Mechanism of degradation of the proteasome through autophagy

 描述（由申请人提供）：两种细胞组分，溶酶体（酵母和植物中的液泡）和蛋白酶体降解真核细胞中的大多数蛋白质。它们在衬底中显示部分重叠，并且已经观察到它们之间的串扰。因此，为了了解细胞降解蛋白质的能力，重要的是要知道蛋白酶体的细胞水平是如何控制的。虽然已经在酵母和哺乳动物细胞中研究了蛋白酶体的转录调控，但是关于靶向蛋白酶体降解的机制或生理条件知之甚少。通过降解降低蛋白酶体水平可以影响许多细胞过程并增加细胞对药物的敏感性。这可能与治疗相关，因为细胞可能对蛋白酶体抑制剂更敏感，如FDA批准的用于治疗多发性骨髓瘤和套细胞淋巴瘤的药物Bortezalide和Carfizalide。本文提出的研究目的是通过生物化学和细胞生物学分析，在分子水平上阐明导致蛋白酶体降解的信号通路和生物学过程。由于许多蛋白酶体相关过程在真核生物中是高度保守的，并且对此过程知之甚少，因此酵母将被用作模式生物。这将提供更广泛的技术和筛选能力，以确定所涉及的基本机制。根据我们的初步数据，提出了两个不同的过程，导致蛋白酶体降解。目标1将确定如何整体蛋白酶体水平降低氮饥饿。目的是鉴定蛋白质、翻译后修饰和在氮饥饿时参与核输出和自噬包装过程的其他信号。目的2将检验以下假设：未能进行质量控制的蛋白酶体通过自噬被特异性地去除。目标是确定识别错误蛋白酶体的因子如何将这些复合物与自噬途径联系起来，从而靶向它们进行溶酶体降解。 这些目标的预期结果是识别和分子理解导致蛋白酶体靶向自噬的过程。了解这些途径将是重要的未来表征这些过程对人类健康相关条件的影响。这可能包括营养缺乏的癌细胞， 增加的氧化应激、衰老或神经退行性疾病，这些都已被证明受到泛素-蛋白酶体系统的影响。

 DESCRIPTION (provided by applicant): Two cellular components, the lysosome (vacuole in yeast and plants) and the proteasome degrade the majority of proteins in eukaryotic cells. They display a partial overlap in substrates and crosstalk between them has been observed. Therefore, to understand the cells ability to degrade proteins it is important to know how the cellular level of the proteasome is controlled. While transcriptional regulation of proteasomes has been studied in yeast and mammalian cells, little is known concerning the mechanism or physiological conditions that target proteasomes for degradation. Reducing proteasome levels through degradation can impact many cellular processes and increase a cell's sensitivity to drugs. This can be therapeutically relevant, because cells can become more sensitive to proteasome inhibitors, like the FDA approved drugs Bortezomib and Carfizomib used in the treatment of multiple myelomas and mantle cell lymphomas. The objective of the research proposed here is to elucidate at the molecular level the signal pathways and biological processes that lead to the degradation of proteasomes by using biochemical and cell biological assays. Since many proteasome related processes are highly conserved amongst eukaryotes and little is known about this process, yeast will be used as a model organism. This will provide a wider array of techniques and screening abilities to determine the basic mechanism involved. Based on our preliminary data, two distinct processes are proposed to lead to proteasome degradation. Aim 1 will determine how overall proteasome levels are reduced upon nitrogen starvation. The goal is to identify proteins, post- translational modifications, and other signals involved in the process of nuclear export and autophagic packaging upon nitrogen starvation. Aim 2 will test the hypothesis that proteasomes that fail quality control are specifically removed via autophagy. The goal is to determine how factors that recognize faulty proteasomes link these complexes to the autophagy pathway that targets them for lysosomal degradation. The expected outcomes from these aims are the identification and a molecular understanding of the process that leads to targeting of proteasomes for autophagy. Understanding of these pathways will be important for future characterization of the impact these processes have on conditions that are relevant for human health. This can include conditions like nutrient starved cancer cells, increased oxidative stress, aging, or neurodegenerative diseases, which all have been shown to be impacted by the ubiquitin- proteasome system.