NMDA receptor subunits GluRepsilon1, GluRepsilon3 and GluRzeta1 are enriched at the mossy fibre-granule cell synapse in the adult mouse cerebellum.
NMDA receptor subunits GluRepsilon1, GluRepsilon3 and GluRzeta1 are enriched at the mossy fibre-granule cell synapse in the adult mouse cerebellum.
复制标题
NMDA 受体亚基 GluRepsilon1、GluRepsilon3 和 GluRzeta1 在成年小鼠小脑的苔藓纤维颗粒细胞突触处富集。
DOI：
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发表时间：
2001
影响因子：
3.4
通讯作者：
M. Watanabe
中科院分区：
文献类型：
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作者：
K. Yamada;M. Fukaya;H. Shimizu;K. Sakimura;M. Watanabe
小脑N-甲基-D-天冬氨酸（NMDA）受体集中在颗粒层，并参与运动协调和苔藓纤维-颗粒细胞突触长时程增强的诱导。在本研究中，我们用免疫组织化学方法研究NMDA受体亚单位在成年小鼠小脑的分布。我们发现，适当的胃蛋白酶预处理切片大大提高免疫组化检测的敏感性和特异性。结果，GluRepsilon 1（NR 2A）、GluRepsilon 3（NR 2C）和GluRzeta 1（NR 1）的强烈免疫标记均出现在颗粒层的突触肾小球中。双重免疫荧光显示，这些亚基共定位在个别突触肾小球。在肾小球内，NMDA受体亚单位位于中央巨大的苔藓纤维终端和外围位于微小的高尔基体轴突终端之间。通过免疫电镜，所有三个亚基检测到颗粒细胞树突的突触后连接，形成突触苔藓纤维终端。与已知的功能定位相一致，GluRepsilon 1，GluRepsilon 3和GluRzeta 1，因此，解剖学上集中在苔藓纤维颗粒细胞突触。相比之下，浦肯野细胞胞体和树突的分子层的免疫组织化学信号非常低。浦肯野细胞中缺乏GluRzeta 1免疫标记是出乎意料的，因为细胞表达高水平的GluRzeta 1 mRNA，并且免疫印迹显示分子层中存在高水平的GluRzeta 1蛋白。由于浦肯野细胞异常缺乏GluRzeta 1的表达，差异的结果可能提供体内证据，表明伴随GluRzeta 1亚基在GluRzeta 1的突触定位中的重要性。
Cerebellar N-methyl-D-aspartate (NMDA) receptors are concentrated in the granular layer and are involved in motor coordination and the induction of long-term potentiation at mossy fibre-granule cell synapses. In the present study, we used immunohistochemistry to examine the distribution of NMDA receptor subunits in the adult mouse cerebellum. We found that appropriate pepsin pretreatment of sections greatly enhanced the sensitivity and specificity of immunohistochemical detection. As a result, intense immunolabelling for GluRepsilon1 (NR2A), GluRepsilon3 (NR2C), and GluRzeta1 (NR1) all appeared in synaptic glomeruli of the granular layer. Double immunofluorescence showed that these subunits were colocalized in individual synaptic glomeruli. Within the glomerulus, NMDA receptor subunits were located between centrally-located huge mossy fibre terminals and peripherally-located tiny Golgi axon terminals. By immunoelectron microscopy, all three subunits were detected at the postsynaptic junction in granule cell dendrites, forming synapses with mossy fibre terminals. Consistent with the known functional localization, GluRepsilon1, GluRepsilon3, and GluRzeta1 are, thus, anatomically concentrated at the mossy fibre-granule cell synapse. By contrast, immunohistochemical signals were very low in Purkinje cell somata and dendrites in the molecular layer. The lack of GluRzeta1 immunolabelling in Purkinje cells was unexpected because the cells express GluRzeta1 mRNA at high levels and high levels of GluRzeta1 protein in the molecular layer were revealed by immunoblot. As Purkinje cells are exceptionally lacking GluRepsilon expression, the discrepant result may provide in vivo evidence suggesting the importance of accompanying GluRepsilon subunits in synaptic localization of GluRzeta1.