Developing Inhibitors of LuxS-dependent Quorum Sensing Systems in Oral Bacteria

描述（由申请人提供）：群体感应是一种细菌细胞间的通信，它是通过产生、释放和检测被称为自诱导剂（AIs）的小信号分子来实现的。有两种主要类型的人工智能，AI-1和AI-2。AI-1包括酰基化的同丝氨酸内酯和修饰肽，作为种内信号分子。AI-2是一种呋喃基硼酸二酯，是细菌活化甲基循环的副产物。AI-2是种间信号分子，为革兰氏阴性菌和革兰氏阳性菌共有。LuxS， s -核糖体同型半胱氨酸酶，是AI-2生物合成的关键酶。依赖luxs的群体感应系统调节细菌的多种生理和病理活动，如毒力因子表达和生物膜形成。LuxS蛋白具有较好的保守性，其同源物已在55种细菌中发现，但在人类中不存在。由于这些特点，LuxS可以成为开发一类新型抗生素的潜在分子靶点。人类口腔微生物斑块是由许多遗传上不同类型的细菌组成的生物膜，它们生活在宿主表面。作为生物膜的生长是口腔细菌适应和在口腔菌群中茁壮成长并引起口腔感染的必要条件。大量研究表明，依赖LuxS的QS系统在许多口腔细菌的生物膜形成和毒力因子的产生方面起着非常重要的作用。因此，LuxS可以成为开发治疗药物以预防或治疗牙周病的潜在目标。本申请的目标是开发基于LuxS的治疗性化合物，以特异性抑制口腔致病性细菌如Pg的生物膜形成。为了实现这一目标，目前的申请主要集中在以下几个具体目标上：(1)阐明Sg和Pg的LuxS蛋白的生化和结构特征；(2)设计筛选体外抑制Pg LuxS活性的特异性化合物；(3)筛选特异性抑制Pg生物膜形成而不抑制Sg生物膜形成的化合物。这些研究的完成不仅有助于更好地了解口腔细菌LuxS蛋白的生化和结构特征，而且可以为牙周病的预防和治疗提供新的手段。

DESCRIPTION (provided by applicant): Quorum sensing is a type of bacterial cell-to-cell communication, and it is achieved through the production, release and detection of small signaling molecules called autoinducers (AIs). There are two major types of AIs, AI-1 and AI-2. AI-1 includes acylated homoserine lactones and modified peptides, which serve as intra-species signaling molecules. AI-2 is a furanosyl borate diester, a byproduct in the activated methyl cycle of bacteria. AI-2 is an interspecies signaling molecule, which is shared by both gram-negative and gram-positive bacteria. LuxS, S-Ribosylhomocysteinase, is a key enzyme in the biosynthesis of AI-2. The LuxS-dependent quorum sensing systems regulate a diverse array of physiological and pathological activities in bacteria, such as virulence factor expression and biofilm formation. LuxS proteins are well conserved, and its orthologs have been found in over 55 bacterial species, but absent in human. Due to these features, LuxS can be a potential molecular target for developing a novel class of antibiotic agents. Human oral microbial-plaques are biofilms composed of numerous genetically distinct types of bacteria that live in close juxtaposition on host surfaces. Growth as biofilms is essential for oral bacteria to adapt and thrive in oral flora and cause oral infections. Numerous studies have shown that the LuxS- dependent QS systems play very important roles in many oral bacteria in terms of biofilm formation, and production of virulence factors. Thus, LuxS can be a potential target for developing therapeutic agents to prevent or treat periodontal diseases. The goal of this application is to develop LuxS-based therapeutic compounds that specifically inhibit the biofilm formation of pathogenic oral bacteria such as Pg. To achieve this goal, the current application focuses on the following specific aims: (1) To elucidate the biochemical and structural features of LuxS proteins of Sg and Pg; (2) To design and screen specific compounds that inhibit the activity of Pg LuxS in vitro; and (3) To screen the compounds that specifically inhibit the biofilm formation of Pg but not Sg. The accomplishment of these studies will not only lead to a better understanding the biochemical and structural features of LuxS proteins from oral bacteria, but could also provide new means of prevention and treatment of periodontal diseases. PUBLIC HEALTH RELEVANCE: Periodontal infections are caused by a group of oral bacteria that grow as biofilms (plaque) in oral flora. Growth as biofilms is essential for oral bacteria to adapt and thrive in oral flora and cause the infections. The goal of this application is to develop inhibitors that are able to inhibit the biofilm formation of oral bacteria.