Rhesus glycoprotein p2(Rhp2) is a novel member of the Rh family of ammonia transporters highly expressed in shark kidney
Rhesus glycoprotein p2(Rhp2) is a novel member of the Rh family of ammonia transporters highly expressed in shark kidney
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恒河猴糖蛋白 p2(Rhp2) 是氨转运蛋白 Rh 家族的新成员，在鲨鱼肾中高表达
DOI：
10.1074/jbc.m109.052068
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
S.
中科院分区：
文献类型：
--
作者：
Nakada;T.;Westhoff;C. M.;Yamaguchi;Y.;Hyodo;S.;Li;X.;Muro;T.;Kato;A.;Nakamura;N.;Hirose;S.
恒河猴（Rh）糖蛋白是一个能够运输氨的膜蛋白家族。我们从带状猎犬鲨（Triakis scyllium）的肾脏cDNA文库中分离出一种新的Rh糖蛋白Rhp2的全长cDNA。分子克隆和鉴定表明，Rhp2由476个氨基酸残基组成，具有12个推测的跨膜跨越，与其他家族成员的结构一致。sharkrhp2基因仅由一个编码外显子组成。Northern blotting和原位杂交显示，Rhp2 mRNA仅在肾窦区肾小管中表达，而在肾束区和肾小体中不表达。特异性抗血清免疫组化染色显示，Rhp2定位于肾小管细胞基底外膜。phalloidin双荧光标记或Na+/K+- atp酶标记进一步将位置缩小到窦区第二和第四环。液泡型H+- atp酶定位于表达rhp2的小管细胞的顶膜。实时荧光定量PCR和Western blotting分析显示，Rhp2的表达随着环境盐度的升高而升高。利用xenopusoocyte表达系统进行的功能分析表明，Rhp2具有转运氨的类似物甲基铵的活性。NH4Cl对这种转运活性有抑制作用，而三甲胺- n -氧化物和尿素对其没有抑制作用。这些结果表明，Rhp2参与了由鲨鱼和鳐鱼组成的软骨鱼组的肾脏氨重吸收。
Rhesus (Rh) glycoproteins are a family of membrane proteins capable of transporting ammonia. We isolated the full-length cDNA of a novel Rh glycoprotein, Rhp2, from a kidney cDNA library from the banded hound shark,Triakis scyllium. Molecular cloning and characterization indicated that Rhp2 consists of 476 amino acid residues and has 12 putative transmembrane spans, consistent with the structure of other family members. The sharkRhp2gene was found to consist of only one coding exon. Northern blotting andin situhybridization revealed that Rhp2 mRNA is exclusively expressed in the renal tubules of the sinus zone but not in the bundle zone and renal corpuscles. Immunohistochemical staining with a specific antiserum showed that Rhp2 is localized in the basolateral membranes of renal tubule cells. Double fluorescence labeling with phalloidin or labeling of the Na+/K+-ATPase further narrowed the location to the second and fourth loops in the sinus zone. Vacuolar type H+-ATPase was localized in apical membranes of the Rhp2-expressing tubule cells. Quantitative real-time PCR analysis and Western blotting showed that expression of Rhp2 was increased in response to elevation of environmental salinity. Functional analysis using theXenopusoocyte expression system showed that Rhp2 has transport activity for methylammonium, an analog of ammonia. This transport activity was inhibited by NH4Cl but not trimethylamine-N-oxide and urea. These results suggested that Rhp2 is involved in ammonia reabsorption in the kidney of the elasmobranch group of cartilaginous fish comprising the sharks and rays.