional receptors can be obtained and provide new opportunities for structure-based design of drugs targeting specific nicotinic acetylcholine receptor interfaces.

KW - Animals

KW - Binding Sites

KW - Carrier Proteins

KW - Crystallography, X-Ray

KW - Dose-Response Relationship, Drug

KW - Female

KW - Humans

KW - Insects

KW - Molecular Mimicry

KW - Protein Binding

KW - Protein Engineering

KW - Protein Structure, Secondary

KW - Receptors, Nicotinic

KW - Xenopus laevis

U2 - 10.1124/mol.115.098061

DO - 10.1124/mol.115.098061

M3 - Journal article

C2 - 26180047

SN - 0026-895X

VL - 88

SP - 697

EP - 707

JO - Molecular Pharmacology

JF - Molecular Pharmacology

IS - 4

ER -