Functional relationship between neuron and glia in glutamatergic synapses

在本研究中，我们旨在阐明小脑和海马中谷氨酸能突触中神经元和胶质之间的功能关系。主要研究结果如下：1。谷氨酸转运体在小脑浦肯野细胞突触中的作用。谷氨酸转运体GLAST、GLT-1、EAAC1和EAAT4分布在小脑皮层兴奋性突触附近。GLAST和GLT-1在pc上的Bergmann胶质（BG）包裹性兴奋突触中表达，而EAAC1和EAAT4在浦肯野细胞中表达。利用缺乏这些转运体基因的突变小鼠，我们发现GLAST和GLT-1主要参与谷氨酸的摄取，谷氨酸在释放递质后的早期从突触间隙中涌出。相反，EAAT4的主要作用是去除在后期从胶质转运体摄取中逃逸的低浓度谷氨酸，从而防止递质溢出到邻近的突触。EAAC1的贡献是微不足道的。我们还表明，胶质谷氨酸转运蛋白（GLAST + GLT-1）在PC兴奋性突触周围表达过剩，并且仅需要其中的20%来保持epscs的快速动力学。神经胶质谷氨酸转运体在海马锥体细胞突触中的作用。使用一种新型的谷氨酸转运蛋白阻滞剂（TFB-TBOA）特异性抑制神经胶质谷氨酸转运蛋白，我们已经表明，持续摄取突触释放的谷氨酸对于保护海马锥体神经元免受NMDA受体介导的超兴奋性是必不可少的。这提示神经胶质谷氨酸转运体功能障碍参与了癫痫的发生。Ca^<2+>-可渗透AMPA受体对胶质过程形态的调控。以表达AMPA受体的人胶质瘤细胞系U-87 MG细胞为模型系统，我们已经表明，神经胶质细胞的细胞过程的延伸是通过操纵Ca^<2+>-可渗透AMPA受体的表达来调节的。少

In this study, we aimed to clarify the functional relationship between neuron and glia in glutamatergic synapses in the cerebellum and hippocampus. The main results are as follows :1.Roles of glutamate transporters in cerebellar Purkinje cell (PC) synapses.Four distinct glutamate transporters, GLAST, GLT-1, EAAC1 and EAAT4, are distributed near excitatory synapses in cerebellar PCs. GLAST and GLT-1 are expressed in Bergmann glia (BG) wrapping excitatory synapses on PCs, whereas EAAC1 and EAAT4 are expressed in Purkinje cells. Using mutant mice deficient in these transporter genes, we have shown that GLAST and GLT-1 contribute mainly to uptake of glutamate that floods out of the synaptic cleft at early times after transmitter release. In contrast, the main role of EAAT4 is to remove low concentrations of glutamate that escape from the uptake by glial transporters at late times and thus to prevent the transmitter from spilling over to neighboring synapses. The contribution of EAAC1 was n … More egligible. We have also shown that glial glutamate transporters (GLAST plus GLT-1) are expressed in surplus around PC excitatory synapses, and that only 20% of them are needed to retain the fast kinetics of EPSCs.2.Roles of glial glutamate transporters in hippocampal pyramidal cell synapses.Using a novel glutamate transporter blocker (TFB-TBOA) that specifically suppresses glial glutamate transporters, we have shown that the continuous uptake of synaptically released glutamate is indispensable for protecting hippocampal pyramidal neurons from NMDA receptor-mediated hyper-excitabilities. This suggests that dysfunction of glial glutamate transporters is involved in the genesis of epilepsy.3.Regulation of the morphology of glial processes by Ca^<2+>-permeable AMPA receptors.Using a human glioma cell line U-87 MG cells expressing AMPA receptors as a model system, we have shown that the extension of cellular processes of glial cells is regulated by manipulating expression of Ca^<2+>-permeable AMPA receptors. Less