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Banerjee S, Smith IM, Hengen AC, Stroka KM. Methods for studying mammalian aquaporin biology. Biol Methods Protoc 2023; 8:bpad031. [PMID: 38046463 PMCID: PMC10689382 DOI: 10.1093/biomethods/bpad031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/29/2023] [Accepted: 11/09/2023] [Indexed: 12/05/2023] Open
Abstract
Aquaporins (AQPs), transmembrane water-conducting channels, have earned a great deal of scrutiny for their critical physiological roles in healthy and disease cell states, especially in the biomedical field. Numerous methods have been implemented to elucidate the involvement of AQP-mediated water transport and downstream signaling activation in eliciting whole cell, tissue, and organ functional responses. To modulate these responses, other methods have been employed to investigate AQP druggability. This review discusses standard in vitro, in vivo, and in silico methods for studying AQPs, especially for biomedical and mammalian cell biology applications. We also propose some new techniques and approaches for future AQP research to address current gaps in methodology.
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Affiliation(s)
- Shohini Banerjee
- Fischell Department of Bioengineering, University of Maryland, MD 20742, United States
| | - Ian M Smith
- Fischell Department of Bioengineering, University of Maryland, MD 20742, United States
| | - Autumn C Hengen
- Fischell Department of Bioengineering, University of Maryland, MD 20742, United States
| | - Kimberly M Stroka
- Fischell Department of Bioengineering, University of Maryland, MD 20742, United States
- Marlene and Stewart Greenebaum Comprehensive Cancer Center, University of Maryland, Baltimore MD 21201, United States
- Biophysics Program, University of Maryland, MD 20742, United States
- Center for Stem Cell Biology and Regenerative Medicine, University of Maryland, Baltimore MD 21201, United States
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2
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Bailey AJ, Ukegbu CV, Giorgalli M, Besson TRB, Christophides GK, Vlachou D. Intracellular Plasmodium aquaporin 2 is important for sporozoite production in the mosquito vector and malaria transmission. Proc Natl Acad Sci U S A 2023; 120:e2304339120. [PMID: 37883438 PMCID: PMC10622946 DOI: 10.1073/pnas.2304339120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 09/09/2023] [Indexed: 10/28/2023] Open
Abstract
Malaria remains a devastating disease and, with current measures failing to control its transmission, there is a need for novel interventions. A family of proteins that have long been pursued as potential intervention targets are aquaporins, which are channels facilitating the movement of water and other solutes across membranes. We identify an aquaporin in malaria parasites and demonstrate that it is important for completion of Plasmodium development in the mosquito vector. Disruption of AQP2 in the human parasite Plasmodium falciparum and the rodent parasite Plasmodium berghei blocks sporozoite production inside oocysts established on mosquito midguts, greatly limiting parasite infection of salivary glands and transmission to a new host. In vivo epitope tagging of AQP2 in P. berghei, combined with immunofluorescence assays, reveals that the protein is localized in vesicle-like organelles found in the cytoplasm of gametocytes, ookinetes, and sporozoites. The number of these organelles varies between individual parasites and lifecycle stages suggesting that they are likely part of a dynamic endomembrane system. Phylogenetic analysis confirms that AQP2 is unique to malaria and closely related parasites and most closely resembles intracellular aquaporins. Structure prediction analyses identify several unusual features, including a large accessory extracellular loop and an arginine-to-phenylalanine substitution in the selectivity filter principally determining pore function, a unique feature among known aquaporins. This in conjunction with the importance of AQP2 for malaria transmission suggests that AQP2 may be a fruitful target of antimalarial interventions.
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Affiliation(s)
- Alexander J. Bailey
- Department of Life Sciences, Imperial College London, LondonSW7 2AZ, United Kingdom
| | | | - Maria Giorgalli
- Department of Life Sciences, Imperial College London, LondonSW7 2AZ, United Kingdom
| | | | | | - Dina Vlachou
- Department of Life Sciences, Imperial College London, LondonSW7 2AZ, United Kingdom
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3
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Login FH, Nejsum LN. Aquaporin water channels: roles beyond renal water handling. Nat Rev Nephrol 2023; 19:604-618. [PMID: 37460759 DOI: 10.1038/s41581-023-00734-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/30/2023] [Indexed: 08/18/2023]
Abstract
Aquaporin (AQP) water channels are pivotal to renal water handling and therefore in the regulation of body water homeostasis. However, beyond the kidney, AQPs facilitate water reabsorption and secretion in other cells and tissues, including sweat and salivary glands and the gastrointestinal tract. A growing body of evidence has also revealed that AQPs not only facilitate the transport of water but also the transport of several small molecules and gases such as glycerol, H2O2, ions and CO2. Moreover, AQPs are increasingly understood to contribute to various cellular processes, including cellular migration, adhesion and polarity, and to act upstream of several intracellular and intercellular signalling pathways to regulate processes such as cell proliferation, apoptosis and cell invasiveness. Of note, several AQPs are highly expressed in multiple cancers, where their expression can correlate with the spread of cancerous cells to lymph nodes and alter the response of cancers to conventional chemotherapeutics. These data suggest that AQPs have diverse roles in various homeostatic and physiological systems and may be exploited for prognostics and therapeutic interventions.
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Affiliation(s)
- Frédéric H Login
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Lene N Nejsum
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.
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4
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Jeuken K, Jaeger E, Matthews E, Beitz E. Methylthiosulfonate-Based Cysteine Modifiers as Alternative Inhibitors of Mercurial-Sensitive Aquaporins. Cells 2023; 12:1742. [PMID: 37443776 PMCID: PMC10340331 DOI: 10.3390/cells12131742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/23/2023] [Accepted: 06/26/2023] [Indexed: 07/15/2023] Open
Abstract
(1) Background: Several members of the ubiquitous aquaporin family, AQP, of water and neutral solute channels carry a cysteine residue in the selectivity filter region. Traditionally, toxic mercury-containing compounds are used to bind to the cysteine as covalent AQP inhibitors for physiological studies or analysis of structure-function relationships. (2) Methods: We tested thiol-reactive methylthiosulfonate reagents, MTS, as alternative Cys modifiers for AQP inhibition. Three MTS reagents transferring S-alkyl moieties of increasing size, i.e., S-methyl, S-n-propyl, and S-benzyl, were used with yeast-expressed water-selective AQP1 and the aquaglyceroporin AQP9. Respective Cys-to-Ala variants and mouse erythrocytes that naturally express AQP1 and AQP9 served as controls. (3) Results: Both wildtype AQP isoforms were inhibited by the Cys modifiers in a size-dependent manner, whereas the Cys-to-Ala-variants exhibited resistance. Sub-millimolar concentrations and incubation times in the minute range were sufficient. The modifications were reversible by treatment with the thiol reagents acetylcysteine, ACC, and dithiothreitol, DTT. (4) Conclusions: MTS reagents represent a valid alternative of low toxicity for the inhibition of mercurial-sensitive AQPs.
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Affiliation(s)
| | | | | | - Eric Beitz
- Department of Pharmaceutical and Medicinal Chemistry, Pharmaceutical Institute, Christian-Albrechts-University of Kiel, Gutenbergstr. 76, 24118 Kiel, Germany; (K.J.); (E.J.); (E.M.)
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Henderson SW, Nakayama Y, Whitelaw ML, Bruning JB, Anderson PA, Tyerman SD, Ramesh SA, Martinac B, Yool AJ. Proteoliposomes reconstituted with human aquaporin-1 reveal novel single-ion-channel properties. BIOPHYSICAL REPORTS 2023; 3:100100. [PMID: 36949749 PMCID: PMC10025285 DOI: 10.1016/j.bpr.2023.100100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Accepted: 01/11/2023] [Indexed: 01/15/2023]
Abstract
Human aquaporin 1 (hAQP1) forms homotetrameric channels that facilitate fluxes of water and small solutes across cell membranes. In addition to water channel activity, hAQP1 displays non-selective monovalent cation-channel activity gated by intracellular cyclic GMP. Dual water and ion-channel activity of hAQP1, thought to regulate cell shape and volume, could offer a target for novel therapeutics relevant to controlling cancer cell invasiveness. This study probed properties of hAQP1 ion channels using proteoliposomes, which, unlike conventional cell-based systems such as Xenopus laevis oocytes, are relatively free of background ion channels. Histidine-tagged recombinant hAQP1 protein was synthesized and purified from the methylotrophic yeast, Pichia pastoris, and reconstituted into proteoliposomes for biophysical analyses. Osmotic water channel activity confirmed correct folding and channel assembly. Ion-channel activity of hAQP1-Myc-His6 was recorded by patch-clamp electrophysiology with excised patches. In symmetrical potassium, the hAQP1-Myc-His6 channels displayed coordinated gating, a single-channel conductance of approximately 75 pS, and multiple subconductance states. Applicability of this method for structure-function analyses was tested using hAQP1-Myc-His6 D48A/D185A channels modified by site-directed mutations of charged Asp residues estimated to be adjacent to the central ion-conducting pore of the tetramer. No differences in conductance were detected between mutant and wild-type constructs, suggesting the open-state conformation could differ substantially from expectations based on crystal structures. Nonetheless, the method pioneered here for AQP1 demonstrates feasibility for future work defining structure-function relationships, screening pharmacological inhibitors, and testing other classes in the broad family of aquaporins for previously undiscovered ion-conducting capabilities.
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Affiliation(s)
- Sam W. Henderson
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia
| | - Yoshitaka Nakayama
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW 2010, Australia
- School of Clinical Medicine, UNSW Medicine & Health, St Vincent’s Healthcare Clinical Campus, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW Australia
| | - Murray L. Whitelaw
- Institute of Photonics and Advanced Sensing, The School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - John B. Bruning
- Institute of Photonics and Advanced Sensing, The School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Peter A. Anderson
- School of Biological Sciences, Faculty of Science and Engineering, Flinders University, Adelaide, SA 5001, Australia
| | - Stephen D. Tyerman
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine & Waite Research Institute, University of Adelaide, Glen Osmond, SA 5064, Australia
| | - Sunita A. Ramesh
- School of Biological Sciences, Faculty of Science and Engineering, Flinders University, Adelaide, SA 5001, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Lowy Packer Building, Darlinghurst, NSW 2010, Australia
- School of Clinical Medicine, UNSW Medicine & Health, St Vincent’s Healthcare Clinical Campus, Faculty of Medicine and Health, University of New South Wales, Sydney, NSW Australia
| | - Andrea J. Yool
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia
- Corresponding author
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6
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Aquaporins Display a Diversity in their Substrates. J Membr Biol 2023; 256:1-23. [PMID: 35986775 DOI: 10.1007/s00232-022-00257-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 07/13/2022] [Indexed: 02/07/2023]
Abstract
Aquaporins constitute a family of transmembrane proteins that function to transport water and other small solutes across the cell membrane. Aquaporins family members are found in diverse life forms. Aquaporins share the common structural fold consisting of six transmembrane alpha helices with a central water-transporting channel. Four such monomers assemble together to form tetramers as their biological unit. Initially, aquaporins were discovered as water-transporting channels, but several studies supported their involvement in mediating the facilitated diffusion of different solutes. The so-called water channel is able to transport a variety of substrates ranging from a neutral molecule to a charged molecule or a small molecule to a bulky molecule or even a gas molecule. This article gives an overview of a diverse range of substrates conducted by aquaporin family members. Prime focus is on human aquaporins where aquaporins show a wide tissue distribution and substrate specificity leading to various physiological functions. This review also highlights the structural mechanisms leading to the transport of water and glycerol. More research is needed to understand how one common fold enables the aquaporins to transport an array of solutes.
