Ca Release Pathways as Integrators of Synaptic Signals

描述(申请人提供)：第二信使信号的时空模式和通路之间的相互作用是突触信息整合和处理以及调节突触连接强度的中心。本研究的主要目的是了解钙信号在小脑浦肯野神经元突触功能中的作用。我们的重点是1，4，5-三磷酸肌醇受体(IP3Rs)和兰尼定受体(RyRs)产生的钙信号的性质和功能，它们介导细胞内钙释放。我们的假设是，钙释放途径作为突触活动的整合因子发挥作用，这一特性是在小脑长期抑制(LTD)的一种突触可塑性诱导过程中关联性和突触特异性的细胞基础。我以前的研究证实，浦肯野神经元通过IP3敏感的通路从细胞内库释放钙主要参与LTD的诱导，IP3受体的钙释放受到IP3和细胞内钙的动态调节，这表明这一途径是突触信号整合的符合检测器。其他研究也表明一氧化氮(NO)是LTD的另一个关键决定因素。这里提出的研究有两个主要目标。第一个目标是了解浦肯野细胞树突中钙释放的空间和时间动态如何受到钙信号通路和其他第二信使级联信号通路之间相互作用的调节。第二个目标是确定这些相互作用对LTD的诱导的功能后果。对于这些实验，我们将结合高速共聚焦显微镜钙测量、电生理学、笼状化合物的局部光解以及急性小脑切片中信号通路的药物操作。我们首先验证了在LTD的诱导过程中，IP3Rs和RyRs对突触钙信号的放大介导了突触输入之间的联系。然后，我们研究了钙释放和NO在LTD的诱导和空间扩散中的关系，特别是NO通过增强IP3Rs和RyRs的敏感性来调节LTD的模型。这些研究的结果将阐明突触信号通路如何在LTD的诱导中起作用，并使我们深入了解生化计算调节神经元之间的通信并塑造单个神经元的信号处理能力的基本机制。这些信息对于理解小脑对运动功能的控制以及导致共济失调和其他运动问题的小脑功能障碍很重要。

DESCRIPTION (provided by applicant): The spatiotemporal patterns of second messenger signals and interactions among pathways are central to the integration and processing of synaptic information and to regulating the strength of synaptic connections. The general goal of this proposal is to understand the role of calcium (Ca) signaling in the synaptic function of cerebellar Purkinje neurons. Our focus is on the properties and function of Ca signals produced by inositol 1,4,5-trisphosphate receptors (IP3Rs) and ryanodine receptors (RyRs), which mediate Ca release from intracellular stores. Our hypothesis is that the Ca release pathways function as integrators of synaptic activity, and that this property is the cellular basis for associativity and synapse specificity during the induction of a form of synaptic plasticity known as cerebellar long-term depression (LTD). My previous studies established that Ca release from intracellular stores via the IP3-sensitive pathway in Purkinje neurons is centrally involved in the induction of LTD and that Ca release by IP3 receptors is dynamically regulated by both IP3 and cytosolic Ca in a way that suggests this pathway acts as a coincidence detector for the integration of synaptic signals. Other studies have also implicated nitric oxide (NO) as another key determinant of LTD. The studies proposed here have two primary objectives. The first goal is to understand how the spatial and temporal dynamics of Ca release in Purkinje cell dendrites are regulated by the interplay between Ca signaling pathways and other second messenger cascades involved in LTD. The second goal is to determine the functional consequences of these interactions for the induction of LTD. For these experiments, we will use a combination of high-speed confocal microscopic Ca measurements, electrophysiology, localized photolysis of caged compounds, and pharmacological manipulations of signaling pathways in acute cerebellar slices. We first test the idea that amplification of synaptic Ca signals by IP3Rs and RyRs mediates associativity between synaptic inputs during the induction of LTD. We then examine the relationship between Ca release and NO in the induction and spatial spread of LTD, with particular focus on a model in which NO regulates LTD by enhancing the sensitivity of IP3Rs and RyRs. The results of these studies should clarify how synaptic signaling pathways contribute to the induction of LTD, and give insight into fundamental mechanisms by which biochemical computation regulates communication between neurons and shapes the signal processing capabilities of individual neurons. This information is important for understanding the control of motor function by the cerebellum and the cerebellar dysfunction that underlies ataxia and other motor problems.