The Roles of Huntingtin Associated Protein 40 in Huntingtin Functions and Huntington's Disease Pathogenesis

亨廷顿病（HD）是由亨廷顿蛋白中谷氨酰胺通道（polyQ）的异常扩张引起的 （HTT）。清楚地了解内源性HTT在体内是如何调节的，对于阐明HD 病因学和确定有效的药物靶点。HTT有许多报告的HTT相关合作伙伴（HAP） 并且在功能上涉及越来越多的细胞过程。然而，很少有人知道HTT本身是如何 以及房屋署有否更改有关规管。我们以前的特点HTT同系物（dHtt） 在模式生物果蝇中。鉴于HTT从果蝇到哺乳动物的重要功能保守性， 我们假设HTT的核心调节因子可能在众多已知的HAP中， 在果蝇中是保守的。在一项针对果蝇中HTT的保守中枢调节因子的蛋白质组学研究中， 我们分离了dHap 40，HAP 40的蝇同源物，作为最强的dHtt相互作用物。重要的是， 来自多个物种的研究的证据都支持体内HTT蛋白通常存在于一种复合物中， HAP 40，HAP 40结合稳定HTT的构象。此外，在来自HD患者的样品中，a~10- 与对照相比，观察到内源性HAP 40水平的成倍增加。但尽管 这些发现，到目前为止，还没有报道HAP 40在任何生理环境中的功能研究， 对HTT正常功能的影响和突变HTT毒性仍不清楚。我们的初步研究支持 HTT和HAP40之间的物理和功能相互作用显著保守，这意味着HTT和HAP40之间存在高度保守的相互作用。 重要的监管关系，限制他们的共同进化从苍蝇到人类。我们的发现不仅 建立果蝇作为相关的遗传模型，以研究HAP40的生理作用，但也导致我们的研究。 假设HAP 40是HTT保守的中枢调节因子， HTT毒性。使用已建立的果蝇和培养的哺乳动物细胞的测定和HD模型，我们将 系统地检验这个假设。在目标1中，我们将对dhap40进行全面的表型分析， 基因，并测试其与dhtt的遗传相互作用，从而获得HAP 40在一个 生理设置，并阐明其与HTT在整个动物水平的关系。在目标2中，我们将系统地 测试HAP40是否是HTT亚细胞动力学及其多种细胞功能的中心调节因子， 从分子和细胞水平阐明其与HTT的关系。目标3：利用好- 在果蝇和哺乳动物神经元中建立HD模型后，我们将严格询问HAP40的作用， 突变HTT毒性的研究从这些多学科研究中，我们将获得第一个全面的评价， HAP 40的生理功能、其对内源性HTT功能和HD发病机制的影响。的 这些结果可能为通过HAP 40治疗HD的新途径奠定基础。

Huntington's disease (HD) is caused by an abnormal expansion of the glutamine tract (polyQ) in Huntingtin (HTT). A clear understanding on how endogenous HTT is regulated in vivo is critical both for elucidating HD etiology and for identifying effective drug targets. HTT has numerous reported HTT associated partners (HAPs) and is functionally implicated in a growing list of cellular processes. However, little is known how HTT itself is regulated and whether such regulation is altered in HD. We previously characterized the HTT homolog (dHtt) in model organism Drosophila. Given the significant functional conservation of HTT from the fly to mammals, we hypothesized that the core regulators of HTT likely are among the numerous known HAPs and should also be conserved in Drosophila. In a proteomic study for such conserved central regulators of HTT in Drosophila, we isolated dHap40, the fly homolog of HAP40, as the strongest dHtt interactor. Importantly, converging evidence from studies in multiple species all support that in vivo HTT protein normally exists in a complex with HAP40, and HAP40 binding stabilizes the conformation of HTT. Further, in samples from HD patients, a ~10- fold increase of the levels of endogenous HAP40 were observed as compared to controls. However, despite these findings, by now there is no reported functional study of HAP40 in any physiological settings, and its effect on HTT's normal functions and mutant HTT toxicity remains unclear. Our preliminary studies support the significantly conserved physical and functional interactions between HTT and HAP40, implying a highly important regulatory relationship that constrains their co-evolution from flies to humans. Our findings not only establish Drosophila as a relevant genetic model to study the physiological roles of HAP40, but also lead to our hypothesis that HAP40 is a conserved central regulator of HTT and potentially a critical modulator of mutant HTT toxicity. Using established assays and HD models in Drosophila and cultured mammalian cells, we will systematically test this hypothesis. In Aim 1, we will carry out a comprehensive phenotypic analyses of dhap40 gene and test its genetic interactions with dhtt, so as to obtain a first systematic evaluation of HAP40 in a physiological setting and clarify its relationship with HTT at whole-animal level. In Aim 2, we will systematically test whether HAP40 is a central regulator of HTT's subcellular dynamics and its diverse cellular functions, so as to elucidate its relationship with HTT at molecular and cellular levels. In Aim 3, taking advantage of the well- established HD models in Drosophila and mammalian neurons, we will rigorously interrogate the role of HAP40 on mutant HTT toxicity. From these multidisciplinary studies, we will obtain a first comprehensive evaluation on the physiological functions of HAP40, its effect on endogenous HTT functions and on HD pathogenesis. The results potentially lay foundation on novel therapeutic avenues against HD via HAP40.