Expression of a mammalian aquaporin 3 homolog in the anterior pituitary gonadotrophs of the tree frog, Hyla japonica
Expression of a mammalian aquaporin 3 homolog in the anterior pituitary gonadotrophs of the tree frog, Hyla japonica
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哺乳动物水通道蛋白 3 同源物在树蛙垂体前叶促性腺激素中的表达
DOI：
10.1007/s00441-010-1122-1
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Tanaka S
中科院分区：
文献类型：
--
作者：
Sato M;Nakakura T;Ogushi Y;Akabane G;Kurabuchi S;Suzuki M;Tanaka S
水通道蛋白（Aquaporins，AQP）是一类在维持机体水平衡中发挥重要作用的水通道蛋白。在日本雨蛙（Hyla japonica）中已经鉴定出几种水通道蛋白。其中，在上皮细胞的基底外侧膜中表达的AQP-h3 BL是哺乳动物AQP 3的同源物。使用免疫组织化学和原位RT-PCR，我们已经证明，AQP-h3 BL表达在垂体前叶促性腺激素细胞的树蛙，但不是在其他垂体前叶的分泌细胞。在促性腺激素β亚基（LHβ）标记的细胞中，AQP-h3 BL蛋白定位于质膜、核膜和细胞质中。AQP-h3 BL mRNA和LHβ蛋白的双标记显示，AQP-h3 BL mRNA在促性腺激素细胞中表达。在促性腺激素释放激素（GnRH）刺激下，位于质膜的AQP-h3 BL标记增强，并伴随LHβ阳性物质转运至质膜。这些发展正好与细胞质和核膜附近的标记密度下降，这表明后者的本地化可能作为“存储区”的AQP-h3 BL。免疫电镜也证实了这些AQP-h3 BL蛋白的定位。基于这些结果，我们认为，AQP-h3 BL蛋白在青蛙促性腺激素细胞参与的分泌颗粒的形成，肿胀和颗粒体积的增加和胞吐。
Aquaporins (AQPs) are a family of water channel proteins that play a major role in maintaining water homeostasis in various organisms. Several AQPs have been identified in the tree frog,Hyla japonica. Of these, AQP-h3BL, which is expressed in the basolateral membrane of the epithelial cells, is a homolog of mammalian AQP3. Using immunohistochemistry and in situ RT-PCR, we have demonstrated that AQP-h3BL is expressed in the anterior pituitary gonadotrophs of the tree frog but not in the other hormone-producing cells of the anterior pituitary. In gonadotrophs labeled for luteinizing hormone subunit-β (LHβ), AQP-h3BL protein was found to reside in the plasma membrane, the nuclear membrane and the cytoplasm. Double-labeling of AQP-h3BL mRNA and LHβ protein revealed that AQP-h3BL mRNA is expressed in the gonadotrophs. Following stimulation by gonadotropin-releasing hormone (GnRH), the label for AQP-h3BL localized in the plasma membrane became more intense, concomitant with the transport of LHβ-positive materials to the plasma membrane. These developments coincided with a decrease in the labeling density in the cytoplasm and near the nuclear membrane, suggesting that the latter localizations may function as “storage area“ for AQP-h3BL. Immunoelectron microscopy also confirmed these localizations of AQP-h3BL protein. Based on these results, we suggest that AQP-h3BL protein in the frog gonadotrophs is involved in the formation of secretory granules, the swelling and increase in the volume of the granules and exocytosis.