Abstract
G-protein-coupled receptors (GPCRs) can initiate unique functional responses depending on the subcellular site of activation. Efforts to uncover the mechanistic basis of compartmentalized GPCR signaling have concentrated on the biochemical aspect of this regulation. Here we assess the biophysical positioning of receptor-containing endosomes as an alternative salient mechanism. We devise a strategy to rapidly and selectively redistribute receptor-containing endosomes 'on command' in intact cells without perturbing their biochemical composition. Next, we present two complementary optical readouts that enable robust measurements of bulk- and gene-specific GPCR/cyclic AMP (cAMP)-dependent transcriptional signaling with single-cell resolution. With these, we establish that disruption of native endosome positioning inhibits the initiation of the endosome-dependent transcriptional responses. Finally, we demonstrate a prominent mechanistic role of PDE-mediated cAMP hydrolysis and local protein kinase A activity in this process. Our study, therefore, illuminates a new mechanism regulating GPCR function by identifying endosome positioning as the principal mediator of spatially selective receptor signaling.