Abstract
We examined α7β2-nicotinic acetylcholine receptor (α7β2-nAChR) expression in mammalian brain and compared pharmacological profiles of homomeric α7-nAChRs and α7β2-nAChRs. α-Bungarotoxin affinity purification or immunoprecipitation with anti-α7 subunit antibodies (Abs) was used to isolate nAChRs containing α7 subunits from mouse or human brain samples. α7β2-nAChRs were detected in forebrain, but not other tested regions, from both species, based on Western blot analysis of isolates using β2 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 (α7)5-, (α7)4(β2)1-, and (α7)3(β2)2-nAChRs was confirmed using two-electrode voltage clamp recording of responses to nicotinic ligands. Importantly, pharmacological profiles were indistinguishable for concatenated (α7)5-nAChRs or for homomeric α7-nAChRs constituted from unlinked α7 subunits. Pharmacological profiles were similar for (α7)5-, (α7)4(β2)1-, and (α7)3(β2)2-nAChRs except for diminished efficacy of nicotine (normalized to acetylcholine efficacy) at α7β2- versus α7-nAChRs. This study represents the first direct confirmation of α7β2-nAChR expression in human and mouse forebrain, supporting previous mouse studies that suggested relevance of α7β2-nAChRs in Alzheimer disease etiopathogenesis. These data also indicate that α7β2-nAChR subunit isoforms with different α7/β2 subunit ratios have similar pharmacological profiles to each other and to α7 homopentameric nAChRs. This supports the hypothesis that α7β2-nAChR agonist activation predominantly or entirely reflects binding to α7/α7 subunit interface sites.
Footnotes
- Received April 22, 2014.
- Accepted July 7, 2014.
M.M., M.Z., and A.A.G. contributed equally to this work; and P.W. and C.G. contributed equally to this work and are joint corresponding authors.
This research was supported by the European Union Seventh Framework Programme [Grant HEALTH-F2-2008-20208 (to C.G. and M.Z.)], CNR Research Project on Aging, Regione Lombardia Project NUTEC [Grant 30263049], Italian Ministry of Health [Grant RF2009-1549619 (to M.Z.)], and the National Institutes of Health National Institute on Drug Abuse [Grant R21-DA026627], and Barrow Neurologic Foundation (to P.W.). The Newcastle Brain Tissue Resource is supported by the Research Councils UK Medical Research Council [Grant G0400074], National Institute for Health Research Newcastle Biomedical Research Centre, Newcastle upon Tyne National Health Service Foundation Trust, Newcastle University, and the Alzheimer’s Society and Alzheimer’s Research Trust [Brains for Dementia Research Project].
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- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
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