Ras family therapy: Rab, Rho and Rai talk to the exocyst

The exocyst is an octameric protein complex implicated in tethering vesicles to specific sites on the plasma membrane in preparation for exocytosis. Recent studies indicate that the exocyst interacts with various members of the Ras superfamily of small GTP-binding proteins. In different systems, this includes a Rab protein, several members of the Rho family and a Ral protein. Collectively, these interactions might serve to control where, when and how many vesicles are tethered to an exocytic site. This regulation is crucial in situations such as directing polarized incorporation of new membrane in epithelial cells and modulating the strength of synaptic transmission in neurons.