Function of Human α3β4α5 Nicotinic Acetylcholine Receptors Is Reduced by the α5(D398N) Variant

• Published in: The Journal of biological chemistry 2012-07, Vol.287 (30), p.25151-25162
• Main Authors: George, Andrew A., Lucero, Linda M., Damaj, M. Imad, Lukas, Ronald J., Chen, Xiangning, Whiteaker, Paul
• Format: Article
• Language: English
• Subjects: Amino Acid Substitution; Animals; Genetic Polymorphism; Genome-Wide Association Study; Humans; Ion Channels; Molecular Pharmacology; Multiprotein Complexes - genetics; Multiprotein Complexes - metabolism; Mutation, Missense; Neurobiology; Nicotinic Acetylcholine Receptors; Oocytes; Pharmacology; Polymorphism, Genetic; Protein Subunits - genetics; Protein Subunits - metabolism; Receptor Function; Receptors, Nicotinic - genetics; Receptors, Nicotinic - metabolism; Signal Transduction - physiology; Xenopus laevis; α5(D398N)
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.379339

Background: The naturally occurring α5(D398N) variant alters smoking behavior, but functional differences have not been detected between α3β4α5 nAChR harboring these variants. Results: ACh-induced α3β4α5 nAChR function is lower when α5(Asn-398) substitutes for α5(Asp-398). Conclusion: The α5 variant-induced change in α3β4α5 nAChR function may underlie some of the phenotypic changes associated with this polymorphism. Significance: α3β4α5 nAChR function may be a useful target for smoking cessation pharmacotherapies. Genome-wide studies have strongly associated a non-synonymous polymorphism (rs16969968) that changes the 398th amino acid in the nAChR α5 subunit from aspartic acid to asparagine (D398N), with greater risk for increased nicotine consumption. We have used a pentameric concatemer approach to express defined and consistent populations of α3β4α5 nAChR in Xenopus oocytes. α5(Asn-398; risk) variant incorporation reduces ACh-evoked function compared with inclusion of the common α5(Asp-398) variant without altering agonist or antagonist potencies. Unlinked α3, β4, and α5 subunits assemble to form a uniform nAChR population with pharmacological properties matching those of concatemeric α3β4* nAChRs. α5 subunit incorporation reduces α3β4* nAChR function after coinjection with unlinked α3 and β4 subunits but increases that of α3β4α5 versus α3β4-only concatemers. α5 subunit incorporation into α3β4* nAChR also alters the relative efficacies of competitive agonists and changes the potency of the non-competitive antagonist mecamylamine. Additional observations indicated that in the absence of α5 subunits, free α3 and β4 subunits form at least two further subtypes. The pharmacological profiles of these free subunit α3β4-only subtypes are dissimilar both to each other and to those of α3β4α5 nAChR. The α5 variant-induced change in α3β4α5 nAChR function may underlie some of the phenotypic changes associated with this polymorphism.