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Melnyk S, Bollag WB. Aquaporins in the Cornea. Int J Mol Sci 2024; 25:3748. [PMID: 38612559 PMCID: PMC11011575 DOI: 10.3390/ijms25073748] [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: 02/20/2024] [Revised: 03/18/2024] [Accepted: 03/21/2024] [Indexed: 04/14/2024] Open
Abstract
The cornea is an avascular, transparent tissue that allows light to enter the visual system. Accurate vision requires proper maintenance of the cornea's integrity and structure. Due to its exposure to the external environment, the cornea is prone to injury and must undergo proper wound healing to restore vision. Aquaporins (AQPs) are a family of water channels important for passive water transport and, in some family members, the transport of other small molecules; AQPs are expressed in all layers of the cornea. Although their functions as water channels are well established, the direct function of AQPs in the cornea is still being determined and is the focus of this review. AQPs, primarily AQP1, AQP3, and AQP5, have been found to play an important role in maintaining water homeostasis, the corneal structure in relation to proper hydration, and stress responses, as well as wound healing in all layers of the cornea. Due to their many functions in the cornea, the identification of drug targets that modulate the expression of AQPs in the cornea could be beneficial to promote corneal wound healing and restore proper function of this tissue crucial for vision.
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Affiliation(s)
- Samuel Melnyk
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA;
| | - Wendy B. Bollag
- Department of Physiology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA;
- Charlie Norwood Department of Veterans Affairs Medical Center, Augusta, GA 30904, USA
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2
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Bill RM. Drugging aquaporins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184164. [PMID: 37146744 DOI: 10.1016/j.bbamem.2023.184164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 04/19/2023] [Accepted: 04/27/2023] [Indexed: 05/07/2023]
Abstract
Water is essential for all life because it is required for the proper functioning of the cells and tissues of all organisms. It crosses biological membranes down osmotic gradients through the pores of aquaporin membrane channels at rates of up to 3 billion molecules per second. In the twenty years since Peter Agre was awarded the 2003 Nobel Prize in Chemistry for the discovery of the aquaporin family, aquaporin structure and function have become established in the literature. As a consequence, we understand in fine detail the mechanism by which aquaporins facilitate membrane water flow while excluding protons. We also know that some aquaporins facilitate the permeation of other small neutral solutes, ions or even unexpected substrates across biological membranes. The thirteen aquaporins in the human body have been implicated in pathologies including oedema, epilepsy, cancer cell migration, tumour angiogenesis, metabolic disorders and inflammation. Surprisingly, however, there is no aquaporin-targeted drug in the clinic. Some scientists have therefore concluded that aquaporins are intrinsically non-druggable targets. Discovering medicines to treat disorders of water homeostasis is thus an enduring challenge for the aquaporin field. Success in this endeavour will meet the urgent clinical need of millions of patients suffering from a range of life-threatening conditions and for whom no pharmacological interventions are currently available.
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Affiliation(s)
- Roslyn M Bill
- College of Health and Life Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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3
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Hellas JA, Andrew RD. Neuronal Swelling: A Non-osmotic Consequence of Spreading Depolarization. Neurocrit Care 2021; 35:112-134. [PMID: 34498208 PMCID: PMC8536653 DOI: 10.1007/s12028-021-01326-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 08/04/2021] [Indexed: 01/22/2023]
Abstract
An acute reduction in plasma osmolality causes rapid uptake of water by astrocytes but not by neurons, whereas both cell types swell as a consequence of lost blood flow (ischemia). Either hypoosmolality or ischemia can displace the brain downwards, potentially causing death. However, these disorders are fundamentally different at the cellular level. Astrocytes osmotically swell or shrink because they express functional water channels (aquaporins), whereas neurons lack functional aquaporins and thus maintain their volume. Yet both neurons and astrocytes immediately swell when blood flow to the brain is compromised (cytotoxic edema) as following stroke onset, sudden cardiac arrest, or traumatic brain injury. In each situation, neuronal swelling is the direct result of spreading depolarization (SD) generated when the ATP-dependent sodium/potassium ATPase (the Na+/K+ pump) is compromised. The simple, and incorrect, textbook explanation for neuronal swelling is that increased Na+ influx passively draws Cl- into the cell, with water following by osmosis via some unknown conduit. We first review the strong evidence that mammalian neurons resist volume change during acute osmotic stress. We then contrast this with their dramatic swelling during ischemia. Counter-intuitively, recent research argues that ischemic swelling of neurons is non-osmotic, involving ion/water cotransporters as well as at least one known amino acid water pump. While incompletely understood, these mechanisms argue against the dogma that neuronal swelling involves water uptake driven by an osmotic gradient with aquaporins as the conduit. Promoting clinical recovery from neuronal cytotoxic edema evoked by spreading depolarizations requires a far better understanding of molecular water pumps and ion/water cotransporters that act to rebalance water shifts during brain ischemia.
