Regulatory targets and pathogenic mechanisms of anthrax edema factor

描述(申请人提供)：炭疽芽孢杆菌是炭疽病的病原体，能产生三种毒素多肽：保护性抗原(PA)、致死因子(LF)和水肿因子(EF)。PA与宿主细胞表面表达的受体结合，允许LF和EF进入细胞。通过在培养的巨噬细胞和动物模型中研究LF的作用，已经广泛地研究了LF在炭疽病发病中的作用。相比之下，对EF的调控靶点和致病机制知之甚少。我们发现，EF具有腺苷环化酶活性，在体外可以促进巨噬细胞的运动和存活。我们的初步数据还表明，EF抑制某些促炎细胞因子的产生，同时激活包括细胞因子血管内皮生长因子(VEGF)在内的一些新的靶基因。众所周知，血管内皮生长因子可增加血管通透性，从而导致水肿，还能促进淋巴管和血管的生长。基于这些发现，我们认为EF可能在促进炭疽杆菌感染的巨噬细胞向淋巴结迁移和细菌向血液循环扩散方面发挥作用。为了验证这一想法，我们计划追求以下特定目标：1)确定将cAMP信号与巨噬细胞中EF靶基因的表达联系起来的转录因子；2)确定EF促进巨噬细胞运动和存活的机制；以及3)确定EF激活巨噬细胞中VEGF表达和小鼠淋巴管生成的机制。除了更好地了解炭疽病的发病机制外，我们的目标是通过调节EF靶向宿主蛋白的功能来设计一种有效的方法来防止炭疽杆菌向致命的系统性感染扩散。与公共卫生相关：我们正在调查炭疽菌操纵巨噬细胞的机制，巨噬细胞是免疫系统第一次打击的主要细胞参与者，扰乱信号系统并征用细胞作为运输工具，从而允许细菌在体内传播。利用培养的巨噬细胞和小鼠，我们将确切地研究由炭疽菌产生的一种毒素蛋白--水肿因子如何激活宿主基因，从而指导这种致命细菌的传播。我们希望，这些努力将导致发现治疗炭疽病和其他传染病的新目标。

DESCRIPTION (provided by applicant): Bacillus anthracis, the causative agent of anthrax, produces three toxin polypeptides: protective antigen (PA), lethal factor (LF) and edema factor (EF). PA binds to receptors expressed on the surface of host cells and allows cellular entry of LF and EF. The function of LF in anthrax pathogenesis has been extensively studied by investigating its action in both cultured macrophages and animal models. By contrast, very little is known about the regulatory targets and pathogenic mechanism of EF. We found that EF, with its adenylate cyclase activity, promotes motility and survival of macrophages in vitro. Our preliminary data also suggest that EF suppresses production of certain proinflammatory cytokines while activating a number of novel target genes that include the cytokine vascular endothelial growth factor (VEGF). VEGF is known to increase vascular permeability, thereby causing edema, and also promote the growth of lymphatic and blood vessels. Based on these findings, we propose that EF may play a role in accelerating the migration of B. anthracis-infected macrophages to lymph nodes and spreading of the bacterium to the blood circulation. To test this idea, we plan to pursue the following specific aims: 1) Identify the transcription factors that link cAMP signaling to the expression of EF target genes in macrophages; 2) Determine the mechanisms by which EF promotes macrophage motility and survival; and 3) Determine the mechanisms by which EF activates VEGF expression in macrophages and lymphangiogenesis in mice. In addition to providing better insight into the mechanism of anthrax pathogenesis, we aim at devising an efficient method to prevent the spreading of B. anthracis toward fatal systemic infection by modulating the function of EF-targeted host proteins. PUBLIC HEALTH RELEVANCE: We are investigating the mechanisms by which anthrax bacteria manipulate macrophages, major cell participants in the first-strike arm of the immune system, disturbing the signaling system and commandeering the cells as transport, thus allowing the bacteria to spread in the body. Using cultured macrophage cells and mice, we will study exactly how edema factor, one of the toxin proteins produced by anthrax bacteria, activates host genes and thereby directs the spreading of this deadly bacterium. Our hope is that these efforts will lead to the discovery of new targets for the treatment of anthrax and other infectious diseases.