ABSTRACT

Drug-resistant pathogenic Staphylococcus aureus (S. aureus) has severely threatened human health and arouses widespread concern. Sortase A (SrtA) is an essential virulence factor of S. aureus, which is responsible for the covalent anchoring of a variety of virulence-related proteins to the cell wall. SrtA has always been regarded as an ideal pharmacological target against S. aureus infections. In this research, we have determined that orientin, a natural compound isolated from various medicinal plants, can effectively inhibit the activity of SrtA with an IC₅₀ of 50.44 ± 0.51 µM. We further demonstrated that orientin inhibited the binding of S. aureus to fibrinogen and diminished biofilm formation and the attaching of Staphylococcal protein A (SpA) to the cell wall in vitro. Using the fluorescence quenching assay, we demonstrated a direct interaction between orientin and SrtA. Further mechanistic studies revealed that the residues Glu-105, Thr-93, and Cys-184 were the key sites for the binding of SrtA to orientin. Importantly, we demonstrated that treatment with orientin attenuated S. aureus virulence of in vivo and protected mice against S. aureus-induced lethal pneumonia. These findings indicate that orientin is a potential drug to counter S. aureus infections and limit the development of drug resistance.

摘要

耐药性致病性金黄色葡萄球菌（S. aureus）严重威胁人类健康，引起广泛关注。Sortase A (SrtA) 是金黄色葡萄球菌的重要毒力因子，负责将多种毒力相关蛋白共价锚定到细胞壁上。SrtA 一直被认为是抗金黄色葡萄球菌感染的理想药理学靶点。在这项研究中，我们已经确定，从各种药用植物中分离出来的天然化合物荠菜素可以有效抑制 SrtA 的活性，IC ₅₀为 50.44 ± 0.51 µM。我们进一步证明了荠菜素抑制金黄色葡萄球菌的结合纤维蛋白原和减少的生物膜形成和葡萄球菌蛋白 A (SpA)在体外与细胞壁的附着。使用荧光猝灭测定，我们证明了荭草素和 SrtA 之间的直接相互作用。进一步的机理研究表明，残基 Glu-105、Thr-93 和 Cys-184 是 SrtA 与 orientin 结合的关键位点。重要的是，我们证明用荭草素治疗可减弱体内金黄色葡萄球菌的毒力，并保护小鼠免受金黄色葡萄球菌诱导的致死性肺炎。这些发现表明，荠菜素是一种对抗金黄色葡萄球菌感染和限制耐药性发展的潜在药物。