LAUSR

ABSTRACT Several previous studies have demonstrated that the activity of neurotransmitters acting on ligand‐gated ion channels such as the nicotinic acetylcholine receptor (nAChR) can be altered by compounds binding to allosteric modulatory sites. In the case of &agr;7 nAChRs, both positive and negative allosteric modulators (PAMs and NAMs) have been identified and have attracted considerable interest. A recent study, employing revised structural models of the transmembrane domain of the &agr;7 nAChR in closed and open conformations, has provided support for an inter‐subunit transmembrane allosteric binding site (Newcombe et al 2017). In the present study, we have performed virtual screening of the DrugBank database using pharmacophore queries that were based on the predicted binding mode of PAMs to &agr;7 nAChR structural models. A total of 81 compounds were identified in the DrugBank database, of which the 25 highest‐ranked hits corresponded to one of four previously‐identified therapeutic compound groups (carbonic anhydrase inhibitors, cyclin‐dependent kinase inhibitors, diuretics targeting the Na+‐K+‐Cl‐ cotransporter, and fluoroquinolone antibiotics targeting DNA gyrase). The top‐ranked compound from each of these four groups (DB04763, DB08122, furosemide and pefloxacin, respectively) was tested for its effects on human &agr;7 nAChR expressed in Xenopus oocytes using two‐electrode voltage‐clamp electrophysiology. These studies, conducted with wild‐type, mutant and chimeric receptors, resulted in all four compounds exerting allosteric modulatory effects. While DB04763, DB08122 and pefloxacin were antagonists, furosemide potentiated ACh responses. Our findings, supported by docking studies, are consistent with these compounds acting as PAMs and NAMs of the &agr;7 nAChR via interaction with a transmembrane site. HIGHLIGHTSIdentification of &agr;7 nAChR positive and negative allosteric modulators.Furosemide is a positive allosteric modulator of &agr;7 nAChRs.DB04763, DB08122 and pefloxacin are negative allosteric modulators of &agr;7 nAChRs.Modulation of &agr;7 nAChRs by an allosteric transmembrane site.