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7
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Xu L, Guo X, Wang W, Li C. Classification and Gene Structure of Aquaporins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1398:1-13. [PMID: 36717483 DOI: 10.1007/978-981-19-7415-1_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Aquaporins (AQPs) are a family of membrane water channels that basically function as regulators of intracellular and intercellular water flow. To date, 13 AQPs, distributed widely in specific cell types in various organs and tissues, have been characterized in humans. A pair of NPA boxes forming a pore is highly conserved among all aquaporins and is also key residues for the classification of AQP superfamily into four groups according to primary sequences. AQPs may also be classified based on their transport properties. So far, chromosome localization and gene structure of 13 human AQPs have been identified, which is definitely helpful for studying phenotypes and potential targets in naturally occurring and synthetic mutations in human or cells.
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Affiliation(s)
- Long Xu
- Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Xiangdong Guo
- Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China
| | - Weidong Wang
- Department of Pathophysiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
| | - Chunling Li
- Department of Physiology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou, China.
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Aquaporin Gating: A New Twist to Unravel Permeation through Water Channels. Int J Mol Sci 2022; 23:ijms232012317. [PMID: 36293170 PMCID: PMC9604103 DOI: 10.3390/ijms232012317] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 09/30/2022] [Accepted: 10/05/2022] [Indexed: 11/17/2022] Open
Abstract
Aquaporins (AQPs) are small transmembrane tetrameric proteins that facilitate water, solute and gas exchange. Their presence has been extensively reported in the biological membranes of almost all living organisms. Although their discovery is much more recent than ion transport systems, different biophysical approaches have contributed to confirm that permeation through each monomer is consistent with closed and open states, introducing the term gating mechanism into the field. The study of AQPs in their native membrane or overexpressed in heterologous systems have experimentally demonstrated that water membrane permeability can be reversibly modified in response to specific modulators. For some regulation mechanisms, such as pH changes, evidence for gating is also supported by high-resolution structures of the water channel in different configurations as well as molecular dynamics simulation. Both experimental and simulation approaches sustain that the rearrangement of conserved residues contributes to occlude the cavity of the channel restricting water permeation. Interestingly, specific charged and conserved residues are present in the environment of the pore and, thus, the tetrameric structure can be subjected to alter the positions of these charges to sustain gating. Thus, is it possible to explore whether the displacement of these charges (gating current) leads to conformational changes? To our knowledge, this question has not yet been addressed at all. In this review, we intend to analyze the suitability of this proposal for the first time.
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Markou A, Unger L, Abir-Awan M, Saadallah A, Halsey A, Balklava Z, Conner M, Törnroth-Horsefield S, Greenhill SD, Conner A, Bill RM, Salman MM, Kitchen P. Molecular mechanisms governing aquaporin relocalisation. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183853. [PMID: 34973181 PMCID: PMC8825993 DOI: 10.1016/j.bbamem.2021.183853] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 02/07/2023]
Abstract
The aquaporins (AQPs) form a family of integral membrane proteins that facilitate the movement of water across biological membrane by osmosis, as well as facilitating the diffusion of small polar solutes. AQPs have been recognised as drug targets for a variety of disorders associated with disrupted water or solute transport, including brain oedema following stroke or trauma, epilepsy, cancer cell migration and tumour angiogenesis, metabolic disorders, and inflammation. Despite this, drug discovery for AQPs has made little progress due to a lack of reproducible high-throughput assays and difficulties with the druggability of AQP proteins. However, recent studies have suggested that targetting the trafficking of AQP proteins to the plasma membrane is a viable alternative drug target to direct inhibition of the water-conducting pore. Here we review the literature on the trafficking of mammalian AQPs with a view to highlighting potential new drug targets for a variety of conditions associated with disrupted water and solute homeostasis.
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Affiliation(s)
- Andrea Markou
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Lucas Unger
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mohammed Abir-Awan
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Ahmed Saadallah
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Andrea Halsey
- MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 0QQ, UK
| | - Zita Balklava
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Matthew Conner
- School of Sciences, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK
| | | | - Stuart D Greenhill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alex Conner
- Institute of Clinical Sciences, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Roslyn M Bill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Mootaz M Salman
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK; Oxford Parkinson's Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK.
| | - Philip Kitchen
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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10
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Chow PH, Cox CD, Pei JV, Anabaraonye N, Nourmohammadi S, Henderson SW, Martinac B, Abdulmalik O, Yool AJ. Inhibition of the Aquaporin-1 Cation Conductance by Selected Furan Compounds Reduces Red Blood Cell Sickling. Front Pharmacol 2022; 12:794791. [PMID: 35111062 PMCID: PMC8801817 DOI: 10.3389/fphar.2021.794791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/06/2021] [Indexed: 11/13/2022] Open
Abstract
In sickle cell disease (SCD), the pathological shift of red blood cells (RBCs) into distorted morphologies under hypoxic conditions follows activation of a cationic leak current (Psickle) and cell dehydration. Prior work showed sickling was reduced by 5-hydroxylmethyl-2-furfural (5-HMF), which stabilized mutant hemoglobin and also blocked the Psickle current in RBCs, though the molecular basis of this 5-HMF-sensitive cation current remained a mystery. Work here is the first to test the hypothesis that Aquaporin-1 (AQP1) cation channels contribute to the monovalent component of Psickle. Human AQP1 channels expressed in Xenopus oocytes were evaluated for sensitivity to 5-HMF and four derivatives known to have differential efficacies in preventing RBC sickling. Ion conductances were measured by two-electrode voltage clamp, and osmotic water permeability by optical swelling assays. Compounds tested were: 5-HMF; 5-PMFC (5-(phenoxymethyl)furan-2-carbaldehyde); 5-CMFC (5-(4-chlorophenoxymethyl)furan-2-carbaldehyde); 5-NMFC (5-(2-nitrophenoxymethyl)-furan-2-carbaldehyde); and VZHE006 (tert-butyl (5-formylfuran-2-yl)methyl carbonate). The most effective anti-sickling agent, 5-PMFC, was the most potent inhibitor of the AQP1 ion conductance (98% block at 100 µM). The order of sensitivity of the AQP1 conductance to inhibition was 5-PMFC > VZHE006 > 5-CMFC ≥ 5-NMFC, which corresponded with effectiveness in protecting RBCs from sickling. None of the compounds altered AQP1 water channel activity. Combined application of a selective AQP1 ion channel blocker AqB011 (80 µM) with a selective hemoglobin modifying agent 5-NMFC (2.5 mM) increased anti-sickling effectiveness in red blood cells from human SCD patients. Another non-selective cation channel known to be expressed in RBCs, Piezo1, was unaffected by 2 mM 5-HMF. Results suggest that inhibition of AQP1 ion channels and capacity to modify hemoglobin are combined features of the most effective anti-sickling agents. Future therapeutics aimed at both targets could hold promise for improved treatments for SCD.
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Affiliation(s)
- Pak Hin Chow
- Aquaporin Physiology and Drug Discovery Program, School of Biomedicine, University of Adelaide, Adelaide, SA, Australia
| | - Charles D Cox
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW, Australia
| | - Jinxin V Pei
- Research School of Biology, College of Science, Australian National University, Canberra, ACT, Australia
| | - Nancy Anabaraonye
- Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Saeed Nourmohammadi
- Aquaporin Physiology and Drug Discovery Program, School of Biomedicine, University of Adelaide, Adelaide, SA, Australia
| | - Sam W Henderson
- Aquaporin Physiology and Drug Discovery Program, School of Biomedicine, University of Adelaide, Adelaide, SA, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW, Australia
| | - Osheiza Abdulmalik
- Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA, United States
| | - Andrea J Yool
- Aquaporin Physiology and Drug Discovery Program, School of Biomedicine, University of Adelaide, Adelaide, SA, Australia
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11
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Wagner K, Unger L, Salman MM, Kitchen P, Bill RM, Yool AJ. Signaling Mechanisms and Pharmacological Modulators Governing Diverse Aquaporin Functions in Human Health and Disease. Int J Mol Sci 2022; 23:1388. [PMID: 35163313 PMCID: PMC8836214 DOI: 10.3390/ijms23031388] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/18/2022] [Accepted: 01/20/2022] [Indexed: 02/07/2023] Open
Abstract
The aquaporins (AQPs) are a family of small integral membrane proteins that facilitate the bidirectional transport of water across biological membranes in response to osmotic pressure gradients as well as enable the transmembrane diffusion of small neutral solutes (such as urea, glycerol, and hydrogen peroxide) and ions. AQPs are expressed throughout the human body. Here, we review their key roles in fluid homeostasis, glandular secretions, signal transduction and sensation, barrier function, immunity and inflammation, cell migration, and angiogenesis. Evidence from a wide variety of studies now supports a view of the functions of AQPs being much more complex than simply mediating the passive flow of water across biological membranes. The discovery and development of small-molecule AQP inhibitors for research use and therapeutic development will lead to new insights into the basic biology of and novel treatments for the wide range of AQP-associated disorders.
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Affiliation(s)
- Kim Wagner
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia;
| | - Lucas Unger
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Mootaz M. Salman
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford OX1 3QX, UK;
- Oxford Parkinson’s Disease Centre, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Philip Kitchen
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Roslyn M. Bill
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK; (L.U.); (P.K.)
| | - Andrea J. Yool
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005, Australia;
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12
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Henderson SW, Nourmohammadi S, Ramesh SA, Yool AJ. Aquaporin ion conductance properties defined by membrane environment, protein structure, and cell physiology. Biophys Rev 2022; 14:181-198. [PMID: 35340612 PMCID: PMC8921385 DOI: 10.1007/s12551-021-00925-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/09/2021] [Indexed: 01/13/2023] Open
Abstract
Aquaporins (AQPs) are multifunctional transmembrane channel proteins permeable to water and an expanding array of solutes. AQP-mediated ion channel activity was first observed when purified AQP0 from bovine lens was incorporated into lipid bilayers. Electrophysiological properties of ion-conducting AQPs since discovered in plants, invertebrates, and mammals have been assessed using native, reconstituted, and heterologously expressed channels. Accumulating evidence is defining amino acid residues that govern differential solute permeability through intrasubunit and central pores of AQP tetramers. Rings of charged and hydrophobic residues around pores influence AQP selectivity, and are candidates for further work to define motifs that distinguish ion conduction capability, versus strict water and glycerol permeability. Similarities between AQP ion channels thus far include large single channel conductances and long open times, but differences in ionic selectivity, permeability to divalent cations, and mechanisms of gating (e.g., by voltage, pH, and cyclic nucleotides) are unique to subtypes. Effects of lipid environments in modulating parameters such as single channel amplitude could explain in part the variations in AQP ion channel properties observed across preparations. Physiological roles of the ion-conducting AQP classes span diverse processes including regulation of cell motility, organellar pH, neural development, signaling, and nutrient acquisition. Advances in computational methods can generate testable predictions of AQP structure-function relationships, which combined with innovative high-throughput assays could revolutionize the field in defining essential properties of ion-conducting AQPs, discovering new AQP ion channels, and understanding the effects of AQP interactions with proteins, signaling cascades, and membrane lipids.
