Molecular mechanisms underlying active desalination and low water permeability in the esophagus of eels acclimated to seawater
Molecular mechanisms underlying active desalination and low water permeability in the esophagus of eels acclimated to seawater
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适应海水的鳗鱼食道主动脱盐和低透水性的分子机制
DOI：
10.1152/ajpregu.00465.2016
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发表时间：
2016
影响因子：
--
通讯作者：
Kusakabe M
中科院分区：
文献类型：
--
作者：
Takei Y;Wong M;Pipil S;Ozaki H;Suzuki Y;Iwasaki W;Kusakabe M
海生硬骨鱼可以吸收吸收的海水来维持水分平衡，其中食道海水淡化起着至关重要的作用。在驯化的鳗鱼的食道中，腔钠盐的吸收增加了10倍，除去腔盐中的Na+或Cl-−后，这种促进吸收的作用消失了，这表明是耦合转运。粘膜/浆膜应用不同的钠/氯−转运体阻断剂可显著降低其吸收。在RNAseq检测到的鳗鱼食道转运蛋白基因中，二甲基阿米洛利敏感的Na+/H+交换器(NHE3)和4，4‘-二异硫氰基-2，2’-二磺酸敏感的氯−/交换器(AE)与上皮细胞顶膜上的支架蛋白偶联，以及哇巴因敏感的Na+-K+-α酶(NKA1c和NKA3ATPase)和基底膜上的二苯胺-2-羧酸敏感的氯-α通道(CLCN2)，可能与促进细胞跨−的跨细胞运输有关。上调的碳酸氢酶2a(CA2a)提供H+和激活偶联的NHE和AE。顶端对氢氯噻嗪敏感的钠-氯转运蛋白−和碱侧钠转运蛋白1和Ae1是其他可能的候选。鉴于海水硬骨鱼食道的低透水性，下调的水通道蛋白基因(aqp1a和aqp3)和上调的claudin基因(Cldn15a)是跨细胞/旁细胞途径的候选基因。原位杂交显示，这些上调的转运蛋白和紧密连接蛋白基因在鳗鱼食道的吸收柱状上皮细胞中表达。这些结果使我们能够全面了解海洋硬骨鱼食道所特有的主动淡化和低透水性的分子机制，并对胃肠道在西南驯化中的作用有了更深入的了解。
Marine teleosts can absorb imbibed seawater (SW) to maintain water balance, with esophageal desalination playing an essential role. NaCl absorption from luminal SW was enhanced 10-fold in the esophagus of SW-acclimated eels, and removal of Na+or Cl−from luminal SW abolished the facilitated absorption, indicating coupled transport. Mucosal/serosal application of various blockers for Na+/Cl−transporters profoundly decreased the absorption. Among the transporter genes expressed in eel esophagus detected by RNA-seq, dimethyl amiloride-sensitive Na+/H+exchanger (NHE3) and 4,4′-diisothiocyano-2,2′-disulfonic acid-sensitive Cl−/exchanger (AE) coupled by the scaffolding protein on the apical membrane of epithelial cells, and ouabain-sensitive Na+-K+-ATPases (NKA1α1c and NKA3α) and diphenylamine-2-carboxylic acid-sensitive Cl−channel (CLCN2) on the basolateral membrane, may be responsible for enhanced transcellular NaCl transport because of their profound upregulation after SW acclimation. Upregulated carbonic anhydrase 2a (CA2a) supplies H+andfor activation of the coupled NHE and AE. Apical hydrochlorothiazide-sensitive Na+-Cl−cotransporters and basolateral Na+-cotransporter (NBCe1) and AE1 are other possible candidates. Concerning the low water permeability that is typically seen in marine teleost esophagus, downregulated aquaporin genes (aqp1aandaqp3) and upregulated claudin gene (cldn15a) are candidates for transcellular/paracellular route. In situ hybridization showed that these upregulated transporters and tight-junction protein genes were expressed in the absorptive columnar epithelial cells of eel esophagus. These results allow us to provide a full picture of the molecular mechanism of active desalination and low water permeability that are characteristic to marine teleost esophagus and gain deeper insights into the role of gastrointestinal tracts in SW acclimation.