title: (-)-Reboxetine inhibits muscle nicotinic acetylcholine receptors by interacting with luminal and non-luminal sites.
abstract: The interaction of (-)-reboxetine, a non-tricyclic norepinephrine selective reuptake inhibitor, with muscle-type nicotinic acetylcholine receptors (AChRs) in different conformational states was studied by functional and structural approaches. The results established that (-)-reboxetine: (a) inhibits (±)-epibatidine-induced Ca(2+) influx in human (h) muscle embryonic (hα1β1γδ) and adult (hα1β1εδ) AChRs in a non-competitive manner and with potencies IC50=3.86±0.49 and 1.92±0.48 μM, respectively, (b) binds to the [(3)H]TCP site with ~13-fold higher affinity when the Torpedo AChR is in the desensitized state compared to the resting state, (c) enhances [(3)H]cytisine binding to the resting but activatableTorpedo AChR but not to the desensitized AChR, suggesting desensitizing properties, (d) overlaps the PCP luminal site located between rings 6' and 13' in the Torpedo but not human muscle AChRs. In silico mutation results indicate that ring 9' is the minimum structural component for (-)-reboxetine binding, and (e) interacts to non-luminal sites located within the transmembrane segments from the Torpedo AChR γ subunit, and at the α1/ε transmembrane interface from the adult muscle AChR. In conclusion, (-)-reboxetine non-competitively inhibits muscle AChRs by binding to the TCP luminal site and by inducing receptor desensitization (maybe by interacting with non-luminal sites), a mechanism that is shared by tricyclic antidepressants.
authors.affiliation: Department of Medical Education, California Northstate University College of Medicine, Elk Grove, CA, USA. Electronic address: hugo.arias@cnucom.org.
authors.forename: Hugo R
authors.initials: HR
authors.lastname: Arias
authors.forename: Marcelo O
authors.initials: MO
authors.lastname: Ortells
authors.forename: Dominik
authors.initials: D
authors.lastname: Feuerbach
mesh_terms: D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000818:Animals; D001665:Binding Sites; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006801:Humans; D017136:Ion Transport; D062105:Molecular Docking Simulation; D056004:Molecular Dynamics Simulation; D009025:Morpholines / Q000494:pharmacology*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011725:Pyridines / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011869:Radioligand Assay; D000077593:Reboxetine; D011978:Receptors, Nicotinic / Q000187:drug effects* / Q000378:metabolism; D014101:Torpedo
chemical_list: D018759:Adrenergic Uptake Inhibitors; D019086:Bridged Bicyclo Compounds, Heterocyclic; D009025:Morpholines; D011725:Pyridines; D011978:Receptors, Nicotinic; D000077593:Reboxetine; C082748:epibatidine; D002118:Calcium
keywords: (−)-R,R-([2-[α[2-ethoxyphenoxy]benzyl]-morpholine); (−)-reboxetine; AChR; Antidepressants; BS; CCh; Conformational states; DMEM; EC(50); FBS; Hill coefficient; IC(50); K(i); NCA; NSRI; Nicotinic acetylcholine receptors; Norepinephrine selective reuptake inhibitor; PCP; RMSD; RT; Reboxetine; TCAs; [(3)H]TCP; binding saline; carbamylcholine; dulbecco’s modified eagle medium; fetal bovine serum; inhibition constant; ligand concentration that inhibits 50% binding or ion flux; ligand concentration that produces 50% increase of binding; n(H); nicotinic acetylcholine receptor; non-competitive antagonist; norepinephrine selective reuptake inhibitor; phencyclidine; piperidyl-3, 4-3H(N)]-(N-(1-(2 thienyl)cyclohexyl)-3, 4-piperidine; room temperature; root mean square deviation; tricyclic antidepressants; α-BTx; α-bungarotoxin