Neuronal nicotinic acetylcholine receptors containing α6 subunits (α6^*-nAChRs) show highly restricted distribution in midbrain neurons associated with pleasure, reward, and mood control, suggesting an important impact of α6^*-nAChRs in modulating mesolimbic functions. However, the function and pharmacology of α6^*-nAChRs remain poorly understood because of the lack of selective agonists for α6^*-nAChRs and the challenging heterologous expression of functional α6^*-nAChRs in mammalian cell lines. In particular, the α6 subunit is commonly co-expressed with α4^*-nAChRs in the midbrain, which masks α6^*-nAChR (without α4) function and pharmacology. In this study, we systematically profiled the pharmacology and function of α6^*-nAChRs and compared these properties with those of α4β2 nAChRs expressed in the same cell line. Heterologously expressed human α6/α3 chimeric subunits (α6 N-terminal domain joined with α3 trans-membrane domains and intracellular loops) with β2 and β3 subunits in the human SH-EP1 cell line (α6^*-nAChRs) were used. Patch-clamp whole-cell recordings were performed to measure these receptor-mediated currents. Functionally, the heterologously expressed α6^*-nAChRs exhibited excellent function and showed distinct nicotine-induced current responses, such as kinetics, inward rectification and recovery from desensitization, compared with α4β2-nAChRs. Pharmacologically, α6^*-nAChR was highly sensitive to the α6 subunit-selective antagonist α-conotoxin MII but had lower sensitivity to mecamylamine and dihydro-β-erythroidine. Nicotine and acetylcholine were found to be full agonists for α6^*-nAChRs, whereas epibatidine and cytisine were determined to be partial agonists. Heterologously expressed α6^*-nAChRs exhibited pharmacology and function distinct from those of α4β2-nAChRs, suggesting that α6^*-nAChRs may mediate different cholinergic signals. Our α6^*-nAChR expression system can be used as an excellent cell model for future investigations of α6^*-nAChR function and pharmacology.

中文翻译：

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在人上皮SH-EP1细胞系中异源表达的α6/α3β2β3-nAChRs和α4β2-nAChRs的药理和功能比较。

含有α6亚基（α6 ^* -nAChRs）的神经元烟碱型乙酰胆碱受体在中脑神经元中的分布受到极大限制，与愉悦，奖赏和情绪控制相关，这表明α6 ^* -nAChRs在调节中脑边缘功能方面具有重要作用。但是，该函数和α6的药理学^* -nAChRs仍知之甚少，因为缺乏用于α6选择性激动剂的^* -nAChRs和功能α6的挑战异源表达^*在哺乳动物细胞系-nAChRs。特别是，α6亚基通常与中脑中的α4 ^* -nAChRs共表达，从而掩盖了α6 ^*-nAChR（无α4）的功能和药理作用。在这项研究中，我们系统地描述了α6 ^* -nAChRs的药理作用和功能，并将这些特性与在同一细胞系中表达的α4β2nAChRs的特性进行了比较。使用在人类SH-EP1细胞系中具有β2和β3亚基的异源表达的人类α6/α3嵌合亚基（与α3跨膜结构域和细胞内环相连的α6N末端域）（α6 ^* -nAChRs）。进行膜片钳全细胞记录以测量这些受体介导的电流。在功能上，异源表达α6 ^*与α4β2-nAChRs相比，-nAChRs表现出出色的功能，并表现出独特的尼古丁诱导的电流响应，例如动力学，内向整流和脱敏恢复。在药理上，α6 ^* -nAChR对α6亚基选择性拮抗剂α-芋螺毒素MII高度敏感，但对美加明胺和二氢-β-类红血球碱的敏感性较低。尼古丁和乙酰胆碱被发现是α6 ^* -nAChRs的完全激动剂，而依巴替丁和半胱氨酸被确定为部分激动剂。异源表达的α6 ^* -nAChRs具有不同于α4β2-nAChRs的药理作用和功能，表明α6 ^* -nAChRs可以介导不同的胆碱能信号。我们的α6 ^*-nAChR表达系统可以用作一个出色的细胞模型，用于进一步研究α6 ^* -nAChR的功能和药理学。