Biomedical Research and Research Training

项目总结 肿瘤坏死因子是一种重要的细胞因子，协调细胞因子的产生、炎症、细胞 存活和细胞死亡。生死决定是如何对肿瘤坏死因子做出反应的，目前还不完全清楚。 几个分子事件决定了肿瘤坏死因子对细胞的刺激是否会导致转录反应 促进细胞存活或是否会导致细胞死亡。肿瘤坏死因子受体下游的信号是重要的 受翻译后修饰的调节，包括泛素化。LUBAC，一种泛素(Ub)E3连接酶，由 由Sharpin、HOIL和HOIP组成的Ub连接酶是迄今为止所描述的唯一一种能够修饰具有线性Ub链的蛋白质的Ub连接酶 (MET1-Ub链)。LUBAC活性是肿瘤坏死因子依赖的生存基因转录所必需的 刺激。来自LUBAC组分胚系突变患者的细胞可引发核因子-kB缺陷 依赖基因转录和细胞死亡途径的异常激活。同样，小鼠模型与 LUBAC成分缺陷会导致慢性炎症和多个器官和组织中细胞凋亡的增加。 我们发表的研究表明，细胞死亡，而不是依赖于核因子-kB的基因转录缺陷， 在LUBAC缺陷(Sharpincpdm)动物中，这种表型推动了肿瘤坏死因子依赖的慢性炎症 被FADD--死亡诱导信号的重要组成部分--的复合缺陷所逆转 很复杂。这一认识使我们提出了这样的假设，即LUBAC活性是预防细胞死亡的直接必要条件 死亡。在目标1中，我们将讨论MET1-Ub修饰蛋白质靶标的分子基础 锁链。我们将讨论LUBAC如何使用MET1-Ub链修改FADD。在目标2中，我们将描述 FADD修饰在细胞中的功能相关性，并使用一种新的基于Ub的工具来丰富MET1-Ub链。在……里面 目的3研究LUBAC自身泛素化的功能以及磷酸化如何调节 LUBAC的线性Ub链形成活性。我们的研究将提供对原发疾病病因的机械性见解。 与LUBAC成分胚系突变患者相关的免疫缺陷。

PROJECT SUMMARY Tumor necrosis factor (TNF) is an important cytokine that coordinates cytokine production, inflammation, cell survival, and cell death. How life and death decisions are made in response to TNF is not completely understood. Several molecular events determine whether TNF stimulation of cells leads to a transcriptional response that promotes cell survival or whether it can lead to cell death. Signaling downstream of the TNF receptor is heavily regulated by post-translation modifications including ubiquitination. LUBAC, a ubiquitin (Ub) E3 ligase consisting of Sharpin, HOIL and HOIP, is the only Ub ligase described to date that can modify proteins with linear Ub chains (Met1-Ub chains). LUBAC activity is essential for NF-kB dependent transcription of prosurvival genes upon TNF stimulation. Cells derived from patients with germline mutations in LUBAC components elicit defective NF-kB- dependent gene transcription and aberrant activation of cell death pathways. Similarly, murine models with defective LUBAC components elicit chronic inflammation and increased apoptosis in multiple organs and tissues. Our published studies indicate that cell death, rather than a deficiency in NF-kB dependent gene transcription, in LUBAC-deficient (sharpincpdm) animals is driving the TNF-dependent chronic inflammation as this phenotype is reversed by a compound deficiency in FADD—an important component of the death inducing signaling complex. This insight led us to the hypothesis that LUBAC activity is directly required for the prevention of cell death. In aim 1, we will address the molecular basis for LUBAC modification of protein targets with Met1-Ub chains. We will address how LUBAC can modify FADD with Met1-Ub chains. In aim 2, we will characterize the functional relevance of FADD modification in cells and use a new Ub-based tool to enrich for Met1-Ub chains. In aim 3, we will investigate the function of LUBAC auto-ubiquitination and how phosphorylation can regulate LUBAC’s linear Ub chain forming activity. Our studies will provide mechanistic insight into the etiology of primary immune deficiencies associated with patients with germline mutations in LUBAC components.