Subcellular localization of GPCR kinases differentially modulate biased signaling at CXCR3

Abstract

Some G protein-coupled receptors (GPCRs) demonstrate biased signaling, where ligands of the same receptor differentially activate specific downstream signaling pathways over others. Ligand-specific receptor phosphorylation by GPCR kinases (GRKs) is one mechanism underlying this phenomenon. Recent evidence demonstrates that GPCRs traffic to and signal from subcellular compartments beyond the plasma membrane, a paradigm termed location bias. Here, we show that GRKs translocate to endosomes following stimulation of the chemokine receptor CXCR3 and other GPCRs. The GRK recruitment patterns at the plasma membrane and endosome are distinct and depend on the identity of the ligand used to activate the receptor. Using cells deficient of GRKs, we demonstrate that biased ligands have unique signaling profiles upon rescue of location-specific GRK isoforms. Our work highlights a role of the GRKs in location-biased GPCR signaling and demonstrates the complex interactions between ligand, GRK isoform and cellular location that contribute to biased signaling.