Localized regulation of GEF-H1 at the cell edge by MT dynamics and Src. GEF-H1 is released at the cell edge by depolymerizing MTs. Upon its release, phosphorylation by Src further activates GEF-H1 and localizes it at the cell edge. While MT depolymerization occurs throughout the cell, the highest number of MT disassembly events was observed in the area ~1.6–3.2 µm from the cell boundary. Control of GEF-H1 by Src occurs in discrete locations of the region ~0–1.6 µm from the edge. Polymerizing MTs recapture and deactivate GEF-H1.