Molecular Mechanisms of Ataxin-1 Action

描述（由申请人提供）：共济失调蛋白-1（Atx 1）是一种神经退行性疾病蛋白，其扩展的谷氨酰胺重复形式在人类中引起脊髓小脑共济失调1型（SCA 1），并在小鼠和果蝇中发挥细胞毒性。虽然Atx 1和SCA 1之间的联系已经建立了十多年，但Atx 1的确切性质及其与SCA 1发病机制的联系仍不清楚。长期以来，人们一直认为Atx 1中扩展的谷氨酰胺重复序列是带来毒性作用的罪魁祸首，但越来越多的证据表明，该蛋白质的固有特性在SCA 1病理学中也起着重要作用。在我们的研究中，我们最近确定Atx 1在体外和体内直接结合一类保守的转录辅阻遏物，包括脊椎动物SMRT（类维生素A和甲状腺激素受体的沉默介体）及其果蝇同源物SMRTER。因此，我们假设AtxVs特性的一个关键方面涉及转录调控，并且保守的SMRT/SMRTER依赖性调控途径的扰动是其在脊椎动物和无脊椎动物中的细胞毒性的部分原因。由于SMRT和SMRTER都是核受体共阻遏物，因此该提议探讨Atx 1介导的细胞毒性是否涉及SMRT/SMRTER及其相关的核受体。在具体目标1，我们提出了各种分子生物学方法，包括染色质免疫沉淀法，调查是否Atx 1，通过其与SMRT的相互作用，参与在脊椎动物的甲状腺激素受体（TR）信号。在具体目标2中，我们将使用遗传方法来阐明果蝇中Atx 1，SMRTER和蜕皮激素受体（TR的功能等同物）之间的关系。最后，在特定目标3中，基于我们最近发现的Atx 1的两个功能结构域，SMRT/SMRTER相互作用AXH（Atx 1和HMG盒蛋白）结构域和自缔合NBA（N-末端区域的船和Atx 1）结构域，我们将研究这两个结构域可能对Atx 1的细胞毒性产生的特定后果。将Atx 1的功能与核激素受体信号传导联系起来将具有重大意义，因为它表明可以利用影响核激素受体运作的激素或化合物的干预来开发治疗SCA 1的治疗剂。

DESCRIPTION (provided by applicant): Ataxin-1 (Atx1) is a neurodegenerative disorder protein whose expanded glutamine-repeat form causes spinocerebellar ataxia type 1 (SCA1) in humans and which exerts cytotoxicity in mice and in Drosophila. Although the linkage between Atx1 and SCA1 has been established for more than a decade, the exact properties of Atx1 and their connection to the pathogenesis of SCA1 remain unclear. It was long thought that the expanded glutamine-repeat in Atx1 is the main culprit that brings about toxic effects, yet growing evidence indicates that the protein's inherent properties also play an important role in SCA1 pathology. In our research, we recently established that Atx1 binds directly to a class of conserved transcriptional co- repressors, including vertebrate SMRT (Silencing Mediator of Retinoid and Thyroid hormone receptors) and its Drosophila cognate SMRTER, both in vitro and in vivo. Consequently, we hypothesize that one key aspect of AtxVs properties involves transcriptional regulation, and that perturbation of conserved SMRT/SMRTER-dependent regulatory pathways is partly responsible for its cytotoxicity in both vertebrates and invertebrates. Because both SMRT and SMRTER are nuclear receptor co-repressors, this proposal probes whether Atx1-mediated cytotoxicity involves SMRT/SMRTER and their associating nuclear receptors. In Specific Aim 1, we propose various molecular biology approaches, including the chromatin immunoprecipitation method, to investigate whether Atx1, by means of its interaction with SMRT, is involved in thyroid hormone receptor (TR) signaling in vertebrates. In Specific Aim 2, we will use genetic approaches to elucidate the relationships among Atx1, SMRTER, and ecdysone receptor (the functional equivalent of TR) in Drosophila. Finally, in Specific Aim 3, building on our recent discovery of two functional domains of Atx1, the SMRT/SMRTER interacting AXH (Atx1 and HMG-box protein) domain and a self-association NBA (N-terminal region of Boat and Atx1) domain, we will investigate the specific consequences that these two domains may have for Atxl's cytotoxicity. Connecting the functions of Atx1 to nuclear hormone receptor signaling will have major implications, since it suggests that intervention with hormones or with chemical compounds that affect the operation of nuclear hormone receptors can be exploited to develop therapeutic agents for treating SCA1.