Microbial Recognition of Sialic Acid Diversity in the Salivary Proteome

描述（由申请人提供）：在对口腔健康的许多其他贡献中，唾液通过促进无害的口腔细菌的定植来帮助维持多种口腔生物膜微生物群内的生态平衡。由于口腔是病原微生物进入胃肠道和呼吸道的入口，因此有理由将与口腔细菌相互作用的唾液组分与推定的口外病原体结合的唾液组分分开。初步数据表明，存在额外的尚未充分理解的复杂性，在唾液糖蛋白的结构介绍或唾液酸的取代，可能会影响粘附素介导的细菌结合，口腔链球菌和口外病原体。考虑到自然界中存在超过40种不同的唾液酸结构亚型，并且已知其介导多种生理和病理过程，包括被病毒和其他病原体识别，因此迄今为止几乎没有工作来确定哪些结构唾液酸亚型存在于人唾液中的糖蛋白上，并且与唾液酸结合病原体如H. pylori或S.肺炎。我们推测O-乙酰基取代唾液酸影响链球菌结合。这些结果有望进一步阐明某些草绿色链球菌令人惊讶的狭窄组织和宿主嗜性，其中一些仅在人类口腔内茁壮成长。鉴定细菌与唾液酸结合的结构要求不仅与唾液和口腔疾病（如龋齿和牙周炎）的易感性有关，而且还可以很容易地应用于病原微生物与呼吸道、消化道和生殖道中其他身体分泌物和粘液覆盖的上皮细胞的相互作用。此外，一旦确定了某些微生物粘附素的确切唾液酸识别基序，就有可能设计碳水化合物类似物作为药物，以防止不需要的细菌定植。该项目的具体目标是：1.定义9-O-乙酰化唾液酸在2-D唾液糖蛋白组成员中的分布。 2.确定被相应粘附素识别的唾液酸的结构亚型，并证明唾液酸的9-O-乙酰化决定链球菌与唾液糖蛋白的结合。这些目标将通过糖生物学和蛋白质组学方法的组合来实现。 公共卫生相关性：拟议的研究旨在通过调查唾液在促进有益肠道微生物菌群口腔定植与预防病原微生物感染方面的区别作用，增加口腔作为进入胃肠道和呼吸道的主要途径的重要性。这项研究与人类健康有关，因为这些发现有望最终帮助了解细菌对口腔和其他粘液组织的组织嗜性。破译这种向性的分子机制有望为未来药物预防不需要的细菌定植铺平道路。

DESCRIPTION (provided by applicant): Among many other contributions to oral health, saliva helps to maintain an ecological balance within the diverse oral biofilm microbiota through fostering colonization by harmless commensal bacteria. Because the oral cavity serves as a port of entry for pathogenic microorganisms to both gastrointestinal and respiratory tracts, legitimate interest exists to dissect salivary components that interact with commensal bacteria from those that are bound by putative extraoral pathogens. Preliminary data suggest that there exists additional not yet well understood complexity in the structural presentation or substitution of sialic acids on salivary glycoproteins that are likely to influence adhesin-mediated bacterial binding by both, commensal oral streptococci and extraoral pathogens. Considering that more than 40 different structural subtypes of sialic acids exist in nature and are known to mediate a wide variety of physiological and pathological processes, including recognition by viruses and other pathogens, thus far little work has been done to determine which structural sialic acid subtypes are present on glycoproteins in human saliva, and which are specifically recognized by oral commensal streptococci in comparison to sialic acid binding pathogens such as H. pylori or S. pneumoniae. We hypothesize that sialic acid substitution by O-acetyl groups influences streptococcal binding. The results are expected to shed additional light on the surprisingly narrow tissue and host tropism of certain viridans streptococci, of which some thrive exclusively within the human oral cavity. Identification of the structural requirements for bacterial binding to sialic acids will be relevant not only to saliva and susceptibility to oral diseases, such as caries and periodontitis, but may also be readily applied to the interaction of pathogenic microorganisms with other bodily secretions and mucous-covered epithelia in respiratory, digestive and genital tracts. Moreover, once the exact sialic acid recognition motifs for certain microbial adhesins are determined, it will become possible to design carbohydrate analogues as drugs to prevent colonization by undesired bacteria. The specific aims of the project are to: 1. Define how 9-O-acetylated sialic acids are distributed among members of the 2-D salivary glycoproteome. 2. Determine the structural subtypes of sialic acids recognized by the corresponding adhesins and demonstrate that 9-O-acetylation of sialic acids determines streptococcal binding to salivary glycoproteins. These aims will be achieved by a combination of glycobiological and proteomics methods. PUBLIC HEALTH RELEVANCE: The proposed study sets out to add significance to the oral cavity being a main way of entry to both gastrointestinal and respiratory tracts by investigating the discriminating role of saliva in fostering oral colonization by a beneficial commensal microflora versus preventing infection by pathogenic microorganisms. This research is relevant to human health because the findings are expected to ultimately help understand tissue tropism of bacteria to the mouth and other mucus-lined tissues. Deciphering the molecular mechanisms underlying this tropism is expected to pave the way for future pharmacological prevention of colonization by undesired bacteria.