Ca Release Pathways as Integrators of Synaptic Signals

描述（由申请人提供）：第二信使信号的时空模式和通路之间的相互作用对于突触信息的整合和处理以及调节突触连接的强度是至关重要的。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。我们的重点是由肌醇1，4，5-三磷酸受体（IP 3Rs）和兰尼碱受体（RyRs）产生的Ca信号的性质和功能，它们介导细胞内储存的Ca释放。我们的假设是，钙释放途径的功能作为整合剂的突触活动，这一属性是细胞的基础上的关联性和突触特异性的诱导过程中的一种形式的突触可塑性被称为小脑长期抑郁症（LTD）。我以前的研究表明，通过IP 3敏感途径浦肯野神经元胞内钙释放主要参与LTD的诱导，IP 3受体的钙释放受IP 3和胞质钙的动态调节，表明该途径作为突触信号整合的巧合检测器。其他研究也暗示一氧化氮（NO）作为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时空动态是如何通过钙信号通路和其他参与LTD的第二信使级联之间的相互作用进行调节的。第二个目标是确定这些相互作用对LTD诱导的功能后果。对于这些实验，我们将使用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和急性小脑切片中信号传导途径的药理学操作。我们首先测试的想法，放大突触Ca信号的IP 3Rs和RyRs介导的突触输入之间的关联性，在诱导的LTD。然后，我们研究Ca释放和NO之间的关系，在诱导和空间传播的LTD，特别关注的模型中，NO调节LTD通过提高IP 3Rs和RyRs的敏感性。这些研究的结果应该澄清突触信号通路如何有助于LTD的诱导，并深入了解生化计算调节神经元之间的通信和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共济失调和其他运动问题的小脑功能障碍是很重要的。

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.