Guanine nucleotide exchange factor (GEF) for RAP1A and RAP2A small GTPases that is activated by binding cAMP. Through simultaneous binding of PDE3B to RAPGEF3 and PIK3R6 is assembled in a signaling complex in which it activates the PI3K gamma complex and which is involved in angiogenesis. Plays a role in the modulation of the cAMP-induced dynamic control of endothelial barrier function through a pathway that is independent on Rho-mediated signaling. Required for the actin rearrangement at cell-cell junctions, such as stress fibers and junctional actin (By similarity). Interacts with PDE3B and PIK3R6; form a signaling complex that regulates phosphatidylinositol 3-kinase gamma in angiogenesis. The DEP domain is involved in membrane localization independent from regulation by cAMP. It is uncertain whether Met-1 or Met-43 is the initiator.