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Affiliation(s)
- Sam W. Henderson
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005 Australia
| | | | - Sunita A. Ramesh
- College of Science and Engineering, Flinders University, Bedford Park, SA 5042 Australia
| | - Andrea J. Yool
- School of Biomedicine, University of Adelaide, Adelaide, SA 5005 Australia
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13
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Tan C, Zeng J, Wu G, Zheng L, Huang M, Huang X. Xinshuitong Capsule extract attenuates doxorubicin-induced myocardial edema via regulation of cardiac aquaporins in the chronic heart failure rats. Biomed Pharmacother 2021; 144:112261. [PMID: 34628163 DOI: 10.1016/j.biopha.2021.112261] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 09/23/2021] [Accepted: 09/26/2021] [Indexed: 02/05/2023] Open
Abstract
Doxorubicin (Dox), an effective antineoplastic drug, was limited use for cardiotoxicity. Xinshuitong Capsule (XST), a patented herbal formula, showed desirable beneficial effects in the treatment of chronic heart failure (CHF) patients. However, the drug on Dox-induced cardiotoxicity remains unclear. Ninety male Sprague-Dawley rats were randomized into two groups: 15 rats were selected as the normal group and 75 rats were injected intraperitoneally with Dox to establish CHF rat models, the success ones were randomly divided into five groups: low XST (LXST), medium XST (MXST) or high XST (HXST) (4.9, 9.8, or 19.6 g/kg d) administrated intragastrically twice a day for 4 weeks, with the captopril-treated group and the model group as comparison. The model group showed the cardiac functions generally impaired, and CHF mortality rate higher (47%) than those in the XST-treated groups (averaged 24%, P < 0.05). Compared with XST-treated groups, myocardial remodeling, inflammation and desarcomerization, and higher water content more severe in the cardiac tissue in the model group (P < 0.05), which was associated with higher expressions of mRNA or protein levels of AQP1, 4 and 7. Dox-impaired cardiac functions, cardiac remodeling and myocardial edema could be dose-dependently reverted by XST treatment. XST could inhibit AQP1, 4 and 7 at mRNA levels or at protein levels, which was associated with the attenuation of myocardial edema and cardiac remodeling, decreasing the ventricular stiffness and improving the cardiac functions and rats' survival. AQPs is involved in cardiac edema composed one of the mechanisms of Dox-induced cardiotoxicity, XSTvia inhibition of AQPs relieved the Dox-induced side effects.
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MESH Headings
- Administration, Oral
- Animals
- Aquaporin 1/antagonists & inhibitors
- Aquaporin 1/genetics
- Aquaporin 1/metabolism
- Aquaporin 4/antagonists & inhibitors
- Aquaporin 4/genetics
- Aquaporin 4/metabolism
- Aquaporins/antagonists & inhibitors
- Aquaporins/genetics
- Aquaporins/metabolism
- Body Water/metabolism
- Capsules
- Cardiotoxicity
- Chronic Disease
- Disease Models, Animal
- Doxorubicin
- Drugs, Chinese Herbal/administration & dosage
- Drugs, Chinese Herbal/pharmacology
- Edema, Cardiac/chemically induced
- Edema, Cardiac/metabolism
- Edema, Cardiac/pathology
- Edema, Cardiac/prevention & control
- Heart Failure/chemically induced
- Heart Failure/metabolism
- Heart Failure/pathology
- Heart Failure/prevention & control
- Male
- Myocardium/metabolism
- Myocardium/pathology
- Rats, Sprague-Dawley
- Signal Transduction
- Ventricular Function, Left/drug effects
- Ventricular Remodeling/drug effects
- Rats
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Affiliation(s)
- Chunjiang Tan
- Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, China; The Third People's Hospital affiliated to Fujian University of Chinese Medicine, Fuzhou, Fujian, China; Fujian Academy of Integrative Medicine, Fuzhou, Fujian, China; Fujian Provincial Key Laboratory of Integrative Medicine on Geriatrics, Fuzhou, Fujian, China.
| | - Jianwei Zeng
- Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, China; Fujian Academy of Integrative Medicine, Fuzhou, Fujian, China; Fujian Provincial Key Laboratory of Integrative Medicine on Geriatrics, Fuzhou, Fujian, China.
| | - Guangwen Wu
- Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, China; Fujian Academy of Integrative Medicine, Fuzhou, Fujian, China; Fujian Provincial Key Laboratory of Integrative Medicine on Geriatrics, Fuzhou, Fujian, China.
| | - Liangpu Zheng
- Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, China; Fujian Academy of Integrative Medicine, Fuzhou, Fujian, China; Fujian Provincial Key Laboratory of Integrative Medicine on Geriatrics, Fuzhou, Fujian, China.
| | - Meiya Huang
- Fujian University of Traditional Chinese Medicine, Fuzhou, Fujian, China; Fujian Academy of Integrative Medicine, Fuzhou, Fujian, China; Fujian Provincial Key Laboratory of Integrative Medicine on Geriatrics, Fuzhou, Fujian, China.
| | - Xiansheng Huang
- Department of Cardiology, the First Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong, China.
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14
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Tyerman SD, McGaughey SA, Qiu J, Yool AJ, Byrt CS. Adaptable and Multifunctional Ion-Conducting Aquaporins. ANNUAL REVIEW OF PLANT BIOLOGY 2021; 72:703-736. [PMID: 33577345 DOI: 10.1146/annurev-arplant-081720-013608] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Aquaporins function as water and neutral solute channels, signaling hubs, disease virulence factors, and metabolon components. We consider plant aquaporins that transport ions compared to some animal counterparts. These are candidates for important, as yet unidentified, cation and anion channels in plasma, tonoplast, and symbiotic membranes. For those individual isoforms that transport ions, water, and gases, the permeability spans 12 orders of magnitude. This requires tight regulation of selectivity via protein interactions and posttranslational modifications. A phosphorylation-dependent switch between ion and water permeation in AtPIP2;1 might be explained by coupling between the gates of the four monomer water channels and the central pore of the tetramer. We consider the potential for coupling between ion and water fluxes that could form the basis of an electroosmotic transducer. A grand challenge in understanding the roles of ion transporting aquaporins is their multifunctional modes that are dependent on location, stress, time, and development.
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Affiliation(s)
- Stephen D Tyerman
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Samantha A McGaughey
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
| | - Jiaen Qiu
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, South Australia 5005, Australia;
| | - Caitlin S Byrt
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
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15
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Targeting Aquaporins in Novel Therapies for Male and Female Breast and Reproductive Cancers. Cells 2021; 10:cells10020215. [PMID: 33499000 PMCID: PMC7911300 DOI: 10.3390/cells10020215] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/13/2021] [Accepted: 01/20/2021] [Indexed: 12/24/2022] Open
Abstract
Aquaporins are membrane channels in the broad family of major intrinsic proteins (MIPs), with 13 classes showing tissue-specific distributions in humans. As key physiological modulators of water and solute homeostasis, mutations, and dysfunctions involving aquaporins have been associated with pathologies in all major organs. Increases in aquaporin expression are associated with greater severity of many cancers, particularly in augmenting motility and invasiveness for example in colon cancers and glioblastoma. However, potential roles of altered aquaporin (AQP) function in reproductive cancers have been understudied to date. Published work reviewed here shows distinct classes aquaporin have differential roles in mediating cancer metastasis, angiogenesis, and resistance to apoptosis. Known mechanisms of action of AQPs in other tissues are proving relevant to understanding reproductive cancers. Emerging patterns show AQPs 1, 3, and 5 in particular are highly expressed in breast, endometrial, and ovarian cancers, consistent with their gene regulation by estrogen response elements, and AQPs 3 and 9 in particular are linked with prostate cancer. Continuing work is defining avenues for pharmacological targeting of aquaporins as potential therapies to reduce female and male reproductive cancer cell growth and invasiveness.
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16
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Qiu J, McGaughey SA, Groszmann M, Tyerman SD, Byrt CS. Phosphorylation influences water and ion channel function of AtPIP2;1. PLANT, CELL & ENVIRONMENT 2020; 43:2428-2442. [PMID: 32678928 DOI: 10.1111/pce.13851] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 07/09/2020] [Accepted: 07/09/2020] [Indexed: 05/24/2023]
Abstract
The phosphorylation state of two serine residues within the C-terminal domain of AtPIP2;1 (S280, S283) regulates its plasma membrane localization in response to salt and osmotic stress. Here, we investigated whether the phosphorylation state of S280 and S283 also influence AtPIP2;1 facilitated water and cation transport. A series of single and double S280 and S283 phosphomimic and phosphonull AtPIP2;1 mutants were tested in heterologous systems. In Xenopus laevis oocytes, phosphomimic mutants AtPIP2;1 S280D, S283D, and S280D/S283D had significantly greater ion conductance for Na+ and K+ , whereas the S280A single phosphonull mutant had greater water permeability. We observed a phosphorylation-dependent inverse relationship between AtPIP2;1 water and ion transport with a 10-fold change in both. The results revealed that phosphorylation of S280 and S283 influences the preferential facilitation of ion or water transport by AtPIP2;1. The results also hint that other regulatory sites play roles that are yet to be elucidated. Expression of the AtPIP2;1 phosphorylation mutants in Saccharomyces cerevisiae confirmed that phosphorylation influences plasma membrane localization, and revealed higher Na+ accumulation for S280A and S283D mutants. Collectively, the results show that phosphorylation in the C-terminal domain of AtPIP2;1 influences its subcellular localization and cation transport capacity.
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Affiliation(s)
- Jiaen Qiu
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
| | - Samantha A McGaughey
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australia
| | - Michael Groszmann
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australia
| | - Stephen D Tyerman
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
| | - Caitlin S Byrt
- ARC Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australia
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17
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Chow PH, Kourghi M, Pei JV, Nourmohammadi S, Yool AJ. 5-Hydroxymethyl-Furfural and Structurally Related Compounds Block the Ion Conductance in Human Aquaporin-1 Channels and Slow Cancer Cell Migration and Invasion. Mol Pharmacol 2020; 98:38-48. [PMID: 32434851 DOI: 10.1124/mol.119.119172] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 04/20/2020] [Indexed: 12/18/2022] Open
Abstract
Aquaporin-1 (AQP1) dual water and ion channels enhance migration and invasion when upregulated in leading edges of certain classes of cancer cells. Work here identifies structurally related furan compounds as novel inhibitors of AQP1 ion channels. 5-Hydroxymethyl-2-furfural (5HMF), a component of natural medicinal honeys, and three structurally related compounds, 5-nitro-2-furoic acid (5NFA), 5-acetoxymethyl-2-furaldehyde (5AMF), and methyl-5-nitro-2-furoate (M5NF), were analyzed for effects on water and ion channel activities of human AQP1 channels expressed in Xenopus oocytes. Two-electrode voltage clamp showed dose-dependent block of the AQP1 ion current by 5HMF (IC50 0.43 mM), 5NFA (IC50 1.2 mM), and 5AMF (IC50 ∼3 mM) but no inhibition by M5NF. In silico docking predicted the active ligands interacted with glycine 165, located in loop D gating domains surrounding the intracellular vestibule of the tetrameric central pore. Water fluxes through separate intrasubunit pores were unaltered by the furan compounds (at concentrations up to 5 mM). Effects on cell migration, invasion, and cytoskeletal organization in vitro were tested in high-AQP1-expressing cancer lines, colon cancer (HT29) and AQP1-expressing breast cancer (MDA), and low-AQP1-expressing SW480. 5HMF, 5NFA, and 5AMF selectively impaired cell motility in the AQP1-enriched cell lines. In contrast, M5NF immobilized all the cancer lines by disrupting actin cytoskeleton. No reduction in cell viability was observed at doses that were effective in blocking motility. These results define furans as a new class of AQP1 ion channel inhibitors for basic research and potential lead compounds for development of therapeutic agents targeting aquaporin channel activity. SIGNIFICANCE STATEMENT: 5-Hydroxymethyl-2-furfural (5HMF), a component of natural medicinal honeys, blocks the ion conductance but not the water flux through human Aquaporin-1 (AQP1) channels and impairs AQP1-dependent cell migration and invasiveness in cancer cell lines. Analyses of 5HMT and structural analogs demonstrate a structure-activity relationship for furan compounds, supported by in silico docking modeling. This work identifies new low-cost pharmacological antagonists for AQP1 available to researchers internationally. Furans merit consideration as a new class of therapeutic agents for controlling cancer metastasis.
