Endosome sorting of β2‐adrenoceptors is GRK5 independent

Abstract
We have investigated the role of G protein‐coupled receptor kinase 5 (GRK5) in the regulation of endosome sorting of human β2‐adrenoceptors. Expressing GRK5 at a high level significantly increased the extent of internalization of wild‐type β2‐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 β2‐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 β2‐adrenoceptors in the endocytic pathway. British Journal of Pharmacology (2004) 141, 277–284. doi:10.1038/sj.bjp.0705504