Characterization of a unique two-component system in streptococci

描述（由申请人提供）：细菌具有许多双组分信号转导系统（TCS），其通过改变响应调节剂的磷酸化状态来响应特定的环境信号。虽然这些系统被认为形成了一个复杂的信号网络，但它们如何相互作用的详细机制在很大程度上仍然无法解释。在本申请中，我们将使用变形链球菌作为模式生物来研究细菌中的新信号通路。S.变形菌被认为是龋齿的主要病原体，有时也是感染性心内膜炎的主要病原体。该病原体通过形成多物种生物膜而定殖于口腔，并且已经发展了多种机制以适应口腔的不利环境并在口腔的不利环境中繁殖。我们发现，一种特殊的TCS，LiaFSR，除了传感器激酶（LiaS）和反应调节因子（LiaR）外，还编码一种额外的蛋白质（LiaF），调节gbpC的表达，gbpC编码生物膜形成和心内膜炎发作所必需的葡聚糖结合蛋白。我们还发现，LiaFSR是生产变链蛋白（一种细菌素）所必需的，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显示，174个基因，约9%的基因组，是由这个TCS。在芽孢杆菌属和葡萄球菌属中，该TCS参与感知由各种抗生素引起的细胞壁损伤，特别是那些干扰脂质- II循环的抗生素。然而，该TCS所感知的信号以及链球菌中信号转导的分子机制尚待确定。一个令人困惑的问题是LiaS和LiaR如何调节S中靶基因的表达。在许多情况下，由于LiaR的失活不产生任何明显的表型，因此，在许多情况下，LiaR不产生任何明显的表型。在本申请中，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LiaSR介导的基因调控中的可能作用。具体目的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。目的3的目标是了解LiaR结合DNA的分子机制。完成后，我们希望确定LiaFSR的细胞作用，这可能会导致控制这种病原体的更好方法。本研究也将促进我们对S.变形菌和其它相关病原体如A组和B组链球菌。 公共卫生相关性：细菌具有许多双组分信号转导系统（TCS），其通过改变响应调节剂的磷酸化状态来响应特定的环境信号。虽然这些系统被认为形成了一个复杂的信号网络，但它们如何相互作用的详细机制在很大程度上仍然无法解释。在本申请中，我们提出要解开TCS和变形链球菌中的另一种信号通路之间的新型相互作用，变形链球菌是一种存在于人类口腔中并在牙齿表面形成细菌群落的细菌，称为牙菌斑。S.变形杆菌引起蛀牙，这是一种代价极其高昂的全球性健康问题，影响工业化国家60-90%的学龄儿童和许多成年人，仅在美国每年的花费就达数十亿美元。我们的研究重点是基因的调控，这些基因编码的产物使这种病原体能够在口腔中生存并导致蛀牙。我们研究的成功完成可能会导致新型治疗方法的开发，以限制这种细菌的生长并减少蛀牙。

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.