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Affiliation(s)
- Pak Hin Chow
- Adelaide Medical School, University of Adelaide, Adelaide, Australia (P.H.C., M.K., J.V.P., S.N., A.J.Y.) and College of Science, The Australian National University, Canberra, Australia (J.V.P.)
| | - Mohamad Kourghi
- Adelaide Medical School, University of Adelaide, Adelaide, Australia (P.H.C., M.K., J.V.P., S.N., A.J.Y.) and College of Science, The Australian National University, Canberra, Australia (J.V.P.)
| | - Jinxin V Pei
- Adelaide Medical School, University of Adelaide, Adelaide, Australia (P.H.C., M.K., J.V.P., S.N., A.J.Y.) and College of Science, The Australian National University, Canberra, Australia (J.V.P.)
| | - Saeed Nourmohammadi
- Adelaide Medical School, University of Adelaide, Adelaide, Australia (P.H.C., M.K., J.V.P., S.N., A.J.Y.) and College of Science, The Australian National University, Canberra, Australia (J.V.P.)
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, Australia (P.H.C., M.K., J.V.P., S.N., A.J.Y.) and College of Science, The Australian National University, Canberra, Australia (J.V.P.)
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18
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Yool AJ, Ramesh S. Molecular Targets for Combined Therapeutic Strategies to Limit Glioblastoma Cell Migration and Invasion. Front Pharmacol 2020; 11:358. [PMID: 32292341 PMCID: PMC7118801 DOI: 10.3389/fphar.2020.00358] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/10/2020] [Indexed: 12/21/2022] Open
Abstract
The highly invasive nature of glioblastoma imposes poor prospects for patient survival. Molecular evidence indicates glioblastoma cells undergo an intriguing expansion of phenotypic properties to include neuron-like signaling using excitable membrane ion channels and synaptic proteins, augmenting survival and motility. Neurotransmitter receptors, membrane signaling, excitatory receptors, and Ca2+ responses are important candidates for the design of customized treatments for cancers within the heterogeneous central nervous system. Relatively few published studies of glioblastoma multiforme (GBM) have evaluated pharmacological agents targeted to signaling pathways in limiting cancer cell motility. Transcriptomic analyses here identified classes of ion channels, ionotropic receptors, and synaptic proteins that are enriched in human glioblastoma biopsy samples. The pattern of GBM-enriched gene expression points to a major role for glutamate signaling. However, the predominant role of AMPA receptors in fast excitatory signaling throughout the central nervous system raises a challenge on how to target inhibitors selectively to cancer cells while maintaining tolerability. This review critically evaluates a panel of ligand- and voltage-gated ion channels and synaptic proteins upregulated in GBM, and the evidence for their potential roles in the pathological disease progress. Evidence suggests combinations of therapies could be more effective than single agents alone. Natural plant products used in traditional medicines for the treatment of glioblastoma contain flavonoids, terpenoids, polyphenols, epigallocatechin gallate, quinones, and saponins, which might serendipitously include agents that modulate some classes of signaling compounds highlighted in this review. New therapeutic strategies are likely to exploit evidence-based combinations of selected agents, each at a low dose, to create new cancer cell-specific therapeutics.
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Affiliation(s)
- Andrea J. Yool
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Sunita Ramesh
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
- College of Science and Engineering, Flinders University, Adelaide, SA, Australia
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19
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Rauen K, Pop V, Trabold R, Badaut J, Plesnila N. Vasopressin V 1a Receptors Regulate Cerebral Aquaporin 1 after Traumatic Brain Injury. J Neurotrauma 2020; 37:665-674. [PMID: 31547764 PMCID: PMC7045352 DOI: 10.1089/neu.2019.6653] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Brain edema formation contributes to secondary brain damage and unfavorable outcome after traumatic brain injury (TBI). Aquaporins (AQP), highly selective water channels, are involved in the formation of post-trauma brain edema; however, their regulation is largely unknown. Because vasopressin receptors are involved in AQP-mediated water transport in the kidney and inhibition of V1a receptors reduces post-trauma brain edema formation, we hypothesize that cerebral AQPs may be regulated by V1a receptors. Cerebral Aqp1 and Aqp4 messenger ribonucleic acid (mRNA) and AQP1 and AQP4 protein levels were quantified in wild-type and V1a receptor knockout (V1a-/-) mice before and 15 min, 1, 3, 6, 12, or 24 h after experimental TBI by controlled cortical impact. In non-traumatized mice, we found AQP1 and AQP4 expression in cortical neurons and astrocytes, respectively. Experimental TBI had no effect on Aqp4 mRNA or AQP4 protein expression, but increased Aqp1 mRNA (p < 0.05) and AQP1 protein expression (p < 0.05) in both hemispheres. The Aqp1 mRNA and AQP1 protein regulation was blunted in V1a receptor knockout mice. The V1a receptors regulate cerebral AQP1 expression after experimental TBI, thereby unraveling the molecular mechanism by which these receptors may mediate brain edema formation after TBI.
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Affiliation(s)
- Katrin Rauen
- Laboratory of Experimental Neurosurgery, Department of Neurosurgery & Institute for Surgical Research, University of Munich Medical Center, Munich, Germany
- Institute for Stroke and Dementia Research (ISD), University of Munich Medical Center, Munich, Germany
- University Hospital of Psychiatry Zurich, Department of Geriatric Psychiatry & Institute for Regenerative Medicine, University of Zurich, Zurich, Switzerland
| | - Viorela Pop
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, California
| | - Raimund Trabold
- Laboratory of Experimental Neurosurgery, Department of Neurosurgery & Institute for Surgical Research, University of Munich Medical Center, Munich, Germany
| | - Jerome Badaut
- Department of Pediatrics, Loma Linda University School of Medicine, Loma Linda, California
- Aquitaine Institute for Cognitive and Integrative Neuroscience, University of Bordeaux, Bordeaux, France
| | - Nikolaus Plesnila
- Laboratory of Experimental Neurosurgery, Department of Neurosurgery & Institute for Surgical Research, University of Munich Medical Center, Munich, Germany
- Institute for Stroke and Dementia Research (ISD), University of Munich Medical Center, Munich, Germany
- Munich Cluster for Systems Neurology (Synergy), Munich, Germany
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20
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Ferré-Dolcet L, Rodríguez-Gil JE, Yeste M, Rigau T, Rivera Del Alamo MM. Tyrosine phosphorylation is not a relevant mechanism to modulate aquaporin 2 activity in gestational queen endometrium and placenta. Reprod Domest Anim 2020; 55:448-453. [PMID: 31951059 DOI: 10.1111/rda.13636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 01/09/2020] [Indexed: 11/30/2022]
Abstract
Aquaporins have been shown to be regulated by phosphorylation of serine residues, but the possible role of tyrosine residues phosphorylation has not been evaluated. Changes in the localization of aquaporin 2 (AQP2) in the queen endometrium have been related to serum progesterone levels. The aim of this study was to determine whether these AQP2-localization changes are mediated by variations in its tyrosine phosphorylation levels. Twelve queens were included in the study and divided into (a) non-macroscopically pregnant with low levels of progesterone; (b) non-macroscopically pregnant with high levels of progesterone; (c) 30 days of pregnancy; and (d) 60 days of pregnancy. Samples from endometrium and placental transference zone were obtained, immunoprecipitated and analysed by immunoblotting to determine the abundance of AQP2 and its relative levels of tyrosine phosphorylation. No significant differences in the tyrosine phosphorylation levels of immunoprecipated-AQP2 were observed between groups. We can thus conclude that changes in the localization of AQP2 in the queen endometrium are not modulated by tyrosine phosphorylation.
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Affiliation(s)
- Lluis Ferré-Dolcet
- Unit of Animal Reproduction, Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
| | - Joan Enric Rodríguez-Gil
- Unit of Animal Reproduction, Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
| | - Marc Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, Girona, Spain.,Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, Girona, Spain
| | - Teresa Rigau
- Unit of Animal Reproduction, Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
| | - Maria Montserrat Rivera Del Alamo
- Unit of Animal Reproduction, Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain
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21
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Phosphorylation of TIP3 Aquaporins during Phaseolus vulgaris Embryo Development. Cells 2019; 8:cells8111362. [PMID: 31683651 PMCID: PMC6912600 DOI: 10.3390/cells8111362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 11/19/2022] Open
Abstract
The membrane phosphoproteome in plant seed changes dynamically during embryo development. We examined the patterns of Phaseolus vulgaris (common bean) seed membrane protein phosphorylation from the mid-maturation stage until two days after germination. Serine and threonine phosphorylation declined during seed maturation while tyrosine phosphorylation remained relatively constant. We discovered that the aquaporin PvTIP3;1 is the primary seed membrane phosphoprotein, and PvTIP3;2 shows a very low level of expression. The level of phosphorylated Ser7 in PvTIP3;1 increased four-fold after seed maturation. Since phosphorylation increases water channel activity, we infer that water transport by PvTIP3;1 is highest in dry and germinating seeds, which would be optimal for seed imbibition. By the use of isoform-specific, polyclonal peptide antibodies, we found that PvTIP3;2 is expressed in a developmental pattern similar to PvTIP3;1. Unexpectedly, PvTIP3;2 is tyrosine phosphorylated following seed maturation, which may suggest a mechanism for the regulation of PvTIP3;2 following seed germination. Analysis of protein secondary structure by circular dichroism spectroscopy indicated that the amino-terminal domain of PvTIP3;1 is generally unstructured, and phosphorylation increases polyproline II (PPII) helical structure. The carboxy-terminal domain also gains PPII character, but in a pH-dependent manner. These structural changes are a first step to understand TIP3 aquaporin regulation.
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22
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De Ieso ML, Pei JV, Nourmohammadi S, Smith E, Chow PH, Kourghi M, Hardingham JE, Yool AJ. Combined pharmacological administration of AQP1 ion channel blocker AqB011 and water channel blocker Bacopaside II amplifies inhibition of colon cancer cell migration. Sci Rep 2019; 9:12635. [PMID: 31477744 PMCID: PMC6718670 DOI: 10.1038/s41598-019-49045-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 08/13/2019] [Indexed: 12/14/2022] Open
Abstract
Aquaporin-1 (AQP1) has been proposed as a dual water and cation channel that when upregulated in cancers enhances cell migration rates; however, the mechanism remains unknown. Previous work identified AqB011 as an inhibitor of the gated human AQP1 cation conductance, and bacopaside II as a blocker of AQP1 water pores. In two colorectal adenocarcinoma cell lines, high levels of AQP1 transcript were confirmed in HT29, and low levels in SW480 cells, by quantitative PCR (polymerase chain reaction). Comparable differences in membrane AQP1 protein levels were demonstrated by immunofluorescence imaging. Migration rates were quantified using circular wound closure assays and live-cell tracking. AqB011 and bacopaside II, applied in combination, produced greater inhibitory effects on cell migration than did either agent alone. The high efficacy of AqB011 alone and in combination with bacopaside II in slowing HT29 cell motility correlated with abundant membrane localization of AQP1 protein. In SW480, neither agent alone was effective in blocking cell motility; however, combined application did cause inhibition of motility, consistent with low levels of membrane AQP1 expression. Bacopaside alone or combined with AqB011 also significantly impaired lamellipodial formation in both cell lines. Knockdown of AQP1 with siRNA (confirmed by quantitative PCR) reduced the effectiveness of the combined inhibitors, confirming AQP1 as a target of action. Invasiveness measured using transwell filters layered with extracellular matrix in both cell lines was inhibited by AqB011, with a greater potency in HT29 than SW480. A side effect of bacopaside II at high doses was a potentiation of invasiveness, that was reversed by AqB011. Results here are the first to demonstrate that combined block of the AQP1 ion channel and water pores is more potent in impairing motility across diverse classes of colon cancer cells than single agents alone.
