Endosome sorting of β 2 ‐adrenoceptors is GRK5 independent

We have investigated the role of G protein‐coupled receptor kinase 5 (GRK5) in the regulation of endosome sorting of human β 2 ‐adrenoceptors. Expressing GRK5 at a high level significantly increased the extent of internalization of wild‐type β 2 ‐adrenoceptors and of an internalization‐defective mutant receptor, and increased receptor phosphorylation at serines 355 and 356 in the cytoplasmic tail. Overexpressing GRK5 did not alter β 2 ‐adrenoceptor recycling as assessed by immunofluorescence microscopy and radioligand binding assays nor was there any change in receptor downregulation. These data indicate that GRK5 does not regulate the sorting of β 2 ‐adrenoceptors in the endocytic pathway.British Journal of Pharmacology (2004) 141 , 277–284. doi: 10.1038/sj.bjp.0705504