The delta subfamily of glutamate receptors: characterization of receptor chimeras and mutants
The delta subfamily of glutamate receptors: characterization of receptor chimeras and mutants
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DOI：
10.1111/ejn.12193
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发表时间：
2013-05-01
影响因子：
3.4
通讯作者：
Hollmann, Michael
中科院分区：
文献类型：
--
作者：
Orth, Angela;Tapken, Daniel;Hollmann, Michael
由于序列的同源性，Delta受体GluD1和GluD2被认为是离子型谷氨酸受体的一个亚家族。虽然它们在小脑功能和高频听力中发挥着重要作用，并且似乎在突触上具有结构性功能，但尚未观察到配体门控离子通道功能。然而，我们之前已经证明，当GluD2与红藻氨酸受体的配体结合结构域嫁接时，可以形成功能离子通道。在这项研究中，我们更详细地描述了这个嵌合体以及额外的大鼠Delta受体嵌合体和点突变。我们发现，海人藻酸受体配体结合域也使GluD1具有功能，当提供AMPA受体配体结合域时，GluD2也成为一种功能离子通道。点突变表明，GluD2离子孔的操作类似于但不完全相同的AMPA(-amino-3-hydroxy-5-methylisoxazole-4-propionic酸)和红藻氨酸受体。在连接配体结合域和离子孔域的连接区内的保守精氨酸处突变的GluD2显示出自发电流，该电流在没有激动剂的情况下发生，并被激动剂应用抑制，这一行为使人想起先前描述的Lurcher突变体的行为。使用我们的嵌合方法，我们提供的证据表明，激动剂对自发电流的抑制可能是由脱敏引起的。我们的结果表明，Delta受体具有与AMPA和海人藻酸受体相似但不完全相同的功能门控机制和离子渗透途径，而关键的区别似乎位于配体结合区域。
The delta receptors, GluD1 and GluD2, are regarded as a subfamily of the ionotropic glutamate receptors solely because of sequence homology. While they play important roles in cerebellar function and high-frequency hearing and appear to serve structural functions at synapses, ligand-gated ion channel function has not been observed. However, we have previously shown that GluD2 can form functional ion channels when grafted with the ligand binding domain of a kainate receptor. In this study, we characterized this chimera as well as additional rat delta receptor chimeras and point mutants in more detail. We found that the kainate receptor ligand binding domain renders GluD1 functional as well, and GluD2 becomes a functional ion channel also when provided with an AMPA receptor ligand binding domain. Point mutations indicate that the GluD2 ion pore operates similarly but not identically to that of AMPA (-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and kainate receptors. GluD2 mutated at a conserved arginine within the linker region connecting the ligand binding domain to the ion pore domain displays spontaneous currents that occur in the absence of agonists and are inhibited by agonist application a behavior reminiscent of that of the previously characterized lurcher mutant. Using our chimeric approach, we provide evidence that this inhibition of spontaneous currents by agonists may be caused by desensitization. Our results show that delta receptors have functional gating machineries and ion permeation pathways similar but not identical to those of AMPA and kainate receptors, while the key differences seem to be located within the ligand binding domain.