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1
Geyer, R. Ryan, Raif Musa-Aziz, Xue Qin, and Walter F. Boron. "Relative CO2/NH3 selectivities of mammalian aquaporins 0–9." American Journal of Physiology-Cell Physiology 304, no. 10 (May 15, 2013): C985—C994. http://dx.doi.org/10.1152/ajpcell.00033.2013.
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Previous work showed that aquaporin 1 (AQP1), AQP4-M23, and AQP5 each has a characteristic CO2/NH3 and CO2/H2O permeability ratio. The goal of the present study is to characterize AQPs 0–9, which traffic to the plasma membrane when heterologously expressed in Xenopus oocytes. We use video microscopy to compute osmotic water permeability ( Pf) and microelectrodes to record transient changes in surface pH (ΔpHS) caused by CO2 or NH3 influx. Subtracting respective values for day-matched, H2O-injected control oocytes yields the channel-specific values Pf* and ΔpHS*. We find that Pf* is significantly >0 for all AQPs tested except AQP6. (ΔpHS*)CO2 is significantly >0 for AQP0, AQP1, AQP4-M23, AQP5, AQP6, and AQP9. (ΔpHS*)NH3 is >0 for AQP1, AQP3, AQP6, AQP7, AQP8, and AQP9. The ratio (ΔpHS*)CO2/ Pf* falls in the sequence AQP6 (∞) > AQP5 > AQP4-M23 > AQP0 ≅ AQP1 ≅ AQP9 > others (0). The ratio (ΔpHS*)NH3/ Pf* falls in the sequence AQP6 (∞) > AQP3 ≅ AQP7 ≅ AQP8 ≅ AQP9 > AQP1 > others (0). Finally, the ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 falls in the sequence AQP0 (∞) ≅ AQP4-M23 ≅ AQP5 > AQP6 > AQP1 > AQP9 > AQP3 (0) ≅ AQP7 ≅ AQP8. The ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 is indeterminate for both AQP2 and AQP4-M1. In summary, we find that mammalian AQPs exhibit a diverse range of selectivities for CO2 vs. NH3 vs. H2O. As a consequence, by expressing specific combinations of AQPs, cells could exert considerable control over the movements of each of these three substances.
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Kendall, B., J. E. J. Maxwell, A. J. German, D. Marples, M. D. Royal, and A. Mobasheri. "Immunohistochemical localisation of aquaporin water channels in the bovine mammary gland." Proceedings of the British Society of Animal Science 2007 (April 2007): 1. http://dx.doi.org/10.1017/s1752756200019049.
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The aquaporins (AQPs) are a family of small integral membrane proteins 28-35kDa in size, sub classified into 2 groups; those selectively permeated by water (the aquaporins; AQP0, AQP1, AQP2, AQP4, AQP5, AQP6 and AQP8) or by water and small organic osmolytes such as glycerol and urea (the aquaglyceroporins; AQP3, AQP7, AQP9 and AQP10). AQPs are expressed in a variety of epithelial tissues where they are responsible for rapid water movement driven by osmotic gradients. The mammary gland produces and secretes milk which consists of water, lipids, electrolytes, vitamins, sugars and specific milk proteins. However, little is known about AQP expression, distribution and function in mammary tissue or about the process of water transport across the mammary epithelium. The only information available relates to the identification of AQP1 and AQP3 in capillary endothelia and epithelial cells of mouse mammary glands respectively (Matsuzaki et al., 2005). Since water delivery to the mammary gland is critical for milk production, which is of major economic importance to the dairy industry, it is necessary to understand the underlying physiology involved. The aim of this study was to determine the expression and distribution of AQPs within the bovine mammary gland.
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Cao, Yixin, Ying He, Cong Wei, Jing Li, Lejing Qu, Huiqin Zhang, Ying Cheng, and Boling Qiao. "Aquaporins Alteration Profiles Revealed Different Actions of Senna, Sennosides, and Sennoside A in Diarrhea-Rats." International Journal of Molecular Sciences 19, no. 10 (October 17, 2018): 3210. http://dx.doi.org/10.3390/ijms19103210.
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Senna and its main components sennosides are well-known effective laxative drugs and are used in the treatment of intestinal constipation in the world. Their potential side effects have attracted more attention in clinics but have little scientific justification. In this study, senna extract (SE), sennosides (SS), and sennoside A (SA) were prepared and used to generate diarrhea rats. The diarrhea rats were investigated with behaviors, clinical signs, organ index, pathological examination, and gene expression on multiple aquaporins (Aqps) including Aqp1, Aqp2, Aqp3, Aqp4, Aqp5, Aqp6, Aqp7, Aqp8, Aqp9, and Aqp11. Using qRT-PCR, the Aqp expression profiles were constructed for six organs including colon, kidney, liver, spleen, lung, and stomach. The Aqp alteration profiles were characterized and was performed with Principle Component Analysis (PCA). The SE treatments on the rats resulted in a significant body weight loss (p < 0.001), significant increases (p < 0.001) on the kidney index (27.72%) and liver index (42.55%), and distinguished changes with up-regulation on Aqps expressions in the kidneys and livers. The SS treatments showed prominent laxative actions and down regulation on Aqps expression in the colons. The study results indicated that the SE had more influence/toxicity on the kidneys and livers. The SS showed more powerful actions on the colons. We suggest that the caution should be particularly exercised in the patients with kidney and liver diseases when chronic using senna-based products.
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de Oliveira, Vanessa, Jennifer Schaefer, Basim Abu-Rafea, George A. Vilos, Angelos G. Vilos, Moshmi Bhattacharya, Sally Radovick, and Andy V. Babwah. "Uterine aquaporin expression is dynamically regulated by estradiol and progesterone and ovarian stimulation disrupts embryo implantation without affecting luminal closure." Molecular Human Reproduction 26, no. 3 (January 16, 2020): 154–66. http://dx.doi.org/10.1093/molehr/gaaa007.
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Abstract The study investigated the effect of normal and supraphysiological (resulting from gonadotropin-dependent ovarian stimulation) levels of estradiol (E2) and progesterone (P4) on mouse uterine aquaporin gene/protein (Aqp/AQP) expression on Day 1 (D1) and D4 of pregnancy. The study also examined the effect of ovarian stimulation on uterine luminal closure and uterine receptivity on D4 of pregnancy and embryo implantation on D5 and D7 of pregnancy. These analyses revealed that the expression of Aqp3, Aqp4, Aqp5 and Aqp8 is induced by E2 while the expression of Aqp1 and Aqp11 is induced by P4. Additionally, P4 inhibits E2 induction of Aqp3 and Aqp4 expression while E2 inhibits Aqp1 and Aqp11 expression. Aqp9, however, is constitutively expressed. Ovarian stimulation disrupts Aqp3, Aqp5 and Aqp8 expression on D4 and AQP1, AQP3 and AQP5 spatial expression on both D1 and D4, strikingly so in the myometrium. Interestingly, while ovarian stimulation has no overt effect on luminal closure and uterine receptivity, it reduces implantation events, likely through a disruption in myometrial activity and embryo development. The wider implication of this study is that ovarian stimulation, which results in supraphysiological levels of E2 and P4 and changes (depending on the degree of stimulation) in the E2:P4 ratio, triggers abnormal expression of uterine AQP during pregnancy, and this is associated with implantation failure. These findings lead us to recognize that abnormal expression would also occur under any pathological state (such as endometriosis) that is associated with changes in the normal E2:P4 ratio. Thus, infertility among these patients might in part be linked to abnormal uterine AQP expression.
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Hurley, Patricia T., Carole J. Ferguson, Tae-Hwan Kwon, Marie-Louise E. Andersen, Alexander G. Norman, Martin C. Steward, Søren Nielsen, and R. Maynard Case. "Expression and immunolocalization of aquaporin water channels in rat exocrine pancreas." American Journal of Physiology-Gastrointestinal and Liver Physiology 280, no. 4 (April 1, 2001): G701—G709. http://dx.doi.org/10.1152/ajpgi.2001.280.4.g701.
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Both the acinar and ductal cells of the pancreas secrete a near-isotonic fluid and may thus be sites of aquaporin (AQP) water channel expression. Northern blot analysis of mRNA from whole rat pancreas revealed high levels of AQP1 and AQP8 expression, whereas lower levels of AQP4 and AQP5 expression were just detectable by RT-PCR Southern blot analysis. Immunohistochemistry showed that AQP1 is localized in the microvasculature, whereas AQP8 is confined to the apical pole of the acinar cells. No labeling of acinar, ductal, or vascular tissue was detected with antibodies to AQP2–7. With immunoelectron microscopy, AQP8 labeling was observed not only at the apical membrane of the acinar cells but also among small intracellular vesicles in the subapical cytoplasm, suggesting that there may be regulated trafficking of AQP8 to the apical plasma membrane. To evaluate the contribution of AQPs to the membrane water permeability, video microscopy was used to measure the swelling of acinar cells in response to hypotonic stress. Osmotic water permeability was reduced by 90% following exposure to Hg2+. Since AQP8 is confined to the apical membrane, the marked effect of Hg2+ suggests that other water channels may be expressed in the basolateral membrane.
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Zhou, Zuoyi, Jiangshan Zhan, Qingyun Cai, Fanqing Xu, Ruichao Chai, Kalista Lam, Zuo Luan, et al. "The Water Transport System in Astrocytes–Aquaporins." Cells 11, no. 16 (August 18, 2022): 2564. http://dx.doi.org/10.3390/cells11162564.
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Astrocytes have distinctive morphological and functional characteristics, and are found throughout the central nervous system. Astrocytes are now known to be far more than just housekeeping cells in the brain. Their functions include contributing to the formation of the blood–brain barrier, physically and metabolically supporting and communicating with neurons, regulating the formation and functions of synapses, and maintaining water homeostasis and the microenvironment in the brain. Aquaporins (AQPs) are transmembrane proteins responsible for fast water movement across cell membranes. Various subtypes of AQPs (AQP1, AQP3, AQP4, AQP5, AQP8 and AQP9) have been reported to be expressed in astrocytes, and the expressions and subcellular localizations of AQPs in astrocytes are highly correlated with both their physiological and pathophysiological functions. This review describes and summarizes the recent advances in our understanding of astrocytes and AQPs in regard to controlling water homeostasis in the brain. Findings regarding the features of different AQP subtypes, such as their expression, subcellular localization, physiological functions, and the pathophysiological roles of astrocytes are presented, with brain edema and glioma serving as two representative AQP-associated pathological conditions. The aim is to provide a better insight into the elaborate “water distribution” system in cells, exemplified by astrocytes, under normal and pathological conditions.
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Okada, Naoko, Tetsuya Kawakita, Masataka Ito, and Kazuo Tsubota. "Aquaporins 8 and 9 as Possible Markers for Adult Murine Lacrimal Gland Cells." BioMed Research International 2021 (September 9, 2021): 1–9. http://dx.doi.org/10.1155/2021/6888494.
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Aquaporins (AQPs) are proteins that selectively transport water across the cell membrane. Although AQPs play important roles in secretion in the lacrimal gland, the expression and localization of AQPs have not been clarified yet. In the current study, we investigated the expression pattern of AQP family members in the murine lacrimal gland during development. Lacrimal gland tissues were harvested from E13.5 and E17.5 murine embryos and from mice 8 weeks of age (adults). Corneal and conjunctival tissues from the latter served as controls. Total RNA was isolated and analyzed for the expression of AQP family members using qPCR. The localization of AQPs in the adult lacrimal gland in adult murine lacrimal glands was also analyzed. Expression of Aqp8 and Aqp9 mRNAs was detected in the adult lacrimal gland but not in the cornea, conjunctiva, or fetal lacrimal gland. AQP8 and AQP9 and α-SMA partially colocalized around the basal regions of the acinar unit. The levels of Aqp3 mRNAs and protein were much lower in the adult lacrimal gland but were readily detected in the adult cornea and conjunctiva. Our study suggests that AQP8 and AQP9 may serve as markers for adult murine lacrimal gland, ductal, and myoepithelial cells.
