Yoo Kyungyoon, Oliveira Natalia Kronbauer, Bhattacharya Somanon, Fries Bettina C
bioRxiv. 2024 Mar 26:2024.03.26.586817. doi: 10.1101/2024.03.26.586817.
( ) is an opportunistic fungal microorganism that causes life-threatening meningoencephalitis. During the infection, the microbial population is heterogeneously composed of cells with varying generational ages, with older cells accumulating during chronic infections. This is attributed to their enhanced resistance to phagocytic killing and tolerance of antifungals like fluconazole (FLC). In this study, we investigated the role of ergosterol synthesis, ATP-binding cassette (ABC) transporters, and mitochondrial metabolism in the regulation of age-dependent FLC tolerance. We find that old cells increase the production of ergosterol and exhibit upregulation of ABC transporters. Old cells also show transcriptional and phenotypic characteristics consistent with increased metabolic activity, leading to increased ATP production. This is accompanied by increased production of reactive oxygen species (ROS), which results in mitochondrial fragmentation. This study demonstrates that the metabolic changes occurring in the mitochondria of old cells drive the increase in ergosterol synthesis and the upregulation of ABC transporters, leading to FLC tolerance.
Infections caused by cause more than 180,000 deaths annually. Estimated one-year mortality for patients receiving care ranges from 20% in developed countries to 70% in developing countries, suggesting that current treatments are inadequate. Some fungal cells can persist and replicate despite the usage of current antifungal regimens, leading to death or treatment failure. In replicative aging, older cells display a resilient phenotype, characterized by their enhanced tolerance against antifungals and resistance to killing by host cells. This study shows that age-dependent increase in mitochondrial reactive oxygen species drive changes in ABC transporters and ergosterol synthesis, ultimately leading to the heightened tolerance against fluconazole in old cells. Understanding the underlying molecular mechanisms of this age-associated antifungal tolerance will enable more targeted antifungal therapies for cryptococcal infections.
（隐球菌）是一种机会性真菌微生物，可引起危及生命的脑膜脑炎。在感染过程中，微生物群体由不同代龄的细胞组成，在慢性感染期间，老龄细胞会不断积累。这归因于它们对吞噬性杀伤的抵抗力增强以及对氟康唑（FLC）等抗真菌药物的耐受性。在本研究中，我们调查了麦角固醇合成、ATP结合盒（ABC）转运蛋白和线粒体代谢在年龄依赖性氟康唑耐受性调节中的作用。我们发现老龄细胞增加了麦角固醇的产生，并表现出ABC转运蛋白的上调。老龄细胞还表现出与代谢活性增加一致的转录和表型特征，导致ATP产生增加。这伴随着活性氧（ROS）产生的增加，进而导致线粒体碎片化。本研究表明，老龄细胞线粒体中发生的代谢变化驱动了麦角固醇合成的增加和ABC转运蛋白的上调，从而导致氟康唑耐受性。
隐球菌引起的感染每年导致超过18万人死亡。接受治疗的患者估计一年死亡率在发达国家为20%，在发展中国家为70%，这表明目前的治疗方法并不充分。尽管使用了目前的抗真菌方案，一些真菌细胞仍能持续存在并复制，导致死亡或治疗失败。在复制性衰老过程中，老龄细胞表现出一种具有弹性的表型，其特征是对抗真菌药物的耐受性增强以及对宿主细胞杀伤的抵抗力增强。本研究表明，线粒体活性氧随年龄增长而增加，驱动了ABC转运蛋白和麦角固醇合成的变化，最终导致老龄隐球菌细胞对氟康唑的耐受性增强。了解这种与年龄相关的抗真菌耐受性的潜在分子机制，将有助于为隐球菌感染开发更具针对性的抗真菌疗法。
