Divergent roles for ferric ions in the biological activity of amidated and non-amidated gastrins
Divergent roles for ferric ions in the biological activity of amidated and non-amidated gastrins
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DOI：
10.1677/joe.0.1810315
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发表时间：
2004-05-01
影响因子：
4
通讯作者：
Baldwin, GS
中科院分区：
文献类型：
--
作者：
Pannequin, J;Tantiongco, JP;Baldwin, GS
肽激素胃泌素的修饰形式通过胆囊收缩素-2受体刺激胃酸分泌，而非修饰形式通过一种新的，尚未表征的受体刺激结肠粘膜增殖。核磁共振（NMR）和荧光光谱研究表明甘氨酸延伸胃泌素17结合两个铁离子，铁离子结合是生物活性所必需的。因此，我们研究了铁离子在修饰胃泌素的生物活性中的作用17。与甘氨酸延伸的胃泌素17一样，荧光猝灭实验表明，修饰胃泌素17的Glu7 Ala和Glu8、9 Ala突变体各自只结合一个铁离子。突变肽在转染的COS-7细胞或t淋巴母细胞Jurkat细胞上对胆囊收缩素-2受体的亲和力，以及它们在刺激Jurkat细胞增殖和转染的COS-7细胞中肌醇磷酸产生方面的效力，与修饰的胃泌素获得的值相似。此外，铁螯合剂去铁胺没有显著抑制修饰胃泌素17与胆囊收缩素-2受体的结合，也没有显著抑制修饰胃泌素17对转染COS-7细胞中肌醇磷酸产生的刺激。我们得出结论，与甘氨酸延伸胃泌素17相反，铁离子的结合对修饰胃泌素17的生物活性不是必需的。我们的研究结果支持了修饰胃泌素和非修饰胃泌素不同作用模式的概念，并提高了开发非修饰胃泌素和修饰胃泌素选择性拮抗剂的可能性。
Amidated forms of the peptide hormone gastrin act via the cholecystokinin-2 receptor to stimulate gastric acid secretion, whereas non-amidated forms stimulate colonic mucosal proliferation via a novel, as yet uncharacterised, receptor. Nuclear magnetic resonance (NMR) and fluorescence spectroscopic studies have revealed that glycine-extended gastrin17 bound two ferric ions, and that ferric ion binding was essential for biological activity. We have therefore investigated the role of ferric ions in the biological activity of amidated gastrin17. As with glycine-extended gastrin17, fluorescence quenching experiments indicated that Glu7 Ala and Glu8,9 Ala mutants of amidated gastrin17 each bound only one ferric ion. The affinity of the mutant peptides for the cholecystokinin-2 receptor on transfected COS-7 cells or on T-lymphoblastoid Jurkat cells, and their potency in stimulation of proliferation in Jurkat cells and inositol phosphate production in transfected COS-7 cells, were similar to the values obtained for amidated gastrin17. In addition, the iron chelator desferrioxamine did not significantly inhibit either binding of amidated gastrin17 to the cholecystokinin-2 receptor, or stimulation of inositol phosphate production by amidated gastrin17 in transfected COS-7 cells. We conclude that, in contrast to glycine-extended gastrin 17, binding of ferric ions is not essential for the biological activity of amidated gastrin17. Our results support the concept of distinct modes of action for amidated and non-amidated gastrins, and raise the possibility of developing selective antagonists of the actions of non-amidated and amidated gastrins.