Wang Z, Orlowski J, Shull G E
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Ohio 45267-0524.
J Biol Chem. 1993 Jun 5;268(16):11925-8.
A cDNA encoding a new isoform of the rat Na/H exchanger (NHE) family has been identified by cross-hybridization with an NHE-1 cDNA probe. The 3.9-kilobase stomach cDNA encodes a protein of 813 amino acids with an M(r) of 91,296. The amino acid sequence of the protein, termed NHE-2, is 42% identical to NHE-1, 36% identical to NHE-3, and 57% identical to NHE-4. Na/H exchanger-deficient Chinese hamster ovary cells that were transfected with an expression construct containing the complete coding sequence of this cDNA exhibit amiloride-sensitive, H+-dependent 22Na+ influx, demonstrating that the protein it encodes is a functional Na/H exchanger. Northern hybridization analyses show that the corresponding mRNA is expressed predominantly in small intestine, colon, and stomach, with much lower levels present in skeletal muscle, kidney, brain, testis, uterus, heart, and lung. This suggests that NHE-2 plays an important role in gastrointestinal physiology and functions in many other organ systems as well.
通过与NHE - 1 cDNA探针交叉杂交，已鉴定出一种编码大鼠钠氢交换体（NHE）家族新亚型的cDNA。这个3.9千碱基的胃cDNA编码一个由813个氨基酸组成、分子量为91296的蛋白质。该蛋白质的氨基酸序列被命名为NHE - 2，与NHE - 1的序列一致性为42%，与NHE - 3的一致性为36%，与NHE - 4的一致性为57%。用含有该cDNA完整编码序列的表达构建体转染缺乏钠氢交换体的中国仓鼠卵巢细胞，这些细胞表现出对氨氯吡咪敏感、依赖H⁺的²²Na⁺内流，表明其编码的蛋白质是一种功能性钠氢交换体。Northern杂交分析表明，相应的mRNA主要在小肠、结肠和胃中表达，在骨骼肌、肾脏、大脑、睾丸、子宫、心脏和肺中的表达水平要低得多。这表明NHE - 2在胃肠生理学中起重要作用，在许多其他器官系统中也有功能。
