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Aquaporins: Water Channels Essential for Living Organisms

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Biochemistry".

Deadline for manuscript submissions: closed (30 November 2017) | Viewed by 160855

Special Issue Editor

Laboratory of Pathophysiological and Nutritional Biochemistry, Faculty of Medicine, Université Libre de Bruxelles, 808 Route de Lennik, Blg G/E CP 611, Brussels B-1070, Belgium
Interests: aquaporins; exocrine glands; diseases; cell signaling; metabolism
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Special Issue Information

Dear Colleagues,

Water is essential for life. The discovery of water channels, also called aquaporins, provided the molecular explanation for the existence of facilitated passive transmembrane water transport. Aquaporins are characterized by a highly conserved structure, especially in the vicinity of the water pore. Aquaporins are present in all living organisms, including vertebrates, invertebrates, microorganisms and plants, and are involved in many living processes, and in diseases. This Special Issue of the International Journal of Molecular Sciences, “Aquaporins: Water Channels Essential For Living Organisms” will focus on the function of aquaporins across all living organisms, including their potential utility in medicine. Authors are invited to submit their contributions that will meet the focus of this Special Issue.

Prof. Dr. Christine Delporte
Guest Editor

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Keywords

  • water channel
  • aquaporin
  • transmembrane permeability
  • disease
  • therapeutic application
  • vertebrates
  • invertebrates
  • microorganisms
  • plants
  • structure
  • function
  • regulation

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Published Papers (23 papers)

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17 pages, 4220 KiB  
Article
Structural Basis for Mutations of Human Aquaporins Associated to Genetic Diseases
by Luisa Calvanese, Gabriella D’Auria, Anna Vangone, Lucia Falcigno and Romina Oliva
Int. J. Mol. Sci. 2018, 19(6), 1577; https://doi.org/10.3390/ijms19061577 - 25 May 2018
Cited by 18 | Viewed by 4387
Abstract
Aquaporins (AQPs) are among the best structural-characterized membrane proteins, fulfilling the role of allowing water flux across cellular membranes. Thus far, 34 single amino acid polymorphisms have been reported in HUMSAVAR for human aquaporins as disease-related. They affect AQP2, AQP5 and AQP8, where [...] Read more.
Aquaporins (AQPs) are among the best structural-characterized membrane proteins, fulfilling the role of allowing water flux across cellular membranes. Thus far, 34 single amino acid polymorphisms have been reported in HUMSAVAR for human aquaporins as disease-related. They affect AQP2, AQP5 and AQP8, where they are associated with nephrogenic diabetes insipidus, keratoderma and colorectal cancer, respectively. For half of these mutations, although they are mostly experimentally characterized in their dysfunctional phenotypes, a structural characterization at a molecular level is still missing. In this work, we focus on such mutations and discuss what the structural defects are that they appear to cause. To achieve this aim, we built a 3D molecular model for each mutant and explored the effect of the mutation on all of their structural features. Based on these analyses, we could collect the structural defects of all the pathogenic mutations (here or previously analysed) under few main categories, that we found to nicely correlate with the experimental phenotypes reported for several of the analysed mutants. Some of the structural analyses we present here provide a rationale for previously experimentally observed phenotypes. Furthermore, our comprehensive overview can be used as a reference frame for the interpretation, on a structural basis, of defective phenotypes of other aquaporin pathogenic mutants. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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9 pages, 3159 KiB  
Communication
Immunohistochemical Expression of Aquaporin-1 in Fluoro-Edenite-Induced Malignant Mesothelioma: A Preliminary Report
by Giuseppe Angelico, Rosario Caltabiano, Carla Loreto, Antonio Ieni, Giovanni Tuccari, Caterina Ledda and Venerando Rapisarda
Int. J. Mol. Sci. 2018, 19(3), 685; https://doi.org/10.3390/ijms19030685 - 28 Feb 2018
Cited by 18 | Viewed by 3364
Abstract
Background: The immunohistochemical expression of aquaporin-1 (AQP1) in asbestos-related malignant pleural mesothelioma (MPM) is emerging as a useful prognostic indicator of improved survival. A significantly increased incidence of MPM in a small town in southern Italy was ascribed to exposure to fluoro-edenite (FE), [...] Read more.
Background: The immunohistochemical expression of aquaporin-1 (AQP1) in asbestos-related malignant pleural mesothelioma (MPM) is emerging as a useful prognostic indicator of improved survival. A significantly increased incidence of MPM in a small town in southern Italy was ascribed to exposure to fluoro-edenite (FE), a naturally occurring asbestos fiber. We investigated the immunohistochemical expression of AQP1 in patients affected by FE-related MPM; taking into consideration its suggested independent prognostic role, its possible correlation with clinicopathological parameters and patient outcome was also evaluated. Methods: Ten patients were selected for this study, as neoplastic tissue blocks, clinical and follow-up data were available. The immunohistochemical overexpression of AQP1 was defined as ≥50% of tumor cells showing membranous staining. Results: Six cases showed AQP1 expression in ≥50% of tumor cells; in this group, a significant association of AQP1 overexpression with an increased median overall survival (OS) of 26.3 months was observed. By contrast, four patients exhibited an AQP1 score of <50% of stained cells, with a shorter median OS of 8.9 months. Conclusions: The present study represents further confirmation of the hypothesized prognostic role of AQP1, which seems a reliable prognostic indicator. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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10 pages, 17329 KiB  
Article
The Aquaporin 1 Inhibitor Bacopaside II Reduces Endothelial Cell Migration and Tubulogenesis and Induces Apoptosis
by Helen M. Palethorpe, Yoko Tomita, Eric Smith, Jinxin V. Pei, Amanda R. Townsend, Timothy J. Price, Joanne P. Young, Andrea J. Yool and Jennifer E. Hardingham
Int. J. Mol. Sci. 2018, 19(3), 653; https://doi.org/10.3390/ijms19030653 - 26 Feb 2018
Cited by 25 | Viewed by 5576
Abstract
Expression of aquaporin-1 (AQP1) in endothelial cells is critical for their migration and angiogenesis in cancer. We tested the AQP1 inhibitor, bacopaside II, derived from medicinal plant Bacopa monnieri, on endothelial cell migration and tube-formation in vitro using mouse endothelial cell lines [...] Read more.
