Structural aspects of talin regulation through Rap1A signalling

Zacharchenko, Thomas
Structural aspects of talin regulation through Rap1A signalling. PhD thesis, University of Liverpool.

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At the nascent focal adhesion, GTPase Rap1A recruits the adaptor protein RIAM (Rap1 Interacting Adaptor Molecule), and RIAM recruits the scaffold protein talin facilitating integrin activation (Lee et al., 2009). As the nascent adhesion matures, actin linkages are strengthened via recruitment of the talin-actin bridging protein vinculin. In vivo data shows that RIAM is not found in mature focal adhesions; furthermore RIAM and vinculin occupy the same binding sites within talin (Goult et al., 2013). This thesis shows that RIAM-talin interaction is synergistic, with multiple domains simultaneously contributing to the binding. Vinculin and RIAM compete for talin, providing a mechanism of RIAM displacement by vinculin as adhesions mature. The interactions are thus characterised by a range biophysical techniques. SHARPIN (Shank associated RH-domain interacting Protein) potentially competes with talin for integrin binding (Rantala et al., 2011). SHARPIN interaction with the synaptic protein SHANK3 (SH3 and multiple ankyrin repeat domains protein 3) may provide a mechanism for SHANK3 recruitment to the adhesion (Lim et al., 2001). This thesis solves the structure of the SHANK N-terminal domain that contains the SHARPIN binding region. The structure shows the presence of a previously uncharacterised RA (Ras-association) domain that packs against the following ankyrin repeat domain. We show the RA domain binds with high affinity to the GTPase-Rap1A. Rap1A-SHANK could provide a negative feedback pathway for integrin regulation in adhesion. In the course of adhesion maturation multiple proteins are recruited to the adhesion complex; these proteins facilitate linkages to the actomyosin contractile machinery. One such protein is DLC1 (Deleted in Liver Cancer 1); DLC1 contains an LD-like motif that is homologues to the LD domains of the adhesion protein paxillin (Brown et al., 1996). This LD-like motif is responsible for tumour suppressor function and binding to talin (Li et al., 2011; Cao et al., 2012). In this thesis we characterise the talin-DLC1 interaction using X-ray crystallography, and suggest mutations to disrupt the interaction in cell experiments.

Item Type: Thesis (PhD)
Additional Information: Date: 2013-08 (completed)
Depositing User: Symplectic Admin
Date Deposited: 08 Aug 2014 10:00
Last Modified: 16 Dec 2022 04:41
DOI: 10.17638/00014693