Ergosterol is the most important membrane sterol in fungal cells and a component not found in the membranes of human cells. We identified the ERG6 gene in the AIDS-associated fungal pathogen, Cryptococcus neoformans, encoding the sterol C-24 methyltransferase of fungal ergosterol biosynthesis. In this work, we have explored its relationship with high-temperature growth and virulence of C. neoformans by the construction of a loss-of-function mutant. In contrast to other genes involved in ergosterol biosynthesis, C. neoformans ERG6 is not essential for growth under permissive conditions in vitro. However, the erg6 mutant displayed impaired thermotolerance and increased susceptibility to osmotic and oxidative stress, as well as to different antifungal drugs. Total lipid analysis demonstrated a decrease in the erg6Δ strain membrane ergosterol content. In addition, this mutant strain was avirulent in an invertebrate model of C. neoformans infection. C. neoformans Erg6 was cyto-localized in the endoplasmic reticulum and Golgi complex. Our results demonstrate that Erg6 is crucial for growth at high temperature and virulence, likely due to its effects on C. neoformans membrane integrity and dynamics. These pathogen-focused investigations into ergosterol biosynthetic pathway components reinforce the multiple roles of ergosterol in the response of diverse fungal species to alterations in the environment, especially that of the infected host. These studies open perspectives to understand the participation of ergosterol in mechanism of resistance to azole and polyene drugs. Observed synergistic growth defects with co-inhibition of Erg6 and other components of the ergosterol biosynthesis pathway suggests novel approaches to treatment in human fungal infections.

中文翻译：

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Erg6 影响人类真菌病原体新型隐球菌的膜组成和毒力。

麦角甾醇是真菌细胞中最重要的膜甾醇，也是人体细胞膜中没有的成分。我们在艾滋病相关真菌病原体新型隐球菌中鉴定了 ERG6 基因，该基因编码真菌麦角甾醇生物合成的甾醇 C-24 甲基转移酶。在这项工作中，我们通过构建功能丧失突变体，探索了其与新型隐球菌的高温生长和毒力的关系。与麦角甾醇生物合成中涉及的其他基因相比，新型隐球菌 ERG6 在体外允许条件下的生长不是必需的。然而，erg6 突变体表现出耐热性受损和对渗透和氧化应激以及不同抗真菌药物的敏感性增加。总脂质分析表明 erg6Δ 菌株膜麦角甾醇含量降低。此外，该突变株在新型隐球菌感染的无脊椎动物模型中是无毒的。新型隐球菌 Erg6 位于细胞内质网和高尔基复合体中。我们的结果表明，Erg6 对高温和毒力的生长至关重要，这可能是由于其对新型隐球菌膜完整性和动力学的影响。这些针对麦角甾醇生物合成途径组分的病原体研究加强了麦角甾醇在不同真菌物种对环境变化的反应中的多重作用，尤其是受感染宿主的环境变化。这些研究为了解麦角甾醇在唑类和多烯类药物耐药机制中的作用开辟了新的视角。