Expression of aquaporin-1 (AQP1) in endothelial cells is critical for their migration and angiogenesis in cancer. We tested the AQP1 inhibitor, bacopaside II, derived from medicinal plant Bacopa monnieri, on endothelial cell migration and tube-formation in vitro using mouse endothelial cell lines (2H11 and 3B11) and human umbilical vein endothelial cells (HUVEC). The effect of bacopaside II on viability, apoptosis, migration and tubulogenesis was assessed by a proliferation assay, annexin-V/propidium iodide flow cytometry, the scratch wound assay and endothelial tube-formation, respectively. Cell viability was reduced significantly for 2H11 at 15 μM (p = 0.037), 3B11 at 12.5 μM (p = 0.017) and HUVEC at 10 μM (p < 0.0001). At 15 μM, the reduced viability was accompanied by an increase in apoptosis of 38%, 50% and 32% for 2H11, 3B11 and HUVEC, respectively. Bacopaside II at ≥10 μM significantly reduced migration of 2H11 (p = 0.0002) and 3B11 (p = 0.034). HUVECs were most sensitive with a significant reduction at ≥7.5 μM (p = 0.037). Tube-formation was reduced with a 15 μM dose for all cell lines and 10 μM for 3B11 (p < 0.0001). These results suggest that bacopaside II is a potential anti-angiogenic agent. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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12 pages, 3613 KiB  
Article
Changes in the Expression of AQP4 and AQP9 in the Hippocampus Following Eclampsia-Like Seizure
by Xinjia Han, Qian Huang, Lei Liu, Xiaoyan Sha, Bihui Hu and Huishu Liu
Int. J. Mol. Sci. 2018, 19(1), 300; https://doi.org/10.3390/ijms19010300 - 19 Jan 2018
Cited by 13 | Viewed by 4559
Abstract
Eclampsia is a hypertensive disorder of pregnancy that is defined by the new onset of grand mal seizures on the basis of pre-eclampsia. Until now, the mechanisms underlying eclampsia were poorly understood. Brain edema is considered a leading cause of eclamptic seizures; aquaporins [...] Read more.
Eclampsia is a hypertensive disorder of pregnancy that is defined by the new onset of grand mal seizures on the basis of pre-eclampsia. Until now, the mechanisms underlying eclampsia were poorly understood. Brain edema is considered a leading cause of eclamptic seizures; aquaporins (AQP4 and AQP9), the glial water channel proteins mainly expressed in the nervous system, play an important role in brain edema. We studied AQP4 and AQP9 expression in the hippocampus of pre-eclamptic and eclamptic rats in order to explore the molecular mechanisms involved in brain edema. Using our previous animal models, we found several neuronal deaths in the hippocampal CA1 and CA3 regions after pre-eclampsia and that eclampsia induced more neuronal deaths in both areas by Nissl staining. In the current study, RT-PCR and Western blotting data showed significant upregulation of AQP4 and AQP9 mRNA and protein levels after eclamptic seizures in comparison to pre-eclampsia and at the same time AQP4 and AQP9 immunoreactivity also increased after eclampsia. These findings showed that eclamptic seizures induced cell death and that upregulation of AQP4 and AQP9 may play an important role in this pathophysiological process. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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13 pages, 6459 KiB  
Article
Aquaporin Expression and Water Transport Pathways inside Leaves Are Affected by Nitrogen Supply through Transpiration in Rice Plants
by Lei Ding, Yingrui Li, Limin Gao, Zhifeng Lu, Min Wang, Ning Ling, Qirong Shen and Shiwei Guo
Int. J. Mol. Sci. 2018, 19(1), 256; https://doi.org/10.3390/ijms19010256 - 16 Jan 2018
Cited by 15 | Viewed by 4601
Abstract
The photosynthetic rate increases under high-N supply, resulting in a large CO2 transport conductance in mesophyll cells. It is less known that water movement is affected by nitrogen supply in leaves. This study investigated whether the expression of aquaporin and water transport [...] Read more.
