The role of GraRS in resistance to cationic antimicrobial peptides in S. aureus

描述（由申请人提供）：S。金黄色葡萄球菌是高度适应性的人类病原体。这种适应的一个结果是它能够产生耐药性阳离子抗菌肽（CAP），这是宿主先天免疫的重要组成部分。在细读S.在金黄色葡萄球菌基因组中，我们发现了四个两组分调节系统，每个系统与ABC转运系统相邻。其中一个系统，GraRS，调节相邻的VraFG流出系统，包括ATP酶和膜透性酶。graR或vraG中的突变导致对CAP如RP-1（来自血小板的PMP-1的同源物）和hNP-1（来自嗜中性粒细胞）、indolicidin和LL 37的抗性降低。作为一种血管内病原体，S.金黄色葡萄球菌可能遇到来自血小板和中性粒细胞的CAP（RP-1和hNP-1），我们将在本提案中重点讨论。S.基于诱导研究和微阵列分析，金黄色葡萄球菌对选择性CAP的抗性也导致了graRS和vraFG以及其他相关CAP抗性的基因的诱导，包括mprF、dltABCD以及另一组ABC转运蛋白基因vraDE。然而，这些基因在S.金黄色葡萄球菌未定义（目的I）。此外，与S.表皮葡萄球菌中graRS和vraFG的表达可由任何CAP诱导，S.金黄色葡萄球菌更具选择性，仅对少数CAP有反应。基于S.金黄色葡萄球菌和epidermidis，我们建议定义确切的残基内GRAS介导这种识别特异性CAP诱导下游基因（目的II）。除了细菌因素，我们还感兴趣的合成CAP的结构和它们的能力，结合和诱导表达的graRS（目的III）。最后，将在感染性心内膜炎的相关兔模型中探索GraRS中这些发现的体内相关性。总之，这些研究将为沙门氏菌对相关宿主CAP的先天抗性提供科学依据。金黄色葡萄球菌，从而提供了一个平台，设计策略，以减轻耐药性的阳离子抗菌肽。

DESCRIPTION (provided by applicant): S. aureus is a highly adaptive human pathogen. One result of this adaptation is its ability to develop resistance cationic antimicrobial peptides (CAPs), which are an important part of innate immunity in the hosts. In perusing the S. aureus genomes, we found four two component regulatory systems each of lie adjacent to an ABC transporter system. One of the system, GraRS, regulates the adjacent VraFG efflux system comprising an ATPase and a membrane permease. Mutations in graR or vraG have led to a reduction in resistance to CAPs such as RP-1 (a congener to PMP-1 from platelets) and hNP-1 (from neutrophils), indolicidin and LL37. As an intravascular pathogen, S. aureus likely encounters CAPs from platelets and neutrophils (RP-1 and hNP-1), which we will focus on in this proposal. The exposure of S. aureus to selective CAP has also led to induction of graRS and vraFG and other genes relevant CAP resistance including mprF, dltABCD and also another set of ABC transporter genes vraDE, based on induction studies and microarray analysis. However, the exact contribution of these genes to CAP resistance mediated by GraRS in S. aureus is not defined (Aim I). In addition, in contrast to S. epidermidis where the expression of graRS and vraFG can be induced by any CAPs, the induction in S. aureus is more selective, responding to only a few CAPs. Based on the difference in the sequence of the kinase sensor GraS between S. aureus and S. epidermidis, we propose to define the exact residues within GraS that mediate this recognition of specific CAPs for induction of downstream genes (Aim II). Besides the bacterial factors, we are also interested in the structure of synthetic CAPs and their ability to bind and induce expression of graRS (Aim III). Finally, the in vivo correlate of these finding in GraRS will be explored in a relevant rabbit model of infective endocarditis. Together, these studies will elicit the scientific basis of innate resistance to relevant host CAPs in S. aureus, thus providing a platform to devise strategies to alleviate resistance to cationic antimicrobial peptides.