Drug resistance in fungal pathogens has risen steadily over the past decades due to long-term azole therapy or triazole usage in agriculture. Modification of the drug target protein to prevent drug binding is a major recognized route to induce drug resistance. However, mechanisms for nondrug target-induced resistance remain only loosely defined. Here, we explore the molecular mechanisms of multidrug resistance resulted from an efficient adaptation strategy for survival in drug environments in the human pathogen Aspergillus fumigatus We show that mutants conferring multidrug resistance are linked with mitochondrial dysfunction induced by defects in heme A biosynthesis. Comparison of the gene expression profiles between the drug-resistant mutants and the parental wild-type strain shows that multidrug-resistant transporters, chitin synthases, and calcium-signaling-related genes are significantly up-regulated, while scavenging mitochondrial reactive oxygen species (ROS)-related genes are significantly down-regulated. The up-regulated-expression genes share consensus calcium-dependent serine threonine phosphatase-dependent response elements (the binding sites of calcium-signaling transcription factor CrzA). Accordingly, drug-resistant mutants show enhanced cytosolic Ca2+ transients and persistent nuclear localization of CrzA. In comparison, calcium chelators significantly restore drug susceptibility and increase azole efficacy either in laboratory-derived or in clinic-isolated A. fumigatus strains. Thus, the mitochondrial dysfunction as a fitness cost can trigger calcium signaling and, therefore, globally up-regulate a series of embedding calcineurin-dependent-response-element genes, leading to antifungal resistance. These findings illuminate how fitness cost affects drug resistance and suggest that disruption of calcium signaling might be a promising therapeutic strategy to fight against nondrug target-induced drug resistance.

中文翻译：

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线粒体功能障碍触发了钙信号依赖性真菌多药耐药性。

在过去的几十年中，由于长期使用唑类药物或在农业中使用三唑类，真菌病原体的耐药性一直在稳步上升。修饰药物靶蛋白以防止药物结合是诱导耐药性的主要公认途径。但是，非药物靶标诱导的耐药性的机制仍然很松散。在这里，我们探讨了一种有效的适应策略，在人类病原体烟曲霉中的药物生存环境中，产生了多重耐药性的分子机制。我们显示，赋予多重耐药性的突变体与血红素A生物合成缺陷所致的线粒体功能障碍有关。耐药突变体与亲本野生型菌株之间的基因表达谱比较表明，多药耐药转运蛋白，几丁质合酶，钙信号相关基因显着上调，而清除线粒体活性氧（ROS）相关基因则显着下调。上调表达的基因共有共识钙依赖性丝氨酸苏氨酸磷酸酶依赖性反应元件（钙信号转录因子CrzA的结合位点）。因此，耐药突变体显示出增强的胞质Ca2 +瞬变和CrzA的持久核定位。相比之下，无论是实验室来源的还是临床分离的烟曲霉菌株，钙螯合剂都能显着恢复药物敏感性，并提高唑的功效。因此，线粒体功能障碍作为健身成本可以触发钙信号传导，因此，全局上调了一系列嵌入钙调神经磷酸酶依赖性反应元件的基因，导致抗真菌性。这些发现阐明了健身成本如何影响耐药性，并暗示了破坏钙信号传导可能是对抗非药物靶标诱导的耐药性的有前途的治疗策略。