Modulation of glycine potency in rat recombinant NMDA receptors containing chimeric NR2A/2D subunits expressed in Xenopus laevis oocytes
Modulation of glycine potency in rat recombinant NMDA receptors containing chimeric NR2A/2D subunits expressed in Xenopus laevis oocytes
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DOI：
10.1113/jphysiol.2007.143172
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发表时间：
2008-01-01
影响因子：
5.5
通讯作者：
Wyllie, David J. A.
中科院分区：
文献类型：
--
作者：
Chen, Philip E.;Geballe, Matthew T.;Wyllie, David J. A.
异聚体NMDAR由促凝剂甘氨酸结合NR 1亚基和谷氨酸结合NR 2亚基组成。哺乳动物中枢神经系统（CNS）中的大多数功能性NMDAR含有两个NRI亚基和两个NR 2亚基，其中存在四种类型（A-D）。我们表明，各种内源性和合成的甘氨酸位点促凝剂的效力在重组NMDAR之间变化，使得在含NR 2D的NMDAR处看到最高效力，在含NR 2A的NMDAR处看到最低效力。这种异质性由NMDAR复合物内的特定NR 2亚基指定，因为甘氨酸结合NRI亚基对所有研究的NMDAR都是共同的。为了确定负责这种异质性的分子决定因素，我们产生了嵌合NR 2A/2D亚基，我们交换了S1和S2区域，形成配体结合域，并在非洲爪蟾卵母细胞中与NRI亚基共表达。含有NR 2A亚基（包括NR 2D S1区）的NMDAR的甘氨酸浓度-响应曲线给出的平均甘氨酸EC 50值与含有NR 2A（WT）的NMDAR相似。然而，含有包括NR 2D S2区或NR 2D S1和S2区两者的NR 2A亚基的受体给出与在含有NR 2D（WT）的NMDAR中所见的类似的甘氨酸效力。特别地，NR 2A亚基的S2区中的两个残基（Lys 719和Tyr 735）当突变为NR 2D亚基中发现的相应残基时影响甘氨酸效力。我们得出结论，甘氨酸效力的变化是由激动剂结合后发生的NRI和NR 2配体结合结构域之间的相互作用引起的，并且可能参与确定通道门控的初始构象变化。
Heteromeric NMDARs are composed of coagonist glycine-binding NR1 subunits and glutamate-binding NR2 subunits. The majority of functional NMDARs in the mammalian central nervous system (CNS) contain two NRI subunits and two NR2 subunits of which there are four types (A-D). We show that the potency of a variety of endogenous and synthetic glycine-site coagonists varies between recombinant NMDARs such that the highest potency is seen at NR2D-containing and the lowest at NR2A-containing NMDARs. This heterogeneity is specified by the particular NR2 subunit within the NMDAR complex since the glycine-binding NRI subunit is common to all NMDARs investigated. To identify the molecular determinants responsible for this heterogeneity, we generated chimeric NR2A/2D subunits where we exchanged the S1 and S2 regions that form the ligand-binding domains and coexpressed these with NRI subunits in Xenopus laevis oocytes. Glycine concentration-response curves for NMDARs containing NR2A subunits including the NR2D S1 region gave mean glycine EC50 values similar to NR2A(WT)-containing NMDARs. However, receptors containing NR2A subunits including the NR2D S2 region or both NR2D SI and S2 regions gave glycine potencies similar to those seen in NR2D (WT)-containing NMDARs. In particular, two residues in the S2 region of the NR2A subunit (Lys719 and Tyr735) when mutated to the corresponding residues found in the NR2D subunit influence glycine potency. We conclude that the variation in glycine potency is caused by interactions between the NRI and NR2 ligand-binding domains that occur following agonist binding and which may be involved in the initial conformation changes that determine channel gating.