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He, Jinzhao, and Baoxue Yang. "Aquaporins in Renal Diseases." International Journal of Molecular Sciences 20, no. 2 (January 16, 2019): 366. http://dx.doi.org/10.3390/ijms20020366.
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Aquaporins (AQPs) are a family of highly selective transmembrane channels that mainly transport water across the cell and some facilitate low-molecular-weight solutes. Eight AQPs, including AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, AQP7, and AQP11, are expressed in different segments and various cells in the kidney to maintain normal urine concentration function. AQP2 is critical in regulating urine concentrating ability. The expression and function of AQP2 are regulated by a series of transcriptional factors and post-transcriptional phosphorylation, ubiquitination, and glycosylation. Mutation or functional deficiency of AQP2 leads to severe nephrogenic diabetes insipidus. Studies with animal models show AQPs are related to acute kidney injury and various chronic kidney diseases, such as diabetic nephropathy, polycystic kidney disease, and renal cell carcinoma. Experimental data suggest ideal prospects for AQPs as biomarkers and therapeutic targets in clinic. This review article mainly focuses on recent advances in studying AQPs in renal diseases.
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Yang, Jinying, Shengjun Yu, Guanglan Zhang, Zheng Zheng, Ping Li, Shanshan Mei, and Xinjia Han. "Different expressions of aquaporin water channels and macrophages infiltration in human cervix remodeling during pregnancy." Biology of Reproduction 106, no. 1 (October 19, 2021): 173–84. http://dx.doi.org/10.1093/biolre/ioab191.
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Abstract Despite aquaporin water channels (AQPs) play a critical role in maintaining water homeostasis in female reproductive tract and prompt a gradual increase in water content in cervical edema as pregnancy progressed, their relationship with macrophage infiltration and collagen content in human cervical remodeling need to be further investigated. This is the first study to examine the expression and localization of AQP3, AQP4, AQP5, AQP8, and macrophages simultaneously in human cervical ripening. The immunoreactivity of these AQPs was 2.6 to 6-fold higher on gestational weeks 26 (GD26W) than that on GD6W and GD15W, but AQP4 expression on GD39W dropped a similar extent on GD15W, other AQPs continued to rise on GD39W. The AQP3, AQP4, and AQP5 intensity seemed more abundant in cervical stroma than in the perivascular area on GD26W; the distribution of AQP3, AQP5, and AQP8 in cervical stroma was equivalent to that in the perivascular area on GD39W. Macrophage numbers were 1.7-fold higher in subepithelium region and 3.0-fold higher in center area on GD26W than that on GD15W; such numbers remained elevated on GD39W. The electron micrographs showed that cervical extensibility increased significantly on GD26W and GD39W accompanied with increased macrophage infiltration, cervical water content, and much more space among collagen fibers. These findings suggest that the upregulation of AQPs expression in human cervix is closely related to enhanced macrophage infiltration during pregnancy; there may be a positive feedback mechanism between them to lead the increase of water content and the degradation of collagen.
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Pellavio, Giorgia, Federica Todaro, Paola Alberizzi, Claudia Scotti, Giulia Gastaldi, Marco Lolicato, Claudia Omes, Laura Caliogna, Rossella E. Nappi, and Umberto Laforenza. "HPV Infection Affects Human Sperm Functionality by Inhibition of Aquaporin-8." Cells 9, no. 5 (May 17, 2020): 1241. http://dx.doi.org/10.3390/cells9051241.
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Human sperm cells express different aquaporins (AQPs), AQP3, 7, 8, 11, which are localized both in the plasma membrane and in intracellular structures. Besides cell volume regulation and end stage of cytoplasm removal during sperm maturation, the role of AQPs extends also to reactive oxygen species (ROS) elimination. Moreover, oxidative stress has been shown to inhibit AQP-mediated H2O2 permeability. A decrease in AQPs functionality is related to a decrease in sperm cells number and motility. Here we investigate the possible effect of human Papillomavirus (HPV) on both expression and function of AQPs in human sperm cells of patients undergoing infertility couple evaluation. Stopped-flow light-scattering experiments demonstrated that HPV infection heavily reduced water permeability of sperm cells in normospermic samples. Confocal immunofluorescence experiments showed a colocalization of HPV L1 protein with AQP8 (Pearson’s correlation coefficient of 0.61), confirmed by co-immunoprecipitation experiments. No interaction of HPV with AQP3 and AQP7 was observed. A 3D model simulation of L1 protein and AQP8 interaction was also performed. Present findings may suggest that HPV infection directly inhibits AQP8 functionality and probably makes sperm cells more sensitive to oxidative stress.
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Koyama, Yu, Tadashi Yamamoto, Tatsuo Tani, Kouei Nihei, Daisuke Kondo, Haruko Funaki, Eishin Yaoita, et al. "Expression and localization of aquaporins in rat gastrointestinal tract." American Journal of Physiology-Cell Physiology 276, no. 3 (March 1, 1999): C621—C627. http://dx.doi.org/10.1152/ajpcell.1999.276.3.c621.
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A family of water-selective channels, aquaporins (AQP), has been demonstrated in various organs and tissues. However, the localization and expression of the AQP family members in the gastrointestinal tract have not been entirely elucidated. This study aimed to demonstrate the expression and distribution of several types of the AQP family and to speculate on their role in water transport in the rat gastrointestinal tract. By RNase protection assay, expression of AQP1–5 and AQP8 was examined in various portions through the gastrointestinal tract. AQP1 and AQP3 mRNAs were diffusely expressed from esophagus to colon, and their expression was relatively intense in the small intestine and colon. In contrast, AQP4 mRNA was selectively expressed in the stomach and small intestine and AQP8 mRNA in the jejunum and colon. Immunohistochemistry and in situ hybridization demonstrated cellular localization of these AQP in these portions. AQP1 was localized on endothelial cells of lymphatic vessels in the submucosa and lamina propria throughout the gastrointestinal tract. AQP3 was detected on the circumferential plasma membranes of stratified squamous epithelial cells in the esophagus and basolateral membranes of cardiac gland epithelia in the lower stomach and of surface columnar epithelia in the colon. However, AQP3 was not apparently detected in the small intestine. AQP4 was present on the basolateral membrane of the parietal cells in the lower stomach and selectively in the basolateral membranes of deep intestinal gland cells in the small intestine. AQP8 mRNA expression was demonstrated in the absorptive columnar epithelial cells of the jejunum and colon by in situ hybridization. These findings may indicate that water crosses the epithelial layer through these water channels, suggesting a possible role of the transcellular route for water intake or outlet in the gastrointestinal tract.
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Choi, Young Sik, Ji Hyun Park, Jeong-Kee Yoon, Ji Sun Yoon, Jung Sook Kim, Jae Hoon Lee, Bo Hyun Yun, et al. "Potential roles of aquaporin 9 in the pathogenesis of endometriosis." MHR: Basic science of reproductive medicine 25, no. 7 (May 9, 2019): 373–84. http://dx.doi.org/10.1093/molehr/gaz025.
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AbstractAquaporins (AQPs) are involved in cell migration, proliferation and carcinogenesis in tumor development and physiologic inflammatory processes, but their associations with endometriosis have not been fully evaluated. In this study, tissue samples were obtained from women undergoing laparoscopic surgery for endometriosis and other benign conditions. Analysis of expressions of AQP subtypes in eutopic and ectopic endometrium of patients with endometriosis (Eu-EMS and Ect-EMS, respectively) and eutopic endometrium of control patients without endometriosis (Eu-CTL) were performed using the NanoString nCounter System and western blotting. Human endometrial stromal cells (HESCs) were cultured and transfected with the siRNA of the AQP of interest. Among the AQP1–9 subtypes, endometrial expression of AQP2 and AQP8 was significantly increased, whereas AQP9 expression was significantly decreased in the Eu-EMS group compared to the Eu-CTL group. Comparison of expression of AQP2, AQP8 and AQP9 among Eu-EMS, Ect-EMS and Eu-CTL groups revealed significant differences for only AQP9. Expression of AQP9 in the Eu-EMS group was decreased compared with that in Eu-CTL. After transfection of AQP9 siRNA in HESCs, expressions of MMP2 and MMP9 were significantly elevated. Increased expression of phosphorylated ERK 1/2 and phosphorylated p38 MAPK proteins after transfection was also confirmed using western blot analysis. Increased migration and invasion potentials of HESCs after transfection were determined by migration and wound healing assays. These findings suggest that AQP9 may be involved in the pathogenesis of endometriosis and warrant further investigation as a potential therapeutic target for treating endometriosis.
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Chow, Pak Hin, Joanne Bowen, and Andrea J. Yool. "Combined Systematic Review and Transcriptomic Analyses of Mammalian Aquaporin Classes 1 to 10 as Biomarkers and Prognostic Indicators in Diverse Cancers." Cancers 12, no. 7 (July 15, 2020): 1911. http://dx.doi.org/10.3390/cancers12071911.
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Aquaporin (AQP) channels enable regulated transport of water and solutes essential for fluid homeostasis, but they are gaining attention as targets for anticancer therapies. Patterns of AQP expression and survival rates for patients were evaluated by systematic review (PubMed and Embase) and transcriptomic analyses of RNAseq data (Human Protein Atlas database). Meta-analyses confirmed predominantly negative associations between AQP protein and RNA expression levels and patient survival times, most notably for AQP1 in lung, breast and prostate cancers; AQP3 in esophageal, liver and breast cancers; and AQP9 in liver cancer. Patterns of AQP expression were clustered for groups of cancers and associated with risk of death. A quantitative transcriptomic analysis of AQP1-10 in human cancer biopsies similarly showed that increased transcript levels of AQPs 1, 3, 5 and 9 were most frequently associated with poor survival. Unexpectedly, increased AQP7 and AQP8 levels were associated with better survival times in glioma, ovarian and endometrial cancers, and increased AQP11 with better survival in colorectal and breast cancers. Although molecular mechanisms of aquaporins in pathology or protection remain to be fully defined, results here support the hypothesis that overexpression of selected classes of AQPs differentially augments cancer progression. Beyond fluid homeostasis, potential roles for AQPs in cancers (suggested from an expanding appreciation of their functions in normal tissues) include cell motility, membrane process extension, transport of signaling molecules, control of proliferation and apoptosis, increased mechanical compliance, and gas exchange. AQP expression also has been linked to differences in sensitivity to chemotherapy treatments, suggesting possible roles as biomarkers for personalized treatments. Development of AQP pharmacological modulators, administered in cancer-specific combinations, might inspire new interventions for controlling malignant carcinomas.
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Nah, Won Heum, Yeong Seok Oh, Jung Hye Hwang, and M. C. Gye. "Changes in aquaporin 5 in the non-ciliated cells of mouse oviduct according to sexual maturation and oestrous cycle." Reproduction, Fertility and Development 29, no. 2 (2017): 336. http://dx.doi.org/10.1071/rd15186.
