title: Platelet-derived growth factor receptor-beta (PDGFR-beta) activation promotes its association with the low density lipoprotein receptor-related protein (LRP). Evidence for co-receptor function.
abstract: Activation of the platelet-derived growth factor receptor-beta (PDGFR-beta) leads to tyrosine phosphorylation of the cytoplasmic domain of LRP and alters its association with adaptor and signaling proteins, such as Shc. The mechanism of the PDGF-induced LRP tyrosine phosphorylation is not well understood, especially since PDGF not only activates PDGF receptor but also binds directly to LRP. To gain insight into this mechanism, we used a chimeric receptor in which the ligand binding domain of the PDGFR-beta was replaced with that from the macrophage colony-stimulating factor (M-CSF) receptor, a highly related receptor tyrosine kinase of the same subfamily, but with different ligand specificity. Activation of the chimeric receptor upon the addition of M-CSF readily mediated the tyrosine phosphorylation of LRP. Since M-CSF is not recognized by LRP, these results indicated that growth factor binding to LRP is not necessary for this phosphorylation event. Using a panel of cytoplasmic domain mutants of the chimeric M-CSF/PDGFR-beta, we confirmed that the kinase domain of PDGFR-beta is absolutely required for LRP tyrosine phosphorylation but that PDGFR-beta-mediated activation of phosphatidylinositol 3-kinase, RasGAP, SHP-2, phospholipase C-gamma, and Src are not necessary for LRP tyrosine phosphorylation. To identify the cellular compartment where LRP and the PDGFR-beta may interact, we employed immunofluorescence and immunogold electron microscopy. In WI-38 fibroblasts, these two receptors co-localized in coated pits and endosomal compartments following PDGF stimulation. Further, phosphorylated forms of the PDGFR-beta co-immunoprecipitated with LRP following PDGF treatment. Together, these studies revealed close association between activated PDGFR-beta and LRP, suggesting that LRP functions as a co-receptor capable of modulating the signal transduction pathways initiated by the PDGF receptor from endosomes.
authors.affiliation: Department of Surgery and Physiology, University of Maryland School of Medicine, 15601 Crabbs Branch Way, Rockville, Maryland 20855, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Newton
authors.forename: Elena
authors.initials: E
authors.lastname: Loukinova
authors.forename: Irina
authors.initials: I
authors.lastname: Mikhailenko
authors.forename: Sripriya
authors.initials: S
authors.lastname: Ranganathan
authors.forename: Yamei
authors.initials: Y
authors.lastname: Gao
authors.forename: Christian
authors.initials: C
authors.lastname: Haudenschild
authors.forename: Dudley K
authors.initials: DK
authors.lastname: Strickland
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D009154:Mutation; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000378:metabolism; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011993:Recombinant Fusion Proteins; D020703:ras GTPase-Activating Proteins; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D016186:Receptor, Macrophage Colony-Stimulating Factor; D020797:Receptor, Platelet-Derived Growth Factor beta; C516724:PTPN11 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; D010738:Type C Phospholipases; D051966:Phospholipase C gamma