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Affiliation(s)
- Michael L De Ieso
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Jinxin V Pei
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Saeed Nourmohammadi
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Eric Smith
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
- Oncology Department, The Basil Hetzel Institute, The Queen Elizabeth Hospital, Woodville, SA, 5011, Australia
| | - Pak Hin Chow
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Mohamad Kourghi
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Jennifer E Hardingham
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia
- Oncology Department, The Basil Hetzel Institute, The Queen Elizabeth Hospital, Woodville, SA, 5011, Australia
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, SA, 5005, Australia.
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23
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Verkerk AO, Lodder EM, Wilders R. Aquaporin Channels in the Heart-Physiology and Pathophysiology. Int J Mol Sci 2019; 20:ijms20082039. [PMID: 31027200 PMCID: PMC6514906 DOI: 10.3390/ijms20082039] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 04/19/2019] [Accepted: 04/23/2019] [Indexed: 12/11/2022] Open
Abstract
Mammalian aquaporins (AQPs) are transmembrane channels expressed in a large variety of cells and tissues throughout the body. They are known as water channels, but they also facilitate the transport of small solutes, gasses, and monovalent cations. To date, 13 different AQPs, encoded by the genes AQP0–AQP12, have been identified in mammals, which regulate various important biological functions in kidney, brain, lung, digestive system, eye, and skin. Consequently, dysfunction of AQPs is involved in a wide variety of disorders. AQPs are also present in the heart, even with a specific distribution pattern in cardiomyocytes, but whether their presence is essential for proper (electro)physiological cardiac function has not intensively been studied. This review summarizes recent findings and highlights the involvement of AQPs in normal and pathological cardiac function. We conclude that AQPs are at least implicated in proper cardiac water homeostasis and energy balance as well as heart failure and arsenic cardiotoxicity. However, this review also demonstrates that many effects of cardiac AQPs, especially on excitation-contraction coupling processes, are virtually unexplored.
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Affiliation(s)
- Arie O Verkerk
- Department of Medical Biology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Elisabeth M Lodder
- Department of Experimental Cardiology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam University Medical Centers, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
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Pei JV, Heng S, De Ieso ML, Sylvia G, Kourghi M, Nourmohammadi S, Abell AD, Yool AJ. Development of a Photoswitchable Lithium-Sensitive Probe to Analyze Nonselective Cation Channel Activity in Migrating Cancer Cells. Mol Pharmacol 2019; 95:573-583. [PMID: 30858164 DOI: 10.1124/mol.118.115428] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 03/05/2019] [Indexed: 11/22/2022] Open
Abstract
This is the first work to use a newly designed Li+-selective photoswitchable probe Sabrina Heng Lithium (SHL) in living colon cancer cells to noninvasively monitor cation channel activity in real time by the appearance of lithium hot spots detected by confocal microscopy. Punctate Li+ hot spots are clustered in the lamellipodial leading edges of HT29 human colon cancer cells and are colocalized with aquaporin-1 (AQP1) channels. AQP1 is a dual water and cyclic-nucleotide-gated cation channel located in lamellipodia and is essential for rapid cell migration in a subset of aggressive cancers. Both the Li+ hot spots and cell migration are blocked in HT29 cells by the AQP1 ion channel antagonist AqB011. In contrast, Li+ hot spots are not evident in a poorly migrating colon cancer cell line, SW620, which lacks comparable membrane expression of AQP1. Knockdown of AQP1 by RNA interference in HT29 cells significantly impairs Li+ hot spot activity. The SHL probe loaded in living cells shows signature chemical properties of ionic selectivity and reversibility. Dynamic properties of the Li+ hot spots, turning on and off, are confirmed by time-lapse imaging. SHL is a powerful tool for evaluating cation channel function in living cells in real time, with particular promise for studies of motile cells or interlinked networks not easily analyzed by electrophysiological methods. The ability to reset SHL by photoswitching allows monitoring of dynamic signals over time. Future applications of the Li+ probe could include high-throughput optical screening for discovering new classes of channels, or finding new pharmacological modulators for nonselective cation channels.
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Affiliation(s)
- Jinxin V Pei
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Sabrina Heng
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Michael L De Ieso
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Georgina Sylvia
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Mohamad Kourghi
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Saeed Nourmohammadi
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Andrew D Abell
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
| | - Andrea J Yool
- Adelaide Medical School, and the Institute for Photonics and Advanced Sensing (IPAS) (J.V.P., M.D.I., M.K., S.N., A.J.Y.) and ARC Centre of Excellence for Nanoscale BioPhotonics, IPAS, School of Physical Sciences (S.H., G.S., A.D.A.), University of Adelaide, Adelaide, South Australia, Australia
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Nesverova V, Törnroth-Horsefield S. Phosphorylation-Dependent Regulation of Mammalian Aquaporins. Cells 2019; 8:cells8020082. [PMID: 30678081 PMCID: PMC6406877 DOI: 10.3390/cells8020082] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/17/2019] [Accepted: 01/21/2019] [Indexed: 12/26/2022] Open
Abstract
Water homeostasis is fundamental for cell survival. Transport of water across cellular membranes is governed by aquaporins—tetrameric integral membrane channels that are highly conserved throughout the prokaryotic and eukaryotic kingdoms. In eukaryotes, specific regulation of these channels is required and is most commonly carried out by shuttling the protein between cellular compartments (trafficking) or by opening and closing the channel (gating). Structural and functional studies have revealed phosphorylation as a ubiquitous mechanism in aquaporin regulation by both regulatory processes. In this review we summarize what is currently known about the phosphorylation-dependent regulation of mammalian aquaporins. Focusing on the water-specific aquaporins (AQP0–AQP5), we discuss how gating and trafficking are controlled by phosphorylation and how phosphorylation affects the binding of aquaporins to regulatory proteins, thereby highlighting structural details and dissecting the contribution of individual phosphorylated residues when possible. Our aim is to provide an overview of the mechanisms behind how aquaporin phosphorylation controls cellular water balance and to identify key areas where further studies are needed.
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Affiliation(s)
- Veronika Nesverova
- Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, Box 124, 221 00 Lund, Sweden.
| | - Susanna Törnroth-Horsefield
- Department of Biochemistry and Structural Biology, Center for Molecular Protein Science, Lund University, Box 124, 221 00 Lund, Sweden.
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26
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Ginsenoside Rg3: Potential Molecular Targets and Therapeutic Indication in Metastatic Breast Cancer. MEDICINES 2019; 6:medicines6010017. [PMID: 30678106 PMCID: PMC6473622 DOI: 10.3390/medicines6010017] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 01/21/2019] [Accepted: 01/23/2019] [Indexed: 01/28/2023]
Abstract
Breast cancer is still one of the most prevalent cancers and a leading cause of cancer death worldwide. The key challenge with cancer treatment is the choice of the best therapeutic agents with the least possible toxicities on the patient. Recently, attention has been drawn to herbal compounds, in particular ginsenosides, extracted from the root of the Ginseng plant. In various studies, significant anti-cancer properties of ginsenosides have been reported in different cancers. The mode of action of ginsenoside Rg3 (Rg3) in in vitro and in vivo breast cancer models and its value as an anti-cancer treatment for breast cancer will be reviewed.
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Ozu M, Galizia L, Acuña C, Amodeo G. Aquaporins: More Than Functional Monomers in a Tetrameric Arrangement. Cells 2018; 7:E209. [PMID: 30423856 PMCID: PMC6262540 DOI: 10.3390/cells7110209] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/27/2018] [Accepted: 11/07/2018] [Indexed: 12/11/2022] Open
Abstract
Aquaporins (AQPs) function as tetrameric structures in which each monomer has its own permeable pathway. The combination of structural biology, molecular dynamics simulations, and experimental approaches has contributed to improve our knowledge of how protein conformational changes can challenge its transport capacity, rapidly altering the membrane permeability. This review is focused on evidence that highlights the functional relationship between the monomers and the tetramer. In this sense, we address AQP permeation capacity as well as regulatory mechanisms that affect the monomer, the tetramer, or tetramers combined in complex structures. We therefore explore: (i) water permeation and recent evidence on ion permeation, including the permeation pathway controversy-each monomer versus the central pore of the tetramer-and (ii) regulatory mechanisms that cannot be attributed to independent monomers. In particular, we discuss channel gating and AQPs that sense membrane tension. For the latter we propose a possible mechanism that includes the monomer (slight changes of pore shape, the number of possible H-bonds between water molecules and pore-lining residues) and the tetramer (interactions among monomers and a positive cooperative effect).
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Affiliation(s)
- Marcelo Ozu
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Luciano Galizia
- Instituto de investigaciones Médicas A. Lanari, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, Laboratorio de Canales Iónicos, Instituto de Investigaciones Médicas (IDIM), Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
| | - Cynthia Acuña
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Gabriela Amodeo
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
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Kourghi M, De Ieso ML, Nourmohammadi S, Pei JV, Yool AJ. Identification of Loop D Domain Amino Acids in the Human Aquaporin-1 Channel Involved in Activation of the Ionic Conductance and Inhibition by AqB011. Front Chem 2018; 6:142. [PMID: 29755973 PMCID: PMC5934433 DOI: 10.3389/fchem.2018.00142] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/12/2018] [Indexed: 01/08/2023] Open
Abstract
Aquaporins are integral proteins that facilitate the transmembrane transport of water and small solutes. In addition to enabling water flux, mammalian Aquaporin-1 (AQP1) channels activated by cyclic GMP can carry non-selective monovalent cation currents, selectively blocked by arylsulfonamide compounds AqB007 (IC50 170 μM) and AqB011 (IC50 14 μM). In silico models suggested that ligand docking might involve the cytoplasmic loop D (between AQP1 transmembrane domains 4 and 5), but the predicted site of interaction remained to be tested. Work here shows that mutagenesis of two conserved arginine residues in loop D slowed the activation of the AQP1 ion conductance and impaired the sensitivity of the channel to block by AqB011. Substitution of residues in loop D with proline showed effects on ion conductance amplitude that varied with position, suggesting that the structural conformation of loop D is important for AQP1 channel gating. Human AQP1 wild type, AQP1 mutant channels with alanines substituted for two arginines (R159A+R160A), and mutants with proline substituted for single residues threonine (T157P), aspartate (D158P), arginine (R159P, R160P), or glycine (G165P) were expressed in Xenopus laevis oocytes. Conductance responses were analyzed by two-electrode voltage clamp. Optical osmotic swelling assays and confocal microscopy were used to confirm mutant and wild type AQP1-expressing oocytes were expressed in the plasma membrane. After application of membrane-permeable cGMP, R159A+R160A channels had a significantly slower rate of activation as compared with wild type, consistent with impaired gating. AQP1 R159A+R160A channels showed no significant block by AqB011 at 50 μM, in contrast to the wild type channel which was blocked effectively. T157P, D158P, and R160P mutations had impaired activation compared to wild type; R159P showed no significant effect; and G165P appeared to augment the conductance amplitude. These findings provide evidence for the role of the loop D as a gating domain for AQP1 ion channels, and identify the likely site of interaction of AqB011 in the proximal loop D sequence.
