Epidermal Growth Factor Receptor Trans-regulate G Protein-coupled Receptor Function

G protein-coupled receptor (GPCR) kinases (GRKs) are key regulators of GPCR function. Here we demonstrate that activation of epidermal growth factor receptor (EGFR), a member of receptor tyrosine kinase family, stimulates GRK2 activity and transregulates the function of G protein-coupled opioid receptors. Our data show that EGF treatment promoted DOR endocytosis induced by DOR agonist and this required the intactness of GRK2-phosphorylation sites in DOR. EGF stimulation induced the association of GRK2 with the activated EGFR and the translocation of GRK2 to the plasma membrane. Following EGF treatment, GRK2 was phosphorylated at tyrosyl residues. Mutational analysis indicated that EGFR-mediated phosphorylation occurred at GRK2 N-terminal tyrosyl residues previously shown as c-Src phosphorylation sites. However, c-Src activity was not required for EGFR-mediated phosphorylation of GRK2. We further demonstrated that EGFR directly interacted with and phosphorylated GRK2 in vitro. Furthermore, EGF treatment remarkably elevated DOR phosphorylation in cells expressing the wild type GRK2 in an EGFR tyrosine kinase activity-dependent manner, while EGF-stimulated DOR phosphorylation was greatly decreased in cells expressing mutant GRK2 lacking EGFR tyrosine kinase sites. Interestingly, EGF stimulation directly resulted in endocytosis ofμ-opoid receptor in the absence of its cognate agonist, and which could be attenuated by GRK2 siRNA. These data indicate that EGF transregulates opioid receptor through EGFR-mediated tyrosyl phosphorylation and activation of GRK2 and propose GRK2 as a mediator of cross-talk from RTK to GPCR signaling pathway.