Histoplasma capsulatum (Hc) is a systemic, dimorphic fungal pathogen that affects upwards of 500,000 individuals in the United States annually. Hc grows as a multicellular mold at environmental temperatures; whereas, upon inhalation into a human or other mammalian host, it transforms into a unicellular, pathogenic yeast. This manuscript is focused on characterizing the DNA damage-responsive gene HcDDR48. HcDDR48 was originally isolated via a subtractive DNA library enriched for transcripts enriched in the mold-phase of Hc growth. Upon further analysis we found that HcDDR48 is not just expressed in the mold morphotype, but both growth programs dependent upon the environment. We found that HcDDR48 is involved in oxidative stress response, antifungal drug resistance, and survival within resting and activated macrophages. Growth of ddr48Δ yeasts was severely decreased when exposed to the reactive oxygen species generator paraquat, as compared to wildtype controls. We also found that ddr48Δ yeasts were 2-times more sensitive to the antifungal drugs amphotericin b and ketoconazole. To test HcDDR48s involvement in vivo, we infected resting and activated RAW 264.7 murine macrophages with Hc yeasts and measured yeast survival 24-hours post-infection. We observed a significant decrease in yeast recovery in the ddr48Δ strain compared to wildtype Hc levels. Herein, we demonstrate the importance of maintaining a functional copy of HcDDR48 in order for Hc yeasts to sense and respond to numerous environmental and host-associated stressors.

中文翻译：

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巨噬细胞内的生存，对氧化应激的反应以及对抗真菌药物的耐药性需要组织胞浆荚膜DDR48基因

荚膜组织胞浆菌（Hc）是一种系统性，双态性真菌病原体，每年在美国影响超过500,000个个体。HC在环境温度下会以多细胞霉菌的形式生长；而吸入人或其他哺乳动物宿主后，它会转化为单细胞病原性酵母。该手稿专注于表征DNA损伤反应基因HcDDR48。HcDDR48最初是通过一个DNA消减文库分离的，该文库富含在Hc生长的霉菌阶段富集的转录本。经过进一步分析，我们发现HcDDR48不仅以霉菌的形态表达，而且两种生长程序都取决于环境。我们发现HcDDR48参与氧化应激反应，抗真菌药物耐药性以及静止和活化巨噬细胞的存活。与野生型对照相比，当暴露于活性氧百草枯时，ddr48Δ酵母的生长严重降低。我们还发现ddr48Δ酵母对抗真菌药两性霉素b和酮康唑的敏感性高2倍。为了测试体内HcDDR48的参与，我们用Hc酵母菌感染了静止的和激活的RAW 264.7鼠巨噬细胞，并在感染后24小时测量了酵母的存活率。我们观察到与野生型Hc相比，ddr48Δ菌株的酵母回收率显着降低水平。在本文中，我们证明了维持HcDDR48功能性复制的重要性，以使Hc酵母能够感测和响应众多环境和与宿主相关的应激源。