Destruction of the pulmonary epithelium is a major feature of lung diseases caused by the mould pathogen Aspergillus fumigatus. Although it is widely postulated that tissue invasion is governed by fungal proteases, A. fumigatus mutants lacking individual or multiple enzymes remain fully invasive, suggesting a concomitant requirement for other pathogenic activities during host invasion. In this study we discovered, and exploited, a novel, tissue non-invasive, phenotype in A. fumigatus mutants lacking the pH-responsive transcription factor PacC. Our study revealed a novel mode of epithelial entry, occurring in a cell wall-dependent manner prior to protease production, and via the Dectin-1 β-glucan receptor. ΔpacC mutants are defective in both contact-mediated epithelial entry and protease expression, and significantly attenuated for pathogenicity in leukopenic mice. We combined murine infection modelling, in vivo transcriptomics, and in vitro infections of human alveolar epithelia, to delineate two major, and sequentially acting, PacC-dependent processes impacting epithelial integrity in vitro and tissue invasion in the whole animal. We demonstrate that A. fumigatus spores and germlings are internalised by epithelial cells in a contact-, actin-, cell wall- and Dectin-1 dependent manner and ΔpacC mutants, which aberrantly remodel the cell wall during germinative growth, are unable to gain entry into epithelial cells, both in vitro and in vivo. We further show that PacC acts as a global transcriptional regulator of secreted molecules during growth in the leukopenic mammalian lung, and profile the full cohort of secreted gene products expressed during invasive infection. Our study reveals a combinatorial mode of tissue entry dependent upon sequential, and mechanistically distinct, perturbations of the pulmonary epithelium and demonstrates, for the first time a protective role for Dectin-1 blockade in epithelial defences. Infecting ΔpacC mutants are hypersensitive to cell wall-active antifungal agents highlighting the value of PacC signalling as a target for antifungal therapy.

译文

肺上皮的破坏是由霉菌病原体烟曲霉引起的肺部疾病的主要特征。尽管人们普遍认为组织入侵是由真菌蛋白酶控制的,但缺乏单个或多种酶的烟曲霉突变体仍然具有完全的侵入性,这表明在宿主入侵过程中还需要其他致病活动。在这项研究中,我们在缺乏pH响应转录因子PacC的烟曲霉突变体中发现并开发了一种新颖的组织非侵入性表型。我们的研究揭示了一种新的上皮进入模式,在蛋白酶产生之前通过Dectin-1的 β-葡聚糖受体以细胞壁依赖性方式发生。Δ pacc突变体在接触介导的上皮进入和蛋白酶表达中均有缺陷,并且在白细胞减少症小鼠中的致病性显着减弱。我们结合了鼠感染模型,体内转录组学和人肺泡上皮的体外感染,以描述两个主要且依次作用的依赖于PacC的过程,这些过程影响整个动物的上皮完整性和组织侵袭。我们证明烟曲霉孢子和发芽被上皮细胞以接触,肌动蛋白,细胞壁和Dectin-1依赖性方式内在化,并且 Δ pacc突变体在发芽生长过程中异常重塑细胞壁,无法进入上皮细胞,无论是在体外还是体内。我们进一步表明,PacC在白细胞减少的哺乳动物肺的生长过程中充当分泌分子的整体转录调节剂,并描述了侵袭性感染期间表达的分泌基因产物的完整队列。我们的研究揭示了一种组合的组织进入模式,该模式取决于肺上皮的顺序和机械上不同的扰动,并首次证明了Dectin-1阻断在上皮防御中的保护作用。感染 Δ PacC突变体对细胞壁活性抗真菌剂过敏,突出了PacC信号传导作为抗真菌治疗靶标的价值。

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