The role of Usp14 in regulating neuronal function

描述（由申请人提供）：泛素-蛋白酶体系统（UPS）是所有真核细胞共同的调节蛋白质周转的中心途径。有许多调节途径依赖于及时去除关键蛋白质。这些途径包括细胞周期、DNA修复、受体介导的内吞作用和长期记忆的诱导。无法从细胞中去除不需要的蛋白质与几种慢性神经系统疾病有关，包括帕金森病，阿尔茨海默病和脊髓小脑共济失调。虽然很明显这些疾病与多聚泛素化蛋白聚集体有关，但尚不清楚这些聚集体如何导致神经元功能障碍。与靶向蛋白质进行蛋白酶体降解的多泛素化信号相反，单泛素标签可以发出受体内化和细胞内囊泡分选的信号。这种修饰是可逆的，类似于磷酸化，可以调节蛋白质的定位和活性。我们最近证明，Uspl 4（一种特异性从蛋白质中去除泛蛋白的去遍在蛋白酶（DUB））在神经学小鼠突变型共济失调（ax/j）中发生突变。axJ小鼠未显示蛋白质聚集缺陷或神经元损失。相反，这些小鼠表现出突触传递的缺陷，表明神经系统疾病可能源于突触功能障碍。我们的工作假设是，Uspl 4的丢失破坏了神经递质释放机制的特定组分的泛素化状态，从而导致突触缺陷。因此，该提议旨在解决Uspl 4在调节突触功能中的作用。第一个目标是确定Usp 14是否与神经元中的26 S蛋白酶体相关，以及它是否在泛素依赖的蛋白水解中起作用。在第二个目标中，我们将确定由Usp 14调节的组分和途径，以便更好地了解正常生理和疾病中泛素修饰的调节。第三个具体目标将确定哪些神经元回路被Usp 14的丢失破坏，并检查这些回路如何导致ax J小鼠的震颤、共济失调和肌肉萎缩表型。这些特定目标的完成将使我们能够发现依赖于泛素信号传导的新过程，并确定这些途径的改变如何导致神经系统疾病。

DESCRIPTION (provided by applicant): The ubiquitin-proteasome system (UPS) is a central pathway common to all eukaryotic cells for regulating protein turnover. There are numerous regulatory pathways that rely on the timely removal of critical proteins. These pathways include the cell cycle, DNA repair, receptor-mediated endocytosis and the induction of long-term memory. The inability to remove unwanted proteins from cells has been linked to several chronic neurological diseases including Parkinson's disease, Alzheimer's disease, and the Spinocerebellar ataxias. While it is clear that these diseases are associated with polyubiquitinated protein aggregates, it is not clear how these aggregates contribute to neuronal dysfunction. In contrast to the polyubiquitination signal that targets proteins for proteasomal degradation, a monoubiquintin tag can signal receptor internalization and sorting of intracellular vesicles. This modification by monoubiquitin is reversible and, akin to phosphorylation, can regulate protein localization and activity. We have recently demonstrated that Uspl4, a deubiquitinating enzyme (DUB) that specifically removes ubiquitin from proteins, is mutated in the neurological mouse mutant ataxia (ax/j). The axJ mice do not show protein aggregation defects or neuronal loss. Instead, these mice exhibit defects in synaptic transmission, indicating that neurological disease may be rooted in synaptic dysfunction. Our working hypothesis is that loss of Uspl4 disrupts the ubiquitinated state of specific components of the neurotransmitter release machinery, thereby resulting in synaptic defects. This proposal is therefore directed at addressing the role of Uspl4 in regulating synaptic function. The first Aim will determine if Usp 14 associates with the 26S proteasome in neurons and if it has a role in ubiquitin-dependent proteolysis. In the second Aim, we will identify components and pathways that are regulated by Usp14 in order to better understand the regulation of ubiquitin modification in normal physiology and disease. The third Specific Aim will determine which neuronal circuits are disrupted by the loss of Uspl4 and examine how these circuits contribute to the tremor, ataxia and muscle wasting phenotypes of the ax J mice. Completion of these Specific Aims will enable us to uncover new processes that rely on ubiquitin-signaling and to determine how alterations in these pathways can lead to neurological disease.