GAPs in Signaling to the Spine and Retardation: Mechanisms and the Role of WRP

描述（由申请人提供）：与神经系统疾病有关的几种基因被认为调节Rho GT3信号传导，但对这些信号传导蛋白如何发挥作用的理解有限。WRP（WAVE相关的Rac GAP蛋白）是这样一种蛋白，其通过定位克隆被鉴定为在3 p综合征精神发育迟滞（MR）中被破坏的基因。WRP通过与Rac效应物WAVE-1结合并通过刺激Rac GTP水解来调节肌动蛋白重塑。WAVE-1基因敲除小鼠在学习和记忆测试中表现出显著的行为障碍。重要的是，WAVE-1无效小鼠的表型与3 p综合征迟缓的表型重叠，支持WRP调节的信号传导和MR之间的联系。本申请的目的是研究调节WRP的分子机制以及WRP的丧失是否影响导致行为障碍的特定神经元功能。我们的中心假设是，WRP的细胞功能之一是调节肌动蛋白信号在棘。因此，WRP的丢失将导致脊柱异常和认知障碍。该假设由基于以下的强有力的初步数据指导：1）定义WRP靶向结构域的结构/功能和成像数据，以及2）将WRP和WAVE-1与脊髓发生、突触可塑性和认知行为联系起来的数据。该基金的具体目标是：1）确定空间靶向和调节WRP的机制。我们将使用生物化学和成像方法的组合，旨在解决WRP是如何调节，并可能针对亚细胞区室。2)描述锚定WRP的细胞作用。由于WRP调节Rac和WAVE-1，我们假设WRP的靶向是棘中该信号通路的显著特征。我们将使用成像和细胞测定来量化WRP靶向在突触功能中的作用。3)测试WRP在调节认知行为和突触功能方面的体内功能。使用条件性WRP无效小鼠模型，我们将在体内和体外分析突触功能的各个方面。我们还将检查这些小鼠与3 p综合征迟缓相关的一系列行为异常。由于这一建议利用多学科的方法来分析WRP信号，在理解肌动蛋白信号转导与神经元功能障碍的机制方面取得了根本性的进展。公共卫生相关性：这项研究与NIH的使命有关，因为它在分子、细胞和生物体水平上研究了与智力迟钝有关的基因的功能作用。因此，可以预期在理解精神发育迟滞的病因学方面会取得重要进展。还预计，在这些研究中获得的知识将揭示其他形式的神经病理学，涉及异常Rho-GTdR信号传导和机制，通常调节神经元连接。

DESCRIPTION (provided by applicant): Several genes implicated in neurological disease are thought to regulate Rho GTPase signaling, yet there is a limited understanding of how these signaling proteins function. WRP (WAVE associated Rac GAP protein), which was identified by positional cloning as a gene disrupted in 3p-syndrome mental retardation (MR), is one such protein. WRP regulates actin remodeling by binding to the Rac effector WAVE-1 and by stimulating Rac GTP hydrolysis. WAVE-1 null mice exhibit dramatic behavioral impairments in learning and memory tests. Importantly, the phenotype of WAVE-1 null mice overlaps well with those of 3p-syndrome retardation, supporting a link between WRP regulated signaling and MR. The objective of this application is to examine the molecular mechanisms regulating WRP and whether loss of WRP affects specific neuronal functions that contribute to behavioral impairments. Our central hypothesis is that one cellular function of WRP is to regulate actin signaling in spines. Thus loss of WRP would lead to spine abnormalities and cognitive impairments. This hypothesis is guided by strong preliminary data based on 1) structure/function and imaging data defining a WRP targeting domain and 2) data linking WRP and WAVE-1 to spinogenesis, synaptic plasticity and cognitive behavior. The specific aims of this grant are: 1) Identify the mechanisms that spatially target and regulate WRP. We will use a combination of biochemical and imaging approaches designed to address how WRP is regulated and may be targeted to subcellular compartments. 2) Delineate the cellular role of anchored WRP. Because WRP regulates Rac and WAVE-1, we hypothesize targeting of WRP is a salient feature of this signaling pathway in spines. We will use imaging and cellular assays to quantify the role of WRP targeting in synapse function. 3) Test the in vivo function of WRP in regulating cognitive behavior and synapse function. Using a conditional WRP null mouse model we will analyze aspects of synapse function in vivo and in vitro. We will also examine these mice for abnormalities in a range of behaviors related to 3p-syndrome retardation. Because this proposal utilizes a multidisciplinary approach to analyze WRP signaling, a fundamental advance in understanding the mechanisms linking actin signaling to neuronal dysfunction can be anticipated. PUBLIC HEALTH RELEVANCE: This research is relevant to the mission of NIH because it examines the functional role of a gene implicated in mental retardation at the molecular, cellular and organismal level. Thus, important advances in understanding the etiology of mental retardation could be anticipated. It is also expected that knowledge gained in these studies will shed light on other forms of neuropathologies that involve abnormal Rho-GTPase signaling and mechanisms that normally regulate neuronal connectivity.