G protein-coupled receptor (GPCR) kinases (GRKs) phosphorylate activated heptahelical receptors, leading to their uncoupling from G proteins[1]. GRKs and arrestins are key participants in the canonical pathways leading to phosphorylation-dependent GPCR desensitization, endocytosis, intracellular trafficking and resensitization as well as in the modulation of important intracellular signaling cascades by GPCR. Activity of GRKs is tightly modulated by mechanisms including phosphorylation by different kinases and interaction with several cellular proteins such as calmodulin, caveolin or RKIP. In addition, GRKs are involved in multiple interactions with non-receptor proteins (PI3K, Akt, GIT or MEK) that point to novel GRK cellular roles[2]. GRK family consists of seven cytosolic serine/threonine (Ser/Thr) protein kinases, and among them, GRK2 is involved in the regulation of an enormous range of both G protein-coupled receptors (GPCRs) and non-GPCR substrates that participate in or regulate many critical cellular processes[3]. GRK2 dysfunction is associated with multiple diseases, including cancers, brain diseases, cardiovascular and metabolic diseases, and therefore GRK2-specifc substrates/inhibitors are needed not only for studies of GRK2-mediated cellular functions but also for GRK2-targeted drug development[3].