SCF-based Ubiquitin E3 Ligases in the Pathobiology of Pneumonia

描述（由申请人提供）： 肺炎是退伍军人死亡的主要原因。 肺炎的一个标志是由宿主细胞细胞因子的大量释放引起的急性肺损伤。肿瘤坏死因子受体相关因子（TRAF）蛋白在介导细胞因子反应中起关键作用，但对其分子调控知之甚少。在这里，我们表明，泛素E3连接酶亚基，被称为F盒蛋白FBXL2，作为一个哨兵抑制剂，介导处理TRAF蛋白，损害促炎细胞的细胞因子分泌。 此外，我们发现一种相对较新的蛋白质，称为F盒蛋白FBX03，靶向FBXL2降解，从而刺激细胞因子释放。FBX03具有类似细菌的分子特征，导致了一种有效的抗炎剂BC1215的开发。在缺乏稳健表达细胞因子的能力的人类受试者中也鉴定了功能丧失的天然存在的FBX03突变。因此，在本提案中，我们将检验以下假设：FBX03的拮抗作用或突变通过保持FBXL2的水平而导致肺炎急性肺损伤的严重程度降低，FBXL2进而介导促炎性TRAF蛋白的降解。为了评估这一假设，我们将确定在实验性肺炎期间，FBXO3是否通过TRAF抑制剂FBXL2的降解稳定TRAF蛋白来刺激细胞因子释放（目的1），确定新型小分子FBXO3拮抗剂BC 1215是否减轻实验性肺炎期间急性肺损伤的严重程度（目的2），并确定是否自然发生的FBXO3点突变降低住院退伍军人肺炎期间急性肺损伤的严重程度（目的3）。总之，本申请揭示了先天免疫的新分子模型，因为它涉及细胞因子信号传导。这些研究的执行将为炎症病理生物学的基本概念进步奠定基础，为退伍军人肺炎的新翻译倡议奠定基础。

DESCRIPTION (provided by applicant): Pheumonia is a leading cause of death among Veterans. A hallmark of pheumonia is acute lung injury resulting from a profound release of host cell cytokines. The tumor necrosis factor receptor associated factor (TRAF) proteins are critical in mediating cytokines responses, but little is known regarding their molecular regulation. Here we show that a ubiquitin E3 ligase subunit, termed F box protein FBXL2, serves as a sentinel inhibitor that mediates disposal of TRAF proteins to impair cytokines secretion in pro-inflammatory cells. Further, we discovered that a relatively new protein, termed F box protein FBX03, targets FBXL2 for degradation thereby stimulating cytokine release. FBX03 harbors a bacterial-like molecular signature that led to the development of a potent anti-inflammatory agent, BC1215. A loss-of-function naturally occurring FBX03 mutation was also identified in human subjects that lack ability to robustly express cytokines. Thus, in this proposal, we will test the hypothesis that antagonism or mutation of FBX03 results in reduced severity of acute lung injury from pneumonia by preserving levels of FBXL2, which in turn mediates degradation of TRAF proteins that are pro-inflammatory. To Evaluate this hypothesis,we will determine if during experimental pneumonia FBXO3 stimulates cytokine release by stabilizing TRAF proteins via degradation of the TRAF inhibitor, FBXL2 (Aim 1), determine if a novel small molecule FBXO3 antagonist, BC1215, lessens severity of acute lung injury during experimental pneumonia (Aim 2), and determine if a naturally occurring FBXO3 point mutation reduces severity of acute lung injury during pneumonia in hospitalized Veterans (Aim 3). In summary, this application unveils a new molecular model of innate immunity as it relates to cytokine signaling. Execution of these studies will lay the groundwork for a fundamental conceptual advance in the pathobiology of inflammation that sets the stage for a new translational initiative in Veterans with pneumonia.