Characterization of vascular permeability factor/vascular endothelial growth factor receptors on mononuclear phagocytes.
Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) is a polypeptide mediator, elaborated by certain tumors and other cell types, that exerts multiple effects on endothelium via interaction with a class of high-affinity binding sites. In this report, the interaction of VPF/VEGF with human mononuclear phagocytes (MPs) is characterized. Radioligand binding studies at 4 degrees C showed the presence of a single class of binding sites, kd approximately 300 to 500 pmol/L (approximately 20 times lower affinity than the high-affinity binding site on endothelial cells [ECs]), the occupancy of which correlated with VPF/VEGF-induced MP migration and expression of tissue factor. These binding results were paralleled by functional experiments which indicated that the same VPF/VEGF preparations were about an order of magnitude less effective in stimulating MP chemotaxis than in inducing EC proliferation. When MPs with surface-bound 125I-VPF/VEGF were warmed to 37 degrees C, endocytosis and degradation occurred. Occupancy of VPF/VEGF binding site resulted in subsequent activation of intracellular signal transduction mechanisms, as shown by an increase in MP intracellular calcium concentration. Cross-linking studies with 125I-VPF/VEGF showed a new high-molecular weight band (corresponding to putative 125I-VPF/VEGF-receptor complex), the appearance of which was blocked by excess unlabeled VPF/VEGF. Consistent with these results, immunoprecipitation of 32PO4-labeled MPs exposed to VPF/VEGF showed a single band of similar mobility, not seen in untreated controls. These results demonstrate that the interaction of VPF/VEGF with MPs, though of lower affinity than that observed with ECs, also results from interaction of the polypeptide with a specific cell-surface protein and leads to activation of intracellular transduction mechanisms.
Shen
H
H
Department of Physiology, Columbia University-College of Physicians and Surgeons, New York, NY 10032.
Clauss
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M
Ryan
J
J
Schmidt
A M
AM
Tijburg
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P
Borden
L
L
Connolly
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Stern
D
D
Kao
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J
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D016228:Endothelial Growth Factors / Q000097:blood* / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008222:Lymphokines / Q000097:blood* / Q000494:pharmacology*; D008970:Molecular Weight; D009000:Monocytes / Q000378:metabolism* / Q000502:physiology; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011869:Radioligand Assay; D040262:Receptors, Vascular Endothelial Growth Factor; D013997:Time Factors; D014471:Umbilical Veins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D007457:Iodine Radioisotopes; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D011505:Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor