Therapeutic Interventions Targeted on Anthrax Toxins

免责声明 炭疽毒素是吸入炭疽杆菌孢子导致死亡的主要原因。是 由保护性抗原（PA）、致死因子（LF）和水肿因子（EF）三种蛋白质组成。 为了表达毒性，PA结合细胞表面受体，肿瘤内皮标志物8（TEMS）或 毛细血管形态发生基因2（CMG 2）。在蛋白水解加工后，寡聚PA 与LF或EF结合并将毒素转运至内体和胞质溶胶。在细胞质中， EF表达其腺苷酸环化酶活性，LF是一种金属蛋白酶， 丝裂原活化蛋白激酶（MAPK）激酶家族。因此，干扰毒素 在上述途径中发挥作用是一种重要的治疗方法。在这里，我们提出了一个双管齐下的研究。第一种是在感染的早期阶段，在机会窗口期间清除血浆中的LF。作为一种金属蛋白酶，LF具有狭窄的底物特异性，并且不会被血液中大量存在的α 2-巨球蛋白（α 2 M）灭活。我们建议工程改造α 2 M的诱饵区域以获得LF失活的新活性。新的alpha 2 M可以输注到孢子吸入患者中，以保持他们在接受抗生素治疗时的生命。第二种方法是干扰PA与其细胞表面炭疽毒素受体的结合。我们建议确定PA-TEM 8和PA-MG 2复合物的三维结构，并使用结构信息来设计干扰复合物形成的小分子抑制剂。在研究计划中设置了各种里程碑，并计划在该计划结束时将最终产品用于人体临床实验。

SU MMARY STATEMENT Anthrax toxin is the major cause of death in inhalation of Bacillus anthracis spores. It is composed of three proteins: protective antigen (PA), lethal factor (LF) and edema factor (EF). To express toxicity, PA binds to a cell surface receptor, tumor endothelial marker 8 (TEMS) or capillary morphogenesis gene-2 (CMG2). After proteolytic processing, the oligomerized PA binds to either LF or EF and transports the toxins to endosomes and cytosol. Within the cytosol, EF expresses its adenylyl cyclase activity and LF, a metalloprotease, hydrolyzes members of the mitogen-activated protein kinase (MAPK) kinase family. Therefore, interfering with the toxin functions in the above pathway is an important therapeutic approach. Here we propose a two-prong research. The first is to inactivate and remove LF in the blood plasma during the window of opportunity at an early stage of infection. As a metalloprotease, LF has a narrow substrate specificity and is not inactivated by alpha2-macroglobulin (alpha2M) that are present in the blood at high amounts. We propose to engineer the bait region of alpha2M to gain a new activity for LF inactivation. The new alpha2M may be infused into spore inhalation patients to keep them alive while being treated with antibiotics. The second approach is to interfere with the binding of PA to its cell surface anthrax toxin receptors. We propose to determine the three-dimensional structures of PA-TEM8 and PA-MG2 complexes and use the structural information to design small-molecular inhibitors that interfere with the complex formation. Various milestones are installed in the Research Plan and the final products are planned for human clinical experiments at the end of this program.