Coordination of metabolism and virulence during infection

说明(申请人提供)：沙门氏菌感染是发达国家和发展中国家发病率和死亡率的重要原因。沙门氏菌有2600多个血清型，表现出不同的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一些宿主隔间的不同条件，这在很大程度上是通过毒力和新陈代谢基因表达的变化来调节的。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，但这种生物的毒力和代谢基因的调控是通过涉及SIRA(沙门氏菌入侵调节因子)和CSRA(碳储存调节因子)的遗传电路错综复杂地联系在一起的。SIRA是一种DNA结合转录因子，是BARA-SIRA双组分信号转导系统的反应调节因子。CSRA是一种RNA结合蛋白，调节mRNA的翻译和稳定性。CSRA活性受隔离CSRA蛋白的非编码小RNA(CsrB，CSRC)调节。反过来，Sira激活了csrB和CSRC的转录。该系统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寄主之间有所不同，导致了这样的假设，即碳可获得性的状态在很大程度上控制着感染周期中的适应性转变。在目标1中，将结合基因组、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新陈代谢和毒力之间调节联系的理解。在目标2中，将使用几种互补的方法来准确确定该系统的基因在小鼠感染沙门氏菌期间何时何地表达和激活。这些信息将在与调节子(在目标1中定义)以及已知在体外影响这些调节子的环境和代谢条件的背景下进行评估。SIRA和CSRA同源基因在整个伽马蛋白细菌中高度保守，在它们所检测的每个物种中对疾病传播和/或毒力都是重要的。因此，了解影响SIRA和CSRA活性的条件和刺激，以及这些蛋白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。 与公共卫生相关：抗生素治疗相对无效，是沙门氏菌胃肠道感染的禁忌，但有可能在婴儿和免疫功能受损的患者中发展为危及生命的感染。沙门氏菌和许多其他种类的细菌利用一种古老的调节系统来控制新陈代谢和毒力。确定在哺乳动物宿主中管理这一调控系统的条件，并确定该系统发挥作用的机制和遗传电路，可能有助于疫苗设计，并为抗生素和益生菌治疗提出新的靶点和策略。

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. PUBLIC HEALTH RELEVANCE: Antibiotic therapies are relatively ineffective and are contraindicated for Salmonella gastrointestinal infections, which nevertheless have the potential to progress to life-threatening infections in infants and immunocompromised patients. Salmonella and many other species of bacteria utilize an ancient regulatory system to control metabolism and virulence. Determining the conditions that govern this regulatory system within the mammalian host, and determining the mechanisms and genetic circuitry by which this system functions may facilitate vaccine design and suggest novel targets and strategies for antibiotic and probiotic therapies.