While the folate biosynthetic pathway has provided a rich source of antibacterial, antiprotozoal, and anticancer therapies, it has not yet been exploited to develop uniquely antifungal agents. Although there have been attempts to develop fungal-specific inhibitors of dihydrofolate reductase (DHFR), the protein itself has not been unequivocally validated as essential for fungal growth or virulence. The purpose of this study was to establish dihydrofolate reductase as a valid antifungal target. Using a strain with doxycycline-repressible transcription of DFR1 (P_TETO-DFR1 strain), we were able to demonstrate that Dfr1p is essential for growth in vitro. Furthermore, nutritional supplements of most forms of folate are not sufficient to restore growth when Dfr1p expression is suppressed or when its activity is directly inhibited by methotrexate, indicating that Candida albicans has a limited capacity to acquire or utilize exogenous sources of folate. Finally, the P_TETO-DFR1 strain was rendered avirulent in a mouse model of disseminated candidiasis upon doxycycline treatment. Collectively, these results confirm the validity of targeting dihydrofolate reductase and, by inference, other enzymes in the folate biosynthetic pathway as a strategy to devise new and efficacious therapies to combat life-threatening invasive fungal infections.

中文翻译：

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二氢叶酸还原酶是人类病原性白色念珠菌中抗真菌发育的有效靶标。

叶酸生物合成途径提供了丰富的抗菌，抗原生动物和抗癌疗法来源，但尚未开发出独特的抗真菌剂。尽管已尝试开发二氢叶酸还原酶（DHFR）的真菌特异性抑制剂，但尚未明确确认该蛋白本身对于真菌生长或毒力必不可少。这项研究的目的是建立二氢叶酸还原酶作为有效的抗真菌靶标。使用具有强力霉素_可抑制的DFR1转录的菌株（P _TETO -DFR1菌株），我们能够证明Dfr1p对于体外生长至关重要。此外，当Dfr1p表达被抑制或甲氨蝶呤直接抑制其活性时，大多数形式叶酸的营养补充剂不足以恢复生长，表明白色念珠菌获取或利用外源叶酸来源的能力有限。最后，在强力霉素处理后，在传播的念珠菌病小鼠模型中，将P _TETO -DFR1菌株变成无毒的。总的来说，这些结果证实了靶向二氢叶酸还原酶以及叶酸生物合成途径中其他酶的靶向性的有效性，以此作为制定新的有效疗法来对抗威胁生命的侵袭性真菌感染的策略。