The link between dimorphism and virulence in Cryptococcus

描述(由申请人提供)：这项建议是为了识别和表征新生隐球菌中可用作目标的因素，以降低其致病性。隐球菌是一种二相性真菌：当它以酵母菌的形式存在时，通常会引起疾病，而当它以丝状形式(假菌丝或菌丝)存在时，它的毒性较小。由于响应宿主提示而调节生长形式的能力是许多真核微生物致病的基本要求，因此激活适当的发育调控电路对于隐球菌在宿主条件下的生存和繁殖可能是至关重要的。不幸的是，隐球菌二型性和毒力之间联系的分子基础仍然是一个谜。在历史上，隐球菌丝状化被认为与交配结合，而交配在宿主条件下被抑制。在申请人的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促进隐球菌丝状生长。锌指转录因子--锌指转录因子是丝状化的主要调节因子，也是细胞黏附(絮凝)的调节因子。重要的是，Znf2对隐球菌的致病力有负面影响。因此，Znf2基因为了解隐球菌二型性和毒力的分子基础提供了一个纽带。这一建议的中心假设是，Znf2通过控制细胞形态和其他通常与形态发生相关的特征来介导隐球菌致病的能力。在强劲的初步数据的指导下，将通过追求以下具体目标来检验假设：1)。建立ZNF2的表达、通过丝状化的能力、细胞黏附和隐球菌毒力之间的关系。2)。确定丝状化和znf2靶标的其他决定因素，并确定它们在毒力中的作用。为了了解隐球菌的二形性和毒力，人们关注调节丝化的固有能力的因素，这与目前以导致交配的信号通路为中心的方法有很大的不同。基于这一新愿景的研究有望对隐球菌的新毒力决定因素产生机械性的见解。考虑到隐球菌与其他环境获得的二型性病原体(不同的门)的差异，这些病原体也显示出丝状化和毒力之间类似的反向关联，这项研究很有可能确定真菌二型性所必需的保守决定因素。由于隐球菌既是一种临床上重要的病原体，也是一种可以进行遗传学和分子研究的细菌，本研究将有助于更广泛地了解细胞形态决定和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.