Migdal M, Huppertz B, Tessler S, Comforti A, Shibuya M, Reich R, Baumann H, Neufeld G
Department of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel.
J Biol Chem. 1998 Aug 28;273(35):22272-8. doi: 10.1074/jbc.273.35.22272.
Placenta growth factor (PlGF) belongs to the family of vascular endothelial growth factors (VEGFs). It binds to the flt-1 VEGF receptor but not to the KDR/flk-1 receptor which is thought to mediate most of the angiogenic and proliferative effects of VEGF. Three PlGF isoforms are produced by alternative splicing. PlGF-1 and PlGF-3 differ from PlGF-2 since they lack the exon 6 encoded peptide which bestows upon PlGF-2 its heparin binding properties. Cross-linking experiments revealed that 125I-PlGF-2 binds to two endothelial cell surface receptors in a heparin dependent fashion. The binding of 125I-PlGF-2 to these receptors was inhibited by an excess of PlGF-2 and by the 165-amino acid form of VEGF (VEGF165), but not at all by VEGF121 and very marginally if at all by PlGF-1. The apparent molecular weight and the binding characteristics of these receptors correspond to those of the recently identified VEGF165 specific receptor neuropilin-1, and we therefore conclude that neuropilin-1 is a receptor for PlGF-2. The binding of 125I-PlGF-2 as well as the binding of 125I-VEGF165 to these receptors was inhibited by a synthetic peptide derived from exon 6 of PlGF. Furthermore, the binding of 125I-PlGF-2, but not that of 125I-VEGF165, was also inhibited by a synthetic peptide derived from exon 7 of PlGF. These observations indicate that the peptides encoded by these exons probably participate in the formation of the domain which mediates the binding of PlGF-2 to these receptors. We have also determined, using chemically modified heparin species, that the presence of sulfate moieties on the glucosamine-O-6 and on the iduronic acid-O-2 groups of heparin was required for the potentiation of 125I-PlGF-2 binding to these receptors. To determine if PlGF-2 is able to induce biological responses that are not induced by PlGF-1, we compared the effects of PlGF-1 and PlGF-2 on the migration and proliferation of endothelial cells. Both PlGF forms induced migration of endothelial cells. However, there was no quantitative difference between the response to PlGF-2 and the response to PlGF-1. Furthermore, neither PlGF-1 nor PlGF-2 had any effect upon the proliferation of the endothelial cells.
胎盘生长因子（PlGF）属于血管内皮生长因子（VEGF）家族。它与flt-1血管内皮生长因子受体结合，但不与KDR/flk-1受体结合，后者被认为介导了血管内皮生长因子的大多数血管生成和增殖作用。通过可变剪接产生三种PlGF异构体。PlGF-1和PlGF-3与PlGF-2不同，因为它们缺乏赋予PlGF-2肝素结合特性的外显子6编码肽。交联实验表明，125I-PlGF-2以肝素依赖的方式与两种内皮细胞表面受体结合。过量的PlGF-2和165个氨基酸形式的血管内皮生长因子（VEGF165）可抑制125I-PlGF-2与这些受体的结合，但VEGF121完全不能抑制，PlGF-1即使有抑制作用也非常微弱。这些受体的表观分子量和结合特性与最近鉴定的VEGF165特异性受体神经纤毛蛋白-1相符，因此我们得出结论，神经纤毛蛋白-1是PlGF-2的受体。源自PlGF外显子6的合成肽可抑制125I-PlGF-2以及125I-VEGF165与这些受体的结合。此外，源自PlGF外显子7的合成肽也可抑制125I-PlGF-2的结合，但不能抑制125I-VEGF165的结合。这些观察结果表明，这些外显子编码的肽可能参与了介导PlGF-2与这些受体结合的结构域的形成。我们还使用化学修饰的肝素确定，肝素葡糖胺-O-6和艾杜糖醛酸-O-2基团上存在硫酸基团是增强125I-PlGF-2与这些受体结合所必需的。为了确定PlGF-2是否能够诱导PlGF-1不能诱导的生物学反应，我们比较了PlGF-1和PlGF-2对内皮细胞迁移和增殖的影响。两种PlGF形式均诱导内皮细胞迁移。然而，对PlGF-2的反应与对PlGF-1的反应之间没有定量差异。此外，PlGF-1和PlGF-2对内皮细胞的增殖均无任何影响。