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Affiliation(s)
- Julia A Hellas
- Center for Neuroscience Studies, Queen's University, Kingston, ON, K7L 3N6, Canada.
| | - R David Andrew
- Center for Neuroscience Studies, Queen's University, Kingston, ON, K7L 3N6, Canada
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Aquaporin-3 regulates endosome-to-cytosol transfer via lipid peroxidation for cross presentation. PLoS One 2020; 15:e0238484. [PMID: 33232321 PMCID: PMC7685505 DOI: 10.1371/journal.pone.0238484] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/03/2020] [Indexed: 01/23/2023] Open
Abstract
Antigen cross presentation, whereby exogenous antigens are presented by MHC class I molecules to CD8+ T cells, is essential for generating adaptive immunity to pathogens and tumor cells. Following endocytosis, it is widely understood that protein antigens must be transferred from endosomes to the cytosol where they are subject to ubiquitination and proteasome degradation prior to being translocated into the endoplasmic reticulum (ER), or possibly endosomes, via the TAP1/TAP2 complex. Revealing how antigens egress from endocytic organelles (endosome-to-cytosol transfer, ECT), however, has proved vexing. Here, we used two independent screens to identify the hydrogen peroxide-transporting channel aquaporin-3 (AQP3) as a regulator of ECT. AQP3 overexpression increased ECT, whereas AQP3 knockout or knockdown decreased ECT. Mechanistically, AQP3 appears to be important for hydrogen peroxide entry into the endosomal lumen where it affects lipid peroxidation and subsequent antigen release. AQP3-mediated regulation of ECT was functionally significant, as AQP3 modulation had a direct impact on the efficiency of antigen cross presentation in vitro. Finally, AQP3-/- mice exhibited a reduced ability to mount an anti-viral response and cross present exogenous extended peptide. Together, these results indicate that the AQP3-mediated transport of hydrogen peroxide can regulate endosomal lipid peroxidation and suggest that compromised membrane integrity and coordinated release of endosomal cargo is a likely mechanism for ECT.
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Nabeel F, Rasheed T, Bilal M, Li C, Yu C, Iqbal HMN. Bio-Inspired Supramolecular Membranes: A Pathway to Separation and Purification of Emerging Pollutants. SEPARATION & PURIFICATION REVIEWS 2020; 49:20-36. [DOI: 10.1080/15422119.2018.1500919] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 06/30/2018] [Indexed: 02/08/2023]
Affiliation(s)
- Faran Nabeel
- The School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Tahir Rasheed
- The School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Muhammad Bilal
- School of Life Science and Food Engineering, Huaiyin Institute of Technology, Huaian, China
| | - Chuanlong Li
- The School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Chunyang Yu
- The School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, China
| | - Hafiz M. N. Iqbal
- Tecnologico de Monterrey, School of Engineering and Sciences, Monterrey, Mexico
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Kepner G. Osmotic and diffusive flows in single-file pores: new approach to modeling pore occupancy states. Theor Biol Med Model 2018; 15:15. [PMID: 30269687 PMCID: PMC6166291 DOI: 10.1186/s12976-018-0087-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 08/01/2018] [Indexed: 11/29/2022] Open
Abstract
Background The relation between osmotic permeability, Pf, diffusion permeability, Pd, and the number of water molecules, Np, in the single-file membrane pore remains an open question. Theoretical analyses, empirical studies on aquaporins and nanotubes, and molecular dynamics simulations have yet to provide a consensus view. Results This paper presents a new combinatorial analysis of the different pore states formed from water molecules and the presence of a vacancy that differs from the several previous combinatorial approaches to analyzing pore states. It is the first such analysis to show that Pf / Pd = Np. It is rooted in the concept of different classes of pore occupancy states, tracer states and tracer exit states, present in the pore. This includes pores with and without a single vacancy. The concepts of knock-on collisions and concerted Brownian fluctuations provide the mechanisms underlying the behaviors of the tracer and vacancy as each moves through the pore during osmotic or diffusive flow. It develops the important role of the knock-on collision mechanism for osmotic flow. An essential feature of the model is the presence, or absence, of a single vacancy in the pore. The vacancy slows down tracer translocation through the pore. Its absence facilitates osmotic flow. Conclusions The full pore states and the single vacancy states together with the knock-on and Brownian mechanisms account for the relative values of Pf and Pd during osmotic and diffusive flow through the single-file pore. The new approach to combinatorial analysis differs from previous approaches and is the first to show a simple intuitive basis for the relation Pf / Pd = Np. This resolves a long persisting dichotomy.
