The molecular basis of crosstalk between integrin-mediated cell-matrix adhesions and the microtubule network.

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All cells in the human body are held in the correct place via adhesion to neighbouring cells, and to a dense meshwork of proteins that surround cells called the extracellular matrix (ECM). Cell attachment to the ECM is important for cell proliferation, survival and migration during embryonic development, and in adult organisms for processes such as blood clotting and wound healing. Cell-matrix adhesion is mediated by a family of proteins, the integrins, that are found on the cells surface that act as receptors that grab hold of ECM proteins.Integrins are organised into specialised structures called focal adhesions (FAs) - sticky feet - and cell migration requires the coordinated assembly and disassembly of FAs coupled to force exerted by the cells contractile machinery which enables the cell to pull itself forwards. While cell migration is essential for the development of multicellular organisms, it must be tightly controlled - cancer metastasis is a product of uncontrolled cell migration. From our previous research and that of other laboratories, the assembly of FAs is now fairly well understood, and an intracellular protein called talin has been shown to be essential for FA assembly as it binds to integrins and couples them to the cells' contractile machinery. However, the mechanisms underlying the disassembly of FAs are less clear. It is now well recognised that recruitment of intracellular structures called microtubules to FAs enhances their turnover and increases the speed at which cells migrate, but what directs microtubules to FAs has remained elusive. Excitingly, we have discovered a novel link between talin and a protein called Kank1 that is involved in stabilising microtubules. The hypothesis that we would like to test is that the interaction between talin and Kank1 directs microtubules to adhesion sites and in doing so leads to FA disassembly and consequently increased cell migration.Drugs that disrupt microtubules are commonly used to kill cancer cells, but have severe side effects because they also kill normal cells. However, if we can leave the microtubule network intact, but specifically prevent microtubule recruitment to FAs, this should inhibit FA turnover and suppress cell migration, and therefore offer a new way to treat cancer metastasis. Until we characterise how the talin:Kank1 interaction works, and determine the precise atomic structure of the binding sites where this linkage is made, we cannot design drugs to prevent the talin-dependent recruitment of microtubules to FAs that enhances the invasiveness of cancer cells. The Aim of this project is to establish how talin and Kank1 interact so as to design mutations in the Kank1 binding site that prevent the interaction. We will use a combination of biochemical and structural approaches to obtain this information, approaches that are well established in the applicant's laboratory. The effect of such mutations on cell migration will then be tested in collaboration with Prof. Anna Akhmanova (Utrecht).Ultimately this study could lead to the identification of new strategies for the design and development of drugs that inhibit microtubule recruitment to adhesion sites, and thus prevent cancer growth and spread in humans.