METABOTROPIC GLUTAMATE RECEPTORS IN NEUROTOXICITY

代谢性谷氨酸受体（mGluRs）是一类G蛋白偶联受体，参与突触传递调节、突触可塑性和神经毒性。本研究的重点是I组mGluRs，其特征是与磷脂酶C和细胞内Ca2+释放偶联。尽管结构相似，但这些受体在受体表达模式、药理特性和各种细胞内信号级联的激活方面表现出功能异质性。最近，我们已经确定了它们在异种系统中表达时诱导凋亡细胞死亡的差异能力。本研究的主要目的是明确证实，观察到的特定I组mGluRs诱导细胞凋亡的差异能力并不局限于特定的表达系统，而是显著存在于天然的神经元和胶质细胞群体中。我们的目标是确定mGluR1和mGluR5的不同毒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。提出的具体目标包括：(1)创建和测试必要的工具，使我们能够评估重组和天然系统中不同I组受体的相对数量，并通过实验修改这些受体的表达。(2)确定特定I组mGluRs诱导天然神经细胞和胶质细胞凋亡的能力。(3)确定特定的I组受体在具有神经元性质的细胞系和异源表达系统中诱导细胞凋亡的能力。我们将使用不同群体的神经细胞和胶质细胞的原代培养，以确定mGluR1而非mGluR5受体的表达是否会导致细胞凋亡。这些研究还将包括从缺乏mGluR1或mGluR5受体的转基因动物中获得的细胞的原代培养实验。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群体中触发细胞凋亡机制中可能发挥的作用，并更好地了解谷氨酸导致神经元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.