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Affiliation(s)
- Mohamad Kourghi
- Aquaporin Physiology and Drug Discovery Program, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Michael L De Ieso
- Aquaporin Physiology and Drug Discovery Program, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Saeed Nourmohammadi
- Aquaporin Physiology and Drug Discovery Program, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Jinxin V Pei
- Aquaporin Physiology and Drug Discovery Program, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Andrea J Yool
- Aquaporin Physiology and Drug Discovery Program, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
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De Ieso ML, Yool AJ. Mechanisms of Aquaporin-Facilitated Cancer Invasion and Metastasis. Front Chem 2018; 6:135. [PMID: 29922644 PMCID: PMC5996923 DOI: 10.3389/fchem.2018.00135] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 04/09/2018] [Indexed: 01/02/2023] Open
Abstract
Cancer is a leading cause of death worldwide, and its incidence is rising with numbers expected to increase 70% in the next two decades. The fact that current mainline treatments for cancer patients are accompanied by debilitating side effects prompts a growing demand for new therapies that not only inhibit growth and proliferation of cancer cells, but also control invasion and metastasis. One class of targets gaining international attention is the aquaporins, a family of membrane-spanning water channels with diverse physiological functions and extensive tissue-specific distributions in humans. Aquaporins−1,−2,−3,−4,−5,−8, and−9 have been linked to roles in cancer invasion, and metastasis, but their mechanisms of action remain to be fully defined. Aquaporins are implicated in the metastatic cascade in processes of angiogenesis, cellular dissociation, migration, and invasion. Cancer invasion and metastasis are proposed to be potentiated by aquaporins in boosting tumor angiogenesis, enhancing cell volume regulation, regulating cell-cell and cell-matrix adhesions, interacting with actin cytoskeleton, regulating proteases and extracellular-matrix degrading molecules, contributing to the regulation of epithelial-mesenchymal transitions, and interacting with signaling pathways enabling motility and invasion. Pharmacological modulators of aquaporin channels are being identified and tested for therapeutic potential, including compounds derived from loop diuretics, metal-containing organic compounds, plant natural products, and other small molecules. Further studies on aquaporin-dependent functions in cancer metastasis are needed to define the differential contributions of different classes of aquaporin channels to regulation of fluid balance, cell volume, small solute transport, signal transduction, their possible relevance as rate limiting steps, and potential values as therapeutic targets for invasion and metastasis.
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Affiliation(s)
- Michael L De Ieso
- Department of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Andrea J Yool
- Department of Physiology, Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
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Kourghi M, Pei JV, De Ieso ML, Nourmohammadi S, Chow PH, Yool AJ. Fundamental structural and functional properties of Aquaporin ion channels found across the kingdoms of life. Clin Exp Pharmacol Physiol 2018; 45:401-409. [PMID: 29193257 DOI: 10.1111/1440-1681.12900] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 11/06/2017] [Accepted: 11/16/2017] [Indexed: 01/09/2023]
Abstract
Aquaporin (AQP) channels in the major intrinsic protein (MIP) family are known to facilitate transmembrane water fluxes in prokaryotes and eukaryotes. Some classes of AQPs also conduct ions, glycerol, urea, CO2 , nitric oxide, and other small solutes. Ion channel activity has been demonstrated for mammalian AQPs 0, 1, 6, Drosophila Big Brain (BIB), soybean nodulin 26, and rockcress AtPIP2;1. More classes are likely to be discovered. Newly identified blockers are providing essential tools for establishing physiological roles of some of the AQP dual water and ion channels. For example, the arylsulfonamide AqB011 which selectively blocks the central ion pore of mammalian AQP1 has been shown to impair migration of HT29 colon cancer cells. Traditional herbal medicines are sources of selective AQP1 inhibitors that also slow cancer cell migration. The finding that plant AtPIP2;1 expressed in root epidermal cells mediates an ion conductance regulated by calcium and protons provided insight into molecular mechanisms of environmental stress responses. Expression of lens MIP (AQP0) is essential for maintaining the structure, integrity and transparency of the lens, and Drosophila BIB contributes to neurogenic signalling pathways to control the developmental fate of fly neuroblast cells; however, the ion channel roles remain to be defined for MIP and BIB. A broader portfolio of pharmacological agents is needed to investigate diverse AQP ion channel functions in situ. Understanding the dual water and ion channel roles of AQPs could inform the development of novel agents for rational interventions in diverse challenges from agriculture to human health.
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Affiliation(s)
- Mohamad Kourghi
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Jinxin V Pei
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Michael L De Ieso
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | | | - Pak Hin Chow
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, SA, Australia
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Kourghi M, Nourmohammadi S, Pei JV, Qiu J, McGaughey S, Tyerman SD, Byrt CS, Yool AJ. Divalent Cations Regulate the Ion Conductance Properties of Diverse Classes of Aquaporins. Int J Mol Sci 2017; 18:ijms18112323. [PMID: 29099773 PMCID: PMC5713292 DOI: 10.3390/ijms18112323] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 10/27/2017] [Accepted: 10/28/2017] [Indexed: 12/20/2022] Open
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 Homo sapiens HsAQP1, rat Rattus norvegicus RnAQP4, RnAQP5, and fly Drosophilamelanogaster 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.
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Affiliation(s)
- Mohamad Kourghi
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Saeed Nourmohammadi
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Jinxin V Pei
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Jiaen Qiu
- School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Samantha McGaughey
- School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Stephen D Tyerman
- School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Caitlin S Byrt
- School of Agriculture, Food and Wine, University of Adelaide, Adelaide, SA 5005, Australia.
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, SA 5005, Australia.
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Lind U, Järvå M, Alm Rosenblad M, Pingitore P, Karlsson E, Wrange AL, Kamdal E, Sundell K, André C, Jonsson PR, Havenhand J, Eriksson LA, Hedfalk K, Blomberg A. Analysis of aquaporins from the euryhaline barnacle Balanus improvisus reveals differential expression in response to changes in salinity. PLoS One 2017; 12:e0181192. [PMID: 28715506 PMCID: PMC5513457 DOI: 10.1371/journal.pone.0181192] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Accepted: 06/26/2017] [Indexed: 12/13/2022] Open
Abstract
Barnacles are sessile macro-invertebrates, found along rocky shores in coastal areas worldwide. The euryhaline bay barnacle Balanus improvisus (Darwin, 1854) (= Amphibalanus improvisus) can tolerate a wide range of salinities, but the molecular mechanisms underlying the osmoregulatory capacity of this truly brackish species are not well understood. Aquaporins are pore-forming integral membrane proteins that facilitate transport of water, small solutes and ions through cellular membranes, and that have been shown to be important for osmoregulation in many organisms. The knowledge of the function of aquaporins in crustaceans is, however, limited and nothing is known about them in barnacles. We here present the repertoire of aquaporins from a thecostracan crustacean, the barnacle B. improvisus, based on genome and transcriptome sequencing. Our analyses reveal that B. improvisus contains eight genes for aquaporins. Phylogenetic analysis showed that they represented members of the classical water aquaporins (Aqp1, Aqp2), the aquaglyceroporins (Glp1, Glp2), the unorthodox aquaporin (Aqp12) and the arthropod-specific big brain aquaporin (Bib). Interestingly, we also found two big brain-like proteins (BibL1 and BibL2) constituting a new group of aquaporins not yet described in arthropods. In addition, we found that the two water-specific aquaporins were expressed as C-terminal splice variants. Heterologous expression of some of the aquaporins followed by functional characterization showed that Aqp1 transported water and Glp2 water and glycerol, agreeing with the predictions of substrate specificity based on 3D modeling and phylogeny. To investigate a possible role for the B. improvisus aquaporins in osmoregulation, mRNA expression changes in adult barnacles were analysed after long-term acclimation to different salinities. The most pronounced expression difference was seen for AQP1 with a substantial (>100-fold) decrease in the mantle tissue in low salinity (3 PSU) compared to high salinity (33 PSU). Our study provides a base for future mechanistic studies on the role of aquaporins in osmoregulation.
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Affiliation(s)
- Ulrika Lind
- Department of Marine Sciences, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Michael Järvå
- Department of Chemistry and Molecular Biology, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Magnus Alm Rosenblad
- Department of Marine Sciences, National Infrastructure of Bioinformatics (NBIS), Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Piero Pingitore
- Department of Molecular and Clinical Medicine, Wallenberg Laboratory, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Emil Karlsson
- Department of Marine Sciences, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Anna-Lisa Wrange
- RISE Research Institute of Sweden, Section for Chemistry and Materials, Borås, Sweden
| | - Emelie Kamdal
- Department of Chemistry and Molecular Biology, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Kristina Sundell
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Carl André
- Department of Marine Sciences-Tjärnö, University of Gothenburg, Strömstad, Sweden
| | - Per R. Jonsson
- Department of Marine Sciences-Tjärnö, University of Gothenburg, Strömstad, Sweden
| | - Jon Havenhand
- Department of Marine Sciences-Tjärnö, University of Gothenburg, Strömstad, Sweden
| | - Leif A. Eriksson
- Department of Chemistry and Molecular Biology, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Kristina Hedfalk
- Department of Chemistry and Molecular Biology, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
| | - Anders Blomberg
- Department of Marine Sciences, Lundberg laboratory, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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Byrt CS, Zhao M, Kourghi M, Bose J, Henderson SW, Qiu J, Gilliham M, Schultz C, Schwarz M, Ramesh SA, Yool A, Tyerman S. Non-selective cation channel activity of aquaporin AtPIP2;1 regulated by Ca 2+ and pH. PLANT, CELL & ENVIRONMENT 2017; 40:802-815. [PMID: 27620834 DOI: 10.1111/pce.12832] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 09/08/2016] [Accepted: 09/10/2016] [Indexed: 05/20/2023]
Abstract
The aquaporin AtPIP2;1 is an abundant plasma membrane intrinsic protein in Arabidopsis thaliana that is implicated in stomatal closure, and is highly expressed in plasma membranes of root epidermal cells. When expressed in Xenopus laevis oocytes, AtPIP2;1 increased water permeability and induced a non-selective cation conductance mainly associated with Na+ . A mutation in the water pore, G103W, prevented both the ionic conductance and water permeability of PIP2;1. Co-expression of AtPIP2;1 with AtPIP1;2 increased water permeability but abolished the ionic conductance. AtPIP2;2 (93% identical to AtPIP2;1) similarly increased water permeability but not ionic conductance. The ionic conductance was inhibited by the application of extracellular Ca2+ and Cd2+ , with Ca2+ giving a biphasic dose-response with a prominent IC50 of 0.32 mм comparable with a previous report of Ca2+ sensitivity of a non-selective cation channel (NSCC) in Arabidopsis root protoplasts. Low external pH also inhibited ionic conductance (IC50 pH 6.8). Xenopus oocytes and Saccharomyces cerevisiae expressing AtPIP2;1 accumulated more Na+ than controls. Establishing whether AtPIP2;1 has dual ion and water permeability in planta will be important in understanding the roles of this aquaporin and if AtPIP2;1 is a candidate for a previously reported NSCC responsible for Ca2+ and pH sensitive Na+ entry into roots.
