EXCITATORY SYNAPTIC SIGNALING BY GLUTAMATE TRANSPORTERS

描述：（申请人摘要） 谷氨酸转运蛋白在神经元兴奋性突触中发挥重要作用， 通过帮助终止兴奋信号来刺激大脑。基于其分子 多样性，不同的表达模式和调制倾向，它 谷氨酸转运蛋白似乎在细胞内起着额外的，更积极的作用。 兴奋性突触功能然而，他们的潜在贡献， 兴奋性信号传导仍然未被探索。我们研究的广泛目标 是了解谷氨酸转运蛋白在完整突触中的功能， 定义转运蛋白在兴奋性信号传导中的作用。 该方案采用全细胞电生理技术应用于脑 切片集中在平行纤维（PF）的谷氨酸转运蛋白， 小脑中的浦肯野神经元（PN）突触。PF突触由一种 一种依赖于活动的可塑性，由G- 蛋白偶联谷氨酸受体（mGluR 1a）。这种受体类型是共定位的 突触后谷氨酸转运蛋白存在于PN树突上。收盘 这两种分子的排列增加了谷氨酸 转运通过限制细胞外谷氨酸来控制mGluRla活性 PF突触的浓度。提案中的每一个目标都特别 解决了这个假设的一个组成部分。第一个目标是检查 突触后谷氨酸转运蛋白限制谷氨酸浓度 PF突触活动。第二个目的是研究阻断谷氨酸的作用 转运和操纵突触上谷氨酸浓度的作用 激活mGluRla。第三个目的是测试mGluRla是否调节谷氨酸 转运，一个假设的负反馈回路，预期调节突触 PF突触的可塑性这些实验阐明了一种新的机制， 控制大脑中兴奋回路的经验依赖性变化。 这些发现也将有助于我们更好地理解谷氨酸突触 并提供与兴奋性神经元功能障碍相关的疾病的见解， 癫痫和肌萎缩侧索硬化症等传染病。

DESCRIPTION: (Applicant's Abstract) Glutamate transporters perform an essential function at excitatory synapses in the brain by helping to terminate excitatory signals. Based on their molecular diversity, distinct patterns of expression and propensity for modulation, it seems likely that glutamate transporters play additional, more active roles in excitatory synaptic function. However, their potential contributions to excitatory signaling remain unexplored. The broad objectives of our research are to understand glutamate transporter function at intact synapses and to define roles for transporters in excitatory signaling. This proposal uses whole-cell electrophysiological techniques applied to brain slices to focus on glutamate transporters at the parallel fiber (PF) to Purkinje neuron (PN) synapse in the cerebellum. PF synapses are regulated by a form of activity-dependent plasticity which is triggered by activation of a G- protein coupled glutamate receptor (mGluR1a). This receptor type is colocalized with a postsynaptic glutamate transporter present on PN dendrites. The close arrangement of these two molecules raises the possibility that glutamate transport controls mGluRla activity by limiting extracellular glutamate concentration at PF synapses. Each of the aims in the proposal specifically addresses a component of this hypothesis. The first aim examines the degree to which postsynaptic glutamate transporters limit glutamate concentration during PF synaptic activity. The second aim examines the effects of blocking glutamate transport and of manipulating glutamate concentration on the synaptic activation of mGluRla. The third aim tests if mGluRla modulates glutamate transport, a hypothesized negative feedback loop expected to regulate synaptic plasticity at PF synapses. These experiments illuminate a novel mechanism for controlling experience-dependent changes in excitatory circuitry in the brain. The findings should also lead to a better understanding of glutamate synapses and provide insight into diseases associated with malfunctions in excitatory transmission such as epilepsy and Amyotrophic Lateral Sclerosis.