血管内皮细胞生长抑制因子N端部分缺失对生物活性的影响

血管内皮细胞生长抑制因子 (vascularendothelialcellgrowthinhibitor,VEGI)是近年来发现的一类TNF家族新成员 ,具有抑制内皮细胞增殖与新血管生成的作用。为了探讨VEGI蛋白N端对其活性的影响 ,进行了VEGI与TNF家族成员基于结构知识的一级结构序列联配 ,在此基础上构建、表达了N端缺失 43与 5 1个氨基酸的VEGI突变体。N端缺失 43个氨基酸的VEGI(VEGI131)表达量占总菌体蛋白质的 2 5 .2 % ,N端缺失 5 1个氨基酸的VEGI(VE GI12 3)表达量为 2 7.8% ,纯化后纯度分别为 92 .5 % (VEGI131)和 91.6 % (VEGI12 3)。VEGI131可明显抑制人脐静脉内皮细胞 (HUVEC)增殖 ,IC50 约为 35mg/L ,而VEGI12 3在同样条件下几乎无抑制作用 ,野生型VEGI即N端缺失 2 3个氨基酸的VEGI(VEGI151,由作者实验室制备 )IC50 约为 2 7mg/L。鸡胚绒毛尿囊膜血管生成实验证明 ,VEGI151可使主血管数显著减少 ,VEGI131可使主血管变细 ,毛细血管数减少 ,而VEGI12 3 与对照组相比无明显变化。体内外研究显示VEGI活性从高到低依次为 :VEGI151>VEGI131>VEGI12 3。结果提示 :VEGI的N端前 43个氨基酸对活性无明显影响 ,而第 44～ 5 1位氨基酸对其生物活性的发挥具有重要作用。

Effect of N-terminal Deletion on Biological Activity of Vascular Endothelial Cell Growth Inhibitor

Vascular endothelial cell growth inhibitor (VEGI) is a novel cytokine which belongs to the TNF superfamily. It can inhibit the proliferation of endothelial cells and neovascularization. Howevor, little is known about the structure-function relationship of VEGI. In order to study the effect of the N-terminus of VEGI on biological properties, the sequence alignament among VEGI and TNF superfamily members based on structure knowledge was done, and then two truncated forms of VEGI were constructed, in which 43 and 51 amino acids from N-terminus were deleted and named VEGI 131 and VEGI 123. Recombinant proteins were generated from E.coli. The expression rates were 25.2% (VEGI 131) and 27.8% (VEGI 123) of total bacterial proteins. After purification the purity reached 92.5% (VEGI 131) and 91.6% (VEGI 123). VEGI 131 showed significant inhibitory effect on growth of human umbilical vein endothelial cells (HUVEC), IC 50 of VEGI 131 being 35 mg/L. Under the same conditions, IC 50 of VEGI 151 (the wild type of VEGI) was 27 mg/L, but VEGI 123 showed no inhibitory effect. On chick choriallantic membrane (CAM ) assay, VEGI 151 markedly reduced the number of main vessels, and VEGI 131 decreased capillary number, while the effect of VEGI 123 was almost the same as control. These results suggest that the first 43 amino acids from N-terminus of VEGI have no significant effect on biological activity, but the amino acids 44-51 at N-terminus are required for full biological activity.