MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural Universitygrid.27871.3b, Nanjing, China.
Key Lab of Animal Bacteriology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural Universitygrid.27871.3b, Nanjing, China.
Microbiol Spectr. 2022 Apr 27;10(2):e0166221. doi: 10.1128/spectrum.01662-21. Epub 2022 Mar 7.
Extraintestinal pathogenic Escherichia coli (ExPEC) can cause systemic infections in both humans and animals. As an essential nutrient, iron is strictly sequestered by the host. Circumventing iron sequestration is a determinant factor for ExPEC infection. However, the ExPEC iron acquisition mechanism, particularly the mechanism of transferrin (TF) acquisition, remains unclear. This study reports that iron-saturated holo-TF can be utilized by ExPEC to promote its growth in culture medium and survival in macrophages. ExPEC specifically bound to holo-TF instead of iron-free apo-TF via the surface located elongation factor G (EFG) in both culture medium and macrophages. As a moonlighting protein, EFG specifically bound holo-TF and also released iron in TF. These two functions were performed by different domains of EFG, in which the N-terminal domains were responsible for holo-TF binding and the C-terminal domains were responsible for iron release. The functions of EFG and its domains have also been further confirmed by surface-display vectors. The surface overexpression of EFG bound significantly more holo-TF in macrophages and significantly improved bacterial intracellular survival ability. Our findings reveal a novel iron acquisition mechanism involving EFG, which suggests novel research avenues into the molecular mechanism of ExPEC resistance to nutritional immunity. Extraintestinal pathogenic Escherichia coli (ExPEC) is an important pathogen causing systemic infections in humans and animals. The competition for iron between ExPEC and the host is a determinant for ExPEC to establish a successful infection. Here, we sought to elucidate the role of transferrin (TF) in the interaction between ExPEC and the host. Our results revealed that holo-TF could be utilized by ExPEC to enhance its growth in culture medium and survival in macrophages. Furthermore, the role of elongation factor G (EFG), a novel holo-TF-binding and TF-iron release protein, was confirmed in this study. Our work provides insights into the iron acquisition mechanism of ExPEC, deepens understanding of the interaction between holo-TF and pathogens, and broadens further researches into the molecular mechanism of ExPEC pathogenicity.
肠外致病性大肠杆菌（ExPEC）可引起人类和动物的全身感染。铁是一种必需营养物质，宿主对其严格隔离。绕过铁隔离是 ExPEC 感染的决定因素。然而，ExPEC 的铁获取机制，特别是转铁蛋白（TF）获取机制尚不清楚。本研究报告称，铁饱和的全铁转铁蛋白可被 ExPEC 利用，以促进其在培养基中的生长和在巨噬细胞中的存活。ExPEC 通过培养基和巨噬细胞中位于表面的延伸因子 G（EFG）特异性结合全铁转铁蛋白，而不是无铁脱铁转铁蛋白。作为一种兼职蛋白，EFG 特异性结合全铁转铁蛋白，并在转铁蛋白中释放铁。这两个功能由 EFG 的不同结构域执行，其中 N 端结构域负责全铁转铁蛋白结合，C 端结构域负责铁释放。EFG 及其结构域的功能也通过表面展示载体得到了进一步证实。EFG 的表面过表达在巨噬细胞中显著结合更多的全铁转铁蛋白，并显著提高了细菌的细胞内存活能力。我们的研究结果揭示了一种涉及 EFG 的新型铁获取机制，这为 ExPEC 抵抗营养免疫的分子机制提供了新的研究途径。
肠外致病性大肠杆菌（ExPEC）是一种重要的病原体，可引起人类和动物的全身感染。ExPEC 与宿主争夺铁是 ExPEC 建立成功感染的决定因素。在这里，我们试图阐明转铁蛋白（TF）在 ExPEC 与宿主相互作用中的作用。我们的结果表明，全铁转铁蛋白可被 ExPEC 利用来增强其在培养基中的生长和在巨噬细胞中的存活。此外，在这项研究中还证实了伸长因子 G（EFG）的作用，EFG 是一种新型的全铁转铁蛋白结合蛋白和 TF-铁释放蛋白。我们的工作深入了解了 ExPEC 的铁获取机制，加深了对全铁转铁蛋白与病原体相互作用的认识，并进一步拓展了对 ExPEC 致病性分子机制的研究。
