Investigating a signaling molecule that cooperates with quorum sensing to induce biofilm formation in C. neoformans

摘要 此探索性R21提案的目标是识别和描述细胞间通信 在人类真菌病原体中与群体感应协同诱导生物膜形成的信号 新生隐球菌。新生隐球菌是一种能引起隐球菌的担子真菌。 脑膜脑炎(CME)是影响患者的最致命和最常见的机会性感染之一 艾滋病毒/艾滋病。像许多其他感染性微生物一样，新生隐球菌会形成类似生物膜的结构，称为 体内的隐球菌瘤。然而，我们对生物膜或其结构要求知之甚少。 这种真菌病原体的遗传调节，部分原因是隐球菌在实验室中不容易形成生物膜 条件，部分是因为该担子菌不携带任何已知的与生物膜相关的同系物 存在于酵母菌和念珠菌等子囊菌中的蛋白质。 在这里，我们发现在交配型a型菌株中转录抑制物SSN6的中断，但在 同源交配型α菌株，导致新生葡萄球菌形成强大的生物膜，这为进入 这为我们研究该真菌生物膜形成的遗传规律提供了依据。有趣的是，SSN6一种生物膜 菌落诱导附近的ssn6α菌落也形成生物膜，这一过程不依赖于交配。 信息素。我们发现激活生物膜形成的细胞间通讯系统 需要群体感应分子Qsp1和一个未知的基于多肽的信号分子。在这里我们 提出(1)鉴定分泌的生物膜信号分子和(2)阐明生物膜的信号转导途径 由这种信号分子激活的形成。这项拟议的工作有望对这一分层结构产生深刻的见解 在临床上重要的真菌中调节这种复杂的群体行为的通信系统 病原体。我们还希望在本研究中发现新的生物膜结构蛋白，如隐球菌中的粘附素 过程，这将填补我们在生物膜形成和调控方面的关键知识空白 担子菌。本次探索性研究的结果也将为今后的研究提供基础 生物被膜调控对隐球菌致病作用的研究。

ABSTRACT The objectives of this exploratory R21 proposal are to identify and characterize an intercellular communication signal that induces biofilm formation in cooperation with quorum sensing in the human fungal pathogen Cryptococcus neoformans. C. neoformans is a basidiomycetous fungus that causes cryptococcal meningoencephalitis (CME), one of the most fatal and common opportunistic infections affecting people with HIV/AIDS. Like many other infectious microbes, C. neoformans forms biofilm-like structures known as cryptococcoma in vivo. However, we know very little about the structural requirements for biofilms or their genetic regulation in this fungal pathogen, partly because Cryptococcus forms biofilms poorly under laboratory conditions, and partly because this basidiomycete does not carry homologues of any known biofilm-relevant proteins established in ascomycetes like Saccharomyces and Candida species. Here we found that disruption of a transcription repressor Ssn6 in a mating-type a strain, but not in the congenic mating-type α strain, leads to robust biofilm formation in C. neoformans, which provides an entry point for us to investigate genetic regulation of biofilm formation in this fungus. Interestingly, ssn6a biofilm colonies induce the nearby ssn6α colonies to also form biofilms and this process is independent of the mating pheromone. We discovered that the intercellular communication system which activates biofilm formation requires the quorum-sensing molecule Qsp1 and an unknown peptide-based signaling molecule. Here we propose to (1) identify the secreted biofilm signaling molecule and (2) elucidate the pathway involved in biofilm formation activated by this signaling molecule. The proposed work is expected to yield insights into this layered communication system that regulates such complex community behaviors in a clinically important fungal pathogen. We also expect to identify novel biofilm structural proteins like adhesins in Cryptococcus in this process, which will fill the critical gap in our knowledge about biofilm formation and regulation in basidiomycetes. The findings from this exploratory research will also provide a foundation for future investigation of the impact of biofilm regulation on cryptococcal pathogenesis.