Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna, Austria.
Dev Neurobiol. 2011 May;71(5):390-9. doi: 10.1002/dneu.20870.
Heteropentameric nicotinic acetylcholine receptors (nAChR) mediate fast synaptic transmission in ganglia of the autonomic nervous system. It is undisputed that α3 and β4 are the predominant subunits in the superior cervical ganglion (SCG); however, reports on the presence of receptors that contain α4 have been controversial. Here, we have searched for the presence of α4-containing nAChRs in the postnatal rat and mouse SCG. We now show by immunoprecipitation combined with radioligand binding that α4-containing receptors constitute about 20% of hetero-oligomeric nAChRs in postnatal Day 3 (P3) mice. However, already by P9, the level of α4 approaches zero. In contrast, the number of α4-containing receptors is close to zero in the rat SCG at all times investigated. Deletion of the β2 subunit by using α5β2-double knockout (KO) mice removes all α4-containing receptors, suggesting that in the postnatal mouse SCG, α4 co-assembles only with β2 but not with β4. α4β2 receptors are, on the other hand, up-regulated in the SCG of P3 α5β4-double KO mice, where they make up about 50% of receptors that bind [(3) H]-epibatidine. Nonetheless, receptors on the surface of SCG neurons from α5β4-double KO mice maintained for one to two days in culture comprise <10% of α4β2 and >90% of α3β2, as determined by patch clamp recordings with α4β2- and α3β2-specific ligands. We propose that in the P3 SCG of wild type mice, α3β4 (±α5) represent about 62% of receptors, whereas 17% are α3β2β4, and 21% are α4β2 (±α5) receptors.
杂合五聚体烟碱型乙酰胆碱受体 (nAChR) 介导自主神经系统神经节中的快速突触传递。无可争议的是，α3 和 β4 是颈上神经节 (SCG) 中的主要亚基；然而，关于包含 α4 的受体存在的报告一直存在争议。在这里，我们在新生大鼠和小鼠的 SCG 中搜索了含有 α4 的受体的存在。我们现在通过免疫沉淀结合放射性配体结合表明，含有 α4 的受体在出生后第 3 天 (P3) 的小鼠中构成异源寡聚 nAChR 的约 20%。然而，到 P9 时，α4 的水平接近零。相比之下，在所有研究的时间点，α4 包含的受体在大鼠 SCG 中接近零。使用 α5β2-双敲除 (KO) 小鼠删除 β2 亚基会去除所有含有 α4 的受体，这表明在新生小鼠的 SCG 中，α4 仅与 β2 而非 β4 组装。另一方面，在 P3 的 α5β4-双 KO 小鼠的 SCG 中，α4β2 受体上调，其中约 50%的结合 [(3) H]-epibatidine 的受体为 α4β2。尽管如此，在培养 1 到 2 天的 α5β4 双 KO 小鼠的 SCG 神经元表面的受体中，α4β2 和 α3β2 的比例分别为 <10%和 >90%，这是通过用 α4β2 和 α3β2 特异性配体进行膜片钳记录确定的。我们提出，在 P3 野生型小鼠的 SCG 中，α3β4(±α5)约占受体的 62%，而 17%是 α3β2β4，21%是 α4β2(±α5)受体。
