| 1. |
- Blume-Jensen, Peter, et al.
(författare)
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Activation of the human c-kit product by ligand-induced dimerization mediates circular actin reorganization and chemotaxis
- 1991
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Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 10:13, s. 4121-4128
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Tidskriftsartikel (refereegranskat)abstract
- The proto-oncogene c-kit is allelic with the murine white spotting (W) locus and encodes a transmembrane protein tyrosine kinase that is structurally related to the receptors for platelet-derived growth factor (PDGF) and colony-stimulating factor-1 (CSF-1). Recently the ligand for the c-kit product, stem cell factor (SCF), was identified in both transmembrane and soluble forms. In order to examine the mechanism for receptor activation by SCF and biological properties of the activated c-kit product, we transfected the wild-type human c-kit cDNA into porcine aortic endothelial cells. We found that the receptor was down-regulated and transmitted a mitogenic signal in response to stimulation with soluble SCF. We also demonstrate that SCF induces dimerization of the c-kit product in intact cells, and that dimerization of the receptor is correlated with activation of its kinase. Activation of the c-kit product by SCF was found to induce circular actin reorganization indistinguishable from that mediated by the PDGF beta-receptor in response to PDGF-BB. Furthermore, soluble SCF was a potent chemotactic agent for cells expressing the c-kit product, a property which might be of importance during embryonic development.
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| 2. |
- Hansen, Klaus, et al.
(författare)
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Mutation of a Src phosphorylation site in the PDGF beta-receptor leads to increased PDGF-stimulated chemotaxis but decreased mitogenesis
- 1996
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Ingår i: EMBO Journal. - 0261-4189 .- 1460-2075. ; 15:19, s. 5299-5313
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Tidskriftsartikel (refereegranskat)abstract
- Ligand induced activation of the beta-receptor for platelet-derived growth factor (PDGF) leads to activation of Src family tyrosine kinases. We have explored the possibility that the receptor itself is a substrate for Src. We show that Tyr934 in the kinase domain of the PDGF receptor is phosphorylated by Src. Cell lines expressing a beta-receptor mutant, in which Tyr934 was replaced with a phenyalanine residue, showed reduced mitogenic signaling in response to PDGF-BB. In contrast, the mutant receptor mediated increased signals for chemotaxis and actin reorganization. Whereas the motility responses of cells expressing wild-type beta-receptors were attenuated by inhibition of phosphatidylinositol 3'-kinase, those of cells expressing the mutant receptor were only slightly influenced. In contrast, PDGF-BB-induced chemotaxis of the cells with the mutant receptor was attenuated by inhibition of protein kinase C, whereas the chemotaxis of cells expressing the wild-type beta-receptor was less affected. Moreover, the PDGF-BB-stimulated tyrosine phosphorylation of phospholipase C-gamma was increased in the mutant receptor cells compared with wild-type receptor cells. In conclusion, the characteristics of the Y934F mutant suggest that the phosphorylation of Tyr934 by Src negatively modulates a signal transduction pathway leading to motility responses which involves phospholipase C-gamma, and shifts the response to increased mitogenicity.
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| 3. |
- Heldin, Carl-Henrik, et al.
(författare)
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Platelet-derived growth factor : isoform-specific signalling via heterodimeric or homodimeric receptor complexes
- 1992
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Ingår i: Kidney International. - : Elsevier BV. - 0085-2538 .- 1523-1755. ; 41:3, s. 571-574
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Growth factors are polypeptides that are involved in the regulation of cell growth and differentiation, such as, during the embryonal development, in wound healing, in hematopoiesis, in the immune response, as well as in several adverse reactions including malignancies. Several families of structurally-related growth factors are known; new members of these families continue to be discovered and occasionally new families are found. One of the best characterized growth factor family is the platelet-derived growth factor (PDGF) family. PDGF was originally found to be present in the alpha-granules of platelets and to have growth promoting activity for fibroblasts and smooth muscle cells; subsequent studies have shown that PDGF is synthesized by a large number of different normal as well as transformed cell types, and that it acts not only on connective tissue cells but also on other types of cells [reviewed in 1, 2]. The present review summarizes some recent developments in the elucidation of the structural and functional properties of PDGF and PDGF receptors, the mechanism for PDGF signalling at the cellular level and the possible in vivo effects of PDGF.
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| 4. |
- Rupp, Eva, et al.
