Shen H, Clauss M, Ryan J, Schmidt A M, Tijburg P, Borden L, Connolly D, Stern D, Kao J
Department of Physiology, Columbia University-College of Physicians and Surgeons, New York, NY 10032.
Blood. 1993 May 15;81(10):2767-73.
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.
血管通透因子/血管内皮生长因子（VPF/VEGF）是一种由某些肿瘤和其他细胞类型产生的多肽介质，它通过与一类高亲和力结合位点相互作用，对内皮细胞产生多种影响。在本报告中，对VPF/VEGF与人类单核吞噬细胞（MPs）的相互作用进行了表征。4℃下的放射性配体结合研究表明存在一类单一的结合位点，解离常数（kd）约为300至500 pmol/L（亲和力比内皮细胞[ECs]上的高亲和力结合位点低约20倍），其占有率与VPF/VEGF诱导的MP迁移和组织因子表达相关。这些结合结果与功能实验结果一致，功能实验表明相同的VPF/VEGF制剂在刺激MP趋化性方面的效力比诱导EC增殖低约一个数量级。当表面结合有125I-VPF/VEGF的MPs升温至37℃时，会发生内吞作用和降解。VPF/VEGF结合位点的占有率导致细胞内信号转导机制随后被激活，这表现为MP细胞内钙浓度的增加。用125I-VPF/VEGF进行的交联研究显示出一条新的高分子量条带（对应于假定的125I-VPF/VEGF-受体复合物），过量未标记的VPF/VEGF可阻断其出现。与这些结果一致，对暴露于VPF/VEGF的32PO4标记的MPs进行免疫沉淀显示出一条迁移率相似的单一条带，在未处理的对照中未见此条带。这些结果表明，VPF/VEGF与MPs的相互作用虽然亲和力低于与ECs的相互作用，但也是该多肽与特定细胞表面蛋白相互作用的结果，并导致细胞内转导机制的激活。
