Regulatory circuits that link cell fate and virulence in Histoplasma capsulatum

描述(由申请人提供)：组织胞浆菌是几种系统性二相性真菌病原体之一，它们的生长程序在哺乳动物宿主中从具有感染性的霉菌形态转变为致病的酵母形态。仅在美国，每年就有多达50万人感染囊状杆菌，使其成为健康宿主中最常见的真菌呼吸道感染原因。当土壤被破坏时，就会发生感染，从而促进人类吸入的菌丝碎片或孢子的扩散。菌丝体和酵母菌之间的形态转换对疾病的建立和维持至关重要。孢子和菌丝片段是主要的感染源；然而，一旦进入宿主，病原体就会转化为萌芽酵母形式，在宿主巨噬细胞内存活和复制。在实验室中，通过改变温度来模拟感染和寄生状态之间的切换：细胞在室温下以丝状形式生长，而在37℃下生长足以触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囊状芽孢杆菌细胞如何感知宿主温度，并激活细胞形态和毒力所需基因的表达。尽管它对人类健康很重要，但人们对它的感知和对人体体温的反应知之甚少。Beyhan-Pelvan博士之前的研究成果极大地促进了人们对胶囊杆菌调控细胞形态和毒力基因表达的分子机制的理解：她发现，四种转录调控因子Ryp1、2、3、4是温度敏感型交叉调控网络的核心组成部分。在该项目的指导阶段，Beyhan-Pelvan博士的目标是利用她之前工作的发现来识别和表征胶囊H.atum新的毒力因素。具体地说，Ryp蛋白的下游靶标将被测试它们在发病机制中的作用。这些研究也将成为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蛋白对宿主温度做出反应的因素。这些研究将提供有关细胞如何感知温度和启动宿主中适当的毒力途径的基本信息。这项工作的发现可以用来研究其他热二型真菌如何对宿主温度做出反应而转变为致病形式。最终，从这个项目中获得的信息可以用来开发治疗包膜螺旋体感染的方法，并帮助预防其他二相性真菌感染。Beyhan-Pelvan博士长期以来一直感兴趣的是研究微生物用来感知和响应环境线索的分子机制，以调节重要的生物过程(即调节细胞形态、生物膜形成、运动性或毒力)。这个项目是为了补充她的研究兴趣，并为她提供毒力研究方面所需的培训。西尔博士的实验室提供了一个独特的学习实验技术的机会，这些技术是研究囊状螺旋体致病机制和生理学所必需的。西尔博士提供资金和支持人员，为贝汉-佩尔万博士提供巨噬细胞和感染囊状螺旋体的小鼠方面的培训。此外，作为导师，西尔博士将与贝汉-佩尔文博士密切合作，帮助她为学术求职做好准备。此外，共同导师约翰逊博士以及顾问委员会成员恩格尔、马德哈尼和考克斯博士将提供额外的指导，重点是为寻找工作做准备，并在一流研究型大学获得终身教职助理教授的职位。

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.