Interplay between tau and PKA condensates in ADRD

项目总结/摘要 cAMP依赖性蛋白激酶（PKA）信号传导对学习记忆和cAMP升高至关重要 磷酸二酯酶（PDE）抑制剂正处于阿尔茨海默病（AD）和AD相关疾病的临床开发中。 痴呆症（ADRD）。RIβ是PKA的脑特异性调节亚基，其中有几种RIβ突变。 R335 W和L50 R最近被证明会导致神经系统症状，包括智力残疾 在儿童和成人痴呆症。我们最近发现，RIα，PKA的另一个RI调节亚基， 经历作为cAMP信号传导的函数的液-液相分离（LLPS）以动态缓冲cAMP， 这对信号传导途径的特异性至关重要。在我们的初步研究中，我们发现cAMP- 结合的RIβ也经历LLPS，并且L50 R和R335 W突变显著改变RIβ的性质 冷凝物重要的是，PKA还参与调节tau蛋白缩合物，如tau蛋白被一种蛋白激酶磷酸化。 包括PKA在内一系列蛋白激酶已经显示出触发tau LLPS。此外，特异性PKA信号传导 对于CREB介导的转录和蛋白质降解至关重要，其失调有助于 AD/ADRD。然而，RIβ缩合物在AD/ADRD中的功能性影响以及tau蛋白和 RIβ缩合物尚未被探索。 我们组建了一个多PI团队，来自两个机构的互补专业知识来研究分子 以及PKA/RIβ相分离的细胞机制和对tau蛋白病和认知障碍的保护作用 在衰老和疾病中衰退。为此，我们产生了携带表位标记的野生型小鼠， RIβ基因Prkar 1b的致病性R335 W和L50 R等位基因。我们假设RIβ缺陷 LLPS和RIβ与tau缩合物之间的失调相互作用与AD/ADRD密切相关。在aim中 1，我们将使用多种细胞类型，包括来自Prkar 1b突变小鼠的皮质培养物来研究它们之间的相互作用。 tau和RIβ凝聚物之间的关系。目标2旨在回答 这两个相分离蛋白如何在体内功能性地相互作用以影响tau蛋白的互补问题 在额颞叶痴呆（hTau P301 L）小鼠模型中的病理学和记忆丧失。我们提出的研究 不仅将开发新的工具和小鼠模型来研究RIβ LLPS缺陷的影响， 同时也为进一步的机理研究建立了合作框架 AD/ADRD中失调的生物分子缩合物。更好地理解潜在机制是 最重要的是确定新的治疗靶点和改善治疗剂的功效， 开发，如PDE抑制剂。

Project Summary / Abstract Signaling by cAMP-dependent protein kinase (PKA) is essential for learning and memory and cAMP-elevating phosphodiesterase (PDE) inhibitors are in clinical development for Alzheimer’s disease (AD) and AD-related dementias (ADRD). RIβ is a brain-specific regulatory subunit of PKA and several RIβ mutations, among them. R335W and L50R, have recently been shown to cause neurological symptoms, including intellectual disability in children and dementia in adults. We recently discovered that RIα, the other RI regulatory subunit of PKA, undergoes liquid-liquid phase separation (LLPS) as a function of cAMP signaling to dynamically buffer cAMP, which is critical for the specificity of the signaling pathway. In our preliminary studies, we showed that cAMP- bound RIβ also undergoes LLPS and the L50R and R335W mutations significantly alter the properties of RIβ condensates. Importantly, PKA is also involved in regulating tau condensates, as phosphorylation of tau by a suite of protein kinases including PKA has been shown to trigger tau LLPS. In addition, specific PKA signaling is critical for CREB mediated transcription and protein degradation, dysregulation of which contribute to AD/ADRD. However, the functional impact of RIβ condensates in AD/ADRD and the interplay between tau and RIβ condensates have not been explored. We assembled a multi-PI team with complementary expertise from two institutions to investigate the molecular and cellular mechanisms governing PKA/RIβ phase-separation and protection from tauopathy and cognitive decline during aging and in disease. To this end, we generated mice carrying epitope-tagged wild-type and pathogenic R335W and L50R alleles of Prkar1b, the gene encoding RIβ. We hypothesize that defective RIβ LLPS and dysregulated interplays between RIβ and tau condensates are critically linked to AD/ADRD. In aim 1, we will use multiple cell types, including cortical cultures from Prkar1b-mutant mice to study the interplay between tau and RIβ condensates using biophysical and imaging approaches. Aim 2 seeks to answer the complementary question how the two phase-separating proteins interact functionally in vivo to influence tau pathology and memory loss in a mouse model of frontotemporal dementia (hTau P301L). Our proposed study will not only develop novel tools and mouse models to study the impact of defective RIβ LLPS and interplays between RIβ and tau condensates, but also establish a collaboration framework for further mechanistic studies of dysregulated biomolecular condensates in AD/ADRD. A better understanding of underlying mechanisms is paramount to identify new therapeutic targets and to improve upon the efficacy of therapeutics under development, such as PDE inhibitors.