Septin2 Mediated Maturation of Endothelial Podosomes is Required for Angiogenesis

Podosomes are compartmentalized actin-rich adhesions, defined by their ability to locally secrete proteases and remodel extracellular matrix. Matrix remodeling by endothelial podosomes facilitates invasion, and thereby vessel formation. However, the mechanisms underlying endothelial podosome formation and function remain unclear. Here we demonstrate that Septins2, 6, and 7 are required for maturation of nascent endothelial podosomes into matrix degrading organelles. We show that podosome development occurs through initial mobilization of the scaffolding protein Tks5 and F-actin accumulation, followed by later recruitment of Septin2. Septin2 localizes around the perimeter of podosomes in close proximity to the basolateral plasma membrane; and phosphoinositide binding residues of Septin2 are required for podosome function. Combined, our results suggest that the septin cytoskeleton forms a diffusive barrier around nascent podosomes to promote their maturation. Finally, we show that Septin2-mediated regulation of podosomes is critical for endothelial cell invasion and nascent vessel perfusion in vivo. Therefore, targeting of Septin2-mediated podosome formation is a potentially attractive anti-angiogenesis strategy.