CRCNS US-German Research Proposal: Quantitative and Computational Dissection of Glutamatergic Crosstalk at Tripartite Synapses

CRCNS 美德研究提案：三方突触谷氨酸能串扰的定量和计算剖析

• 批准号: 10612169
• 负责人: Ghanim Ullah
• 金额: $ 12.58万
• 依托单位: UNIVERSITY OF SOUTH FLORIDA
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-15 至 2027-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10612169
• 关键词: Affect; Astrocytes; Bioenergetics; Brain; Brain region; Cell physiology; Cells; Cellular Morphology; Chemical Synapse; Communication; Computer Models; Data; Development; Disease; Dissection; Electrophysiology (science); Event; Excitatory Synapse; Extracellular Space; Feedback; Florida; Fluorescence Microscopy; Future; German population; Germany; Giant Cells; Glutamate Transporter; Glutamates; Heterogeneity; Hippocampus; Homeostasis; Impairment; Individual; Ion Transport; Ischemic Stroke; Link; Measures; Modeling; Molecular; Monitor; Morphology; Mus; N-Methyl-D-Aspartate Receptors; Neocortex; Neuronal Plasticity; Neurons; Pathway interactions; Pharmacology; Play; Preparation; Process; Production; Property; Protons; Research; Research Proposals; Role; Side; Signal Transduction; Site; Specificity; Structure; Synapses; Synaptic Cleft; Synaptic Transmission; Techniques; Testing; Time; Tissues; Universities; Viral; Work; density; design; driving force; excitotoxicity; experimental study; extracellular; fluorescence imaging; fluorescence lifetime imaging; image processing; insight; multi-scale modeling; multiphoton imaging; neocortical; nervous system disorder; neuronal cell body; neuronal excitability; neurotransmission; novel; novel strategies; pharmacologic; postsynaptic; predictive modeling; presynaptic; spatiotemporal; stoichiometry; synaptic function; tool; transmission process; uptake

CRCNS US-German Research Proposal: Quantitative and computational dissection of glutamatergic crosstalk at tripartite synapses (1) Christine R Rose, Heinrich Heine University, Düsseldorf, Germany (2) Christian Henneberger, University of Bonn, Germany (3) Ghanim Ullah, University of South Florida, Tampa, FL, USA Project Description 1 Introduction and Background Transmission at chemical synapses is the central mechanism by which information is transferred between neurons. Synaptic connections such as glutamatergic excitatory synapses are often perceived and modeled as point-to-point connections. However, there is substantial evidence that crosstalk between various glutamatergic synapses can occur when the presynaptically released glutamate is sensed not only by its direct postsynaptic partner but also by nearby synapses of the same and other neurons [4]. Notably, this phenomenon termed “glutamate spillover” not only defines the input-specificity of a given synaptic connection and its crosstalk to neighboring synapses, but is also involved in and controlled by activity-dependent plasticity [1, 7, 8]. How easily glutamate escapes from its release site and how far it spreads into the tissue depends on the morphological and molecular properties of the extracellular space (ECS) as well as on the efficacy of glutamate clearance, which primarily depends on astrocytic uptake [11, 12]. We and others have shown that the efficacy of perisynaptic glutamate uptake by astrocytes displays a remarkable heterogeneity between brain regions and, importantly, can vary drastically from one synapse to the next within a brain region [3, 7, 8]. This is in part because the morphological coverage of synapses by perisynaptic astrocyte processes (PAPs) can differ strongly between individual synapses [14]. Moreover, the Henneberger lab has recently shown that higher synaptic coverage by PAPs correlates with a higher local efficacy of glutamate uptake [3]. We have also demonstrated that in addition to being heterogeneous, astrocytic glutamate uptake and PAPs morphology both are controlled by neuronal plasticity [1]. Moreover, glutamate uptake is governed by the transporters’ stoichiometry, importing one glutamate molecule into the astrocyte by using the energy gained from co-transporting three Na+ and one proton down the electrochemical gradients, whilst also exporting one K+ [12]. While the inwardly-directed Na+ gradient is the main driving force for glutamate uptake, recent work by Rose lab and others have shown that glutamatergic activity causes local or global Na+ transients in astrocytes ([Na+]A) [15]. In the mouse hippocampus, astrocytic Na+ signals in fact arise predominately due to the activity of glutamate transporters themselves, degrading the Na+ gradient and thereby transiently weakening uptake capacity in a negative feedback-loop [15-17]. In the neocortex, glutamatergic synaptic activity in addition results in prominent Na+ influx through NMDA receptors, boosting astrocyte Na+ gradients [18]. Thus, it is increasingly appreciated that astrocytic glutamate uptake is neither static nor uniform. First, it is functionally dependent on the gradients of the transported ions which dynamically change with synaptic transmission [12]. Second, it is plastic because structural remodeling of PAPs on time scales of minutes profoundly alters perisynaptic glutamate spread [1]. Therefore, the emerging hypothesis is that the degree of glutamate spillover and, therefore, synaptic crosstalk in most brain regions are dynamically regulated and controlled at the level of the astrocytes. Furthermore, since a single astrocyte can contact thousands of synapses of various neurons, it has the potential to locally control the crosstalk of many synapses. In such a scenario, an astrocyte, or a subcellular domain of it, can coordinate crosstalk between many glutamatergic synapses on different neurons. Thereby, astrocytes and their PAPs set the spatial fidelity of glutamatergic synaptic transmission and as a consequence profoundly control neuronal signal exchange. So far, these important hypotheses remain largely untested. We will fill this gap by combining quantitative fluorescence imaging, astrocytic manipulations, and predictive computer modelling. This will be accomplished by investigating perisynaptic astrocytic Na+ gradients, the main driving force of glutamate uptake, and local mechanisms controlling them 1

