Platelet-derived growth factor (PDGF)-AB-mediated phosphorylation of PDGF beta receptors.
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ABSTRACT:
SUBMITTER: Coats SR
PROVIDER: S-EPMC1137840 | biostudies-other | 1994 Jan
REPOSITORIES: biostudies-other
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Project description: Not available
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Project description:Site-directed mutagenesis of the platelet-derived growth factor (PDGF) B-chain was conducted to determine the importance of cationic amino acid residues (Arg160-Lys161-Lys162; RKK) located within the loop III region in mediating the biological and cell-association properties of the molecule. Binding to both PDGF alpha-and beta-receptors was inhibited by the conversion of all three cationic residues into anionic glutamates (RKK-->EEE), whereas an RKK-->SSS mutant also exhibited a modest loss in affinity for beta-receptors. Replacements with serine at either Arg160 (RKK-->SKK) or at all three positions (RKK-->SSS) had little effect on binding to alpha-receptors. Replacements with either glutamic or serine residues at any of the three positions also resulted in significant inhibition of heparin-binding activity. Furthermore, the RKK-->EEE mutant exhibited decreased association with the cell surface and accumulated in the culture medium as 29-32 kDa forms. Stable transfection of U87 astrocytoma cells with RKK-->EEE mutants of either the A-chain or the B-chain inhibited malignant growth in athymic nude mice. Despite altered receptor-binding activities, each of the loop III mutants retained full mitogenic activity when applied to cultured Swiss 3T3 cells. CD spectrophotometric analysis of the RKK-->EEE mutant revealed a secondary structure indistinguishable from the wild type, with a high degree of beta-sheet structure and random coil content (50% and 43% respectively). These findings indicate an important role of the Arg160-Lys161-Lys162 sequence in mediating the biological and cell-associative activities of the PDGF-BB homodimer, and reveal that the mitogenic activity of PDGF-BB is insufficient to mediate its full oncogenic properties.
| S-EPMC1219627 | biostudies-other
Project description:PDGF-C, which is abundant in the malignant breast tumor microenvironment, plays an important role in cell growth and survival. Because tumor-associated macrophages (TAMs) contribute to cancer malignancy, macrophage survival mechanisms are an attractive area of research into controlling tumor progression. In this study, we investigated PDGF-C-mediated signaling pathways involved in anti-apoptotic effects in macrophages. We found that the human malignant breast cancer cell line MDA-MB-231 produced high quantities of PDGF-C, whereas benign MCF-7 cells did not. Recombinant PDGF-C induced PDGF receptor α chain phosphorylation, followed by Akt and Bad phosphorylation in THP-1-derived macrophages. MDA-MB-231 culture supernatants also activated macrophage PDGF-Rα. PDGF-C prevented staurosporine-induced macrophage apoptosis by inhibiting the activation of caspase-3, -7, -8, and -9 and cleavage of poly(ADP-ribose) polymerase. Finally, TAMs isolated from the PDGF-C knockdown murine breast cancer cell line 4T1 and PDGF-C knockdown MDA-MB-231-derived tumor mass showed higher rates of apoptosis than the respective WT controls. Collectively, our results suggest that tumor cell-derived PDGF-C enhances TAM survival, promoting tumor malignancy.
| S-EPMC3937687 | biostudies-literature
Project description:Abl family kinases are nonreceptor tyrosine kinases activated by diverse cellular stimuli that regulate cytoskeleton organization, morphogenesis, and adhesion. The catalytic activity of Abl family kinases is tightly regulated in cells by a complex set of intramolecular and intermolecular interactions and post-translational modifications. For example, the platelet-derived growth factor receptor beta (PDGFRβ), important for cell proliferation and chemotaxis, is a potent activator of Abl family kinases. However, the molecular mechanism by which PDGFRβ engages and activates Abl family kinases is not known. We show here that the Abl2 Src homology 2 domain directly binds to phosphotyrosine Y771 in the PDGFRβ cytoplasmic domain. PDGFRβ directly phosphorylates multiple novel sites on the N-terminal half of Abl2, including Y116, Y139, and Y161 within the Src homology 3 domain, and Y299, Y303, and Y310 on the kinase domain. Y116, Y161, Y272, and Y310 are all located at or near the Src homology 3/Src homology 2-kinase linker interface, which helps maintain Abl family kinases in an autoinhibited conformation. We also found that PDGFRβ-mediated phosphorylation of Abl2 in vitro activates Abl2 kinase activity, but mutation of these four tyrosines (Y116, Y161, Y272, and Y310) to phenylalanine abrogated PDGFRβ-mediated activation of Abl2. These findings reveal how PDGFRβ engages and phosphorylates Abl2 leading to activation of the kinase, providing a framework to understand how growth factor receptors engage and activate Abl family kinases.