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Aquaporin (AQP) water channels play an important role in fluid homeostasis and the control of epithelial cell volume. To understand the oviductal fluid homeostasis, the expression of aqp5 was examined in mouse oviduct. In the oviduct of cycling females, aqp1, aqp3, aqp4, aqp5, aqp6, aqp7, aqp8, and aqp11 mRNA were detected. Of these, expression of aqp5 mRNA increased significantly from the early prepubertal period to puberty. Epithelial AQP5 immunoreactivity was markedly increased during the same period and was most notable in the infundibulum. In immature female mice (3 weeks old), gonadotropin (pregnant mare’s serum gonadotropin (5 IU/head) and human chorionic gonadotropin (5 IU/head), single intraperitoneal injection) significantly increased oviductal aqp5 mRNA and AQP5 immunoreactivity in oviduct epithelia. In adult mouse oviduct epithelia, AQP5 was primarily found in the apical membrane, subapical cytoplasm and basolateral membrane of secretory non-ciliated cells, whereas weak to negligible immunoreactivity was found in β-tubulin-positive ciliated cells. Taking into account the fact that non-ciliated cells are well developed with subapical secretory vesicles as well as endosomes, AQP5 may also participate in the secretion and endocytosis in addition to water movement through non-ciliated secretory cells. AQP5 immunoreactivity was also found in the isthmic muscle and lamina propria beneath the epithelia. In cycling females, oviductal aqp5 mRNA levels were the highest at oestrus and the lowest at di-oestrus. AQP5 immunoreactivity in non-ciliated cells was notable in the infundibulum, where AQP5 immunoreactivity was relatively high at oestrus but low at dioestrus and pro-oestrus, indicating synchrony between aqp5 gene activation and the ovarian cycle. Together, the findings of the present study indicate that aqp5 specific to non-ciliated cells is activated during sexual maturation, supporting fluid homeostasis in mouse oviduct.
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Pellavio, Giorgia, Patrizia Sommi, Umberto Anselmi-Tamburini, Maria Paola DeMichelis, Stefania Coniglio, and Umberto Laforenza. "Cerium Oxide Nanoparticles Regulate Oxidative Stress in HeLa Cells by Increasing the Aquaporin-Mediated Hydrogen Peroxide Permeability." International Journal of Molecular Sciences 23, no. 18 (September 16, 2022): 10837. http://dx.doi.org/10.3390/ijms231810837.
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Some aquaporins (AQPs) allow the diffusion of hydrogen peroxide (H2O2), the most abundant ROS, through the cell membranes. Therefore, the possibility of regulating the AQP-mediated permeability to H2O2, and thus ROS scavenging, appears particularly important for controlling the redox state of cells in physiological and pathophysiological conditions. Several compounds have been screened and characterized for this purpose. This study aimed to analyze the effect of cerium oxide nanoparticles (CNPs) presenting antioxidant activity on AQP functioning. HeLa cells express AQP3, 6, 8, and 11, able to facilitate H2O2. AQP3, 6, and 8 are expressed in the plasma membrane and intracellularly, while AQP11 resides only in intracellular structures. CNPs but not cerium ions treatment significantly increased the water and H2O2 permeability by interacting with AQP3, 6, and especially with AQP8. CNPs increased considerably the AQP-mediated water diffusion in cells with oxidative stress. Functional experiments with silenced HeLa cells revealed that CNPs increased the H2O2 diffusion mainly by modulating the AQP8 permeability but also the AQP3 and AQP6, even if to a lesser extent. Current findings suggest that CNPs represent a promising pharmaceutical agent that might potentially be used in numerous pathologies involving oxidative stress as tumors and neurodegenerative diseases.
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Zhao, Wen-Xiao, Ning Cui, Hai-Qiang Jiang, Xu-Ming Ji, Xiao-Chun Han, Bing-Bing Han, Tong Wang, and Shi-Jun Wang. "Effects of Radix Astragali and Its Split Components on Gene Expression Profiles Related to Water Metabolism in Rats with the Dampness Stagnancy due to Spleen Deficiency Syndrome." Evidence-Based Complementary and Alternative Medicine 2017 (2017): 1–10. http://dx.doi.org/10.1155/2017/4946031.
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Radix Astragali (RA) with slight sweet and warm property is a significant “qi tonifying” herb; it is indicated for the syndrome of dampness stagnancy due to spleen deficiency (DSSD). The purpose of this research was to explore effects of RA and its split components on gene expression profiles related to water metabolism in rats with the DSSD syndrome for identifying components representing property and flavor of RA. The results indicated that RA and its split components, especially polysaccharides component, significantly increased the body weight and the urine volume and decreased the water load index of model rats. Our data also indicated differentially expressed genes (DEGs) related to water metabolism involved secretion, ion transport, water homeostasis, regulation of body fluid levels, and water channel activity; the expression of AQP1, AQP3, AQP4, AQP5, AQP6, and AQP8 was improved; calcium, cAMP, MAPK, PPAR, AMPK, and PI3K-Akt signaling pathway may be related to water metabolism. In general, results indicate that RA and its split components could promote water metabolism in rats with the DSSD syndrome via regulating the expression of AQPs, which reflected sweet-warm properties of RA. Effects of the polysaccharides component are better than others.
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Nishimura, Hiroko, and Yimu Yang. "Aquaporins in avian kidneys: function and perspectives." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, no. 11 (December 1, 2013): R1201—R1214. http://dx.doi.org/10.1152/ajpregu.00177.2013.
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For terrestrial vertebrates, water economy is a prerequisite for survival, and the kidney is their major osmoregulatory organ. Birds are the only vertebrates other than mammals that can concentrate urine in adaptation to terrestrial environments. Aquaporin (AQP) and glyceroporin (GLP) are phylogenetically old molecules and have been found in plants, microbial organisms, invertebrates, and vertebrates. Currently, 13 AQPs/aquaGLPs and isoforms are known to be present in mammals. AQPs 1, 2, 3, 4, 6, 7, 8, and 11 are expressed in the kidney; of these, AQPs 1, 2, 3, 4, and 7 are shown to be involved in fluid homeostasis. In avian kidneys, AQPs 1, 2, 3, and 4 have been identified and characterized. Also, gene and/or amino acid sequences of AQP5, AQP7, AQP8, AQP9, AQP11, and AQP12 have been reported in birds. AQPs 2 and 3 are expressed along cortical and medullary collecting ducts (CDs) and are responsible, respectively, for the water inflow and outflow of CD epithelial cells. While AQP4 plays an important role in water exit in the CD of mammalian kidneys, it is unlikely to participate in water outflow in avian CDs. This review summarizes current knowledge on structure and function of avian AQPs and compares them to those in mammalian and nonmammalian vertebrates. Also, we aim to provide input into, and perspectives on, the role of renal AQPs in body water homeostasis during ontogenic and phylogenetic advancement.
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Ruan, Wenbin, Yinghui Dong, Zhihua Lin, and Lin He. "Molecular Characterization of Aquaporins Genes from the Razor Clam Sinonovacula constricta and Their Potential Role in Salinity Tolerance." Fishes 7, no. 2 (March 18, 2022): 69. http://dx.doi.org/10.3390/fishes7020069.
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Aquaporins (AQPs) play crucial roles in osmoregulation, but the knowledge about the functions of AQPs in Sinonovacula constricta is unclear. In this study, Sc-AQP1, Sc-AQP8, and Sc-AQP11 were identified from S. constricta, and the three Sc-AQPs are highly conserved compared to the known AQPs. The qRT-PCR analysis revealed that the highest mRNA expressions of Sc-AQP1, Sc-AQP8, and Sc-AQP11 were detected in the gill, digestive gland, and adductor muscle, respectively. In addition, the highest mRNA expression of Sc-AQP1 and Sc-AQP11 was detected in the D-shaped larvae stage, whereas that of SC-AQP8 was observed in the umbo larvae stage. The mRNA expression of Sc-AQP1, Sc-AQP8, and Sc-AQP11 significantly increased to 12.45-, 12.36-, and 27.44-folds post-exposure of low salinity (3.5 psu), while only Sc-AQP1 and Sc-AQP11 significantly increased post-exposure of high salinity (35 psu) (p < 0.01). The fluorescence in situ hybridization also showed that the salinity shift led to the boost of Sc-AQP1, Sc-AQP8, and Sc-AQP11 mRNA expression in gill filament, digestive gland, and adductor muscle, respectively. Knockdown of the Sc-AQP1 and Sc-AQP8 led to the decreased osmotic pressure in the hemolymph. Overall, these findings would contribute to the comprehension of the osmoregulation pattern of AQPs in S. constricta.
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Yang, Baoxue, Yuanlin Song, Dan Zhao, and A. S. Verkman. "Phenotype analysis of aquaporin-8 null mice." American Journal of Physiology-Cell Physiology 288, no. 5 (May 2005): C1161—C1170. http://dx.doi.org/10.1152/ajpcell.00564.2004.
Full textAbstract:
Aquaporin-8 (AQP8) is a water-transporting protein expressed in organs of the mammalian gastrointestinal tract (salivary gland, liver, pancreas, small intestine, and colon) and in the testes, heart, kidney, and airways. We studied the phenotype of AQP8-null mice, and mice lacking AQP8, together with AQP1 or AQP5. AQP8-knockout mice lacked detectable AQP8 transcript and protein, and had reduced water permeability in plasma membranes from testes. Breeding of AQP8 heterozygous mice yielded AQP8-null mice, whose number, survival, and growth were not different from those of wild-type mice. Organ weight and serum/urine chemistries were similar in wild-type and AQP8-null mice, except for increased testicular weight in the null mice (4.8 ± 0.7 vs. 7.3 ± 0.3 mg/g body wt). Urinary concentrating ability in AQP8-null mice was unimpaired as assessed by urine osmolality (3,590 ± 360 mosmol/kgH2O) and weight loss (22 ± 2%) after 36-h water deprivation; urinary concentrating ability was similarly impaired in AQP1-null mice vs. AQP8/AQP1 double-knockout mice. Agonist-driven fluid secretion in salivary gland was not different in AQP8 vs. wild-type mice (∼1 μl·min−1·g body wt−1) or in AQP5-null mice vs. AQP8/AQP5 double-knockout mice. Closed intestinal loop measurements in vivo indicated unimpaired osmotically driven water transport, active fluid absorption, and cholera toxin-driven fluid secretion in AQP8-null mice. After 21 days on a 50% fat diet, wild-type and AQP8-null mice had similar weight gain (∼15 g), with no evidence of steatorrhea or abnormalities in blood chemistries, except for mild hypertriglyceridemia in the null mice. The mild phenotype of AQP8-null mice was surprising in view of the multiple phenotype abnormalities found in mouse models of AQP1–5 deficiency.
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Verkman, A. S., and Alok K. Mitra. "Structure and function of aquaporin water channels." American Journal of Physiology-Renal Physiology 278, no. 1 (January 1, 2000): F13—F28. http://dx.doi.org/10.1152/ajprenal.2000.278.1.f13.
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The aquaporins (AQPs) are a family of small membrane-spanning proteins (monomer size ∼30 kDa) that are expressed at plasma membranes in many cells types involved in fluid transport. This review is focused on the molecular structure and function of mammalian aquaporins. Basic features of aquaporin structure have been defined using mutagenesis, epitope tagging, and spectroscopic and freeze-fracture electron microscopy methods. Aquaporins appear to assemble in membranes as homotetramers in which each monomer, consisting of six membrane-spanning α-helical domains with cytoplasmically oriented amino and carboxy termini, contains a distinct water pore. Medium-resolution structural analysis by electron cryocrystallography indicated that the six tilted helical segments form a barrel surrounding a central pore-like region that contains additional protein density. Several of the mammalian aquaporins (e.g., AQP1, AQP2, AQP4, and AQP5) appear to be highly selective for the passage of water, whereas others (recently termed aquaglyceroporins) also transport glycerol (e.g., AQP3 and AQP8) and even larger solutes (AQP9). Evidence for possible movement of ions and carbon dioxide through the aquaporins is reviewed here, as well as evidence for direct regulation of aquaporin function by posttranslational modification such as phosphorylation. Important unresolved issues include definition of the molecular pathway through which water and solutes move, the nature of monomer-monomer interactions, and the physiological significance of aquaporin-mediated solute movement. Recent results from knockout mice implicating multiple physiological roles of aquaporins suggest that the aquaporins may be suitable targets for drug discovery by structure-based and/or high-throughput screening strategies.
