Regulatory Circuits that Link Cell Fate and Virulence in Histoplasma Capsulatum

描述（由申请人提供）：荚膜组织胞浆菌是几种系统性二型真菌病原体之一，其生长程序从土壤中的感染性霉菌形式转变为哺乳动物宿主中的致病性酵母形式。H.仅在美国每年就有多达50万例感染，使其成为健康宿主中真菌呼吸道感染的最常见原因。当土壤被破坏，促进菌丝碎片或孢子被人类吸入时，就会发生感染。菌丝和酵母形态之间的形态转换对疾病的建立和维持至关重要。孢子和菌丝碎片是主要的感染因子;然而，一旦引入宿主，病原体转化为芽殖酵母形式，其在宿主巨噬细胞内存活和复制。在实验室中，感染和寄生状态之间的转换是通过改变温度来模拟的：细胞在室温下以丝状形式生长，而在37 ℃下的生长足以引发酵母形式的生长和毒力因子的表达。Beyhan-Pelvan博士的长期研究目标是了解H。荚膜细胞感知宿主温度并激活细胞形态和毒力所需基因的表达。尽管它对人类健康的重要性，很少有人知道如何H。capsulatum感知并响应人体温度。Beyhan-Pelvan博士先前的研究发现对理解H。她发现，四个转录调节因子Ryp 1，2，3，4是温度响应交叉调控网络的核心组成部分。在这个项目的指导阶段，Beyhan-Pelvan博士的目标是利用她以前的工作发现来鉴定和表征H。荚膜具体而言，将测试Ryp蛋白的下游靶标在发病机制中的作用。这些研究也将作为Beyhan-Pelvan博士学习巨噬细胞和小鼠感染技术的培训机会。在该奖项的独立阶段，Beyhan-Pelvan博士的目标是研究调节Ryp蛋白响应宿主温度的因素。这些研究将提供有关细胞如何感知温度并在宿主中开启适当毒力途径的基本信息。这项工作的结果可用于研究其他热二型真菌如何响应宿主温度转变为致病形式。最终，从该项目中获得的信息可用于开发H。capsulatum感染，并有助于防止其他二型真菌感染。Beyhan-Pelvan博士长期以来一直对研究微生物用于感知和响应环境线索以调节重要生物过程（即细胞形态，生物膜形成，运动性或毒性的调节）的分子机制感兴趣。该项目旨在补充她的研究兴趣，并为她提供毒力研究所需的培训。Sil博士的实验室提供了一个独特的机会来学习研究H。荚膜的发病机制和生理机制。Sil博士提供资金和支持人员，以培训Beyhan-Pelvan博士在巨噬细胞和小鼠感染H。荚膜此外，作为导师，Sil博士将与Beyhan-Pelvan博士密切合作，为她的学术求职做好准备。此外，共同导师约翰逊博士和咨询委员会成员恩格尔博士、马德哈尼博士和考克斯博士将提供额外的指导，重点是为求职做准备，并确保在一流研究型大学获得终身助理教授职位。

DESCRIPTION (provided by applicant): Histoplasma capsulatum is one of several systemic dimorphic fungal pathogens that switch their growth program from an infectious mold form in the soil to a pathogenic yeast form in mammalian hosts. H. capsulatum causes up to 500,000 infections per year in the U.S. alone, making it the most common cause of fungal respiratory infections in healthy hosts. Infection occurs when the soil is disrupted, facilitating dispersion o hyphal fragments or spores that are inhaled by humans. The morphologic switch between the hyphal and yeast forms is critical to the establishment and maintenance of disease. Spores and hyphal fragments are the primary infectious agents; however, once introduced into the host, the pathogen converts to a budding-yeast form, which survives and replicates within host macrophages. In the laboratory, the switch between the infectious and parasitic states is modeled by changing the temperature: cells grow in the filamentous form at room temperature, whereas growth at 37�C is sufficient to trigger growth in the yeast form and expression of virulence factors. The long-term research goal of Dr. Beyhan-Pelvan is to understand how H. capsulatum cells sense host temperature and activate the expression of genes required for cell morphology and virulence. Despite its importance to human health, very little is known about how H. capsulatum senses and responds to human body temperature. Dr. Beyhan-Pelvan's prior research findings significantly contributed to the understanding of the molecular mechanism used by H. capsulatum to regulate cell morphology and virulence gene expression: she found that four transcriptional regulators, Ryp1,2,3,4, are the core components of a temperature-responsive intersecting regulatory network. In the mentored phase of this project, Dr. Beyhan-Pelvan aims to use findings from her previous work to identify and characterize novel virulence factors of H. capsulatum. Specifically, downstream targets of the Ryp proteins will be tested for their role in pathogenesis. These studies will also serve as a training opportunity for Dr. Beyhan-Pelvan to learn macrophage and mouse infection techniques. During the independent phase of this award, Dr. Beyhan-Pelvan aims to investigate factors that regulate Ryp proteins in response to host temperature. These studies will provide fundamental information on how cells sense temperature and turn on the appropriate virulence pathways in the host. Findings from this work can be used to investigate how other thermally dimorphic fungi can transition into a pathogenic form in response to host temperature. Ultimately, the information obtained from this project can be used to develop therapeutics for H. capsulatum infections and help prevent other dimorphic fungal infections. Dr. Beyhan-Pelvan has a longstanding interest in studying the molecular mechanisms used by microorganisms to sense and respond to environmental cues to regulate important biological processes (i.e. regulation of cell morphology, biofilm formation, motility or virulence). This project is proposed to complement her research interests and provide her with the required training in virulence studies. Dr. Sil's laboratory provides a unique opportunity to learn experimental techniques required to study both H. capsulatum's pathogenesis and physiology. Dr. Sil offers both funds and support staff to train Dr. Beyhan-Pelvan in macrophage and mouse infections with H. capsulatum. Additionally, as a mentor, Dr. Sil will work closely with Dr. Beyhan-Pelvan to prepare her for academic job searches. Furthermore, co-mentor Dr. Johnson and advisory committee members Drs. Engel, Madhani and Cox, who have facilitated transition of numerous post-doctoral trainees into independent investigators, will provide additional mentoring with emphasis on preparation for job searches and securing a tenure-track assistant professor position in a top-tier research university.