The photosynthetic rate increases under high-N supply, resulting in a large CO2 transport conductance in mesophyll cells. It is less known that water movement is affected by nitrogen supply in leaves. This study investigated whether the expression of aquaporin and water transport were affected by low-N (0.7 mM) and high-N (7 mM) concentrations in the hydroponic culture of four rice varieties: (1) Shanyou 63 (SY63), a hybrid variant of the indica species; (2) Yangdao 6 (YD6), a variant of indica species; (3) Zhendao 11 (ZD11), a hybrid variant of japonica species; and (4) Jiuyou 418 (JY418), another hybrid of the japonica species. Both the photosynthetic and transpiration rate were increased by the high-N supply in the four varieties. The expressions of aquaporins, plasma membrane intrinsic proteins (PIPs), and tonoplast membrane intrinsic protein (TIP) were higher in high-N than low-N leaves, except in SY63. Leaf hydraulic conductance (Kleaf) was lower in high-N than low-N leaves in SY63, while Kleaf increased under high-N supply in the YD6 variant. Negative correlations were observed between the expression of aquaporin and the transpiration rate in different varieties. Moreover, there was a significant negative correlation between transpiration rate and intercellular air space. In conclusion, the change in expression of aquaporins could affect Kleaf and transpiration. A feedback effect of transpiration would regulate aquaporin expression. The present results imply a coordination of gas exchange with leaf hydraulic conductance. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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16 pages, 3424 KiB  
Article
CPT-11-Induced Delayed Diarrhea Develops via Reduced Aquaporin-3 Expression in the Colon
by Risako Kon, Yuika Tsubota, Moe Minami, Saki Kato, Yukari Matsunaga, Hiroshi Kimura, Yuta Murakami, Tetsuya Fujikawa, Ryoya Sakurai, Rei Tomimoto, Yoshiaki Machida, Nobutomo Ikarashi and Kiyoshi Sugiyama
Int. J. Mol. Sci. 2018, 19(1), 170; https://doi.org/10.3390/ijms19010170 - 06 Jan 2018
Cited by 28 | Viewed by 6199
Abstract
While irinotecan (CPT-11) has a potent anti-cancer effect, it also causes serious diarrhea as an adverse reaction. In this study, we analyzed the pathogenic mechanism of CPT-11-induced delayed diarrhea by focusing on water channel aquaporin-3 (AQP3) in the colon. When rats received CPT-11, [...] Read more.
While irinotecan (CPT-11) has a potent anti-cancer effect, it also causes serious diarrhea as an adverse reaction. In this study, we analyzed the pathogenic mechanism of CPT-11-induced delayed diarrhea by focusing on water channel aquaporin-3 (AQP3) in the colon. When rats received CPT-11, the expression level of AQP3 was reduced during severe diarrhea. It was found that the expression levels of inflammatory cytokines and the loss of crypt cells were increased in the colon when CPT-11 was administered. When celecoxib, an anti-inflammatory drug, was concomitantly administered, both the diarrhea and the reduced expression of AQP3 induced by CPT-11 were suppressed. The inflammation in the rat colon during diarrhea was caused via activated macrophage by CPT-11. These results showed that when CPT-11 is administered, the expression level of AQP3 in the colon is reduced, resulting in delayed diarrhea by preventing water transport from the intestinal tract. It was also suggested that the reduced expression of AQP3 might be due to the inflammation that occurs following the loss of colonic crypt cells and to the damage caused by the direct activation of macrophages by CPT-11. Therefore, it was considered that anti-inflammatory drugs that suppress the reduction of AQP3 expression could prevent CPT-11-induced delayed diarrhea. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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13 pages, 1302 KiB  
Article
Endothelial Aquaporins and Hypomethylation: Potential Implications for Atherosclerosis and Cardiovascular Disease
by Inês Vieira Da Silva, Madalena Barroso, Teresa Moura, Rita Castro and Graça Soveral
Int. J. Mol. Sci. 2018, 19(1), 130; https://doi.org/10.3390/ijms19010130 - 03 Jan 2018
Cited by 24 | Viewed by 4331
Abstract
Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol permeation through cell membranes. Recently, the water channel AQP1 was suggested to contribute to endothelial homeostasis and cardiovascular health. Less is known about endothelial aquaglyceroporins expression and its implication in cardiovascular disease (CVD). [...] Read more.
Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol permeation through cell membranes. Recently, the water channel AQP1 was suggested to contribute to endothelial homeostasis and cardiovascular health. Less is known about endothelial aquaglyceroporins expression and its implication in cardiovascular disease (CVD). We have previously used cultured human endothelial cells under a hypomethylating environment to study endothelial dysfunction and activation, a phenotype implicated in the establishment of atherosclerosis and CVD. Here, we used the same cell model to investigate aquaporin’s expression and function in healthy or pro-atherogenic phenotype. We first confirmed key features of endothelium dysfunction and activation in our cell model, including an augmented endothelial transmigration under hypomethylation. Subsequently, we found AQP1 and AQP3 to be the most predominant AQPs accounting for water and glycerol fluxes, respectively, in the healthy endothelium. Moreover, endothelial hypomethylation led to decreased levels of AQP1 and impaired water permeability without affecting AQP3 and glycerol permeability. Furthermore, TNF-α treatment-induced AQP1 downregulation suggesting that the inflammatory NF-κB signaling pathway mediates AQP1 transcriptional repression in a pro-atherogenic endothelium, a possibility that warrants further investigation. In conclusion, our results add further support to AQP1 as a candidate player in the setting of endothelial dysfunction and CVD. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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3451 KiB  
Article
Pituitary Gonadotropins, Prolactin and Growth Hormone Differentially Regulate AQP1 Expression in the Porcine Ovarian Follicular Cells
by Mariusz T. Skowronski, Patrycja Mlotkowska, Damian Tanski, Ewa Lepiarczyk, Michal K. Oklinski, Soren Nielsen and Agnieszka Skowronska
Int. J. Mol. Sci. 2018, 19(1), 5; https://doi.org/10.3390/ijms19010005 - 21 Dec 2017
Cited by 14 | Viewed by 4846
Abstract
The present in vitro study analyzed whether the hormones that affect the ovarian follicular steroidogenesis process also participate in the regulation of AQP1 mRNA and protein expression. Granulosa (Gc) and theca cells (Tc) of medium and large porcine ovarian follicles were exposed to [...] Read more.
