Dual CHIP Functions Control Tau Triage In Alzheimer's Disease

项目摘要/摘要 在大脑中聚集的tau蛋白是阿尔茨海默病(AD)的一个重要特征， 合理的治疗目标，以防止AD的进展。老鼠身上的遗传证据有力地支持了这一观点 Tau促进AD患者的认知缺陷。虽然反聚集和免疫治疗方法已经出现 作为减少tau在大脑中聚集的潜在策略，这些药物针对的是晚期tau中间体。大有可为 对于在其他健康神经元中产生tau聚集体的早期事件，人们知之甚少。 依赖伴侣的折叠以补偿方式恢复tau功能的时间段 一种关键的微管(MT)稳定因子。我们试图定义这些早期的tau分类决定，因为 在这个较早的窗口中临床靶向tau是非常可取的，以防止tau积累，特别是在 无症状的人从疾病开始几年到几十年。热休克70的C末端--相互作用 蛋白质(或芯片)在协调蛋白质质量控制方面发挥着核心作用。虽然大多数先前的研究都有 指出CHIP的E3连接酶活性是包括tau在内的客户底物降解的主要中介， 现在的研究表明，芯片包含一种鲜为人知的内在伴侣功能，这种功能 完全不依赖于其E3连接酶的活性。脊髓小脑性共济失调16(SCAR 16)的遗传学研究 患者，一种罕见的神经退行性疾病，表明仅丧失芯片辅伴活性就足够了。 导致神经退化和认知功能障碍。这些先前的研究，再加上我们引人注目的新发现 初步数据显示，CHIP直接结合和伴侣tau以促进其去磷酸化， 为芯片介导的tau分流新模式提供有力支持。我们假设芯片可以防止 异常的tau修饰和聚集，恢复正常的tau功能和MT稳定，以及 改善AD相关的认知功能衰退。在AIM-1中，我们将剖析芯片作为调节器的双重功能 用体外生化和生物物理方法测定tau的功能和磷酸化。这些研究将提供 对芯片如何瞄准和修复异常tau物种的新机械见解。在AIM-2中，我们将探索 CHIP通过稳定MTS在介导神经保护中的新作用。我们将测试以下要求 ChIP辅助伴侣活性在维持MT完整性从而促进神经元存活方面的作用 否则就会退化。最后，在AIM-3中，我们将测试芯片辅助伴侣的临床意义 在阿尔茨海默病动物模型中恢复认知功能。总体而言，我们的建议意义重大，因为它将 说明决定tau最初如何处理和分类的早期事件。它也是创新的 因为它第一次强调了芯片的双重分子功能，这些功能与tau的发病机制和 这种毁灭性疾病的发展。

PROJECT SUMMARY/ABSTRACT The accumulation of aggregated tau protein in the brain is a defining feature of Alzheimer’s disease (AD) and a logical therapeutic target to prevent AD progression. Genetic evidence in mice strongly supports the notion that tau promotes cognitive deficits in AD. While anti-aggregation and immunotherapy approaches have emerged as potential strategies to reduce tau aggregation in the brain, these target late-stage tau intermediates. Much less is known about the early-stage events that give rise to tau aggregates in otherwise healthy neurons, a time period in which chaperone-dependent refolding acts in a compensatory manner to restore tau function as a critical microtubule (MT) stabilizing factor. We seek to define these early-stage tau triage decisions since clinically targeting tau in this earlier window is highly desirable to prevent tau accumulation, particularly in asymptomatic individuals years to decades from disease onset. The C-terminus of heat shock 70-interacting protein (or CHIP) plays a central role in orchestrating protein quality control. While most prior studies have pointed to CHIP’s E3 ligase activity as a principal mediator of client substrate degradation including tau, studies now indicate that CHIP contains a poorly understood intrinsic chaperone function that operates completely independent of its E3 ligase activity. Genetic studies of spinocerebellar ataxia 16 (SCAR 16) patients, a rare neurodegenerative disorder, showed that loss of CHIP co-chaperone activity alone is sufficient to cause neurodegeneration and cognitive dysfunction. These prior studies, combined with our compelling new preliminary data showing that CHIP directly binds and chaperones tau to facilitate its dephosphorylation, provide strong support for a new model of CHIP-mediated tau triage. We hypothesize that CHIP prevents aberrant tau modifications and aggregation, restores normal tau function and MT stabilization, and ameliorates AD-related cognitive decline. In Aim-1, we will dissect CHIP’s dual functions as a regulator of tau function and phosphorylation using biochemical and biophysical assays in vitro. These studies will provide new mechanistic insights into how CHIP targets and repairs abnormal tau species. In Aim-2, we will explore a novel role for CHIP in mediating neuroprotection via the stabilization of MTs. We will test the requirements for CHIP co-chaperone activity in maintaining MT integrity and hence promoting survival in neurons that would otherwise undergo degeneration. Finally, in Aim-3, we will test the clinical implications of CHIP co-chaperone function in restoring cognition in an animal model of AD. Overall, our proposal is significant because it will illuminate the early-stage events that determine how tau is initially processed and triaged. It is also innovative because it is the first to highlight dual molecular functions of CHIP that are relevant to tau pathogenesis and the progression of this devastating disease.