NHE3 in an ancestral vertebrate: primary sequence, distribution, localization, and function in gills
NHE3 in an ancestral vertebrate: primary sequence, distribution, localization, and function in gills
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DOI：
10.1152/ajpregu.00048.2005
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发表时间：
2005-11-01
影响因子：
2.8
通讯作者：
Evans, DH
中科院分区：
文献类型：
--
作者：
Choe, KP;Kato, A;Evans, DH
在哺乳动物中，Na+/H+交换器3 （NHE3）在肾近端小管中与Na+/K+- atp酶一起表达，在肾近端小管中分泌H+并吸收Na+以维持血液pH值和体积。在板鳃类（鲨鱼、鳐鱼和黄貂鱼）中，鳃是pH值和渗透调节的主要部位。本研究旨在确定鳃中是否存在上皮NHE同源物，如果存在，则定位其在鳃中的表达，并确定其表达是否会因环境盐度或高血氧症而改变。利用退化引物和RTPCR技术从大西洋黄貂鱼（Dasyatis sabina）的鳃中推导出哺乳动物NHE2和NHE3同源基因的部分序列。Real-time PCR显示，当黄貂鱼被转移到低盐度环境时，NHE3同源基因的mRNA表达增加，而在高糖血症期间则没有增加。两种处理均未改变NHE2同源物的表达。然后使用cDNA快速扩增来推断推定的NHE3的完整序列。这对2,744个碱基对的cDNA包含一个编码区，该编码区含有2,511个氨基酸，与人类NHE3 （SLC9A3）相同70%。针对黄貂鱼羧基尾产生的抗血清标记了富含Na+/K+- atp酶的上皮细胞的顶膜，而对淡水的适应导致了鳃中标记的重新分布。该研究首次从板鳃纲中克隆出NHE3，并首次证实在适应低盐度时鳃中NHE3的表达增加，这表明NHE3可以从低离子环境中吸收Na+。
In mammals, the Na+/H+ exchanger 3 (NHE3) is expressed with Na+/K+-ATPase in renal proximal tubules, where it secretes H+ and absorbs Na+ to maintain blood pH and volume. In elasmobranchs ( sharks, skates, and stingrays), the gills are the dominant site of pH and osmoregulation. This study was conducted to determine whether epithelial NHE homologs exist in elasmobranchs and, if so, to localize their expression in gills and determine whether their expression is altered by environmental salinity or hypercapnia. Degenerate primers and RTPCR were used to deduce partial sequences of mammalian NHE2 and NHE3 homologs from the gills of the euryhaline Atlantic stingray (Dasyatis sabina). Real-time PCR was then used to demonstrate that mRNA expression of the NHE3 homolog increased when stingrays were transferred to low salinities but not during hypercapnia. Expression of the NHE2 homolog did not change with either treatment. Rapid amplification of cDNA was then used to deduce the complete sequence of a putative NHE3. The 2,744-base pair cDNA includes a coding region for a 2,511-amino acid protein that is 70% identical to human NHE3 (SLC9A3). Antisera generated against the carboxyl tail of the putative stingray NHE3 labeled the apical membranes of Na+/K+-ATPase-rich epithelial cells, and acclimation to freshwater caused a redistribution of labeling in the gills. This study provides the first NHE3 cloned from an elasmobranch and is the first to demonstrate an increase in gill NHE3 expression during acclimation to low salinities, suggesting that NHE3 can absorb Na+ from ion-poor environments.