Ethanol inhibition of recombinant NR1/2A receptors: effects of heavy metal chelators and a zinc-insensitive NR2A mutant.
Ethanol inhibition of recombinant NR1/2A receptors: effects of heavy metal chelators and a zinc-insensitive NR2A mutant.
复制标题
重组 NR1/2A 受体的乙醇抑制：重金属螯合剂和锌不敏感 NR2A 突变体的作用。
DOI：
10.1016/j.alcohol.2003.07.002
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Smothers,Corigan
中科院分区：
文献类型：
--
作者：
Woodward,JohnJ;Smothers,Corigan
N-甲基-d-天冬氨酸(NMDA)受体是神经细胞中高表达的离子型谷氨酸受体的一种亚型。这些受体是钙离子通透性的，调节各种形式的可塑性，包括谷氨酸突触的长期增强。乙醇明显抑制NMDA受体的功能，神经元长期接触乙醇与戒断过程中NMDA受体功能增强有关。以前对重组NMDA受体的研究结果表明，亚基组成影响NMDA受体的乙醇敏感性，含有NR2A的受体通常比含有其他NR2亚基的受体表现出更大的乙醇抑制作用。含有NR2a的NMDA受体对其他通道功能调节剂特别敏感，包括重金属，如锌。虽然锌通过与通道位置的电压依赖的相互作用抑制微摩尔浓度的NMDA受体，但低纳摩尔浓度的锌以不依赖于电压的方式抑制含有NR2A的受体。在这项研究中，我们研究了在锌的影响最小的条件下，乙醇对人胚胎肾293(HEK 293)细胞中NR1/NR2A受体表达的影响。在对照条件下，乙醇(100 MM)对NR1/2A受体的峰电流和稳态电流的抑制率为35%~40%。如前所述，在实验溶液中加入重金属螯合剂乙二胺四乙酸[(EDTA)；10μM]或其他螯合化合物可增强N-甲基-D-天冬氨酸的刺激电流。在乙二胺四乙酸二钠(10μM)存在下，100 mM乙醇对Nr1/2A型电流的抑制率约为28%。正如预期的那样，表达NR1亚单位的细胞和锌不敏感的NR2A突变体(H128S)记录的电流没有被锌螯合剂增强。在这些细胞中，乙醇(100 MM)抑制NMDA受体电流约28%，这种抑制作用不受EDTA的影响。这些结果支持这样一种观点，即实验溶液中存在的低水平锌可能会影响含有NR2A亚单位的NMDA受体的表观酒精敏感性。
N-methyl-d-aspartate (NMDA) receptors are a subtype of ionotropic glutamate receptors that are highly expressed in brain neurons. These receptors are calcium permeable and regulate various forms of plasticity, including long-term potentiation of glutamate synapses. Acutely, ethanol inhibits the function of NMDA receptors, and chronic exposure of neurons to ethanol is associated with enhanced NMDA receptor function during withdrawal. Results from previous studies with recombinant NMDA receptors have demonstrated that subunit composition influences the ethanol sensitivity of NMDA receptors, with NR2A-containing receptors often showing greater inhibition by ethanol than shown by those containing other NR2 subunits. NR2A-containing NMDA receptors are particularly sensitive to other modulators of channel function, including heavy metals such as zinc. Although zinc inhibits NMDA receptors at micromolar concentrations through a voltage-dependent interaction with a channel site, NR2A-containing receptors are inhibited by low nanomolar concentrations of zinc in a voltage-independent manner. In this study, we examined the effects of ethanol on NR1/NR2A receptors expressed in human embryonic kidney 293 (HEK 293) cells recorded under conditions in which the effects of zinc are minimized. Under control conditions, ethanol (100 mM) inhibited peak and steady-state currents of NR1/2A receptors by 35%–40%. Inclusion of the heavy metal chelator ethylenediaminetetraacetic acid [(EDTA); 10 μM] or other chelating compounds in the experimental solution augmented NMDA-stimulated currents, as previously described. In the presence of EDTA (10 μM), the inhibition of NR1/2A currents by 100 mM ethanol was reduced to approximately 28%. As expected, currents recorded from cells expressing the NR1 subunit and a zinc-insensitive NR2A mutant (H128S) were not augmented by zinc chelators. In these cells, ethanol (100 mM) inhibited NMDA receptor currents by approximately 28%, and this inhibition was unaffected by EDTA. These results support the suggestion that low levels of zinc present in experimental solutions may affect the apparent ethanol sensitivity of NMDA receptors containing the NR2A subunit.