Coordinating Eph-dependent cell-cell contacts and syndecan-4-dependent cell-matrix contacts to regulate cell migration during wound healing

In healthy adults, the majority of cells are immotile but, upon wounding, damage signals induce fibroblast migration into a wound bed that facilitates healing. Transmembrane receptors up-regulated upon wounding, and necessary for repair, include the matrix receptor, syndecan-4, and the Eph family of cell-cell receptors. The interplay between cell-matrix and cell-cell contacts is critical to both the initiation and guidance of cell migration, and this is particularly true of Eph receptors, which are capable of both attractive and repulsive signals.

This project will examine the mutual regulation of syndecan-4 and Eph receptors with particular focus on endocytic regulation. Syndecan-4 is already known to regulate endocytosis and trafficking of matrix receptors, and Eph receptor endocytosis is a key step in converting attractive signals to cell-cell repulsion. Biochemical techniques will be combined with live confocal imaging and RNAi to elucidate the mechanistic relationship between receptors. Migration analysis through complex extracellular matrix or in response to ligand-coated beads will allow the effects of syndecan-4 and Eph receptor on cell directionality to be determined. The combination of quantitative migration analysis, fluorophore-tagged receptor tracking and FRET-based protrusion analysis will allow the complete pathway from molecule to cell behaviour to be elucidated. There is also the opportunity to take the next step and test these findings in our existing animal models, thus ensuring the in vivo relevance of the study. Collectively these experiments will determine how fibroblast migration during a healing response is initiated. At the same time the ability of Eph receptors to inhibit syndecan-4 by phosphorylation will be examined. The termination of cell migration is just as important as healing initiation, as dysregulated cell migration will result in tumour development. Comparison of the phosphorylation status between active and inactive syndecan-4 cell types, in response to Eph receptor engagement, will grant insight into possible negative feedback between syndecan-4 and Eph receptor.

The therapy already reduces fracture-healing times by 40%, and has the potential to be refined even further as the target molecules are resolved. The student will have access to the Smith & Nephew technology and as key molecular events are identified, the ability of ultrasound to overcome such defects will be tested, with the objective of identifying the point of ultrasound action.