Channel blockers acting at N-methyl-D-aspartate receptors:: Differential effects of mutations in the vestibule and ion channel pore
Channel blockers acting at N-methyl-D-aspartate receptors:: Differential effects of mutations in the vestibule and ion channel pore
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DOI：
10.1124/mol.61.3.533
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发表时间：
2002-03-01
影响因子：
3.6
通讯作者：
Williams, K
中科院分区：
文献类型：
--
作者：
Kashiwagi, K;Masuko, T;Williams, K
大量结构多样的化合物作为NMDA受体的开放通道阻滞剂。它们可以在通道内共享离散或重叠的结合位点。本研究利用非洲爪蟾卵母细胞中表达的重组NMDA受体，用MK-801、美金刚和TB-3-4三种阻滞剂研究了NMDA受体亚基跨膜和成孔区及其周围突变的影响。NR1和NR2B的M2环中关键天冬酰胺残基的突变以及NR2B的M2中色氨酸残基的突变被MK-801、美金刚和TB-3-4减少阻滞。M1前区、M1后区、M3后区和m4后区残基突变对三种阻滞剂有不同的影响。这些区域的许多突变减少了MK-801和TB-3-4的阻滞，但对美金刚的阻滞没有影响。美金刚和MK-801对阻滞的不同影响不太可能是由这些阻滞剂的大小不同引起的。MK-801和TB-3-4中的苯环可能与孔内的芳香和疏水氨基酸残基发生疏水相互作用。前m1和M3区域的一些突变产生了本构性开放通道，其特征是保持电流大。各种突变的影响在基于已知KcsA钾通道孔结构的模型的背景下进行了讨论，并在处理NMDA受体亚基中溶剂可及残基的先前研究中进行了讨论，这些残基是由半胱氨酸诱变后的修饰决定的。
A large number of structurally diverse compounds act as open-channel blockers of NMDA receptors. They may share discrete or overlapping binding sites within the channel. In this study, the effects of mutations in and around the membrane-spanning and pore-forming regions of NMDA receptor subunits were studied with three blockers, MK-801, memantine, and TB-3-4, using recombinant NMDA receptors expressed in Xenopus laevis oocytes. Mutations at the critical asparagine residues in the M2 loop of NR1 and NR2B and at a tryptophan residue in M2 of NR2B reduced block by MK-801, memantine, and TB-3-4. Mutations at residues in the pre-M1, M1, M3, post-M3, and post-M4 regions had differential effects on the three blockers. Many mutations in these regions reduced block by MK-801 and TB-3-4 but had no effect on block by memantine. The differential effects on block by memantine and MK-801 are unlikely to be caused by differences in the size of these blockers. Benzyl rings in MK-801 and TB-3-4 may make hydrophobic interactions with aromatic and hydrophobic amino acid residues in the pore. Some mutations in the pre-M1 and M3 regions generated constitutively open channels, characterized by large holding currents. The effects of the various mutants are discussed in the context of models based on the known structure of the pore of the KcsA potassium channel and on previous studies dealing with solvent accessible residues in NMDA receptor subunits as determined by modification after cysteine mutagenesis.