When trafficking and signaling mix: how subcellular location shapes GPCR activation of heterotrimeric G proteins.

G protein-coupled receptors (GPCRs) physically connect extracellular information with intracellular signal propagation. Membrane trafficking plays a supportive role by 'bookending' signaling events: movement through the secretory pathway delivers GPCRs to the cell surface where receptors can sample the extracellular environment, while endocytosis and endo-lysosomal membrane trafficking provide a versatile system to titrate cellular signaling potential and maintain homeostatic control. Recent evidence suggests that, in addition to these important effects, GPCR trafficking actively shapes the cellular signaling response by altering the location and timing of specific receptor-mediated signaling reactions. Here we review key experimental evidence underlying this expanding view, focused on GPCR signaling mediated through activation of heterotrimeric G proteins. We then discuss lingering and emerging questions regarding the interface between GPCR signaling and trafficking. This article is protected by copyright. All rights reserved.