摘要:

AbstractFetal liver kinase-1 (Flk-1) is a transmembrane tyrosine kinase that was identified in endothelial cells and populations of cells enriched in hematopoietic progenitors. To characterize the interaction of Flk-1 with potential ligands the receptor extracellular domain was genetically fused to an alkaline phosphatase (AP) tag. A soluble ligand for Flk-1 was identified in the supernatants of numerous mesenchymal cell lines by co-immunoprecipitation with the Flk1-AP fusion protein. This polypeptide was shown by N-terminal sequencing to be vascular endothelial growth factor (VEGF). Receptor-AP fusion proteins can thus be used to identify soluble ligands as well as transmembrane ligands, and this approach is therefore likely to be widely applicable to many types of orphan receptor. The Flk1-AP soluble receptor was also found to bind to cell surfaces, showing two apparent classes of binding site with different affinities. This interaction could be reconstructed by introducing a VEGF expression plasmid into cells. These results indicate that VEGF presented at the cell surface can bind to the Flk-1 receptor, and could mediate a direct cell-cell interaction. The Flk1-AP fusion protein was also found to bind heparin, implying that ligand binding by the Flk-1 receptor may involve a three way interaction between the Flk-1 receptor, VEGF, and heparin-like cell surface proteoglycans.

ISSN:0897-7194    

DOI:10.3109/08977199509003208

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractVascular endothelial growth factor (VEGF)/vascular permeability factor (VPF), exists as multiple forms due to alternative splicing of mRNA. VEGF165/164(human/rodent homologue) is often assumed to be the predominant form, although truly quantitative assessments are lacking. We have used the RNase protection assay to directly quantitate the relative abundance of VEGF mRNA forms in five rat tissues (brain, kidney, lung, spleen, and heart) and two rat glioma cell lines (C6 and 9L). The three major forms, which code for proteins of 188, 164, and 120 amino acids, were observed in all of the tissues and cells examined. However, the relative abundance differed among the samples. VEGF188was the predominant form (>50% of total VEGF mRNA) in heart and lung, but was the least abundant form (6–15%) in all other samples. VEGF164was lower (∼25%) in heart and lung, but was predominant (>50%) in brain and kidney. VEGF164and VEGF120were present in equimolar amounts (each form∼46% of total) in the spleen, C6, and 9L. VEGF120, was also present in kidney (38%) and lung (27%) and was least abundant (∼15%) in brain and heart. A rat homologue of VEGF206was not observed. VEGF mRNA splicing occurs in a tissue-specific manner. The assumption that the predominant physiologic form of VEGF is a VEGF165/164homodimer should be viewed with caution.

ISSN:0897-7194    

DOI:10.3109/08977199509003209

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractVascular endothelial growth factor (VEGF) is a glycoprotein consisting of two identical polypeptide chains linked by a disulfide bond. The unique biological activities of VEGF include its potent mitogenic and permeability inducing properties specific for the vascular endothelium. VEGF is implicated in tumor angiogenesis, wound healing, and the stimulation of collateral vessel formation at the site of arterial occlusion. Therefore, in order to produce large quantities of biologically active VEGF, a splice variant (VEGF165) was cloned and expressed in a yeast expression system. The coding region of VEGF165was isolated from U937 cells by RT-PCR, sequenced and then cloned into the yeast expression vector pHILS1. VEGF165was secreted into the medium as a dimer. Recombinant VEGF reacted to antibodies raised against the N-terminal and C-terminal synthetic polypeptides of human VEGF. As much as 35–40 mg/L of purified VEGF could be obtained from the yeast expression system. The recombinant protein was biologically active in inducing vascular endothelial cell proliferationin vitroand permeability changesin vivo.

ISSN:0897-7194    

DOI:10.3109/08977199509003210

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractKaposi's fibroblast growth factor (K-FGF, FGF-4) is a newer member of FGF family with uncharacterized wound healing properties. Basic fibroblast growth factor (bFGF, FGF-2) has been well studied and accelerates repair in normal and impaired wound healing models. K-FGF and bFGF are known to have similar biological effects in tissue culture, and both stimulate fibroblast and endothelial cell proliferation. The rabbit dermal ulcer model was used to examine the effects of bFGF and K-FGF under ischemic and nonischemic conditions. We found bFGF was ineffective in stimulating healing under ischemic conditions even at high doses (30μg/wound). However, when the ischemic wounds were treated with bFGF (5μg/wound) plus hyperbaric oxygen therapy, it was highly effective again as previously found under nonischemic conditions (P<0.05). In contrast K-FGF stimulated repair in both nonischemic and ischemic wounds (P<0.05). These results suggest that wound oxygen content differentially regulates responsiveness to bFGF and that K-FGF is biologically active in hypoxic wounds.

