Rieder Carmen V, Fliegel Larry
Department of Biochemistry, CIHR Membrane Protein Group, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada.
Mol Cell Biochem. 2003 Jan;243(1-2):87-95. doi: 10.1023/a:1021643608619.
We examined regulation of the Na+/H+ exchanger (NHE1 isoform) in the developing mouse. We generated transgenic mice with the Na+/H+ exchanger promoter directing expression of the beta-Galactosidase reporter. We found that expression of the Na+/H+ exchanger was maximum in the heart and liver of 12-day-old embryonic mice. Similar results were found in mice using the green fluorescent protein reporter driven by the Na+/H+ exchanger promoter. Detailed examination of the myocardium revealed that the GFP reporter protein was expressed in the cytoplasm of cardiomyocyte cells. We examined NHE1 protein expression in transgenic mice lacking the transcription factors AP-2alpha or the transcription factor COUP-TF1. Eighteen-day-old AP-2alpha heterozygote mice show no large changes in NHE1 expression in heart, lung, liver, kidney and brain. In contrast, 18-day-old embryos from AP-2alpha null mice showed a large increase in Na+/H+ exchanger protein expression in the brain. NHE1 protein levels in COUP-TF1 knockout embryos did not differ from wild type embryos. The results suggest that AP-2alpha and COUP-TF1 are not critical to NHE1 expression in the late stage embryo and that other related transcription factors may function in regulation of the Na+/H+ exchanger.
我们研究了发育中小鼠体内钠氢交换体（NHE1亚型）的调控机制。我们构建了转基因小鼠，其钠氢交换体启动子指导β-半乳糖苷酶报告基因的表达。我们发现，钠氢交换体在12日龄胚胎小鼠的心脏和肝脏中表达量最高。在使用由钠氢交换体启动子驱动的绿色荧光蛋白报告基因的小鼠中也发现了类似结果。对心肌的详细检查显示，绿色荧光蛋白报告基因蛋白在心肌细胞的细胞质中表达。我们检测了缺乏转录因子AP-2α或转录因子COUP-TF1的转基因小鼠中NHE1蛋白的表达。18日龄的AP-2α杂合子小鼠心脏、肺、肝脏、肾脏和大脑中的NHE1表达没有明显变化。相比之下，AP-2α基因敲除小鼠的18日龄胚胎大脑中钠氢交换体蛋白表达大幅增加。COUP-TF1基因敲除胚胎中的NHE1蛋白水平与野生型胚胎没有差异。结果表明，AP-2α和COUP-TF1在胚胎后期对NHE1表达并不关键，其他相关转录因子可能在钠氢交换体的调控中发挥作用。