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Affiliation(s)
- Caitlin S Byrt
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Manchun Zhao
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Mohamad Kourghi
- Discipline of Physiology, School of Medicine, University of Adelaide, South Australia, 5005, Australia
| | - Jayakumar Bose
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Sam W Henderson
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Jiaen Qiu
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Matthew Gilliham
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Carolyn Schultz
- Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Manuel Schwarz
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Sunita A Ramesh
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
| | - Andrea Yool
- Discipline of Physiology, School of Medicine, University of Adelaide, South Australia, 5005, Australia
| | - Steve Tyerman
- Australian Research Council Centre of Excellence in Plant Energy Biology, Waite Research Institute and School of Agriculture, Food and Wine, The University of Adelaide, Glen Osmond, South Australia, 5064, Australia
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Abstract
Aquaporins (AQPs ) are a family of membrane water channels that basically function as regulators of intracellular and intercellular water flow. To date, thirteen AQPs , which are distributed widely in specific cell types in various organs and tissues, have been characterized in humans. Four AQP monomers, each of which consists of six membrane-spanning alpha-helices that have a central water-transporting pore, assemble to form tetramers, forming the functional units in the membrane. AQP facilitates osmotic water transport across plasma membranes and thus transcellular fluid movement. The cellular functions of aquaporins are regulated by posttranslational modifications , e.g. phosphorylation, ubiquitination, glycosylation, subcellular distribution, degradation, and protein interactions. Insight into the molecular mechanisms responsible for regulated aquaporin trafficking and synthesis is proving to be fundamental for development of novel therapeutic targets or reliable diagnostic and prognostic biomarkers.
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Affiliation(s)
- Chunling Li
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, 74# Zhongshan Er Road, Guangzhou, 510080, China
| | - Weidong Wang
- Institute of Hypertension, Zhongshan School of Medicine, Sun Yat-sen University, 74# Zhongshan Er Road, Guangzhou, 510080, China.
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Bajic JE, Eden GL, Lampton LS, Cheah KY, Lymn KA, Pei JV, Yool AJ, Howarth GS. Rhubarb extract partially improves mucosal integrity in chemotherapy-induced intestinal mucositis. World J Gastroenterol 2016; 22:8322-8333. [PMID: 27729739 PMCID: PMC5055863 DOI: 10.3748/wjg.v22.i37.8322] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 07/07/2016] [Accepted: 08/08/2016] [Indexed: 02/06/2023] Open
Abstract
AIM To investigate the effects of orally gavaged aqueous rhubarb extract (RE) on 5-fluorouracil (5-FU)-induced intestinal mucositis in rats.
METHODS Female Dark Agouti rats (n = 8/group) were gavaged daily (1 mL) with water, high-dose RE (HDR; 200 mg/kg) or low-dose RE (LDR; 20mg/kg) for eight days. Intestinal mucositis was induced (day 5) with 5-FU (150 mg/kg) via intraperitoneal injection. Intestinal tissue samples were collected for myeloperoxidase (MPO) activity and histological examination. Xenopus oocytes expressing aquaporin 4 water channels were prepared to examine the effect of aqueous RE on cell volume, indicating a potential mechanism responsible for modulating net fluid absorption and secretion in the gastrointestinal tract. Statistical significance was assumed at P < 0.05 by one-way ANOVA.
RESULTS Bodyweight was significantly reduced in rats administered 5-FU compared to healthy controls (P < 0.01). Rats administered 5-FU significantly increased intestinal MPO levels (≥ 307%; P < 0.001), compared to healthy controls. However, LDR attenuated this effect in 5-FU treated rats, significantly decreasing ileal MPO activity (by 45%; P < 0.05), as compared to 5-FU controls. 5-FU significantly reduced intestinal mucosal thickness (by ≥ 29% P < 0.001) as compared to healthy controls. LDR significantly increased ileal mucosal thickness in 5-FU treated rats (19%; P < 0.05) relative to 5-FU controls. In xenopus oocytes expressing AQP4 water channels, RE selectively blocked water influx into the cell, induced by a decrease in external osmotic pressure. As water efflux was unaltered by the presence of extracellular RE, the directional flow of water across the epithelial barrier, in the presence of extracellular RE, indicated that RE may alleviate water loss across the epithelial barrier and promote intestinal health in chemotherapy-induced intestinal mucositis.
CONCLUSION In summary, low dose RE improves selected parameters of mucosal integrity and reduces ileal inflammation, manifesting from 5-FU-induced intestinal mucositis.
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Pei JV, Kourghi M, De Ieso ML, Campbell EM, Dorward HS, Hardingham JE, Yool AJ. Differential Inhibition of Water and Ion Channel Activities of Mammalian Aquaporin-1 by Two Structurally Related Bacopaside Compounds Derived from the Medicinal Plant Bacopa monnieri. Mol Pharmacol 2016; 90:496-507. [PMID: 27474162 DOI: 10.1124/mol.116.105882] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2016] [Accepted: 07/26/2016] [Indexed: 11/22/2022] Open
Abstract
Aquaporin-1 (AQP1) is a major intrinsic protein that facilitates flux of water and other small solutes across cell membranes. In addition to its function as a water channel in maintaining fluid homeostasis, AQP1 also acts as a nonselective cation channel gated by cGMP, a property shown previously to facilitate rapid cell migration in a AQP1-expressing colon cancer cell line. Here we report two new modulators of AQP1 channels, bacopaside I and bacopaside II, isolated from the medicinal plant Bacopa monnieri Screening was conducted in the Xenopus oocyte expression system, using quantitative swelling and two-electrode voltage clamp techniques. Results showed bacopaside I blocked both the water (IC50 117 μM) and ion channel activities of AQP1 but did not alter AQP4 activity, whereas bacopaside II selectively blocked the AQP1 water channel (IC50 18 μM) without impairing the ionic conductance. These results fit with predictions from in silico molecular modeling. Both bacopasides were tested in migration assays using HT29 and SW480 colon cancer cell lines, with high and low levels of AQP1 expression, respectively. Bacopaside I (IC50 48 μM) and bacopaside II (IC50 14 μM) impaired migration of HT29 cells but had minimal effect on SW480 cell migration. Our results are the first to identify differential AQP1 modulators isolated from a medicinal plant. Bacopasides could serve as novel lead compounds for pharmaceutic development of selective aquaporin modulators.
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Affiliation(s)
- Jinxin V Pei
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Mohamad Kourghi
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Michael L De Ieso
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Ewan M Campbell
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Hilary S Dorward
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Jennifer E Hardingham
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
| | - Andrea J Yool
- School of Medicine (J.V.P., M.K., M.L.D.I., J.E.H., A.J.Y.), and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, Australia; School of Biological Sciences, University of Aberdeen, Aberdeen, Scotland, United Kingdom (E.M.C.); Molecular Oncology Laboratory, Basil Hetzel Institute, Queen Elizabeth Hospital, Woodville, Australia (H.S.D., J.E.H.)
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Kourghi M, Pei JV, De Ieso ML, Flynn G, Yool AJ. Bumetanide Derivatives AqB007 and AqB011 Selectively Block the Aquaporin-1 Ion Channel Conductance and Slow Cancer Cell Migration. Mol Pharmacol 2015; 89:133-40. [PMID: 26467039 DOI: 10.1124/mol.115.101618] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/13/2015] [Indexed: 12/24/2022] Open
Abstract
Aquaporins (AQPs) in the major intrinsic family of proteins mediate fluxes of water and other small solutes across cell membranes. AQP1 is a water channel, and under permissive conditions, a nonselective cation channel gated by cGMP. In addition to mediating fluid transport, AQP1 expression facilitates rapid cell migration in cell types including colon cancers and glioblastoma. Work here defines new pharmacological derivatives of bumetanide that selectively inhibit the ion channel, but not the water channel, activity of AQP1. Human AQP1 was analyzed in the Xenopus laevis oocyte expression system by two-electrode voltage clamp and optical osmotic swelling assays. The aquaporin ligand bumetanide derivative AqB011 was the most potent blocker of the AQP1 ion conductance (IC50 of 14 μM), with no effect on water channel activity (at up to 200 μM). The order of potency for inhibition of the ionic conductance was AqB011 > AqB007 >> AqB006 ≥ AqB001. Migration of human colon cancer (HT29) cells was assessed with a wound-closure assay in the presence of a mitotic inhibitor. AqB011 and AqB007 significantly reduced migration rates of AQP1-positive HT29 cells without affecting viability. The order of potency for AQP1 ion channel block matched the order for inhibition of cell migration, as well as in silico modeling of the predicted order of energetically favored binding. Docking models suggest that AqB011 and AqB007 interact with the intracellular loop D domain, a region involved in AQP channel gating. Inhibition of AQP1 ionic conductance could be a useful adjunct therapeutic approach for reducing metastasis in cancers that upregulate AQP1 expression.
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Affiliation(s)
- Mohamad Kourghi
- School of Medicine (M.K., J.V.P., M.L.D.I., A.J.Y.) and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, South Australia, Australia; and Spacefill Enterprises LLC, Oro Valley, Arizona (G.F.)
| | - Jinxin V Pei
- School of Medicine (M.K., J.V.P., M.L.D.I., A.J.Y.) and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, South Australia, Australia; and Spacefill Enterprises LLC, Oro Valley, Arizona (G.F.)
| | - Michael L De Ieso
- School of Medicine (M.K., J.V.P., M.L.D.I., A.J.Y.) and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, South Australia, Australia; and Spacefill Enterprises LLC, Oro Valley, Arizona (G.F.)
| | - Gary Flynn
- School of Medicine (M.K., J.V.P., M.L.D.I., A.J.Y.) and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, South Australia, Australia; and Spacefill Enterprises LLC, Oro Valley, Arizona (G.F.)
| | - Andrea J Yool
- School of Medicine (M.K., J.V.P., M.L.D.I., A.J.Y.) and Institute for Photonics and Advanced Sensing (J.V.P., A.J.Y.), University of Adelaide, Adelaide, South Australia, Australia; and Spacefill Enterprises LLC, Oro Valley, Arizona (G.F.)
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Kitchen P, Day RE, Salman MM, Conner MT, Bill RM, Conner AC. Beyond water homeostasis: Diverse functional roles of mammalian aquaporins. Biochim Biophys Acta Gen Subj 2015; 1850:2410-21. [PMID: 26365508 DOI: 10.1016/j.bbagen.2015.08.023] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 08/25/2015] [Accepted: 08/30/2015] [Indexed: 01/02/2023]
Abstract
BACKGROUND Aquaporin (AQP) water channels are best known as passive transporters of water that are vital for water homeostasis. SCOPE OF REVIEW AQP knockout studies in whole animals and cultured cells, along with naturally occurring human mutations suggest that the transport of neutral solutes through AQPs has important physiological roles. Emerging biophysical evidence suggests that AQPs may also facilitate gas (CO2) and cation transport. AQPs may be involved in cell signalling for volume regulation and controlling the subcellular localization of other proteins by forming macromolecular complexes. This review examines the evidence for these diverse functions of AQPs as well their physiological relevance. MAJOR CONCLUSIONS As well as being crucial for water homeostasis, AQPs are involved in physiologically important transport of molecules other than water, regulation of surface expression of other membrane proteins, cell adhesion, and signalling in cell volume regulation. GENERAL SIGNIFICANCE Elucidating the full range of functional roles of AQPs beyond the passive conduction of water will improve our understanding of mammalian physiology in health and disease. The functional variety of AQPs makes them an exciting drug target and could provide routes to a range of novel therapies.
