Characterization of a unique two-component system in streptococci

描述(申请人提供)：细菌有许多双组分信号转导系统(TCS)，通过改变响应调节器的磷酸化状态来响应特定的环境信号。尽管这些系统被认为形成了一个错综复杂的信号网络，但它们如何相互作用的详细机制在很大程度上仍未得到解释。在这一应用中，我们将以变形链球菌作为模式生物来研究细菌中一种新的信号通路。变形链球菌被认为是龋病的主要病原体，有时也是感染性心内膜炎的病原体。这种病原菌通过形成多种生物膜来定植口腔，并发展了各种机制来适应口腔恶劣的环境并在其上繁衍生息。我们发现，一种特殊的TCS，LianFSR，除了传感器激酶(LIAS)和反应调节因子(LIAR)外，还编码额外的蛋白质(LIAF)，调节GBPC的表达，GBPC编码生物膜形成和心内膜炎发生所必需的葡聚糖结合蛋白。我们还发现，LianFSR对于生产细菌素突变素是必要的，以抑制生物膜群落中存在的其他竞争细菌的生长。最近的一项微阵列研究表明，174个基因，约占基因组的9%，受这种TCS的调控。在芽孢杆菌和葡萄球菌中，这种TCS参与了对各种抗生素引起的细胞壁破坏的感知，特别是那些干扰脂-II循环的抗生素。然而，这种TCS所感受到的信号以及链球菌中信号转导的分子机制尚不清楚。一个令人困惑的问题是LiAs和Liar如何调节变形链球菌中的靶基因表达，因为在许多情况下，Lias和Liar的灭活不会产生任何明显的表型。在这个应用中，基于我们的初步结果，我们提出了一个模型来解释Lias和Liar如何参与信号转导。我们还提出了LIAF在LianSR介导的基因调控中的可能作用。特定的目标1和2旨在检验我们的假设，以确定LIAS和LIAF参与信号转导的机制。目标3的目的是了解说谎者与DNA结合的分子机制。完成后，我们希望确定LianFSR的细胞作用，这可能会导致更多的方法来控制这种病原体。这项研究也将促进我们对变形链球菌和其他相关病原体如A组和B组链球菌基因调控和信号转导的分子机制的全面了解。 与公共健康相关：细菌有许多双组分信号转导系统(TCS)，通过改变反应调节器的磷酸化状态来对特定的环境信号做出反应。尽管这些系统被认为形成了一个错综复杂的信号网络，但它们如何相互作用的详细机制在很大程度上仍未得到解释。在这项申请中，我们建议揭开TCS和变形链球菌中另一条信号通路之间的新的相互作用，变形链球菌是一种驻留在人类口腔中的细菌，在牙齿表面形成细菌群落，称为牙菌斑。变形链球菌会导致龋齿，这是一种代价极其高昂的全球健康问题，影响着工业化国家60%-90%的学童和许多成年人，仅在美国每年就导致数十亿美元的支出。我们的研究重点是对编码产物的基因进行调控，这些产物使这种病原体能够在口腔中生存并导致龋齿。成功完成我们的研究可能会导致开发新的治疗方法来限制这种细菌的生长和减少龋齿。

DESCRIPTION (provided by applicant): Bacteria have many two-component signal-transduction systems (TCSs) that respond to specific environmental signals by altering the phosphorylated state of a response regulator. Although these systems are presumed to form an intricate signal network, the detailed mechanism of how they interact with each other remains largely unexplained. In this application, we will use Streptococcus mutans as a model organism to study a novel signaling pathway in bacteria. S. mutans is considered to be the primary etiological agent of dental caries and sometimes in infective endocarditis. This pathogen colonizes the oral cavity by formation of multispecies biofilm and has developed a variety of mechanisms to adapt and to flourish in the hostile environment of the oral cavity. We found that one particular TCS, LiaFSR, which encodes an extra protein (LiaF) in addition to the sensor kinase (LiaS) and the response regulator (LiaR), regulates the expression of gbpC that encodes a glucan-binding-protein necessary for biofilm formation and the onset of endocarditis. We also found that LiaFSR is necessary for the production of mutacin, a bacteriocin, to suppress the growth of other competitor bacteria present in the biofilm community. A recent microarray study revealed that 174 genes, ~9% of the genome, are regulated by this TCS. In Bacillus and Staphylococcus, this TCS is involved in sensing cell wall damage caused by various antibiotics, particularly those antibiotics that interfere with the lipid- II cycle. However, the signals sensedby this TCS and the molecular mechanism of signal transduction in streptococci are yet to be identified. A puzzling question is how LiaS and LiaR regulate target gene expression in S. mutans, since inactivation of LiaR does not produce, in many cases, any noticeable phenotypes. In this application, based on our preliminary results, we propose a model to explain how LiaS and LiaR may participate in signal transduction. We also propose a possible role for LiaF in LiaSR mediated gene regulation. Specific Aims 1 and 2 are designed to test our hypothesis to determine the mechanisms by which LiaS and LiaF participate in signal transduction. The goal of Aim 3 is to understand the molecular mechanism of DNA binding by LiaR. Upon completion, we hope to determine the cellular role of the LiaFSR that may lead to greater means of controlling this pathogen. This investigation will also promote our overall understanding of the molecular mechanisms of gene regulation and signal transduction in S. mutans and other related pathogens such as group A- and group B- streptococcus. PUBLIC HEALTH RELEVANCE: Bacteria have many two-component signal-transduction systems (TCSs) that respond to specific environmental signals by altering the phosphorylated state of a response regulator. Although these systems are presumed to form an intricate signal network, the detailed mechanism of how they interact with each other remains largely unexplained. In this application we propose to unravel a novel interaction between a TCS and another signaling pathway in Streptococcus mutans, a bacterium that resides in the human oral cavity and forms bacterial communities on the tooth surface known as dental plaque. S. mutans causes tooth decay, an extremely costly global health problem that affects 60-90% of school children and many adults in industrialized countries, and results in annual expenditures of billions of dollars in the U.S. alone. Our study focuses on the regulation of genes that encode products that enable this pathogen to survive in the oral cavity and to cause tooth decay. Successful completion of our studies could lead to the development of novel therapeutic treatments to limit the growth of this bacterium and reduce tooth decay.