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（由申请人提供）：在中性粒细胞颗粒，子宫分泌物中发现的Siderocalin（Lipocalin 2），并从上皮细胞中分泌，以应对炎症或肿瘤发生。也是一种急性相蛋白，在细菌感染过程中血清和滑膜水平明显升高。尽管与多样化的生理过程有关，但直到我们最近对这种蛋白质的特异性高亲和力配体鉴定之前，Siderocalin的功能是神秘的：细菌型苯甲酸苯甲酸苯甲酸铁型铁载体，例如肠球磷脂（AKA肠乳糖蛋白（aka interobactin; kd = 0.4纳米尔）和混合 - 型碳纤维蛋白。因此，我们提出副旋转蛋白充当抗菌剂，将铁作为铁载体复合物隔离，并补充先天免疫系统的一般抗微生物铁灭绝策略。在支持这一假设的情况下，我们发现在铁限制条件下，副旋藻是一种体外有效的抑菌剂，并且在敲除时，使动物显着容易受到细菌感染的影响。 Siderocalin显然使用一种新型的退化识别机制与不同类型的铁载体进行交叉反应，从而扩大了反应的效用。该功能性假设还合理化了一些铁载体与毒力的关联：通过交替利用对副链蛋白的亲和力显着降低的铁载体，病原体可以逃脱sideocalin介导的铁剥落。该项目的目的是确定先天免疫反应的铁载体特异性成分如何识别微生物铁载体。 在AIM 1中，我们提出了对辅助蛋白的持续晶体学，诱变和生物物理研究，以及一组天然，合成和设计的铁载体，以完全描述该蛋白质如何识别铁载体。 Siderocalin是多种脂肪蛋白蛋白家族的成员。 我们还确定了四个遥远相关的鼠和禽脂蛋白，它们可以明显地结合细菌铁载体的替代光谱，或者根据建模研究进行预测。在AIM 2中，我们提出了这些蛋白质的类似结构和生化研究，以类似地解析其识别机制。 最终，这些研究不仅将充分表征抗菌免疫监测的这一组成部分，而且还将允许对毒力和发病机理的持续和未来的研究 - 并将这些蛋白质的潜在效用定义为新型抗细菌疗法。