Interplay between the heat shock response and histidine kinase pathways in the thermally dimorphic fungal pathogen Histoplasma capsulatum

项目摘要 荚膜组织胞浆菌是几种系统性双态真菌病原体之一， 从土壤中的传染性霉菌形式到哺乳动物宿主中的致病性酵母形式的程序。H.浆菌 仅在美国，每年就有多达25，000例危及生命的感染，死亡率高达50%， 健康宿主真菌呼吸道感染的最常见原因。感染发生在土壤 破坏，促进菌丝碎片或孢子的分散，被人类吸入。孢子和菌丝 片段是主要的感染因子;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。在实验室里， 通过改变生长温度来模拟感染和寄生状态：细胞在丝状体中生长， 在室温下，菌丝生长足以引发酵母形式的生长，而在37ºC下， 毒力因子的表达。 尽管它对人类健康的重要性，很少有人知道如何H。囊状细胞感觉和反应 人体温度。我们先前的研究结果大大有助于理解 H.荚膜调节细胞形态和毒力基因表达：我们发现 四个转录调节因子Ryp 1，2，3，4是温度响应交叉的核心成分， 监管网络。在未发表的研究中，我们全面鉴定了Ryp-interacting蛋白， 监管角色。在多种Ryp 2相互作用蛋白中，我们鉴定了一种热休克蛋白， 热休克蛋白90，和两个蛋白质，Ssk 1和Skn 7，预测响应调节域。我们发现热休克蛋白90， Ssk 1和Skn 7在H.荚膜热休克蛋白90在热休克中起关键作用 反应;和反应调节剂与传感器组氨酸激酶一起工作，通常参与传感 环境信号。在这个项目中，我们建议建立在我们以前的研究结果和充分表征 热休克反应和组氨酸激酶途径参与调节Ryp蛋白、细胞 形态学和毒力特性。capsulatum响应宿主温度。这些研究将提供 关于细胞如何感知温度并在宿主中开启适当的毒力途径的基本信息。 最终，从该项目中获得的信息可用于开发H。浆菌 感染，并有助于防止其他二型真菌感染。

Project Summary 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 25,000 life-threatening infections per year in the U.S. alone with up to 50% mortality rate, and is the most common cause of fungal respiratory infections in healthy hosts. Infection occurs when the soil is disrupted, facilitating dispersion of hyphal fragments or spores that are inhaled by humans. 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 growth temperature: cells grow in the filamentous form (hyphal) at room temperature, whereas growth at 37ºC is sufficient to trigger growth in the yeast form and expression of virulence factors. Despite its importance to human health, very little is known about how H. capsulatum senses and responds to human body temperature. Our prior research findings significantly contributed to the understanding of the molecular mechanism used by H. capsulatum to regulate cell morphology and virulence gene expression: we found that four transcriptional regulators, Ryp1,2,3,4, are the core components of a temperature-responsive intersecting regulatory network. In unpublished studies, we comprehensively identified Ryp-interacting proteins with potential regulatory roles. Among the diverse set of Ryp2-interacting proteins, we characterized a heat shock protein, Hsp90, and two proteins, Ssk1 and Skn7, with predicted response regulator domains. We found that Hsp90, Ssk1 and Skn7 regulate yeast phase growth in H. capsulatum. Hsp90 plays a key role in the heat shock response; and response regulators work with sensor histidine kinases and are often involved in sensing environmental signals. In this project, we propose to build upon our previous findings and fully characterize the involvement of the heat shock response and histidine kinase pathways in regulating Ryp proteins, cell morphology and virulence traits in H. capsulatum 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. Ultimately, the information obtained from this project can be used to develop therapeutics for H. capsulatum infections and help prevent other dimorphic fungal infections.