Inducible Antibiotic Resistance in Methicillin-Resistant Staphylococcus aureus

项目总结/摘要 耐甲氧西林金黄色葡萄球菌（MRSA）是一种有问题的人类细菌病原体， 对β-内酰胺类抗生素具有广泛耐药性。这种抗性是可诱导的，由一组基因赋予， 编码抗生素传感器/信号转导蛋白、基因阻遏物和两个抗性决定子（a A类β-内酰胺酶和命名为PBP 2a的独特青霉素结合蛋白（PBP）。共价结合 β-内酰胺抗生素与传感器/信号转导蛋白的表面结构域的结合启动了 抗性，其需要细胞质侧的生化事件，涉及基因的蛋白水解 阻遏物和转录的基因的抗病性决定因素。我们处理序列 细胞质中发生的事件的详细描述。我们在具体目标1中建议研究两个 MRSA在识别表面上的抗生素后所经历的反应。一个是碎片化 BlaR 1（传感器/转换器蛋白）在其细胞质蛋白酶结构域，这被认为是激活它 (i.e.,把它从延迟中带出来）。另一个是我们称之为BlaR 2的蛋白质的磷酸化。我们建议 证明了胞质结构域的蛋白水解启动了诱导的开始。BlaR 2的磷酸化 还增强表面上的抗生素识别，并且对于抗生素应答是必需的。我们建议 鉴定和表征BlaR 2，并确定其磷酸化位点，以阐明功能联系 BlaR 1的激活和BlaR 2的磷酸化之间的关系。在具体目标2中，我们希望建立在我们的 BlaR 2磷酸化抑制剂的初步发现， β-内酰胺抗生素的增效剂。这类化合物可以阻止BlaR 2磷酸化， 记录导致微生物对β-内酰胺抗生素致敏。这样一类分子具有 β-内酰胺类抗生素在MRSA感染治疗中的应用潜力。MRSA有 已经存在了50多年这些研究将明确阐明复杂的机制， MRSA菌株已进化为对β-内酰胺抗生素的耐药性。

Project Summary/Abstract Methicillin-resistant Staphylococcus aureus (MRSA) is a problematic human bacterial pathogen, which is broadly resistant to β-lactam antibiotics. This resistance is inducible and is conferred by a set of genes that encode an antibiotic sensor/signal transducer protein, a gene repressor and two resistance determinants (a class A β-lactamases and a unique penicillin-binding protein (PBP) designated as PBP2a). Covalent binding of the β-lactam antibiotic to the surface domain of the sensor/signal transducer protein initiates the induction of resistance, which entails biochemical events on the cytoplasmic side involving proteolysis of the gene repressor and transcription of the genes for the antibiotic-resistance determinants. We address the sequence of events that take place in the cytoplasm in this grant application. We propose in Specific Aim 1 to study two responses that MRSA experiences after the recognition of the antibiotic on the surface. One is a fragmentation of the BlaR1 (the sensor/transducer protein) in its cytoplasmic protease domain, which is believed to activate it (i.e., bring it out of latency). Another is phosphorylation of a protein that we refer to as BlaR2. We propose to document that proteolysis of the cytoplasmic domain initiates the onset of induction. Phosphorylation of BlaR2 also ensues antibiotic recognition on the surface and is essential for the antibiotic response. We propose to identify and characterize BlaR2 and determine the site of its phosphorylation in elucidating a functional link between activation of BlaR1 and phosphorylation of BlaR2. In Specific Aim 2, we would like to build on our preliminary findings on inhibitors of BlaR2 phosphorylation in identification of molecules that could serve as potentiators of β-lactam antibiotics. This class of compounds prevents BlaR2 phosphorylation, which we have documented to result in sensitization of the organism to β-lactam antibiotics. Such a class of molecules has the potential of bring back β-lactam antibiotics from obsolescence in treatment of MRSA infections. MRSA has been with humanity for over 50 years. These studies will shed definitive light on the complex machinery that MRSA strains have evolved for resistance to β-lactam antibiotics.