Molecular Cancer Biology Program, Biomedicum Helsinki, Department of Pathology, Haartman Institute and Helsinki University Central Hospital, PO Box 63, University of Helsinki, Haartmaninkatu 8, FI-00014 Helsinki, Finland.
Proc Natl Acad Sci U S A. 2010 Feb 9;107(6):2425-30. doi: 10.1073/pnas.0914318107.
Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel formation through activation of three receptor tyrosine kinases, VEGFR-1, -2, and -3. The extracellular domain of VEGF receptors consists of seven immunoglobulin homology domains, which, upon ligand binding, promote receptor dimerization. Dimerization initiates transmembrane signaling, which activates the intracellular tyrosine kinase domain of the receptor. VEGF-C stimulates lymphangiogenesis and contributes to pathological angiogenesis via VEGFR-3. However, proteolytically processed VEGF-C also stimulates VEGFR-2, the predominant transducer of signals required for physiological and pathological angiogenesis. Here we present the crystal structure of VEGF-C bound to the VEGFR-2 high-affinity-binding site, which consists of immunoglobulin homology domains D2 and D3. This structure reveals a symmetrical 22 complex, in which left-handed twisted receptor domains wrap around the 2-fold axis of VEGF-C. In the VEGFs, receptor specificity is determined by an N-terminal alpha helix and three peptide loops. Our structure shows that two of these loops in VEGF-C bind to VEGFR-2 subdomains D2 and D3, while one interacts primarily with D3. Additionally, the N-terminal helix of VEGF-C interacts with D2, and the groove separating the two VEGF-C monomers binds to the D2/D3 linker. VEGF-C, unlike VEGF-A, does not bind VEGFR-1. We therefore created VEGFR-1/VEGFR-2 chimeric proteins to further study receptor specificity. This biochemical analysis, together with our structural data, defined VEGFR-2 residues critical for the binding of VEGF-A and VEGF-C. Our results provide significant insights into the structural features that determine the high affinity and specificity of VEGF/VEGFR interactions.
血管内皮生长因子 (VEGFs) 通过激活三个受体酪氨酸激酶 VEGFR-1、-2 和 -3 来调节血液和淋巴管的形成。VEGF 受体的细胞外结构域由七个免疫球蛋白同源结构域组成，这些结构域在配体结合后促进受体二聚化。二聚化启动跨膜信号转导，激活受体的细胞内酪氨酸激酶结构域。VEGF-C 通过 VEGFR-3 刺激淋巴管生成，并有助于病理性血管生成。然而，蛋白水解处理的 VEGF-C 也刺激 VEGFR-2，VEGFR-2 是生理和病理性血管生成所需信号的主要转导器。在这里，我们展示了与 VEGFR-2 高亲和力结合位点结合的 VEGF-C 的晶体结构，该结合位点由免疫球蛋白同源结构域 D2 和 D3 组成。该结构揭示了一个对称的 22 复合物，其中左手扭曲的受体结构域围绕 VEGF-C 的 2 倍轴缠绕。在 VEGFs 中，受体特异性由 N 端α螺旋和三个肽环决定。我们的结构表明，VEGF-C 的两个环与 VEGFR-2 的 D2 和 D3 亚结构域结合，而一个环主要与 D3 结合。此外，VEGF-C 的 N 端螺旋与 D2 相互作用，而将两个 VEGF-C 单体分开的凹槽与 D2/D3 接头结合。VEGF-C 与 VEGF-A 不同，不与 VEGFR-1 结合。因此，我们创建了 VEGFR-1/VEGFR-2 嵌合蛋白来进一步研究受体特异性。这种生化分析，以及我们的结构数据，定义了 VEGFR-2 残基对于 VEGF-A 和 VEGF-C 结合的关键作用。我们的研究结果为确定 VEGF/VEGFR 相互作用的高亲和力和特异性的结构特征提供了重要的见解。
