High affinity binding of epibatidine to serotonin type 3 receptors
High affinity binding of epibatidine to serotonin type 3 receptors
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DOI：
10.1074/jbc.m703672200
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发表时间：
2008-04-11
影响因子：
4.8
通讯作者：
Green, William N.
中科院分区：
文献类型：
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作者：
Drisdel, Renaldo C.;Sharp, Douglas;Green, William N.
Epibatidine 和 mecamylamine 是广泛用于中枢和周围神经系统烟碱乙酰胆碱受体 (nAChR) 研究的配体。在本研究中，我们发现尼古丁仅阻断 75% 的 I-125-epibatidine 与大鼠脑膜的结合，而 5-羟色胺 3 型受体 (5-HT(3)Rs) 特异性配体则阻断其余 25%。 I-125-Epibatidine 以高亲和力与 N1E-115 细胞的天然 5-HT(3)R 以及 HEK 细胞中表达的仅由 5-HT3A 亚基组成的受体结合。在这些细胞中，血清素、5-HT3R 特异性拮抗剂 MDL72222 和 5-HT3R 激动剂氯苯基双胍很容易与 I-125-epibatidine 竞争与 5-HT(3)R 的结合。尼古丁是 I-125-epibatidine 与 5-HT(3)R 结合的较差竞争者。然而，非竞争性 nAChR 拮抗剂美加明可作为 I-125-epibatidine 与 5-HT(3)R 结合的有效竞争性抑制剂。 Epibatidine 抑制神经母细胞瘤细胞系中内源性 5-HT(3)R 和 HEK 细胞中表达的 5-HT(3)AR 以竞争性方式介导的血清素诱导电流。我们的结果表明，5-HT(3)R 是大脑中先前未表征的高亲和力皮巴替丁结合位点，并表明皮巴替丁和美加明可作为 5-HT3R 拮抗剂。先前依赖于皮巴替丁和美加明作为 nAChR 特异性配体的研究，特别是对皮巴替丁镇痛特性的研究，可能需要重新解释 5-HT(3)Rs 的潜在作用。
Epibatidine and mecamylamine are ligands used widely in the study of nicotinic acetylcholine receptors (nAChRs) in the central and peripheral nervous systems. In the present study, we find that nicotine blocks only 75% of I-125-epibatidine binding to rat brain membranes, whereas ligands specific for serotonin type 3 receptors (5-HT(3)Rs) block the remaining 25%. I-125-Epibatidine binds with a high affinity to native 5-HT(3)Rs of N1E-115 cells and to receptors composed of only 5-HT3A subunits expressed in HEK cells. In these cells, serotonin, the 5-HT3R-specific antagonist MDL72222, and the 5-HT3R agonist chlorophenylbiguanide readily competed with I-125-epibatidine binding to 5-HT(3)Rs. Nicotine was a poor competitor for I-125-epibatidine binding to 5-HT(3)Rs. However, the noncompetitive nAChR antagonist mecamylamine acted as a potent competitive inhibitor of I-125-epibatidine binding to 5-HT(3)Rs. Epibatidine inhibited serotonin-induced currents mediated by endogenous 5-HT(3)Rs in neuroblastoma cell lines and 5-HT(3)ARs expressed in HEK cells in a competitive manner. Our results demonstrate that 5-HT(3)Rs are previously uncharacterized high affinity epibatidine binding sites in the brain and indicate that epibatidine and mecamylamine act as 5-HT3R antagonists. Previous studies that depended on epibatidine and mecamylamine as nAChR-specific ligands, in particular studies of analgesic properties of epibatidine, may need to be reinterpreted with respect to the potential role of 5-HT(3)Rs.