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）：铁运载蛋白（脂质运载蛋白 2），存在于中性粒细胞颗粒、子宫分泌物中，并在炎症或肿瘤发生时从上皮细胞分泌。也是一种急性时相蛋白，在细菌感染期间血清和滑膜中的水平显着升高。尽管铁运蛋白与多种生理过程有关，但它的功能一直很神秘，直到我们最近鉴定出这种蛋白质的特异性、高亲和力配体：细菌酚盐型铁铁载体，例如肠螯素（又名肠菌素；KD = 0.4 纳摩尔）和混合型羧基分枝杆菌素铁铁载体。因此，我们认为铁运蛋白具有抗菌剂的功能，将铁作为三价铁铁载体复合物螯合，补充了先天免疫系统的一般抗微生物铁耗竭策略。支持这一假设的是，我们发现铁运蛋白在体外铁限制条件下是一种有效的抑菌剂，并且当被敲除时，使动物非常容易受到细菌感染。铁运蛋白显然使用了一种新颖的简并识别机制来与不同类型的铁载体发生交叉反应，从而扩大了反应的效用。这一功能假说也合理化了一些铁载体与毒力的关联：通过交替利用对铁铁蛋白亲和力显着降低的铁载体，病原体可以逃避铁铁蛋白介导的缺铁。该项目的目标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。 在目标 1 中，我们建议继续对铁蛋白以及一组天然、合成和设计的铁载体进行晶体学、诱变和生物物理研究，以充分描述这种蛋白质如何识别铁载体。铁运载蛋白是多种脂质运载蛋白家族的成员。 我们还鉴定了四种关系较远的鼠类和禽类脂质运载蛋白，它们要么明显结合细菌铁载体的替代谱，要么根据模型研究预测它们会结合。在目标 2 中，我们提出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表征抗菌免疫监视的这一组成部分，还将允许对毒力和发病机制进行持续和未来的研究，并确定这些蛋白质作为新型抗菌疗法的潜在用途。