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

描述(申请人提供)：群体感应是细菌细胞间通讯的一种类型，它是通过产生、释放和检测称为自身诱导物(AIs)的小信号分子来实现的。人工智能主要有两种类型，AI-1和AI-2。AI-1包括酰化高丝氨酸内酯和修饰的多肽，它们作为种内信号分子。AI-2是一种呋喃糖基硼酸双酯，是细菌激活的甲基循环中的副产品。AI-2是一种跨物种信号分子，在革兰氏阴性和革兰氏阳性细菌中均有表达。LUXS，S-核糖基同型半胱氨酸酶，是AI-2生物合成的关键酶。依赖于LuxS的群体感应系统调节细菌中一系列不同的生理和病理活动，如毒力因子的表达和生物膜的形成。LuxS蛋白具有很好的保守性，它的同源物已经在55种细菌中被发现，但在人类中没有。由于这些特性，LuxS可以成为开发一类新型抗生素的潜在分子靶点。人类口腔微生物菌斑是由许多遗传上不同类型的细菌组成的生物膜，这些细菌紧密地并列在宿主表面。作为生物膜的生长对于口腔细菌适应并在口腔菌群中茁壮成长并导致口腔感染是必不可少的。大量研究表明，LUXS依赖的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发挥着非常重要的作用。因此，LuxS有可能成为开发预防或治疗牙周病的治疗药物的潜在靶点。这项应用的目标是开发基于LuxS的治疗化合物，专门抑制PG等致病口腔细菌的生物膜形成。为了实现这一目标，目前的应用主要集中在以下几个方面：(1)阐明Sg和PG的LuxS蛋白的生化和结构特征；(2)设计和筛选体外抑制PG LuxS活性的特定化合物；(3)筛选特异性抑制PG生物膜形成而不是Sg生物膜形成的化合物。这些研究的完成不仅将有助于更好地了解口腔细菌LuxS蛋白的生化和结构特征，而且还可能为牙周病的预防和治疗提供新的手段。 公共卫生相关性：牙周感染是由一组口腔细菌引起的，这些细菌在口腔菌群中以生物膜(菌斑)的形式生长。作为生物膜的生长对于口腔细菌适应并在口腔菌群中茁壮成长并导致感染是必不可少的。这项应用的目标是开发能够抑制口腔细菌生物膜形成的抑制剂。

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.