Demolle D, Lecomte M, Boutherin-Falson O, Cragoe E J, Nairn A C, Boeynaems J M
Institute of Interdisciplinary Research, School of Medicine, Université Libre de Bruxelles, Belgium.
Mol Pharmacol. 1990 Jun;37(6):827-32.
5-(N-Ethyl-N-isopropyl)amiloride (EIPA), a potent inhibitor of Na+/H+ antiport, reduced [35S]methionine incorporation in proteins and induced the phosphorylation of a Mr 95,000 protein in bovine aortic endothelial cells. This protein was previously shown to become phosphorylated in response to ATP, bradykinin, and A23187 (1) and was identified as elongation factor-2 (2). The action of EIPA was independent of changes in cytosolic pH, because it was neither mimicked by sodium acetate nor inhibited by ammonium chloride, and it was reproduced by 2',4'-dimethylbenzamil, an analog of amiloride that is inactive on the Na+/H+ antiport. Furthermore, EIPA enhanced the Ca2(+)-dependent phosphorylation of a similar Mr 95,000 protein in a cell-free system, rabbit reticulocyte lysate, where an inhibitory effect of amiloride on protein synthesis has already been described (3). Because phosphorylation decreases the activity of elongation factor-2, our observation might explain why amiloride analogs inhibit protein synthesis.
5-（N-乙基-N-异丙基）氨氯吡脒（EIPA）是一种有效的Na⁺/H⁺逆向转运抑制剂，它降低了[³⁵S]甲硫氨酸掺入牛主动脉内皮细胞蛋白质中的量，并诱导了一种分子量为95,000的蛋白质发生磷酸化。先前已表明，该蛋白质会因ATP、缓激肽和A23187而发生磷酸化（1），并被鉴定为延伸因子-2（2）。EIPA的作用与胞质pH的变化无关，因为它既不能被醋酸钠模拟，也不会被氯化铵抑制，并且它能被氨氯吡脒的类似物2',4'-二甲基苯甲酰胺重现，而该类似物对Na⁺/H⁺逆向转运无活性。此外，EIPA在无细胞系统兔网织红细胞裂解物中增强了一种类似的分子量为95,000的蛋白质的Ca²⁺依赖性磷酸化，在该系统中已经描述了氨氯吡脒对蛋白质合成的抑制作用（3）。由于磷酸化会降低延伸因子-2的活性，我们的观察结果可能解释了为什么氨氯吡脒类似物会抑制蛋白质合成。