CRCNS美国-德国研究提案：定量和计算解剖 三叉神经突触间的神经元串扰 (1)克莉丝汀R罗斯，海因里希海涅大学，杜塞尔多夫，德国 (2)Christian Henneberger，波恩大学，德国 (3)Ghanim Ullah，南佛罗里达大学，美国佛罗里达州坦帕 项目描述 1介绍和背景 化学突触的传递是信息被传递的中心机制。 在神经元之间传递。突触连接，如突触能兴奋性 突触通常被感知和建模为点对点连接。不过有 有大量证据表明，当 突触前释放的谷氨酸不仅被其直接的突触后伙伴感受到， 而且还受到同一神经元和其他神经元附近突触的影响[4]。值得注意的是，这种现象 被称为“谷氨酸溢出”不仅定义了给定突触的输入特异性， 连接及其与相邻突触的串扰，但也涉及并控制 活动依赖的可塑性[1，7，8]。 谷氨酸从其释放部位逃逸的难易程度以及它扩散到组织中的距离 取决于细胞外间隙（ECS）的形态和分子特性， 以及谷氨酸清除的功效，这主要取决于星形胶质细胞的摄取 [11，12]。我们和其他人已经表明，突触周围谷氨酸摄取的功效， 星形胶质细胞在大脑区域之间显示出显著的异质性，重要的是， 在大脑区域内，从一个突触到下一个突触变化很大[3，7，8]。这部分是 因为突触周围星形胶质细胞突起（PAP）对突触的形态覆盖 在不同的突触之间有很大的差异[14]。此外，Henneberger实验室 最近表明，PAP的较高突触覆盖率与较高的局部疗效相关， 谷氨酸摄取[3]。我们还证明了，除了是异质的， 星形胶质细胞谷氨酸摄取和PAP形态均受神经元可塑性控制 [1]的文件。此外，谷氨酸的摄取是由转运蛋白的化学计量决定的， 谷氨酸分子进入星形胶质细胞通过使用从共同运输三个 Na+和一个质子沿电化学梯度向下，同时也输出一个K+ [12]。 虽然内向Na+梯度是谷氨酸摄取的主要驱动力，但最近的研究表明， 罗斯实验室和其他人的工作表明，多巴胺能活动导致局部或全局Na+ 星形胶质细胞中的瞬变（[Na+]A）[15]。在小鼠海马体中，星形胶质细胞Na+信号实际上 主要是由于谷氨酸转运蛋白本身的活性， Na+梯度，从而在负反馈回路中暂时削弱吸收能力 [15-17]第二章。在新皮层，突触活动的结果，此外，突出的Na+ 通过NMDA受体流入，增加星形胶质细胞Na+梯度[18]。 因此，越来越多的人认识到星形胶质细胞的谷氨酸摄取既不是静态的， 制服首先，它在功能上依赖于所传输的离子的梯度， 随着突触传递的动态变化[12]。其次，它是塑料的，因为结构 以分钟为时间尺度的PAP重构深刻地改变了突触周谷氨酸扩散 [1]的文件。因此，新出现的假设是谷氨酸溢出的程度， 因此，大多数脑区的突触串扰是动态调节和控制的， 星形胶质细胞的水平。此外，由于单个星形胶质细胞可以接触数千个 突触的各种神经元，它有可能局部控制串扰的许多 突触在这种情况下，星形胶质细胞或其亚细胞区域可以协调 不同神经元上的许多突触之间的串扰。因此星形胶质细胞 和他们的PAP设置空间保真度的神经元突触传递，并作为一个 结果深刻地控制神经元信号交换。 到目前为止，这些重要的假设在很大程度上还没有得到验证。我们将填补这一空白， 结合定量荧光成像、星形细胞操作和预测 计算机模拟这将通过研究突触周星形胶质细胞Na+ 梯度，谷氨酸摄取的主要驱动力，以及控制它们的局部机制 1