Neuronal nicotinic receptor β2 and β4 subunits confer large differences in agonist binding affinity

被引:158
作者
Parker, MJ [1 ]
Beck, A [1 ]
Luetje, CW [1 ]
机构
[1] Univ Miami, Sch Med, Dept Mol & Cellular Pharmacol, Miami, FL 33101 USA
关键词
D O I
10.1124/mol.54.6.1132
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
We used equilibrium binding analysis to characterize the agonist binding properties of six different rat neuronal nicotinic receptor subunit combinations expressed in Xenopus laevis oocytes. The alpha 4 beta 2 receptor bound [H-3]cytisine with a K-dapp of 0.74 +/- 0.14 nM. The rank order of K-iapp values of additional nicotinic ligands, determined in competition assays, was cytisine < nicotine < acetylcholine < carbachol < curare. These pharmacological properties of alpha 4 beta 2 expressed in oocytes are comparable to published values for the high affinity cytisine binding site in rat brain (alpha 4 beta 2), demonstrating that rat neuronal nicotinic receptors expressed in X. laevis oocytes display appropriate pharmacological properties. Use of [H-3]epibatidine allowed detailed characterization of multiple neuronal nicotinic receptor subunit combinations. K-dapp values for [H-3]epibatidine binding were 10 pM for alpha 2 beta 2, 87 pM for alpha 2 beta 4, 14 pM for alpha 3 beta 2, 300 pM for alpha 3 beta 4, 30 pM for alpha 4 beta 2, and 85 pM for alpha 4 beta 4. Affinities for six additional agonists (acetylcholine, anabasine, cytisine, 1,1-dimethyl-4-phenylpiperazinium, lobeline, and nicotine) were determined in competition assays. The beta 2-containing receptors had consistently higher affinities for these agonists than did beta 4-containing receptors. Particularly striking examples are the affinities displayed by alpha 2 beta 2 and alpha 2 beta 4, which differ in 1,1-dimethyl-4-phenylpiperazinium, nicotine, lobeline, and acetylcholine affinity by 120-, 86-, 85-, and 61-fold, respectively. Although smaller differences in affinity could be ascribed to different alpha subunits, the major factor in determining agonist affinity was the nature of the beta subunit.
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页码:1132 / 1139
页数:8
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