PGA52基因对白念珠菌细胞壁组成、结构和致病力的影响及机制研究

The incidence of invasive fungal infection mainly caused by Candida albicans is increasing rapidly, which is a threat to human health and even life. Therefore, it is urgent to discover the key factor of C. albicans and study its effect mechanism of pathogenicity. We previously found that PGA52 gene played a major role in the composition or structure of cell wall glucan and pathogenicity of C. albicans. Up to now, the function of PGA52 gene in C. albicans has not been reported. The molecular mechanism of action on the composition and structure of cell wall and pathogenicity of C. albicans remain to be clarified. In this study, firstly, we are going to evaluate in vivo virulence of PGA52-deleted C. albicans and comprehensively investigate its pathogenicity-related phenotype such as hyphal formation, biofilm formation and so on, for the purpose of determining the effect of PGA52 gene on the pathogenicity and biological phenotype of C. albicans. Secondly, after demonstrating the basic biofunction of PGA52 gene in C. albicans, we will further explore its role in the composition and structure of cell wall, especially the structure of glucan, through analysis methods including HPLC, NMR, GC/MS and so on. Thirdly, we will further research the molecular mechanism of the effect of PGA52 gene on the cell wall and pathogenicity of C. albicans mainly from two aspects which are cell wall integrity signal pathway and host immune response. This project will provide basis for the understanding of pathogenic mechanism of C. albicans.

以白念珠菌为主的侵袭性真菌感染日益严重，对人类健康甚至生命构成威胁，因此，亟需发现白念珠菌的关键分子并研究其在致病过程中的作用机制。前期我们首次发现PGA52基因可能对白念珠菌的致病力和细胞壁葡聚糖的组成或结构具有重要影响。该基因在白念珠菌内的功能尚未被研究报道，其对细胞壁组成、结构和致病力影响的分子机制也有待阐明。本项目拟①评价PGA52基因缺失白念珠菌的致病力，并全面考察其菌丝形成、生物被膜形成等多个致病力相关表型，以确定PGA52基因对白念珠菌致病力及相关生物学表型的影响。②在明确PGA52基因编码蛋白的基本生物学功能基础之上，运用HPLC、NMR、GC/MS等分析手段，明确该基因对细胞壁组成、结构尤其是葡聚糖结构的影响。③从细胞壁完整性相关通路和宿主免疫反应两方面，深入阐明PGA52基因影响白念珠菌细胞壁组成、结构和致病力的分子机制。本项目将为进一步理解白念珠菌的致病机制提供基础。

细胞壁在白念珠菌共栖和致病过程中均发挥了很重要的作用，开展对细胞壁尤其是其主要骨架成分-葡聚糖相关关键分子的发现以及它在致病过程中的作用机制研究，对侵袭性真菌感染的防治具有重要意义。在青年基金的资助下，研究团队不仅完成了PGA52基因缺失菌和回复菌的构建，还成功构建了PGA52相似基因——TOS1基因的缺失菌和回复菌。研究发现PGA52基因缺失后，白念珠菌的菌丝形成能力无明显改变，但生长倍增时间发生迟滞，小鼠体内毒力明显下降。进一步研究还发现PGA52基因缺失菌的细胞壁超微结构也发生明显改变，葡聚糖层厚度增加，对氟康唑的敏感性增加，但对细胞壁抑制剂阿尼芬净的敏感性下降。TOS1基因缺失后，白念珠菌的菌丝形成能力和生长倍增时间均无明显改变，但小鼠体内毒力发生明显下降，细胞壁超微结构也发生改变，葡聚糖层厚度增加，对氟康唑的敏感性增加。机制研究发现PGA52和TOS1基因缺失菌的体内毒力下降可能与其细胞壁超微结构发生改变，导致白念珠菌通过诱导中性粒细胞呼吸爆发而更容易被中性粒细胞识别杀伤相关。本项目研究发现了细胞壁相关基因PGA52和TOS1在白念珠菌致病力的重要作用和影响机制，对其深入研究，有望阐明白念珠菌致病机制，也为抗真菌药物的发现提供潜在的新靶点。在青年基金资助下，本项目已发表SCI论文4篇，影响因子5分以上的2篇，申请发明专利10项，已授权3项。