The Glutamate Transporter EAAT4 in Rat Cerebellar Purkinje Cells: A Glutamate-Gated Chloride Channel Concentrated near the Synapse in Parts of the Dendritic Membrane Facing Astroglia
The Glutamate Transporter EAAT4 in Rat Cerebellar Purkinje Cells: A Glutamate-Gated Chloride Channel Concentrated near the Synapse in Parts of the Dendritic Membrane Facing Astroglia
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DOI：
10.1523/jneurosci.18-10-03606.1998
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发表时间：
1998-05
期刊：
影响因子：
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通讯作者：
Y. Dehnes;F. Chaudhry;K. Ullensvang;K. P. Lehre;J. Storm-Mathisen;N. Danbolt
中科院分区：
文献类型：
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作者：
Y. Dehnes;F. Chaudhry;K. Ullensvang;K. P. Lehre;J. Storm-Mathisen;N. Danbolt
兴奋性氨基酸转运蛋白 (EAAT4) 的抗体在小脑中强烈标记约 65 kDa 的糖蛋白，在前脑中标记较弱。小脑蛋白在溶解前与双（磺基琥珀酰亚胺基）辛二酸酯交联，导致 EAAT4 的二聚体带以及其他谷氨酸转运蛋白 GLAST (EAAT1) 和 GLT (EAAT2) 的二聚体和三聚体带出现在免疫印迹上。与 GLAST、GLT 和 EAAC (EAAT3) 相比，EAAT4 在小脑分子层中分布不均匀，在矢状旁区强烈表达。它位于小脑浦肯野细胞中，在表达高水平斑蛋白 II（醛缩酶 C）的细胞中浓度最高。浦肯野细胞刺和细树突的标记比大直径树突和细胞体的标记更强。 EAAT4 在突触膜中浓度较低，但与面向神经元膜的部分相比，在面向星形胶质细胞（表达 GLAST 和 GLT）的树突和棘膜部分高度富集，表明与神经胶质谷氨酸转运蛋白存在功能关系。细胞内池和多泡细胞器中 EAAT4 的存在可能反映了质膜中转运蛋白的周转。浦肯野细胞脊柱总表面和分子层中的 EAAT4 浓度分别为 1.1 m2/cm3 和 0.2 mg/cm3，相当于 1800 个分子/μm2。 EAAT4 的突触旁位置可以解释预测浦肯野细胞棘突触释放位点附近神经元谷氨酸转运蛋白存在的电生理学观察结果。 EAAT4 可能作为联合转运蛋白和抑制性谷氨酸受体发挥作用。
Antibodies to an excitatory amino acid transporter (EAAT4) label a glycoprotein of ∼65 kDa strongly in the cerebellum and weakly in the forebrain. Cross-linking of cerebellar proteins with bis(sulfosuccinimidyl) suberate before solubilization causes dimer bands of EAAT4 and both dimer and trimer bands of the other glutamate transporters GLAST (EAAT1) and GLT (EAAT2) to appear on immunoblots. In contrast to GLAST, GLT, and EAAC (EAAT3), EAAT4 is unevenly distributed in the cerebellar molecular layer, being strongly expressed in parasagittal zones. It is located in cerebellar Purkinje cells, and the highest concentrations are seen in ones expressing high levels of zebrin II (aldolase C). The labeling of Purkinje cell spines and thin dendrites is stronger than that of large diameter dendrites and cell bodies. EAAT4 is present at low concentrations in the synaptic membrane, but is highly enriched in the parts of the dendritic and spine membranes facing astrocytes (which express GLAST and GLT) compared with parts facing neuronal membranes, suggesting a functional relationship with glial glutamate transporters. The presence of EAAT4 in intracellular cisterns and multivesicular organelles may reflect turnover of transporter in the plasma membrane. The total Purkinje cell spine surface and the EAAT4 concentration were found to be 1.1 m2/cm3 and 0.2 mg/cm3, respectively, in the molecular layer, corresponding to 1800 molecules/μm2. The juxtasynaptic location of EAAT4 may explain electrophysiological observations predicting the presence of a neuronal glutamate transporter near the release site at a Purkinje cell spine synapse. EAAT4 may function as a combined transporter and inhibitory glutamate receptor.