Epac1 (exchange protein directly activated by cyclic AMP [cAMP]) couples intracellular cAMP to the activation of Rap1, a Ras family GTPase that regulates cell adhesion, proliferation, and differentiation. Using mass spectrometry, we identified the small G protein Ran and Ran binding protein 2 (RanBP2) as potential binding partners of Epac1. Ran is a small G protein best known for its role in nuclear transport and can be found at the nuclear pore through its interaction with RanBP2. Here we demonstrate that Ran-GTP and Epac1 interact with each other in vivo and in vitro. This binding requires a previously uncharacterized Ras association (RA) domain in Epac1. Surprisingly, the interaction of Epac1 with Ran is necessary for the efficient activation of Rap1 by Epac1. We propose that Ran and RanBP2 anchor Epac1 to the nuclear pore, permitting cAMP signals to activate Rap1 at the nuclear envelope.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to SciCrunch, however this is not currently a free service.