Charité-Universitaetsmedizin Berlin, Medizinische Klinik IV, Hindenburgdamm 30, D-12200, Berlin, Germany.
J Mol Med (Berl). 2013 Sep;91(9):1095-107. doi: 10.1007/s00109-013-1036-y. Epub 2013 May 1.
The group of dinucleoside polyphosphates encompasses a large number of molecules consisting of two nucleosides which are connected by a phosphate chain of variable length. While the receptors activated by dinucleoside polyphosphates as well as their degradation have been studied in detail, its biosynthesis has not been elucidated so far. Since endothelial cells released the dinucleoside polyphosphate uridine adenosine tetraphosphate (Up4A), we tested cytosolic proteins of human endothelial cells obtained from dermal vessels elicited for enzymatic activity. When incubated with ADP and UDP, these cells showed increasing concentrations of Up4A. The underlying enzyme was isolated by chromatography and the mass spectrometric analysis revealed that the enzymatic activity was caused by the vascular endothelial growth factor receptor 2 (VEGFR2). Since VEGFR2 but neither VEGFR1 nor VEGFR3 were capable to synthesise dinucleoside polyphosphates, Tyr-1175 of VEGFR2 is most likely essential for the enzymatic activity of interest. Further, VEGFR2-containing cells like HepG2, THP-1 and RAW264.7 were capable of synthesising dinucleoside polyphosphates. VEGFR2-transfected HEK 293T/17 but not native HEK 293T/17 cells synthesised dinucleoside polyphosphates in vivo too. The simultaneous biosynthesis of dinucleoside polyphosphates could amplify the response to VEGF, since dinucleoside polyphosphates induce cellular growth via P2Y purinergic receptors. Thus the biosynthesis of dinucleoside polyphosphates by VEGFR2 may enhance the proliferative response to VEGF. Given that VEGFR2 is primarily expressed in endothelial cells, the biosynthesis of dinucleoside polyphosphates is mainly located in the vascular system. Since the vasculature is also the main site of action of dinucleoside polyphosphates, activating vascular purinoceptors, blood vessels appear as an autocrine system with respect to dinucleoside polyphosphates. We conclude that VEGFR2 receptor is capable of synthesising dinucleoside polyphosphates. These mediators may modulate the effects of VEGFR2 due to their proliferative effects.
二核苷酸多核苷酸包括大量由两个核苷酸组成的分子，这些核苷酸通过可变长度的磷酸链连接。虽然已经详细研究了二核苷酸多核苷酸激活的受体及其降解，但到目前为止，其生物合成尚未阐明。由于内皮细胞释放二核苷酸多核苷酸尿苷腺苷四磷酸（Up4A），我们测试了从皮肤血管中获得的人内皮细胞的细胞质蛋白，以检测其酶活性。当与 ADP 和 UDP 孵育时，这些细胞显示出 Up4A 的浓度增加。通过色谱法分离出潜在的酶，并通过质谱分析表明，该酶活性是由血管内皮生长因子受体 2（VEGFR2）引起的。由于 VEGFR2 而不是 VEGFR1 或 VEGFR3 能够合成二核苷酸多核苷酸，因此 VEGFR2 的 Tyr-1175 很可能是该酶活性所必需的。此外，像 HepG2、THP-1 和 RAW264.7 这样含有 VEGFR2 的细胞也能够合成二核苷酸多核苷酸。VEGFR2 转染的 HEK 293T/17 细胞而不是天然的 HEK 293T/17 细胞也能够在体内合成二核苷酸多核苷酸。由于二核苷酸多核苷酸通过 P2Y 嘌呤能受体诱导细胞生长，因此二核苷酸多核苷酸的同时生物合成可以放大对 VEGF 的反应。因此，VEGFR2 的二核苷酸多核苷酸生物合成可能增强对 VEGF 的增殖反应。鉴于 VEGFR2 主要在内皮细胞中表达，因此二核苷酸多核苷酸的生物合成主要位于血管系统中。由于脉管系统也是二核苷酸多核苷酸作用的主要部位，激活血管嘌呤能受体，血管在二核苷酸多核苷酸方面表现为自分泌系统。我们得出结论，VEGFR2 受体能够合成二核苷酸多核苷酸。这些介质可能由于其增殖作用而调节 VEGFR2 的作用。