| S-EPMC8259415 | biostudies-literature
Project description:The regulation of mesenchymal cell growth by signaling molecules plays an important role in maintaining tissue functions. Aberrant mesenchymal cell proliferation caused by disruption of this regulatory process leads to pathogenetic events such as fibrosis. In the current study we have identified a novel nuclear factor, Phf14, which controls the proliferation of mesenchymal cells by regulating PDGFR? expression. Phf14-null mice died just after birth due to respiratory failure. Histological analyses of the lungs of these mice showed interstitial hyperplasia with an increased number of PDGFR?(+) mesenchymal cells. PDGFR? expression was elevated in Phf14-null mesenchymal fibroblasts, resulting in increased proliferation. We demonstrated that Phf14 acts as a transcription factor that directly represses PDGFR? expression. Based on these results, we used an antibody against PDGFR? to successfully treat mouse lung fibrosis. This study shows that Phf14 acts as a negative regulator of PDGFR? expression in mesenchymal cells undergoing normal and abnormal proliferation, and is a potential target for new treatments of lung fibrosis.
| S-EPMC3431629 | biostudies-literature
Project description:Vascular endothelial growth factor (VEGF-A) is a crucial stimulator of vascular cell migration and proliferation. Using bone marrow-derived human adult mesenchymal stem cells (MSCs) that did not express VEGF receptors, we provide evidence that VEGF-A can stimulate platelet-derived growth factor receptors (PDGFRs), thereby regulating MSC migration and proliferation. VEGF-A binds to both PDGFRalpha and PDGFRbeta and induces tyrosine phosphorylation that, when inhibited, results in attenuation of VEGF-A-induced MSC migration and proliferation. This mechanism was also shown to mediate human dermal fibroblast (HDF) migration. VEGF-A/PDGFR signaling has the potential to regulate vascular cell recruitment and proliferation during tissue regeneration and disease.
| S-EPMC2064818 | biostudies-literature
Project description:We have previously shown that the T-cell protein tyrosine phosphatase (TC-PTP) dephosphorylates the platelet-derived growth factor (PDGF) beta-receptor. Here, we show that the increased PDGF beta-receptor phosphorylation in TC-PTP knockout (ko) mouse embryonic fibroblasts (MEFs) occurs primarily on the cell surface. The increased phosphorylation is accompanied by a TC-PTP-dependent, monensin-sensitive delay in clearance of cell surface PDGF beta-receptors and delayed receptor degradation, suggesting PDGF beta-receptor recycling. Recycled receptors could also be directly detected on the cell surface of TC-PTP ko MEFs. The effect of TC-PTP depletion was specific for the PDGF beta-receptor, because PDGF alpha-receptor homodimers were cleared from the cell surface at the same rate in TC-PTP ko MEFs as in wild-type MEFs. Interestingly, PDGF alphabeta-receptor heterodimers were recycling. Analysis by confocal microscopy revealed that, in TC-PTP ko MEFs, activated PDGF beta-receptors colocalized with Rab4a, a marker for rapid recycling. In accordance with this, transient expression of a dominant-negative Rab4a construct increased the rate of clearance of cell surface receptors on TC-PTP ko MEFs. Thus, loss of TC-PTP specifically redirects the PDGF beta-receptor toward rapid recycling, which is the first evidence of differential trafficking of PDGF receptor family members.
