Regulation of Candida albicans gene expression in response to host environmental stresses

项目摘要/摘要 摘要白色念珠菌是一种主要的人类真菌病原体，可引起多种全身和粘膜病变。 感染。免疫功能受损的个人，包括器官移植接受者、艾滋病患者和癌症 接受化疗的患者极易感染。在宿主环境中，白色念珠菌遇到一种 各种各样的环境胁迫，包括酸性pH、渗透/阳离子、热、氧化、亚硝酸盐、细胞 壁面和细胞膜的应力。而转录和翻译后机制调节C. 白念珠菌的应激反应已经有了很好的特征，但对白念珠菌的作用知之甚少。 翻译机制；考虑到许多有效的抗生素针对细菌翻译 机制方面，这仍然是一条尚未开发和利用的抗真菌开发途径。EIF4F 翻译起始复合体是与mRNAs 5‘CAP结合的重要物质，具有解旋酶活性 解开5‘非翻译区(UTRs)中的复杂二级结构，以促进翻译和 核糖体可及性。我们最近已经证明了真菌特异的白色念珠菌是酵母的直系物 EIF4E结合蛋白Eap1和Caf20作为eIF4F复合体的负调节蛋白，在 在控制氧化和细胞壁/细胞膜应激反应中发挥重要作用。此外，我们还有 研究表明，白念珠菌的两种蛋白都在膜胁迫下下调，orf19.7034( EAP1正向同源同源异构体)在多种应力条件(P- 身体在翻译上是不活跃的细胞室)。利用核糖体图谱，我们最近还 证明了白色念珠菌的形态转变，以及最有可能的额外毒力过程，是 在广泛的全球翻译控制下。基于这一证据和其他研究，我们的假设是 阐明了控制白念珠菌对宿主反应能力的翻译调控机制 环境压力将为识别和表征潜在的抗真菌靶标提供一种新的策略。至 为了解决这一假设，我们计划：1)确定全球白念珠菌的翻译图谱，以响应 各种寄主环境压力条件；我们还将从翻译的角度识别和描述选定的 对白念珠菌应激反应重要的受控靶基因，2)决定eIF4E结合蛋白 而eIF4F复合体的成分控制着白色念珠菌对宿主环境的反应能力 应激，3)决定翻译应激反应机制如何控制白念珠菌的毒力和 用系统性念珠菌病小鼠模型和巨噬细胞/中性粒细胞杀伤和 生存分析。这些研究将提供对全球监管电路和个人的更好理解 控制白念珠菌对宿主环境胁迫条件的翻译反应的因素。最终， 常见真菌特异性翻译因子和/或目标基因对应激反应、毒力和 发病机制可作为开发新的更有效的抗真菌药物的重要靶点。

PROJECT SUMMARY/ABSTRACT Candida albicans is a major human fungal pathogen responsible for a wide variety of systemic and mucosal infections. Immunocompromised individuals, including organ transplant recipients, AIDS patients and cancer patients on chemotherapy are highly susceptible to infection. In the host environment C. albicans encounters a wide variety of environmental stresses, including acidic pH, osmotic/cationic, thermal, oxidative, nitrosative, cell wall and cell membrane stresses. While transcriptional and post-translational mechanisms that mediate C. albicans stress responses have been well-characterized, considerably less is known about the role of translational mechanisms; given that many effective classes of antibiotics target bacterial translation mechanisms, this remains an unexplored and unexploited avenue for antifungal development. The eIF4F translation initiation complex is important for binding to the 5' CAP of mRNAs and contains helicase activity that unwinds complex secondary structures in 5' untranslated regions (UTRs) to promote translation and ribosome accessibility. We have recently demonstrated that fungal-specific C. albicans orthologs of the yeast eIF4E-binding proteins Eap1 and Caf20, which function as negative regulators of the eIF4F complex, play an important role in controlling oxidative and cell wall/cell membrane stress responses. In addition, we have shown that both C. albicans proteins are down-regulated in response to membrane stress and orf19.7034 (the Eap1 ortholog) functions as a key negative regulator of P-body formation under multiple stress conditions (P- bodies are translationally inactive cellular compartments). Using ribosome profiling, we have also recently demonstrated that the C. albicans morphological transition, and most likely additional virulence processes, is under widespread global translational control. Based on this evidence, and additional studies, our hypothesis is that elucidating translational regulatory mechanisms which control the ability of C. albicans to respond to host environmental stresses will provide a new strategy to identify and characterize potential antifungal targets. To address this hypothesis, we plan to: 1) determine the global translational profile of C. albicans in response to a variety of host environmental stress conditions; we will also identify and characterize selected translationally controlled target genes important for C. albicans stress responses, 2) determine how eIF4E-binding proteins and components of the eIF4F complex control the ability of C. albicans to respond to host environmental stresses, 3) determine how translational stress response mechanisms control C. albicans virulence and pathogenicity using both a mouse model of systemic candidiasis and macrophage/neutrophil killing and survival assays. These studies will provide a better understanding of global regulatory circuits and individual factors that control the translational response of C. albicans to host environmental stress conditions. Ultimately, common fungal-specific translation factors and/or target genes important for stress responses, virulence and pathogenesis could serve as important targets for the development of novel and more effective antifungals.