Different sites of alcohol action in the NMDA receptor GluN2A and GluN2B subunits.
Different sites of alcohol action in the NMDA receptor GluN2A and GluN2B subunits.
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DOI：
10.1016/j.neuropharm.2015.05.018
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发表时间：
2015-10
影响因子：
4.7
通讯作者：
Peoples RW
中科院分区：
文献类型：
--
作者：
Zhao Y;Ren H;Dwyer DS;Peoples RW
NMDA受体是中枢神经系统酒精作用的主要靶点，最近的行为和细胞研究指出GluN2B亚单位在酒精作用中的重要性。我们和其他人以前已经确定了NMDA受体GluN2A亚单位第三和第四膜相关(M)区域的四个氨基酸位置，它们同时影响离子通道门控和酒精敏感性。在这项研究中，我们发现GluN2B亚基四个对应位置中的两个位置的替换突变，即F637和G826，影响乙醇敏感性和离子通道门控。由于826位在天然蛋白中含有甘氨酸残基，我们将注意力集中在GluN2B(F637)上。GluN2B(F637)的替换突变显著改变了乙醇的IC50值、峰值(Ip)和稳态(ISS)电流的谷氨酸EC50值以及稳态与峰值电流比(ISS：IP)。表观谷氨酸亲和力的变化不是由于脱敏状态下的激动剂捕获引起的，因为谷氨酸ISS EC50值与ISS：IP值没有相关性。乙醇敏感性与Ip和ISS谷氨酸EC50值均相关，但与ISS：IP无关。GluN2B(F637)突变株的乙醇IC50、谷氨酸EC50和ISS：IP值与GluN2A(F636)突变株的相应值高度相关，这与该位置在两个亚基中的功能相似。这些结果表明，GluN2B(Phe637)对乙醇作用和NMDA受体的离子通道功能具有调节作用。然而，尽管高度保守的M结构域序列，乙醇对GluN2A和GluN2B亚基的作用不同。
The NMDA receptor is a major target of alcohol action in the CNS, and recent behavioral and cellular studies have pointed to the importance of the GluN2B subunit in alcohol action. We and others have previously characterized four amino acid positions in the third and fourth membrane-associated (M) domains of the NMDA receptor GluN2A subunit that influence both ion channel gating and alcohol sensitivity. In this study, we found that substitution mutations at two of the four corresponding positions in the GluN2B subunit, F637 and G826, influence ethanol sensitivity and ion channel gating. Because position 826 contains a glycine residue in the native protein, we focused our attention on GluN2B(F637). Substitution mutations at GluN2B(F637) significantly altered ethanol IC50 values, glutamate EC50 values for peak (Ip) and steady-state (Iss) current, and steady-state to peak current ratios (Iss:Ip). Changes in apparent glutamate affinity were not due to agonist trapping in desensitized states, as glutamate Iss EC50 values were not correlated with Iss:Ip values. Ethanol sensitivity was correlated with values of both Ip and Iss glutamate EC50, but not with Iss:Ip. Values of ethanol IC50, glutamate EC50, and Iss:Ip for mutants at GluN2B(F637) were highly correlated with the corresponding values for mutants at GluN2A(F636), consistent with similar functional roles of this position in both subunits. These results demonstrate that GluN2B(Phe637) regulates ethanol action and ion channel function of NMDA receptors. However, despite highly conserved M domain sequences, ethanol's actions on GluN2A and GluN2B subunits differ.