Enhancement of Protein Breakdown through PKG-mediated Phosphorylation of the Proteasome

项目摘要/摘要 泛素蛋白酶体系统(UPS)降解哺乳动物细胞中的大多数蛋白质和一种 它的主要功能之一是选择性地消除错误折叠的、潜在的有毒蛋白质。在UPS中，蛋白质 底物通过连接泛素分子链进行修饰，泛素分子以蛋白质为靶点进行快速 26S蛋白酶体的降解。通常认为泛素化决定了蛋白质的速率。 被UPS降解，但最近的研究表明，26S蛋白酶体的活性密切相关 调节并可以确定细胞中蛋白质的降解率。我们的实验室和合作者最近发现 升高cAMP的药物导致蛋白激酶A介导的26S亚单位Rpn6的磷酸化和 增强多种蛋白酶体的活性。这一修改增加了细胞和小鼠的容量 大脑降解错误折叠的容易聚集的蛋白质(例如突变的Tau和SOD1)，从而导致 神经退行性疾病。因此，药物增强蛋白酶体功能是一个令人兴奋的新课题。 与各种与衰老相关的疾病作斗争的方法。 我最近发现，提高cGMP和激活蛋白激酶G的治疗也会刺激 细胞内蛋白酶体活性和蛋白质降解。这种cGMP介导的刺激不是由于Rpn6 磷酸化，因此发生的机制不同于升高cAMP。我正在提议一项深入的 调查以确定1.)升高cGMP如何刺激蛋白酶体功能，2。提高cGMP水平的效果 对不同类型细胞蛋白的降解和3.)FDA批准的药剂是否 增加cGMP水平(例如，PDE5抑制剂)可增强引起 阿尔茨海默病，肌萎缩侧索硬化症，额颞叶痴呆和帕金森病。 这些研究应该阐明这种新的蛋白质调节模式的机制和重要性。 降解及其治疗潜力。

Project Summary / Abstract The ubiquitin proteasome system (UPS) degrades the majority of proteins in mammalian cells and one of its primary functions is to selectively eliminate misfolded, potentially toxic proteins. In the UPS, protein substrates are modified by the attachment of chains of ubiquitin molecules, which target the protein for rapid degradation by the 26S proteasome. It is generally assumed that ubiquitination determines the rate of protein degradation by the UPS, but recent studies have shown that the activity of 26S proteasomes is tightly regulated and can determine rates of protein degradation in cells. Our lab and collaborators recently found that agents that raise cAMP cause the Protein Kinase A-mediated phosphorylation of the 26S subunit Rpn6 and the enhancement of multiple proteasome activities. This modification increases the capacity in cells and mouse brains to degrade misfolded, aggregation-prone proteins (e.g. mutant Tau and SOD1) that cause neurodegenerative diseases. Thus, pharmacological enhancement of proteasome function is an exciting new approach to combat various aging-associated diseases. I recently found that treatments that raise cGMP and activate Protein Kinase G also stimulate proteasome activity and protein degradation in cells. This cGMP-mediated stimulation was not due to Rpn6 phosphorylation, and therefore occurs by a different mechanism than raising cAMP. I am proposing an in-depth investigation to determine 1.) how raising cGMP stimulates proteasome function, 2.) the effect of raising cGMP on the degradation of different types of cell proteins and 3.) whether FDA-approved pharmacological agents that increase cGMP levels (e.g. PDE5 inhibitors) enhance the clearance of mutant proteins that cause Alzheimer’s Disease, Amyotrophic Lateral Sclerosis, Frontotemporal Dementia, and Parkinson’s Disease. These studies should clarify the mechanisms and importance of this new mode of regulating protein degradation and its therapeutic potential.