Retention of NMDA receptor NR2 subunits in the lumen of endoplasmic reticulum in targeted NR1 knockout mice
Retention of NMDA receptor NR2 subunits in the lumen of endoplasmic reticulum in targeted NR1 knockout mice
复制标题
DOI：
10.1073/pnas.0830996100
复制
发表时间：
2003-04-15
影响因子：
11.1
通讯作者：
Watanabe, M
中科院分区：
文献类型：
--
作者：
Fukaya, M;Kato, A;Watanabe, M
谷氨酸是哺乳动物中枢神经系统中的主要兴奋性神经递质，N-甲基-D-天冬氨酸选择性谷氨酸受体（NR）由NR 1亚基和NR 2或NR 3亚基组成，在突触传递、可塑性以及学习和记忆中起着关键作用。通过使用敲除小鼠品系，其中NR 1基因缺失主要针对海马CA 1锥体细胞，我们研究了NR 1亚基缺失对NR 2亚基的细胞表达和细胞内分布的体内影响。NR 1基因缺失对NR 2A和NR 2B mRNA水平无明显影响，但导致NR 2A和NR 2B蛋白在CA 1锥体细胞树突中的表达严重减少。NR 2亚基的这种减少的树突状分布伴随着它们在胞体中的大量积累，在那里它们作为电子致密颗粒凝聚在内质网的内腔中。在对照小鼠的CA 1锥体细胞中也观察到这些颗粒，但它们少得多，并且不含可检测水平的NR 2亚基。NR 1敲除对NR 2亚基的细胞内定位的影响是特异性的，因为对于GluR 1和PSD-95（另外两种主要的突触后蛋白）没有观察到这种影响。这些结果表明，NR 1亚基在海马锥体细胞内质网释放NR 2亚基中起着至关重要的作用，当NR 1亚基不可用时，NR 2亚基被保留并聚集成脑池内颗粒。
Glutamate is a major excitatory neurotransmitter in the mammalian central nervous system, and the N-methyl-D-aspartate-selective glutamate receptor (NR) consisting of the NR1 subunit and an NR2 or NR3 subunit plays crucial roles in synaptic transmission, plasticity, and learning and memory. By using a knockout mouse strain, in which the NR1 gene deletion is primarily targeted to the CA1 pyramidal cells of the hippocampus, we investigated the in vivo effect of the loss of the NR1 subunit on the cellular expression and intracellular distribution of the NR2 subunits. The NR1 gene deletion had no apparent effect on the levels of NR2A or NR2B mRNA but led to severe reductions of NR2A and NR2B protein in dendrites of CA1 pyramidal cells. This reduced dendritic distribution of the NR2 subunits accompanied their robust accumulation in perikarya, where they were condensed in the lumen of the endoplasmic reticulum as electron-dense granules. These granules were also observed in CA1 pyramidal cells of the control mice but they were much fewer and contained no detectable levels of the NR2 subunit. The effect of the NR1 knockout on intracellular localization of the NR2 subunits was specific in that no such effect was observed for the GluR1 and PSD-95, two other major postsynaptic proteins. These results suggest that the NR1 subunit plays a crucial role in the release of the NR2 subunit from the endoplasmic reticulum in hippocampal pyramidal cells in vivo, and when the NR1 subunit is unavailable, the NR2 subunits are retained and aggregate into intracisternal granules.