白色念珠球菌轉錄因子 Zcf31 對於幾丁聚醣抗性和細胞表面結構之調控

Role of the transcription factor Zcf31 in chitosan resistance and cell surface structure in Candida albicans

陳紀宏(Ji-Hong Chen)

指導教授 ： 林晉玄

國立臺灣大學/生命科學院/生化科技學系/碩士(2020年)

https://doi.org/10.6342/NTU202001981

摘要

白色念珠球菌 (Candida albicans) 為人體常見的伺機性致病真菌，平時與人體保持共生關係，唯人體免疫力低下時，白色念珠球菌會進一步增生並感染人體。在臺灣，白色念珠球菌是醫療照護相關感染 (health care–associated infection) 比例最高的真菌菌種，臨床上仰賴抗真菌藥物對其感染進行治療。然而，抗真菌藥物的廣泛使用驅使白色念珠球菌抗藥性菌株數量上升，因此發展新的抗真菌劑勢在必行。幾丁聚醣 (chitosan) 擁有發展成抗真菌劑的潛力，且對白色念珠球菌展現良好殺菌活性，但其中的抗菌機制尚未研究透徹。為了探討其中機轉，對前人的突變株庫 (mutant library) 篩選結果做進一步研究。結果顯示，相較於白色念珠球菌野生株，zcf31 突變株對幾丁聚醣敏感性明顯上升。幾丁聚醣的施加使白色念珠球菌產生不規則細胞形狀和細胞膜邊界模糊，而模糊情形在 zcf31 突變株細胞壁也可以觀察到。有趣的是，zcf31 突變株展現異常增厚的細胞壁，伴隨對細胞壁干擾劑抗性上升，細胞膜干擾劑抗性下降。透過 RNA-seq 分析，發現六個 mannosyltransferase 基因在 zcf31 突變株中表現量上升，分別在 zcf31 突變株背景下剔除此六個基因，其中 MNN41、MNN42、MNN45、MNN1 或 MNN15 基因的剔除可以部分回復 zcf31 突變株細胞壁厚度或對細胞表面干擾劑的敏感性。綜合以上結果，推測 zcf31 突變株中 mannosyltransferase 基因表現量上升，可能導致細胞壁蛋白質醣基化樣式改變，進而造成異常細胞壁結構和藥劑敏感性變化。

關鍵字

白色念珠球菌 ； 幾丁聚醣 ； ZCF31 ； 細胞壁厚度 ； mannosyltransferase ； MNN41 ； MNN42 ； MNN45 ； MNN1 ； MNN15

並列摘要

Candida albicans is an opportunistic fungal pathogen commonly found in humans. Generally, it maintains a commensal relationship with healthy people. However, decrease in immunity would allow C. albicans to infect the host. In Taiwan, C. albicans caused the most health care–associated infection cases among fungi. Antifungal drugs were therefore widely used against infection, leading to an increasing number of drug-resistant strains. Knowing the need of new therapeutic method, our lab focused on anti-C. albicans mechanism of a potential antifungal agent, chitosan. In continuation of previous mutant library screening results, we showed that compared to C. albicans wild type, zcf31 mutant was more sensitive to chitosan. Treatment of chitosan resulted in irregular cell surface of the C. albicans wild type strain. The damages on cell wall and cell membrane were more severe in zcf31 mutant during chitosan treatment. Interestingly, zcf31 mutant exhibited abnormally thick cell wall, accompanied by increase resistance to cell wall disturbing agents and decrease resistance to cell membrane disturbing agent. RNA-seq analysis revealed that six mannosyltransferase genes were upregulated in zcf31 mutant. Deletion of MNN41, MNN42, MNN45, MNN1 or MNN15 respectively in zcf31 mutant could partially restore cell wall thickness or sensitivity to cell surface agents. Taken together, our results suggested that the upregulation of mannosyltransferase genes in zcf31 mutant probably changed the glycosylation patterns of cell wall proteins, resulting in atypical cell wall structure and alteration of drug or stress sensitivity.

並列關鍵字

Candida albicans ； chitosan ； ZCF31 ； cell wall thickness ； mannosyltransferase ； MNN41 ； MNN42 ； MNN45 ； MNN1 ； MNN15

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