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Anderson, Judy, Naoko Brown, Mala S. Mahendroo, and Jeff Reese. "Utilization of Different Aquaporin Water Channels in the Mouse Cervix during Pregnancy and Parturition and in Models of Preterm and Delayed Cervical Ripening." Endocrinology 147, no. 1 (January 1, 2006): 130–40. http://dx.doi.org/10.1210/en.2005-0896.
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Biochemical changes of cervical connective tissue, including progressive disorganization of the collagen network and increased water content, occur during gestation to allow for cervical dilatation during labor, but the mechanisms that regulate cervical fluid balance are not fully understood. We examined whether aquaporins (AQPs), a family of membrane channel proteins that facilitate water transport, help mediate fluid balance in the mouse cervix during parturition. Of the 13 known murine AQPs, AQP0–2, 6, 7, 9, 11, and 12 were absent or at the limits of detection. By Northern blot and real-time PCR, AQP3 expression was low in nongravid and mid-pregnancy cervices with peak expression on d 19 and postpartum d 1 (PP1). AQP4 expression was generally low throughout pregnancy but showed a small upward trend at the time of parturition. AQP5 and AQP8 expression were significantly increased on d 12–15 but fell to nongravid/baseline by d 19 and PP1. By in situ hybridization and immunohistochemistry, AQP3 was preferentially expressed in basal cell layers of the cervical epithelium, whereas AQP4, 5, and 8 were primarily expressed in apical cell layers. Females with LPS-induced preterm labor had similar trends in AQP4, 5, and 8 expression to mice with natural labor at term gestation. Mice with delayed cervical remodeling due to deletion of the steroid 5α-reductase type 1 gene showed significant reduction in the levels of AQP3, 4, and 8 on d 19 or PP1. Together, these studies suggest that AQPs 3, 4, 5, and 8 regulate distinct aspects of cervical water balance during pregnancy and parturition.
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Nielsen, Søren, Jørgen Frøkiær, David Marples, Tae-Hwan Kwon, Peter Agre, and Mark A. Knepper. "Aquaporins in the Kidney: From Molecules to Medicine." Physiological Reviews 82, no. 1 (January 1, 2002): 205–44. http://dx.doi.org/10.1152/physrev.00024.2001.
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The discovery of aquaporin-1 (AQP1) answered the long-standing biophysical question of how water specifically crosses biological membranes. In the kidney, at least seven aquaporins are expressed at distinct sites. AQP1 is extremely abundant in the proximal tubule and descending thin limb and is essential for urinary concentration. AQP2 is exclusively expressed in the principal cells of the connecting tubule and collecting duct and is the predominant vasopressin-regulated water channel. AQP3 and AQP4 are both present in the basolateral plasma membrane of collecting duct principal cells and represent exit pathways for water reabsorbed apically via AQP2. Studies in patients and transgenic mice have demonstrated that both AQP2 and AQP3 are essential for urinary concentration. Three additional aquaporins are present in the kidney. AQP6 is present in intracellular vesicles in collecting duct intercalated cells, and AQP8 is present intracellularly at low abundance in proximal tubules and collecting duct principal cells, but the physiological function of these two channels remains undefined. AQP7 is abundant in the brush border of proximal tubule cells and is likely to be involved in proximal tubule water reabsorption. Body water balance is tightly regulated by vasopressin, and multiple studies now have underscored the essential roles of AQP2 in this. Vasopressin regulates acutely the water permeability of the kidney collecting duct by trafficking of AQP2 from intracellular vesicles to the apical plasma membrane. The long-term adaptational changes in body water balance are controlled in part by regulated changes in AQP2 and AQP3 expression levels. Lack of functional AQP2 is seen in primary forms of diabetes insipidus, and reduced expression and targeting are seen in several diseases associated with urinary concentrating defects such as acquired nephrogenic diabetes insipidus, postobstructive polyuria, as well as acute and chronic renal failure. In contrast, in conditions with water retention such as severe congestive heart failure, pregnancy, and syndrome of inappropriate antidiuretic hormone secretion, both AQP2 expression levels and apical plasma membrane targetting are increased, suggesting a role for AQP2 in the development of water retention. Continued analysis of the aquaporins is providing detailed molecular insight into the fundamental physiology and pathophysiology of water balance and water balance disorders.
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Petano-Duque, Julieth M., Rafael E. Castro-Vargas, Juan S. Cruz-Mendez, Kelly J. Lozano-Villegas, María P. Herrera-Sánchez, Heinner F. Uribe-García, Juan S. Naranjo-Gómez, Rafael J. Otero-Arroyo, and Iang S. Rondón-Barragán. "Gene Expression of Aquaporins (AQPs) in Cumulus Oocytes Complex and Embryo of Cattle." Animals 13, no. 1 (December 27, 2022): 98. http://dx.doi.org/10.3390/ani13010098.
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Aquaporins (AQPs) are proteins with various functions related to proper cell function and early development in mammals. The aim of this study was to evaluate the presence of AQPs and determine their mRNA levels in the cumulus oocyte complex (COC) of four bovine breeds and in blastocysts of five bovine crosses. Grade I, II and III COCs were collected by ovum pick up from non-lactating heifers of the Brahaman, Holstein, Gir and Romosinuano breeds. Embryos were produced in vitro up to the blastocyst stage of the bovine ♀Gir × ♂Holstein, ♀Holstein × ♂Gir, ♀Brahman × ♂Holstein, ♀Holstein × ♂Brahman, and ♀Romosinuano × ♂Holstein crosses. mRNA expression of AQP1-AQP12b was estimated in COC and embryos by real-time-PCR. The presence of the twelve AQPs in the COCs and bovine embryos was established. Additionally, significant differences were determined in the expression of AQP6 and AQP12b in COCs, as well as in transcripts levels of AQP4, AQP8 and AQP9 from bovine embryos. Gene expression of AQPs in COCs and bovine embryos is consistent with the previously described biological functions. This is the first report of AQPs in COC of Gir, Brahman, Holstein and Romosinuano and embryos of five crossbreeds between Bos indicus and B. taurus.
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Wang, Weidong, Chunling Li, Tae-Hwan Kwon, Mark A. Knepper, Jørgen Frøkiær, and Søren Nielsen. "AQP3, p-AQP2, and AQP2 expression is reduced in polyuric rats with hypercalcemia: prevention by cAMP-PDE inhibitors." American Journal of Physiology-Renal Physiology 283, no. 6 (December 1, 2002): F1313—F1325. http://dx.doi.org/10.1152/ajprenal.00040.2002.
Full textAbstract:
The purpose of this study was to evaluate whether hypercalcemia is associated with downregulation of renal aquaporins (AQPs), including AQP1, AQP2, phosphorylated AQP2 (p-AQP2), AQP3, and AQP4, and if this is the case, to test whether cAMP-phosphodiesterase (PDE) inhibitor treatment can prevent AQP downregulation and prevent the development of polyuria. Vitamin D-induced hypercalcemia in rats was associated with increased urine output and reduced urine osmolality, consistent with previous findings (Levi M, Peterson L, and Berl T. Kidney Int 23: 489–497, 1983). Semiquantitative immunoblotting revealed a significant reduction in the abundance of inner medullary AQP2 (52 ± 6% of control levels), consistent with previous studies, and of AQP2, which is phosphorylated at the PKA phosphorylation consensus site serine 256 (p-AQP2; 36 ± 8%). Moreover, AQP3 abundance was also significantly decreased (45 ± 7 and 61 ± 6% of control levels in inner medulla and whole kidney, respectively). Consistent with this, immunohistochemistry demonstrated reduced AQP3 immunolabeling along the entire collecting duct. AQP4 expression was not reduced. Surprisingly, total kidney AQP1 abundance was also reduced (60 ± 6%). AQP1 expression was reduced in the cortex and outer stripe of the outer medulla (48 ± 7%; i.e., in proximal tubules). In contrast, AQP1 levels were not changed in the inner stripe of the outer medulla or in the inner medulla (i.e., descending thin limbs and vasa recta). Treatment with the cAMP-PDE inhibitors rolipram and milrinone in combination (inhibiting PDE IV and PDE III isoenzymes) at day 2 and onward completely prevented the hypercalcemia-induced downregulation of AQP2 and AQP3 (but not AQP1) and completely prevented the development of polyuria. In conclusion, AQP3, AQP2, and p-AQP2 are downregulated and are likely to play critical roles in the development of polyuria associated with vitamin D-induced hypercalcemia. Moreover, PDE inhibitor treatment significantly prevented the reduced expression of collecting duct AQPs and prevented the development of polyuria.
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Mucciolo, Serena, Andrea Desiderato, Marika Salonna, Tomasz Mamos, Viviane Prodocimo, Maikon Di Domenico, Francesco Mastrototaro, Paulo Lana, Carmela Gissi, and Giuseppe Calamita. "Finding Aquaporins in Annelids: An Evolutionary Analysis and a Case Study." Cells 10, no. 12 (December 17, 2021): 3562. http://dx.doi.org/10.3390/cells10123562.
Full textAbstract:
Aquaporins (AQPs) are a family of membrane channels facilitating diffusion of water and small solutes into and out of cells. Despite their biological relevance in osmoregulation and ubiquitous distribution throughout metazoans, the presence of AQPs in annelids has been poorly investigated. Here, we searched and annotated Aqp sequences in public genomes and transcriptomes of annelids, inferred their evolutionary relationships through phylogenetic analyses and discussed their putative physiological relevance. We identified a total of 401 Aqp sequences in 27 annelid species, including 367 sequences previously unrecognized as Aqps. Similar to vertebrates, phylogenetic tree reconstructions clustered these annelid Aqps in four clades: AQP1-like, AQP3-like, AQP8-like and AQP11-like. We found no clear indication of the existence of paralogs exclusive to annelids; however, several gene duplications seem to have occurred in the ancestors of some Sedentaria annelid families, mainly in the AQP1-like clade. Three of the six Aqps annotated in Alitta succinea, an estuarine annelid showing high salinity tolerance, were validated by RT-PCR sequencing, and their similarity to human AQPs was investigated at the level of “key” conserved residues and predicted three-dimensional structure. Our results suggest a diversification of the structures and functions of AQPs in Annelida comparable to that observed in other taxa.
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Verkman, A. S., Michael A. Matthay, and Yuanlin Song. "Aquaporin water channels and lung physiology." American Journal of Physiology-Lung Cellular and Molecular Physiology 278, no. 5 (May 1, 2000): L867—L879. http://dx.doi.org/10.1152/ajplung.2000.278.5.l867.
