Phosphodiesterase-4 gates the ability of protein kinase A to phosphorylate G-protein receptor kinase-2 and influence its translocation.
Challenge of the beta(2)Ar (beta(2)-adrenergic receptor) with isoprenaline in HEK-293beta(2) cells (human embryonic kidney cells stably overexpressing a FLAG- and green fluorescent protein-tagged beta(2)Ar) results in the PKA (cAMP-dependent protein kinase) phosphorylation of GRK2 (G-protein receptor kinase-2). This response was enhanced when PDE4 (phosphodiesterase-4) activity was attenuated using either rolipram, a PDE4-selective inhibitor, or with siRNA (small interfering RNA) knockdown of both PDE4B and PDE4D. Rolipram also facilitated GRK2 recruitment to the membrane and phosphorylation of the beta(2)Ar by GRK2 in response to isoprenaline challenge of cells. In resting cells, rolipram treatment alone is sufficient to promote PKA phosphorylation of GRK2, with consequential effects on GRK2 translocation and GRK2 phosphorylation of the beta(2)Ar. Similar effects are observed in cardiac myocytes. We propose that PDE4 activity protects GRK2 from inappropriate phosphorylation by PKA in resting cells that might have occurred through fluctuations in basal cAMP levels. Thus PDE4 gates the action of PKA to phosphorylate GRK2.
Houslay
M D
MD
Molecular Pharmacology Group, Division of Biochemistry and Molecular Biology, IBLS, Wolfson Link Building, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK.
Baillie
G S
GS
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D006801:Humans; D032342:Muscle Cells / Q000201:enzymology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D021381:Protein Transport
D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; C517360:PDE4B protein, human; C517376:PDE4D protein, human