How is cell migration regulated by the extracellular matrix: role of syndecan-4 and integrin-alpha5beta1 receptors in the regulation of Rho family GTPases?. (360G-Wellcome-088419_Z_09_Z)

I aim to understand how syndecan-4 regulates Rho-family GTPases and integrin-alpha5beta1 to achieve directional cell migration. Specifically I will address: A. Regulation of the principal RhoA suppressor, p190RhoGAP by syndecan-4. I will map the syndecan-4-dependent phosphorylation sites of p190RhoGAP and identify p190RhoGAP-binding partners. Subsequently, I will examine the effects of p190RhoGAP regulation on the activities of RhoA, Rac1 and cell migration. B. Regulation of Rac1 by s yndecan-4. First, I will identify the GTP-exchange factor(s) (GEF(s)) responsible for syndecan-4-dependent Rac1 activation. Second, I will characterise syndecan-4-dependent Rac1 inhibition and turnover through p190RhoGAP. By defining simultaneous activation and turnover pathways, I will resolve mechanisms of precise spatiotemporal regulation and rapid cycling of active Rac1. I will demonstrate how localisation of these events results in directional cell migration in response to syndecan-4 en gagement. C. Regulation of integrin-alpha5beta1 by syndecan-4 that determines adhesive strength. My preliminary experiments have revealed that engagement of syndecan-4 reduces the strength of cell adhesion to integrin ligands. I will identify the mechanism of this novel relationship, focusing on the effect of syndecan-4 engagement on activity and distribution of integrins. Through these aims I will resolve novel mechanisms of GTPase coordination, rapid cycling of active Rac1 and regulat ed cell adhesion.