G protein-coupled receptor kinases (GRKs) belong to the AGC family of serine/threonine kinases. They phosphorylate agonist-activated G protein-coupled receptors (hence the name). This phosphorylation triggers the binding of arrestins to the receptors. Receptor:arrestin interaction then leads to the desensitization of G protein activation by the receptors and can also lead to internalization of the receptors and initiation of new signaling pathways. Some G protein-coupled receptor kinases can also constitutively phosphorylate cytosolic proteins, including beta-tubulin …