Orchestration of adhesion signalling networks by the tensins and their impact in cell motility and matrix remodelling.

Tissues in our body consist of a meshwork of fibrillar material and living cells. The cells continuously sense and produce this fibrillar material, the so-called extracellular matrix (ECM), which surrounds the cells and to which they can attach to. Cell-ECM communication is particularly important during regeneration processes that require specific cellular responses to changing ECM environments. Cellular responses include changes in motile behaviour (e.g. closing of wounds) and also active reorganisation of their ECM when forming new functional tissue. Many studies have focused on how cells detect (sense) environmental signals, but we are still far from understanding how these are translated into signals that promote specific cellular responses.

The extracellular environment of cells alters enormously particularly during ageing, injury and certain diseases. For example, the mechanical properties of the ECM influences tumour progression, and stiffening of ECM causes fibrosis (excess of matrix production), which in turn can lead to malfunctioning of the affected tissues. Intriguingly, cells produce and simultaneously respond to these environmental changes. Understanding this process is critically important if we want to get a step closer to treating the roots of diseases and promote regeneration.

Cells sense their environment by grabbing and pulling the neighbouring extracellular fibrillar material using surface proteins called integrins. These integrins not only bind to the environment of the cells but also connect to a skeleton inside the cells (cytoskeleton). This link is not direct but is regulated by components that couple the two. We published a number of manuscripts showing that two of these coupling proteins, called talin and vinculin, are central to sensing environmental changes. They are particularly important for measuring the stiffness of their surroundings and they control cell migration. In this proposal we present important pilot data demonstrating that members of the tensin protein family, which are critical for ECM reorganisation, interact with a variety of adhesion regulatory proteins including talin and vinculin. How these interactions are mediated, and how different tensin family members are linked to the wider network of proteins that couple integrins to the cytoskeleton, is unclear. Additionally, how these different interactions influence cell behaviour and matrix remodelling is unknown. We will address this problem using long-standing expertise in the fields of integrin mediated cell-matrix interactions in combination with the powerful novel methods established in the Ballestrem laboratory.

The proposed research aims are: (i) to identify key interaction partners of tensin; (ii) to determine how interactions between tensin and its binding partners are regulated and how they contribute to tensin recruitment to cell-matrix adhesion sites; (iii) to investigate how tensins, together with their interaction partners, contribute ECM remodelling and cell motility.

To reach our goals, we will an interdisciplinary approach of cutting edge microscopy, biochemisty and molecular biology techniques with the aim to gain a better understanding of mechanisms that are fundamental for the generation of functional tissues. Ultimately, the knowledge gained may lead to the development of new way to prevent diseases (e.g. cancer, fibrosis) and promote regeneration (wound healing).

Cells interact with the extracellular matrix (ECM) through transmembrane adhesion receptors (integrins) that are linked to signalling proteins that regulate cell migration and ECM remodelling/synthesis. Published data suggest that a family of proteins, the tensins, are embedded in a large network of proteins that influence how cells interpret and remodel their ECM. Which proteins tensins interact with and how they transduce signals to and from the ECM is unclear. As these signals affect cell motility and ECM remodelling, our overarching aim is to understand the role of tensin family members in controlling these processes.

Using cutting edge mass spectrometry and a novel mitochondrial targeting system (MTS) that allows visualisation of protein complexes assembled under defined conditions, we will first identify the proteins the tensins associate with. Using MTS, we will then define tensin interaction sites with binding partners and then examine how they contribute to tensin recruitment to cell-matrix adhesions. Pilot data show an interaction between tensin and the mechanosensors talin and vinculin. Based on these data we hypothesise a key role for these associations in the force-dependent maturation of cell-matrix adhesion sites that regulate ECM remodelling and cell movements. We will use advanced fluorescence imaging to investigate how specific interactions contribute to matrix remodelling and cell motility.

Insights from these studies may ultimately lead to the development of new strategies to prevent diverse diseases and promote tissue regeneration.