Molecular mechanisms of excitatory postsynaptic diversity

神经元之间突触连接的独特模式，以及这些突触的不同强度，是 对大脑的信息处理能力至关重要。突触的强度由数量决定， 突触后AMPA受体(AMPAR)的组成和翻译后修饰。这些功能 受一系列第二信使通路、支架蛋白和运输蛋白的调节 以突触后密度(PSD)表示。对于主要显示突触后可塑性的突触，蛋白质 负责调节AMPAR表面表达的基因被认为在谷氨酸能PSD中是共享的。 因此，尚不清楚突触之间的突触强度是否存在根本差异，这是由于 单个PSD的独特蛋白质签名。神经元特异性基因(NSG1-3)编码单一跨膜 参与多种支架和信号蛋白分泌运输的蛋白质，包括突触后 AMPAR。对培养细胞和急性海马片制备的研究已经证实 单独干扰NSG1-3的功能会导致基础突触活性和可塑性的严重变化。 有趣的是，我们公布的和初步的证据表明，NSG1和NSG2长期驻留在 兴奋性海马神经元中的突触亚群。此外，我们数据显示，这些基因的敲除(KO) 蛋白质不同地影响网络功能并导致行为缺陷。这项研究将具有重要意义 因为它将确定NSG家族的多个成员是否被限制在唯一的 兴奋性突触，并通过促进AMPAR表面表达来赋予独特的功能特性。 我们将使用经过验证的和新颖的技术相结合的方式，分三个阶段来解决这些重要问题 具体目标： 具体目的1.确定神经生长因子蛋白是否定义了兴奋性突触的独特群体(S)。 我们将使用体外时间推移和体外成像来确定NSG1和NSG2是否特异性 定位于海马区突触的一个子集，或在它们之间进行交易。 特定目的2.确定单个NSG蛋白是否对突触功能有不同影响。 利用生理记录和谷氨酸去除，我们将确定NSG1/2是否存在差异 参与在基础或活性依赖条件下促进表面AMPAR的表达。 具体目标3：确定NSG蛋白的KO是否导致特定的、可分离的行为缺陷。 在单KO和双KO小鼠中使用已建立的和新的行为测试，我们将确定NSG1/2 蛋白质在塑造活体动物的运动、情感和认知功能方面发挥着独特或重叠的作用。

Unique patterns of synaptic connectivity between neurons, and the differential strength of those synapses, are fundamental to the information processing capability of the brain. Synaptic strength is determine by the number, composition, and post-translational modifications of post-synaptic AMPA receptors (AMPARs). These features of AMPARs are regulated by a host of second messenger pathways, scaffolding proteins, and trafficking proteins in post-synaptic densities (PSDs). For synapses that display primarily postsynaptic plasticity, the proteins responsible for regulating AMPAR surface expression are thought to be shared across glutamatergic PSDs. Thus, it remains unknown whether fundamental differences in synaptic strength between synapses exist due to unique protein signatures of individual PSDs. Neuron-specific genes (NSG1-3) encode single transmembrane proteins involved in the secretory trafficking of multiple scaffold and signaling proteins, including postsynaptic AMPARs. Studies in cultured cells as well as acute hippocampal slice preparations have established that disrupting NSG1-3 function independently causes severe alterations in basal synaptic activity and plasticity. Interestingly, our published and preliminary evidence show that NSG1 and NSG2 chronically reside within a subset of synapses in excitatory hippocampal neurons. In addition, our data show that knockout (KO) of these proteins differentially affects network function and induces behavioral deficits. This study will be significant because it will identify whether multiple members of the NSG family are restricted to a unique subpopulation of excitatory synapses, and confer unique functional properties via the promotion of AMPAR surface expression. We will use a combination of validated and novel techniques to address these important questions in three specific aims: Specific Aim 1. Determine whether NSG proteins define unique population(s) of excitatory synapses. We will use in vitro time lapse, and ex vivo imaging to determine whether NSG1 and NSG2 are specifically targeted to a subset of hippocampal synapses or trafficked between them. Specific Aim 2. Determine whether individual NSG proteins differentially affect synaptic function. Using physiological recordings and glutamate uncaging we will determine whether NSG1/2 are differentially involved in promoting surface AMPAR expression during basal or activity-dependent conditions. Specific Aim 3: Determine whether KO of NSG proteins leads to specific, dissociable behavioral deficits. Using established and novel behavioral tests in single and double KO mice we will determine whether NSG1/2 proteins play unique or overlapping roles in shaping motor, affective, and cognitive function in live animals.