PBF SIGNALLING IN THE REGULATION OF CELL MOTILITY

The co-ordinated movement of cells is an important biological process for the early stages of embryo growth, tissue repair after injury and immune responses to viruses, bacteria and other foreign substances. Its disruption is also linked with the ageing process and with age-related disorders such as long-term, damaging inflammation and the progression of cancers to more aggressive forms. The control of cell movement is highly complex, with messages being sent from the outside of cells to the machinery within the cells that drives it. While many aspects of this regulation are understood, there is still much we don't know.

We have shown that a protein called PBF stimulates cell movement, and modification of PBF is essential for this function. PBF is one of the most highly modified proteins in humans suggesting it is of great importance. Our data now show that PBF has a key role in the regulatory network that links external signals to the cell machinery that drives movement.

Thus, the overall aim of this study is to understand how PBF influences the molecular network that controls cell movement. We will establish how PBF modification affects its function. The effect of PBF on known regulators of cell movement will be investigated. The contribution of PBF to pathways that are known to drive cell movement will be determined. Importantly, the precise effects of modified PBF on the cell machinery that drives movement, as well as the overall process of moving itself, will be determined.

This study will provide a new understanding of how cell movement is regulated, which will in turn increase our knowledge of the many important bodily processes and diseases that rely on it. Understanding the regulation of cell movement is vital to develop new ways to prevent and treat conditions such as inflammatory disease and aggressive cancer.

Cell motility is critical for embryogenesis, wound healing and immune responses. Its disruption is associated with ageing and related disorders such as inflammation and cancer. Regulation of cell motility is complex, with multiple intracellular signalling pathways linking external signals, sensed by cell surface proteins such as receptor tyrosine kinases (RTKs), with the actin cytoskeleton reorganisation that drives cell movement. Rho GTPases are central nodes within this network that regulate actin cytoskeleton dynamics and cellular adhesion.

We have shown that pituitary tumor-transforming gene (PTTG)-binding factor (PBF/PTTG1IP) is an as-yet uncharacterised node in the network that regulates cell motility, co-ordinating cellular signalling cascades, small GTPase activity, cell adhesion and cytoskeletal organisation. PBF is a ubiquitously expressed transmembrane glycoprotein that stimulates cell migration and invasion. Phosphorylation at tyrosine 174 (Y174) mediates PBF function and, induced by RTK and Src signalling, is one of the most common phosphorylation events in the human phosphoproteome.

We will elucidate the critical role of PBF in mediating the molecular network that controls cell motility. The effect of Y174 phosphorylation on PBF will be determined through identification of proteins that interact with PBF-pY174 as a potential SH2 domain binding site. The role of PBF-pY174 in Rho GTPase signalling will be defined through identification of the Rho GTPase(s) regulated by PBF and determining the underlying mechanisms by which PBF modulates their activity. PBF contribution to RTK and Src modulation of Rho GTPase activity will also be delineated. Critically, the precise effects of PBF-pY174 on cell adhesion, actin organisation and cell motility will be determined. These findings will reveal new insights into the regulation of this fundamental biological process, informing the multiple physiological and disease mechanisms that are contingent upon it.

This study will advance our understanding of the regulation of cell motility, a process that has a critical role in human biology throughout life. The findings of this project will reveal new insights into basic mechanisms such as wound healing and immune responses that are dependent on cell motility and deteriorate during ageing. They will also increase our understanding of aberrant cell motility in age-related disorders such as chronic inflammation and cancer progression. This research will therefore create new knowledge that will innovate strategies for healthy ageing, an area of great importance and strategic priority reflective of our ageing society.

Impact will benefit both academic and non-academic stakeholders and is expected to come from several main streams:
1) An increase in the fundamental knowledge of cell motility will result in worldwide academic advancement
2) Through the involvement of research staff and students this research will contribute to the training of highly skilled researchers and improved teaching and learning
3) Translational potential through the identification of novel drug targets will be realised through commercialisation and exploitation, leading to improved health and well-being in the long-term
4) A number of outreach activities will increase public engagement with research

Who will benefit and how?
1) Academic researchers: Research groups both in the UK and globally will benefit from this study. Given the fundamental nature and complex cellular regulation of cell motility our findings will have broad appeal across the wider research community. Cell and molecular biology researchers, particularly those with an interest in cell motility, adhesion, cytoskeleton, small GTPases, wound healing, ageing and cancer, will benefit from the new knowledge that is generated. This will be effectively disseminated through publishing in Open Access journals and presentation at local, national and international meetings, and will result in increased collaboration and research outputs.
2) Students/early career researchers: Clinical and non-clinical students at both undergraduate and postgraduate level will be engaged with this research through ongoing taught and laboratory-based sessions provided by the PI. Students will be exposed to cutting-edge research and experimental techniques, thereby increasing their scientific skills and knowledge of essential processes for health and wellbeing.
3) Research Staff: The postdoctoral researcher and technician will make valuable contributions to this study. In return they will benefit from extensive training in research skills and provided with regular opportunities for professional development.
4) Commercial/private sector: The knowledge generated through this study has the potential to identify new drug targets for the treatment of disorders associated with cell motility, such as inflammation and cancer. Through secondary use of our data and/or overall findings, or through collaboration with our group, pharmaceutical industries would thus benefit.
5) Wider socio-economic impacts: In the long-term the development of effective novel therapeutic strategies would ultimately have a significant impact on the health and wellbeing of patients, enhancing quality of life and reducing pressure on the health and social care systems.
6) Public. We will engage wider non-academic community, communicating research directions and outputs from the study in an accessible way. Members of the public will increase their knowledge of research undertaken through the support of BBSRC and understand its relevance to society.