Hatton Christopher J, Paoletti Pierre
Laboratoire de Neurobiologie, CNRS UMR 8544, Ecole Normale Supérueure, Paris, France.
Neuron. 2005 Apr 21;46(2):261-74. doi: 10.1016/j.neuron.2005.03.005.
NMDA receptors (NMDARs) are heteromeric assemblies of NR1 and NR2(A-D) subunits with properties heavily influenced by the type of NR2 subunit incorporated. While NMDARs with only one type of NR2 subunit have been extensively characterized, little is known about receptors containing two different NR2 subunits, despite compelling evidence that such triheteromeric receptors exist in vivo. We used a point-mutation approach that allows isolation of recombinant triheteromeric NMDARs possessing two different NR2 N-terminal domains (NTDs). We show that in receptors associating the NR2A-NTD (sensing nanomolar Zn) and the NR2B-NTD (sensing ifenprodil), each NTD binding site retains selective high affinity for its ligand. However, each ligand produces only partial inhibition, and maximal inhibition requires occupancy of both NR2-NTDs by their respective ligands. Similarly, NR1/2A/2C receptors are inhibited by zinc with high potency but low efficacy. Therefore, interactions between homologous N-terminal domains determine the unique pharmacological properties of triheteromeric NMDARs.
N-甲基-D-天冬氨酸受体（NMDARs）是由NR1和NR2（A-D）亚基组成的异源聚体，其特性受所包含的NR2亚基类型的严重影响。虽然仅含有一种类型NR2亚基的NMDARs已得到广泛表征，但对于含有两种不同NR2亚基的受体却知之甚少，尽管有确凿证据表明这种三异源受体在体内存在。我们采用了一种点突变方法，该方法能够分离出具有两个不同NR2 N端结构域（NTDs）的重组三异源NMDARs。我们发现，在结合了NR2A-NTD（感知纳摩尔浓度的锌）和NR2B-NTD（感知艾芬地尔）的受体中，每个NTD结合位点对其配体都保持选择性高亲和力。然而，每种配体仅产生部分抑制作用，最大抑制作用需要其各自的配体占据两个NR2-NTDs。同样，NR1/2A/2C受体对锌的抑制作用具有高效力但低效能。因此，同源N端结构域之间的相互作用决定了三异源NMDARs独特的药理学特性。
