Vollum Institute, Oregon Health and Science University, Portland, Oregon, United States of America.
PLoS One. 2011 Apr 22;6(4):e19180. doi: 10.1371/journal.pone.0019180.
The N-methyl-D-aspartate (NMDA) receptor, an obligate heterotetrameric assembly organized as a dimer of dimers, is typically composed of two glycine-binding GluN1 subunits and two glutamate-binding GluN2 subunits. Despite the crucial role that the NMDA receptor plays in the nervous system, the specific arrangement of subunits within the dimer-of-dimer assemblage is not conclusively known. Here we studied the organization of the amino terminal domain (ATD) of the rat GluN1/GluN2A and GluN1/GluN2B NMDA receptors by cysteine-directed, disulfide bond-mediated cross-linking. We found that GluN1 ATDs and GluN2 ATDs spontaneously formed disulfide bond-mediated dimers after introducing cysteines into the L1 interface of GluN2A or GluN2B ATD. The formation of dimer could be prevented by knocking out endogenous cysteines located near the L1 interface of GluN1. These results indicate that GluN1 and GluN2 ATDs form local heterodimers through the interactions in the L1-L1 interface and further demonstrate a dimer-of-heterodimer arrangement in GluN1/GluN2A and GluN1/GluN2B NMDA receptors.
N-甲基-D-天冬氨酸（NMDA）受体是一种必需的异四聚体组装体，组织为二聚体的二聚体，通常由两个甘氨酸结合的 GluN1 亚基和两个谷氨酸结合的 GluN2 亚基组成。尽管 NMDA 受体在神经系统中起着至关重要的作用，但二聚体-二聚体组装体中亚基的具体排列尚不清楚。在这里，我们通过半胱氨酸定向、二硫键介导的交联研究了大鼠 GluN1/GluN2A 和 GluN1/GluN2B NMDA 受体的氨基末端结构域（ATD）的组织。我们发现，在 GluN2A 或 GluN2B ATD 的 L1 界面中引入半胱氨酸后，GluN1 ATD 和 GluN2 ATD 会自发形成二硫键介导的二聚体。通过敲除 GluN1 中靠近 L1 界面的内源性半胱氨酸可以阻止二聚体的形成。这些结果表明，GluN1 和 GluN2 ATD 通过 L1-L1 界面的相互作用形成局部异二聚体，并进一步证明 GluN1/GluN2A 和 GluN1/GluN2B NMDA 受体中存在二聚体-异二聚体排列。
