Tethering of the Platelet-derived Growth Factor β Receptor to G-protein-coupled Receptors

A NOVEL PLATFORM FOR INTEGRATIVE SIGNALING BY THESE RECEPTOR CLASSES IN MAMMALIAN CELLS*

Abstract

Here we provide evidence to show that the platelet-derived growth factor β receptor is tethered to endogenous G-protein-coupled receptor(s) in human embryonic kidney 293 cells. The tethered receptor complex provides a platform on which receptor tyrosine kinase and G-protein-coupled receptor signals can be integrated to produce more efficient stimulation of the p42/p44 mitogen-activated protein kinase pathway. This was based on several lines of evidence. First, we have shown that pertussis toxin (which uncouples G-protein-coupled receptors from inhibitory G-proteins) reduced the platelet-derived growth factor stimulation of p42/p44 mitogen-activated protein kinase. Second, transfection of cells with inhibitory G-protein α subunit increased the activation of p42/p44 mitogen-activated protein kinase by platelet-derived growth factor. Third, platelet-derived growth factor stimulated the tyrosine phosphorylation of the inhibitory G-protein α subunit, which was blocked by the platelet-derived growth factor kinase inhibitor, tyrphostin AG 1296. We have also shown that the platelet-derived growth factor β receptor forms a tethered complex with Myc-tagged endothelial differentiation gene 1 (a G-protein-coupled receptor whose agonist is sphingosine 1-phosphate) in cells co-transfected with these receptors. This facilitates platelet-derived growth factor-stimulated tyrosine phosphorylation of the inhibitory G-protein α subunit and increases p42/p44 mitogen-activated protein kinase activation. In addition, we found that G-protein-coupled receptor kinase 2 and β-arrestin I can associate with the platelet-derived growth factor β receptor. These proteins play an important role in regulating endocytosis of G-protein-coupled receptor signal complexes, which is required for activation of p42/p44 mitogen-activated protein kinase. Thus, platelet-derived growth factor β receptor signaling may be initiated by G-protein-coupled receptor kinase 2/β-arrestin I that has been recruited to the platelet-derived growth factor β receptor by its tethering to a G-protein-coupled receptor(s). These results provide a model that may account for the co-mitogenic effect of certain G-protein-coupled receptor agonists with platelet-derived growth factor on DNA synthesis.

  • Abbreviations:
    GPCR
    G-protein-coupled receptor
    MAPK
    mitogen-activated protein kinase
    MEK1
    mitogen-activated protein kinase kinase 1
    IGF-1
    insulin like growth factor-1
    GRK
    G-protein-coupled receptor kinase
    PDGF
    platelet-derived growth factor
    PDGFβR
    PDGF receptor β
    PI3K
    phosphoinositide 3-kinase
    EGF
    epidermal growth factor
    EDG
    endothelial differentiation gene
    S1P
    sphingosine 1-phosphate
    MEM
    minimum essential medium
    HRP
    horseradish peroxidase
    Gab1
    Grb-2 associated binder
    Gi
    inhibitory G-protein
    Giα
    α subunit of Gi
    Grb
    growth factor receptor binding protein
    • Received March 29, 2001.
    Table of Contents

    This Article

    1. The Journal of Biological Chemistry 276, 28578-28585.
    1. All Versions of this Article:
      1. M102771200v1
      2. 276/30/28578 (most recent)

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