| S-EPMC1635401 | biostudies-literature
Project description:The oncogenic roles of PDGF-D and its proteolytic activator, matriptase, have been strongly implicated in human prostate cancer. Latent full-length PDGF-D (FL-D) consists of a CUB domain, a growth factor domain (GFD), and the hinge region in between. Matriptase processes the FL-D dimer into a GFD dimer (GFD-D) in a stepwise manner, involving generation of a hemidimer (HD), an intermediate product containing one FL-D subunit and one GFD subunit. Although the HD is a pro-growth factor that can be processed into the GFD-D by matriptase, the HD can also act as a dominant-negative ligand that prevents PDGF-B-mediated β-PDGF receptor activation in fibroblasts. The active GFD-D can be further cleaved into a smaller and yet inactive form if matriptase-mediated proteolysis persists. Through mutagenesis and functional analyses, we found that the R(340)R(341)GR(343)A (P4-P1/P1') motif within the GFD is the matriptase cleavage site through which matriptase can deactivate PDGF-D. Comparative sequence analysis based on the published crystal structure of PDGF-B predicted that the matriptase cleavage site R(340)R(341)GR(343)A is within loop III of the GFD, a critical structural element for its binding with the β-PDGF receptor. Interestingly, we also found that matriptase processing regulates the deposition of PDGF-D dimer species into the extracellular matrix (ECM) with increased binding from the FL-D dimer, to the HD, and to the GFD-D. Furthermore, we provide evidence that R(340)R(341)GR(343)A within the GFD is critical for PDGF-D deposition and binding to the ECM. In this study, we report a structural element crucial for the biological function and ECM deposition of PDGF-D and provide molecular insight into the dynamic functional interplay between the serine protease matriptase and PDGF-D.
| S-EPMC4423702 | biostudies-literature
Project description:Certain platelet-derived growth factor (PDGF) isoforms are associated with proliferative vitreoretinopathy (PVR), a sight-threatening complication that develops in a subset of patients recovering from retinal reattachment surgery. Although these PDGF isoforms are abundant in the vitreous of patients and experimental animals with PVR, they make only a minor contribution to activating PDGF receptor α (PDGFRα) and driving experimental PVR. Rather, growth factors outside of the PDGF family are the primary (and indirect) agonists of PDGFRα. These observations beg the question of why vitreal PDGFs fail to activate PDGFRα. We report here that vitreous contains an inhibitor of PDGF-dependent activation of PDGFRα and that a major portion of this inhibitory activity is due to vascular endothelial cell growth factor A (VEGF-A). Furthermore, recombinant VEGF-A competitively blocks PDGF-dependent binding and activation of PDGFR, signaling events, and cellular responses. These findings unveil a previously unappreciated relationship between distant members of the PDGF/VEGF family that may contribute to pathogenesis of a blinding eye disease.
| S-EPMC3347401 | biostudies-literature
Project description:Mesangial cells express platelet-derived growth factor (PDGF) A- and B-chain mRNA and release PDGF. Several polypeptide growth factors, including PDGF itself, induce PDGF A- and B- chain mRNA abundance. To understand the molecular mechanisms associated with the changes in mRNA abundance, we measured the effects of PDGF BB homodimer on PDGF A- and B-chain gene transcription in cultured mesangial cells. The data demonstrate 2- and 4-fold increases in PDGF A-chain gene transcription in response to PDGF BB homodimer at 5 and 24 h time points respectively. PDGF B-chain gene transcription was also induced approximately 3-fold at 2, 5 and 24 h time points in response to treatment with PDGF BB homodimer. The effect of PDGF BB on the half-life of PDGF A- as well as PDGF B-chain mRNA was measured directly by the pulse-chase method. There was no effect on PDGF A-chain mRNA half-life whereas PDGF B-chain mRNA half-life was increased 1.5-fold. These studies indicate that, in human mesangial cells, the increase in the levels of PDGF A- and B-chain mRNA in response to PDGF- receptor(s) activation is mediated at the level of gene transcription. In addition, the regulation of PDGF B- but not PDGF A-chain gene involves increased mRNA stability. Mesangial cells are a useful model for studying molecular mechanisms of PDGF- gene regulation in non-transformed human cells.
| S-EPMC1137841 | biostudies-other