The novel ?7?2-nicotinic acetylcholine receptor subtype is expressed in mouse and human basal forebrain: biochemical and pharmacological characterization.

ABSTRACT: We examined ?7?2-nicotinic acetylcholine receptor (?7?2-nAChR) expression in mammalian brain and compared pharmacological profiles of homomeric ?7-nAChRs and ?7?2-nAChRs. ?-Bungarotoxin affinity purification or immunoprecipitation with anti-?7 subunit antibodies (Abs) was used to isolate nAChRs containing ?7 subunits from mouse or human brain samples. ?7?2-nAChRs were detected in forebrain, but not other tested regions, from both species, based on Western blot analysis of isolates using ?2 subunit-specific Abs. Ab specificity was confirmed in control studies using subunit-null mutant mice or cell lines heterologously expressing specific human nAChR subtypes and subunits. Functional expression in Xenopus oocytes of concatenated pentameric (?7)5-, (?7)4(?2)1-, and (?7)3(?2)2-nAChRs was confirmed using two-electrode voltage clamp recording of responses to nicotinic ligands. Importantly, pharmacological profiles were indistinguishable for concatenated (?7)5-nAChRs or for homomeric ?7-nAChRs constituted from unlinked ?7 subunits. Pharmacological profiles were similar for (?7)5-, (?7)4(?2)1-, and (?7)3(?2)2-nAChRs except for diminished efficacy of nicotine (normalized to acetylcholine efficacy) at ?7?2- versus ?7-nAChRs. This study represents the first direct confirmation of ?7?2-nAChR expression in human and mouse forebrain, supporting previous mouse studies that suggested relevance of ?7?2-nAChRs in Alzheimer disease etiopathogenesis. These data also indicate that ?7?2-nAChR subunit isoforms with different ?7/?2 subunit ratios have similar pharmacological profiles to each other and to ?7 homopentameric nAChRs. This supports the hypothesis that ?7?2-nAChR agonist activation predominantly or entirely reflects binding to ?7/?7 subunit interface sites.

SUBMITTER: Moretti M 

PROVIDER: S-EPMC4152907 | biostudies-other | 2014 Sep

REPOSITORIES: biostudies-other