Gene Circuits that Control Morphology in Histoplasma

描述（由申请人提供）：本研究的长期目标是确定环境信号（如温度）如何调节真菌病原体荚膜组织胞浆菌的形态和毒力。H.荚膜细胞在土壤中以丝状形式生长;一旦被吸入哺乳动物宿主，这些细胞将其生长程序转换为寄生酵母形式，破坏先天免疫系统，导致疾病。在进化上相关的系统性二型真菌病原体（包括H。capsulatum以及选择的病原体如球孢子菌属物种。对于所有这些病原体，温度是调节这种形态发生开关的关键信号，这被认为是H。荚膜毒力通过阐明H. capsulatum细胞的感觉和响应宿主温度，我们将确定关键的分子标志，促进形态的变化，以及毒力性状的表达。这些研究将揭示信号转导和基因调控等基本过程，并揭示温度依赖性途径在真菌致病中的作用。在过去的资助期间，我们确定了第一个转录调节所需的酵母形式的增长，以响应宿主温度。这些因子被命名为Ryp 1、Ryp 2和Ryp 3，与其他真菌中的关键发育调节因子同源，并且代表了H.荚膜有趣的是，在其他真菌中的正向调节因子的精确生物化学功能尚不清楚，从而为我们在H.荚膜我们最近发现，Ryp蛋白与形态和毒力基因的上游区域相关，这表明它们直接调节形态和毒力程序的重要组成部分。此外，这些数据提供了第一个分子证据，形态和毒力因子的转录调控耦合。在这项提议中，我们的具体目标是研究和鉴定（1）温度激活Ryp蛋白的分子机制;（2）Ryp蛋白调节基因表达的机制;（3）位于这些因子下游的依赖于Ryp的调节回路的元件及其对形态学和毒力的影响。综合起来，所得的数据将极大地增强我们对H. capsulatum宿主温度。此外，我们还将获得关于H.宿主中的荚膜致病。 公共卫生相关性：荚膜组织胞浆菌是一种主要病原体，在美国每年感染约500，000人，是免疫功能低下患者发病率和死亡率的重要来源。由于对这种真菌如何引起疾病知之甚少，因此鉴定影响发病机制和操纵宿主免疫反应的真菌因素将显着推进该领域并允许开发新的治疗方法。

DESCRIPTION (provided by applicant): The long-term goal of this research is to determine how environmental signals such as temperature regulate morphology and virulence in the fungal pathogen Histoplasma capsulatum. H. capsulatum grows in a filamentous form in the soil; once inhaled into a mammalian host, these cells switch their growth program to a parasitic yeast form that subverts the innate immune system to cause disease. A similar switch from soil to host form is observed for the evolutionarily related systemic dimorphic fungal pathogens, which include H. capsulatum as well as select agent pathogens such as Coccidioides species. For all of these pathogens, temperature is a key signal that regulates this morphogenetic switch, which is thought to be essential for H. capsulatum virulence. By elucidating how H. capsulatum cells sense and respond to host temperature, we will define critical molecular landmarks that promote changes in morphology as well as the expression of virulence traits. These studies will shed light on fundamental processes such as signal transduction and gene regulation, as well as uncover the role of temperature-dependent pathways in fungal pathogenesis. Over the last funding period, we identified the first transcriptional regulators required for growth in the yeast form in response to host temperature. These factors, named Ryp1, Ryp2, and Ryp3, are homologous to key developmental regulators in other fungi, and represent critical elements of the temperature-dependent regulatory circuit in H. capsulatum. Interestingly, the precise biochemical function of the orthologous regulators in other fungi is unclear, thus adding additional significance to our functional characterization in H. capsulatum. We have recently shown that the Ryp proteins associate with the upstream regions of both morphology and virulence genes, suggesting that they directly regulate essential components of the morphology and virulence programs. Furthermore, these data provide the first molecular evidence that the transcriptional regulation of morphology and virulence factors is coupled. In this proposal, our specific aims are to investigate and identify (1) the molecular mechanism of activation of the Ryp proteins by temperature; (2) the mechanisms by which the Ryp proteins regulate gene expression; and (3) the elements of the Ryp-dependent regulatory circuit that lie downstream of these factors and their effect on morphology and virulence. Taken together, the resultant data will greatly enhance our understanding of the molecular response pathway of H. capsulatum to host temperature. Additionally, we will gain valuable knowledge about individual morphology and virulence factors that are required for H. capsulatum pathogenesis in the host. PUBLIC HEALTH RELEVANCE: Histoplasma capsulatum is a primary pathogen that infects approximately 500,000 individuals per year in the U.S. and is a significant source of morbidity and mortality in immunocompromised patients. Since very little is understood about how this fungus causes disease, the identification of fungal factors that influence pathogenesis and manipulate the host immune response will significantly advance the field and allow for the development of new therapeutics.