The glutamate transporter GLT1a is expressed in excitatory axon terminals of mature hippocampal neurons
The glutamate transporter GLT1a is expressed in excitatory axon terminals of mature hippocampal neurons
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DOI：
10.1523/jneurosci.1586-03.2004
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发表时间：
2004-02-04
影响因子：
5.3
通讯作者：
Rosenberg, PA
中科院分区：
文献类型：
--
作者：
Chen, WZ;Mahadomrongkul, V;Rosenberg, PA
GLT1 是大脑的主要谷氨酸转运蛋白，被认为仅在星形胶质细胞中表达。尽管兴奋性轴突末端吸收谷氨酸，但负责的转运蛋白尚未确定。 GLT1 在 C 末端以至少两种不同的形式表达，即 GLT1a 和 GLT1b。 GLT1 mRNA 已在神经元中得到证实，但没有相关蛋白。最近，使用特定的 C 末端定向抗体提供了证据，表明 GLT1b 蛋白在体内神经元中表达。这些数据表明，在神经元中检测到的 GLT1 mRNA 编码 GLT1b，并且 GLT1b 可能是难以捉摸的突触前转运蛋白。为了测试这些假设，我们使用针对 GLT1a 和 GLT1b 3'-非翻译区的变体特异性探针在海马中进行原位杂交。与预期相反，GLT1a mRNA 的形式更为丰富。为了进一步研究 GLT1 在海马神经元中的表达，针对 GLT1a C 末端和 GLT1 N 末端产生的抗体（通过在 GLT1 敲除小鼠中测试发现具有特异性）用于光学显微镜和 EM-ICC。 GLT1a 蛋白在神经元中检测到，在海马区 14-29% 的轴突中检测到，具体取决于区域。许多标记的轴突形成轴突、不对称，因此形成兴奋性突触。一些刺和树突也发生了标记。针对 GLT1 N 末端的抗体也产生神经元过程的标记。因此，GLT1 的最初克隆形式 GLT1a 在成熟海马的神经元中表达为蛋白质，并且可能对兴奋性末梢的谷氨酸摄取有显着贡献。
GLT1 is the major glutamate transporter of the brain and has been thought to be expressed exclusively in astrocytes. Although excitatory axon terminals take up glutamate, the transporter responsible has not been identified. GLT1 is expressed in at least two forms varying in the C termini, GLT1a and GLT1b. GLT1 mRNA has been demonstrated in neurons, without associated protein. Recently, evidence has been presented, using specific C terminus-directed antibodies, that GLT1b protein is expressed in neurons in vivo. These data suggested that the GLT1 mRNA detected in neurons encodes GLT1b and also that GLT1b might be the elusive presynaptic transporter. To test these hypotheses, we used variant-specific probes directed to the 3'-untranslated regions for GLT1a and GLT1b to perform in situ hybridization in the hippocampus. Contrary to expectation, GLT1a mRNA was the more abundant form. To investigate further the expression of GLT1 in neurons in the hippocampus, antibodies raised against the C terminus of GLT1a and against the N terminus of GLT1, found to be specific by testing in GLT1 knock-out mice, were used for light microscopic and EM-ICC. GLT1a protein was detected in neurons, in 14-29% of axons in the hippocampus, depending on the region. Many of the labeled axons formed axo-spinous, asymmetric, and, thus, excitatory synapses. Labeling also occurred in some spines and dendrites. The antibody against the N terminus of GLT1 also produced labeling of neuronal processes. Thus, the originally cloned form of GLT1, GLT1a, is expressed as protein in neurons in the mature hippocampus and may contribute significantly to glutamate uptake into excitatory terminals.