Functional role of the ubiquitin specific protease 8 (USP8/UBPy) in T cells

泛素对蛋白质的修饰控制着多种基本的生物学过程，并被去泛素化酶的活性所抵消。UBPy（USP 8）是人类基因组中编码的80多种去泛素化酶之一。我们能够表明，UBPy调节受体酪氨酸激酶的稳定性，并且对于体内适当的内体分选是必需的。使用cre-loXP介导的基因靶向，我们产生了T细胞特异性缺失UBPy（ΔT-UBPy）的小鼠，以分析这种遍在蛋白异肽酶在T细胞中的功能，其中关键信号分子的多效性由遍在蛋白介导的机制控制。ΔT-UBPy小鼠表现出过早死亡并发展为严重的炎性肠病（IBD）。胸腺、淋巴结和脾脏中的CD 4+和CD 8+单阳性T细胞强烈减少，并且在刺激后ΔT-UBPy胸腺细胞显示出降低的增殖能力。给出的结果揭示了UBPy在T细胞功能中的重要作用。使用这个模型系统，我们将阐明由USP 8介导的分子和细胞机制，以获得关于泛素蛋白酶体系统和泛素修饰在T细胞信号传导中的作用的新见解。一个特别的重点将是泛素去缀合的调节，特异性和功能作用，这是迄今为止知之甚少。ΔT-UBPy小鼠作为IBD的新型模型系统也可能有助于更好地理解人类自身免疫性疾病克罗恩病和溃疡性结肠炎的分子机制。

Protein modification by ubiquitin controls a wide variety of basic biological processes and is counteracted by the activity of deubiquitinating enzymes. UBPy (USP8) is one of more than 80 deubiquitinating enzymes encoded in the human genome. We were able to show that UBPy regulates the stability of receptor tyrosine kinases and is essential for proper endosomal sorting in vivo. Using cre-loxP mediated gene targeting we have generated mice with T-cell specific deletion of UBPy (ΔT-UBPy) in order to analyze the function of this ubiquitin isopeptidase in T-cells, where a pleiotropy of key signalling molecules are controlled by ubiquitin mediated mechanisms. ΔT-UBPy mice show premature death and develop a severe inflammatory bowel disease (IBD). CD4+ and CD8+ single positive T-cells in thymus, lymph node and spleen are strongly reduced and upon stimulation ΔT-UBPy thymocytes showed reduced proliferative capacity. Given results reveal an essential role of UBPy in T-cell function. Using this model system we will elucidate the molecular and cellular mechanisms mediated by USP8 to gain novel insights about the role of the ubiquitin proteasome system and ubiquitin modification in T-cell signalling. A particular focus will be the regulation, specificity and functional role of ubiquitin deconjugation, which is so far poorly understood. ΔT-UBPy mice as a novel model system for IBD might also help to better understand the molecular mechanisms underlying the human autoimmune disorders Crohns- disease and ulcerative colitis.