Analysis of Candida albicans NRG1-regulated gene expression in vivo.

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，但也能够入侵身体的几乎每一个部位，并导致感染，特别是在感染艾滋病毒或其他免疫功能受损的宿主中。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，这一观点主要是基于对不能经历这种形态发生转换的白色念珠菌突变株(即CPhl、Efgl、tupl、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，所以不能就这些形态发生变化在毒力中的作用得出明确的结论。为了解决这些问题，我们设计了一个条件突变株，其中丝状生长的负调控因子(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，在动物宿主内感染期间，通过简单地改变在真菌中表达的NRG1的量，可以改变生物的形态转变和毒力：然而，NRG1p是一种已知的全球抑制蛋白，负责抑制许多白色念珠菌基因，而这些基因并不都参与丝化过程。因此，这项建议的目的是通过对直接从受感染的动物组织中分离的真菌细胞进行微阵列分析，研究NRG1过表达如何改变白色念珠菌的全球表达谱。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 particularly in HIV infected or otherwise immunocompromised hosts. 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 (i.e. ?cphl, ?efgl, ?tupl, ?nrgl) unable to undergo this morphogenetic switch: because all of these strains are locked in one or other form, definitive conclusions on the role of these morphogenetic changes in virulence cannot be made. To address these concerns, 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 has revealed that morphological transitions and, perhaps more importantly, the virulence of the organism can be modified during an infection within an animal host by simply altering the amount of NRG1 being expressed in the fungus: Nrg1 p, however, is known to be a global repressor protein responsible for the suppression of numerous C. albicans genes not all of which are involved in the process of filamentation. The aim of this proposal therefore is to examine how the C. albicans global expression profile is altered by NRG1 overexpression by performing microarray analysis of fungal cells isolated directly from infected animal tissues. 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.