The role of linear ubiquitination in protein aggregation

为了维持神经元的活力和稳态，神经元依赖于有效的应激反应和质量控制途径。这些系统的不平衡与衰老和各种神经退行性疾病有关。这些途径中的大多数（如果不是全部的话）都受到泛素化的调节，例如蛋白酶体降解、自噬和细胞器应激反应程序。我们的初步结果表明，线性泛素组装复合物（LUBAC）被招募到与神经退行性疾病相关的错误折叠蛋白质物种，如具有延长的聚谷氨酰胺束的突变亨廷顿蛋白。因此，错误折叠的亨廷顿蛋白被线性多聚泛素链修饰，导致其神经元毒性显著降低。基于这些观察结果，我们提出，细胞质蛋白质聚集体被认为是一种特殊的“细胞病原体”，导致招募和激活LUBAC，对神经元蛋白质稳态和活力具有有益的影响。该建议的目的是描述LUBAC在预防蛋白毒性应激中的功能并阐明其潜在机制。我们将结合联合收割机和生物化学的方法来实验解决以下目标：目标1：分析线性泛素化如何影响Htt聚集毒性目标2：解决LUBAC对其他聚集倾向蛋白的影响目标3：探索NEMO在维持蛋白质稳态中的可能作用

To maintain neuronal viability and homeostasis, neurons depend on efficient stress response and quality control pathways. Imbalances in these systems are associated with aging and various neurodegenerative diseases. Most if not all of these pathways are regulated by ubiquitination, such as proteasomal degradation, autophagy, and organellar stress response programs. Our preliminary results revealed that the linear ubiquitin assembly complex (LUBAC) is recruited to misfolded protein species associated with neurodegenerative diseases, such as mutant huntingtin with an elongated poly-glutamine tract. As a consequence, misfolded huntingtin is modified with linear polyubiquitin chains, resulting in a marked decrease of its neuronal toxicity. Based on these observations, we propose that cytoplasmic protein aggregates are sensed as a special kind of "cellular pathogens", resulting in the recruitment and activation of LUBAC with beneficial effects on neuronal proteostasis and viability. The aim of this proposal is to characterize the function of LUBAC in preventing proteotoxic stress and to elucidate the underlying mechanisms. We will combine imaging and biochemical approaches to experimentally address the following objectives:Objective 1: To analyze how linear ubiquitination influences Htt aggregate toxicityObjective 2: To address the impact of LUBAC on other aggregation-prone proteinsObjective 3: To explore a possible role of NEMO in maintaining proteostasis