Rutter A R, Stephenson F A
Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University of London, London, England.
J Neurochem. 2000 Dec;75(6):2501-10. doi: 10.1046/j.1471-4159.2000.0752501.x.
Coexpression in human embryonic kidney (HEK) 293 cells of the postsynaptic density-95 protein (PSD-95) with NMDA receptor NR2A or NR2B single subunits or NR1-1a/NR2A and NR1-1a/NR2B subunit combinations induced an approximately threefold increase in NR2A and NR2B subunit expression. Deletion of the NR2 C-terminal ESDV motifs resulted in the loss of this increase following coexpression of NR1-1a/NR2A(Trunc) and NR1-1a/NR2B(Trunc) with PSD-95. Characterisation of the radioligand binding properties of [(3)H]MK-801 to NR1-1a/NR2A receptors with or without PSD-95 showed that PSD-95 induced a threefold increase in B:(max) values and an apparent approximately fivefold decrease in affinity in the presence of 10 microM: L-glutamate. In the presence of 1 mM: L-glutamate, the K:(i) for MK-801 binding to NR1-1a/NR2A with PSD-95 was not significantly different from that for NR1-1a/NR2A without PSD-95. The EC(50) value for the enhancement of [(3)H]MK-801 binding by L-glutamate to NR1-1a/NR2A was 1.8 +/- 0.4 (n = 4) and 8.9 (mean of n = 2) microM: in the absence and presence of PSD-95, respectively. Thus, coexpression of PSD-95 with NR1-1a/NR2A results in a decreased sensitivity to L-glutamate and an enhanced expression of NR2A and NR2B subunits. Deletion studies show that this effect is mediated via interaction of the C-terminal ESDV motif of the NR2 subunit with PSD-95.
在人胚肾（HEK）293细胞中，将突触后致密蛋白95（PSD - 95）与NMDA受体NR2A或NR2B单个亚基或NR1 - 1a/NR2A和NR1 - 1a/NR2B亚基组合共表达，可使NR2A和NR2B亚基表达增加约三倍。在将NR1 - 1a/NR2A(Trunc)和NR1 - 1a/NR2B(Trunc)与PSD - 95共表达后，缺失NR2 C末端的ESDV基序导致这种增加消失。对[(3)H]MK - 801与有无PSD - 95的NR1 - 1a/NR2A受体的放射性配体结合特性进行表征，结果表明，在存在10 microM L - 谷氨酸的情况下，PSD - 95使B:(max)值增加了三倍，亲和力明显降低了约五倍。在存在1 mM L - 谷氨酸的情况下，MK - 801与有PSD - 95的NR1 - 1a/NR2A结合的K:(i)与无PSD - 95的NR1 - 1a/NR2A相比无显著差异。在无PSD - 95和有PSD - 95的情况下，L - 谷氨酸增强[(3)H]MK - 801与NR1 - 1a/NR2A结合的EC(50)值分别为1.8±0.4（n = 4）和8.9（n = 2的平均值） microM。因此，PSD - 95与NR1 - 1a/NR2A共表达导致对L - 谷氨酸的敏感性降低以及NR2A和NR2B亚基表达增强。缺失研究表明，这种效应是通过NR2亚基的C末端ESDV基序与PSD - 95相互作用介导的。
