Molecular determinants of proton-sensitive N-methyl-D-aspartate receptor gating
Molecular determinants of proton-sensitive N-methyl-D-aspartate receptor gating
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DOI：
10.1124/mol.63.6.1212
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发表时间：
2003-06-01
影响因子：
3.6
通讯作者：
Zheng, F
中科院分区：
文献类型：
--
作者：
Low, CM;Lyuboslavsky, P;Zheng, F
细胞外质子抑制n -甲基- d -天冬氨酸（NMDA）受体，其IC50值在生理pH范围内。为了确定质子敏感性的分子决定因素，我们使用NR1亚基的扫描诱变来寻找控制NMDA受体质子抑制的残基。胞外结构域的同源性建模表明，突变干扰pH敏感性的残基定位在离散区域。大多数强烈影响质子敏感性的突变集中在第二跨膜结构域（M3）的胞外端和邻近连接NR1甘氨酸结合结构域S2部分的连接体上。NR2A的突变证实了类似区域控制着该亚基的pH敏感性，并确定了第三跨膜结构域（M4）和NR2谷氨酸结合结构域S2部分之间的连接区域是质子敏感性的另一个决定因素。其中一个突变受体NR1(A649C)/ NR2A（A651T）显示质子的IC50降低了145倍（IC50为17.3 muM，对应于pH 4.9）。M3-S2连接区被认为控制NMDA受体门控，导致质子传感器和受体门可能在结构和功能上集成的假设。
Extracellular protons inhibit N-methyl-D-aspartate ( NMDA) receptors with an IC50 value in the physiological pH range. To identify the molecular determinants of proton sensitivity, we used scanning mutagenesis of the NR1 subunit to search for residues that control proton inhibition of NMDA receptors. Homology modeling of the extracellular domains suggested that residues at which mutations perturbed pH sensitivity were localized in discrete regions. The majority of mutations that strongly affected proton sensitivity were clustered in the extracellular end of the second transmembrane domain (M3) and adjacent linker leading to the S2 portion of the glycine-binding domain of NR1. Mutations in NR2A confirmed that the analogous region controls the pH sensitivity of this subunit and also identified the linker region between the third transmembrane domain (M4) and the S2 portion of the NR2 glutamate binding domain as an additional determinant of proton sensitivity. One mutant receptor, NR1(A649C)/ NR2A(A651T), showed a 145-fold reduction in the IC50 for protons (IC50, 17.3 muM corresponding to pH 4.9). The M3-S2 linker region has been suggested to control NMDA receptor gating, leading to the hypothesis that the proton sensor and receptor gate may be structurally and functionally integrated.