Identification of zebrafish Fxyd11a protein that is highly expressed in ion-transporting epithelium of the gill and skin and its possible role in ion homeostasis
Identification of zebrafish Fxyd11a protein that is highly expressed in ion-transporting epithelium of the gill and skin and its possible role in ion homeostasis
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DOI：
10.3389/fphys.2010.00129
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发表时间：
2010-01-01
影响因子：
4
通讯作者：
Hirose, Shigehisa
中科院分区：
文献类型：
--
作者：
Saito, Kaori;Nakamura, Nobuhiro;Hirose, Shigehisa
FXYD蛋白是一种小的单跨膜蛋白，被认为是Na ~+-K ~+-ATPase的辅助调节亚基，最近被认为参与了硬骨鱼的离子交换调节。在淡水鱼中，利用Na+-K+-ATP酶产生的Na+电化学梯度，许多离子通过鳃和皮肤上皮的富钾细胞（MRCs）被积极吸收。本研究通过对斑马鱼MRC中FXYD蛋白的鉴定，探讨了斑马鱼MRC中Na+-K+-ATP酶的分子调控机制。对成年斑马鱼组织的逆转录酶PCR研究表明，在斑马鱼数据库中发现的8个fxyd基因中，只有斑马鱼fxyd 11（zfxyd 11）mRNA表现出鳃特异性表达。免疫荧光双标显示zFxyd 11在富含Na+-K+-ATPase的MRC（NaK-MRC）中大量表达，而在富含液泡型H+-转运ATPase的MRC中不表达。原位邻位连接实验证明它与NaK-MRC中的Na+-K+-ATPase密切相关。zfxyd 11 mRNA的表达是可检测的受精后1天，其在整个幼虫和成人鳃的表达水平调节响应环境离子浓度的变化。此外，敲低zFxyd 11导致幼虫皮肤中Na+-K+-ATP酶阳性细胞的数量显著增加。这些结果提示zFxyd 11可能通过调节Na+-K+-ATPase活性来调节NaK-MRCs的转运能力，并可能参与调节体液和电解质的稳态。
FXYD proteins, small single-transmembrane proteins, have been proposed to be auxiliary regulatory subunits of Na+-K+-ATPase and have recently been implied in ion osmoregulation of teleost fish. In freshwater (FW) fish, numerous ions are actively taken up through mitochondrionrich cells (MRCs) of the gill and skin epithelia, using the Na+ electrochemical gradient generated by Na+-K+-ATPase. In the present study, to understand the molecular mechanism for the regulation of Na+-K+-ATPase in MRCs of FW fish, we sought to identify FXYD proteins expressed in MRCs of zebrafish. Reverse-transcriptase PCR studies of adult zebrafish tissues revealed that, out of eight fxyd genes found in zebrafish database, only zebrafish fxyd11 (zfxyd11) mRNA exhibited a gill-specific expression. Double immunofluorescence staining showed that zFxyd11 is abundantly expressed in MRCs rich in Na+-K+-ATPase (NaK-MRCs) but not in those rich in vacuolar-type H+-transporting ATPase. An in situ proximity ligation assay demonstrated its close association with Na+-K+-ATPase in NaK-MRCs. The zfxyd11 mRNA expression was detectable at 1 day postfertilization, and its expression levels in the whole larvae and adult gills were regulated in response to changes in environmental ionic concentrations. Furthermore, knockdown of zFxyd11 resulted in a significant increase in the number of Na+-K+-ATPase-positive cells in the larval skin. These results suggest that zFxyd11 may regulate the transport ability of NaK-MRCs by modulating Na+-K+-ATPase activity, and may be involved in the regulation of body fluid and electrolyte homeostasis.