EXCITATORY SYNAPTIC SIGNALING BY GLUTAMATE TRANSPORTERS

描述：(申请人摘要) 谷氨酸转运体在兴奋性突触中发挥重要作用 通过帮助终止兴奋性信号来影响大脑。根据他们的分子 多样性，独特的表达方式和调制倾向，它 似乎谷氨酸转运体在体内扮演着额外的、更活跃的角色 兴奋性突触功能。然而，他们对 兴奋性信号仍未被研究。我们研究的总体目标 是了解完整突触的谷氨酸转运蛋白功能，以及 定义转运体在兴奋性信号中的作用。 该方案将全细胞电生理技术应用于大脑。 切片将重点放在平行纤维(PF)到 浦肯野神经元(PN)突触位于小脑。PF突触受一种 一种依赖于活性的可塑性形式，由G- 蛋白偶联谷氨酸受体(MGluR1a)。这种受体类型是共同定位的 PN树突上存在突触后谷氨酸转运体。收盘 这两个分子的排列增加了谷氨酸 转运蛋白通过限制胞外谷氨酸控制mGluRla活性 集中在PF突触。提案中的每一项目标都明确 阐述了这一假说的一个组成部分。第一个目标是考察 在突触后谷氨酸转运体限制谷氨酸浓度 PF突触活性。第二个目的是研究阻断谷氨酸的效果。 谷氨酸在突触上的转运和调节 激活mGluR1a。第三个目的是测试mGluRla是否调节谷氨酸 运输，一个假想的负反馈环路，有望调节突触 PF突触的可塑性。这些实验阐明了一种新的机制 控制大脑兴奋回路中依赖经验的变化。 这些发现还应该有助于更好地理解谷氨酸突触 并提供与兴奋性功能障碍相关的疾病的洞察 传播，如癫痫和肌萎缩侧索硬化症。

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.