Regulation Of CCR7 Signaling Events By G-Protein-Coupled Receptor Kinases 2 And 3

G protein-coupled receptors (GPCR) can bind multiple ligands, leading to differential signaling events termed biased signaling. C-C chemokine receptor 7 (CCR7) is a GPCR known to have biased signaling between the two ligands it binds to, CCL19 and CCL21. Binding of C-C Chemokine Ligand 19 (CCL19) promotes a high level of CCR7 phosphorylation, while CCL21 leads to a much lower level of CCR7 phosphorylation; findings observed in HEK and dendritic cells. GPCR kinases (GRKs), which can control the phosphorylation patterns of a GPCR, are hypothesized to regulate biased signaling of a receptor. GRK expression differs between cell lines and cell types, even for ubiquitously expressed kinases, which we observed with HEK and T cells. This made us question if the role of GRKs with CCR7 signaling applied to T cell, which endogenously expresses the receptor. We aimed to explore the role of GRK2 and GRK3 in T cells since T cells have elevated GRK2, while GRK3 regulates CCR7 phosphorylation levels in HEKs. We hypothesized GRK2 would act as an inhibitor of CCR7 since there is little evidence of phosphorylation with CCR7; while GRK3's role is an initial phosphorylation kinase on CCR7, promoting receptor internalization. To test the hypothesis in T cells, we generated T cells deficient in either GRK2 or GRK3 with CRISPR-Cas9. We analyzed the regulation of CCR7 internalization, T cell migration, and signaling with either ligand. Our studies support the idea that GRK2 and GRK3 do not play interchangeable roles in ligand-bound CCR7. Each kinase is favored by a function of the CCR7, with internalization and migration to a particular ligand being affected by the loss of the kinase. In the broader context, this project could lead to targeted therapies, eliminating pathological effects, like T-ALL infiltration, without losing the immune responses of T cells.