NRG1 Regulated Genes in Candida albicans Pathogenicity

描述（由申请人提供）：白色念珠菌是念珠菌病最常见的病原，目前是医院感染的第四大原因。即使采用积极的药物治疗，患者的预后也不佳，死亡率在30-50%之间，更不用说与治疗相关的重大经济负担。白色念珠菌能够在单细胞酵母样和丝状形态之间进行可逆的形态转变，这一特性被认为是其致病潜力的关键。然而，目前对白色念珠菌毒力中形态发生所起作用的理解主要是基于无法经历这种发育过程的基因定义突变菌株的研究数据。为了克服这些问题，我们构建了一个可调节tet-NRG1的菌株（SSY50-B），其形态发生转化可以在体外和体内进行外部操纵。使用该菌株进行的毒力研究提供了迄今为止将这种机会致病菌的形态发生和毒力联系起来的最令人信服的证据。本应用旨在进一步探索NRG1调控白色念珠菌丝化和毒力的机制，我们提出了三个具体目标：i)利用基因筛选鉴定在白色念珠菌丝化和发病机制中发挥关键作用的nrg1调控基因；ii)通过构建“敲除”突变株并在小鼠传播性念珠菌病模型中进行测试，评估nrg1调控基因在毒力中的个体作用；iii)筛选小分子文库，通过模拟白色念珠菌Nrglp功能来鉴定抑制丝化和毒力的化合物。

DESCRIPTION (provided by applicant): Candida albicans is the most common etiological agent of candidiasis, now the fourth leading cause of nosocomial infections. Even with aggressive drug therapy the prognosis for the patient is not good with mortality rates ranging from 30-50%, not to mention the significant economic burden associated with treatment. C. albicans is able to undergo reversible morphological transitions between unicellular yeast-like and filamentous forms and it is this attribute that is considered pivotal to its pathogenic potential. However, the current understanding of the role played by morphogenesis in C. albicans virulence is based primarily on data obtained from studies using genetically defined mutant strains unable to undergo this developmental programme. To overcome these concerns, we have constructed a tet-NRG1 regulatable strain (SSY50-B) in which morphogenetic conversions can be externally manipulated both in vitro and in vivo. Virulence studies performed using this strain have provided the most compelling evidence to date linking morphogenesis and virulence in this opportunistic pathogen. This application aims to further explore the mechanisms by which NRG1 regulates C. albicans filamentation and virulence for which we propose three specific aims: i) to use a genetic screen to identify NRG1-regulated genes that play key roles in C. albicans filamentation and pathogenesis, ii) to assess the individual roles of the NRG1-regulated genes in virulence by constructing "knock out" mutant strains and testing them in a murine model of disseminated candidiasis and iii) to screen small molecule libraries to identify compounds that inhibit filamentation and virulence by mimicking C. albicans Nrglp function. Relevance to public health: Candida albicans is the main causative agent of candidiasis, the most frequent fungal infection and now the fourth leading cause of infections in US hospitals, with high mortality rates and soaring economic burden. The main idea behind this study is to further investigate the relationship between filamentation and virulence, as controlled by key regulatory genes, which may serve as the basis for the development of novel strategies for the treatment of these infections.