Regulation in time and space of signal transduction networks is one of the most fundamental processes in biology. Our lab studies the Rap1 signalling network, which is involved many physiological processes and a critical component in spatial and temporal control of cell adhesion and secretion. The Rap1 network includes the cAMP target Epac, a protein involved in among others endothelial cell junction formation, heart function, memory, circadian rhythm and insulin secretion.The Cerebral Cavernous Malformation (CCM)1 protein was previously identified as an effector of Rap1 involved in endothelial junction integrity and recently we found that CCM2 and CCM3 and the CCM1 interacting protein ICAP, is also involved in the process. Importantly, activation of Epac results in a rapid translocation of CCM1 to the junction. This implies that the environment of the protein and/or complex changes during cAMP signalling. In this project we aim to determine the effects of Epac-Rap1 on CCM complex formation. We will selectively activate Epac and determine the content and modifications of the CCM complex and associated proteins by quantitative mass spec. We anticipate that this study will result in a better understanding of how the Epac-Rap1 signalling network controls cell junction formation.