The role of arginine catabolic pathways in modulating staphylococcal fitness

摘要 尽管在临床护理方面取得了几十年的进步，但葡萄球菌感染的高发病率仍然是一个主要问题 公共卫生问题。多重耐药金黄色葡萄球菌与凝固酶阴性 表皮葡萄球菌经常在医院环境中分离出来，极大地限制了治疗。 选择。事实上，越来越明显的是，对葡萄球菌生物学的基本理解 而影响其适合性的因素是开发有效疗法所必需的。为了实现这个目标，我们 最近确定了包括一氧化氮在内的精氨酸分解代谢酶的重要生理功能 合酶(NOS)和精氨酸脱亚胺酶(ADI)在促进生长和控制细胞程序性死亡(PCD)中的作用 在葡萄球菌中。在正常生理条件下，一氧化氮合酶活性通过激活呼吸来促进生长 并防止代谢功能障碍，包括细胞内粘附素多糖的过度产生 (Pia)。然而，在酸性条件下，醋酸盐(葡萄糖代谢的副产物)流入细胞质 似乎破坏了一氧化氮合酶的正常功能，促进了一氧化氮合酶依赖的活性氧的产生 (ROS)和PCD。有趣的是，通过ADI途径的碳流量似乎可以对抗依赖一氧化氮合酶的PCD。 这些途径影响葡萄球菌生理学的机制仍在深入研究中。 并构成本申请的标的。在目标1中，我们将测试一氧化氮合酶如何通过抑制 Pia的产生是其正常生理活动的一部分。此外，我们将调查苯丙氨酸是否对 在一氧化氮合酶依赖的PIA抑制中的作用以及一氧化氮合酶活性是否影响肾小球疾病的致病潜能 葡萄球菌采用幼鼠中枢神经系统(CNS)导管感染模型。在目标2中，我们 将检验这一假设，即PCD期间依赖一氧化氮合酶的ROS产生是由于一氧化氮合酶解偶联，一个 一氧化氮合酶副产物产生超氧化物而不是一氧化氮的现象。最后，在目标3中，我们将 检测精氨酸脱亚胺酶和精氨酸酶途径通过激活过氧化氢酶对抗PCD的潜力 通过谷氨酸生物合成的活性。在完成这些研究后，我们将获得更深层次的机制 了解各种精氨酸分解代谢途径如何影响葡萄球菌的生理学和适合性。

ABSTRACT Despite decades of advances in clinical care, the high incidence of staphylococcal infections remain a major public health concern. Multiple antibiotic-resistant isolates of Staphylococcus aureus and coagulase-negative Staphylococcus epidermidis are frequently isolated in the hospital environment and significantly limit therapeutic options. Indeed, it is increasingly becoming evident that a fundamental understanding of staphylococcal biology and factors affecting its fitness are required for the development of effective therapeutics. Towards this goal, we have recently identified important physiological functions for arginine catabolic enzymes including nitric oxide synthase (NOS) and arginine deiminase (ADI), in promoting growth and controlling programmed cell death (PCD) in staphylococci. Under normal physiological conditions, NOS activity promotes growth by activating respiration and preventing metabolic dysfunction including excessive production of the polysaccharide intracellular adhesin (PIA). However, influx of acetate (a byproduct of glucose metabolism) into the cytoplasm under acidic conditions appears to corrupt normal function of NOS and promotes NOS-dependent production of reactive oxygen species (ROS) and PCD. Interestingly, carbon flux through the ADI pathway appears to counter NOS-dependent PCD. The mechanism by which these pathways affect staphylococcal physiology is still under intense investigation and constitutes the subject of this application. In Aim #1, we will test how NOS promotes growth by suppressing PIA production as part of its normal physiological activity. Further, we will investigate if phenylalanine plays a role in NOS-dependent PIA suppression and whether NOS activity affects the pathogenic potential of staphylococci using an infant mouse model of central nervous system (CNS) catheter infection. In Aim #2, we will test the hypothesis that NOS-dependent ROS production during PCD results from NOS uncoupling, a phenomenon wherein NOS generates superoxide rather than nitric oxide as byproduct. Finally in Aim #3, we will test the potential for the arginine deiminase and the arginase pathways in countering PCD by activating catalase activity through glutamate biosynthesis. On completion of these studies, we will gain a deeper mechanistic understanding of how various arginine catabolic pathways affect staphylococcal physiology and fitness.