The link between dimorphism and virulence in Cryptococcus

描述（由申请人提供）：本提案旨在鉴定和表征新型隐球菌真菌中可作为降低其致病性靶标的因子。隐球菌是一种二态真菌：当它呈酵母状时通常会引起疾病，当它呈丝状时（假菌丝或菌丝）毒性较弱。由于根据宿主信号调节生长形式的能力是许多真核微生物引起疾病的必要条件，激活适当的调节回路进行发育可能对隐球菌在宿主条件下的生存和繁殖至关重要。不幸的是，潜伏在隐球菌二态性和毒力之间的分子基础仍然是一个谜。隐球菌的成丝一直被认为是与交配相结合的，而交配在宿主条件下被抑制。在申请人实验室进行的初步研究表明，基因操作可以在与宿主生理相关的条件下赋予隐球菌丝状生长。锌指转录因子Znf2是丝化的主要调节因子，它也决定细胞粘附（絮凝）。重要的是，Znf2对隐球菌致病性有负面影响。因此，Znf2为了解隐球菌二态性和毒力的分子基础提供了一个链接。该提议的中心假设是Znf2通过控制细胞形态型和其他通常与形态发生相关的特征介导隐球菌引起疾病的能力。在强有力的初步数据的指导下，假设将通过追求以下具体目标进行检验：1)。建立ZNF2表达、成丝能力、细胞粘附能力和隐球菌毒力之间的关系。2)。表征成丝和Znf2靶点的其他决定因素，并确定它们在毒力中的作用。为了理解隐球菌的二态性和毒力，研究人员将重点放在了调节固有丝化能力的因素上，这与目前以导致交配的信号通路为中心的研究方法有很大的不同。基于这一新愿景的研究有望产生对隐球菌新毒力决定因素的机制见解。考虑到隐球菌与其他环境获得性二态病原体（不同门）的差异，这些病原体也显示出丝状和毒力之间类似的负相关，本研究极有可能确定真菌二态性所需的保守决定因素。隐球菌是一种重要的临床病原体，并且可以进行遗传和分子研究，因此本研究将有助于更广泛地了解细胞形状的决定以及形态对微生物病原体生存的影响。长期目标是了解真菌病原体常见的形态发生和致病性的基本要求，并利用这些知识开发针对侵袭性真菌病的预防和治疗措施。

DESCRIPTION (provided by applicant): This proposal is to identify and characterize factors in the fungus Cryptococcus neoformans that can be used as targets to compromise its pathogenicity. Cryptococcus is a dimorphic fungus: it generally causes diseases when it is in the yeast form and it is less virulent when it is in the filamentous form (pseudohyphae or hyphae). As the ability to regulate growth form in response to host cues is an essential requirement for many eukaryotic microbes to cause diseases, activating appropriate regulatory circuits for development is likely to be critical for the survival and propagation of Cryptococcus under host conditions. Unfortunately, the molecular bases underlying the link between dimorphism and virulence in Cryptococcus remain an enigma. Filamentation in Cryptococcus has historically been considered to be coupled with mating, which is suppressed under host conditions. Preliminary studies performed in the applicant's lab indicate that genetic manipulation can confer Cryptococcus filamentous growth under conditions that are host physiologically relevant. Znf2, a zinc finger transcription factor, is a master regulator of filamentation and it also dictates cell adhesion (flocculation). Importantly, Znf2 negatively impact Cryptococcus pathogenicity. Thus, Znf2 provides a link to understand the molecular bases of dimorphism and virulence in Cryptococcus. The central hypothesis of this proposal is that Znf2 mediates the ability of Cryptococcus to cause disease by controlling cell morphotype and other features normally associated with morphogenesis. Guided by strong preliminary data, the hypothesis will be tested by pursuing the following specific aims: 1). Establish the relationship between ZNF2 expression, the ability to undergo filamentation, cell adhesion, and Cryptococcus virulence. 2). Characterize additional determinants of filamentation and Znf2 targets, and determine their roles in virulence. The focus on factors that regulate the inherent ability to undergo filamentation in order to understand dimorphism and virulence in Cryptococcus represents a substantial departure from current approaches that are centered on the signaling pathways that lead to mating. Research based on this new vision is expected to generate mechanistic insights into novel virulence determinants in Cryptococcus. Given the divergence of Cryptococcus from other environmentally-acquired dimorphic pathogens (different phyla) that also show a similar inverse association between filamentation and virulence, it is highly likely that this research will identify conserved determinants necessary for fungal dimorphism. As Cryptococcus is both a clinically important pathogen and is amenable to genetic and molecular studies, this research will contribute to a broader understanding of cell-shape determination and the impact of morphotype on the survival of microbial pathogens. The long-term goals are to understand the fundamental requirements for morphogenesis and pathogenicity that are common to fungal pathogens, and to harness such knowledge to develop preventative and therapeutic measures against invasive mycoses.