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

描述(申请人提供)：几个与神经系统疾病有关的基因被认为调节Rho GTP酶信号，但对这些信号蛋白的功能了解有限。WRP(Wave Association RAC Gap Protein，波形相关RAC间隙蛋白)就是这样一种蛋白，它被定位克隆为3P综合征精神发育迟滞(MR)的干扰基因。WRP通过与RAC效应器WAVE-1结合和刺激RAC GTP水解来调节肌动蛋白重塑。波1缺失的小鼠在学习和记忆测试中表现出戏剧性的行为障碍。重要的是，波-1缺失小鼠的表型与3p综合征发育迟缓小鼠的表型很好地重叠，支持WRP调节信号与MR之间的联系。这项应用的目的是研究WRP调节的分子机制，以及WRP的丢失是否影响导致行为损害的特定神经功能。我们的中心假设是，WRP的一个细胞功能是调节脊椎中的肌动蛋白信号。因此，WRP的丢失会导致脊柱异常和认知障碍。这一假说是由强大的初步数据指导的，这些数据基于1)结构/功能和定义WRP靶向结构域的成像数据，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。这笔赠款的具体目标是：1)确定在空间上针对和调节WRP的机制。我们将使用生化和成像方法的组合，旨在解决WRP是如何被调控的，并可能被定位于亚细胞隔室。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的靶向是这一信号通路在脊椎中的一个显著特征。我们将使用成像和细胞分析来量化WRP靶向在突触功能中的作用。3)检测WRP对大鼠认知行为和突触功能的体内调节作用。使用条件性WRP缺失小鼠模型，我们将分析体内和体外突触功能的各个方面。我们还将检查这些小鼠与3P综合征发育迟缓相关的一系列行为的异常。由于这一建议利用多学科方法来分析WRP信号，可以预期在理解肌动蛋白信号与神经元功能障碍之间的机制方面取得根本性进展。公共卫生相关性：这项研究与美国国立卫生研究院的任务相关，因为它在分子、细胞和组织水平上检查了与智力低下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方面取得重要进展。预计这些研究中获得的知识将有助于揭示其他形式的神经病理，涉及异常的Rho-GTPase信号和正常调节神经元连接的机制。

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.