The Role and Regulation of the Focal Adhesion Network

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Abstract

This abstract is for the thesis entitled ‘The role and regulation of the focal adhesion network’ by Devina Jethwa. The thesis is submitted in 2017 for the degree of Doctor of Philosophy in the Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester. Cells sense and interpret environmental signals to influence a number of cellular processes including migration, proliferation and differentiation. Focal adhesions (FAs) are large integrin based adhesion receptors that link the extracellular matrix to the contractile actin cytoskeleton. Here, FAs can sense mechanical changes of the underlying matrix and translate this information into a cellular response, a process known as mechanotransduction. However, the molecular processes that co-ordinate mechanotransduction are yet to be elucidated. Talin and vinculin are two multidomain proteins that form the core of the FA and are thought to be involved in mechanotransduction. The first results chapter focuses on the force-dependent interactions between talin, vinculin and actin. Talin’s R2R3 domains were identified as key mechanosensitive vinculin binding sites that are exposed upon the application of force. Upon vinculin binding to R2R3, talin’s central actin binding site (ABS2) is exposed allowing actin to bind to talin and link to the underlying substrate. The association of actin at talin’s ABS2 is required for the transmission of actomyosin tensin onto the underlying substrate as traction force. The second results chapter focuses on the force-independent mechanisms of talin and vinculin activation and recruitment. Through the generation of a force free system, we revealed that actomyosin forces are not essential for talin to expose potential vinculin binding sites. Following talin activation, vinculin can bind to talin’s R3 domain to trigger vinculin activation. Once activated, actomyosin forces are required for talin and vinculin to recruit the FA plaque and stabilse the FA. Finally, we assembled a core subset of FA proteins into a mathematical rule based model (RBM). Using a rule based modelling technique, we were able to create the first large-scale adhesome with talin and vinculin playing central roles. Protein turnover data was used to link interactions and simulate the dynamic exchange of various talin and vinculin mutants and how the FA network can affect cellular processes (i.e., cellular migration). Together, these findings increase our knowledge in the processes that coordinate adhesion signalling and in particular, mechanotransduction. By understanding these processes, we could develop novel therapies to target diseases such as fibrosis, cancer and atherosclerosis.

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Keyword(s)

Focal Adhesion; Talin; Vinculin

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