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Fluid transport across epithelial and endothelial barriers occurs in the neonatal and adult lungs. Biophysical measurements in the intact lung and cell isolates have indicated that osmotic water permeability is exceptionally high across alveolar epithelia and endothelia and moderately high across airway epithelia. This review is focused on the role of membrane water-transporting proteins, the aquaporins (AQPs), in high lung water permeability and lung physiology. The lung expresses several AQPs: AQP1 in microvascular endothelia, AQP3 in large airways, AQP4 in large- and small-airway epithelia, and AQP5 in type I alveolar epithelial cells. Lung phenotype analysis of transgenic mice lacking each of these AQPs has been informative. Osmotically driven water permeability between the air space and capillary compartments is reduced ∼10-fold by deletion of AQP1 or AQP5 and reduced even more by deletion of AQP1 and AQP4 or AQP1 and AQP5 together. AQP1 deletion greatly reduces osmotically driven water transport across alveolar capillaries but has only a minor effect on hydrostatic lung filtration, which primarily involves paracellular water movement. However, despite the major role of AQPs in lung osmotic water permeabilities, AQP deletion has little or no effect on physiologically important lung functions, such as alveolar fluid clearance in adult and neonatal lung, and edema accumulation after lung injury. Although AQPs play a major role in renal and central nervous system physiology, the data to date on AQP knockout mice do not support an important role of high lung water permeabilities or AQPs in lung physiology. However, there remain unresolved questions about possible non-water-transporting roles of AQPs and about the role of AQPs in airway physiology, pleural fluid dynamics, and edema after lung infection.
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Li, Chunling, Weidong Wang, Mark A. Knepper, Søren Nielsen, and Jørgen Frøkiær. "Downregulation of renal aquaporins in response to unilateral ureteral obstruction." American Journal of Physiology-Renal Physiology 284, no. 5 (May 1, 2003): F1066—F1079. http://dx.doi.org/10.1152/ajprenal.00090.2002.
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The expression of aquaporin-2 (AQP2) is decreased in rats with bilateral ureteral obstruction (BUO) and unilateral ureteral obstruction (UUO). Therefore, the expression of additional renal aquaporins (AQP1–4) and phosphorylated AQP2 (p-AQP2), known to play a role in urinary concentration, was examined in a Wistar rat model with 24 h of UUO. In obstructed kidneys, immunoblotting revealed a significant decrease in the expression of inner medullary AQP2 to 42 ± 4, p-AQP2 to 23 ± 5, AQP3 to 19 ± 6, AQP4 to 11 ± 5, and AQP1 to 64 ± 8% of sham levels. AQP1 expression located in the proximal tubule decreased to 74 ± 4% of sham levels ( P < 0.05). Immunocytochemistry confirmed the downregulation of AQP3, AQP4, and p-AQP2. In contralateral nonobstructed kidneys, immunoblotting also revealed significant reductions of AQP1 in the inner medulla, outer medulla, and cortex, whereas expression of AQP2, AQP3, AQP4, and p-AQP2 was unchanged. Furthermore, we collected the urine from both obstructed and nonobstructed kidneys for 2 h, respectively, after 24 h of UUO. Urine collection from obstructed kidneys during 2 h after release of UUO revealed a significant reduction in urine osmolality and solute-free water reabsorption (TcH2O). Moreover, an increase in urine production and TcH2O was observed in contralateral kidneys. To examine whether vasopressin-independent mechanisms are involved in AQP2 regulation, vasopressin-deficient Brattleboro (BB) rats with 24 h of UUO were examined. Immunoblotting revealed downregulation of AQP2, p-AQP2, AQP3, and AQP1 in obstructed kidneys and downregulation of p-AQP2 and AQP1 in nonobstructed kidneys. In conclusion, 1) UUO is associated with severe downregulation of AQP2, AQP3, AQP4, and AQP1; thus all of these AQPs may play important roles in the impaired urinary concentrating capacity in the obstructed kidney; 2) the reduced levels of AQP1 in the nonobstructed kidney may contribute to the compensatory increase in urine production; and 3) downregulation of AQPs in BB rats supports the view that vasopressin-independent pathways may be involved in AQP2 and AQP3 regulation in the obstructed kidney.
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Gonen, Tamir, and Thomas Walz. "The structure of aquaporins." Quarterly Reviews of Biophysics 39, no. 4 (November 2006): 361–96. http://dx.doi.org/10.1017/s0033583506004458.
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1. Introduction 3621.1 The elusive water pores 3621.2 CHIP28 3622. Studies on AQP-1 3632.1 Expression of AQP1 cDNA in Xenopus oocytes 3632.2 Reconstitution of purified AQP1 into artificial lipid bilayers 3642.3 Structural information deduced from the primary sequence 3652.4 Evolution and mammalian AQPs 3653. Chronological overview over AQP structures 3683.1 AQP1 – the red blood cell water pore 3683.2 GlpF – the E. coli glycerol facilitator 3713.3 AQPZ – the E. coli water pore 3723.4 AQP0 – the lens-specific aquaporin 3733.5 AQP4 – the main aquaporin in brain 3773.6 SoPiP2;1 – a plant aquaporin 3793.7 AQPM – an archaeabacterial aquaporin 3794. Proton exclusion 3805. Substrate selectivity 3826. Pore regulation 3856.1 Hormonal regulation of AQP trafficking 3856.2 Influence of pH on AQP water conduction 3866.3 Regulation of AQP pore conductance by protein binding 3876.4 Pore closure by conformational changes in the AQP0 pore 3887. Unresolved questions 3908. Acknowledgments 3909. References 391The ubiquitous members of the aquaporin (AQP) family form transmembrane pores that are either exclusive for water (aquaporins) or are also permeable for other small neutral solutes such as glycerol (aquaglyceroporins). The purpose of this review is to provide an overview of our current knowledge of AQP structures and to describe the structural features that define the function of these membrane pores. The review will discuss the mechanisms governing water conduction, proton exclusion and substrate specificity, and how the pore permeability is regulated in different members of the AQP family.
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Borok, Zea, and A. S. Verkman. "Lung Edema Clearance: 20 Years of Progress Invited Review: Role of aquaporin water channels in fluid transport in lung and airways." Journal of Applied Physiology 93, no. 6 (December 1, 2002): 2199–206. http://dx.doi.org/10.1152/japplphysiol.01171.2001.
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Water transport across epithelial and endothelial barriers in bronchopulmonary tissues occurs during airway hydration, alveolar fluid transport, and submucosal gland secretion. Many of the tissues involved in these processes are highly water permeable and express aquaporin (AQP) water channels. AQP1 is expressed in microvascular endothelia throughout the lung and airways, AQP3 in epithelia in large airways, AQP4 in epithelia throughout the airways, and AQP5 in type I alveolar epithelial cells and submucosal gland acinar cells. The expression of some of these AQPs increases near the time of birth and is regulated by growth factors, inflammation, and osmotic stress. Transgenic mouse models of AQP deletion have provided information about their physiological role. In lung, AQP1 and AQP5 provide the principal route for osmotically driven water transport; however, alveolar fluid clearance in the neonatal and adult lung is not affected by AQP deletion nor is lung CO2 transport or fluid accumulation in experimental models of lung injury. In the airways, AQP3 and AQP4 facilitate water transport; however, airway hydration, regulation of the airway surface liquid layer, and isosmolar fluid absorption are not impaired by AQP deletion. In contrast to these negative findings, AQP5 deletion in submucosal glands in upper airways reduced fluid secretion and increased protein content by greater than twofold. Thus, although AQPs play a major physiological role outside of the airways and lung, AQPs appear to be important mainly in airway submucosal gland function. The substantially slower rates of fluid transport in airways, pleura, and lung compared with renal and some secretory epithelia may account for the apparent lack of functional significance of AQPs at these sites. However, the possibility remains that AQPs may play a role in lung physiology under conditions of stress and/or injury not yet tested or in functions unrelated to transepithelial fluid transport.
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Yang, Baoxue, Hans G. Folkesson, Jian Yang, Michael A. Matthay, Tonghui Ma, and A. S. Verkman. "Reduced osmotic water permeability of the peritoneal barrier in aquaporin-1 knockout mice." American Journal of Physiology-Cell Physiology 276, no. 1 (January 1, 1999): C76—C81. http://dx.doi.org/10.1152/ajpcell.1999.276.1.c76.
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Aquaporin-1 (AQP1) water channels are expressed widely in epithelia and capillary endothelia involved in fluid transport. To test whether AQP1 facilitates water movement from capillaries into the peritoneal cavity, osmotically induced water transport rates were compared in AQP1 knockout [(−/−)], heterozygous [(+/−)], and wild-type [(+/+)] mice. In (+/+) mice, RT-PCR showed detectable transcripts for AQP1, AQP3, AQP4, AQP7, and AQP8. Immunofluorescence showed AQP1 protein in capillary endothelia and mesangium near the peritoneal surface and AQP4 in adherent muscle plasmalemma. For measurement of water transport, 2 ml of saline containing 300 mM sucrose (600 mosM) were infused rapidly into the peritoneal cavity via a catheter. Serial fluid samples (50 μl) were withdrawn over 60 min, with albumin as a volume marker. The albumin dilution data showed significantly decreased initial volume influx in AQP1 (−/−) mice: 101 ± 8, 107 ± 5, and 42 ± 4 (SE) μl/min in (+/+), (+/−), and (−/−) mice, respectively [ n = 6–10, P < 0.001, (−/−) vs. others]. Volume influx for AQP4 knockout mice was 100 ± 8 μl/min. In the absence of an osmotic gradient,3H2O uptake [half time = 2.3 and 2.2 min in (+/+) and (−/−) mice, respectively], [14C]urea uptake [half time = 7.9 and 7.7 min in (+/+) and (−/−) mice, respectively], and spontaneous isosmolar fluid absorption from the peritoneal cavity [0.47 ± 0.05 and 0.46 ± 0.04 ml/h in (+/+) and (−/−) mice, respectively] were not affected by AQP1 deletion. Therefore, AQP1 provides a major route for osmotically driven water transport across the peritoneal barrier in peritoneal dialysis.
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Hamann, Steffen, Thomas Zeuthen, Morten La Cour, Erlend A. Nagelhus, Ole Petter Ottersen, Peter Agre, and Søren Nielsen. "Aquaporins in complex tissues: distribution of aquaporins 1–5 in human and rat eye." American Journal of Physiology-Cell Physiology 274, no. 5 (May 1, 1998): C1332—C1345. http://dx.doi.org/10.1152/ajpcell.1998.274.5.c1332.
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Multiple physiological fluid movements are involved in vision. Here we define the cellular and subcellular sites of aquaporin (AQP) water transport proteins in human and rat eyes by immunoblotting, high-resolution immunocytochemistry, and immunoelectron microscopy. AQP3 is abundant in bulbar conjunctival epithelium and glands but is only weakly present in corneal epithelium. In contrast, AQP5 is prominent in corneal epithelium and apical membranes of lacrimal acini. AQP1 is heavily expressed in scleral fibroblasts, corneal endothelium and keratocytes, and endothelium covering the trabecular meshwork and Schlemm’s canal. Although AQP1 is plentiful in ciliary nonpigmented epithelium, it is not present in ciliary pigmented epithelium. Posterior and anterior epithelium of the iris and anterior lens epithelium also contain significant amounts of AQP1, but AQP0 (major intrinsic protein of the lens) is expressed in lens fiber cells. Retinal Müller cells and astrocytes exhibit notable concentrations of AQP4, whereas neurons and retinal pigment epithelium do not display aquaporin immunolabeling. These studies demonstrate selective expression of AQP1, AQP3, AQP4, and AQP5 in distinct ocular epithelia, predicting specific roles for each in the complex network through which water movements occur in the eye.