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Affiliation(s)
- Philip Kitchen
- Molecular Organisation and Assembly in Cells Doctoral Training Centre, University of Warwick, Coventry CV4 7AL, UK
| | - Rebecca E Day
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Mootaz M Salman
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Matthew T Conner
- Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, UK
| | - Roslyn M Bill
- School of Life & Health Sciences and Aston Research Centre for Healthy Ageing, Aston University, Aston Triangle, Birmingham B4 7ET, UK
| | - Alex C Conner
- Institute of Clinical Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Shachar-Hill B, Hill AE, Powell J, Skepper JN, Shachar-Hill Y. Mercury-sensitive water channels as possible sensors of water potentials in pollen. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:5195-205. [PMID: 24098048 PMCID: PMC3830494 DOI: 10.1093/jxb/ert311] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The growing pollen tube is central to plant reproduction and is a long-standing model for cellular tip growth in biology. Rapid osmotically driven growth is maintained under variable conditions, which requires osmosensing and regulation. This study explores the mechanism of water entry and the potential role of osmosensory regulation in maintaining pollen growth. The osmotic permeability of the plasmalemma of Lilium pollen tubes was measured from plasmolysis rates to be 1.32±0.31×10(-3) cm s(-1). Mercuric ions reduce this permeability by 65%. Simulations using an osmotic model of pollen tube growth predict that an osmosensor at the cell membrane controls pectin deposition at the cell tip; inhibiting the sensor is predicted to cause tip bursting due to cell wall thinning. It was found that adding mercury to growing pollen tubes caused such a bursting of the tips. The model indicates that lowering the osmotic permeability per se does not lead to bursting but rather to thickening of the tip. The time course of induced bursting showed no time lag and was independent of mercury concentration, compatible with a surface site of action. The submaximal bursting response to intermediate mercuric ion concentration was independent of the concentration of calcium ions, showing that bursting is not due to a competitive inhibition of calcium binding or entry. Bursting with the same time course was also shown by cells growing on potassium-free media, indicating that potassium channels (implicated in mechanosensing) are not involved in the bursting response. The possible involvement of mercury-sensitive water channels as osmosensors and current knowledge of these in pollen cells are discussed.
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Affiliation(s)
| | - Adrian E. Hill
- Department of Physiology, Development and Neuroscience, Cambridge University, Cambridge, UK
- * To whom correspondence should be addressed. E-mail:
| | - Janet Powell
- Multi-Imaging Centre, Cambridge University, Cambridge, UK
| | | | - Yair Shachar-Hill
- Department of Plant Biology, Plant Biology Building, Michigan State University, East Lansing, MI 48824-1312, USA
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Genetic deletion of aquaporin-1 results in microcardia and low blood pressure in mouse with intact nitric oxide-dependent relaxation, but enhanced prostanoids-dependent relaxation. Pflugers Arch 2013; 466:237-51. [PMID: 23873354 DOI: 10.1007/s00424-013-1325-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2013] [Revised: 06/27/2013] [Accepted: 06/28/2013] [Indexed: 12/21/2022]
Abstract
The water channels, aquaporins (AQPs) are key mediators of transcellular fluid transport. However, their expression and role in cardiac tissue is poorly characterized. Particularly, AQP1 was suggested to transport other molecules (nitric oxide (NO), hydrogen peroxide (H2O2)) with potential major bearing on cardiovascular physiology. We therefore examined the expression of all AQPs and the phenotype of AQP1 knockout mice (vs. wild-type littermates) under implanted telemetry in vivo, as well as endothelium-dependent relaxation in isolated aortas and resistance vessels ex vivo. Four aquaporins were expressed in wild-type heart tissue (AQP1, AQP7, AQP4, AQP8) and two aquaporins in aortic and mesenteric vessels (AQP1-AQP7). AQP1 was expressed in endothelial as well as cardiac and vascular muscle cells and co-segregated with caveolin-1. AQP1 knockout (KO) mice exhibited a prominent microcardia and decreased myocyte transverse dimensions despite no change in capillary density. Both male and female AQP1 KO mice had lower mean BP, which was not attributable to altered water balance or autonomic dysfunction (from baroreflex and frequency analysis of BP and HR variability). NO-dependent BP variability was unperturbed. Accordingly, endothelium-derived hyperpolarizing factor (EDH(F)) or NO-dependent relaxation were unchanged in aorta or resistance vessels ex vivo. However, AQP1 KO mesenteric vessels exhibited an increase in endothelial prostanoids-dependent relaxation, together with increased expression of COX-2. This enhanced relaxation was abrogated by COX inhibition. We conclude that AQP1 does not regulate the endothelial EDH or NO-dependent relaxation ex vivo or in vivo, but its deletion decreases baseline BP together with increased prostanoids-dependent relaxation in resistance vessels. Strikingly, this was associated with microcardia, unrelated to perturbed angiogenesis. This may raise interest for new inhibitors of AQP1 and their use to treat hypertrophic cardiac remodeling.
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Chu YH, Hsu YJ, Lee HS, Ho ST, Tung CS, Tseng CJ, Li MH, Lin TC, Lu CC. The Osmopressor Response Is Linked to Upregulation of Aquaporin-1 Tyrosine Phosphorylation on Red Blood Cell Membranes. Hypertension 2013; 62:197-202. [DOI: 10.1161/hypertensionaha.111.200147] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Studies in patients with an impaired efferent baroreflex led us to discover that ingesting water induces a robust increase in blood pressure and vascular resistance. This response was also present in healthy subjects with intact baroreflexes, described as osmopressor response. This study was to discover the physiology of the osmopressor response by determining functional activation of the aquaporin-1 water channel receptor on red blood cell membranes in young healthy subjects. In a randomized, controlled, crossover fashion, 22 young healthy subjects (age, 19–27 years) ingested either 500 or 50 mL of water. Heart rate, blood pressure, cardiac index, and total peripheral vascular resistance were measured using a Finometer hemodynamic monitor. Blood sampling was performed at 5 minutes before and at 25 and 50 minutes after either the water ingestion or control session. Immunoblotting for aquaporin-1 tyrosine phosphorylation was performed before and after subjects ingested either 500 or 50 mL of water. At 25 minutes after the ingestion of 500 mL of water, total peripheral resistance increased significantly, and plasma osmolality decreased. Functional expression of aquaporin-1 tyrosine phosphorylation on red blood cell membranes increased significantly at 25 and 50 minutes after subjects ingested 500 mL of water compared with that before water ingestion. This study concludes that water ingestion produces upregulation of aquaporin-1 tyrosine phosphorylation on red blood cell, which presents as a novel biological marker that occurs simultaneously with the osmopressor response.
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Affiliation(s)
- You Hsiang Chu
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Yu-Juei Hsu
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Herng Sheng Lee
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Shung-Tai Ho
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Che-Se Tung
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Ching-Jiunn Tseng
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Min-Hui Li
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Tso-Chou Lin
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
| | - Chih-Cherng Lu
- From the Institute of Aerospace Medicine (M.-H.L.), Department of Anesthesiology (C.-C.L., T.-C.L.), Physiology (C.-S.T.), Pathology (H.S.L.), Nephrology of Internal Medicine (Y.-J.H.) of Tri-Service General Hospital, Taipei, Taiwan; Graduate Institute of Life Sciences (Y.H.C.), National Defense Medical Center, Taipei, Taiwan; Department of Anesthesiology (S.-T.H., C.-C.L), Taipei Veterans General Hospital, Taipei, Taiwan; and Medical Education and Research, Kaohsiung Veterans General Hospital,
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Yool AJ, Morelle J, Cnops Y, Verbavatz JM, Campbell EM, Beckett EAH, Booker GW, Flynn G, Devuyst O. AqF026 is a pharmacologic agonist of the water channel aquaporin-1. J Am Soc Nephrol 2013; 24:1045-52. [PMID: 23744886 DOI: 10.1681/asn.2012080869] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Aquaporin-1 (AQP1) facilitates the osmotic transport of water across the capillary endothelium, among other cell types, and thereby has a substantial role in ultrafiltration during peritoneal dialysis. At present, pharmacologic agents that enhance AQP1-mediated water transport, which would be expected to increase the efficiency of peritoneal dialysis, are not available. Here, we describe AqF026, an aquaporin agonist that is a chemical derivative of the arylsulfonamide compound furosemide. In the Xenopus laevis oocyte system, extracellular AqF026 potentiated the channel activity of human AQP1 by >20% but had no effect on channel activity of AQP4. We found that the intracellular binding site for AQP1 involves loop D, a region associated with channel gating. In a mouse model of peritoneal dialysis, AqF026 enhanced the osmotic transport of water across the peritoneal membrane but did not affect the osmotic gradient, the transport of small solutes, or the localization and expression of AQP1 on the plasma membrane. Furthermore, AqF026 did not potentiate water transport in Aqp1-null mice, suggesting that indirect mechanisms involving other channels or transporters were unlikely. Last, in a mouse gastric antrum preparation, AqF026 did not affect the Na-K-Cl cotransporter NKCC1. In summary, AqF026 directly and specifically potentiates AQP1-mediated water transport, suggesting that it deserves additional investigation for applications such as peritoneal dialysis or clinical situations associated with defective water handling.
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Affiliation(s)
- Andrea J Yool
- School of Medical Sciences and the Adelaide Centre for Neuroscience Research, University of Adelaide, Adelaide, South Australia, Australia.
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Yool AJ, Campbell EM. Structure, function and translational relevance of aquaporin dual water and ion channels. Mol Aspects Med 2012; 33:553-61. [PMID: 22342689 DOI: 10.1016/j.mam.2012.02.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 01/31/2012] [Accepted: 02/02/2012] [Indexed: 12/29/2022]
Abstract
Aquaporins have been assumed to be selective for water alone, and aquaglyceroporins are accepted as carrying water and small uncharged solutes including glycerol. This review presents an expanded view of aquaporins as channels with more complex mechanisms of regulation and diverse repertoires of substrate permeabilities than were originally appreciated in the early establishment of the field. The role of aquaporins as dual water and gated ion channels is likely to have physiological and potentially translational relevance, and can be evaluated with newly developed molecular and pharmacological tools. Ion channel activity has been shown for Aquaporins -0, -1, and -6, Drosphila Big Brain, and plant Nodulin-26. Although the concept of ion channel function in aquaporins remains controversial, research advances are beginning to define not only the ion channel function but also the detailed molecular mechanisms that govern and mediate the multifunctional capabilities. With regard to physiological relevance, the adaptive benefit of expression of ion channel activity in aquaporins, implied by amino acid sequence conservation of the ion channel gating domains, suggests they provide more than water or glycerol and solute transport. Dual ion and water channels are of interest for understanding the modulation of transmembrane fluid gradients, volume regulation, and possible signal transduction in tissues expressing classes of aquaporins that have the dual function capability. Other aquaporin classes might be found in future work to have ion channel activities, pending identification of the possible signaling pathways that could govern activation.
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Affiliation(s)
- Andrea J Yool
- School of Medical Sciences and The Adelaide Centre for Neuroscience Research, Medical School South, Frome Road, University of Adelaide, Adelaide, SA 5005, Australia.
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