ISSN:0897-7194    

DOI:10.3109/08977199509003211

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThe progressive growth of solid tumors is dependent on the tumor ability to recruit new blood vessels from the surrounding host tissues. We show here that acidic Fibroblast Growth Factor (FGF-1) produced by a rat bladder carcinoma transfected cell line (NBT-II cells) is a potent inducer of angiogenesis. After injection in nude mice, NBT-II cells transfected with FGF-1 form rapidly growing carcinomas which are highly vascularized, whereas carcinoma cells producing a biologically active form of FGF-4 behave like non-producer cells. The vasculature of the tumors obtained with NBT-II cells producing a secreted form of FGF-1 is dramatically expanded but lacking in some places a complete endothelial lining. Conditioned medium from these cells induce formation of capillary-like structuresin vitro, whereas those of FGF-4 and non-secreting FGF-1 producing cells failed to induce such structures.Our results indicate that the expression of FGF-1 may promote tumor growth, at least in part, by inducing angiogenesis, and that the acquired ability of tumor cells to secrete FGF-1 but not FGF-4, may result in aberrant neovascularization of the tumor.

ISSN:0897-7194    

DOI:10.3109/08977199509003212

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractFibroblast growth factors (FGF) are expressed at high levels in the central nervous system (CNS), however their function in the CNS is not well understood. The immortalized neuronal cell line (BK1), derived from a transgenic mouse central nervous system tumor, expresses high levels of FGF receptor 1 (FGFR1) and demonstrates both morphologic and biochemical changes when treated with basic FGF (FGF-2). We have derived subclones of BK1 cells with varying degrees of FGF responsiveness by transfecting either a wild type (FRW) or a truncated (FRX) form of FGFR1. Cells expressing high levels of FGFR1 rapidly and uniformly respond to FGF, while cells expressing FRX fail to respond to FGF, either morphologically or by the expression of molecular markers. These BK1 subclones will prove useful to study FGFR mediated signal transduction and FGFR responsive genes in a CNS derived cell. These studies also demonstrate that a dominant negative FGF receptor can be used as a tool to elucidate the function of FGF in the central nervous system.

ISSN:0897-7194    

DOI:10.3109/08977199509003213

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractStem cell factor (SCF) promotes limited proliferation and differentiation of hematopoietic progenitor cells and is potently synergistic in combination with growth factors such as granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3) or erythropoietin (Epo). We have examined tyrosine phosphorylation induced by SCF in the megakaryoblastic cell line Mo7e and found phosphorylation of proteins of 200, 145, 120, 58 and 55 KDa. The dominant phosphotyrosylproteins in SCF treated cells were 200 and 145 kDa. Our studies indicated that the 145 kDa protein was c-kit, the receptor for SCF. Subsequent work was directed towards further characterizing the 200 kDa protein. Surface labeling of Mo7e cells suggested that p200 had an extracellular domain and could be induced to associate with c-kit after stimulation with SCF. The rapid phosphorylation of p200 and its immediate association with c-kit suggest that p200 is potentially a component of the SCF signal transduction pathway.

ISSN:0897-7194    

DOI:10.3109/08977199509003214

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractA single-amino-acid substitution mutant form of human interleukin-4 (hIL-4), Y124D.hIL-4, has been described previously as an antagonist of the effects of hIL-4 on various human cells. The murine T-cell leukemic cell line CT.MS, which expresses the human IL-4 receptor, proliferates in response to both hIL-4 and murine IL-4. Although Y124D.hIL-4 antagonizes the proliferative effects of hIL-4 on human phytohaemagglutinin-stimulated peripheral blood mononuclear cells, Y124D.hIL-4 is a potent stimulator for CT.h4S cells. Molecular modelling studies were performed to investigate the stability of different conformations of residue 124 as well as the efficiency of different molecular mechanics force fields in homology modelling. We suggest that the aspartate substitution alters the C-terminal end of the D-helix in such way that the analogue still binds to the human IL-4 receptorα-chain and signals through the murineγc-chain. In contrast, the Y124D.hIL-4/ IL-4 receptor complex cannot signal through the humanγc-chain.

ISSN:0897-7194    

DOI:10.3109/08977199509003215

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractPolyfunctionality of Hemopoietic Regulators: The Metcalf ForumEd. MARTIN J. MURPHY AlpkaMed Press

ISSN:0897-7194    

DOI:10.3109/08977199509003216

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor