Nicotinic acetylcholine receptors assembled from the α7 and β3 subunits
Nicotinic acetylcholine receptors assembled from the α7 and β3 subunits
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DOI：
10.1074/jbc.274.26.18335
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发表时间：
1999-06-25
影响因子：
4.8
通讯作者：
Ballivet, M
中科院分区：
文献类型：
--
作者：
Palma, E;Maggi, L;Ballivet, M
细胞内记录进行电压钳爪蟾卵母细胞注射后的混合物的cDNA编码的β 3和突变体α 7（（L247 T）α 7）神经元烟碱乙酰胆碱受体（nAChR）亚基。表达的受体保持对甲基绿乌头碱和α-银环蛇毒素的敏感性，但表现出与同聚体（L247 T）α 7受体明显不同的功能特征。异聚体（L247 T）α 7 β 3 nAChR比L247 Ta 7 nAChR具有更低的表观亲和力和更快的脱敏速率，在I-V关系中表现出非线性，并被5-羟色胺抑制，很像野生型α 7（（WT）α 7）nAChR。在细胞附着模式的单通道记录显示单一的事件与19皮西门子的斜率电导和5毫秒的寿命，这两个值都远远小于那些同源受体通道。在注射（WT）α 7和β 3 cDNA的混合物后，获得了异聚nAChR的质膜组装的明确证据，尽管ACh不能激活这些受体。它的结论是β 3，长期以来被认为是一个孤儿亚基，容易与其他亚基共组装形成异聚体受体，其中一些可能是胆碱能功能的负调节。
Intracellular recordings were performed in voltage-clamped Xenopus oocytes upon injection with a mixture of cDNAs encoding the beta 3 and mutant alpha 7 ((L247T)alpha 7) neuronal nicotinic acetylcholine receptor (nAChR) subunits. The expressed receptors maintained sensitivity to methyllycaconitine and to alpha-bungarotoxin but exhibited a functional profile strikingly different from that of the homomeric (L247T)alpha 7 receptor, The heteromeric (L247T)alpha 7 beta 3 nAChR had a lower apparent affinity and a faster rate of desensitization than L247Ta7 nAChR, exhibited nonlinearity in the I-V relationship, and was inhibited by 5-hydroxytryptamine, much like wild type alpha 7 ((WT)alpha 7) nAChR. Single channel recordings in cell-attached mode revealed unitary events with a slope conductance of 19 picosiemens and a lifetime of 5 ms, both values being much smaller than those of the homomeric receptor channel. Upon injection with a mixture of (WT)alpha 7 and beta 3 cDNAs, clear evidence was obtained for the plasma membrane assembly of heteromeric nAChRs, although ACh could not activate these receptors. It is concluded that beta 3, long believed to be an orphan subunit, readily co-assembles with other subunits to form heteromeric receptors, some of which may be negative regulators of cholinergic function.