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Affiliation(s)
- Gordon Kepner
- Membrane Studies Project, P.O. Box 13160, Minneapolis, MN, USA.
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Yeste M, Morató R, Rodríguez-Gil JE, Bonet S, Prieto-Martínez N. Aquaporins in the male reproductive tract and sperm: Functional implications and cryobiology. Reprod Domest Anim 2017; 52 Suppl 4:12-27. [DOI: 10.1111/rda.13082] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- M Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm); Unit of Cell Biology; Department of Biology; Institute of Food and Agricultural Technology; Faculty of Sciences; University of Girona; Girona Spain
| | - R Morató
- Biotechnology of Animal and Human Reproduction (TechnoSperm); Unit of Cell Biology; Department of Biology; Institute of Food and Agricultural Technology; Faculty of Sciences; University of Girona; Girona Spain
- Unit of Animal Reproduction; Department of Animal Medicine and Surgery; Faculty of Veterinary Medicine; Autonomous University of Barcelona; Bellaterra (Cerdanyola del Vallès) Barcelona Spain
| | - JE Rodríguez-Gil
- Unit of Animal Reproduction; Department of Animal Medicine and Surgery; Faculty of Veterinary Medicine; Autonomous University of Barcelona; Bellaterra (Cerdanyola del Vallès) Barcelona Spain
| | - S Bonet
- Biotechnology of Animal and Human Reproduction (TechnoSperm); Unit of Cell Biology; Department of Biology; Institute of Food and Agricultural Technology; Faculty of Sciences; University of Girona; Girona Spain
| | - N Prieto-Martínez
- Biotechnology of Animal and Human Reproduction (TechnoSperm); Unit of Cell Biology; Department of Biology; Institute of Food and Agricultural Technology; Faculty of Sciences; University of Girona; Girona Spain
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Wawrzkiewicz-Jałowiecka A, Kowalczyk K, Pluta D, Blukacz Ł, Madej P. The role of aquaporins in polycystic ovary syndrome - A way towards a novel drug target in PCOS. Med Hypotheses 2017; 102:23-27. [PMID: 28478824 DOI: 10.1016/j.mehy.2017.03.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/05/2017] [Indexed: 11/25/2022]
Abstract
Aquaporins (AQPs) are transmembrane proteins, able to transport water (and in some cases also small solutes, e. g. glycerol) through the cell membrane. There are twelve types of aquaporins (AQP1-AQP12) expressed in mammalian reproductive systems. According to literature, many diseases of the reproductive organs are correlated with changes of AQPs expression and their malfunction. That is the case in the polycystic ovary syndrome (PCOS), where dysfunctions of AQPs 7-9 and alterations in its levels occur. In this work, we postulate how AQPs are involved in PCOS-related disorders, in order to emphasize their potential therapeutic meaning as a drug target. Our research allows for a surprising inference, that genetic mutation causing malfunction and/or decreased expression of aquaporins, may be incorporated in the popular insulin-dependent hypothesis of PCOS pathogenesis. What is more, changes in AQP's expression may affect the folliculogenesis and follicular atresia in PCOS.
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Affiliation(s)
- Agata Wawrzkiewicz-Jałowiecka
- Department of Physical Chemistry and Technology of Polymers, Faculty of Chemistry, Silesian University of Technology, 44-100 Gliwice, Ks. M. Strzody 9, Poland.
