CHARACTERIZATION OF ANTHRAX TOXIN RECEPTOR INTERACTIONS

性状（由申请方提供）：炭疽芽孢杆菌（炭疽的病原体）的毒力与其分泌毒素的活性有关。炭疽毒素是由一个单一的细胞结合部分，保护性抗原（PA），和两个催化部分，致死因子（LF）和水肿因子（EF）。LF是一种蛋白酶，其切割信号蛋白的MAP激酶激酶家族的成员，并引起巨噬细胞裂解。EF是一种腺苷酸环化酶，其增加细胞cAMP水平，破坏水稳态和中性粒细胞功能。PA结合宿主细胞炭疽毒素受体（ATR），随后结合LF和EF并将其转运到宿主细胞质中，在那里它们是有活性的。因此，炭疽毒素对哺乳动物细胞发挥其毒性作用的能力取决于PA结合ATR的能力。关于ATR的天然功能知之甚少，并且没有报道该受体的天然配体。然而，PA通过结构保守的整合素样插入（I）结构域结合ATR。I结构域作为蛋白质-蛋白质相互作用模块起作用，因此通常与ATR相互作用的宿主蛋白质可能通过PA结合的相同结构域来进行。鉴定ATR能够参与的非毒素相互作用并定义毒素和天然配体的结合要求将为开发阻断毒素-受体相互作用同时保持正常ATR相互作用完整的抗毒素提供有价值的信息。因此，这些拟议研究的主要目标是阐明与ATR结合的分子要求。将鉴定ATR配体，并表征ATR-PA和ATR-配体相互作用。毒素和配体相互作用之间的比较分析将用于确定结合的要求是否重叠或不同。另外，将筛选噬菌体展示文库中特异性结合ATR的肽。从这些研究中获得的信息将用于开发基于可溶性受体、毒素或配体模拟物或特异性阻断PA-ATR相互作用的小肽的不同类别的抗毒素。

DESCRIPTION (provided by applicant): Virulence of Bacillus anthracis, the causative agent of anthrax, is associated with the activities of its secreted toxin. Anthrax toxin is comprised of a single cell-binding moiety, protective antigen (PA), and two catalytic moieties, lethal factor (LF) and edema factor (EF). LF is a protease that cleaves members of the MAP kinase kinase family of signaling proteins, and causes lysis of macrophages. EF is an adenylate cyclase that increases cellular levels of cAMP, disrupting water homeostasis and neutrophil function. PA binds the host cellular anthrax toxin receptor (ATR) and subsequently binds and translocates LF and EF into the host cytosol where they are active. Thus, the ability of anthrax toxin to exert its toxic effects on mammalian cells depends on the ability of PA to bind ATR. Very little is known about the natural function of ATR, and no natural ligands for this receptor have been reported. However, PA binds ATR through a structurally conserved integrin-like inserted (I) domain. I domains function as protein-protein interaction modules, and thus it is likely that host proteins that normally interact with ATR do so via the same domain to which PA binds. Identifying the non-toxin interactions that ATR is capable of engaging in and defining the binding requirements for both toxin and natural ligands will provide valuable information for the development of antitoxins that block toxin-receptor interaction while leaving normal ATR interactions intact. Therefore, the primary goal of these proposed studies is to elucidate the molecular requirements for binding to ATR. ATR ligands will be identified and ATR-PA and ATR-ligand interactions will be characterized. Comparative analysis between toxin and ligand interactions will be used to determine if the requirements for binding overlap or are distinct. Additionally phage display libraries will be screened for peptides that bind specifically to ATR. The information learned from these studies wilt be used to develop distinct classes of antitoxins based on soluble receptor, toxin or ligand mimetics, or small peptides that specifically block PA-ATR interactions.