Phosphorylation of the platelet-derived growth factor receptor-beta by G protein-coupled receptor kinase-2 reduces receptor signaling and interaction with the Na(+)/H(+) exchanger regulatory factor.
G protein-coupled receptor kinase-2 (GRK2) can phosphorylate and desensitize the platelet-derived growth factor receptor-beta (PDGFRbeta) in heterologous cellular systems. To determine whether GRK2 regulates the PDGFRbeta in physiologic systems, we examined PDGFRbeta signaling in mouse embryonic fibroblasts from GRK2-null and cognate wild type mice. To discern a mechanism by which GRK2-mediated phosphorylation can desensitize the PDGFRbeta, but not the epidermal growth factor receptor (EGFR), we investigated effects of GRK2-mediated phosphorylation on the association of the PDGFRbeta with the Na(+)/H(+) exchanger regulatory factor (NHERF), a protein shown to potentiate dimerization of the PDGFRbeta, but not the EGFR. Physiologic expression of GRK2 diminished (a) phosphoinositide hydrolysis elicited through the PDGFRbeta but not heterotrimeric G proteins; (b) Akt activation evoked by the PDGFRbeta but not the EGFR; and (c) PDGF-induced tyrosyl phosphorylation of the PDGFRbeta itself. PDGFRbeta desensitization by physiologically expressed GRK2 correlated with a 2.5-fold increase in PDGF-promoted PDGFRbeta seryl phosphorylation. In 293 cells, GRK2 overexpression reduced PDGFRbeta/NHERF association by 60%. This effect was reproduced by S1104D mutation of the PDGFRbeta, which also diminished PDGFRbeta activation and signaling (like the S1104A mutation) to an extent equivalent to that achieved by GRK2-mediated PDGFRbeta phosphorylation. GRK2 overexpression desensitized only the wild type but not the S1104A PDGFRbeta. We conclude that GRK2-mediated PDGFRbeta seryl phosphorylation plays an important role in desensitizing the PDGFRbeta in physiologic systems. Furthermore, this desensitization appears to involve GRK2-mediated phosphorylation of PDGFRbeta Ser(1104), with consequent dissociation of the PDGFRbeta from NHERF.
Hildreth
Kerry L
KL
Department of Medicine (Cardiology), Duke University Medical Center, Durham, North Carolina 27710, USA.
Wu
Jiao-Hui
JH
Barak
Larry S
LS
Exum
Sabrina T
ST
Kim
Luke K
LK
Peppel
Karsten
K
Freedman
Neil J
NJ
D000818:Animals; D002417:Cattle; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism* / Q000502:physiology; D004815:Epidermal Growth Factor; D005347:Fibroblasts / Q000378:metabolism; D054770:G-Protein-Coupled Receptor Kinase 3; D006801:Humans; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers; D014162:Transfection; D051552:beta-Adrenergic Receptor Kinases
D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D012694:Serine; D004815:Epidermal Growth Factor; D020797:Receptor, Platelet-Derived Growth Factor beta; D017868:Cyclic AMP-Dependent Protein Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C517848:GRK3 protein, human; C517850:GRK3 protein, mouse; D051552:beta-Adrenergic Receptor Kinases