RFG1 Regulation of Candida albicans Filamentation and Virulence

描述(申请人提供)：白色念珠菌是迄今为止最常见的人类分离真菌。它是人类的正常共生体，但也能够入侵人体的几乎每一个部位，并导致感染，特别是在不断扩大的免疫受损宿主群体中，包括那些感染艾滋病毒的人。这种生物体能够在单细胞酵母状(芽孢子)和丝状(根据丝状结构的微小变化而称为菌丝或伪菌丝)之间经历可逆的形态转变，以响应外部环境的变化，这种能力被认为是其致病潜力的关键。然而，这一信念主要是基于对无法经历这种形态发生转换的白色念珠菌突变株(即Delta-cph1、Delta-Efg1、Delta-Tup1、Delta-NRG1)进行的大量毒力研究的结果：因为所有这些菌株都以一种或另一种形式锁定，所以不能就形态发生转换在毒力中的作用得出明确的结论。在之前的研究中，我们设计了一个条件突变菌株，其中丝状化的负调控因子(NRG1)被置于四环素可调节启动子的控制下。对该菌株的分析表明，这些形态转变可以在体外和感染期间在动物(小鼠)宿主内进行修改。在这一应用中，我们建议将这些研究扩展到白念珠菌(RFG1)中唯一已知的这一过程的其他负调控因子，以更密切地检查和进一步定义这种重要真菌病原体的感染过程。这将首先通过构建一个tet-RFG1可调节的白色念珠菌菌株来实现，就像我们对NRG1基因所做的那样，然后分析它在体外和感染过程中的行为。此外，我们将进行全基因组转录图谱，以确定哪些白色念珠菌基因受到Rfg1p蛋白的负面调控，以及这些基因如何影响毒力。与公共卫生相关：白色念珠菌是念珠菌病的主要病原体，是最常见的真菌感染，现在是美国医院感染的第四大原因，死亡率高，经济负担飙升。这项研究的主要思想是进一步研究丝状化和毒力之间的关系，这是由关键调控基因控制的，这可能成为开发治疗这些感染的新策略的基础。

DESCRIPTION (provided by applicant): Candida albicans is by far the most frequently isolated fungus from humans. It is a normal commensal of Man but is also capable of invading almost every site in the body and causing infections especially in an expanding population of immunocompromised hosts, including those infected with HIV. The organism is able to undergo reversible morphological transitions between unicellular yeast-like forms (blastospores) and filamentous forms (called hyphae or pseudohyphae depending on slight variations in the structure of the filament), in response to changes in the external environment, and this ability is considered pivotal to its pathogenic potential. However, this belief is based primarily upon the results obtained from a large number of virulence studies using C. albicans mutant strains unable to undergo this morphogenetic switch (i.e. delta-cph1, delta-efg1, delta-tup1, delta-nrg1): because all of these strains are locked in one or other form, definitive conclusions on the role of the morphogenetic conversion in virulence cannot be made. In a previous study, we engineered a conditional mutant strain in which a negative regulator (NRG1) of filamentation was placed under the control of a tetracycline regulatable promoter. Analysis of this strain revealed that these morphological transitions could be modified both in vitro and also within an animal (mouse) host during an infection. In this application, we propose to extend these studies to the only other known negative regulator of this process in C. albicans (RFG1) to more closely examine and further define the infectious process of this important fungal pathogen. This will be achieved first through the construction of a tet-RFG1 regulatable C. albicans strain, as we did for the NRG1 gene, then analyzing its behavior both in vitro and then during the course of an infection. In addition, we will perform genome wide transcriptional profiling to determine which C. albicans genes are negatively regulated by the Rfg1p protein and how these impact on virulence. 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.