Tanaka J, Ichikawa R, Watanabe M, Tanaka K, Inoue Y
Department of Anatomy, Hokkaido University School of Medicine, Sapporo, Japan.
Neuroreport. 1997 Jul 28;8(11):2461-4. doi: 10.1097/00001756-199707280-00010.
We used silver-enhanced immunogold electron microscopy to reveal synaptic localization of the glutamate transporter EAAT4 in mouse cerebellar Purkinje cells (PCs). Gold-silver particles representing the EAAT4 were densely localized on extra-junctional membrane, but not on junctional membrane of PC spines in contact with parallel fiber or climbing fiber terminals. No particle accumulations were observed at inhibitory synapses formed on cell body and dendritic shafts of PCs. Therefore, the EAAT4 is selectively targeted to the extra-junctional site of excitatory PC synapses. The finding suggests that the EAAT4 transports glutamate or its related amino acids from outside the synaptic cleft, which would facilitate glutamate diffusion from the synaptic cleft to the extrasynaptic space and restrict glutamate spillover to adjacent synapses.
我们使用银增强免疫金电子显微镜来揭示谷氨酸转运体EAAT4在小鼠小脑浦肯野细胞（PCs）中的突触定位。代表EAAT4的金银颗粒密集地定位于结外膜，而不是与平行纤维或攀缘纤维终末接触的PC树突棘的结膜上。在PCs的细胞体和树突干上形成的抑制性突触处未观察到颗粒聚集。因此，EAAT4选择性地靶向兴奋性PC突触的结外部位。这一发现表明，EAAT4从突触间隙外转运谷氨酸或其相关氨基酸，这将促进谷氨酸从突触间隙扩散到突触外空间，并限制谷氨酸向相邻突触的溢出。