The present in vitro study analyzed whether the hormones that affect the ovarian follicular steroidogenesis process also participate in the regulation of AQP1 mRNA and protein expression. Granulosa (Gc) and theca cells (Tc) of medium and large porcine ovarian follicles were exposed to follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL) and growth hormone (GH) for 24 h in separated cells and co-cultures of these cells. Real-time PCR, Western blotting, immunofluorescence and volumetric analysis were then performed. Gonadotropins, PRL and GH had a stimulatory impact on AQP1 mRNA and protein expression in Gc and Tc of medium and large ovarian cells. Moreover, swelling assays, in response to a hypotonic environment, demonstrated the functional presence of AQPs in porcine Gc and Tc. Immunofluorescence analysis showed that AQP1 protein was mainly localized in the perinuclear region of the cytoplasm, endosomes and cell membranes of Gc and Tc from medium and large follicles. It seems possible that AQP1 present in Gc and Tc cells may be implicated not only in the regulation of water homeostasis required for follicle development but also in cell proliferation and migration. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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4935 KiB  
Article
Regulation of Aquaporin Functional Properties Mediated by the Antioxidant Effects of Natural Compounds
by Giorgia Pellavio, Marta Rui, Laura Caliogna, Emanuela Martino, Giulia Gastaldi, Simona Collina and Umberto Laforenza
Int. J. Mol. Sci. 2017, 18(12), 2665; https://doi.org/10.3390/ijms18122665 - 08 Dec 2017
Cited by 36 | Viewed by 4684
Abstract
Some aquaporins (AQPs) have been recently demonstrated to facilitate the diffusion of hydrogen peroxide (H2O2) from the producing cells to the extracellular fluid, and their reactive oxygen species scavenging properties have been defined. Nevertheless, the identification of different AQPs [...] Read more.
Some aquaporins (AQPs) have been recently demonstrated to facilitate the diffusion of hydrogen peroxide (H2O2) from the producing cells to the extracellular fluid, and their reactive oxygen species scavenging properties have been defined. Nevertheless, the identification of different AQPs acting as peroxiporins, their functional role in eustress and distress, and the identification of antioxidant compounds able to regulate AQP gating, remain unsolved. This study aims to investigate, in HeLa cells: (1) the expression of different AQPs; (2) the evaluation of naringenin, quercetin, (R)-aloesaponol III 8-methyl ether, marrubiin, and curcumin antioxidant profiles, via α,α-diphenyl-β-picrylhydrazyl assay; (3) the effect of the compounds on the water permeability in the presence and in the absence of oxidative stress; and (4) the effect of pre- and post-treatment with the compounds on the H2O2 content in heat-stressed cells. Results showed that HeLa cells expressed AQP1, 3, 8, and 11 proteins. The oxidative stress reduced the water transport, and both pre- and post-treatment with the natural compounds recovering the water permeability, with the exception of curcumin. Moreover, the pre- and post-treatment with all the compounds reduced the H2O2 content of heat-stressed cells. This study confirms that oxidative stress reduced water AQP-mediated permeability, reversed by some chemical antioxidant compounds. Moreover, curcumin was shown to regulate AQP gating. This suggests a novel mechanism to regulate cell signaling and survival during stress, and to manipulate key signaling pathways in cancer and degenerative diseases. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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2373 KiB  
Article
Lipopolysaccharide Modifies Glycerol Permeability and Metabolism in 3T3-L1 Adipocytes
by Jeanne Durendale Chiadak, Patrizia Gena, Françoise Gregoire, Nargis Bolaky, Valérie Delforge, Jason Perret, Giuseppe Calamita and Christine Delporte
Int. J. Mol. Sci. 2017, 18(12), 2566; https://doi.org/10.3390/ijms18122566 - 29 Nov 2017
Cited by 13 | Viewed by 5447
Abstract
Aquaglyceroporins—aquaporin membrane channels (AQP) that conduct glycerol and other small neutral solutes in addition to water—play major roles in obesity. In adipocytes, aquaglyceroporins mediate glycerol uptake and release across the plasma membrane, which are two key steps for triacylglycerols (TAGs) synthesis (lipogenesis) and [...] Read more.
Aquaglyceroporins—aquaporin membrane channels (AQP) that conduct glycerol and other small neutral solutes in addition to water—play major roles in obesity. In adipocytes, aquaglyceroporins mediate glycerol uptake and release across the plasma membrane, which are two key steps for triacylglycerols (TAGs) synthesis (lipogenesis) and hydrolysis (lipolysis). The aim of this study was to assess both glycerol permeability and metabolism in undifferentiated 3T3-L1 cells (UDCs) as well as in untreated (CTL-DCs) versus lipopolysaccharide (LPS-DCs)-treated differentiated 3T3-L1 adipocytes. Glycerol release, TAGs content and whole membrane glycerol permeability were significantly increased in DCs as compared to UDCs. Moreover, in DCs, LPS treatment significantly increased TAGs content and decreased glycerol permeability. In addition, a significant reduction in whole membrane glycerol permeability was observed in LPS-DCs as compared to CTL-DCs. The relative contributions of AQP3, AQP7 and AQP9 (facilitated diffusion), as well as that of the phospholipid bilayer (simple diffusion), to the whole membrane glycerol permeability, were estimated biophysically in UDCs, CTL-DCs and LPS-DCs, using selective AQP inhibitors. Further studies will be required to determine if modifications in either subcellular localization and/or activity of aquaglyceroporins could account for the data herein. Nevertheless, our findings provide novel insights in understanding the LPS-induced adipocyte hypertrophy that accompanies obesity. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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5266 KiB  
Article
Divalent Cations Regulate the Ion Conductance Properties of Diverse Classes of Aquaporins
by Mohamad Kourghi, Saeed Nourmohammadi, Jinxin V. Pei, Jiaen Qiu, Samantha McGaughey, Stephen D. Tyerman, Caitlin S. Byrt and Andrea J. Yool
Int. J. Mol. Sci. 2017, 18(11), 2323; https://doi.org/10.3390/ijms18112323 - 03 Nov 2017
Cited by 54 | Viewed by 5471
Abstract
Aquaporins (AQPs) are known to facilitate water and solute fluxes across barrier membranes. An increasing number of AQPs are being found to serve as ion channels. Ion and water permeability of selected plant and animal AQPs (plant Arabidopsis thaliana AtPIP2;1, AtPIP2;2, AtPIP2;7, human [...] Read more.
