Microbial siderophore-specific innate immune responses

微生物铁载体特异性先天免疫反应

• 批准号: 6872755
• 负责人: Roland K Strong
• 金额: $ 29.41万
• 依托单位: FRED HUTCHINSON CANCER RESEARCH CENTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6872755
• 关键词: X ray crystallography; antibacterial agents; antiinfective agents; bactericidal immunity; chemical synthesis; immune response; iron; microorganism immunology; polymerase chain reaction; protein structure; siderophores; virulence

DESCRIPTION (provided by applicant): Siderocalin (lipocalin 2), found in neutrophil granules, uterine secretions and secreted from epithelial cells in response to inflammation or tumorigenesis. is also an acute phase protein, with markedly elevated levels in the serum and the synovium during bacterial infection. Though implicated in diverse physiological processes, siderocalin's function was mysterious until our recent identification of specific, high-affinity ligands for this protein: bacterial phenolate-type ferric siderophores, such as enterochelin (aka enterobactin; KD = 0.4 nanomolar) and the mixed-type carboxymycobactin ferric siderophores. We therefore propose that siderocalin functions as an antibacterial agent, sequestering iron as ferric siderophore complexes, complementing the general anti-microbial iron-depletion strategy of the innate immune system. Supporting this hypothesis, we have found that siderocalin is a potent bacteriostatic agent in vitro under iron-limiting conditions and, when knocked-out, renders animals remarkably susceptible to bacterial infection. Siderocalin apparently uses a novel, degenerate recognition mechanism to cross-react with distinct types of siderophores, broadening the utility of the response. This functional hypothesis also rationalizes the association of some siderophores with virulence: by alternately utilizing siderophores with markedly reduced affinity for siderocalin, pathogens can escape siderocalin-mediated iron-deprivation. The goal of this project is to determine how siderophore-specific components of the innate immune response recognize microbial siderophores. In Aim 1, we propose continuing crystallographic, mutagenesis and biophysical studies of siderocalin, and a panel of natural, synthetic and designed siderophores, to fully delineate how this protein recognizes siderophores. Siderocalin is a member of the diverse lipocalin protein family. We have also identified four distantly-related murine and avian lipocalins that either demonstrably bind alternate spectrums of bacterial siderophores or are predicted to on the basis of modeling studies. In Aim 2, we propose analogous structural and biochemical studies of these proteins to similarly parse their recognition machinery. Ultimately, these studies will not only fully characterize this component of antibacterial immune surveillance, but will also allow continuing and future studies of virulence and pathogenesis - as well as defining the potential utility of these proteins as novel anti-bacterial therapeutics.

描述(申请人提供)：西德罗卡林(Lipocalin 2)，发现于中性粒细胞颗粒和子宫分泌物中，由上皮细胞分泌，对炎症或肿瘤发生作出反应。也是一种急性期蛋白，在细菌感染期间血清和滑膜中的水平显著升高。虽然与多种生理过程有关，但铁黄素的功能一直是个谜，直到我们最近发现了该蛋白的特定的高亲和力配体：细菌酚型铁铁载体，如肠球蛋白(又名肠球蛋白；Kd=0.4纳米分子)和混合型羧基粘连蛋白铁铁载体。因此，我们认为铁胆碱作为一种抗菌剂发挥作用，将铁作为铁载体复合体隔离，补充了先天免疫系统一般的抗微生物铁耗竭策略。支持这一假说的是，我们发现在体外铁限制条件下，铁胆碱是一种有效的抑菌剂，当被敲除时，使动物非常容易受到细菌感染。西德罗卡林显然使用了一种新的、退化的识别机制来与不同类型的铁载体发生交叉反应，从而扩大了反应的用途。这一功能假说也使一些铁载体与毒力之间的联系合理化：通过交替利用铁载体，而铁载体对铁载体的亲和力显著降低，病原体可以逃脱铁载体介导的铁缺乏。该项目的目标是确定先天免疫反应中铁载体特异性成分如何识别微生物铁载体。在目标1中，我们建议继续进行铁黄素的结晶学、诱变和生物物理研究，以及一组天然的、合成的和设计的铁载体，以充分描述该蛋白质如何识别铁载体。西德罗卡林是Lipocalin蛋白家族的一员。我们还确定了四个远缘关系的小鼠和禽类Lipocalin，它们要么明显地结合细菌铁载体的交替光谱，要么根据模拟研究预测会结合。在目标2中，我们建议对这些蛋白质进行类似的结构和生化研究，以类似地解析它们的识别机制。最终，这些研究不仅将充分描述抗菌免疫监测的这一组成部分，而且还将允许继续和未来对毒力和发病机制的研究-以及确定这些蛋白质作为新型抗菌疗法的潜在用途。