Kuryatov A, Olale F, Cooper J, Choi C, Lindstrom J
Department of Neuroscience, University of Pennsylvania Medical School, 217 Stemmler Hall, 36th and Hamilton Walk, Philadelphia, PA 19104-6074, USA.
Neuropharmacology. 2000 Oct;39(13):2570-90. doi: 10.1016/s0028-3908(00)00144-1.
Many nicotinic acetylcholine receptor (AChR) subunits are known to be co-expressed with the alpha6 subunit in neurons. Because alpha6beta4 AChRs assemble inefficiently and alpha6beta2 AChRs not at all, more complex mixtures of human subunit cDNAs were tested for their abilities to form functional AChRs when expressed in Xenopus oocytes. alpha6beta4beta3 AChRs produced the largest and most consistent responses. alpha6alpha3beta2 AChRs exhibited reduced potency for ACh and increased potency and efficacy for nicotine compared to alpha3beta2 AChRs, but similar resistance to functional inactivation after prolonged exposure to nicotine. alpha6alpha4beta2 AChRs differed little in potency or efficacy for ACh or nicotine compared to alpha4beta2 AChRs, and had similarly high sensitivity to inactivation by prolonged exposure to nicotine. Co-expression of alpha6 and beta2 cRNAs resulted in large numbers of (3)H-epibatidine binding sites in the form of large aggregates but not in functional pentameric AChRs. Co-expression of alpha6, beta2, and alpha5 resulted in assembly of some functional pentameric AChRs. Chimeras with the large extracellular domain of alpha6 and the rest from either alpha3 or alpha4 efficiently formed functional AChRs. Thus, the extracellular domain of alpha6 efficiently assembles with beta2 to form ACh binding sites, but more C-terminal domains cause difficulties in forming pentameric AChRs. Chimeric alpha6/alpha3 and alpha6/alpha4 AChRs containing either beta2 or beta4 subunits were blocked by alpha-conotoxin MII which had previously been reported to be specific for alpha3beta2 AChRs.
已知许多烟碱型乙酰胆碱受体（AChR）亚基在神经元中与α6亚基共同表达。由于α6β4 AChRs组装效率低下，而α6β2 AChRs根本无法组装，因此测试了更复杂的人类亚基cDNA混合物在非洲爪蟾卵母细胞中表达时形成功能性AChRs的能力。α6β4β3 AChRs产生了最大且最一致的反应。与α3β2 AChRs相比，α6α3β2 AChRs对乙酰胆碱（ACh）的效力降低，对尼古丁的效力和效能增加，但在长时间暴露于尼古丁后对功能失活的抵抗力相似。与α4β2 AChRs相比，α6α4β2 AChRs对ACh或尼古丁的效力或效能差异不大，并且对长时间暴露于尼古丁导致的失活具有相似的高敏感性。α6和β2 cRNAs的共表达导致大量以大聚集体形式存在的（3）H-埃博霉素结合位点，但未形成功能性五聚体AChRs。α6、β2和α5的共表达导致一些功能性五聚体AChRs的组装。具有α6大细胞外结构域和α3或α4其余部分的嵌合体有效地形成了功能性AChRs。因此，α6的细胞外结构域与β2有效组装形成ACh结合位点，但更多的C末端结构域在形成五聚体AChRs时会产生困难。含有β2或β4亚基的嵌合α6/α3和α6/α4 AChRs被α-芋螺毒素MII阻断，α-芋螺毒素MII此前被报道对α3β2 AChRs具有特异性。
