GPR97-mediated PAR2 transactivation via a mPR3-associated macromolecular complex induces inflammatory activation of human neutrophils

Abstract Neutrophils play essential anti-microbial and inflammatory roles in host defense, however their activities are tightly regulated as neutrophil dysfunction often leads to detrimental inflammatory and autoimmune diseases. Here, we identified a novel PR3/CD177/GPR97/PAR2/CD16b interactome as a critical modulator of neutrophil activation. Using multiple approaches, we deorphanized GPR97, a human neutrophil-restricted adhesion G protein-coupled receptor (aGPCR), as the interacting protein and allosteric activator of CD177-associated membrane proteinase 3 (mPR3). Structural and deletion analysis of the GPR97 extracellular region disclosed two independent mPR3-binding domains. The efficient binding and activation of mPR3 by GPR97 required a macromolecular CD177/GPR97/PAR2/CD16b interactome and resulted in the transactivation of PAR2, another GPCR. GPR97-mediated PAR2 transactivation in neutrophils elicited strong inflammatory activation, triggering anti-microbial activities and endothelial dysfunction. Altogether, we identify a novel aGPCR-GPCR transactivation mechanism that directs neutrophil activation and inflammation. The PR3/CD177/GPR97/PAR2/CD16b interactome represents a potential therapeutic target for neutrophil-mediated inflammatory diseases.