Novel Aspects of the Response to Cellular Stress and Intracellular Bacterial Pathogens

The cellular stress response represents an essential mechanism that enables cells to adapt to an array of environmental and physiological conditions. Given the importance of these adaptive responses, it comes as no surprise that dysregulation of the stress response has been strongly implicated in various diseases including infection, neurodegenerative diseases, and cancer. The findings presented in this thesis reveal novel aspects of the cellular response elicited by stress stimuli including nutrient starvation, proteotoxic stress and infection by intracellular bacterial pathogens. We first highlight that various components of the machinery responsible for mRNA splicing undergo dynamic reorganization into cytoplasmic granules known as U snRNA (U) bodies during metabolic stress and infection. The formation of U bodies during stress is accompanied by an overall decrease in splicing components, including the U snRNAs that are essential for mRNA splicing. Furthermore, we report global transcriptional reprogramming of a core group of stress-related genes in intestinal epithelial organoids in response to endoplasmic reticulum (ER) stress and nutrient starvation, including transcription factors, chemokines, and genes involved in inflammation. The landscape of alternative splicing (AS) was also strongly affected by cellular stress, and we report the existence of a conserved mechanism to regulate the expression of splicing and RNA processing genes that involves the coupling of AS and nonsense-mediated decay (NMD). Lastly, this thesis underscores the importance of stress response pathways in the maintenance of cellular homeostasis and survival by highlighting a novel role for the natural compound isoginkgetin as an inhibitor of the 26S proteasome. Disruption of protein homeostasis via isoginkgetin impairs the ability of cancer cells to mount stress responses and sensitizes various cancer cell types to apoptotic cell death upon nutrient starvation. Taken together, the results of this research will contribute to the overall understanding of the mechanisms underlying the cellular adaptation to stress and will aid in the development of novel therapeutics for diseases in which critical arms of the stress response are dysregulated.Ph.D.2019-12-19 00:00:0

The transcriptional and splicing landscape of intestinal organoids undergoing nutrient starvation or endoplasmic reticulum stress

Abstract Background The intestinal epithelium plays a critical role in nutrient absorption and innate immune defense. Recent studies showed that metabolic stress pathways, in particular the integrated stress response (ISR), control intestinal epithelial cell fate and function. Here, we used RNA-seq to analyze the global transcript level and alternative splicing responses of primary murine enteroids undergoing two distinct ISR-triggering stresses, endoplasmic reticulum (ER) stress and nutrient starvation. Results Our results reveal the core transcript level response to ISR-associated stress in murine enteroids, which includes induction of stress transcription factors, as well as genes associated with chemotaxis and inflammation. We also identified the transcript expression signatures that are unique to each ISR stress. Among these, we observed that ER stress and nutrient starvation had opposite effects on intestinal stem cell (ISC) transcriptional reprogramming. In agreement, ER stress decreased EdU incorporation, a marker of cell proliferation, in primary murine enteroids, while nutrient starvation had an opposite effect. We also analyzed the impact of these cellular stresses on mRNA splicing regulation. Splicing events commonly regulated by both stresses affected genes regulating splicing and were associated with nonsense-mediated decay (NMD), suggesting that splicing is modulated by an auto-regulatory feedback loop during stress. In addition, we also identified a number of genes displaying stress-specific splicing regulation. We suggest that functional gene expression diversity may arise during stress by the coordination of alternative splicing and alternative translation, and that this diversity might contribute to the cellular response to stress. Conclusions Together, these results provide novel understanding of the importance of metabolic stress pathways in the intestinal epithelium. Specifically, the importance of cellular stresses in the regulation of immune and defense function, metabolism, proliferation and ISC activity in the intestinal epithelium is highlighted. Furthermore, this work highlights an under-appreciated role played by alternative splicing in shaping the response to stress and reveals a potential mechanism for gene regulation involving coupling of AS and alternative translation start sites

Spiraea ogawae Nakai

原著和名: キイシモツケ科名: バラ科 = Rosaceae採集地: 和歌山県 那賀郡 粉河町 竜門山 (紀伊 粉河町 竜門山)採集日: 1981/5/13採集者: 萩庭丈壽整理番号: JH000438国立科学博物館整理番号: TNS-VS-95043

The heme-regulated inhibitor is a cytosolic sensor of protein misfolding that controls innate immune signaling

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