(författare)
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A unique autophosphorylation site in the platelet-derived growth factor alpha receptor from a heterodimeric receptor complex
- 1994
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Ingår i: European Journal of Biochemistry. - 0014-2956 .- 1432-1033. ; 225:1, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- The platelet-derived growth factor (PDGF) alpha and beta receptors undergo dimerization as a consequence of ligand binding. Depending on the PDGF isoform (PDGF-AA, -AB or -BB), homodimers or heterodimers of receptors are formed. In this study, we have used transfected porcine aortic endothelial cells, coexpressing cDNAs for the alpha receptor and the beta receptor at comparable levels, to investigate the properties of the alpha beta-heterodimeric receptor complex. PDGF-AB, which mainly induced alpha beta-heterodimeric complexes, was the most efficient isoform for stimulating mitogenicity. Actin reorganization, in the form of circular membrane ruffling and chemotaxis, was induced by PDGF-AB and PDGF-BB, but not by PDGF-AA, thus indicating that the beta receptor in the homodimeric or heterodimeric configuration was required for induction of motility responses. The molecular basis for the apparent receptor dimer-specific properties was examined by analyzing receptor autophosphorylation and phosphorylation of substrates. The alpha receptor was found to be phosphorylated at an additional tyrosine residue, Tyr754, in the heterodimeric complex as compared to the alpha alpha receptor homodimer. Phosphorylation of this tyrosine residue could permit the binding of a specific signal-tranducing protein. A candidate is a 134,000-M(r) protein, which was shown to associate preferentially with the alpha receptor in the heterodimeric receptor complex. It is possible that phosphorylated Tyr754 in the alpha receptor mediates activation of specific signal-tranducing molecules like the 134,000-M(r) substrate, and thereby initiates signal-tranduction pathways from the alpha beta receptor heterodimer, which are distinct from those initiated via homodimeric receptor complexes.
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| 5. |
- Rönnstrand, Lars, et al.
(författare)
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Overactivation of phospholipase C-gamma1 renders platelet-derived growth factor beta-receptor-expressing cells independent of the phosphatidylinositol 3-kinase pathway for chemotaxis
- 1999
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Ingår i: Journal of Biological Chemistry. - : Elsevier BV. - 0021-9258 .- 1083-351X. ; 274:31, s. 22089-22094
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that porcine aortic endothelial cells expressing the Y934F platelet-derived growth factor (PDGF) beta-receptor mutant respond to PDGF-BB in a chemotaxis assay at about 100-fold lower concentration than do wild-type PDGF beta-receptor-expressing cells (Hansen, K., Johnell, M., Siegbahn, A. , Rorsman, C., Engström, U., Wernstedt, C., Heldin, C.-H., and Rönnstrand, L. (1996) EMBO J. 15, 5299-5313). Here we show that the increased chemotaxis correlates with increased activation of phospholipase C-gamma1 (PLC-gamma1), measured as inositol-1,4, 5-trisphosphate release. By two-dimensional phosphopeptide mapping, the increase in phosphorylation of PLC-gamma1 was shown not to be selective for any site, rather a general increase in phosphorylation of PLC-gamma1 was seen. Specific inhibitors of protein kinase C, bisindolylmaleimide (GF109203X), and phosphatidylinositol 3-kinase (PI3-kinase), LY294002, did not affect the activation of PLC-gamma1. To assess whether increased activation of PLC-gamma1 is the cause of the hyperchemotactic behavior of the Y934F mutant cell line, we constructed cell lines expressing either wild-type or a catalytically compromised version of PLC-gamma1 under a tetracycline-inducible promoter. Overexpression and concomitant increased activation of wild-type PLC-gamma1 in response to PDGF-BB led to a hyperchemotactic behavior of the cells, while the catalytically compromised PLC-gamma1 mutant had no effect on PDGF-BB-induced chemotaxis. Furthermore, in cells expressing normal levels of PLC-gamma1, chemotaxis was inhibited by LY294002. In contrast, the increase in chemotactic response seen upon overexpression of PLC-gamma1 was not inhibited by the PI3-kinase inhibitor LY294002. These observations suggest the existence of two different pathways which mediate PDGF-induced chemotaxis; depending on the cellular context, the PI3-kinase pathway or the PLC-gamma1 pathway may dominate.
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| 6. |
- Siegbahn, Agneta, et al.