Aquaporins (AQPs) are known to facilitate water and solute fluxes across barrier membranes. An increasing number of AQPs are being found to serve as ion channels. Ion and water permeability of selected plant and animal AQPs (plant Arabidopsis thaliana AtPIP2;1, AtPIP2;2, AtPIP2;7, human Homo sapiens HsAQP1, rat Rattus norvegicus RnAQP4, RnAQP5, and fly Drosophila melanogaster DmBIB) were expressed in Xenopus oocytes and examined in chelator-buffered salines to evaluate the effects of divalent cations (Ca2+, Mg2+, Ba2+ and Cd2+) on ionic conductances. AtPIP2;1, AtPIP2;2, HsAQP1 and DmBIB expressing oocytes had ionic conductances, and showed differential sensitivity to block by external Ca2+. The order of potency of inhibition by Ca2+ was AtPIP2;2 > AtPIP2;1 > DmBIB > HsAQP1. Blockage of the AQP cation channels by Ba2+ and Cd2+ caused voltage-sensitive outward rectification. The channels with the highest sensitivity to Ca2+ (AtPIP2;1 and AtPIP2;2) showed a distinctive relief of the Ca2+ block by co-application of excess Ba2+, suggesting that divalent ions act at the same site. Recognizing the regulatory role of divalent cations may enable the discovery of other classes of AQP ion channels, and facilitate the development of tools for modulating AQP ion channels. Modulators of AQPs have potential value for diverse applications including improving salinity tolerance in plants, controlling vector-borne diseases, and intervening in serious clinical conditions involving AQPs, such as cancer metastasis, cardiovascular or renal dysfunction. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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3319 KiB  
Article
The Effect of Aquaporin 1-Inhibition on Vasculogenic Mimicry in Malignant Mesothelioma
by Emily Pulford, James McEvoy, Ashleigh Hocking, Sarita Prabhakaran, Kim Griggs and Sonja Klebe
Int. J. Mol. Sci. 2017, 18(11), 2293; https://doi.org/10.3390/ijms18112293 - 01 Nov 2017
Cited by 9 | Viewed by 4625
Abstract
Malignant mesothelioma (MM) is an aggressive malignancy of the serosal membranes, with poor overall survival and quality of life. Limited targeted treatment strategies exist due to restricted knowledge of pathogenic pathways. Vasculogenic mimicry (VM) is a newly described phenomenon associated with increased aggressiveness [...] Read more.
Malignant mesothelioma (MM) is an aggressive malignancy of the serosal membranes, with poor overall survival and quality of life. Limited targeted treatment strategies exist due to restricted knowledge of pathogenic pathways. Vasculogenic mimicry (VM) is a newly described phenomenon associated with increased aggressiveness in other malignancies, and has been characterized in MM. Normal mesothelium expresses aquaporin 1 (AQP1) and retained expression has been associated with improved survival in MM. AQP1 is expressed by normal vascular endothelium and is involved in mediating MM cell motility and proliferation. We investigated the role of AQP1 in VM, and its interaction with the pro-angiogenic factor vascular endothelial growth factor A (VEGFA), which is variably expressed in MM. Matrigel VM assays were performed using NCI-H226 and NCI-H28 MM cell lines and primary cells in hypoxia and normoxia. The synthetic blocker AqB050 and siRNA were used to inhibit AQP1, and bevacizumab was used to inhibit VEGF. Inhibition of AQP1 resulted in increased VEGFA secretion by MM cells and reduced VM in MM cell lines in hypoxia but not normoxia. No change in VM was seen in MM primary cells. Combined inhibition of AQP1 and VEGF had no effect on VM in normoxia. In a heterotopic xenograft mouse model, AqB050 treatment did not alter vessel formation. AQP1 may interact with VEGFA and play a role in VM, especially under hypoxic conditions, but the heterogeneity of MM cells may result in different dominant pathways between patients. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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1420 KiB  
Article
Relationship between Aging-Related Skin Dryness and Aquaporins
by Nobutomo Ikarashi, Risako Kon, Miho Kaneko, Nanaho Mizukami, Yoshiki Kusunoki and Kiyoshi Sugiyama
Int. J. Mol. Sci. 2017, 18(7), 1559; https://doi.org/10.3390/ijms18071559 - 18 Jul 2017
Cited by 39 | Viewed by 7104
Abstract
Skin function deteriorates with aging, and the dermal water content decreases. In this study, we have analyzed the mechanism of aging-related skin dryness focusing on aquaporins (AQPs), which are the water channels. Mice aged 3 and 20 months were designated as young and [...] Read more.
