Regulation of Innate Immunity by F-Box Proteins

描述（由申请方提供）：严重肺炎或脓毒症诱导的肺损伤患者的一个临床特征是由入侵病原体引发的强烈急性炎症宿主反应。这里，在入侵的病原体激活免疫效应细胞（T细胞、巨噬细胞等）上的受体后，先天免疫系统被激活以分泌大量促炎细胞因子（即细胞因子风暴）。TRAF家族的衔接子分子是关键的和高度保守的蛋白质，其通过NF-kB依赖性信号传导将外表面信号（例如通过Toll受体）与细胞因子释放连接。因此，旨在选择性调节TRAF家族蛋白可用性的策略可能会减轻脓毒症的严重程度。然而，迄今为止，很少有人知道关于TRAF家族在蛋白质稳定性水平上的分子调控。在研究细菌性脓毒症的过程中，我们发现一个孤儿泛素E3连接酶亚基FBXO3被激活，足以泛素化并介导另一个相对较新的泛素E3连接酶亚基FBXL2的蛋白酶体降解。此外，我们发现FBXL2是抗炎的，因为它靶向TRAF蛋白家族，以将其处理在上皮细胞和单核细胞中。因此，我们的初步工作表明，铜绿假单胞菌，通过激活FBXO3，导致FBXL2泛素化和降解，导致增加的免疫反应性TRAF，增加细胞因子的产生，和受损的肺稳定性。这些数据导致了我们的新假设，即铜绿假单胞菌诱导的细胞因子释放涉及FBXO3介导的FBXL2的泛素化和降解，这反过来又增加了促炎的TRAF蛋白的水平。我们将确定孤儿泛素E3连接酶亚基FBXO3是否与GSK 3b协调以触发FBXL2的泛素化依赖性降解，这反过来激活TRAF蛋白以刺激细胞因子释放（Aim 1）。我们还将确定FBXO3的突变或抑制是否会减轻细菌诱导的急性肺损伤（目的2）。该提议提供了一种新的先天免疫模型，因为它涉及细胞因子信号传导。这些研究的实施将为严重细菌感染期间先天免疫应答的分子调节方面的重大机制进展奠定基础。这些研究的结果旨在作为开发高选择性新型FBXO3小分子抑制剂的策略的基础，以减轻细菌或脓毒症诱导的急性肺损伤的严重程度。

DESCRIPTION (provided by applicant): One clinical hallmark of patients with severe pneumonia or sepsis-induced lung injury is a robust acute inflammatory host response triggered by the invading pathogens. Here, the innate immunity system is activated to secrete large amounts of pro-inflammatory cytokines (i.e. a cytokine storm) after invading pathogens activate receptors on immune effector cells (T-cells, macrophages, etc.). The TRAF family of adaptors molecules are pivotal and highly conserved proteins that link external surface signals (e.g. via Toll receptors) to cytokine release via NF-kB dependent signaling. Thus, maneuvers designed to selectively modulate the availability of TRAF family proteins might lessen the severity of sepsis. However, to date, very little is known regarding the molecular regulation of the TRAF family at the level of protein stability. In the process of studying bacterial sepsis, we discovere that an orphan ubiquitin E3 ligase subunit, termed FBXO3, is activated and sufficient to ubiquitinate and mediate proteasomal degradation of another relatively new ubiquitin E3 ligase subunit, termed FBXL2. Further, we discovered that FBXL2 is anti-inflammatory as it targets the TRAF family of proteins for their disposal in epithelia and monocytes. Thus, our preliminary work demonstrates that P. aeruginosa, via activation of FBXO3, results in FBXL2 ubiquitination and degradation resulting in increased immunoreactive TRAFs, increased cytokine production, and impaired lung stability. These data led to our novel hypothesis that P. aeruginosa induced cytokine release involves FBXO3 mediated ubiquitination and degradation of FBXL2, which in turn increases levels of TRAF proteins which are pro-inflammatory. We will determine if an orphan ubiquitin E3 ligase subunit, FBXO3, coordinates with GSK3b to trigger ubiquitination dependent degradation of FBXL2, which in turn activates TRAF proteins to stimulate cytokine release (Aim 1). We will also determine if mutation or inhibition of FBXO3 will attenuate bacterial-induced acute lung injury (Aim 2). This proposal provides a new model of innate immunity as it relates to cytokine signaling. Execution of these studies will lay the foundation fo a significant mechanistic advance regarding the molecular regulation of the innate immune response during severe bacterial infection. Results from these studies are intended to serve as the basis for strategies directed at the development of highly selective novel small molecule inhibitors of FBXO3 to lessen the severity of bacterial or sepsis-induced acute lung injury.