α4β2 nicotinic receptors with high and low acetylcholine sensitivity:: Pharmacology, stoichiometry, and sensitivity to long-term exposure to nicotine
α4β2 nicotinic receptors with high and low acetylcholine sensitivity:: Pharmacology, stoichiometry, and sensitivity to long-term exposure to nicotine
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DOI：
10.1124/mol.106.023044
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发表时间：
2006-08-01
影响因子：
3.6
通讯作者：
Bermudez, Isabel
中科院分区：
文献类型：
--
作者：
Moroni, Mirko;Zwart, Ruud;Bermudez, Isabel
异源表达的α4和β2烟碱乙酰胆碱受体（nAChR）亚基组装成对乙酰胆碱（ACh）具有高（HS）和低（LS）敏感性的受体；它们的相对比例取决于 alpha 4 与 beta 2 的比率。在这项研究中，单相 ACh 浓度-反应曲线证明，注射 1:10 α4/β2 亚基 cDNA 比例的卵母细胞有利于 HS α4β2 nAChR 的表达，而注射 10:1 cDNA 比例的卵母细胞有利于 LS α4β2 受体的表达。化学计量是根据 α 4 和 β 2 第二个跨膜结构域 9' 位置上的 Leu 突变为 Thr 引起的 ACh EC50 值的变化推断的。1:10 注射比例产生 (α 4)(2)(β 2)(3) 化学计量，而 10:1 注射产生 (α 4)(3)(β(2))(2) 化学计量。激动剂皮巴替丁、3-[2(S)-氮杂环丁基甲氧基]吡啶 (A-85380)、5-乙氧基-间烟碱 (TC-2559)、金雀花碱和 3-Br-金雀花碱以及拮抗剂二氢-β-赤霉素和 d-筒箭毒碱对 HS 受体更有效。 TC-2559 对 HS 受体比 ACh 更有效，但对 LS 受体是部分激动剂。 Epibatidine 对 LS 受体比 ACh 更有效，并且是 HS 受体的部分激动剂。金雀花碱和5-卤代金雀花碱对LS受体具有中等功效，但对HS受体几乎没有功效。通过利用 ACh、TC-2559 和 5-I-金雀花碱的差异效应，我们评估了长期暴露于尼古丁对 cDNA 注射或人胚胎肾 293 细胞中组装的 α 4 β 2 受体微移植后非洲爪蟾卵母细胞中表达的 HS 和 LS 受体的影响。我们得出的结论是，尼古丁上调 HS α 4 β 2 受体，可能是通过影响受体的组装，而不是通过改变 LS α 4 β 2 nAChR 的功能状态。
alpha 4 and beta 2 nicotinic acetylcholine receptor ( nAChR) subunits expressed heterologously assemble into receptors with high (HS) and low (LS) sensitivity to acetylcholine (ACh); their relative proportions depend on the alpha 4 to beta 2 ratio. In this study, injection of oocytes with 1: 10 alpha 4/beta 2 subunit cDNA ratios favored expression of HS alpha 4 beta 2 nAChRs, as evidenced by monophasic ACh concentration-response curves, whereas injections with 10: 1 cDNA ratios favored expression of LS alpha 4 beta 2 receptors. The stoichiometry was inferred from the shifts in the ACh EC50 values caused by Leu to Thr mutations at position 9' of the second transmembrane domain of alpha 4 and beta 2. The 1: 10 injection ratio produced the (alpha 4)(2)(beta 2)(3) stoichiometry, whereas 10:1 injections produced the (alpha 4)(3)(beta(2))(2) stoichiometry. The agonists epibatidine, 3-[2(S)-azetidinylmethoxy]pyridine (A-85380), 5-ethoxy-metanicotine (TC-2559), cytisine, and 3-Br-cytisine and the antagonists dihydro-beta-erythroidine and d-tubocurarine were more potent at HS receptors. TC-2559 was more efficacious than ACh at HS receptors but was a partial agonist at LS receptors. Epibatidine was more efficacious than ACh at LS receptors and a partial agonist at HS receptors. Cytisine and 5-halogenated cytisines had moderate efficacy at LS receptors but had almost no efficacy at HS receptors. By exploiting the differential effects of ACh, TC-2559 and 5-I-cytisine we evaluated the effects of long-term exposure to nicotine on HS and LS receptors expressed in Xenopus laevis oocytes after cDNA injections or microtransplantation of alpha 4 beta 2 receptors assembled in human embryonic kidney 293 cells. We conclude that nicotine up-regulates HS alpha 4 beta 2 receptors, probably by influencing the assembly of receptors rather than by altering the functional state of LS alpha 4 beta 2 nAChRs.