MBI PhD Oral Defense

Time: 2pm
Date: Tuesday, 14 October 2017
Venue: Level 5 Seminar Room, T-Lab
Supervisor:  Assistant Professor Ronen Zaidel-Bar and Professor Jay Groves

Spatial-mechanical regulation of EphA2-integrin signaling

by Chen Zhongwen, Zaidel-Bar Group

Recent studies have revealed pronounced effects of the spatial distribution of EphA2 receptors on cellular response to receptor activation. However, little is known about molecular mechanisms underlying this spatial sensitivity, in part due to lack of experimental systems. In this thesis, I introduce a hybrid live cell-patterned supported lipid bilayers (SLBs) experimental platform in which the sites of EphA2 activation and integrin adhesion are spatially controlled. Fluid EphrinA1 presented on SLBs engages with cellular EphA2 receptors to form clusters, which significantly increases EphA2 signaling efficiency by promoting receptor phosphorylation and increasing downstream signaling molecule binding frequency and dwell time. Taking advantage of the spatially defined regions of EphA2 and integrin engagement, I found that ligand dependent EphA2 activation induces localized myosin-dependent contractions while simultaneously increasing focal adhesion dynamics throughout the cell. Mechanistically, Src kinase is activated at sites of ephrinA1:EphA2 clustering and subsequently diffuses on the membrane to focal adhesions, where it upregulates FAK and paxillin tyrosine phosphorylation. EphrinA1:EphA2 signaling triggers multiple cellular responses with differing spatial dependencies to enable a directed migratory response to spatially resolved contact with ephrinA1 ligands, revealing a signaling crosstalk with integrin.

*Please note only panelists are permitted for the following examination*