Host-mediated zinc sequestration during Acinetobacter baumannii infection

项目总结 鲍曼不动杆菌是一种重要的医院内病原体，可引起一系列疾病，包括 呼吸道和尿路感染、脑膜炎、心内膜炎、伤口感染和菌血症。事实上, 鲍曼不动杆菌现在占全球某些地区所有重症监护病房感染的20%。 肺炎是世界上最常见的表现。鲍曼不动杆菌感染的临床意义 这种细菌对几乎所有抗生素迅速产生抗药性。身份识别 治疗干预的新靶点对于我们保护公众健康的能力至关重要 新出现的传染性威胁。治疗开发的一个有前景的潜在领域涉及靶向 细菌接触到营养金属或金属处理。这种策略是基于这样一个事实，即所有的细菌 病原体需要营养金属来定植它们的宿主，而饮食中金属水平的变化 对感染的易感性有深远的影响。宿主蛋白钙保护素(CP)是其中最重要的 免疫介导的金属限制和CP的贡献者通过螯合 营养锌(锌)和锰(锰)。在本应用程序中，我们将CP描述为探测 发现鲍曼不动杆菌内与CP依赖条件下的生存有关的遗传位点 缺锌。该基因座编码保守的COG0523 GTP酶家族的一个成员 命名为Zur诱导的GTPase A(ZIGA)，以及我们已命名的D-丙氨酸-D-丙氨酸羧肽酶 锌调节的脂蛋白A(ZrlA)。我们发现ZIGA是一种金属配位酮，它为 客户蛋白，是在缺锌条件下释放生物可利用的锌库所必需的。 这一发现确立了ZIGA是自然界中第一个锌金属配位杂多酮的例子。另外，我们的模型 预测了在锌胁迫过程中，细胞壁构型的维持需要ZrlA。基于这些基本原理 根据我们的发现，我们假设在锌饥饿时，鲍曼不动杆菌会将锌动员到关键的需要锌的客户那里。 蛋白质，同时也激活参与肽聚糖重塑的羧基肽酶的表达 这替代了需要锌的Paralog活性的丧失。为了检验这一中心假设，我们建议 一系列实验旨在了解心力衰竭的机制和病理生理后果。 肺炎发病过程中鲍曼不动杆菌对膳食和宿主缺锌的反应。 在这些研究中，我们将(I)确定ZIGA-锌-金属配位酮在CP条件下的靶标。 施加锌限制，(Ii)阐明在条件下ZrlA在肽聚糖重塑中的作用 以及(Iii)确定锌的分布在A. 鲍曼氏肺炎。这些结果将为鲍曼不动杆菌如何应对 脊椎动物宿主的营养缺乏，并为创造多肽疗法奠定了基础 基于CP支架，通过营养金属螯合抑制微生物生长。

PROJECT SUMMARY Acinetobacter baumannii is an important nosocomial pathogen that causes a range of diseases, including respiratory and urinary tract infections, meningitis, endocarditis, wound infections, and bacteremia. In fact, A. baumannii is now responsible for up to 20% of all intensive care unit infections in some regions of the world with pneumonia being the most common presentation. The clinical significance of A. baumannii has been propelled by this organism's rapid acquisition of resistance to virtually all antibiotics. The identification of novel targets for therapeutic intervention is critical to our ability to protect the public health from this emerging infectious threat. One promising potential area of therapeutic development involves targeting bacterial access to nutrient metal or metal handling. This strategy is based on the fact that all bacterial pathogens require nutrient metal in order to colonize their hosts, and alterations in dietary metal levels profoundly affect susceptibility to infection. The host protein calprotectin (CP) is one of the most important contributors to immune-mediated metal restriction and CP protects against infection through the chelation of nutrient zinc (Zn) and manganese (Mn). In this application, we describe our use of CP as a probe to uncover a genetic locus within A. baumannii that is involved in survival during conditions of CP-dependent Zn starvation. This locus encodes a member of the conserved COG0523 family of GTPases that we have named Zur-induced GTPase A (ZigA), and a D-alanine D-alanine carboxypeptidase that we have named Zn-regulated lipoprotein A (ZrlA). We have discovered that ZigA is a metallochaperone that provides Zn to client proteins and is required for the liberation of a biovavailable Zn pool during conditions of Zn starvation. This finding establishes ZigA as the first example of a Zn metallochaperone in nature. In addition, our model predicts that ZrlA is required to maintain cell wall architecture during Zn stress. Based on these fundamental discoveries, we hypothesize that upon Zn starvation, A. baumannii mobilizes Zn to critical Zn-requiring client proteins, while also activating the expression of a carboxypeptidase involved in peptidoglycan remodeling that substitutes for the loss of activity of a Zn-requiring paralog. To test this central hypothesis, we propose a series of experiments aimed at understanding the mechanism and pathophysiological consequence of the A. baumannii response to dietary and host-imposed Zn deprivation during the pathogenesis of pneumonia. In these studies, we will (i) define the target of the ZigA Zn-metallochaperone during conditions of CP- imposed Zn restriction, (ii) elucidate the contribution of ZrlA to peptidoglycan remodeling during conditions of Zn deprivation, and (iii) determine the importance of Zn distribution during the pathogenesis of A. baumannii pneumonia. These results will provide fundamental insight into how A. baumannii responds to nutrient deprivation in the vertebrate host, and lay the foundation for the creation of peptide therapeutics based on a CP scaffold that inhibit microbial growth through nutrient metal chelation.