Non-equivalent Ligand Selectivity of Agonist Sites in (α4β2)2α4 Nicotinic Acetylcholine Receptors

Abstract

Background:The ␣4/␤2 and ␣4/␣4 interfaces of the (␣4␤2) 2 ␣4 nicotinic acetylcholine receptor house structurally different agonist sites. Results: Agonists of a certain size cannot bind the ␣4/␣4 interface, which decreases efficacy. Conclusion:The ability to bind all agonist sites in (␣4␤2) 2 ␣4 receptors critically influences agonist efficacy. Significance: The finding adds a new level of complexity to structural mechanisms governing agonist efficacy.

Engineered α4β2 nicotinic acetylcholine receptors as models for measuring agonist binding and effect at the orthosteric low-affinity α4–α4 interface

“…1B) which is known to be highly selective for the 2a:3b receptor . a4 H142 in the aea interface has been suggested to play an important role for this selectivity (Mazzaferro et al, 2014) and it is tempting to speculate that sazetidine-A has an even lower affinity for the aea interface than NS3573 despite its high affinity at aeb interfaces.…”

“…Hence, full activation of a 3a:2b receptor is achieved by ACh binding in three interfaces (two at aeb and one at aea interfaces) whereas the 2a:3b receptor is fully activated by binding to only two interfaces (the two aeb interfaces). The aea interface has been shown to be responsible for the distinct pharmacology of various agonists (Harpsøe et al, 2011;Marotta et al, 2014;Mazzaferro et al, 2014) and the actions of modulators, like Zn 2þ and NS9283 (Timmermann et al, 2012;Olsen et al, 2013Olsen et al, , 2014aGrupe et al, 2013).…”

Potentiation of a neuronal nicotinic receptor via pseudo-agonist site

“…A recent study based on the ability of NS9283 to potentiate concatemeric receptors with mutations in individual subunits suggested the subunits assembled in a counter-clockwise direction [50]. On the other hand, studies of the effects of single residue mutations [18,[51][52][53], and the ability of agonists to protect against covalent reaction of a methanethiosulfonate reagent with a substituted cysteine [54], suggested the subunits assembled in a clockwise direction. Thus to interpret our findings, we consider both scenarios of subunit assembly.…”

“…Single channel recordings from cells expressing receptors formed from linked subunits were made 72 to 96 hours post-transfection. Mutations were installed in cDNAs encoding unlinked and linked subunits and confirmed by sequencing as described previously [13,27,28].…”

Stoichiometry of the Heteromeric Nicotinic Receptors of the Renshaw Cell

“…Heteromeric nAChRs can associate multiple ␣ and ␤ subunits and in addition, for a given set of ␣ and ␤ subunits, can adopt two stoichiometries noted either 2␣:3␤ and 3␣:2␤ or A2B3 and A3B2 (Marotta et al, 2014). There is evidence for the presence in the CNS of the two stoichiometric variants of heteromeric nAChRs (Marks et al, 1999Shafaee et al, 1999;Gotti et al, 2007;DeDominicis et al, 2017). However, until now it has not been possible to assess the presence of a given variant at a specific synapse.…”