Skin function deteriorates with aging, and the dermal water content decreases. In this study, we have analyzed the mechanism of aging-related skin dryness focusing on aquaporins (AQPs), which are the water channels. Mice aged 3 and 20 months were designated as young and aged mice, respectively, to be used in the experiments. No differences were observed in transepidermal water loss between the young mice and aged mice. However, the dermal water content in aged mice was significantly lower than that in young mice, thus showing skin dryness. The expression of AQP1, AQP3, AQP4, AQP7, and AQP9 was observed in the skin. All the mRNA expression levels of these AQPs were significantly lower in aged mice. For AQP3, which was expressed dominantly in the skin, the protein level was lower in aged mice than in young mice. The results of the study showed that the expression level of AQPs in the skin decreased with aging, suggesting the possibility that this was one of the causes of skin dryness. New targets for the prevention and treatment of aging-related skin dryness are expected to be proposed when the substance that increases the expression of AQP3 is found. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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Review

Jump to: Research

27 pages, 370 KiB  
Review
Plant and Mammal Aquaporins: Same but Different
by Timothée Laloux, Bruna Junqueira, Laurie C. Maistriaux, Jahed Ahmed, Agnieszka Jurkiewicz and François Chaumont
Int. J. Mol. Sci. 2018, 19(2), 521; https://doi.org/10.3390/ijms19020521 - 08 Feb 2018
Cited by 54 | Viewed by 5458
Abstract
Aquaporins (AQPs) constitute an ancient and diverse protein family present in all living organisms, indicating a common ancient ancestor. However, during evolution, these organisms appear and evolve differently, leading to different cell organizations and physiological processes. Amongst the eukaryotes, an important distinction between [...] Read more.
Aquaporins (AQPs) constitute an ancient and diverse protein family present in all living organisms, indicating a common ancient ancestor. However, during evolution, these organisms appear and evolve differently, leading to different cell organizations and physiological processes. Amongst the eukaryotes, an important distinction between plants and animals is evident, the most conspicuous difference being that plants are sessile organisms facing ever-changing environmental conditions. In addition, plants are mostly autotrophic, being able to synthesize carbohydrates molecules from the carbon dioxide in the air during the process of photosynthesis, using sunlight as an energy source. It is therefore interesting to analyze how, in these different contexts specific to both kingdoms of life, AQP function and regulation evolved. This review aims at highlighting similarities and differences between plant and mammal AQPs. Emphasis is given to the comparison of isoform numbers, their substrate selectivity, the regulation of the subcellular localization, and the channel activity. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
13 pages, 2813 KiB  
Review
Role of Aquaporins in Determining Carbon and Nitrogen Status in Higher Plants
by Limin Gao, Zhifeng Lu, Lei Ding, Junjie Guo, Min Wang, Ning Ling, Shiwei Guo and Qirong Shen
Int. J. Mol. Sci. 2018, 19(1), 35; https://doi.org/10.3390/ijms19010035 - 15 Jan 2018
Cited by 35 | Viewed by 6066
Abstract
Aquaporins (AQPs) are integral membrane proteins facilitating the transport of water and some small neutral molecules across cell membranes. In past years, much effort has been made to reveal the location of AQPs as well as their function in water transport, photosynthetic processes, [...] Read more.
Aquaporins (AQPs) are integral membrane proteins facilitating the transport of water and some small neutral molecules across cell membranes. In past years, much effort has been made to reveal the location of AQPs as well as their function in water transport, photosynthetic processes, and stress responses in higher plants. In the present review, we paid attention to the character of AQPs in determining carbon and nitrogen status. The role of AQPs during photosynthesis is characterized as its function in transporting water and CO2 across the membrane of chloroplast and thylakoid; recalculated results from published studies showed that over-expression of AQPs contributed to 25% and 50% increases in stomatal conductance (gs) and mesophyll conductance (gm), respectively. The nitrogen status in plants is regulated by AQPs through their effect on water flow as well as urea and NH4+ uptake, and the potential role of AQPs in alleviating ammonium toxicity is discussed. At the same time, root and/or shoot AQP expression is quite dependent on both N supply amounts and forms. Future research directions concerning the function of AQPs in regulating plant carbon and nitrogen status as well as C/N balance are also highlighted. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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12 pages, 401 KiB  
Review
Implications of Aquaglyceroporin 7 in Energy Metabolism
by Francesco Maria Iena and Janne Lebeck
Int. J. Mol. Sci. 2018, 19(1), 154; https://doi.org/10.3390/ijms19010154 - 04 Jan 2018
Cited by 27 | Viewed by 23962
Abstract
The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with [...] Read more.
The aquaglyceroporin AQP7 is a pore-forming transmembrane protein that facilitates the transport of glycerol across cell membranes. Glycerol is utilized both in carbohydrate and lipid metabolism. It is primarily stored in white adipose tissue as part of the triglyceride molecules. During states with increased lipolysis, such as fasting and diabetes, glycerol is released from adipose tissue and metabolized in other tissues. AQP7 is expressed in adipose tissue where it facilitates the efflux of glycerol, and AQP7 deficiency has been linked to increased glycerol kinase activity and triglyceride accumulation in adipose tissue, leading to obesity and secondary development of insulin resistance. However, AQP7 is also expressed in a wide range of other tissues, including kidney, muscle, pancreatic β-cells and liver, where AQP7 also holds the potential to influence whole body energy metabolism. The aim of the review is to summarize the current knowledge on AQP7 in adipose tissue, as well as AQP7 expressed in other tissues where AQP7 might play a significant role in modulating whole body energy metabolism. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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1794 KiB  
Review
The Role of Aquaporins in Ocular Lens Homeostasis
by Kevin L. Schey, Rosica S. Petrova, Romell B. Gletten and Paul J. Donaldson
Int. J. Mol. Sci. 2017, 18(12), 2693; https://doi.org/10.3390/ijms18122693 - 12 Dec 2017
Cited by 40 | Viewed by 5575
Abstract
Abstract: Aquaporins (AQPs), by playing essential roles in the maintenance of ocular lens homeostasis, contribute to the establishment and maintenance of the overall optical properties of the lens over many decades of life. Three aquaporins, AQP0, AQP1 and AQP5, each with distinctly [...] Read more.
