Laboratory of Food and Soft Materials, Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland.
Laboratory of Food and Soft Materials, Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland.
J Biol Chem. 2021 Jan-Jun;296:100584. doi: 10.1016/j.jbc.2021.100584. Epub 2021 Mar 24.
Physical interactions between vascular endothelial growth factor (VEGF), a central player in blood endothelial cell biology, and fibronectin, a major fibrillar protein of the extracellular matrix, are important determinants of angiogenic activity in health and disease. Conditions signaling the need for new blood vessel growth, such as hypoxia and low extracellular pH, increase VEGF-fibronectin interactions. These interactions can be further fine-tuned through changes in the availability of the VEGF-binding sites on fibronectin, regulated by conformational changes induced by heparin and heparan sulfate chains within the extracellular matrix. These interactions may alter VEGF bioavailability, generate gradients, or alter the way VEGF is recognized by and activates its cell-surface receptors. Here, using equilibrium and kinetic studies, we discovered that fibronectin can also interact with the extracellular domain of the VEGF receptor 2 (VEGFR2). The VEGFR2-binding sites on fibronectin show great similarity to the VEGF-binding sites, as they were also exposed upon heparin-induced conformational changes in fibronectin, and the interaction was enhanced at acidic pH. Kinetic parameters and affinities for VEGF and VEGFR2 binding to fibronectin were determined by surface plasmon resonance measurements, revealing two populations of fibronectin-binding sites for each molecule. Our data also suggest that a VEGF/VEGFR2/fibronectin triple complex may be formed by VEGF or VEGFR2 first binding to fibronectin and subsequently recruiting the third binding partner. The formation of such a complex may lead to the activation of distinct angiogenic signaling pathways, offering new possibilities for clinical applications that target angiogenesis.
血管内皮生长因子（VEGF）是血液内皮细胞生物学中的核心分子，与细胞外基质中的主要纤维状蛋白纤维连接蛋白之间的物理相互作用是健康和疾病中血管生成活性的重要决定因素。需要新血管生长的条件（如缺氧和低细胞外 pH）会增加 VEGF-纤维连接蛋白的相互作用。这些相互作用可以通过纤维连接蛋白上 VEGF 结合位点的可用性变化进一步微调，这是由细胞外基质中肝素和硫酸乙酰肝素链诱导的构象变化来调节的。这些相互作用可能会改变 VEGF 的生物利用度、产生梯度或改变 VEGF 被其细胞表面受体识别和激活的方式。在这里，我们使用平衡和动力学研究发现，纤维连接蛋白也可以与血管内皮生长因子受体 2（VEGFR2）的细胞外结构域相互作用。纤维连接蛋白上的 VEGFR2 结合位点与 VEGF 结合位点非常相似，因为它们也在纤维连接蛋白的肝素诱导构象变化中暴露出来，并且在酸性 pH 下相互作用增强。通过表面等离子体共振测量确定了 VEGF 和 VEGFR2 与纤维连接蛋白相互作用的动力学参数和亲和力，揭示了每个分子的两种纤维连接蛋白结合位点群体。我们的数据还表明，VEGF 或 VEGFR2 首先与纤维连接蛋白结合，随后招募第三个结合伴侣，可能会形成 VEGF/VEGFR2/纤维连接蛋白三重复合物。这种复合物的形成可能会导致不同的血管生成信号通路的激活，为针对血管生成的临床应用提供了新的可能性。
