title: G protein-coupled receptor kinase 4 (GRK4) regulates the phosphorylation and function of the dopamine D3 receptor.
abstract: During conditions of moderate sodium excess, the dopaminergic system regulates blood pressure and water and electrolyte balance by engendering natriuresis. Dopamine exerts its effects on dopamine receptors, including the dopamine D(3) receptor. G protein-coupled receptor kinase 4 (GRK4), whose gene locus (4p16.3) is linked to essential hypertension, desensitizes the D(1) receptor, another dopamine receptor. This study evaluated the role of GRK4 on D(3) receptor function in human proximal tubule cells. D(3) receptor co-segregated in lipid rafts and co-immunoprecipitated and co-localized in human proximal tubule cells and in proximal and distal tubules and glomeruli of kidneys of Wistar Kyoto rats. Bimolecular fluorescence complementation and confocal microscopy revealed that agonist activation of the receptor initiated the interaction between D(3) receptor and GRK4 at the cell membrane and promoted it intracellularly, presumably en route to endosomal trafficking. Of the four GRK4 splice variants, GRK4-gamma and GRK4-alpha mediated a 3- and 2-fold increase in the phosphorylation of agonist-activated D(3) receptor, respectively. Inhibition of GRK activity with heparin or knockdown of GRK4 expression via RNA interference completely abolished p44/42 phosphorylation and mitogenesis induced by D(3) receptor stimulation. These data demonstrate that GRK4, specifically the GRK4-gamma and GRK4-alpha isoforms, phosphorylates the D(3) receptor and is crucial for its signaling in human proximal tubule cells.
authors.affiliation: National Institute of Molecular Biology and Biotechnology, University of the Philippines, Diliman, Quezon City 1101, Philippines. vvillar@cnmc.org
authors.forename: Van Anthony M
authors.initials: VA
authors.lastname: Villar
authors.forename: John E
authors.initials: JE
authors.lastname: Jones
authors.forename: Ines
authors.initials: I
authors.lastname: Armando
authors.forename: Cynthia
authors.initials: C
authors.lastname: Palmes-Saloma
authors.forename: Peiying
authors.initials: P
authors.lastname: Yu
authors.forename: Annabelle M
authors.initials: AM
authors.lastname: Pascua
authors.forename: Lindsay
authors.initials: L
authors.lastname: Keever
authors.forename: Francis B
authors.initials: FB
authors.lastname: Arnaldo
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Yingjin
authors.initials: Y
authors.lastname: Luo
authors.forename: Robin A
authors.initials: RA
authors.lastname: Felder
authors.forename: Pedro A
authors.initials: PA
authors.lastname: Jose
mesh_terms: D000818:Animals; D016466:CHO Cells; D002499:Centrifugation, Density Gradient; D006224:Cricetinae; D003412:Cricetulus; D011992:Endosomes / Q000378:metabolism; D054771:G-Protein-Coupled Receptor Kinase 4 / Q000096:biosynthesis* / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism; D010766:Phosphorylation; D020033:Protein Isoforms; D051381:Rats; D050637:Receptors, Dopamine D3 / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D020033:Protein Isoforms; D050637:Receptors, Dopamine D3; D054771:G-Protein-Coupled Receptor Kinase 4; C517855:GRK4 protein, human