C-terminal Domains of N-Methyl-D-aspartic Acid Receptor Modulate Unitary Channel Conductance and Gating
C-terminal Domains of N-Methyl-D-aspartic Acid Receptor Modulate Unitary Channel Conductance and Gating
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DOI：
10.1074/jbc.m112.390013
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发表时间：
2012-10-19
影响因子：
4.8
通讯作者：
Popescu, Gabriela K.
中科院分区：
文献类型：
--
作者：
Maki, Bruce A.;Aman, Teresa K.;Popescu, Gabriela K.
NMDA受体（NRs）是谷氨酸门控的钙离子通道，在正常突触传递中起重要作用，并参与神经退行性变。四聚体蛋白由两个专性GluN 1（N1）和两个GluN 2（N2）亚基组成，其中GluN 2A（2A）和GluN 2B（2B）在成人脑中普遍存在。位于细胞内的C-末端结构域（CTD）是受体的重要组成部分，对可塑性和兴奋性毒性至关重要，但其功能尚未完全确定。最近的证据表明，截断的N2 CTD改变通道动力学;然而，发生这种情况的机制尚不清楚。在这里，我们记录了缺乏N1，2A或2B CTD的单个NR的活性，并确定了这些受体的门控机制。缺乏N1 CTD的受体具有更大的单位电导和更快的失活动力学，缺乏2A或2B CTD的受体具有更长的开口和更长的脱敏间隔，N2 CTD的前100个氨基酸对这些变化至关重要。此外，缺乏2A或2B的CTD的受体保持同种型特异性动力学差异，并且在2A和2B之间交换CTD对单通道特性没有影响。基于这些结果，我们认为CTD中的扰动可以以亚基依赖性的方式修饰NR介导的信号，在2A中，这些效应最有可能是由膜近端残基介导的，并且2A和2B赋予的亚型特异性生物物理特性是CTD独立的。我们开发的动力学机制提供了一个定量的方法来了解NR亚基的细胞内结构域如何调节受体的反应。
NMDA receptors (NRs) are glutamate-gated calcium-permeable channels that are essential for normal synaptic transmssion and contribute to neurodegeneration. Tetrameric proteins consist of two obligatory GluN1 (N1) and two GluN2 (N2) subunits, of which GluN2A (2A) and GluN2B (2B) are prevalent in adult brain. The intracellularly located C-terminal domains (CTDs) make a significant portion of mass of the receptors and are essential for plasticity and excitotoxicity, but their functions are incompletely defined. Recent evidence shows that truncation of the N2 CTD alters channel kinetics; however, the mechanism by which this occurs is unclear. Here we recorded activity from individual NRs lacking the CTDs of N1, 2A, or 2B and determined the gating mechanisms of these receptors. Receptors lacking the N1 CTDs had larger unitary conductance and faster deactivation kinetics, receptors lacking the 2A or 2B CTDs had longer openings and longer desensitized intervals, and the first 100 amino acids of the N2 CTD were essential for these changes. In addition, receptors lacking the CTDs of either 2A or 2B maintained isoform-specific kinetic differences and swapping CTDs between 2A and 2B had no effect on single-channel properties. Based on these results, we suggest that perturbations in the CTD can modify the NR-mediated signal in a subunit-dependent manner, in 2A these effects are most likely mediated by membrane-proximal residues, and the isoform-specific biophysical properties conferred by 2A and 2B are CTD-independent. The kinetic mechanisms we developed afford a quantitative approach to understanding how the intracellular domains of NR subunits can modulate the responses of the receptor.