Deranged calcium signaling and polyglutamine expansion disorders

描述（由申请人提供）：该项目的长期目标是了解聚谷氨酰胺（polyQ）扩张障碍中神经变性的分子基础。多q扩增疾病属于常染色体显性致死性神经退行性疾病家族，具有共同的分子触发（CAG重复扩增）。许多毒性功能已被分配到polyq扩增蛋白，但到目前为止，对这些疾病的致病机制还缺乏明确的认识。没有一种多q扩张障碍是可以治愈的。亨廷顿氏病（HD）是研究最广泛的多q扩张疾病。纹状体中棘神经元（MSN）在HD中受到选择性影响。亨廷顿蛋白（Httexp）的polyq扩增是HD的分子原因。我的实验室最近发现，Httexp直接结合并激活1型肌醇1,4,5-三磷酸受体（InsP3R1），这是细胞内Ca2+释放通道。此外，我们在体外实验中证明了异常神经元Ca2+信号传导与HD MSN细胞凋亡之间的直接联系。现在我建议进一步验证“HD的Ca2+假说”。我也建议应用类似的想法来理解脊髓小脑性共济失调3型（SCA3）的发病机制，SCA3是多q扩张障碍家族的另一成员。具体而言，我建议：

DESCRIPTION (provided by applicant): The broad, long-term objective of the project is to understand the molecular basis for neurodegeneration in polyglutamine (polyQ) expansion disorders. The polyQ-expansion disorders belong to the family of autosomal-dominant and lethal neurodegenerative diseases that share a common molecular trigger (CAG repeat expansion). A number of toxic functions have been assigned to the polyQ-expanded proteins, but so far clear understanding of pathogenic mechanisms involved in these disorders is lacking. None of the polyQ- expansion disorders have a cure. Huntington's disease (HD) is the most extensively studied among polyQ- expansion disorders. Striatal medium spiny neurons (MSN) are selectively affected in HD. PolyQ-expansion in Huntingtin protein (Httexp) is a molecular cause of HD. My laboratory recently discovered that Httexp directly binds to and activates the type 1 inositol 1,4,5-trisphosphate receptor (InsP3R1), an intracellular Ca2+ release channel. Furthermore, we demonstrated a direct connection between abnormal neuronal Ca2+ signaling and apoptosis of HD MSN in in vitro experiments. Now I propose to further test "Ca2+ hypothesis of HD". I also propose to apply similar ideas to understanding the mechanisms of pathogenesis in spinocerebellar ataxia type 3 (SCA3), another member of polyQ-expansion disorders family. Specifically, I propose: 1. To analyze biochemical and functional interactions between InsP3R1 and polyQ-expanded Huntingtin protein. To test "Ca2+ hypothesis of HD" in experiments with HD-YAC128 mouse model of HD. 2. To analyze biochemical and functional interactions between InsP3R1 and polyQ-expanded ataxin-3 protein. To test "Ca2+ hypothesis of SCA3" in experiments with SCA3-YAC84Q mouse model of SCA3. 3. To validate our results in Ca2+ imaging and biochemical experiments with primary fibroblasts from human HD and SCA3 patients Our experiments will provide a critical test for a role of deranged Ca2+ signaling in pathogenesis of HD and SCA3 and may have implications for understanding and treatment of other polyQ-expansion disorders. The proposed project will have direct and immediate relevance for public health. Huntington's disease (HD) and Spinocerebellar Ataxia type 3 (SCA3) are incurable genetic disorders that cause enormous suffering. The experiments described in the grant are aimed at testing specific hypothesis regarding pathogenesis of these diseases and will provide information critical for development of the cure.