Differential sensitivity of recombinant N-methyl-D-aspartate receptor subtypes to zinc inhibition
Differential sensitivity of recombinant N-methyl-D-aspartate receptor subtypes to zinc inhibition
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DOI：
10.1124/mol.51.6.1015
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发表时间：
1997-06-01
影响因子：
3.6
通讯作者：
Raymond, LA
中科院分区：
文献类型：
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作者：
Chen, NS;Moshaver, A;Raymond, LA
锌存在于突触囊泡的一个亚类的谷氨酸能终扣中，并被认为与谷氨酸在这些突触处结合。各种研究表明，锌可能通过抑制N-甲基-D-天冬氨酸（NMDA）型谷氨酸受体而在兴奋性传递的调节以及兴奋性毒性中发挥作用。为了进一步研究锌对不同亚基组成的NMDA受体的调节作用，我们在HEK 293细胞中共表达了重组亚基NR 1和NR 2A和/或NR 2B。在这些转染细胞的全细胞膜片钳记录，锌抑制峰谷氨酸诱发的电流反应在一个非竞争性的方式，但有显着差异的受体亚型之间的敏感性锌抑制。对于NR 1/NR 2A，锌以电压非依赖性方式抑制了约40%的峰值电流，IC 50值为5.0 +/- 1.6 nhl，V-H值为-60 mV;其余部分在第二个电压依赖性位点被阻断，IC 50值为79 +/- 18 μ M。相反，NR 1/NR 2B电流在电压非依赖性位点显示几乎完全抑制，IC 50值为9.5 +/- 3.3 μ M。NR 1、NR 2A和NR 2B共转染的细胞表现出介于NR 1/NR 2A和NR 1/NR 2B之间的锌敏感性。此外，锌以剂量依赖性方式加速NR 1/NR 2A和NR 1/NR 2B的宏观脱敏，显然独立于甘氨酸敏感性脱敏和Ca 2+依赖性失活;最大效应是使NR 1/NR 2A的脱敏时间常数降低75%，使NR 1/NR 2B的脱敏时间常数降低90%。锌对NR 1/NR 2A和NR 1/NR 2B电流的差异调节可能在调节NMDA受体诱导的突触可塑性和神经毒性中起作用。
Zinc has been shown to be present in synaptic vesicles of a subset of glutamatergic boutons and is believed to be core-leased with glutamate at these synapses, A variety of studies have suggested that zinc might play a role in modulation of excitatory transmission, as well as excitotoxicity, by inhibiting N-methyl-D-aspartate (NMDA)-type glutamate receptors. To further investigate the modulatory effects of zinc on NMDA receptors of different subunit compositions, we coexpressed the recombinant subunit NR1 with NR2A and/or NR2B in HEK 293 cells. In whole-cell patch-clamp recordings from these transfected cells, zinc inhibited peak glutamate-evoked current responses in a noncompetitive manner, but there were significant differences between the receptor subtypes in sensitivity to zinc inhibition. For NR1/NR2A, similar to 40% of the peak current was inhibited by zinc in a voltage-independent manner with an IC50 value of 5.0 +/- 1.6 nhl and at a V-H value of -60 mV; the remainder was blocked at a second, voltage-dependent site with an IC50 value of 79 +/- 18 mu M. In contrast, NR1/NR2B currents showed nearly complete inhibition at a voltage-independent site with an IC50 value of 9.5 +/- 3.3 mu M. Cells cotransfected with NR1, NR2A, and NR2B showed zinc sensitivity intermediate between that characteristic of NR1/NR2A and that of NR1/NR2B. Furthermore, zinc accelerated the macroscopic desensitization of both NR1/NR2A and NR1/NR2B in a dose-dependent manner, apparently independently of glycine-sensitive desensitization and Ca2+-dependent inactivation; maximal effects were to decrease desensitization time constants for NR1/NR2A by similar to 75% and for NR1/NR2B by similar to 90%. Differential modulation of NR1/NR2A and NR1/NR2B currents by zinc may play a role in regulating NMDA receptor-induced synaptic plasticity and neurotoxicity.