Exploiting quorum sensing inhibition of the natural products fimbrolide and elegaphenone in gram-negative bacteria

由多重耐药菌株引起的细菌感染对公共卫生构成重大威胁。尤其是表现出几乎不可克服的细胞膜的革兰氏阴性菌株对于治疗具有挑战性。因此，研究基本的细胞机制是一项重要的任务，以确定新的治疗方法。在这里，细菌之间的细胞通讯，称为群体感应（QS），在发病机制的调节中起着关键作用。在我们以前的工作中，我们研究了发光模式生物哈维氏弧菌中的fimbrolide天然产物，并确定了QS途径的中央调节器LuxS作为其细胞靶点。在本项目的第一部分，我们希望扩大范围，并专注于在致病性革兰氏阴性S菌中使用第二代抑制剂抑制LuxS。鼠伤寒。对于该策略，我们采用S.本研究旨在探讨其抑制鼠伤寒沙门氏菌和哈维氏菌LuxS的作用机制，并合理设计改良的结合剂。基于这些结果，将合成不同的芬布洛来类似物，并在已建立的LuxS测定中进行检测。此外，在整个S中对LuxS最有效的化合物的选择性。通过制备相应的探针和随后的化学蛋白质组学研究来分析鼠伤寒杆菌细胞。有了一个有效的和特异性的LuxS抑制剂在手，我们将不仅测试它对S。鼠伤寒的发病机制，但也阐明了一个机制之谜。虽然AI-2是S.鼠伤寒沙门氏菌，其相应的调节致病因子至今仍是难以捉摸的。因此，我们的目的是研究AI-2在S.新一代LuxS抑制剂通过全蛋白质组分析研究鼠伤寒杆菌的发病机制。该项目的第二部分致力于从金丝桃中分离出的天然产物elegaphenone。该化合物因其对革兰氏阳性细菌菌株的抗菌活性而闻名。然而，在初步实验中，我们令人惊讶地发现，它抑制了铜绿假单胞菌（一种具有高度临床相关性的毁灭性病原体）中的QS依赖性毒力。由于这种生物活性指向一个有前途的治疗靶点，我们在这里建议合成相应的探针，解开其细胞机制，并进一步剖析其在QS中的潜在作用。综上所述，本项目旨在以天然产物QS抑制剂为出发点，针对革兰氏阴性菌进行合成优化，深入机理研究，开发具有抗菌活性的新型QS抑制剂，重点关注具有挑战性的革兰氏阴性菌。

Bacterial infections caused by multiresistant strains pose a major threat to public health. Especially gram-negative strains exhibiting an almost insuperable cell membrane are challenging for treatment. Thus, the study of essential cellular mechanisms is an important task in order to identify novel therapeutic approaches. Here, the cellular communication between bacteria, termed quorum sensing (QS), plays a key role in the regulation of pathogenesis. In our previous work, we investigated fimbrolide natural products in the luminescent model organism Vibrio harveyi and identified LuxS, a central regulator of the QS pathway, as their cellular target. In the first part of this project, we would like to expand the scope and focus on inhibition of LuxS with second generation inhibitors in pathogenic gram-negative S. typhimurium. For this strategy, we employ cocrystallization of S. typhimurium and V. harveyi LuxS with fimbrolide to elucidate its inhibition mechanism and rationally design improved binders. Based on these results, diverse fimbrolide analogs will be synthesized and tested in an established LuxS assay. Furthermore, selectivity of the most potent compound for LuxS in whole S. typhimurium cells will be analyzed via preparation of a corresponding probe and subsequent chemical proteomics studies. With a potent and specific LuxS inhibitor at hand, we will not only test its effect on S. typhimurium pathogenesis but also elucidate a mechanistic puzzle. Although AI-2 is the sole comprehensive QS circuit in S. typhimurium, its corresponding regulation of pathogenicity factors remains elusive so far. Therefore, we aim to investigate the role of AI-2 in S. typhimurium pathogenesis via whole proteome analysis with the new generation of LuxS inhibitors. The second part of the project is dedicated to the natural product elegaphenone isolated of Hypericum elegans. The compound is well-known for its antibacterial activity against gram-positive bacterial strains. However, in pilot experiments we surprisingly identified that it inhibits QS-dependent virulence in Pseudomonas aeruginosa, a devastating pathogen of high clinical relevance. As this bioactivity points towards a promising therapeutic target, we here propose to synthesize a corresponding probe, unravel its cellular mechanism and further dissect its potential role in QS. Moreover, based on SAR studies, new QS inhibitors will be synthesized and tested for their antibacterial activity in gram-negative bacteria.In summary, this project aims to utilize natural product QS inhibitors as a starting point for synthetic optimization, in depth mechanistic studies and development of novel inhibitors with antibacterial potency deliberately focusing on challenging gram-negative strains.