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Chou, C. L., Tonghui Ma, Baoxue Yang, Mark A. Knepper, and A. S. Verkman. "Fourfold reduction of water permeability in inner medullary collecting duct of aquaporin-4 knockout mice." American Journal of Physiology-Cell Physiology 274, no. 2 (February 1, 1998): C549—C554. http://dx.doi.org/10.1152/ajpcell.1998.274.2.c549.
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Aquaporin (AQP)-3 and AQP4 water channels are expressed at the basolateral membrane of mammalian collecting duct epithelium. To determine the contribution of AQP4 to water permeability in the initial inner medullary collecting duct (IMCD), osmotic water permeability ( P f) was compared in isolated perfused IMCD segments from wild-type and AQP4 knockout mice. The AQP4 knockout mice were previously found to have normal gross appearance, survival, growth, and kidney morphology and a mild urinary concentrating defect (T. Ma, B. Yang, A. Gillespie, E. J. Carlson, C. J. Epstein, and A. S. Verkman. J. Clin. Invest. 100: 957–962, 1997). Transepithelial P f was measured in microdissected IMCDs after 18–48 h of water deprivation and in the presence of 0.1 nM arginine vasopressin (to make basolateral P f rate limiting). P fvalues (37°C; means ± SE in cm/s × 10−3) were 56.0 ± 8.5 for wild-type mice ( n = 5) and 13.1 ± 3.7 for knockout mice ( n = 6) ( P < 0.001). Northern blot analysis of kidney showed that transcript expression of AQP1, AQP2, AQP3, and AQP6 were not affected by AQP4 deletion. Immunoblot analysis indicated no differences in protein expression of AQP1, AQP2, or AQP3, and immunoperoxidase showed no differences in staining patterns. Coexpression of AQP3 and AQP4 in Xenopus laevis oocytes showed additive water permeabilities, suggesting that AQP4 deletion does not affect AQP3 function. These results indicate that AQP4 is responsible for the majority of basolateral membrane water movement in IMCD but that its deletion is associated with a very mild defect in urinary concentrating ability.
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Lee, Sungeun, Hee-Gyoo Kang, Chongsuk Ryou, and Yong-Pil Cheon. "Spatiotemporal expression of aquaporin 9 is critical for the antral growth of mouse ovarian follicles†." Biology of Reproduction 103, no. 4 (June 24, 2020): 828–39. http://dx.doi.org/10.1093/biolre/ioaa108.
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Abstract Although a few aquaporins (AQPs) expressed in granulosa cells have been postulated to mediate fluid passage into the antrum, the specific expression of AQPs in different follicle cell types and stages and their roles have not been evaluated extensively. The spatiotemporal expression of aquaporin (Aqp) 7, 8, and 9 and the functional roles of Aqp9 in antral growth and ovulation were examined using a superovulation model and 3-dimensional follicle culture. Aqp9 was expressed at a high level in the rapid growth phase (24–48 h post equine chorionic gonadotropin (eCG) for superovulation induction) compared to Aqp7 (after human chorionic gonadotropin (hCG)) and Aqp8 (8–24 h post eCG and 24 h post hCG). A dramatic increase in the expression and localization of Aqp9 mRNA in theca cells was observed, as evaluated using quantitative reverse transcription-polymerase (RT-PCR) coupled with laser capture microdissection and immunohistochemistry. AQP9 was located primarily on the theca cells of the tertiary and preovulatory follicles but not on the ovulated follicles. In phloretin-treated mice, the diameter of the preovulatory follicles and the number of ovulated oocytes decreased. Consistent with these findings, knocking down Aqp9 expression with an Aqp9 siRNA inhibited follicle growth (0.28:1 = siRNA:control) and decreased the number of ovulated follicles (0.36:1 = siRNA:control) during in vitro growth and ovulation induction. Based on these results, the expression of AQPs is under the control of the physiological status, and AQP9 expression in theca during folliculogenesis is required for antral growth and ovulation in a tissue-specific and stage-dependent manner.
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Tritto, Simona, Giulia Gastaldi, Sergey Zelenin, Monica Grazioli, Maria Novella Orsenigo, Ulderico Ventura, Umberto Laforenza, and Marina Zelenina. "Osmotic water permeability of rat intestinal brush border membrane vesicles: involvement of aquaporin-7 and aquaporin-8 and effect of metal ions." Biochemistry and Cell Biology 85, no. 6 (December 2007): 675–84. http://dx.doi.org/10.1139/o07-142.
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Water channels AQP7 and AQP8 may be involved in transcellular water movement in the small intestine. We show that both AQP7 and AQP8 mRNA are expressed in rat small intestine. Immunoblot and immunohistochemistry experiments demonstrate that AQP7 and AQP8 proteins are present in the apical brush border membrane of intestinal epithelial cells. We investigated the effect of several metals and pH on the osmotic water permeability (Pf) of brush border membrane vesicles (BBMVs) and of AQP7 and AQP8 expressed in a cell line. Hg2+, Cu2+, and Zn2+ caused a significant decrease in the BBMV Pf, whereas Ni2+ and Li+ had no effect. AQP8-transfected cells showed a reduction in Pf in the presence of Hg2+ and Cu2+, whereas AQP7-transfected cells were insensitive to all tested metals. The Pf of both BBMVs and cells transfected with AQP7 and AQP8 was not affected by pH changes within the physiological range, and the Pf of BBMVs alone was not affected by phlorizin or amiloride. Our results indicate that AQP7 and AQP8 may play a role in water movement via the apical domain of small intestine epithelial cells. AQP8 may contribute to the water-imbalance-related clinical symptoms apparent after ingestion of high doses of Hg2+ and Cu2+.
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Squillacioti, Caterina, Nicola Mirabella, Giovanna Liguori, Giuseppe Germano, and Alessandra Pelagalli. "Aquaporins Are Differentially Regulated in Canine Cryptorchid Efferent Ductules and Epididymis." Animals 11, no. 6 (May 25, 2021): 1539. http://dx.doi.org/10.3390/ani11061539.
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The efferent ductules and the epididymis are parts of the male reproductive system where spermatozoa mature. Specialized epithelial cells in these ducts contribute to the transport of fluids produced by spermatozoa’s metabolic activity. Aquaporins (AQPs) have been demonstrated to be expressed in the spermatozoan membrane and testis epithelial cells, where they contribute to regulating spermatozoan volume and transit through environments of differing osmolality. Due to the lack of detailed literature regarding AQP expression in the canine male genital tract, the aim of this study was to investigate both the distribution and expression of AQP7, AQP8, and AQP9 in the efferent ductules and epididymal regions (caput, corpus, and cauda) from normal and cryptorchid dogs by using immunohistochemistry, Western blotting, and real-time reverse transcription polymerase chain reaction (RT-PCR). Our results show different patterns for the distribution and expression of the examined AQPs, with particular evidence of their upregulation in the caput and downregulation in the cauda region of the canine cryptorchid epididymis. These findings are associated with a modulation of Hsp70 and caspase-3 expression, suggesting the participation of AQPs in the luminal microenvironment modifications that are peculiar characteristics of this pathophysiological condition.
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Liu, Mi, Ying Sun, Man Xu, Xiaowen Yu, Yue Zhang, Songming Huang, Guixia Ding, Aihua Zhang, and Zhanjun Jia. "Role of mitochondrial oxidative stress in modulating the expressions of aquaporins in obstructive kidney disease." American Journal of Physiology-Renal Physiology 314, no. 4 (April 1, 2018): F658—F666. http://dx.doi.org/10.1152/ajprenal.00234.2017.
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Downregulation of aquaporins (AQPs) in obstructive kidney disease has been well demonstrated with elusive mechanisms. Our previous study indicated that mitochondrial dysfunction played a crucial role in this process. However, it is still uncertain how mitochondrial dysfunction affected the AQPs in obstructive kidney disease. This study investigated the role of mitochondria-derived oxidative stress in mediating obstruction-induced downregulation of AQPs. After unilateral ureteral obstruction for 7 days, renal superoxide dismutase 2 (SOD2; mitochondria-specific SOD) was reduced by 85%. Meanwhile, AQP1, AQP2, AQP3, and AQP4 were remarkably downregulated as determined by Western blotting and/or quantitative real-time PCR. Administration of the SOD2 mimic manganese (III) tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP) significantly attenuated AQP2 downregulation in line with complete blockade of thiobarbituric acid-reactive substances elevation, whereas the reduction of AQP1, AQP3, and AQP4 was not affected. The cyclooxygenase (COX)-2/prostaglandin (PG) E2 pathway has been well documented as a contributor of AQP reduction in obstructed kidney; thus, we detected the levels of COX-1/2 and microsomal prostaglandin E synthase 1 (mPGES-1) in kidney and PGE2 secretion in urine. Significantly, MnTBAP partially suppressed the elevation of COX-2, mPGES-1, and PGE2. Moreover, a marked decrease of V2 receptor was significantly restored after MnTBAP treatment. However, the fibrotic response and renal tubular damage were unaffected by MnTBAP in obstructed kidneys. Collectively, these findings suggested an important role of mitochondrial oxidative stress in mediating AQP2 downregulation in obstructed kidney, possibly via modulating the COX-2/mPGES-1/PGE2/V2 receptor pathway.
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Carreras, Flavia I., Guillermo L. Lehmann, Domenico Ferri, Mariana F. Tioni, Giuseppe Calamita, and Raúl A. Marinelli. "Defective hepatocyte aquaporin-8 expression and reduced canalicular membrane water permeability in estrogen-induced cholestasis." American Journal of Physiology-Gastrointestinal and Liver Physiology 292, no. 3 (March 2007): G905—G912. http://dx.doi.org/10.1152/ajpgi.00386.2006.
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Our previous work supports a role for aquaporin-8 (AQP8) water channels in rat hepatocyte bile formation mainly by facilitating the osmotically driven canalicular secretion of water. In this study, we tested whether a condition with compromised canalicular bile secretion, i.e., the estrogen-induced intrahepatic cholestasis, displays defective hepatocyte AQP8 functional expression. After 17α-ethinylestradiol administration (5 mg·kg body wt−1·day−1 for 5 days) to rats, the bile flow was reduced by 58% ( P < 0.05). By subcellular fractionation and immunoblotting analysis, we found that 34 kDa AQP8 was significantly decreased by ∼70% in plasma (canalicular) and intracellular (vesicular) liver membranes. However, 17α-ethinylestradiol-induced cholestasis did not significantly affect the protein level or the subcellular localization of sinusoidal AQP9. Immunohistochemistry for liver AQPs confirmed these observations. Osmotic water permeability ( Pf) of canalicular membranes, measured by stopped-flow spectrophotometry, was significantly reduced (73 ± 1 vs. 57 ± 2 μm/s) in cholestasis, consistent with defective canalicular AQP8 functional expression. By Northern blotting, we found that AQP8 mRNA expression was increased by 115% in cholestasis, suggesting a posttranscriptional mechanism of protein level reduction. Accordingly, studies in primary cultured rat hepatocytes indicated that the lysosomal protease inhibitor leupeptin prevented the estrogen-induced AQP8 downregulation. In conclusion, hepatocyte AQP8 protein expression is downregulated in estrogen-induced intrahepatic cholestasis, presumably by lysosomal-mediated degradation. Reduced canalicular membrane AQP8 expression is associated with impaired osmotic membrane water permeability. Our data support the novel notion that a defective expression of canalicular AQP8 contributes as a mechanism for bile secretory dysfunction of cholestatic hepatocytes.
