CXCR1 and CXCR2 display receptor bias for shared chemokine agonists

Abstract

G protein-coupled receptors (GPCRs) mediate diverse signaling outputs through their proximal transducers: G proteins, GRKs, and {beta}-arrestins. Although ligand bias at chemokine receptors (CKRs), where ligands for the same receptor display distinct signaling patterns, is well recognized, receptor bias, where the same agonist at different receptors yields distinct transducer engagement, remains poorly understood. We compared endogenous chemokine ligands (CXCL1, CXCL5, CXCL7, CXCL8) at the highly homologous CXCR1 and CXCR2 receptors using biosensor assays to measure Gi activation, {beta}-arrestin1/2 recruitment, GRK2/3/5/6 translocation, and receptor internalization. Our data reveal qualitatively different signaling patterns, most notably where CXCL1 acts as a G protein-biased partial agonist at CXCR1 but as a balanced full agonist at CXCR2. These signaling differences correlate with receptor internalization but not subcellular ERK activation patterns measured using compartment-specific biosensors. Collectively, our findings demonstrate receptor bias in CKR signaling, transducer activation, and compartmentalized kinase activation in translating chemokine identity into discrete functional outcomes. SIGNIFICANCE STATEMENTChemokine ligand bias, where different ligands for the same receptor display different signaling patterns, is now well appreciated. However, there are only few examples of receptor bias, where the same agonist generates distinct signaling profiles at different receptors. Here we used biosensors and compartmental ERK biosensors, to show that CXCL1, CXCL5, CXCL7, and CXCL8 differentially engage G proteins, {beta}-arrestins, and GRKs, at CXCR1 and CXCR2. This work provides mechanistic insight into CXCR1/CXCR2 signaling diversity.