Translational repression & Aspergillus fumigatus virulence

描述（由申请方提供）：机会霉菌烟曲霉感染仍然是血液恶性肿瘤和器官移植患者管理的主要威胁。由于目前的抗真菌治疗无法预防这种疾病的高死亡率，因此需要更多关于真菌途径的信息，这些真菌途径允许这种生物体在宿主环境中茁壮成长。最近的研究表明，A.烟曲霉和其它病原真菌严重依赖未折叠蛋白应答（UPR）进行感染。UPR是对内质网（ER）应激的适应性反应，负责调节ER的蛋白质折叠能力，使其与分泌途径上的需求成比例。在哺乳动物中，UPR的一个重要分支是由eIF 2磷酸化介导的翻译抑制，这是一种在细胞器过载时降低新生蛋白流入ER的途径。我们的初步数据表明，一个类似的途径存在于A。fumigatus，这挑战了真菌UPR信号传导的现有范式。在这个提议中要测试的首要假设是，翻译抑制是A的重要应激反应。烟曲霉，有助于这种生物体的毒力和抗真菌药物的敏感性。第一个目标将使用该途径的突变体来确定eIF 2的磷酸化和翻译抑制对真菌引起感染和抵抗抗真菌药物和其他类型压力的能力的影响。其次，哺乳动物途径的一个重要特征是，在ER稳态中具有关键功能的mRNA的有限子集可以逃脱翻译抑制。因此，第二个目标将使用RNA-seq和多核糖体分级分离来鉴定在ER应激期间显示增加的翻译的mRNA。这项研究的结果有望揭示真菌内质网应激反应的新模式，这可能导致新的策略来对抗A。烟曲霉，和潜在的其他利用UPR致病力的真核病原体。

DESCRIPTION (provided by applicant): Infections with the opportunistic mold Aspergillus fumigatus continue to be a major threat to the management of patients with hematologic malignancies and organ transplants. Since current antifungal therapies are unable to prevent a high rate of mortality for this disease, there is a need for more information on fungal pathways that allow this organism to thrive in the host environment. Recent studies have shown that A. fumigatus, and other pathogenic fungi, rely heavily on the unfolded protein response (UPR) for infection. The UPR is an adaptive response to endoplasmic reticulum (ER) stress, responsible for adjusting the protein folding capacity of the ER in proportion to the demand placed on the secretory pathway. In mammals, an important branch of the UPR is translational repression mediated by eIF2¿ phosphorylation, a pathway that lowers the influx of nascent proteins into the ER when the organelle is overloaded. Our preliminary data demonstrate that an analogous pathway is present in A. fumigatus, which challenges the existing paradigm of fungal UPR signaling. The overarching hypothesis to be tested in this proposal is that translational repression is a vital stress response of A. fumigatus that contributes to the virulence and antifungal drug susceptibility of this organism. The first aim will use mutants of the pathway to determine the impact of eIF2¿ phosphorylation and translational repression on the ability of the fungus to cause infection and to withstand antifungal drugs and other types of stress. Secondly, an important characteristic of the mammalian pathway is that a limited subset of mRNAs with key functions in ER homeostasis can escape translational repression. Thus, a second aim will use RNA-seq and polysome fractionation to identify mRNAs that show increased translation during ER stress. The outcome of this study is expected to uncover a new paradigm for the fungal ER stress response, which could lead to the development of novel strategies to combat infections with A. fumigatus, and potentially other eukaryotic pathogens that exploit the UPR for virulence.