Human substance P receptor undergoes agonist-dependent phosphorylation by G protein-coupled receptor kinase 5 in vitro

G protein-coupled receptor kinases (GRKs) phosphorylate agonist-occupied G protein-coupled receptors, leading to receptor desensitization. Seven GRKs, designated GRK1 through 7, have been characterized. GRK5 is negatively regulated by protein kinase C. We investigated whether human substance P receptor (hSPR) is a substrate of GRK5. We report that membrane-bound hSPR is phosphorylated by purified GRK5, and that both the rate and extent of phosphorylation increase dramatically in the presence of substance P. The phosphorylation has a high stoichiometry (20 +/- 4 mol phosphate/mol hSPR) and a low K-m (1.7 +/- 0.1 nM). These data provide the first evidence that hSPR is a substrate of GRK5. (C)2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.