Magro Fernando, Fraga Sónia, Soares-da-Silva Patrício
Institute of Pharmacology and Therapeutics, Faculty of Medicine, 4200 Porto, Portugal.
Biochem Pharmacol. 2005 Nov 1;70(9):1312-9. doi: 10.1016/j.bcp.2005.07.015.
This study evaluated the effect of interferon-gamma (IFN-gamma) upon the function and expression of type 1 Na(+)/H+ exchanger (NHE1) in human intestinal epithelial HT-29 cells, namely that concerning the abundance of surface NHE1 and NHE1 binding to the ezrin, radixin and moesin (ERM) family of proteins. HT-29 cells express endogenous NHE1 and the ERM family of proteins that retain the localization of NHE1 in the membrane. Long-term exposure (24 h) of HT-29 cells to IFN-gamma resulted in a concentration-dependent decrease in NHE1 activity. Inhibition of NHE1 activity by IFN-gamma was absent after pretreatment with cariporide. The long-term exposure to IFN-gamma was accompanied by increase in surface NHE1 and ERM abundance and no changes in total NHE1 and ERM abundance. Inhibition of signal transducer and activator transcription factor 1 (STAT1) with epigallocatechin-3-gallate (EGCG) prevented the inhibitory effect of IFN-gamma. Treatment with IFN-gamma activated phospho-STAT1 was markedly attenuated by EGCG. The IFN-gamma-induced increase in surface NHE1 and ERM abundance was prevented by EGCG. In conclusion, long-term inhibition of NHE1 activity by IFN-gamma involves STAT1 phosphorylation and is accompanied by increased abundance of surface NHE1 and the NHE1 membrane anchoring ERM proteins.
本研究评估了γ-干扰素（IFN-γ）对人肠道上皮HT-29细胞中1型钠氢交换体（NHE1）功能和表达的影响，即关于表面NHE1的丰度以及NHE1与埃兹蛋白、根蛋白和膜突蛋白（ERM）家族蛋白的结合情况。HT-29细胞表达内源性NHE1和ERM家族蛋白，这些蛋白可维持NHE1在膜上的定位。HT-29细胞长期（24小时）暴露于IFN-γ会导致NHE1活性呈浓度依赖性下降。用卡立泊来德预处理后，IFN-γ对NHE1活性的抑制作用消失。长期暴露于IFN-γ伴随着表面NHE1和ERM丰度的增加以及总NHE1和ERM丰度的无变化。用表没食子儿茶素-3-没食子酸酯（EGCG）抑制信号转导子和转录激活因子1（STAT1）可防止IFN-γ的抑制作用。EGCG可显著减弱IFN-γ激活的磷酸化STAT1的作用。EGCG可防止IFN-γ诱导的表面NHE1和ERM丰度增加。总之，IFN-γ对NHE1活性的长期抑制涉及STAT1磷酸化，并伴随着表面NHE1和NHE1膜锚定ERM蛋白丰度的增加。
