THE LOW CALCIUM RESPONSE AND CYTOTOXIC EFFECT OF PLAGUE

低钙反应（LCR）是一个重要的决定因素的毒力， 鼠疫耶尔森氏菌，斑块的病原体，以及在另外两个人， 同一属的病原菌，Y. entercolitica和Y.假结核病 观察到LCR是两种新的生长和表达的停止。 蛋白质，V和W抗原，当在无Ca2+培养基中培养时， 从26摄氏度变成了37摄氏度 一组外 膜蛋白也与LCR基因相关。 LCR被认为是 当Y.鼠疫 进入细胞内环境， 生长，LCR可以帮助细菌适应细胞内 条件 我们最近在Y.鼠疫 特异于编码LCR的质粒。 这种影响可能是主要的 LCR对毒力的贡献。 本项目将集中在细胞毒效应，V抗原，和调节 温度和Ca2+浓度对LCR的影响。 相关基因 这些现象中的每一种都将被识别，它们的功能将被确定， 它们对毒力表达的重要性进行了评估。 这些目标将是 通过对具有特定缺陷的突变体进行详细的遗传分析来完成 在细胞毒性的表达或LCR的调节中， 在小鼠中的毒力测试以及表型的体外分析。 为 例如，Ca2+的调节将用以下缺陷的突变体进行研究： 检测Ca2+的能力。 这种突变体仍然表现出温度 法规和表达LCR在37摄氏度的其他功能，无论是或 不存在Ca2+。 此外，构建的操纵子融合菌株 将使用Ca2+调节分析来确定Ca2+是否 调控基因被Y的进入所诱导。进入动物细胞。 越来越清楚的是，毒力基因的调控是一个重要的机制。 重要但研究较少的发病机制方面。 该项目将 提供了对所采用的规则的第一个详细描述之一 被一种兼性细胞内病原体感染 它还可以建立 细胞毒性是LCR对毒力的主要贡献。

The low calcium response (LCR) is an essential determinant of virulence in Yersinia pestis, the causative agent of plaque, and in two other human pathogens of the same genus, Y. entercolitica and Y. psuedotuberculosis. LCR is observed as cessation of growth and expression of two novel proteins, the V and W antigens, when cultures in Ca2+ free medium are shifted from 26 degrees C to 37 degrees C. Expression of a group of outer membrane proteins is also associated with the LCR genes. LCR is thought to be triggered by the low free Ca2+ concentrations encountered when Y. pestis enters the intracellular environment and thus, rather than restricting growth, LCR may aid the bacteria in adaptation to intracellular conditions. We have recently observed a cytotoxic effect in Y. pestis specific to the plasmid which encodes LCR. This effect could be the major contribution of LCR to virulence. This project will focus on the cytotoxic effect, V antigen, and regulation of LCR by temperature and by Ca2+ concentration. The genes involved in each of these phenomena will be identified, their function determined and their importance for expression of virulence assessed. These goals will be accomplished by detailed genetic analysis of mutants with specific defects in expression of cytotoxicity or in regulation of LCR, coupled with virulence testing in mice as well as in vitro analysis of phenotypes. For example, regulation by Ca2+ will be investigated with mutants defective in their ability to detect Ca2+. Such mutants still exhibit temperature regulation and express the other features of LCR at 37 degrees C whether or not Ca2+ is present. Additionally, operon fusion strains constructed for analysis of Ca2+ regulation will be used to determine whether or not Ca2+ regulated genes are induced by entry of Y. pestis into animal cells. It is becoming increasingly clear that regulation of virulence genes is an important but poorly studied aspect of pathogenesis. This project will provide one of the first detailed descriptions of the regulation employed by a facultative intracellular pathogen. It may also establish cytotoxicity as the major contribution of LCR to virulence.