Da Silva Nicolas, Silberstein Claudia, Beaulieu Valérie, Piétrement Christine, Van Hoek Alfred N, Brown Dennis, Breton Sylvie
Massachusetts General Hospital, Program in Membrane Biology-Nephrology Division, Boston, Massachusetts 02114, USA.
Biol Reprod. 2006 Feb;74(2):427-38. doi: 10.1095/biolreprod.105.044735. Epub 2005 Oct 12.
The mammalian aquaporins (AQPs) are a family of 13 transmembrane channel proteins that are involved in the transport of water in numerous organs. In the male excurrent duct, the movement of fluid and solutes across the epithelium is essential for establishing the proper luminal environment in which sperm mature and are stored. AQP9 is abundantly expressed in the efferent ducts, the epididymis, and the vas deferens, where it could represent an important apical pathway for transmembrane water and solute movement. However, other organs in which water transport is critical, including the kidney, the lung, or the eye, express several different AQPs with a cell-specific pattern. To undertake a systematic analysis of the expression of known AQPs in the postnatal and adult rat epididymis, we examined the expression of their respective mRNAs in epithelial cells isolated by laser capture microdissection (LCM), and we determined their corresponding protein expression pattern by immunofluorescence and Western blotting. Our data show that, whereas AQP9 is the main AQP of the epididymis, the mRNA specific for Aqp2, 5, 7, and 11 are also expressed in epididymal epithelial cells. AQP5 protein colocalizes with AQP9 in the apical membrane of a subpopulation of principal cells in the corpus and cauda regions. Aqp2 mRNA was detected in epithelial cells after the second postnatal week and the amount significantly increased up to adulthood. However, AQP2 protein was detected only in the distal cauda of young rats (between the second and fourth postnatal week). No AQP2 protein was detected in the adult epididymis, indicating that posttranscriptional mechanisms are involved in the regulation of AQP2 expression. In addition, epididymal epithelial cells express significant amounts of the mRNAs coding for AQP7 and 11. No mRNA or protein for AQPs 0, 4, 6, and 8 were detectable in epithelial cells, and Aqp1 was detected in whole epididymal samples, but not in epithelial cells. Thanks to the recent development of microdissection technologies, our observations suggest that epididymal epithelial cells express several members of the AQP family with a region-specific pattern. AQPs may be involved not only in the transepithelial transport of water in the epididymis but also in the postnatal development of this organ, as suggested by the differential expression of AQP2.
哺乳动物水通道蛋白（AQPs）是一个由13种跨膜通道蛋白组成的家族，它们参与了许多器官中的水运输过程。在雄性输出管道中，液体和溶质跨上皮细胞的移动对于建立精子成熟和储存的合适管腔环境至关重要。AQP9在输出小管、附睾和输精管中大量表达，在那里它可能是跨膜水和溶质移动的一条重要的顶端途径。然而，其他对水运输至关重要的器官，包括肾脏、肺或眼睛，以细胞特异性模式表达几种不同的AQP。为了对出生后和成年大鼠附睾中已知AQP的表达进行系统分析，我们检测了通过激光捕获显微切割（LCM）分离的上皮细胞中它们各自mRNA的表达，并通过免疫荧光和蛋白质印迹法确定了它们相应的蛋白质表达模式。我们的数据表明，虽然AQP9是附睾的主要AQP，但Aqp2、5、7和11的特异性mRNA也在附睾上皮细胞中表达。AQP5蛋白在体部和尾部区域主细胞亚群的顶端膜中与AQP9共定位。出生后第二周后在上皮细胞中检测到Aqp2 mRNA，其数量在成年前显著增加。然而，仅在幼鼠（出生后第二至第四周）的远端尾部检测到AQP2蛋白。在成年附睾中未检测到AQP2蛋白，这表明转录后机制参与了AQP2表达的调节。此外，附睾上皮细胞表达大量编码AQP7和11的mRNA。在上皮细胞中未检测到AQP0、4、6和8的mRNA或蛋白，在整个附睾样本中检测到Aqp1，但在上皮细胞中未检测到。由于显微切割技术的最新发展，我们的观察结果表明附睾上皮细胞以区域特异性模式表达AQP家族的几个成员。如AQP2的差异表达所示，AQP可能不仅参与附睾中水的跨上皮运输，还参与该器官的出生后发育。
