EAAC1, a high-affinity glutamate transporter, is localized to astrocytes and gabaergic neurons besides pyramidal cells in the rat cerebral cortex
EAAC1, a high-affinity glutamate transporter, is localized to astrocytes and gabaergic neurons besides pyramidal cells in the rat cerebral cortex
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DOI：
10.1093/cercor/8.2.108
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发表时间：
1998-03-01
期刊：
影响因子：
3.7
通讯作者：
Melone, M
中科院分区：
文献类型：
--
作者：
Conti, F;DeBiasi, S;Melone, M
谷氨酸从突触间隙的高亲和力摄取在生理和病理条件下调节神经元活动中起着至关重要的作用。我们已经使用亲和纯化的特异性多克隆抗体提出了对合成肽对应的C-末端区域的兔和大鼠EAAC 1。谷氨酸（Glu）转运蛋白，被认为是专门的神经元，研究其细胞和亚细胞定位，以及它是否只在颗粒下层的谷氨酸能细胞中表达，如以前的研究所建议的。光镜研究表明，EAAC 1免疫反应（IR）是本地化的神经元和点状元素的神经元。EAAC 1阳性神经元在II-III层和V-VI层中数量更多，即在所有投射层中。大多数EAAC 1阳性神经元是锥体细胞，虽然也观察到非锥体细胞。一些EAAC 1阳性的非锥体神经元用GAD的抗血清染色阳性，从而证明EAAC 1并不局限于海马神经元。在白色物质中也观察到非神经元EAAC 1阳性细胞，其中一些细胞用GFAP抗血清染色呈阳性。超微结构研究表明EAAC 1-ir分布于神经元胞体、树突和树突棘。但不在轴突终末，即仅在突触后。对EAAC 1-IR谱图上突触轴突终末类型的分析表明，97%的轴突终末形成不对称接触，从而表明EAAC 1位于兴奋性氨基酸释放的非常位点。出乎意料的是，EAAC 1-ir也被发现在一些星形胶质细胞的过程中位于灰色和白色的问题。EAAC 1的定位可以解释EAAC敲除后的病理症状（癫痫发作和轻度毒性），因为癫痫发作可能是由于EAAC 1介导的轴树突和轴棘突触神经元兴奋性的精细调节的丧失，而轻度毒性可能与星形胶质细胞EAAC 1的功能失活有关。
High-affinity uptake of glutamate from the synaptic cleft plays a crucial role in regulating neuronal activity in physiological and pathological conditions. We have used affinity-purified specific polyclonal antibodies raised against a synthetic peptide corresponding to the C-terminal region of rabbit and rat EAAC1. a glutamate (Glu) transporter believed to be exclusively neuronal, to investigate its cellular and subcellular localization and whether it is expressed exclusively in glutamatergic cells of infragranular layers, as suggested by previous studies. Light microscopic studies revealed that EAAC1 immunoreactivity (ir) is localized to neurons and punctate elements in the neuropil. EAAC1-positive neurons were more numerous in layers II-III and V-VI, i.e. throughout all projection layers. Most EAAC1-positive neurons were pyramidal, although nonpyramidal cells were also observed. Some EAAC1-positive non-pyramidal neurons stained positively with an antiserum to GAD, thus demonstrating that EAAC1 is not confined to glutamatergic neurons. Non-neuronal EAAC1-positive cells were also observed in the white matter, and some of them stained positively with an antiserum to GFAP. Ultrastructural studies showed that EAAC1-ir was in neuronal cell bodies, dendrites and dendritic spines. but not in axon terminals, i.e. exclusively postsynaptic. Analysis of the type of axon terminals synapsing on EAAC1-ir profiles showed that 97% of them formed asymmetric contacts, thus indicating that EAAC1 is located at the very sites of excitatory amino acid release. Unexpectedly, EAAC1-ir was also found in a few astrocytic processes located in both the gray and the white matter. The localization of EAAC1 may explain the pathological symptoms that follow EAAC knockout (seizures and mild toxicity), as seizures could be due to the loss of EAAC1-mediated fine regulation of neuronal excitability at axodendritic and axospinous synapses, whereas the mild toxicity may be related to the functional inactivation of astrocytic EAAC1.