Understanding the Role GPRC6a During Tau Metabolism

了解 GPRC6a 在 Tau 代谢过程中的作用

• 批准号: 10338842
• 负责人: Daniel Carl Lee
• 金额: --
• 依托单位: UNIVERSITY OF KENTUCKY
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-07-01 至 2024-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10338842
• 关键词: Understanding; Role; GPRC6a; During; Tau

Tauopathies including Alzheimer's disease (AD) consist of age-associated neurodegenerative diseases for which no disease-modifying treatments exist. Our group has uncovered a unique interaction between the arginine metabolism and tauopathies. Arginine metabolism affects multiple biological processes that show considerable influence upon tau biology. We hypothesize that L-arginine acts as a sensor for amino acid abundance and that the depletion of arginine initiates autophagy to replenish amino acid levels. Arginase 1 (Arg1) remains one of several different enzymes capable of metabolizing the semi-essential amino acid L- arginine. In fact numerous isoforms exist for Arg and nitric oxide synthases (NOS). We demonstrate in cells and animal models of tauopathy the benefits of increasing Arg1 in reducing many aspects of the tau phenotype (hallmarks comprised of tau effects). Several seminal findings show lysosomal and cytoplasmic arginine sensors that modulate mechanistic target of rapamycin complex 1 (mTORC1). GPRC6a is a G-protein coupled receptor that binds L-α amino acids including L-arginine and may serve as an extracellular arginine sensor for mTORC1. Our preliminary data indicates increased activation of the arginine-sensing mTORC1 pathway in AD brains and animal models of tauopathies. We show that arginine producing and metabolizing enzymes, arginine sensors, and mTORC1 complexes increase in the hippocampus of AD patients compared to control aged matched brains. We also find that tau increased total arginine levels in the brain by 35%, increased basal levels of extracellular arginine and arginine release following neuronal stimulation in the brain. Furthermore, novel allosteric antagonist to GPRC6a clears various forms of tau in cell lines, primary neurons, and mice. Genetic reduction of GPRC6a also reduced tau expression and seemingly regulates several intracellular arginine sensors. We posit that tauopathies (including AD) cause impaired arginine metabolism and uncoupling of arginine-sensing mTORC1 signaling, which lead to hyper-mTORC1 activation creating a positive feed- forward loop to augment the tau phenotype. We will test the hypothesis that decreased GPRC6a signaling from allosteric antagonists or shRNA to GPRC6a modulate arginine-sensing mTORC1 signaling, induces autophagy and increases tau clearance in vitro and in vivo. We will use tetracycline inducible tau cell lines with a photo- switchable fluorescent tracer to measure tau metabolism, split tau-GFP constructs that measure tau oligomerization, and primary neurons to determine the role of GPRC6a and tau fate. We will determine if genetic knockdown and pharmacological inhibition of GPRC6a impacts tau biology in vitro and in vivo. Success in this application would provide a new receptor target that may impact arginine-sensing mTORC1 signaling. Furthermore, we aim to identify an entirely new class of drugs that targets GPCR6a to mitigate the tau phenotype provide new strategies for tauopathies and AD.

包括阿尔茨海默氏病（AD）在内的TAUOPADY包括与年龄相关的神经退行性疾病 不存在调整疾病的治疗方法。我们的小组发现了 精氨酸的代谢和扭曲病。精氨酸代谢会影响显示的多种生物学过程 对tau生物学的影响很大。我们假设L-精氨酸充当氨基酸的传感器 抽象及其部署精氨酸会引发自噬以复制氨基酸水平。精氨酸酶1 （arg1）仍然是能够代谢半必定氨基酸l-的几种不同的酶之一 精氨酸。实际上，ARG和一氧化氮合酶（NOS）存在许多同工型。我们在细胞中演示 和tauopathy的动物模型，增加了arg1在减少tau表型的许多方面的好处 （包括tau效应的标志）。几个第二个发现显示溶酶体和细胞质精氨酸 调节雷帕霉素复合物1（MTORC1）的机械靶标的传感器。 GPRC6A是G蛋白耦合的 结合包括L-精氨酸在内的L-α氨基酸的受体，可以用作细胞外精氨酸传感器 mtorc1。我们的初步数据表明AD中精氨酸感应MTORC1途径的激活增加 大脑和动物模型。我们表明精氨酸的产生和代谢酶， 与对照相比 老化的大脑。我们还发现，tau在大脑中的总精氨酸水平增加了35％，基本 大脑神经元刺激后细胞外精氨酸和精氨酸释放的水平。此外， GPRC6A的新型变构拮抗剂清除了细胞系，原发性神经元和小鼠中的各种形式的tau。 GPRC6A的遗传降低也降低了Tau表达，似乎调节了几个细胞内 精氨酸传感器。我们肯定的是，tauopathies（包括AD）会导致精氨酸代谢受损和解偶联 精氨酸感应MTORC1信号传导，这导致高MTORC1激活产生正馈 向前循环增强tau表型。我们将测试以下假设，即从 变构拮抗剂或shRNA至GPRC6A调节精氨酸感应MTORC1信号，诱导自噬 并增加体外和体内的tau清除率。我们将使用四环素诱导的tau细胞系与光 可切换的荧光示踪剂以测量Tau代谢，分裂Tau-GFP构造，以测量tau 寡聚和原发性神经元确定GPRC6A和TAU命运的作用。我们将确定是否 GPRC6A的遗传敲低和药物抑制会影响Tau生物学体外和体内。成功 在此应用中，将提供一个新的受体靶标，可能会影响精氨酸感应MTORC1信号传导。 此外，我们旨在确定针对GPCR6A的全新药物以减轻tau 表型为扭曲和AD提供了新的策略。