title: MAP kinase protects G protein-coupled receptor kinase 2 from proteasomal degradation.
abstract: The G protein-coupled receptor kinase 2 (GRK2) phosphorylates and shuts down signaling from 7-transmembrane receptors (7TMs). Although, receptor activity controls GRK2 expression levels, the underlying molecular mechanisms are poorly understood. We have previously shown that extracellular signal-regulated kinase (ERK1/2) activation increases GRK2 expression [J. Theilade, J. Lerche Hansen, S. Haunso, S.P. Sheikh, Extracellular signal-regulated kinases control expression of G protein-coupled receptor kinase 2 (GRK2), FEBS Lett. 518 (2002) 195-199]. In the present study, we found that ERK1/2 regulates GRK2 degradation rather than synthesis. ERK1/2 blockade using PD98059 decreased GRK2 cellular levels to 0.25-fold of control in Cos7 cells. This effect was due to enhanced degradation of the GRK2 protein, since proteasome blockade prevented down-regulation of GRK2 protein levels in the presence of PD98059. Further, ERK blockade had no effect on GRK2 synthesis as probed using a reporter construct carrying the GRK2 promoter upstream of the luciferase gene. We predict ERK1/2 mediated GRK2 protection could be a general phenomenon as proteasome inhibition increased GRK2 expression in two other cell lines, HEK293 and NIH3T3.
authors.affiliation: The Laboratory of Molecular and Cellular Cardiology, Department of Medicine B, Copenhagen University Hospital B9312, 20, Juliane Mariesvej, DK-2100 Copenhagen, Denmark.
authors.forename: Juliane
authors.initials: J
authors.lastname: Theilade
authors.forename: Jakob L
authors.initials: JL
authors.lastname: Hansen
authors.forename: Stig
authors.initials: S
authors.lastname: Haunsø
authors.forename: Søren P
authors.initials: SP
authors.lastname: Sheikh
mesh_terms: D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D054769:G-Protein-Coupled Receptor Kinase 2; D054770:G-Protein-Coupled Receptor Kinase 3; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D051552:beta-Adrenergic Receptor Kinases
chemical_list: D017868:Cyclic AMP-Dependent Protein Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C496567:GRK2 protein, human; C517848:GRK3 protein, human; C517850:GRK3 protein, mouse; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D046988:Proteasome Endopeptidase Complex