Heterogeneity of Synaptic NMDA Receptors

描述(申请人提供)：N-甲基-D-天冬氨酸受体(NMDAR)NR2亚单位编码基因在发育过程中的顺序表达产生了一系列事件，导致NMDA通道的表达根据它们所扮演的生理角色的动力学特性而量身定做。在这次竞争性更新中，我们建议继续利用电生理学、分子生物学和解剖学技术来研究兴奋性突触的异质性。我们过去的研究表明，NMDAR亚型对控制小脑突触功能特性的亚型具有选择性调节作用。基于这些结果，我们将研究小脑颗粒细胞(CGCs)突触和突触外NMDAR的多样性对兴奋性突触传递和小脑皮质信息流控制的影响。CGCs提供了对NMDAR介导的突触电流进行高分辨率膜片钳记录的独特可能性，并具有单通道电流的分辨率。长时程增强(LTP)和长时程抑制(LTD)以及紧张性NMDA电导的发生将在野生型小鼠和缺乏NMDAR亚基的小鼠的小脑片中进行研究。结合电生理学和电子显微镜，可以量化NMDAR亚型在产生突触和突触外反应中的相对作用。此外，培养的CGCs是一个同质神经元系统，在其中选择性地过度表达或删除蛋白质，并获得关于这些变化如何调节突触传递的数据。这些方法将使我们能够检验我们的领先假设，即兴奋性突触上NMDAR分子形式的异质性在决定兴奋性突触传递的有效性以及小脑可塑性方面具有生理作用。这些研究的结果将填补我们对这些生理作用是什么以及它们如何影响兴奋性突触传递的知识的空白。利用亚单位缺失小鼠的小脑突触，我们将有一个独特的机会来回答一个基本问题：为什么我们需要一种对中枢神经系统的可塑性至关重要的蛋白质的不同亚型？具有NMDAR亚单位表达变化的转基因小鼠正在成为从癫痫到精神分裂症等人类疾病的令人兴奋的模型。因此，我们将得到的结果，尽管显然与基础神经科学有关，但将在神经疾病和精神健康方面有显著的应用。

DESCRIPTION (provided by applicant): The sequential expression of the genes coding for NR2 subunits of N-methyI-D-aspartic acid receptors (NMDARs) during development produces an elegant concert of events that result in the expression of NMDA channels tailored in their kinetic properties to the physiologic roles they play. In this competitive renewal, we propose to continue the study of heterogeneity in excitatory synapses by electrophysiology, molecular biology and anatomic techniques. Our past studies demonstrate a selective regulation of NMDAR subtypes that control the functional properties of cerebellar synapses. Based on these results, we will investigate the consequences of the diversity of synaptic and extrasynaptic NMDARs in cerebellar granule cells (CGCs) for excitatory synaptic transmission and the control of information flow in the cerebellar cortex. CGCs offer the unique possibility to perform high-resolution patch clamp recordings of NMDAR-mediated synaptic currents with resolution of single-channel currents. Long-term potentiation (LTP) and long-term depression (LTD) and the occurrence of tonic NMDA conductances will be studied in cerebellar slices from wild-type mice and mice lacking NMDAR subunits. Combined electrophysiology and electron microscopy will allow quantitation of the relative role of NMDAR subtypes in producing synaptic and extrasynaptic responses. Furthermore, cultured CGCs are a system of homogenous neurons in which to selectively overexpress or delete proteins and obtain data on how these changes regulate synaptic transmission. These approaches will allow us to test our leading hypothesis that the heterogeneity of molecular forms of NMDARs at excitatory synapse has physiological roles in determining the efficacy of excitatory synaptic transmission and, in turn, cerebellar plasticity. The results of these studies will fill a gap in our knowledge of what these physiologic roles are and how they shape excitatory synaptic transmission. Using cerebellar synapses from subunit null mice we will have a unique opportunity to answer a fundamental question: Why do we need distinct subtypes of a protein key to the plasticity of the central nervous system? Transgenic mice with alteration of the expression of NMDAR subunits are becoming exciting models of human disorders ranging from epilepsy to schizophrenia. Thus, the results we will derive, although clearly related to basic neuroscience, will have notable applications to neurological disorders and to mental health