Regulation of endoplasmic reticulum stress resistance in yeast

在真核细胞中，近三分之一的新合成蛋白质进入内质网(ER)，内质网是一个含有特殊质量控制机制的细胞器，确保新生多肽的正确折叠。不能折叠成正确的构象会导致蛋白质功能丧失和细胞死亡。因此，细胞已经进化出信号通路，对由基因突变或环境侮辱等各种因素引起的内质网错折叠蛋白负荷(ER Stress)的突然增加做出反应。作为对内质网应激的响应，细胞激活未折叠蛋白反应(UPR)。这种进化上保守的应对机制增加了编码蛋白质的基因的表达，这些蛋白质通过改善蛋白质折叠和错误折叠的蛋白质降解来帮助恢复内质网稳态。最近发现，UPR不仅可以被错误折叠的蛋白质激活，还可以通过内质网膜脂组成的变化而激活。这种差异激活的生物学相关性仍然难以捉摸。利用发芽酵母酿酒酵母，可以进行快速和广泛的遗传操作，已经广泛地表征了内质网应激分解和UPR的机制。然而，UPR的作用是其他酵母物种，如病原体白色念珠菌仍然知之甚少。有趣的是，UPR受损的白色念珠菌细胞对抗真菌药物表现出超敏反应，并降低了致病性。结合对酿酒酵母和白色念珠菌的研究，我建议调查UPR如何控制与抗真菌反应和致病性相关的基因表达。我的中心假设是，UPR激活的不同模式部署了一个特定的转录程序，该程序适应ER折叠环境来调节抗真菌耐药性和致病性。我的研究计划的长期目标是确定控制UPR驱动的抗真菌耐药性和致病性的潜在机制。具体来说，我的短期目标是：(1)阐明内质网应激传感器IRE1是如何被抗真菌药物激活的。(2)对白色念珠菌UPR进行界定。(3)确定UPR靶基因在白色念珠菌抗真菌耐药性和致病性中的作用这个项目将发现新的基本的抗真菌耐药性调节机制，以后可以在其他各种微生物中进行研究。我们的研究将有助于建立新的方法来防止病原菌对抗真菌药物的耐药性进化。

In eukaryotic cells, nearly one third of all newly synthetized proteins enter the endoplasmic reticulum (ER), an organelle containing specialized quality control machinery that ensures the proper folding of the nascent peptides. Failure to fold into their proper conformation leads to loss of protein function and cell death. Thus, cells have evolved signaling pathways that respond to sudden increases in the ER misfolded protein burden (ER stress) caused by various factors such as genetic mutations or environmental insults. In response to ER stress, cells activate the unfolded protein response (UPR). This evolutionarily conserved coping mechanism increases the expression of genes encoding proteins that help restore ER homeostasis by improving protein folding and misfolded protein degradation. Recently, it has emerged that the UPR can not only be activated by misfolded proteins, but also by changes in the lipid composition of the ER membrane. The biological relevance of this differential activation remains elusive. The mechanisms of ER stress resolution and UPR have been extensively characterized using the budding yeast Saccharomyces cerevisiae, which allows rapid and extensive genetic manipulations. However, the role of the UPR is other yeast species such as the pathogen Candida albicans remains poorly understood. Interestingly, C. albicans cells with compromised UPR display hypersensitivity to antifungal drugs and reduced pathogenicity. Using a combination of studies in both S. cerevisiae and C. albicans, I propose to investigate how the UPR control gene expression associated with the antifungal response and pathogenicity. My central hypothesis is that the different mode of UPR activation deploys a specific transcriptional program that adapt the ER folding environment to regulate antifungal resistance and pathogenicity. The long-term goal of my research program is to identify the underlying mechanisms that control UPR-driven antifungal resistance and pathogenicity. Specifically, my short-term objectives are to: (1) Elucidate how the ER stress sensor Ire1 is activated by antifungal drugs. (2) Define the C. albicans UPR. (3) Characterize the role of UPR target genes in C. albicans antifungal resistance and pathogenicity This program will uncover new, fundamental regulatory mechanisms for antifungal resistance that can later be investigated in various other microbial organisms. Our study will contribute to establish new approaches to prevent evolution of pathogen resistance to antifungals.