Tuning activation of the AMPA-sensitive GluR2 ion channel by genetic adjustment of agonist-induced conformational changes
Tuning activation of the AMPA-sensitive GluR2 ion channel by genetic adjustment of agonist-induced conformational changes
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DOI：
10.1073/pnas.1037393100
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发表时间：
2003-05-13
影响因子：
11.1
通讯作者：
Gouaux, E
中科院分区：
文献类型：
--
作者：
Armstrong, N;Mayer, M;Gouaux, E
（S）-2-氨基-3-（3-羟基-5-甲基-4-异恶唑）丙酸（AMPA）受体在结合和通道门控方面区分激动剂; AMPA是高亲和力完全激动剂，而红藻氨酸盐是低亲和力部分激动剂。虽然有大量的文献对离子通道的部分激动剂活性的功能表征，基于结构的机制是稀缺的。在这里，我们调查的作用Leu-650，结合裂缝残基之间保守的AMPA受体，在保持激动剂的特异性和调节激动剂结合和通道门控，通过使用生理学，X-射线晶体学和生化技术。将Leu-650改变为Thr产生了相对于WT受体对红藻氨酸的响应更强有力和有效性以及对AMPA的响应较弱有力和有效性的受体。Leu-650到Thr突变体的晶体结构揭示了在红藻氨酸盐结合状态下的结构域闭合的增加以及在AMPA结合形式下的部分闭合和完全闭合构象。我们的研究结果表明，激动剂可以诱导一系列的构象在GluR 2配体结合的核心和域关闭直接相关的通道激活。L 650 T突变体的部分闭合的AMPA结合构象可能捕获受体的激动剂结合的非活性状态的结构。连同以前解决的结构，我们已经确定了激动剂结合和随后的构象重排的机制。
The (S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazole) propionic acid (AMPA) receptor discriminates between agonists in terms of binding and channel gating; AMPA is a high-affinity full agonist, whereas kainate is a low-affinity partial agonist. Although there is extensive literature on the functional characterization of partial agonist activity in ion channels, structure-based mechanisms are scarce. Here we investigate the role of Leu-650, a binding cleft residue conserved among AMPA receptors, in maintaining agonist specificity and regulating agonist binding and channel gating by using physiological, x-ray crystallographic, and biochemical techniques. Changing Leu-650 to Thr yields a receptor that responds more potently and efficaciously to kainate and less potently and efficaciously to AMPA relative to the WT receptor. Crystal structures of the Leu-650 to Thr mutant reveal an increase in domain closure in the kainate-bound state and a partially closed and a fully closed conformation in the AMPA-bound form. Our results indicate that agonists can induce a range of conformations in the GluR2 ligand-binding core and that domain closure is directly correlated to channel activation. The partially closed, AMPA-bound conformation of the L650T mutant likely captures the structure of an agonist-bound, inactive state of the receptor. Together with previously solved structures, we have determined a mechanism of agonist binding and subsequent conformational rearrangements.