Domain near TM1 influences agonist and antagonist responses of peptide-gated Na+ channels
Domain near TM1 influences agonist and antagonist responses of peptide-gated Na+ channels
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DOI：
10.1007/s00424-005-1385-7
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发表时间：
2005-06-01
影响因子：
4.5
通讯作者：
Cottrell, GA
中科院分区：
文献类型：
--
作者：
Cottrell, GA
采用分子生物学方法分析不同氨基酸对配体激活的重要性，并确定阿米洛利对肽-（Phe-Met-Arg-Phe-NH2，FMRFamide）门控Na+通道（退化蛋白/上皮Na通道（DEG/ENaC）家族成员）的作用。阿米洛利是大多数 DEG/ENa 通道的低亲和力阻断剂，但对其中一些通道的反应具有不寻常的增强作用。嵌合体在爪蟾卵母细胞中表达并进行电生理学研究。 Helix aspersa 和 Helisoma trivolvis 通道特性的差异突出显示了靠近第一个跨膜片段 (TM1) 的胞外结构域的 50 个残基序列，该序列影响对 FMRFamide 的敏感性，以及阿米洛利是否阻断或增强对 FMRFamide 的反应。对从 H. aspersa 制备的嵌合体和其他两个物种（海兔和 Lymnaea stagnalis）的细胞外结构域进行比较以及进一步构建体的制备表明，H. aspersa 序列中的氨基酸 128-134 对于确定阿米洛利的主要作用和影响 FMRFamide 的 EC50 非常重要。结果还表明，该区域的氨基酸受到胞外结构域其他区域氨基酸的影响，从而不仅影响反应的幅度，而且影响反应的时程和脱敏。
A molecular biological approach was used to analyse the importance of different amino acids for ligand activation and for determining the action of amiloride on peptide- (Phe-Met-Arg-Phe-NH2, FMRFamide)-gated Na+ channels, members of the degenerin/epithelial Na channel (DEG/ENaC) family. Amiloride is a low-affinity blocker of most DEG/ENa channels, but has an unusual enhancing effect on responses of some of them. Chimeras were expressed in Xenopus oocytes and studied electrophysiologically. Differences in properties of channels from Helix aspersa and Helisoma trivolvis highlighted a sequence of 50 residues of the extracellular domain, near the first transmembrane segment (TM1), that affected sensitivity to FMRFamide, and whether amiloride blocked or enhanced the response to FMRFamide. Comparisons of chimeras prepared from H. aspersa and the extracellular domains of two other species, Aplysia californica and Lymnaea stagnalis and the preparation of further constructs, showed that amino acids 128-134 in the H. aspersa sequence are important in determining the predominant effect of amiloride and influencing the EC50 of FMRFamide. The results also showed that amino acids in this region are influenced by amino acids in other regions of the extracellular domain so as to affect not only the magnitude of responses, but also their time course and desensitisation.