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Lehmann, Guillermo L., Flavia I. Carreras, Leandro R. Soria, Sergio A. Gradilone, and Raúl A. Marinelli. "LPS induces the TNF-α-mediated downregulation of rat liver aquaporin-8: role in sepsis-associated cholestasis." American Journal of Physiology-Gastrointestinal and Liver Physiology 294, no. 2 (February 2008): G567—G575. http://dx.doi.org/10.1152/ajpgi.00232.2007.
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Although bacterial lipopolysaccharides (LPS) are known to cause cholestasis in sepsis, the molecular mechanisms accounting for this effect are only partially known. Because aquaporin-8 (AQP8) seems to facilitate the canalicular osmotic water movement during hepatocyte bile formation, we studied its gene and functional expression in LPS-induced cholestasis. By subcellular fractionation and immunoblotting analysis, we found that 34-kDa AQP8 was significantly decreased by 70% in plasma (canalicular) and intracellular (vesicular) liver membranes. However, expression and subcellular localization of hepatocyte sinusoidal AQP9 were unaffected. Immunohistochemistry for liver AQPs confirmed these observations. Osmotic water permeability ( Pf) of canalicular membranes, measured by stopped-flow spectrophotometry, was significantly reduced (65 ± 1 vs. 49 ± 1 μm/s) by LPS, consistent with defective canalicular AQP8 functional expression. By Northern blot analysis, we found that 1.5-kb AQP8 mRNA expression was increased by 80%, suggesting a posttranscriptional mechanism of protein reduction. The tumor necrosis factor-α (TNF-α) receptor fusion protein TNFp75:Fc prevented the LPS-induced impairment of AQP8 expression and bile flow, suggesting the cytokine TNF-α as a major mediator of LPS effect. Accordingly, studies in hepatocyte primary cultures indicated that recombinant TNF-α downregulated AQP8. The effect of TNF-α was prevented by the lysosomal protease inhibitors leupeptin or chloroquine or by the proteasome inhibitors MG132 or lactacystin, suggesting a cytokine-induced AQP8 proteolysis. In conclusion, our data suggest that LPS induces the TNF-α-mediated posttranscriptional downregulation of AQP8 functional expression in hepatocytes, a mechanism potentially relevant to the molecular pathogenesis of sepsis-associated cholestasis.
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Gresz, V., T. H. Kwon, P. T. Hurley, G. Varga, T. Zelles, S. Nielsen, R. M. Case, and M. C. Steward. "Identification and localization of aquaporin water channels in human salivary glands." American Journal of Physiology-Gastrointestinal and Liver Physiology 281, no. 1 (July 1, 2001): G247—G254. http://dx.doi.org/10.1152/ajpgi.2001.281.1.g247.
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Aquaporin (AQP) water channels are expressed in a variety of fluid-transporting epithelia and are likely to play a significant role in salivary secretion. Our aim was to identify and localize the aquaporins expressed in human salivary glands. Total RNA was extracted from human parotid, submandibular, sublingual, and labial glands and from human brain. Expression of aquaporin mRNA was assessed by RT-PCR using specific primers for human AQP1, AQP3, AQP4, and AQP5. All four aquaporins were detected by RT-PCR in all of the glands, and the sequences were confirmed after further amplification with nested primers. Cleaned PCR products were then used as 32P-labeled cDNA probes in a semiquantitative Northern blot analysis using glyceraldehyde-3-phosphate dehydrogenase as reference. Only AQP1, AQP3, and AQP5 mRNAs were present at significant levels. AQP localization was determined by immunohistochemistry on paraffin sections using affinity-purified primary antibodies and peroxidase-linked secondary antibodies. Each salivary gland type showed a broadly similar staining pattern: AQP1 was localized to the capillary endothelium and myoepithelial cells; AQP3 was present in the basolateral membranes of both mucous and serous acinar cells; AQP4 was not detected; and AQP5 was expressed in the luminal and canalicular membranes of both types of acinar cell. We conclude that AQP3 and AQP5 together may provide a pathway for transcellular osmotic water flow in the formation of the primary saliva.
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Escudero-Hernández, Celia, Andreas Münch, Ann-Elisabet Østvik, Atle van Beelen Granlund, and Stefan Koch. "The Water Channel Aquaporin 8 is a Critical Regulator of Intestinal Fluid Homeostasis in Collagenous Colitis." Journal of Crohn's and Colitis 14, no. 7 (February 4, 2020): 962–73. http://dx.doi.org/10.1093/ecco-jcc/jjaa020.
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Abstract Background and Aims Diarrhoea is a common, debilitating symptom of gastrointestinal disorders. Pathomechanisms probably involve defects in trans-epithelial water transport, but the role of aquaporin [AQP] family water channels in diarrhoea-predominant diseases is unknown. We investigated the involvement of AQPs in the pathobiology of collagenous colitis [CC], which features chronic, watery diarrhoea despite overtly normal intestinal epithelial cells [IECs]. Methods We assessed the expression of all AQP family members in mucosal samples of CC patients before and during treatment with the corticosteroid drug budesonide, steroid-refractory CC patients and healthy controls. Samples were analysed by genome-wide mRNA sequencing [RNA-seq] and quantitative real-time PCR [qPCR]. In some patients, we performed tissue microdissection followed by RNA-seq to explore the IEC-specific CC transcriptome. We determined changes in the protein levels of the lead candidates in IEC by confocal microscopy. Finally, we investigated the regulation of AQP expression by corticosteroids in model cell lines. Results Using qPCR and RNA-seq, we identified loss of AQP8 expression as a hallmark of active CC, which was reverted by budesonide treatment in steroid-responsive but not refractory patients. Consistently, decreased AQP8 mRNA and protein levels were observed in IECs of patients with active CC, and steroid drugs increased AQP8 expression in model IECs. Moreover, low APQ8 expression was strongly associated with higher stool frequency in CC patients. Conclusion Down-regulation of epithelial AQP8 may impair water resorption in active CC, resulting in watery diarrhoea. Our results suggest that AQP8 is a potential drug target for the treatment of diarrhoeal disorders.
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Yamamoto, T., S. Sasaki, K. Fushimi, K. Ishibashi, E. Yaoita, K. Kawasaki, H. Fujinaka, F. Marumo, and I. Kihara. "Expression of AQP family in rat kidneys during development and maturation." American Journal of Physiology-Renal Physiology 272, no. 2 (February 1, 1997): F198—F204. http://dx.doi.org/10.1152/ajprenal.1997.272.2.f198.
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The mRNA expression and localization of the aquaporin (AQP) family in rat kidney were examined by ribonuclease protection assay and immunohistochemistry. AQP1, AQP2, AQP3, and AQP4 mRNA were hardly detectable in 16-day gestation fetuses. AQP1 mRNA was explosively expressed at 1 wk, keeping the level throughout life. AQP2 mRNA expression was apparently noticed in 18-day fetuses and was enhanced gradually with age to reach a plateau at 4 wk. AQP3 and AQP4 mRNA expression was significantly found at birth but was not changed remarkably thereafter. AQP2 protein appeared first at the apical side of collecting duct cells in 18-day fetuses. The staining intensity at the site increased with age, and basolateral staining was added in adult rats. AQP3 was distinctly demonstrated at the basolateral side of collecting duct cells after birth, and the staining intensity was almost stable throughout life. The progressive induction of AQP2 expression in the first 4 wk after birth is presumed to contribute to the maturation of urinary concentrating capacity during the kidney development.
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Floyd, R. V., S. L. Mason, C. J. Proudman, A. J. German, D. Marples, and A. Mobasheri. "Expression and nephron segment-specific distribution of major renal aquaporins (AQP1–4) in Equus caballus, the domestic horse." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, no. 1 (July 2007): R492—R503. http://dx.doi.org/10.1152/ajpregu.00689.2005.
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Aquaporins (AQPs) play fundamental roles in water and osmolyte homeostasis by facilitating water and small solute movement across plasma membranes of epithelial, endothelial, and other tissues. AQP proteins are abundantly expressed in the mammalian kidney, where they have been shown to play essential roles in fluid balance and urine concentration. Thus far, the majority of studies on renal AQPs have been carried out in laboratory rodents and sheep; no data have been published on the expression of AQPs in kidneys of equines or other large mammals. The aim of this comparative study was to determine the expression and nephron segment localization of AQP1–4 in Equus caballus by immunoblotting and immunohistochemistry with custom-designed rabbit polyclonal antisera. AQP1 was found in apical and basolateral membranes of the proximal convoluted tubules and thin descending limbs of the loop of Henle. AQP2 expression was specifically detected in apical membranes of cortical, medullary, and papillary collecting ducts. AQP3 was expressed in basolateral membranes of cortical, medullary, and papillary collecting ducts. Immunohistochemistry also confirmed AQP4 expression in basolateral membranes of cells lining the distal convoluted and connecting tubules. Western blots revealed high expression of AQP1–4 in the equine kidney. These observations confirm that AQPs are expressed in the equine kidney and are found in similar nephron locations to mouse, rat, and human kidney. Equine renal AQP proteins are likely to be involved in acute and chronic regulation of body fluid composition and may be implicated in water balance disorders brought about by colic and endotoxemia.
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King, Landon S., Søren Nielsen, and Peter Agre. "Aquaporins in complex tissues. I. Developmental patterns in respiratory and glandular tissues of rat." American Journal of Physiology-Cell Physiology 273, no. 5 (November 1, 1997): C1541—C1548. http://dx.doi.org/10.1152/ajpcell.1997.273.5.c1541.
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Developmental expression of aquaporin water transport proteins is not well understood in respiratory tract or secretory glands; here we define aquaporin protein ontogeny in rat. Expression of aquaporin-3 (AQP3), AQP4, and AQP5 proteins occurs within 2 wk after birth, whereas AQP1 first appears before birth. In most tissues, aquaporin protein expression increases progressively, although transient high-level expression is noted in distal lung (AQP4 at postnatal day +2) and trachea (AQP5 at postnatal day +21 and AQP3 at postnatal day +42). In mature animals, AQP5 is abundant in distal lung and salivary glands, AQP3 and AQP4 are present in trachea, and AQP1 is present in all of these tissues except salivary glands. Surprisingly, all four aquaporin proteins are highly abundant in nasopharynx. Unlike AQP1, corticosteroids did not induce expression of AQP3, AQP4, or AQP5 in lung. Our results seemingly implicate aquaporins in proximal airway humidification, glandular secretion, and perinatal clearance of fluid from distal airways. However, the studies underscore a need for detailed immunohistochemical characterizations and definitive functional studies.
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Yang, Baoxue, Dan Zhao, Eugene Solenov, and A. S. Verkman. "Evidence from knockout mice against physiologically significant aquaporin 8-facilitated ammonia transport." American Journal of Physiology-Cell Physiology 291, no. 3 (September 2006): C417—C423. http://dx.doi.org/10.1152/ajpcell.00057.2006.
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Aquaporin (AQP)8-facilitated transport of NH3 has been suggested recently by increased NH3 permeability in Xenopus oocytes and yeast expressing human or rat AQP8. We tested the proposed roles of AQP8-facilitated NH3 transport in mammalian physiology by comparative phenotype studies in wild-type vs. AQP8-null mice. AQP8-facilitated NH3 transport was confirmed in mammalian cell cultures expressing rat or mouse AQP8, in which the fluorescence of a pH-sensing yellow fluorescent protein was measured in response to ammonia (NH3/NH4+) gradients. Relative AQP8 single-channel NH3-to-water permeability was ∼0.03. AQP8-facilitated NH3 and water permeability in a native tissue was confirmed in membrane vesicles isolated from testes of wild-type vs. AQP8-null mice, in which BCECF was used as an intravesicular pH indicator. A series of in vivo studies were done in mice, including 1) serum ammonia measurements before and after ammonia infusion, 2) renal ammonia clearance, 3) colonic ammonia absorption, and 4) liver ammonia accumulation and renal ammonia excretion after acute and chronic ammonia loading. Except for a small reduction in hepatic ammonia accumulation and increase in ammonia excretion in AQP8-null mice loaded with large amounts of ammonia, there were no significant differences in wild-type vs. AQP8-null mice. Our results support the conclusion that AQP8 can facilitate NH3 transport but provide evidence against physiologically significant AQP8-facilitated NH3 transport in mice.
