Barbadin selectively modulates FPR2-mediated neutrophil functions independent of receptor endocytosis

Formyl peptide receptor 2 (FPR2), a member of the family of G protein-coupled receptors (GPCRs), mediates neutrophil migration, a response that has been linked to β-arrestin recruitment. β-Arrestin regulates GPCR endocytosis and can also elicit non-canonical receptor signaling. To determine the poorly understood role of β-arrestin in FPR2 endocytosis and in NADPH-oxidase activation in neutrophils, Barbadin was used as a research tool in this study. Barbadin has been shown to bind the clathrin adaptor protein (AP2) and thereby prevent β- arrestin/AP2 interaction and β-arrestin-mediated GPCR endocytosis. In agreement with this, AP2/β-arrestin interaction induced by an FPR2-specific agonist was inhibited by Barbadin. Unexpectedly, however, Barbadin did not inhibit FPR2 endocytosis, indicating that a mechanism independent of β-arrestin/AP2 interaction may sustain FPR2 endocytosis. This was confirmed by the fact, that FPR2 also underwent agonist-promoted endocytosis in β-arrestin deficient cells, albeit at a diminished level as compared to wild type cells. Dissection of the Barbadin effects on FPR2-mediated neutrophil functions including NADPH-oxidase activation mediated release of reactive oxygen species (ROS) and chemotaxis reveled that Barbadin had no effect on chemotactic migration whereas the release of ROS was potentiated/primed. The effect of Barbadin on ROS production was reversible, independent of β-arrestin recruitment, and similar to that induced by latrunculin A. Taken together, our data demonstrate that endocytic uptake of FPR2 occurs independently of β-arrestin, while Barbadin selectively augments FPR2-mediated neutrophil ROS production independently of receptor endocytosis. Given that Barbadin binds to AP2 and prevents the AP2/β-arrestin interaction, our results indicate a role for AP2 in FPR2-mediated ROS release from human neutrophils.