Abstract: Aquaporins (AQPs), by playing essential roles in the maintenance of ocular lens homeostasis, contribute to the establishment and maintenance of the overall optical properties of the lens over many decades of life. Three aquaporins, AQP0, AQP1 and AQP5, each with distinctly different functional properties, are abundantly and differentially expressed in the different regions of the ocular lens. Furthermore, the diversity of AQP functionality is increased in the absence of protein turnover by age-related modifications to lens AQPs that are proposed to alter AQP function in the different regions of the lens. These regional differences in AQP functionality are proposed to contribute to the generation and directionality of the lens internal microcirculation; a system of circulating ionic and fluid fluxes that delivers nutrients to and removes wastes from the lens faster than could be achieved by passive diffusion alone. In this review, we present how regional differences in lens AQP isoforms potentially contribute to this microcirculation system by highlighting current areas of investigation and emphasizing areas where future work is required. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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221 KiB  
Review
Aquaporins during Pregnancy: Their Function and Significance
by Eszter Ducza, Adrienn Csányi and Róbert Gáspár
Int. J. Mol. Sci. 2017, 18(12), 2593; https://doi.org/10.3390/ijms18122593 - 01 Dec 2017
Cited by 27 | Viewed by 3504
Abstract
Water is the major component of cells and tissues, and the movement of water across the cell membrane is a fundamental property of life. Until the discovery of the first water channel, aquaporin, it was long assumed that the transport of water was [...] Read more.
Water is the major component of cells and tissues, and the movement of water across the cell membrane is a fundamental property of life. Until the discovery of the first water channel, aquaporin, it was long assumed that the transport of water was due to simple diffusion through the lipid bilayer membrane that encloses cells. Aquaporin (AQP) molecules were first discovered in the human uterus in 1994, and since then several studies have investigated these channels in the female reproductive system. The expressions of AQPs have been proven in the reproductive system. Their levels are altered during the implantation process, both in the uterus and the fetal cells, and participate in the control of the flow of amniotic fluid. They seem to be very important for the normal placental functions. AQPs are present during parturition, participating in the control of pregnant myometrial contractions and cervical ripening. However, most of the physiological and regulatory roles of AQPs are not clarified in the reproductive tract. Furthermore, no satisfactory knowledge is available about their sensitivities to different drugs. AQP-selective ligands may contribute to the development of new drug candidates and the therapy of several reproductive disorders. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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1603 KiB  
Review
Prostaglandin E2 in the Regulation of Water Transport in Renal Collecting Ducts
by Yuyuan Li, Yuanyi Wei, Feng Zheng, Youfei Guan and Xiaoyan Zhang
Int. J. Mol. Sci. 2017, 18(12), 2539; https://doi.org/10.3390/ijms18122539 - 27 Nov 2017
Cited by 27 | Viewed by 10824
Abstract
The kidney plays a central role in the regulation of the body water balance. The process of targeting the water channel aquaporin-2 (AQP2) on the apical plasma membrane of the collecting duct (CD) principal cells is mainly regulated by the antidiuretic peptide hormone [...] Read more.
The kidney plays a central role in the regulation of the body water balance. The process of targeting the water channel aquaporin-2 (AQP2) on the apical plasma membrane of the collecting duct (CD) principal cells is mainly regulated by the antidiuretic peptide hormone arginine vasopressin (AVP), which is responsible for the maintenance of water homeostasis. Recently, much attention has been focused on the local factors modulating renal water reabsorption by AQP2 in the collecting ducts, especially prostaglandin E2 (PGE2). PGE2 is a lipid mediator involved in a variety of physiological and pathophysiological processes in the kidney. The biological function of PGE2 is mainly mediated by four G-protein-coupled receptors, namely EP1-4, which couple to drive separate intracellular signaling pathways. Increasing evidence demonstrates that PGE2 is essential for renal water transport regulation via multiple mechanisms. Each EP receptor plays a unique role in regulating water reabsorption in renal collecting ducts. This brief review highlights the role of PGE2 in the regulation of water reabsorption and discusses the involvement of each EP receptor subtype in renal collecting duct. A better understanding of the role of PGE2 in renal water transport process may improve disease management strategies for water balance disorders, including nephrogenic diabetes insipidus. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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2231 KiB  
Review
Hereditary Nephrogenic Diabetes Insipidus: Pathophysiology and Possible Treatment. An Update
by Serena Milano, Monica Carmosino, Andrea Gerbino, Maria Svelto and Giuseppe Procino
Int. J. Mol. Sci. 2017, 18(11), 2385; https://doi.org/10.3390/ijms18112385 - 10 Nov 2017
Cited by 64 | Viewed by 15296
Abstract
Under physiological conditions, excessive loss of water through the urine is prevented by the release of the antidiuretic hormone arginine-vasopressin (AVP) from the posterior pituitary. In the kidney, AVP elicits a number of cellular responses, which converge on increasing the osmotic reabsorption of [...] Read more.
