INSULIN-LIKE GROWTH-FACTOR (IGF)-II BINDING TO IGF-BINDING PROTEINS AND IGF RECEPTORS IS MODIFIED BY DELETION OF THE N-TERMINAL HEXAPEPTIDE OR SUBSTITUTION OF ARGININE FOR GLUTAMATE-6 IN IGF-II
INSULIN-LIKE GROWTH-FACTOR (IGF)-II BINDING TO IGF-BINDING PROTEINS AND IGF RECEPTORS IS MODIFIED BY DELETION OF THE N-TERMINAL HEXAPEPTIDE OR SUBSTITUTION OF ARGININE FOR GLUTAMATE-6 IN IGF-II
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DOI：
10.1042/bj2930713
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发表时间：
1993-08-01
影响因子：
4.1
通讯作者：
WALLACE, JC
中科院分区：
文献类型：
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作者：
FRANCIS, GL;APLIN, SE;WALLACE, JC
重组胰岛素样生长因子-II（IGF-II）和两个结构类似物，des（1-6）IGF-II和[Arg 6]-IGF-II，被生产，以研究N-末端残基在结合IGF-binding proteins（IGFBPs）中的作用，从而修饰肽的生物学特性。生长因子以IGF-I的两种先前表征的变体des（1-3）IGF-I和[Arg 3]-IGF-I为模型，这两种变体均显示出与IGFBP的结合显著降低，并在大肠杆菌中表达为融合蛋白。比较了IGF-I和IGF-II相应类似物在大鼠L 6成肌细胞和H35 B肝癌细胞中的生物活性。在L 6-成肌细胞蛋白合成试验中，IGF-II类似物des（1-6）IGF-II和[Arg 6]-IGF-II的效力略高于IGF-II，但比IGF-I的效力低约10倍，比相应的IGF-I类似物des（1-3）IGF-I和[Arg 3]-IGF-I的效力低约100倍。在H35肝癌细胞中，测定的合成代谢反应是抑制蛋白质分解，并且效力顺序为胰岛素>[Arg 3]-IGF-I > des（I-3）IGF-I > [Arg 6]-IGF-II > des（1-6）IGF-II > IGF-I > IGF-II。IGF及其类似物与L 6成肌细胞中的1型IGF受体和H35肝癌细胞中的胰岛素受体的结合并不能完全解释所观察到的合成代谢效力差异。此外，与亲本IGF相比，所有四种类似物与L 6成肌细胞和H35 B肝癌细胞分泌的IGFBPs的结合大大降低。我们得出结论，所观察到的合成代谢反应，每一个IGF的确定其相对结合的竞争细胞受体和IGFBP结合位点存在。
Recombinant insulin-like growth factor-II (IGF-II) and two structural analogues, des(1-6)IGF-II and [Arg6]-IGF-II, were produced to investigate the role of N-terminal residues in binding to IGF-binding proteins (IGFBPs) and hence the biological properties of the modified peptides. The growth factors were modelled on two previously characterized variants of IGF-I, des(1-3)IGF-I and [Arg3]-IGF-I, which both show substantially decreased binding to IGFBPs and were expressed as fusion proteins in Eschericia coli. The biological activities of the corresponding analogues of IGF-I and IGF-II were compared in rat L6 myoblasts and H35B hepatoma cells. In the L6-myoblast protein-synthesis assay, the IGF-II analogues, des(1-6)IGF-II and [Arg6]-IGF-II, were slightly more potent than IGF-II but about 10-fold less potent than IGF-I and 100-fold less potent than the respective IGF-I analogues, des(1-3)IGF-I and [Arg3]-IGF-I. In H35 hepatoma cells the anabolic response measured was the inhibition of protein breakdown, and the potency order was insulin much greater than [Arg3]-IGF-I > des(I-3)IGF-I > [Arg6]-IGF-II > des(1-6)IGF-II > IGF-I > IGF-II. Binding of the IGFs and their analogues to the type 1 IGF receptor in L6 myoblasts and to the insulin receptor in H35 hepatoma cells did not fully explain the observed anabolic potency differences. Moreover, binding of all four analogues to the IGFBPs secreted by L6 myoblasts and H35B hepatoma cells was greatly decreased compared with the parent IGF. We conclude that the observed anabolic response to each IGF was determined by their relative binding to the competing cell receptor and IGFBP binding sites present.