棘阿米巴角膜炎是一種由致病性棘阿米巴經由角膜損傷處感染角膜的眼部疾病。由於缺乏專一性藥物的發展，臨床上對於原蟲感染多半使用廣效性抗生素或消毒劑。聚六亞甲基雙胍 (Polyhexamethylene biguanide, PHMB) 是一種廣效性殺菌劑，為目前治療棘阿米巴角膜炎臨床用藥，但抗藥性蟲株的出現使得此類疾病並非每次都能夠順利治癒，因此針對其抗藥性機制研究，進而開發專一性藥物勢必為重要之議題。本研究結果顯示，抗性較強之本土臨床分離株NCKH_D在施予PHMB後，其雙硫鍵異構酶蛋白 (disulfideisomerase domain containing protein, PDI) 基因四個同分異構物中的ACA1_189420表現量會大幅提升。經由序列分析及分子生物學實驗，我們證明PDI的功能如同其他生物中的硫氧還蛋白 (Thioredoxin, Trx)，在表現量提升時能影響棘阿米巴核糖核苷酸還原酶 (Ribonucleotide reductase, RNR) 的表現，進而干擾DNA複製使得細胞週期停滯。最重要的是，在抗藥性蟲株的PDI表現受抑制時，PHMB的毒殺效果確實有明顯的提升。總結以上結果，本論文證實PDI在棘阿米巴之抗藥機制中的重要性，並進一步釐清PDI於棘阿米巴中相關的訊息傳導路徑。

In this study, we found that disulfideisomerase domain containing protein (PDI) ACA1_189420 is up-regulated by PHMB treatment in Acanthamoeba castellanii NCKH_D, a highly PHMB-tolerant strain. Furthermore, PDI affects the expression level of Ribonucleotide reductase (RNR) and DNA replication in Acanthamoeba as the role of Thioredoxin (Trx) in mammalian cell. NCKH_D was vulnerable to PHMB after PDI-specific siRNA silencing, which proved the relationship between PDI and drug tolerance. These results show that PDI is an important gene for drug tolerance ability in PHMB-tolerant Acanthamoeba. In addition, we also revealed the PDI signaling transduction in Acanthamoeba.

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