Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, United States of America.
Institute of Life Sciences, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
PLoS Pathog. 2019 May 22;15(5):e1007800. doi: 10.1371/journal.ppat.1007800. eCollection 2019 May.
Staphylococcus aureus is a leading cause of endovascular infections. This bacterial pathogen uses a diverse array of surface adhesins to clump in blood and adhere to vessel walls, leading to endothelial damage, development of intravascular vegetations and secondary infectious foci, and overall disease progression. In this work, we describe a novel strategy used by S. aureus to control adhesion and clumping through activity of the ArlRS two-component regulatory system, and its downstream effector MgrA. Utilizing a combination of in vitro cellular assays, and single-cell atomic force microscopy, we demonstrated that inactivation of this ArlRS-MgrA cascade inhibits S. aureus adhesion to a vast array of relevant host molecules (fibrinogen, fibronectin, von Willebrand factor, collagen), its clumping with fibrinogen, and its attachment to human endothelial cells and vascular structures. This impact on S. aureus adhesion was apparent in low shear environments, and in physiological levels of shear stress, as well as in vivo in mouse models. These effects were likely mediated by the de-repression of giant surface proteins Ebh, SraP, and SasG, caused by inactivation of the ArlRS-MgrA cascade. In our in vitro assays, these giant proteins collectively shielded the function of other surface adhesins and impaired their binding to cognate ligands. Finally, we demonstrated that the ArlRS-MgrA regulatory cascade is a druggable target through the identification of a small-molecule inhibitor of ArlRS signaling. Our findings suggest a novel approach for the pharmacological treatment and prevention of S. aureus endovascular infections through targeting the ArlRS-MgrA regulatory system.
金黄色葡萄球菌是导致血管内感染的主要原因。这种细菌病原体使用多种表面黏附素聚集在血液中并黏附在血管壁上，导致内皮损伤、血管内赘生物和继发性感染灶的形成，以及整体疾病的进展。在这项工作中，我们描述了金黄色葡萄球菌通过 ArlRS 双组分调节系统及其下游效应物 MgrA 来控制黏附和聚集的新策略。我们利用体外细胞分析和单细胞原子力显微镜技术，证明了该 ArlRS-MgrA 级联的失活抑制了金黄色葡萄球菌对多种相关宿主分子（纤维蛋白原、纤维连接蛋白、血管性血友病因子、胶原蛋白）的黏附、与纤维蛋白原的聚集以及对人内皮细胞和血管结构的附着。这种对金黄色葡萄球菌黏附的影响在低剪切环境中以及生理水平的剪切应力中以及在小鼠模型中均很明显。这些影响可能是由于 ArlRS-MgrA 级联失活导致的巨型表面蛋白 Ebh、SraP 和 SasG 的去抑制引起的。在我们的体外实验中，这些巨型蛋白共同屏蔽了其他表面黏附素的功能，并削弱了它们与相应配体的结合。最后，我们通过鉴定 ArlRS 信号的小分子抑制剂，证明了 ArlRS-MgrA 调节级联是一个可成药的靶点。我们的研究结果表明，通过靶向 ArlRS-MgrA 调节系统，为金黄色葡萄球菌血管内感染的治疗和预防提供了一种新的方法。
