Synthetic Ligands for Modulating Bacterial Communication

描述（由申请人提供）：群体感应（QS）广泛存在于细菌中，并在细菌与真核宿主的相互作用中发挥关键作用。这种细胞间信号传导机制基于小分子配体及其同源蛋白受体，并允许细菌评估其局部种群密度并作为一个群体发挥作用。拟议研究的长期目标是设计，合成和表征能够拦截原生QS信号的非原生小分子，以作为工具来剖析QS在细菌种群和细菌-宿主关联中的无数作用。这种化学探针的潜在影响是巨大的，范围从基础研究到治疗和生物材料开发。由于许多最臭名昭著的人类病原体使用QS来激活毒力途径，这些毒力途径是急性和慢性感染的起源，包括生物膜形成，因此QS拮抗剂的应用作为一种新型抗微生物策略具有重要的前景。这种“抗毒力”剂与目前的抗生素不同，因为它们靶向感染性而不是生长，并且代表了治疗细菌介导的疾病的范式转变。革兰氏阴性菌中的QS是迄今为止表征最好的，也是本项目的重点。这些QS电路基于N-酰基L-高丝氨酸内酯（阿勒）信号和LuxR型转录因子，并且阿勒与其靶LuxR型受体的结合在高细胞密度下触发QS控制的基因表达。在早期的工作中，我们研究了LuxR型受体配体结合位点的结构，设计了能够靶向这些位点的非天然配体，并开发了这些化合物文库的有效合成路线。在模型细菌菌株中的文库的评价揭示了迄今报道的LuxR型QS的几种最有效的合成拮抗剂和激动剂。这些结果验证了我们的整体研究策略。我们现在的目的是开发新的小分子支架，能够拦截LuxR型QS，提高效力和稳定性，确定这些化合物发挥其QS调节活性的机制，并检查其在野生型人类病原体中减弱QS表型的能力。在赠款期间，这些目标将在三个具体目标中实现。这些是：（1）新合成QS拮抗剂和激动剂的设计和结构优化，（2）合成配体对LuxR型受体拮抗和激动作用的机制分析，以及（3）基于细胞的毒力测定和对QS拮抗剂抗性发展的研究。本文提出的跨学科研究的结果将为QS的机制提供基本见解，并最终为开发下一代细菌感染的抗毒力治疗提供方法。

DESCRIPTION (provided by applicant): Quorum sensing (QS) is widespread in bacteria and plays a pivotal role in their interactions with eukaryotic hosts. This intercellular signaling mechanism is based on small molecule ligands and their cognate protein receptors, and allows bacteria to assess their local population densities and function as a group. The long-term objective of the proposed research is to design, synthesize, and characterize non-native small molecules capable of intercepting native QS signals for use as tools to dissect the myriad roles of QS in bacterial populations and in bacteria-host0 associations. The potential impact of such chemical probes is enormous, and ranges from applications in basic research to therapeutic and biomaterials development. As many of the most notorious human pathogens use QS to activate virulence pathways that are the origin of acute and chronic infections, including biofilm formation, the application of QS antagonists holds significant promise as a novel antimicrobial strategy. Such "anti-virulence" agents differ from current antibiotics because they target infectivity as opposed to growth, and represent a paradigm shift for the treatment of bacteria-mediated disease. QS in Gram-negative bacteria is the best characterized to date and the focus of this project. These QS circuits are based on N-acyl L-homoserine lactone (AHL) signals and LuxR-type transcription factors, and binding of the AHL to its target LuxR-type receptor triggers QS-controlled gene expression at high cell densities. In earlier work, we studied the structures of LuxR-type receptor ligand-binding sites, designed non-native ligands capable of targeting these sites, and developed efficient synthetic routes to libraries of these compounds. Evaluation of the libraries in model bacterial strains revealed several of the most potent synthetic antagonists and agonists of LuxR-type QS reported to date. These results validate our overall research strategy. Our intent now is to develop new small molecules scaffolds capable of intercepting LuxR-type QS with improved potencies and stabilities, determine the mechanisms by which these compounds exert their QS modulatory activities, and examine their ability to attenuate QS phenotypes in wild-type human pathogens. During the grant period, these objectives will be pursued in three Specific Aims. These are: (1) Design and Structural Optimization of New Synthetic QS Antagonists and Agonists, (2) Mechanistic Analysis of LuxR-type Receptor Antagonism and Agonism by Synthetic Ligands, and (3) Cell-Based Virulence Assays and Studies of Resistance Development to QS Antagonists. The results of the interdisciplinary research proposed herein will provide fundamental insights into the mechanisms of QS and ultimately could provide an approach for the development of next-generation, anti-virulence treatments for bacterial infection.