Roles of nicotinic acetylcholine receptor β subunit cytoplasmic loops in acute desensitization and single-channel features.
Roles of nicotinic acetylcholine receptor β subunit cytoplasmic loops in acute desensitization and single-channel features.
复制标题
烟碱乙酰胆碱受体β亚基胞质环在急性脱敏和单通道特征中的作用。
DOI：
10.1016/j.neuroscience.2014.12.016
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发表时间：
2015
期刊：
影响因子：
3.3
通讯作者：
Wu,J
中科院分区：
文献类型：
--
作者：
Liu,Q;Kuo,Y-P;Shen,J;Lukas,RJ;Wu,J
评估位于烟碱乙酰胆碱受体（nAChR）亚基M3和M4跨膜结构域之间的大的第二细胞质环（C2）的生理作用。我们构建了嵌合β2 （β2χ）和β4 （β4χ）亚基，其中这些β亚基的“嵌套”C2结构域（但不是紧邻M3或M4结构域的约14个残基的“近端”序列）被来自5- ht3a受体亚基的相应序列所取代。我们之前报道了含有α4和β2χ亚基的异源表达的nAChR在其激动剂反应中表现出比全野生型α4β2-nAChR更快的全细胞电流衰减。这表明β2亚基的C2结构域在α4β2-nAChR急性脱敏中具有意想不到的功能作用。在人SH-EP1细胞系中，α4β4χ-nAChR的脱敏速度比α4β4-nAChR的脱敏速度更快，且具有稳定的异源表达。此外，细胞贴附的单通道记录显示，乙酰胆碱激活的α4β2χ-和α4β4χ-nAChR的平均打开概率显著低于完全野生型，平均打开时间显著缩短，平均关闭时间显著延长，但电导幅度没有差异。这些发现揭示了含有嵌合而非野生型β亚基的α4 * -nAChR更快脱敏的微观基础。我们的发现也与β亚基嵌套C2结构域在α4 * -nAChR功能调节中的新颖和意想不到的作用保持一致。
To evaluate physiological roles of the large, second cytoplasmic loops (C2) situated between the M3 and M4 transmembrane domains of nicotinic acetylcholine receptor (nAChR) subunits. We have constructed chimeric β2 (β2χ) and β4 (β4χ) subunits in which the “nested” C2 domains (but not the “proximal” sequences of ∼14 residues immediately adjacent to the M3 or M4 domains) of these β subunits were replaced by the corresponding sequence from the serotonin 5-HT3Areceptor subunit. We previously reported that heterologously expressed nAChR containing α4 and β2χ subunits displayed a faster whole-cell current decay in its agonist response compared to responses of all-wild-type α4β2-nAChR. This suggests an unexpected, functional role for the C2 domain of the β2 subunit in α4β2-nAChR acute desensitization. Here we report that there also is faster desensitization of α4β4χ-nAChR relative to α4β4-nAChR stably and heterologously expressed in the human SH-EP1 cell-line. In addition, cell-attached, single-channel recording shows that both acetylcholine-activated α4β2χ- and α4β4χ-nAChR have a significantly lower mean open probability, shorter mean open-time, and a longer mean closed-time than their fully wild-type counterparts while not having different conductance amplitudes. These findings reveal microscopic bases for the faster desensitization of α4∗-nAChR containing chimeric instead of wild-type β subunits. Our findings also remain consistent with novel and unexpected roles of β subunit-nested C2 domains in modulation of α4∗-nAChR function.