Specifically phosphorylates the activated forms of G protein-coupled receptors. Such receptor phosphorylation initiates beta-arrestin-mediated receptor desensitization, internalization, and signaling events leading to their desensitization. Seems to be involved in the desensitization of D2-like dopamine receptors in striatum and chemokine receptor CXCR4 which is critical for CXCL12-induced cell chemotaxis (By similarity). Phosphorylates rhodopsin (RHO) (in vitro) and a non G-protein-coupled receptor, LRP6 during Wnt signaling (in vitro) (By similarity). [G-protein-coupled receptor] + ATP = [G-protein-coupled receptor]-phosphate + ADP + H(+) Interacts with GIT1. Expressed in the brain in striatal neurons. Deficient mice show significant altered central dopamine receptors regulation, deficient lymphocyte chemotaxis and increased acute inflammation and neutrophil chemotaxis. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family. GPRK subfamily.