Expression of nigrostriatal α6-containing nicotinic acetylcholine receptors is selectively reduced, but not eliminated, by β3 subunit gene deletion
Expression of nigrostriatal α6-containing nicotinic acetylcholine receptors is selectively reduced, but not eliminated, by β3 subunit gene deletion
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DOI：
10.1124/mol.105.011940
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发表时间：
2005-06-01
影响因子：
3.6
通讯作者：
Whiteaker, P
中科院分区：
文献类型：
--
作者：
Gotti, C;Moretti, M;Whiteaker, P
神经元烟碱乙酰胆碱受体（nAChR）α 6和β 3亚基的mRNA在黑质和腹侧被盖区的多巴胺能细胞中大量表达和共定位。使用亚基缺失突变小鼠的研究表明，α 6或β 3依赖性nAChR以高亲和力结合α-芋螺毒素MII（α-CtxMII）并调节纹状体多巴胺释放。本研究探讨了β 3亚基缺失突变对纹状体和中脑nAChR表达、组成和药理学的影响。使用亚基特异性抗体进行的配体结合和免疫沉淀实验表明，与β 3（+/+）对照相比，β 3无效突变选择性地降低了纹状体α 6（*）nAChR表达的76%。平行实验显示，中脑α 3（*）和α 6（*）nAChR的减少较小（与β 3（+/+）对照相比，分别为34%和42%）。沉降系数测定表明，β 3（-/-）纹状体中残留的α 6（*）nAChR是五聚体，与野生型对应物一样。对免疫纯化的β 3（*）nAChRs的免疫沉淀实验表明，几乎所有野生型纹状体β 3（*）nAChRs也含有α 4、α 6和β 2亚基，尽管也表达少量非β 3 α 6（*）nAChRs。β 3亚单位的掺入似乎增加了α 4参与α 6 β 2（*）复合物。I-125-Epibatidine竞争结合研究表明，β 3（-/-）小鼠纹状体中α 6（*）nAChR的α-CtxMII亲和力与从β 3（-/-）动物中分离的α 6（*）nAChR相似。总之，这些实验的结果表明，β 3亚基对于多巴胺能神经元中α 6（*）nAChR的正确组装、稳定性和/或转运是重要的，并影响它们的亚基组成。然而，β 3亚基表达对于α 6（*）、高亲和力α-CtxMII结合nAChR的表达不是必需的。
mRNAs for the neuronal nicotinic acetylcholine receptor (nAChR) alpha 6 and beta 3 subunits are abundantly expressed and colocalized in dopaminergic cells of the substantia nigra and ventral tegmental area. Studies using subunit-null mutant mice have shown that alpha 6- or beta 3-dependent nAChRs bind alpha-conotoxin MII (alpha-CtxMII) with high affinity and modulate striatal dopamine release. This study explores the effects of beta 3 subunit-null mutation on striatal and midbrain nAChR expression, composition, and pharmacology. Ligand binding and immunoprecipitation experiments using subunit-specific antibodies indicated that beta 3-null mutation selectively reduced striatal alpha 6(*) nAChR expression by 76% versus beta 3(+/+) control. Parallel experiments showed a smaller reduction in both midbrain alpha 3(*) and alpha 6(*) nAChRs (34 and 42% versus beta 3(+/+) control, respectively). Sedimentation coefficient determinations indicated that residual alpha 6(*) nAChRs in beta 3(-/-) striatum were pentameric, like their wild-type counterparts. Immunoprecipitation experiments on immunopurified beta 3(*) nAChRs demonstrated that almost all wild-type striatal beta 3(*) nAChRs also contain alpha 4, alpha 6, and beta 2 subunits, although a small population of non-beta 3 alpha 6(*) nAChRs is also expressed. beta 3 subunit incorporation seemed to increase alpha 4 participation in alpha 6 beta 2(*) complexes. I-125-Epibatidine competition binding studies showed that the alpha-CtxMII affinity of alpha 6(*) nAChRs from the striata of beta 3(-/-) mice was similar to those isolated from beta 3(-/-) animals. Together, the results of these experiments show that the beta 3 subunit is important for the correct assembly, stability and/or transport of alpha 6(*) nAChRs in dopaminergic neurons and influences their subunit composition. However, beta 3 subunit expression is not essential for the expression of alpha 6(*), high-affinity alpha-CtxMII binding nAChRs.