(författare)
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Regulation of chemotaxis by the cytoplasmic domain of tissue factor
- 2005
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Ingår i: Thrombosis and Haemostasis. - 0340-6245 .- 2567-689X. ; 93:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- We previously demonstrated that FVIIa bound to tissue factor (TF) induces a hyperchemotactic response towards PDGF-BB. The aim of the present study was to investigate the role of the cytoplasmic domain of TF in cell migration. Porcine aortic endothelial (PAE) cells expressing human PDGF beta-receptors (PAE/PDGFRbeta) were transfected for expression of human wildtype TF (PAE/PDGFRbeta,TF), a construct lacking the cytoplasmic domain (PAE/PDGFRbeta,TFDeltacyto), a construct with alanine replacement of serine 258 (PAE/PDGFRbeta,TFS258A), or a construct with alanine replacement of serine 253, 258 and 263 in the cytoplasmic domain (PAE/PDGFRbeta,TF3SA). All stably transfected cell lines expressed functional TF. Chemotaxis was analyzed in a modified Boyden chamber assay. PAE/PDGFRbeta,TF cells stimulated with FVIIa migrated towards a 100-fold lower concentration of PDGF-BB than in the absence of FVIIa, however, hyperchemotaxis was not seen in PAE/PDGFRbeta,TFDeltacyto cells. PAE/PDGFRbeta/TFS258A and PAE/PDGFRbeta,TF3SA cells responded to low levels of PDGF-BB, but migrated a significantly shorter distance than PAE/PDGFRbeta,TF cells. Thus, hyperchemotaxis towards PDGF-BB is likely to depend in part on phosphorylation of the cytoplasmic domain of TF. We conclude that the cytoplasmic domain of TF plays a pivotal role in modulating cellular migration response. Our results suggest that the FVIIa/TF complex mediates intracellular signaling by alternative signal transduction pathway(s).
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| 7. |
- Zhang, Yanyu, et al.
(författare)
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Platelet-Specific PDGFB Ablation Impairs Tumor Vessel Integrity and Promotes Metastasis
- 2020
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Ingår i: Cancer Research. - : American Association for Cancer Research (AACR). - 0008-5472 .- 1538-7445. ; 80:16, s. 3345-3358
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Tidskriftsartikel (refereegranskat)abstract
- Platelet-derived growth factor B (PDGFB) plays a crucial role in recruitment of PDGF receptor b-positive pericytes to blood vessels. The endothelium is an essential source of PDGFB in this process. Platelets constitute a major reservoir of PDGFB and are continuously activated in the tumor microenvironment, exposing tumors to the plethora of growth factors contained in platelet granules. Here, we show that tumor vascular function, as well as pericyte coverage is significantly impaired in mice with conditional knockout of PDGFB in platelets. A lack of PDGFB in platelets led to enhanced hypoxia and epithelial-to-mesenchymal transition in the primary tumors, elevated levels of circulating tumor cells, and increased spontaneous metastasis to the liver or lungs in two mouse models. These findings establish a previously unknown role for platelet-derived PDGFB, whereby it promotes and maintains vascular integrity in the tumor microenvironment by contributing to the recruitment of pericytes. Significance: Conditional knockout of PDGFB in platelets demonstrates its previously unknown role in the maintenance of tumor vascular integrity and host protection against metastasis.
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| 8. |
- Åberg, Mikael, 1978-
(författare)
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Tissue Factor Biological Functions : Coagulation Activity in Microparticles and Signaling with Focus On Migration and Apoptosis
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Tissue factor (TF) is a 47 kDa transmembrane glycoprotein known as the main initiator of blood coagulation. TF is over-expressed on many malignant cells and apart from increasing the risk of thrombosis, the presence of TF/FVIIa also promotes the progression of cancer and metastasis by intracellular signaling. TF expressing microparticles (MP) are, moreover, often found in the circulation of cancer patients.Aim: The aim of this thesis was to study different aspects of TF activity, e.g. the importance of procoagulant MP and TF-induced intracellular signaling pathways, with focus on cell migration (chemotaxis) and apoptosis.Results: The TF signaling complexes were shown to prevent apoptosis induced by serum starvation and TRAIL in cancer cells by reduced activation of caspase-8 in a PI3k/AKT-dependent manner. FVIIa also decreased transcription of pro-apoptotic genes in cancer cells treated with TRAIL. Simvastatin triggered apoptosis by transcriptional reduction of BCL-2 due to cytosolic retention of NFκB. Simvastatin also inactivated the PI3k/AKT pathway and reduced the production of the MP-like prostasomes which, respectively, impaired the anti-apoptotic signaling by TF and reduced the procoagulant activity in the vicinity of prostate cancer cells. Intracellular events conducted by the TF/FVIIa complex selectively enhanced PDGF-BB induced chemotaxis which was partly explained by the TF/FVIIa-induced transactivation of the PDGFβ-receptor. This was dependent on Src-family members and engagement of PAR2.Conclusions: The results presented in this thesis extend the current knowledge of TF-mediated signaling. We report the TF complexes to govern the extrinsic pathway of apoptosis, present data on FVIIa-dependent regulation of apoptosis-related genes, and exclude known surface proteins as transmitters of the anti-apoptotic signals. We moreover describe TF/FVIIa to transactivate the PDGFβ-receptor and play a decisive role in the potentiated chemotaxis toward PDGF-BB in a number of cell types. Finally, we explain the mechanism behind simvastatin-induced apoptosis in cancer cells and how statins interfere with TF-dependent signaling and coagulation.
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