Role of EPS8-mediated RAC activation in disease-related protein aggregation

EPS8介导的RAC激活在疾病相关蛋白聚集中的作用

• 批准号: 455072713
• 负责人: Professor Dr. David Vilchez
• 金额: --
• 依托单位: Institut für Genetik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/455072713?language=en
• 关键词: Role; EPS8; mediated; RAC; activation

Aging is a major risk factor for neurodegenerative diseases that involve protein aggregation, including amyotrophic lateral sclerosis, Huntington’s, Parkinson’s and Alzheimer’s. The discovery of pathways that slow down the aging process has revolutionized the field of molecular gerontology, suggesting the realistic possibility of creating therapeutics to prevent age-related neurodegenerative diseases. However, the mechanisms underlying aging and their impact on age-related diseases are only beginning to be unraveled at the molecular level. In the previous DFG grant, we found a remodeling of the ubiquitinated proteome during aging, which was ameliorated by longevity paradigms such as dietary restriction and reduced insulin signaling. Notably, aging caused a global loss of ubiquitination that was triggered by increased deubiquitinase (DUB) activity. Because ubiquitination can tag proteins for recognition by the proteasome, a fundamental question was whether deficits in targeted degradation influence longevity. By integrating data from worms with a defective proteasome, we identified proteasomal targets that accumulate with age owing to decreased ubiquitination and subsequent degradation. Lowering the levels of age-dysregulated proteasome targets prolonged longevity, whereas preventing their degradation shortened lifespan. Among the proteasomal targets, we found the IFB-2 intermediate filament and the EPS-8 modulator of RAC signaling. While increased levels of IFB-2 promoted the loss of intestinal integrity, upregulation of EPS-8 hyperactivated RAC in muscle and neurons, and led to alterations in the actin cytoskeleton and protein kinase JNK. An exciting hypothesis raised by these results is whether regulatory proteins that escape proteasomal degradation with aging have a role in the development of age-related disorders that involve protein aggregation. Indeed, our preliminary results indicate that lowering EPS-8/RAC signaling, but not IFB-2, prevents aggregation of proteins linked with neurodegenerative diseases such as Huntington’s and amyotrophic lateral sclerosis in C. elegans disease models. In this renewal application, we propose to define the impact of EPS-8/RAC in disease-related protein aggregation and subsequent physiological consequences using different C. elegans and human cell models. Then, we will define whether hyperactivated EPS8/RAC signaling modulates disease-related protein aggregation through its role in actin and/or JNK regulation. Finally, we will define the DUBs that deubiquitinate and suppress proteasomal degradation of EPS-8. Importantly, our preliminary data indicate that knockdown of USP4, a DUB that becomes upregulated with age, phenocopies the beneficial effects of lowering EPS8/RAC signaling in C. elegans and human cells. Together, our findings could lead to converging therapeutic approaches for distinct age-related neurodegenerative disorders.

衰老是涉及蛋白质聚集的神经退行性疾病的主要风险因素，包括肌萎缩性侧索硬化症、亨廷顿氏病、帕金森氏病和阿尔茨海默氏病。减缓衰老过程的途径的发现彻底改变了分子老年学领域，表明创造治疗方法以预防与年龄相关的神经退行性疾病的现实可能性。然而，衰老的机制及其对年龄相关疾病的影响才刚刚开始在分子水平上被揭开。在之前的DFG资助中，我们发现了衰老过程中泛素化蛋白质组的重塑，这是通过长寿范例如饮食限制和减少胰岛素信号传导来改善的。值得注意的是，衰老导致了由去泛素化酶（DUB）活性增加引发的泛素化的整体丧失。由于泛素化可以标记蛋白质，使其被蛋白酶体识别，因此一个基本问题是靶向降解的缺陷是否会影响寿命。通过整合蠕虫与缺陷蛋白酶体的数据，我们确定了蛋白酶体的目标，随着年龄的增长，由于减少泛素化和随后的降解积累。降低年龄失调的蛋白酶体水平可以延长寿命，而防止其降解则会缩短寿命。在蛋白酶体靶点中，我们发现了IFB-2中间丝和RAC信号的EPS-8调节剂。虽然IFB-2水平的增加促进了肠道完整性的丧失，但EPS-8的上调过度激活了肌肉和神经元中的RAC，并导致肌动蛋白细胞骨架和蛋白激酶JNK的改变。这些结果提出了一个令人兴奋的假设，即随着年龄的增长，逃避蛋白酶体降解的调节蛋白是否在涉及蛋白质聚集的年龄相关疾病的发展中发挥作用。事实上，我们的初步结果表明，降低EPS-8/RAC信号，而不是IFB-2，防止与神经退行性疾病，如亨廷顿和肌萎缩侧索硬化症在C。elegans疾病模型。在此更新申请中，我们建议使用不同的C.线虫和人类细胞模型。然后，我们将确定是否超活化的EPS 8/RAC信号调节疾病相关的蛋白质聚集通过其在肌动蛋白和/或JNK调节的作用。最后，我们将定义去泛素化和抑制EPS-8的蛋白酶体降解的DUBs。重要的是，我们的初步数据表明，USP 4（一种随着年龄增长而上调的DUB）的敲低，表型模仿了降低C.线虫和人类细胞。总之，我们的研究结果可能会导致不同的年龄相关的神经退行性疾病的融合治疗方法。