Role of the Ras-GTPase activating protein Rasa3 in Angiogenesis processes

Rasa3 is a member of the Ras GAP1 subfamily and is known to function as dual GAP (GTPase activating protein) for Ras and Rap1 smallGTPases. Homologous knockout mice expressing a catalytically-inactive Rasa3 protein die during embryonic life from massive bleedings due to destabilisation of endothelial junctions. The main goal of this project is to investigate and characterize the role of Rasa3 in angiogenesis which is the process by which new blood vessels develop from pre-existing ones.
Here, we show that loss of function of Rasa3 in Huvecs (Human Umbilical Vein Endothelial Cells) affects their angiogenic potential. Interestingly, we found that inactivation of Rasa3 impacts migration/adhesion-related properties of endothelial cells. Using phase contrast microscopy and TIRF technology we showed that Rasa3 inactivation doesn’t affect cell directionality and that the stronger adhesion of cells on fibronectin is due to a downregulation of adhesion turnover. We showed that these alterations can be attributed to the hyperactivation of the smallGTPase Rap1 and downregulation of FAK/SRC signalling. We suggest that in the absence of Rap1, hyperactivation of FAK/SRC following integrin engagement could explain the different phenotypes observed. Altogether these preliminary results suggested a critical function of Rasa3 in angiogenesis.