Expression of clp genes in Streptococcus mutans

描述（由申请人提供）：变形链球菌被认为是龋齿的主要病原体。S.变形杆菌也是感染性心内膜炎的重要病原体。这种微生物通过在牙齿表面形成多种多样的多物种生物膜（称为牙菌斑）来定居口腔。这种病原体已经发展了多种机制来适应口腔的恶劣环境并在其中蓬勃发展。S.变形杆菌具有快速有效地响应各种环境通量的能力，包括严重的营养限制、pH和温度的波动以及氧化和渗透张力的变化。将细菌暴露于这些不利的环境中可以通过表达各种各样的基因来诱导应激耐受性反应，这些基因提供针对不同环境挑战的交叉保护。胁迫耐受性基因受独特的转录调节因子群调节，包括交替的σ因子。然而，与其他病原体不同，S.变形链球菌和其它链球菌不编码任何交替的σ因子。另一方面，在其他细菌中，一些在应激反应中起作用的基因也存在于S。变形链球菌基因组中，但其在胁迫和毒力中的作用尚未在变形链球菌中研究。变种人的详细信息一个这样的组是参与热和氧化应激反应的蛋白质的Clp（酪蛋白分解蛋白酶）家族。Clp家族由称为ClpP的小细胞质丝氨酸蛋白酶和各种ATP酶组成。S.变异体编码五种Clp ATP酶，ClpP与伴侣Clp ATP酶结合形成功能复合物，其特异性靶向受损或错误折叠的蛋白质以降解或易位。当ATP酶组分决定底物特异性时，ClpP降解受损的蛋白质。在大多数病原体中，ClpP在毒力方面起着非常重要的作用。例如，在S.在变形杆菌中，ClpP是最佳生物膜形成和耐酸性反应所必需的。虽然ClpP在致病机制中起重要作用，但对该病原体中clp基因的调控知之甚少。clp基因的调节非常复杂，并且可以根据生物体而显著变化。该建议的主要目标是深入了解clpP基因在S.变形菌在正常和应激条件下生长。此外，我们还建议研究一个重要的和独特的转录抑制因子，CtsR，这是重要的CLP基因，包括clpP，适应性反应过程中的表达。我们期望该项目的完成将导致在S.变种人此外，从该项目中获得的知识还可以扩展到其他重要的革兰氏阳性病原体（例如S. pnemetrium和S.化脓性链球菌，并可能导致新的药物靶点的鉴定。 公共卫生相关性：变形链球菌是一种存在于人类口腔中的细菌，在牙齿表面形成称为牙菌斑的细菌群落。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。我们的研究集中在一个重要基因的调控上，该基因使这种病原体能够在口腔的恶劣环境中生存，从而导致蛀牙。成功完成我们的研究可能会导致新的治疗方法的发展，以减少蛀牙。

DESCRIPTION (provided by applicant): Streptococcus mutans is considered as the major etiological agent in dental caries. S. mutans is also an important agent of infective endocarditis. The organism colonizes the oral cavity by forming diverse, multispecies biofilms on the tooth surface, known as dental plaque. This pathogen has developed multiple mechanisms to adapt and to flourish in the hostile environment of the oral cavity. S. mutans has the ability to respond rapidly and efficiently to various environmental fluxes, including severe nutrient limitation, fluctuations in pH and temperature, and changes in oxidative and osmotic tensions. Exposure of bacteria to these adverse environments can induce a stress tolerance response through expression of a wide variety of genes that provides cross-protection against diverse environmental challenges. Stress tolerance genes are regulated by unique groups of transcriptional regulators, including alternate sigma factors. However, unlike other pathogens, S. mutans and other streptococci do not encode any alternate sigma factors. On the other hand, some genes that putatively function in stress responses in other bacteria are present in the S. mutans genome, but their role in stress and virulence has not been investigated in S. mutans in great detail. One such group is the Clp (caseinolytic protease) family of proteins that are involved in thermal and oxidative stress responses. The Clp family is composed of a small cytoplasmic serine protease, called ClpP, and various ATPases. S. mutans encodes five Clp ATPases and ClpP associates with a partner Clp ATPase to form a functional complex that specifically targets damaged or misfolded proteins for degradation or translocation. While the ATPase component determines the substrate specificity, ClpP degrades the damaged protein. In most pathogens, ClpP plays a very important role in virulence. For example, in S. mutans, ClpP is required for optimal biofilm formation and acid-tolerance response. Although ClpP play important roles for the pathogenesis, very little is known about the regulation of the clp genes in this pathogen. Regulation of the clp genes is very complex, and can vary significantly depending on the organism. The main goal of this proposal is to gain insight into the expression of the clpP gene during S. mutans growth under normal and stressful conditions. Furthermore, we also propose to study an important and unique transcriptional repressor, CtsR, which is important for clp genes, including clpP, expression during adaptive response. We anticipate that completion of this project will lead to the identification of novel regulatory pathway for expression of stress response genes in S. mutans. Moreover, knowledge acquired from this project can also be extended to analysis of other important gram-positive pathogens such as S. pnemoniae and S. pyogenes, and may lead to the identification of novel drug targets. PUBLIC HEALTH RELEVANCE: Streptococcus mutans is a bacterium that resides in the human oral cavity, forming 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 studies are focused on the regulation of an important gene that enables this pathogen to survive in the hostile environment of the oral cavity to cause tooth decay. Successful completion of our studies could lead to the development of novel therapeutic treatments to reduce tooth decay.