Rat, a regulator of autolysis in S. aureus

描述（申请人提供）：金黄色葡萄球菌是一种主要的人类病原体；由于出现抗生素耐药性，有必要制定新的抗微生物策略。我们已经确定了一个参与自溶的调控系统作为一个新的目标。细菌细胞壁的完整性通常通过两个相互竞争的过程来维持：细胞壁合成和自溶活性。细胞壁的合成是由PBP介导的，而蛋白水解酶则介导裂解过程。这两个过程之间的不平衡可能导致细胞裂解。我们最近在金黄色葡萄球菌中发现了一个叫做大鼠的调控位点；大鼠的突变导致生长缺陷和小鼠水解酶活性增加，而细胞壁合成相对不受干扰。因此，与亲本菌株相比，大鼠突变体具有增强的洗涤剂和青霉素诱导裂解。由于大鼠蛋白与MarR蛋白家族更同源，我们假设大鼠基因产物是金黄色葡萄球菌自溶活性的独特调节剂。大鼠还抑制另一种叫做sarV的基因，这是最近描述的SarA蛋白家族的一员。与大鼠相反，sarV的突变使突变体更能抵抗裂解。我们推测大鼠可能通过抑制sarV来控制金黄色葡萄球菌的自溶。为了了解大鼠和sarV的内部工作原理，促进新的治疗方法的发展，我们提出以下五个具体目标：1)表征大鼠和sarV在体外自溶中的相互作用和调控途径；II)评价大鼠和sarV在洗涤剂和抗生素介导的细胞裂解中的作用；III)确定大鼠和sarV在体外调控毒力决定因素中的作用；IV)通过测定高水平表达sarV的大鼠突变株和毒株的转录谱和靶自溶素，确定大鼠和sarV结合的基因启动子，评估大鼠和sarV的靶基因；IV)评估大鼠和sarV在兔心内膜炎模型中的毒力和抗生素治疗反应的作用。在完成这些研究后，我们希望了解大鼠和sarV在控制自溶的调节网络中的作用。我们的长期目标是通过抗大鼠或亲sarv策略促进自溶，而不会对毒力产生不利影响。

DESCRIPTION (provided by applicant): S. aureus is a major human pathogen; because of emerging antibiotic resistance, there is a need to develop new antimicrobial strategies. We have identified a regulatory system involved in autolysis as a novel target. The integrity of the cell wall in bacteria is generally maintained by two competing processes: cell wall synthesis and autolytic activity. While synthesis of the cell wall synthesis is mediated by PBP, murein hydrolases mediate the lytic process. An imbalance between these two processes may lead to cell lysis. We recently identified a regulatory locus called rat in S. aureus; a mutation in rat resulted in a growth defect and increased murein hydrolase activity while leaving cell wall synthesis relatively unperturbed. Consequently, the rat mutant had enhanced detergent and penicillin induced lysis as compared with the parental strain. As the Rat protein is more homologous to the MarR protein family, we hypothesize that the rat gene product is a unique regulator of autolytic activity in S. aureus. Rat also represses another gene called sarV, a member of the recently described SarA protein family. Contrary to rat, a mutation in sarV rendered the mutant more resistant to lysis. We speculate that rat may repress sarV to control autolysis in S. aureus. To understand the inner working of rat and sarV and to facilitate the development of a novel therapeutic approach, we propose the following five specific aims: I) characterizing the interaction and regulatory pathways of rat and sarV in autolysis in vitro; II) Evaluating the role of rat and sarV in detergent and antibiotic mediated cell lysis; III) Determining the role of rat and sarV in the regulation of virulence determinants in vitro; IV) Assessing the target genes of rat and sarV by determining the transcriptional profile and target autolysins of the rat mutant and strains expressing a high level of sarV and determining the gene promoters to which Rat and SarV bind; IV) Evaluating the role of rat and sarV in virulence and responses to antibiotic therapy in the rabbit endocarditis model. Upon completion of these studies, we hope to understand the role of rat and sarV within the network of regulators that control autolysis. Our long-term goal is to promote autolysis with an anti-Rat or pro-SarV strategy without developing an untoward impact on virulence.