Koyama N, Ishibashi K, Kuwahara M, Inase N, Ichioka M, Sasaki S, Marumo F
Second Department of Internal Medicine, Tokyo Medical and Dental University, Tokyo, 1-5-45 Yushima, Bunkyo-ku, 113-8519, Japan.
Genomics. 1998 Nov 15;54(1):169-72. doi: 10.1006/geno.1998.5552.
The cDNA and the gene of human aquaporin8 (AQP8) were cloned from human testis cDNA and a genomic library, respectively. The AQP8 cDNA encodes 261 amino acids. The identity of the amino acid sequence to other aquaporins is highest with a plant water channel, gamma-TIP (40.4%), while AQP2 and AQP3 are 28.9 and 29.5% identical to human AQP8, respectively. The human AQP8 is only 74.9% identical to rat AQP8 and 76.0% identical to mouse AQP8. In Northern blot analysis, approximately 1.35-kb human AQP8 mRNA was expressed in pancreas and colon, but not in other tissues. Absence of human AQP8 in testis is noteworthy as rat AQP8 was abundantly expressed in testis. The expression of human AQP8 cRNA in Xenopus oocytes increased osmotic water permeability by 10-fold. AQP8 was not permeable to urea nor to glycerol. The AQP8 gene has five introns, and the locations of exon-intron boundaries were different from those of the other mammalian aquaporins, suggesting its separate phylogenetic origin.
人水通道蛋白8（AQP8）的互补DNA（cDNA）和基因分别从人睾丸cDNA和基因组文库中克隆得到。AQP8 cDNA编码261个氨基酸。其氨基酸序列与其他水通道蛋白的一致性最高的是一种植物水通道蛋白γ-TIP（40.4%），而AQP2和AQP3与人AQP8的一致性分别为28.9%和29.5%。人AQP8与大鼠AQP8的一致性仅为74.9%，与小鼠AQP8的一致性为76.0%。在Northern印迹分析中，约1.35 kb的人AQP8信使核糖核酸（mRNA）在胰腺和结肠中表达，但在其他组织中不表达。值得注意的是，人AQP8在睾丸中不存在，而大鼠AQP8在睾丸中大量表达。人AQP8互补核糖核酸（cRNA）在非洲爪蟾卵母细胞中的表达使渗透水通透性增加了10倍。AQP8对尿素和甘油均不通透。AQP8基因有5个内含子，外显子-内含子边界的位置与其他哺乳动物水通道蛋白不同，表明其有独立的系统发生起源。
