METABOTROPIC GLUTAMATE RECEPTORS IN NEUROTOXICITY

代谢型谷氨酸受体（metabotropic glutamate receptor，mGluRs）是G蛋白偶联受体家族，其参与突触传递的调节、突触可塑性和神经毒性。该提议集中于I组mGluRs，其特征在于它们与磷脂酶C和细胞内Ca2+释放的偶联。尽管结构相似，但这些受体显示出功能异质性，这可以在受体表达模式、其药理学性质和各种细胞内信号级联的激活中观察到。最近，我们已经确定了它们在异源系统中表达时诱导凋亡性细胞死亡的差异能力。该提议的主要目标是明确地确定观察到的特定I组mGluRs诱导细胞凋亡的差异能力不限于特定表达系统，而是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其表达水平的反映，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组受体的相对量，并通过实验改变这些受体的表达。(2)确定特定I组mGluR诱导神经元和神经胶质细胞的天然群体中的细胞凋亡的能力。(3)确定特定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。我们将使用原代培养的不同群体的神经元和神经胶质细胞，以确定是否mGluR1的表达，而不是mGluR5受体导致细胞凋亡。 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原代培养物的实验。这些研究将使我们能够确定mGluRs可能发挥的作用，在触发机制的表达天然代谢型谷氨酸受体的人群中的细胞凋亡，并实现更好地了解谷氨酸的神经毒性作用，这有助于神经元细胞死亡。

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.