Title:
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Investigation of YAP1 localisation and dynamics in tumour cell biology
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The complexity of the cancer is created by the fine interplay between cancer cells and their microenvironment. Cancer cells interact with various stromal cell types and extracellular matrix components during tumour growth and development of metastasis. Many signalling pathways influence the cross talk between cancer cells and their environment. For example, YAP1/TAZ signalling has already been shown to be an important determinant of cancer progression in both cancer and stromal cells. Nuclear YAP1 drives transcription but little is known about the dynamics and regulation of YAP1 protein shuttling in and out of nucleus. Furthermore, so far there is no method activating YAP1 signalling specifically in a subset of tumour or stromal cells. I used several approaches to address these outstanding questions in YAP1 biology. Imaging of migrating fibroblasts revealed the tight temporal coupling of cell shape change and YAP1 localization. With the help of high throughput screening and follow up in-depth hit characterisation, I identified exportin 1 (XPO1/CRM1) as the main export factor of YAP1 in human and murine cells. I showed that even upon knockdown of XPO1 nuclear YAP1 remains subject to actomyosin and Src-family kinase regulation. In a similar screen investigating molecular motors I identified DYNLL1 and KLC1 microtubule motors as regulators of YAP1 cytoplasmic stability and mRNA transcript. I also demonstrated DYNLL1 and KLC1 importance in functionality of cancer associated fibroblasts, independently of the effect on YAP1. Finally, I developed an optogenetic approach to specifically modulate nucleocytoplasmic shuttling with single cell resolution. I described opto-release system where I modulate YAP1/TAZ signalling by translocation of YAP1 or TAZ into the nucleus with light. Opto-release tool is used alongside mathematical modelling to study YAP1/TAZ protein dynamics and nucleocytoplasmic shuttling. The results suggest faster nucleocytoplasmic shuttling of TAZ protein in comparison to YAP1, and indicate potential importance of this protein in regulation of keratinocyte biology. Overall, the results presented in this thesis improve current knowledge of YAP1/TAZ signalling in cell biology.
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