Coordination of metabolism and virulence during infection

描述（由申请人提供）：沙门氏菌感染是发达国家和发展中国家发病和死亡的重要原因。沙门氏菌有超过 2600 种血清型，具有多种宿主范围和疾病表现，包括胃肠炎、菌血症、转移性感染以及副伤寒和伤寒。在所有情况下，感染都需要细菌适应许多宿主区室的不同条件，这在很大程度上是由毒力和代谢基因表达的变化介导的。了解感染周期中的这些适应对于制定预防和治疗感染的新策略非常重要。尽管知识有限，但该生物体的毒力和代谢基因的调节通过涉及 SirA（沙门氏菌入侵调节因子）和 CsrA（碳储存调节因子）的遗传回路错综复杂地联系在一起。 SirA 是一种 DNA 结合转录因子，是 BarA-SirA 二元信号转导系统的反应调节因子。 CsrA 是一种 RNA 结合蛋白，可调节 mRNA 翻译和稳定性。 CsrA 活性受小非编码 RNA（CsrB、CsrC）调节，这些小非编码 RNA 隔离 CsrA 蛋白。反过来，csrB 和 csrC 的转录被 SirA 激活。该系统的调节对碳代谢的底物和最终产物做出反应，这些底物和最终产物在宿主室内有所不同，从而导致了这样的假设：碳可用性的状态在很大程度上控制着感染周期期间的适应性转变。在目标 1 中，将结合基因组学、生物信息学、分子遗传学和生化方法来定义 SirA 和 CsrA 调节子，从而大大增加我们对代谢和毒力之间调节联系的理解。在目标 2 中，将使用几种补充方法来精确确定该系统的基因在小鼠沙门氏菌感染期间表达和活跃的时间和地点。该信息将根据调节子（目标 1 中定义）以及已知在体外影响这些调节器的环境和代谢条件进行评估。 SirA 和 CsrA 直向同源物在整个 γ-变形菌中高度保守，对于已检测它们的每个物种的疾病传播和/或毒力都很重要。因此，了解影响SirA和CsrA活性的条件和刺激以及这些蛋白质协调毒力和代谢基因表达的机制可能适用于广泛的病原体。

DESCRIPTION (provided by applicant): Salmonella infections are a significant cause of morbidity and mortality in both developed and developing nations. There are over 2600 serovars of Salmonella that exhibit a variety of host ranges and disease manifestations, which include gastroenteritis, bacteremia, metastatic infections and paratyphoid and typhoid fevers. In all cases, infection requires adaptation of the bacterium to distinct conditions of a number of host compartments, mediated in large part by changes in the expression of virulence and metabolism genes. Understanding these adaptations during the infection cycle is important for developing new strategies for preventing and treating infection. Although knowledge is limited, regulation of the virulence and metabolism genes of this organism are intricately linked through genetic circuitry involving SirA (Salmonella invasion regulator) and CsrA (carbon storage regulator). SirA is a DNA binding transcription factor that is the response regulator of the BarA-SirA two component signal transduction system. CsrA is an RNA binding protein that regulates mRNA translation and stability. CsrA activity is regulated by small noncoding RNAs (CsrB, CsrC), which sequester the CsrA protein. In turn, the transcription of csrB and csrC is activated by SirA. Regulation by this system responds to substrates and end products of carbon metabolism, which vary within host compartments, leading to the hypothesis that the status of carbon availability in large part governs adaptive transitions during the infection cycle. In Aim 1, a combination of genomic, bioinformatic, molecular genetic and biochemical approaches will be used to define the SirA and CsrA regulons, and thereby greatly increase our understanding of the regulatory links between metabolism and virulence. In Aim 2, several complementary approaches will be used to determine precisely when and where genes of this system are expressed and active during Salmonella infection of mice. This information will be evaluated in context with the regulons (defined in Aim 1) as well as the environmental and metabolic conditions that are known to influence these regulators in vitro. SirA and CsrA orthologs are highly conserved throughout the gamma-proteobacteria and are important for disease transmission and/or virulence in every species in which they have been examined. Thus, an understanding of the conditions and stimuli affecting SirA and CsrA activities and the mechanisms by which these proteins coordinate virulence and metabolic gene expression may be applicable to a broad range of pathogens.