Under physiological conditions, excessive loss of water through the urine is prevented by the release of the antidiuretic hormone arginine-vasopressin (AVP) from the posterior pituitary. In the kidney, AVP elicits a number of cellular responses, which converge on increasing the osmotic reabsorption of water in the collecting duct. One of the key events triggered by the binding of AVP to its type-2 receptor (AVPR2) is the exocytosis of the water channel aquaporin 2 (AQP2) at the apical membrane the principal cells of the collecting duct. Mutations of either AVPR2 or AQP2 result in a genetic disease known as nephrogenic diabetes insipidus, which is characterized by the lack of responsiveness of the collecting duct to the antidiuretic action of AVP. The affected subject, being incapable of concentrating the urine, presents marked polyuria and compensatory polydipsia and is constantly at risk of severe dehydration. The molecular bases of the disease are fully uncovered, as well as the genetic or clinical tests for a prompt diagnosis of the disease in newborns. A real cure for nephrogenic diabetes insipidus (NDI) is still missing, and the main symptoms of the disease are handled with s continuous supply of water, a restrictive diet, and nonspecific drugs. Unfortunately, the current therapeutic options are limited and only partially beneficial. Further investigation in vitro or using the available animal models of the disease, combined with clinical trials, will eventually lead to the identification of one or more targeted strategies that will improve or replace the current conventional therapy and grant NDI patients a better quality of life. Here we provide an updated overview of the genetic defects causing NDI, the most recent strategies under investigation for rescuing the activity of mutated AVPR2 or AQP2, or for bypassing defective AVPR2 signaling and restoring AQP2 plasma membrane expression. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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9288 KiB  
Review
Aquaporin Protein-Protein Interactions
by Jennifer Virginia Roche and Susanna Törnroth-Horsefield
Int. J. Mol. Sci. 2017, 18(11), 2255; https://doi.org/10.3390/ijms18112255 - 27 Oct 2017
Cited by 54 | Viewed by 10447
Abstract
Aquaporins are tetrameric membrane-bound channels that facilitate transport of water and other small solutes across cell membranes. In eukaryotes, they are frequently regulated by gating or trafficking, allowing for the cell to control membrane permeability in a specific manner. Protein–protein interactions play crucial [...] Read more.
Aquaporins are tetrameric membrane-bound channels that facilitate transport of water and other small solutes across cell membranes. In eukaryotes, they are frequently regulated by gating or trafficking, allowing for the cell to control membrane permeability in a specific manner. Protein–protein interactions play crucial roles in both regulatory processes and also mediate alternative functions such as cell adhesion. In this review, we summarize recent knowledge about aquaporin protein–protein interactions; dividing the interactions into three types: (1) interactions between aquaporin tetramers; (2) interactions between aquaporin monomers within a tetramer (hetero-tetramerization); and (3) transient interactions with regulatory proteins. We particularly focus on the structural aspects of the interactions, discussing the small differences within a conserved overall fold that allow for aquaporins to be differentially regulated in an organism-, tissue- and trigger-specific manner. A deep knowledge about these differences is needed to fully understand aquaporin function and regulation in many physiological processes, and may enable design of compounds targeting specific aquaporins for treatment of human disease. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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398 KiB  
Review
A Review: Expression of Aquaporins in Otitis Media
by Su Young Jung, Sung Su Kim, Young Il Kim, Sang Hoon Kim and Seung Geun Yeo
Int. J. Mol. Sci. 2017, 18(10), 2164; https://doi.org/10.3390/ijms18102164 - 17 Oct 2017
Cited by 9 | Viewed by 3312
Abstract
Otitis media (OM) refers to inflammatory diseases of the middle ear (ME), regardless of cause or pathological mechanism. Among the molecular biological studies assessing the pathology of OM are investigations of the expression of aquaporins (AQPs) in the ME and Eustachian tube (ET). [...] Read more.
Otitis media (OM) refers to inflammatory diseases of the middle ear (ME), regardless of cause or pathological mechanism. Among the molecular biological studies assessing the pathology of OM are investigations of the expression of aquaporins (AQPs) in the ME and Eustachian tube (ET). To date, fifteen studies have evaluated AQPs expression in the ME and ET. Although the expression of individual AQPs varies by species and model, eleven types of AQP, AQP1 to AQP11, were found to be expressed in mammalian ME and ET. The review showed that: (1) various types of AQPs are expressed in the ME and ET; (2) AQP expression may vary by species; and (3) the distribution and levels of expression of AQPs may depend on the presence or absence of inflammation, with variations even in the same species and same tissue. Fluid accumulation in the ME and ET is a common pathological mechanism for all types of OM, causing edema in the tissue and inducing inflammation, thereby possibly involving various AQPs. The expression patterns of several AQPs, especially AQP1, 4 and 5, were found to be altered in response to inflammatory stimuli, including lipopolysaccharide (LPS), suggesting that AQPs may have immunological functions in OM. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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793 KiB  
Review
Aquaporin-3 in Cancer
by Saw Marlar, Helene H. Jensen, Frédéric H. Login and Lene N. Nejsum
Int. J. Mol. Sci. 2017, 18(10), 2106; https://doi.org/10.3390/ijms18102106 - 07 Oct 2017
Cited by 77 | Viewed by 10313
Abstract
Increasing evidence suggests that the water/glycerol channel aquaporin-3 (AQP3) plays a pivotal role in cancer metastasis. AQP3 knockout mice were resistant to skin tumor formation and overexpression correlated with metastasis and poor prognosis in patients with breast or gastric cancer. In cultured cancer [...] Read more.
Increasing evidence suggests that the water/glycerol channel aquaporin-3 (AQP3) plays a pivotal role in cancer metastasis. AQP3 knockout mice were resistant to skin tumor formation and overexpression correlated with metastasis and poor prognosis in patients with breast or gastric cancer. In cultured cancer cells, increased AQP3 expression stimulated several intracellular signaling pathways and resulted in increased cell proliferation, migration, and invasion as well as aggravation of epithelial-to-mesenchymal transition. Besides AQP facilitated water transport at the leading edge of migrating cells, AQP3 signaling mechanisms are beginning to be unraveled. Here, we give a thorough review of current knowledge regarding AQP3 expression in cancer and how AQP3 contributes to cancer progression via signaling that modulates cellular mechanisms. This review article will expand our understanding of the known pathophysiological findings regarding AQP3 in cancer. Full article
(This article belongs to the Special Issue Aquaporins: Water Channels Essential for Living Organisms)
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