Award details

Dynamics and interaction of cell-polarity landmark proteins and the Cdc42 GTPase module: a systems approach

Reference	BB/K021699/1
Principal Investigator / Supervisor	Professor Kenneth Sawin
Co-Investigators / Co-Supervisors	Professor Andrew Goryachev
Institution	University of Edinburgh
Department	Sch of Biological Sciences
Funding type	Research
Value (£)	657,292
Status	Completed
Type	Research Grant
Start date	01/07/2014
End date	30/06/2017
Duration	36 months

Abstract

Establishment and maintenance of cell polarity are fundamental cellular phenomena directly related to health and disease. Loss of cell polarity is increasingly noted to be associated with neoplasia and cancerous transformation in epithelial organs. Maintenance of polarity is absolutely required for the function of motile immune cells, asymmetric division of stem cells, and growth and regeneration of neurons. Importantly, polarity is frequently lost in response to a variety of cellular stresses, and its recovery requires some form of cellular memory, often referred to as "landmarks". While an understanding of the mechanisms of polarity recovery is absolutely essential for bio-medical applications, it is hindered by the complexity of mammalian cells. Using fission yeast as a model organism, we propose to determine the mechanisms linking the fundamental Cdc42 cell-polarity module with the microtubule-mediated Tea1 polarity landmark. In addition, we will uncover the role of this interaction in the recovery of cell polarity after stress. We will address the issue of Tea1 landmark stability and its control by Tea1 phosphorylation.

Summary

In the process of development from embryo to adult, cells of multicellular organisms undergo transitions from undifferentiated, embryonic-type cells into more specialised differentiated types, such as neurons, epithelial cells and muscle fibres. The term "cell polarity" refers to the ability of many types of cells to acquire an internal structure or architecture that distinguishes, for example, their front from their back, or their top from their bottom. Differentiation of cells into specialised cell types is typically accompanied by changes in cell polarity and cell shape, and these are important for the specific functions of different cell types. Environmental stresses to the cell, such as extreme temperature, changes in oxygen, acidity or toxins, can lead to loss of cell polarity, and this loss is in fact a normal defensive reaction of the cell. However, if cell polarity does not recover back to normal after the stress subsides, the cell may be more likely to eventually undergo a malignant transformation into a rapidly-dividing non-differentiated form that could cause cancer. Therefore, understanding the detailed mechanisms that control the loss of cell polarity in response to stresses, and the subsequent recovery of cell polarity, is very important to succeed in our fight against cancer. However, human cells, and indeed all mammalian cells, are exceedingly complex and difficult to study experimentally. In this project we will use fission yeast, a model laboratory fungus that is much better understood than human cells, and significantly easier to work with, to study how cell polarity is established and re-established after the recovery from environmental stresses In particular, we will focus on two systems that contribute to the regulation of cell polarity. One system involves a protein called Cdc42, which is found in all cells from yeasts to humans and acts as a "switch" on the cell membrane (surface). Regions of the cell membrane where Cdc42 is "switched on" have different properties to regions where Cdc42 is "switched off". These different regions generate signals to the cell interior to control internal cellular architecture, cell movement and growth. A second system involves filaments called microtubules, which are also found in all cells and reach from the cell interior to the cell membrane. Microtubules contribute to cell polarity by delivering various protein factors to the cell membrane, including a protein called Tea1. To date, the Cdc42 system and the Tea1/microtubules system and their associated proteins have been studied only in isolation. However, in our laboratory we have obtained evidence that the two systems are not completely independent, but instead "talk to each other". The goal of our research is to understand the interplay between the Cdc42 system and the Tea1/microtubules system during the establishment of cell polarity and in response to, and recovery from, stress. To achieve this goal we will use a combination of methods, including state-of-the art microscopy, genetics, mathematical modelling, and analysis of signal-dependent chemical modifications of proteins. In spite of the obvious differences between human cells and yeast, the actual detailed mechanisms underlying their biological behaviours are remarkably similar. Therefore, an improved understanding of the regulation of these processes in yeast, a "model organism", will aid in the understanding of comparable processes in human cells. In addition, our work with yeast may also be useful to develop novel strategies to control growth of fungal pathogens that infect humans and economically important crops and animals.

Impact Summary

Who will benefit from this research? How will they benefit from this research? 1. This is a basic-science project that will use fission yeast as a model organism to investigate the interplay between two eukaryotic cell polarity regulation systems, at both mechanistic and systems levels, using a combination of quantitative imaging, molecular genetics, phosphoproteomics, and computational modelling. As such, the primary beneficiaries of project outcomes will be from the international scientific community. Importantly, because of the multidisciplinary nature of the project, beneficiaries will come from diverse groups: 1) Researchers using fungi as model organisms to understand principles of eukaryotic cell development, differentiation and cell cycle control will benefit from conceptual advances made in understanding how cell polarity is established de novo and re-established after recovery from stress. Because fission yeast offers a level of complexity intermediate between budding yeast and filamentous fungi, we our results will bridge research in budding yeast and in complex filamentous fungi, including pathogens. 2) Researchers working on related problems in mammalian cells will also benefit from an improved understanding of general principles controlling cell polarity after stress. 3) Researchers in imaging will benefit from new methods in image analysis developed in the project, e.g. methods for quantifying recruitment of proteins to the plasma membrane during de novo polarity establishment. 4) Researchers doing computational modelling will benefit from new tools generated, which may be applicable to other systems. 5) Researchers interested in post-translational modifications will benefit from our publicly available SILAC phosphoproteomics datasets as they relate to signalling by conserved protein kinases. 2. There will also be several types of beneficiaries outside the immediate academic community. For example, because fungi are economically important pathogens of both plants and animals, applied researchers working on developing novel chemical compounds to suppress growth and proliferation of fungal pathogens will benefit, as they will be able to leverage conceptual advances, datasets and, ultimately, possible novel fungal-specific drug targets identified in the project. In addition, due to the broader relevance of the project to understanding mechanisms related to cell polarity in cancer progression, the international communities of cancer biologists and medical oncologists will benefit, as they will be able to use paradigms emerging from our work as guiding principles in much more complex mammalian cells. Thus, in the long run, our work will benefit both agricultural and medical practitioners developing anti-fungal drugs and therapies. 3. There will also be wider benefits to society in the technology arena, because of the training and professional skills that staff (PDRAs) employed on the proposal will acquire in the course of carrying out multidisciplinary research. The project provides outstanding potential for staff to develop novel cross-disciplinary, quantitative and other skills required in the modern work environment. These will improve their employment potential in diverse sectors. 4. We also envision the potential for beneficiaries in the area of intellectual property. Although this is a basic-science project, specific areas that may lead to intellectual property include software tools for analysis and modelling, as well as methods of imaging of live cells, which could be useful in high-content screening. 5. Finally in the public sphere, results from the project will be of interest in the popular press, due to interest in both modern cell-imaging techniques and the importance of fungi in agricultural, ecological, and medical contexts. Communication of our results and methodologies, through engagement and the media, will raise awareness within the general public.

Committee	Research Committee C (Genes, development and STEM approaches to biology)
Research Topics	Microbiology, Systems Biology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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