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Soria, Leandro R., Sergio A. Gradilone, M. Cecilia Larocca, and Raúl A. Marinelli. "Glucagon induces the gene expression of aquaporin-8 but not that of aquaporin-9 water channels in the rat hepatocyte." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 296, no. 4 (April 2009): R1274—R1281. http://dx.doi.org/10.1152/ajpregu.90783.2008.
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Glucagon stimulates the vesicle trafficking of aquaporin-8 (AQP8) water channels to the rat hepatocyte canalicular membranes, a process thought to be relevant to glucagon-induced bile secretion. In this study, we investigated whether glucagon is able to modulate the gene expression of hepatocyte AQP8. Glucagon was administered to rats at 0.2 mg/100 g body wt ip in 2, 3, or 6 equally spaced doses for 8, 16, and 36 h, respectively. Immunoblotting analysis showed that hepatic 34-kDa AQP8 was significantly increased by 79 and 107% at 16 and 36 h, respectively. Hepatic AQP9 protein expression remained unaltered. AQP8 mRNA expression, assessed by real-time PCR, was not modified over time, suggesting a posttranscriptional mechanism of AQP8 protein increase. Glucagon effects on AQP8 were directly studied in primary cultured rat hepatocytes. Immunoblotting and confocal immunofluorescence microscopy confirmed the specific glucagon-induced AQP8 upregulation. The RNA polymerase II inhibitor actinomycin D was unable to prevent glucagon effect, providing additional support to the nontranscriptional upregulation of AQP8. Cycloheximide also showed no effect, suggesting that glucagon-induced AQP8 expression does not depend on protein synthesis but rather on protein degradation. Inhibitory experiments suggest that a reduced calpain-mediated AQP8 proteolysis could be involved. The action of glucagon on hepatocyte AQP8 was mimicked by dibutyryl cAMP and suppressed by PKA or phosphatidylinositol-3-kinase (PI3K) inhibitors. In conclusion, our data suggest that glucagon induces the gene expression of rat hepatocyte AQP8 by reducing its degradation, a process that involves cAMP-PKA and PI3K signal pathways.
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Tanski, Damian, Agnieszka Skowronska, Malgorzata Tanska, Ewa Lepiarczyk, and Mariusz T. Skowronski. "The In Vitro Effect of Steroid Hormones, Arachidonic Acid, and Kinases Inhibitors on Aquaporin 1, 2, 5, and 7 Gene Expression in the Porcine Uterine Luminal Epithelial Cells during the Estrous Cycle." Cells 10, no. 4 (April 7, 2021): 832. http://dx.doi.org/10.3390/cells10040832.
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Aquaporins (AQPs) are integral membrane proteins, which play an important role in water homeostasis in the uterus. According to the literature, the expression of aquaporins in reproductive structures depends on the local hormonal milieu. The current study investigated the effect of selected PKA kinase inhibitor H89 and MAPK kinase inhibitor PD98059, on the expression of AQP1, 2, 5, and 7, and steroid hormones (E2), progesterone (P4), and arachidonic acid (AA) in the porcine endometrium on days 18–20 and 2–4 of the estrous cycle (the follicular phase where estrogen and follicle-stimulating hormone (FSH) are secreted increasingly in preparation for estrus and the luteal phase where the ovarian follicles begin the process of luteinization with the formation of the corpus luteum and progesterone secretion, respectively). The luminal epithelial cells were incubated in vitro in the presence of the aforementioned factors. The expression of mRNA was determined by the quantitative real-time PCR technique. In general, in Experiment 1, steroid hormones significantly increased expression of AQP1, 2, and 5 while arachidonic acid increased expression of AQP2 and AQP7. On the other hand, MAPK kinase inhibitor significantly decreased the expression of AQP1 and 5. In Experiment 2, E2, P4, or AA combined with kinase inhibitors differentially affected on AQPs expression. E2 in combination with PKA inhibitor significantly decreased expression of AQP1 but E2 or P4 combined with this inhibitor increased the expression of AQP5 and 7. On the contrary, E2 with PD98059 significantly increased AQP5 and AQP7 expression. Progesterone in combination with MAPK kinase inhibitor significantly downregulated the expression of AQP5 and upregulated AQP7. Arachidonic acid mixed with H89 or PD98059 caused a decrease in the expression of AQP5 and an increase of AQP7. The obtained results indicate that estradiol, progesterone, and arachidonic acid through PKA and MAPK signaling pathways regulate the expression of AQP1 and AQP5 in the porcine luminal epithelial cells in the periovulatory period.
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Calamita, Giuseppe, Maria Moreno, Domenico Ferri, Elena Silvestri, Patrizia Roberti, Luigi Schiavo, Patrizia Gena, Maria Svelto, and Fernando Goglia. "Triiodothyronine modulates the expression of aquaporin-8 in rat liver mitochondria." Journal of Endocrinology 192, no. 1 (January 2007): 111–20. http://dx.doi.org/10.1677/joe-06-0058.
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The recent identification of aquaporin-8 (AQP8), an aquaporin (AQP) channel permeable to water and ammonia, in the inner membrane (IMM) of rat liver mitochondria suggested a role for such AQP in the hydration state and the metabolic function of mitochondria. Since thyroid hormone triiodothyronine (T3) is known to modulate both the shape and the metabolic activities of liver mitochondria, it was interesting to investigate the expression and distribution of AQP8 as well as the osmotic water permeability of the IMM in liver mitochondria from rats in different thyroid states. By semi-quantitative reverse transcriptase (RT)-PCR, when compared with the euthyroid counterpart, the levels of hepatic AQP8 mRNA significantly increased in the hypothyroid state, whereas they were strongly decreased after administration of T3. A similar pattern was seen at the protein level by immunoblotting mitochondrial membranes. The upregulation of mitochondrial AQP8 in the hypothyroid liver was confirmed by immunogold electron microscopy. Stopped-flow light scattering with IMM vesicles showed no significant differences in terms of osmotic water permeability among the IMMs in the various thyroid states. Overall, our data indicate that the T3 modulation of the AQP8 gene is a rapid downregulation of transcription. Modulation of hepatic AQP8 expression may be relevant to the regulation of mitochondrial metabolism by thyroid hormones.
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VERKMAN, A. S. "Lessons on Renal Physiology from Transgenic Mice Lacking Aquaporin Water Channels." Journal of the American Society of Nephrology 10, no. 5 (May 1999): 1126–35. http://dx.doi.org/10.1681/asn.v1051126.
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Abstract. Several aquaporin-type water channels are expressed in kidney: AQP1 in the proximal tubule, thin descending limb of Henle, and vasa recta; AQP2, AQP3, and AQP4 in the collecting duct; AQP6 in the papilla; and AQP7 in the proximal tubule. AQP2 is the vasopressin-regulated water channel that is important in hereditary and acquired diseases affecting urine-concentrating ability. It has been difficult to establish the roles of the other aquaporins in renal physiology because suitable aquaporin inhibitors are not available. One approach to the problem has been to generate and analyze transgenic knockout mice in which individual aquaporins have been selectively deleted by targeted gene disruption. Phenotype analysis of kidney and extrarenal function in knockout mice has been very informative in defining the role of aquaporins in organ physiology and addressing basic questions regarding the route of transepithelial water transport and the mechanism of near isoosmolar fluid reabsorption. This article describes new renal physiologic insights revealed by phenotype analysis of aquaporin-knockout mice and the prospects for further basic and clinical developments.
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Wojtanowicz-Markiewicz, Katarzyna, Magdalena Kulus, Sandra Knap, Ievgenia Kocherova, Maurycy Jankowski, Katarzyna Stefańska, Michal Jeseta, et al. "Expression of Selected Connexin and Aquaporin Genes and Real-Time Proliferation of Porcine Endometrial Luminal Epithelial Cells in Primary Culture Model." BioMed Research International 2020 (February 3, 2020): 1–15. http://dx.doi.org/10.1155/2020/7120375.
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Luminal epithelial cells are the first embryonic-maternal contact site undergoing very specific changes associated with reproductive processes. Cells prepare for embryo development by increasing their volume, with the help of aquaporins that provide a transcellular path of rapid water movement during the secretion and absorption of fluids, as well as connexins enabling the flow of inorganic ions and small molecules. In this work, we have examined how AQPs and Cx’s behave in luminal epithelium primary cell culture. Cells obtained from porcine specimen during slaughter were primarily in vitro cultured for 7 days. Their proliferation patterns were then analyzed using RTCA, with the expression of genes of interest evaluated with the use of immunofluorescence and RT-qPCR. The results of these changes of gene of interest expression were analyzed on each of the seven days of the porcine luminal primary cell culture. Our study showed that the significant changes were noted in the case of Cx43, whose level of protein expression and distribution increases after 120 hours of culture, when the cells enter the lag phase, and maintains an upward trend until the end of the culture. We noted an increase in AQP4, AQP7, AQP8, and AQP11 levels throughout the entire culture period, while the largest differences in expression were found in AQP3, AQP4, and AQP10. The obtained results could become a point of reference for further in vivo and clinical research. Experiments conducted with these proteins showed that they influence the endometrial fluid content during the oestrous cycle and participate in the process of angiogenesis, which intensifies during endometrial development.
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Rai, Tatemitsu, Sei Sasaki, and Shinichi Uchida. "Polarized trafficking of the aquaporin-3 water channel is mediated by an NH2-terminal sorting signal." American Journal of Physiology-Cell Physiology 290, no. 1 (January 2006): C298—C304. http://dx.doi.org/10.1152/ajpcell.00356.2005.
Full textAbstract:
Epithelial renal collecting duct cells express multiple types of aquaporin (AQP) water channels in a polarized fashion. AQP2 is specifically targeted to the apical cell domain, whereas AQP3 and AQP4 are expressed on the basolateral membrane. It is crucial that these AQP variants are sorted to their proper polarized membrane domains, because correct AQP sorting enables efficient water transport. However, the molecular mechanisms involved in the polarized targeting and membrane trafficking of AQPs remain largely unknown. In the present study, we have examined the polarized trafficking and surface expression of AQP3 in Madin-Darby canine kidney type II (MDCKII) cells in an effort to identify the molecular determinants of polarized targeting specificity. When expressed in MDCKII cells, the majority of the exogenous wild-type AQP3 was found to be targeted to the basolateral membrane, consistent with its localization pattern in vivo. A potential sorting signal consisting of tyrosine- and dileucine-based motifs was subsequently identified in the AQP3 NH2 terminus. When mutations were introduced into this signaling region, the basolateral targeting of the resulting mutant AQP3 was disrupted and the mutant protein remained in the cytoplasm. AQP2-AQP3 chimeras were then generated in which the entire NH2 terminus of AQP2 was replaced with the AQP3 NH2 terminus. This chimeric protein was observed to be mislocalized constitutively in the basolateral membrane, and mutations in the AQP3 NH2-terminal sorting signal abolished this effect. On the basis of these results, we conclude that an NH2-terminal sorting signal mediates the basolateral targeting of AQP3.