Chiodelli P, Rezzola S, Urbinati C, Federici Signori F, Monti E, Ronca R, Presta M, Rusnati M
Units of Experimental Oncology and Immunology, University of Brescia, Brescia, Italy.
Units of Biotechnology, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy.
Oncogene. 2017 Nov 23;36(47):6531-6541. doi: 10.1038/onc.2017.243. Epub 2017 Aug 7.
Vascular endothelial growth factor receptor-2 (VEGFR2) is the main pro-angiogenic receptor expressed by endothelial cells (ECs). Using surface plasmon resonance, immunoprecipitation, enzymatic digestion, immunofluorescence and cross-linking experiments with specific sugar-binding lectins, we demonstrated that VEGFR2 bears both α,1-fucose and α(2,6)-linked sialic acid (NeuAc). However, only the latter is required for VEGF binding to VEGFR2 and consequent VEGF-dependent VEGFR2 activation and motogenic response in ECs. Notably, downregulation of β-galactoside α(2,6)-sialyltransferase expression by short hairpin RNA transduction inhibits VEGFR2 α(2,6) sialylation that is paralleled by an increase of β-galactoside α(2,3)-sialyltransferase expression. This results in an ex-novo α(2,3)-NeuAc sialylation of the receptor that functionally replaces the lacking α(2,6)-NeuAc, thus allowing VEGF/VEGFR2 interaction. In keeping with the role of VEGFR2 sialylation in angiogenesis, the α(2,6)-NeuAc-binding lectin Sambucus nigra (SNA) prevents VEGF-dependent VEGFR2 autophosphorylation and EC motility, proliferation and motogenesis. In addition, SNA exerts a VEGF-antagonist activity in tridimensional angiogenesis models in vitro and in the chick-embryo chorioallantoic membrane neovascularization assay and mouse matrigel plug assay in vivo. In conclusion, VEGFR2-associated NeuAc plays an important role in modulating VEGF/VEGFR2 interaction, EC pro-angiogenic activation and neovessel formation. VEGFR2 sialylation may represent a target for the treatment of angiogenesis-dependent diseases.
血管内皮生长因子受体-2（VEGFR2）是内皮细胞（ECs）表达的主要促血管生成受体。通过表面等离子体共振、免疫沉淀、酶消化、免疫荧光以及与特定糖结合凝集素的交联实验，我们证明VEGFR2同时携带α(1, fucose和α(2,6)-连接的唾液酸（NeuAc）。然而，只有后者是VEGF与VEGFR2结合以及随后在ECs中VEGF依赖性VEGFR2激活和促运动反应所必需的。值得注意的是，通过短发夹RNA转导下调β-半乳糖苷α(2,6)-唾液酸转移酶的表达会抑制VEGFR2的α(2,6)唾液酸化，与此同时β-半乳糖苷α(2,3)-唾液酸转移酶的表达增加。这导致受体发生新的α(2,3)-NeuAc唾液酸化，在功能上替代了缺失的α(2,6)-NeuAc，从而允许VEGF/VEGFR2相互作用。与VEGFR2唾液酸化在血管生成中的作用一致，α(2,6)-NeuAc结合凝集素黑接骨木（SNA）可防止VEGF依赖性VEGFR2自磷酸化以及EC的运动、增殖和促运动作用。此外，SNA在体外三维血管生成模型以及体内鸡胚绒毛尿囊膜血管生成试验和小鼠基质胶栓塞试验中发挥VEGF拮抗剂活性。总之，与VEGFR2相关的NeuAc在调节VEGF/VEGFR2相互作用、EC促血管生成激活和新血管形成中起重要作用。VEGFR2唾液酸化可能代表了治疗血管生成依赖性疾病的一个靶点。
