title: G protein-coupled receptor kinase 2 negatively regulates chemokine signaling at a level downstream from G protein subunits.
abstract: The G protein-coupled receptor kinase 2 (GRK2) phosphorylates and desensitizes ligand-activated G protein-coupled-receptors. Here, evidence is shown for a novel role of GRK2 in regulating chemokine-mediated signals. The presence of increased levels of GRK2 in human embryonic kidney (HEK) 293 cells produced a significant reduction of the extracellular signal-regulated kinase (ERK) response to CCL2. This effect is independent of its role in receptor phosphorylation because the kinase-deficient mutant GRK2K220R was able to reduce this response, and ERK activation by CCR2BIX, a phosphorylation-defective receptor mutant, was also inhibited by GRK2. Constructs containing the Galpha(q)-binding RGS-like RH domain of GRK2 or its Gbetagamma-binding domain could not reproduce the inhibition, thus revealing that GRK2 acts downstream of G proteins. Interestingly, chemokine-driven mitogen-activated protein kinase kinase (MEK) stimulation is not affected in cells overexpressing GRK2 or GRK2K220R or in splenocytes from heterozygous GRK2 mice, where reduced kinase levels correlate with enhanced ERK activation by chemokines. We find GRK2 and MEK in the same multimolecular complex, thus suggesting a mechanism for GRK2 regulation of ERK activity that involves a direct or coordinate interaction with MEK. These results suggest an important role for GRK2 in the control of chemokine induction of ERK activation at the level of the MEK-ERK interface.
authors.affiliation: Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Jiménez-Sainz
authors.forename: Cristina
authors.initials: C
authors.lastname: Murga
authors.forename: Annemieke
authors.initials: A
authors.lastname: Kavelaars
authors.forename: María
authors.initials: M
authors.lastname: Jurado-Pueyo
authors.forename: Beate F
authors.initials: BF
authors.lastname: Krakstad
authors.forename: Cobi J
authors.initials: CJ
authors.lastname: Heijnen
authors.forename: Federico
authors.initials: F
authors.lastname: Mayor
authors.forename: Anna M
authors.initials: AM
authors.lastname: Aragay
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D054769:G-Protein-Coupled Receptor Kinase 2; D005786:Gene Expression Regulation / Q000187:drug effects; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051552:beta-Adrenergic Receptor Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D018932:Chemokine CCL2; D021122:Protein Subunits; C496568:GRK2 protein, mouse; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020962:Heterotrimeric GTP-Binding Proteins