Functional Effects of PDE11A Alzheimer's-Associated Variants

项目摘要：PDE11A阿尔茨海默病(AD)相关变异的功能效应 这项父母资助研究了与年龄相关的酶的表达和异位定位的增加。 磷酸二酯酶11A(PDE11A)可导致年龄相关性认知功能下降(ARCD)。PDE11A特别值得关注 在衰老和阿尔茨海默病的背景下，因为它在大脑中的表达在海马结构中丰富-a 对情节记忆至关重要的区域，在AD中严重受损。我们发现PDE11A表达 啮齿动物和人类海马区随年龄增长而增加，在痴呆患者海马区进一步升高 与有脑外伤病史的非痴呆老年人进行比较。我们已经确定，这些与年龄相关的增长在 PDE11A异位富含在海马区的“鬼轴突”，即密集的轴突终末。 被PDE11A蛋白包裹，其他轴突蛋白被闭塞。通过突变分析，我们有 已确定的分子内信号负责这些与年龄相关的PDE11A表达增加及其 异位定位，并表明Pde11a基因敲除小鼠对ARCD具有保护作用。考虑到 高龄是患痴呆症的最大风险因素，再加上这些PDE11A“幽灵轴突” 尤其令人联想到与ADRDS相关的tau蛋白病变，非常有趣的是 罕见的PDE11A变异(即R202H和L756Q)最近被认为与早发性AD有关。其影响 这些突变中的PDE11A功能没有被直接测量；然而，突变体的表达 体外实验中增加重组tau蛋白的磷酸化。这种PDE11A突变导致的 P-tau与在ADRD脑中观察到的病理生理学一致；然而，它提示PDE11A丢失- 这一功能与我们在正常老化时观察到的PDE11A的功能增益形成了直接对比。AS 因此，我们测试了与AD相关的PDE11A突变会改变催化活性和/或 以与老化本身根本不同的方式对PDE11A进行亚细胞区隔， 从而产生比正常衰老更严重的生化和行为缺陷。 跨越这两个目标，我们采取了一种综合的方法，将体内和体外的遗传操作与 行为、生理和生化终点。在具体目标1中，我们确定与AD相关的 PDE11A变异体改变蛋白质表达、催化活性、亚细胞区隔、磷酸化、 以及PDE11A在内源性表达tau和tau的海马细胞系中的下游信号转导 概述了PDE11A年龄相关的蛋白病变。在特定的目标2中，我们确定是否上调了 小鼠海马区的这些与PDE11A AD相关的变异体可导致更广泛的认知功能衰退 野生型PDE11A的高表达。这些创新研究将为我们提供亟需的洞察 这些AD相关突变的功能后果与 神经科学的目标是了解ARCD的过程如何与AD的发展相交。

PROJECT SUMMARY: Functional Effects of PDE11A Alzheimer’s Disease (AD)-Associated Variants This parent grant explores how age-related increases in expression and ectopic localization of the enzyme Phosphodiesterase 11A (PDE11A) drive age-related cognitive decline (ARCD). PDE11A is of particular interest in the context of aging and AD because its expression in brain is enriched in the hippocampal formation—a region that is critical for episodic memory and is severely impaired in AD. We find PDE11A expression increases with age in the rodent and human hippocampus and is further elevated in hippocampus of demented vs. non-demented aged humans with a history of TBI. We have established that these age-related increases in PDE11A are ectopically enriched in hippocampal “ghost axons”—that is, axonal terminals that are so densely packed with PDE11A protein that other axonal proteins are occluded. Through mutational analyses, we have identified intramolecular signals responsible for these age-related increases in PDE11A expression and its ectopic localization and have shown that Pde11a knockout mice are protected against ARCD. Given that advanced age is the strongest risk factor for dementia, coupled with the fact that these PDE11A “ghost axons” are particularly reminiscent of tau proteinopathies that are associated with ADRDs, it is highly interesting that 2 rare PDE11A variants (i.e., R202H and L756Q) have recently been associated with early-onset AD. The impact of these mutations on PDE11A function were not measured directly; however, expression of the mutants increased phosphorylation of recombinant tau in an in vitro assay. This PDE11A mutation-induced increase in p-tau is consistent with the pathophysiology observed in ADRD brains; however, it suggests a PDE11A loss-of- function that stands in direct contrast to the PDE11A gain-of-function that we observe with normal aging. As such, we test the overarching hypothesis that AD-related PDE11A mutations alter catalytic activity and/or subcellular compartmentalization of PDE11A in a manner that fundamentally differs from aging itself, thereby producing biochemical and behavioral deficits worse than those seen with normal aging. Across the 2 aims, we take an integrative approach by coupling in vivo and in vitro genetic manipulations with behavioral, physiological, and biochemical endpoints. In Specific Aim 1, we determine how the AD-related PDE11A variants alter protein expression, catalytic activity, subcellular compartmentalization, phosphorylation, and downstream signaling of PDE11A in a hippocampal cell line that endogenously expresses tau and recapitulates PDE11A age-related proteinopathies. In Specific Aim 2, we determine if elevated expression of these PDE11A AD-associated variants in mouse hippocampus produces more widespread cognitive decline than elevated expression of wild-type PDE11A.These innovative studies will provide much needed insight into the functional consequences of these AD-related mutations and are consistent with the Division of Neuroscience’s goal to understand how the processes of ARCD intersect with the development of AD.