Heparan Sulfate Proteoglycans act as a cell surface co-receptors for many proteins in which a signal is sent downstream via its cytosolic domain. The role of syndecan-4 proteoglycans in FA assembly was studied in endothelial cells, and single molecule localization super-resolution microscopy showed that Syn4 loss altered the cytoskeleton protein network assembly. Using molecular and cell biology approaches we were able to demonstrate that syndecan-4 plays a pivotal role in endothelial cell behavior. Super-resolution microscopy revealed that syndecan-4 knockdown alters the level and arrangement of essential proteins for focal adhesion, including actin network and a selective decoupling of vinculin from actin, leading to lamellipodia assembly and filopodia protrusions (Figure 1). Furthermore, using Coherent Anti-stokes Raman Scattering (CARS
) microscopy, the structure of the tumors formed by such cells in mice was revealed showing its network of vascularization (Figure 2). We propose a model in which syndecan-4 acts as a central mediator: serving as a cell-signaling center in which ECM (fibronectin), cell surface (integrins) and intracellular components (actin and vinculin) come together.