The behaviour of cells is determined by how they interpret their genetic and epigenetic programming in the context of signals from their surroundings. These environmental cues are often chemical, but recent work has shown the importance of mechanical stimulation in driving responses to cell morphology, metabolism, motility, proliferation and commitment to lineage. Cells sense the mechanical properties of their environment through integrin adhesion receptors that bind and pull against components of the extracellular matrix (ECM). The modulated response to ECM stiffness, and its maintenance at the appropriate level, is essential for tissue health. In the context of development and repair, stem cells can be directed towards tissue-specific lineages. Mesenchymal stem cells (MSCs) can be directed towards adipogenesis in soft environments, or towards chondro- or osteogenesis in stiff environments, and have been widely studied due to their potential for applications in regenerative medicine. The ECM is also central to many disease processes, and the aberrantly stiff, fibrotic environment of many cancers has been shown to contribute to uncontrolled cellular proliferation and metastatic processes. In pancreatic cancer, for example, the ECM produced by pancreatic fibroblasts (PFs) is an order of magnitude stiffer than the healthy tissue.
Cells respond to physical stimuli, such as stiffness, through mechano-transduction pathways that convert mechanical to biochemical signals. Many of the proteins involved with these processes, such as components of the integrin adhesion complex (IAC) at the cell/ECM interface or the linker of nucleo- and cytoskeleton (LINC) complex at the nuclear membrane, have been identified and characterised. However, these complexes have generally been studied as discrete entities. We lack a holistic picture of how mechanical signals are carried from the ECM through to the nucleus, where distinct genetic programmes can be modulated. Here we propose to use proximity biotinylation mass spectrometry (BioID-MS) to systematically identify the protein linkages that enable communication between cellular regulatory machinery and cellular environments with distinct mechanical properties. BioID-MS enables protein interactions to be identified by selectively tagging proteins proximal to a ‘bait’. By engineering a library of bait constructs for structural and signalling components of IACs and LINC complexes, we will develop a quantitative, global picture of how MSCs and PFs respond to environmental stiffness. By determining how these two complexes are integrated, we intend to identify conserved mechano-transduction pathways, as well as those that may be affected by disease and thus be future targets for intervention. https://www.wellcome-matrix.org/people/martin-humphries/ https://www.wellcome-matrix.org/people/joe-swift/
Applications are invited from UK/EU nationals only. Applicants must have obtained, or be about to obtain, at least an upper second class honours degree (or equivalent) in a relevant subject.
Horton, E.R., Byron, A., Askari, J.A., Ng, D.H.J., Millon-Frémillon, A., Robertson, J., Koper, E.J., Paul, N.R., Warwood, S., Knight, D., Humphries, J.D. and Humphries, M.J. (2015) Definition of a consensus integrin adhesome and its dynamics during adhesion complex assembly and disassembly. Nature Cell Biol. 17: 1577-1587
Ajeian, J.N., Horton, E.R., Astudillo, P., Byron, A., Askari, J.A., Millon-Frémillon, A., Knight, D., Kimber, S.J., Humphries, M.J. and Humphries, J.D. (2016) Proteomic analysis of integrin-associated complexes from mesenchymal stem cells. Proteomics Clin. Appl. 10: 51-57
Horton, E.R., Astudillo, P., Humphries, M.J. and Humphries, J.D. (2016) Mechanosensitivity of integrin adhesion complexes: role of the consensus adhesome. Exp. Cell Res. 343: 7-13
Swift, J., Ivanovska, I.L., Buxboim, A., Harada, T., Dingal, P.C.D.P, Pinter, J., Pajerowski, J.D., Spinler, K.R., Shin, J.-W., Tewari, M., Rehfeldt, F., Speicher, D.W. and Discher, D.E. (2013) Nuclear lamin-A scales with tissue stiffness and enhances matrix-directed differentiation. Science 341: 1240104