Bacterial cation exporters: a new signaling paradigm for bacterial virulence

描述（由申请方提供）：肺炎链球菌是全球发病和死亡的主要原因。肺炎球菌能够在人类宿主的许多部位定植和复制，包括鼻咽（定植）、肺（肺炎）、血液（败血症）和脑（脑膜炎）。了解肺炎球菌疾病的发病机制的关键是了解细菌遇到的信号和对这些信号的特异性转录反应。一个未探索的环境是高浓度的，潜在的毒性，钙和其他金属遇到的肺炎球菌进入鼻咽和易位到血液。本申请将阐明S.通过研究环境阳离子对全球基因表达的特定作用以及表征两个新发现的宿主致病所需的阳离子外排系统，研究了肺炎克雷伯氏菌对二价阳离子的反应。在这项研究中，我们将描述特定的转录反应的S。通过微阵列和qRT-PCR两者，检测肺炎链球菌对钙、锰和锌的影响。这项研究提供了一个独特的视角，不仅可以确定对细胞外阳离子传感的整体反应，而且由于这些转运蛋白中的突变体积累了高水平的同源阳离子，因此可以确定细胞内阳离子浓度如何影响细胞信号传导途径。这些数据将用于进一步了解S. pneumoniae对宿主中遇到的各种信号的反应。转运蛋白本身将进行广泛的分子表征，包括通过测序临床菌株确定保守结构域，然后基于序列同源性产生突变体，以确定金属特异性和蛋白质功能的关键残基。通过在分子水平上表征这些转运蛋白所获得的知识将有助于我们理解细菌中的金属转运。公共卫生相关性：大多数以前的研究都集中在病原菌的金属收购，相比之下，我们的理解金属外流的病原菌仍然是一个有趣的问题。此外，由于这些转运蛋白是宿主致病所必需的，因此它们提供了新的抗菌靶标。通过了解赋予金属离子选择性和功能的残基，这些研究将提供更深入的了解致病菌利用的策略，以输出在人类宿主中大量发现的阳离子。

DESCRIPTION (provided by applicant): Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. The pneumococcus is able to colonize and replicate in a number of sites in the human host including the nasopharynx (colonization), lungs (pneumoniae), blood (sepsis, and the brain (meningitis). Crucial to understanding the pathogenesis of pneumococcal disease is understanding the signals encountered by the bacteria and the specific transcriptional response to these signals. An unexplored setting is the high, potentially toxic, concentrations of calcium and other metals encountered as the pneumococcus enters the nasopharynx and translocates to the bloodstream. This application will elucidate the transcriptional response of S. pneumoniae to divalent cations by investigating the specific roles of environmental cations on global gene expression as well as characterize two newly discovered cation efflux systems that are required for host pathogenesis. In this study we will characterize the specific transcriptional responses of S. pneumoniae to calcium, manganese, and zinc by both microarray and qRT-PCR. This study provides a unique perspective to not only determine the global response to extracellular cation sensing, but since mutants in these transporters accumulate high levels of their cognate cation, allows for the determination of how intracellular cation concentration can influence cell signaling pathways. These data will be used to further understand the specific responses of S. pneumoniae to the various signals encountered in the host. The transporters themselves will be subject to extensive molecular characterization including determining conserved domains via sequencing clinical strain and then generating mutants based on sequence homology to ascertain critical residues for metal specificity and protein function. The knowledge gained by characterizing these transporters at a molecular level will aid in our understanding of metal transport in bacteria. PUBLIC HEALTH RELEVANCE: A majority of previous studies in pathogenic bacteria has focused on metal acquisition, in contrast our understanding of metal efflux by pathogenic bacteria remains an intriguing question. Furthermore, as these transporters are required for host pathogenesis, they provide a novel antibacterial target. By understanding the residues conferring metal ion selectivity and function, these studies will provide greater insight into the strategies utilized by pathogenic bacteria to export cations found in abundance in the human host.