Molecular blueprint of allosteric binding sites in a homologue of the agonist-binding domain of the α7 nicotinic acetylcholine receptor.
The α7 nicotinic acetylcholine receptor (nAChR) belongs to the family of pentameric ligand-gated ion channels and is involved in fast synaptic signaling. In this study, we take advantage of a recently identified chimera of the extracellular domain of the native α7 nicotinic acetylcholine receptor and acetylcholine binding protein, termed α7-AChBP. This chimeric receptor was used to conduct an innovative fragment-library screening in combination with X-ray crystallography to identify allosteric binding sites. One allosteric site is surface-exposed and is located near the N-terminal α-helix of the extracellular domain. Ligand binding at this site causes a conformational change of the α-helix as the fragment wedges between the α-helix and a loop homologous to the main immunogenic region of the muscle α1 subunit. A second site is located in the vestibule of the receptor, in a preexisting intrasubunit pocket opposite the agonist binding site and corresponds to a previously identified site involved in positive allosteric modulation of the bacterial homolog ELIC. A third site is located at a pocket right below the agonist binding site. Using electrophysiological recordings on the human α7 nAChR we demonstrate that the identified fragments, which bind at these sites, can modulate receptor activation. This work presents a structural framework for different allosteric binding sites in the α7 nAChR and paves the way for future development of novel allosteric modulators with therapeutic potential.
Laboratory of Structural Neurobiology, Katholieke Universiteit Leuven, Leuven B-3000, Belgium;
Radovan
R
Spurny
Laboratory of Structural Neurobiology, Katholieke Universiteit Leuven, Leuven B-3000, Belgium;
Sarah
S
Debaveye
Laboratory of Structural Neurobiology, Katholieke Universiteit Leuven, Leuven B-3000, Belgium;
Ana
A
Farinha
Neurosciences and.
Ken
K
Veys
Discovery Sciences, Janssen Research and Development, Beerse B-2340, Belgium;
Ann M
AM
Vos
Beactica AB, SE-752 37 Uppsala, Sweden;
Thomas
T
Gossas
Translational Drug Discovery Group, University of Sussex, BN1 9QJ Brighton, United Kingdom;
John
J
Atack
HiQscreen,1222 Vésenaz, Geneva, Switzerland; and.
Sonia
S
Bertrand
HiQscreen,1222 Vésenaz, Geneva, Switzerland; and.
Daniel
D
Bertrand
Beactica AB, SE-752 37 Uppsala, Sweden; Department of Chemistry, Uppsala Biomedical Center, Uppsala University, SE-751 23 Uppsala, Sweden.
U Helena
UH
Danielson
Discovery Sciences, Janssen Research and Development, Beerse B-2340, Belgium;
Gary
G
Tresadern
Laboratory of Structural Neurobiology, Katholieke Universiteit Leuven, Leuven B-3000, Belgium; chris.ulens@med.kuleuven.be.
Chris
C
Ulens
D000494:Allosteric Regulation; D000495:Allosteric Site; D000818:Animals; D002244:Carbon / Q000737:chemistry; D018360:Crystallography, X-Ray; D006801:Humans; D058446:Ligand-Gated Ion Channels / Q000378:metabolism; D008024:Ligands; D008958:Models, Molecular; D016296:Mutagenesis; D009865:Oocytes / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011978:Receptors, Nicotinic / Q000378:metabolism; D020349:Surface Plasmon Resonance; D014101:Torpedo; D014961:X-Ray Diffraction; D014981:Xenopus; D064569:alpha7 Nicotinic Acetylcholine Receptor / Q000378:metabolism*
D058446:Ligand-Gated Ion Channels; D008024:Ligands; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor; D002244:Carbon
Cys-loop receptor; X-ray crystallography; allosteric modulator; fragment screen; ligand-gated ion channel