Ammonia secretion from fish gill depends on a set of Rh glycoproteins
Ammonia secretion from fish gill depends on a set of Rh glycoproteins
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DOI：
10.1096/fj.06-6834com
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发表时间：
2007-04-01
期刊：
影响因子：
4.8
通讯作者：
Hirose, Shigehisa
中科院分区：
文献类型：
--
作者：
Nakada, Tsutomu;Westhoff, Connie M.;Hirose, Shigehisa
硬骨鱼鳃中的氨排泄对氮的消除是必不可少的。虽然许多生理学研究已经测量了氨的排泄，但氨通过鳃上皮细胞膜的运动机制仍不清楚。哺乳动物的Rh糖蛋白是细菌、酵母和植物中介导氨运输的蛋白质家族的成员。我们鉴定了河豚Rh糖蛋白同源物fRhag、fRhbg、fRhcg1和fRhcg2。Northern印迹、原位杂交和免疫组织化学显示，河豚红系Rh糖蛋白同源物rHAg存在于鱼的红细胞和血液器官(脾和肾)中。所有四种河豚Rh糖蛋白都特异性地定位于鳃，排列在柱状细胞、铺面细胞和富含线粒体的细胞中。在非洲爪哇卵母细胞中的异源表达表明，它们介导了甲基铵(一种类似于铵的物质)的运输。这些结果表明河豚Rh糖蛋白与鳃排氨有关。这些发现挑战了经典的观点，即鱼鳃中的氨排泄是通过被动扩散发生的。
Ammonia excretion from the gill in teleost fish is essential for nitrogen elimination. Although numerous physiological studies have measured ammonia excretion, the mechanism of ammonia movement through the membranes of gill epithelial cells is still unknown. Mammalian Rh glycoproteins are members of a family of proteins that mediate ammonia transport in bacteria, yeast, and plants. We identified the Rh glycoprotein homologs, fRhag, fRhbg, fRhcg1, and fRhcg2, of the pufferfish, Takifugu rubripes. Northern blot, in situ hybridization, and immunohistochemistry revealed that the pufferfish erythroid Rh glycoprotein homologue fRhag was present in red blood cells and the hematological organs ( spleen and kidney) in fish. All four pufferfish Rh glycoproteins are specifically localized in the gill and line the pillar cells, pavement cells, and the mitochondrion-rich cells. Heterologous expression in Xenopus oocytes showed that they mediate methylammonium ( an analog of ammonium) transport. These results suggest that pufferfish Rh glycoproteins are involved in ammonia excretion from the gill. These findings challenge the classic view that ammonia excretion in the fish gill occurs by passive diffusion.