REGULATION OF METABOTROPIC GLUTAMATE RECEPTOR RESPONSES

说明：谷氨酸是中枢神经系统中主要的兴奋性氨基酸，从轴突末端释放谷氨酸可激活两个不同的受体家族。代谢性谷氨酸受体(MGluRs)是其中的一个家族，它与多种GRP结合蛋白偶联，激活几个第二信使通路来调节细胞兴奋性和突触传递。由于mGluR在谷氨酸能突触形成净传递中的重要作用，了解参与调节mGluR反应的机制至关重要。一个被称为G蛋白信号调节因子(RGS)的新的蛋白质家族直接与G蛋白相互作用，以减弱G蛋白介导的反应并调节G蛋白信号。到目前为止，RGS蛋白对神经递质反应的调节还没有被解决。最近有报道，长期应用激动剂对mGluRs会导致一种长期脱敏的形式，这种脱敏不能通过磷酸化或受体的国际化和降解来解释。我们推测，RGS蛋白不仅可能调节中枢神经系统中的G蛋白通路，而且长期应用mGluR激动剂可能导致细胞内RGS蛋白水平的调节，从而导致神经元和神经胶质细胞中受体反应的脱敏。因此，本研究的目的是结合分子、生化和电生理方法，确定RGS蛋白对mGluR介导的反应的影响，以及mGluR激活对RGS蛋白细胞水平调节的影响。其具体目的是：(1)确定RGS7蛋白在异源表达系统中对mGluR反应的影响；(2)确定RGS蛋白对神经细胞mGluR反应的影响；(3)确定mGluR激活是否调节神经元中RGS mRNA和蛋白的表达水平；(4)确定mGluR激活是否调节神经胶质细胞中RGS mRNA和蛋白的表达水平。这些研究将对mGluR信号转导的细胞机制提供有价值的见解，并可能对开发治疗各种中枢神经系统疾病的新型治疗药物具有重要意义。

DESCRIPTION:(from applicant's abstract) Glutamate is the principal excitatory amino acid in the central nervous system and release of glutamate from axon terminals results in the activation of two distinct families of receptors. One of these families, the metabotropic glutamate receptors (mGluRs), coupled to a variety of GRP-binding (G) proteins and activate several second messenger pathways to regulate cell excitability and synaptic transmission. Because of the important roles of mGluRs in shaping net transmission at glutamatergic synapses, it is critical to understand the mechanisms involved in regulating mGluR responses. A new family of proteins termed RGS (regulators of G protein signaling) interact directly with G proteins to attenuate G protein-mediated responses and regulate G protein signaling. To date, the regulation of neurotransmitter responses by RGS proteins has not been addressed. It has recently been reported that the long-term application of agonists to mGluRs results in a form of long-term desensitization that is not accounted for by phosphorylation, or internationalization and degradation of the receptor. We hypothesize that RGS proteins may not only regulate G protein pathways in the central nervous system, but that long-term application of mGluR agonists may lead to the regulation of cellular levels of RGS proteins and the subsequent desensitization of receptor responses in neurons and glia. Thus the goal of this proposal is to determine the effects of RGS proteins on mGLuR- mediated responses and the effects of mGluR activation on the regulation of cellular levals of RGS proteins using a combination of molecular, biochemical and electrophysiological methods. The specific aims are to: (1) determine the effects of RGS7 protein on mGluR responses in heterologous expression systems, (2) determine the effects of RGS proteins on mGluR responses in neuronal cells, (3) determine whether mGluR activation regulates the cellular levels of expression of RGS mRNA and protein in neurons and (4) determine whether mGluR activation regulates the cellular levels of expression of RGS mRNA and protein in glial cells. These studies will provide valuable insight into the cellular mechanisms involvedin mGluR signaling and could have important implications for the development of novel therapeutic agents for the treatment of a variety of central nervous system disorders.