METABOTROPIC GLUTAMATE RECEPTORS IN NEUROTOXICITY

代谢性谷氨酸受体(MGluRs)是一类G蛋白偶联受体家族，参与突触传递、突触可塑性和神经毒性的调节。这项建议集中在第一类mGluRs，其特征是与磷脂酶C偶联和细胞内钙释放。尽管结构相似，但这些受体表现出功能上的异质性，这可以从受体的表达模式、它们的药理特性以及激活各种细胞内信号级联反应中观察到。最近，我们已经确定了它们在异源系统中表达时诱导细胞凋亡的不同能力。这项建议的主要目的是明确地确定，观察到的特定组mGluRs诱导细胞凋亡的分化能力不仅限于特定的表达系统，而且显著存在于神经元和神经胶质细胞的天然群体中。我们的目标也是确定mGluR1和mGluR5的不同毒性特性不仅仅是它们表达水平的反映，而是由这些受体的固有特性引起的。拟议的具体目标包括：(1)创建和测试必要的工具，使我们能够评估不同的I组受体在重组和天然系统中的相对数量，并在实验上修改这些受体的表达。(2)确定特定的I组mGluRs诱导神经细胞和神经胶质细胞群凋亡的能力。(3)确定特定的I组受体在具有神经元特性的细胞系和异源表达系统中诱导细胞凋亡的能力。我们将使用不同人群的神经元和神经胶质细胞的原代培养，以确定mGluR1的表达而不是mGluR5受体的表达是否会导致细胞凋亡。这些研究还将包括对从缺乏mGluR1或mGluR5受体的转基因动物获得的细胞进行原代培养的实验。这些研究将使我们能够确定mGluRs在表达天然代谢性谷氨酸受体的人群中可能在触发凋亡机制中所起的作用，并更好地理解谷氨酸导致神经细胞死亡的神经毒性作用。

Metabotropic glutamate receptors (mGluRs) are a family of G protein- coupled receptors which participate in modulation of synaptic transmission, in synaptic plasticity and neurotoxicity. This proposal focused on group I mGluRs which are characterized by their coupling to phospholipase C and intracellular Ca2+ release. Despite the structural similarities, these receptors show a functional heterogeneity which can be observed in the patterns of receptor expression, their pharmacological properties, and in the activation of various intracellular signaling cascades. Recently, we have determined their differential ability to induce apoptotic cell death when expressed in heterologous systems. The main goal of this proposal is to establish definitively that the observed differential ability of the particular group I mGluRs to induce apoptosis is not restricted to a specific expression system, but is significantly present in native populations of neuronal and glial cells. It is also our goal to determine that the different toxic properties of mGluR1 and mGluR5 are not a mere reflection of their expression levels but are caused by the inherent properties of these receptors. The proposed specific aims include: (1) To create and test the necessary tools that will allow us to evaluate the relative amounts of the different group I receptors in recombinant and native systems and to experimentally modify the expression of these receptors. (2) To determine the ability of particular group I mGluRs to induce apoptosis in native populations of neuronal and glial cells. (3) To determine the ability of the particular group I receptors to induce apoptosis in cell lines with neuronal properties and in heterologous expression systems. We will use primary cultures of different populations with neuronal and glial cells in order to establish whether the expression of mGluR1 but not of mGluR5 receptors leads to apoptosis. These studies will also include experiments with primary cultures of cell obtained from genetically modified animals lacking mGluR1 or mGluR5 receptors. These studies will allow us to determine the role that mGluRs may play in triggering the mechanisms of apoptosis in populations of expressing native metabotropic glutamate receptors and to achieve a better understanding of the neurotoxic actions of glutamate which contribute to neuronal cell death.