| | - Karolina Kowalczyk
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Dagmara Pluta
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Łukasz Blukacz
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
| | - Paweł Madej
- Department of Gynecological Endocrinology, Medical Faculty in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
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Pavlin T, Nagelhus EA, Brekken C, Eyjolfsson EM, Thoren A, Haraldseth O, Sonnewald U, Ottersen OP, Håberg AK. Loss or Mislocalization of Aquaporin-4 Affects Diffusion Properties and Intermediary Metabolism in Gray Matter of Mice. Neurochem Res 2016; 42:77-91. [DOI: 10.1007/s11064-016-2139-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 12/02/2016] [Accepted: 12/08/2016] [Indexed: 11/27/2022]
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Tadokoro M, Suda T, Shouji T, Ohno K, Honda K, Takeuchi A, Yoshizawa M, Isoda K, Kamebuchi H, Matsui H. Transpiration of Water Molecules through Molecule-Based Porous Crystals with One-Dimensional Nanochannels. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2015. [DOI: 10.1246/bcsj.20150285] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Makoto Tadokoro
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Takahiro Suda
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Taishi Shouji
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Kazuhiro Ohno
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Kohei Honda
- Department of Physics, Graduate School of Science, Tohoku University
| | - Asuka Takeuchi
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Makoto Yoshizawa
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Kyosuke Isoda
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Hajime Kamebuchi
- Department of Chemistry, Faculty of Science, Tokyo University of Science
| | - Hiroshi Matsui
- Department of Physics, Graduate School of Science, Tohoku University
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de Souza Mecawi A, Ruginsk SG, Elias LLK, Varanda WA, Antunes‐Rodrigues J. Neuroendocrine Regulation of Hydromineral Homeostasis. Compr Physiol 2015; 5:1465-516. [DOI: 10.1002/cphy.c140031] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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12
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Grebenkov DS. Exploring diffusion across permeable barriers at high gradients. II. Localization regime. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 248:164-176. [PMID: 25266755 DOI: 10.1016/j.jmr.2014.08.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2014] [Revised: 08/27/2014] [Accepted: 08/29/2014] [Indexed: 06/03/2023]
Abstract
We present an analytical solution of the one-dimensional Bloch-Torrey equation for diffusion across multiple semi-permeable barrier. This solution generalizes the seminal work by Stoller, Happer, and Dyson, in which the non-Gaussian stretched-exponential behavior of the pulsed-gradient spin-echo (PGSE) signal was first predicted at high gradients in the so-called localization regime. We investigate how the diffusive exchange across a semi-permeable barrier modifies this asymptotic behavior, and explore the transition between the localization regime at low permeability and the Gaussian regime at high permeability. High gradients are suitable to spatially localize the contribution of the nuclei near the barrier and to enhance the sensitivity of the PGSE signal to the barrier permeability. The emergence of the localization regime for three-dimensional domains is discussed.
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Affiliation(s)
- Denis S Grebenkov
- Laboratoire de Physique de la Matière Condensée, CNRS - Ecole Polytechnique, F-91128 Palaiseau, France.
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13
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Stiebel-Kalish H, Eyal S, Steiner I. The role of aquaporin-1 in idiopathic and drug-induced intracranial hypertension. Med Hypotheses 2013; 81:1059-62. [PMID: 24169407 DOI: 10.1016/j.mehy.2013.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 09/27/2013] [Accepted: 10/04/2013] [Indexed: 10/26/2022]
Abstract
Idiopathic intracranial hypertension is a common disorder affecting mainly healthy, young, overweight women. The pathogenesis of this condition is unknown, but it has been shown to follow treatment with several compounds including corticosteroids and vitamin A derivatives. This paper will offer a novel hypothesis and insight on the pathogenesis of drug induced intracranial hypertension following a review and analysis of the literature. Both corticosteroids and vitamin A derivatives have been shown to upregulate the expression of aquaporin 1, a water channel protein. Aquaporin 1 is widely distributed in the human brain and is associated with water secretion into the subarachnoid space. Aquaporin 1 was also shown to participate in the regulation of weight. Agents used for treating idiopathic intracranial hypertension reduce aquaporin 1 expression. Based on these observations, we propose that aquaporin 1 has a pathogenetic role in drug induced idiopathic intracranial hypertension. Over expression of this gene causes increased intracranial pressure, and downregulation reduces pressure and alleviates the symptomatology and complications of idiopathic intracranial hypertension.
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Affiliation(s)
- H Stiebel-Kalish
- Department of Ophthalmology, Neuro-Ophthalmology Unit, Rabin Medical Center, Petach Tikva 49100, Israel; Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel.
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Molecular dynamics of water in the neighborhood of aquaporins. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2012; 42:223-39. [DOI: 10.1007/s00249-012-0880-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 12/04/2012] [Accepted: 12/11/2012] [Indexed: 12/19/2022]
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15
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Alleva K, Chara O, Amodeo G. Aquaporins: another piece in the osmotic puzzle. FEBS Lett 2012; 586:2991-9. [PMID: 22728434 DOI: 10.1016/j.febslet.2012.06.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 06/04/2012] [Accepted: 06/06/2012] [Indexed: 01/15/2023]
Abstract
Osmolarity not only plays a key role in cellular homeostasis but also challenges cell survival. The molecular understanding of osmosis has not yet been completely achieved, and the discovery of aquaporins as molecular entities involved in water transport has caused osmosis to again become a focus of research. The main questions that need to be answered are the mechanism underlying the osmotic permeability coefficients and the extent to which aquaporins change our understanding of osmosis. Here, attempts to answer these questions are discussed. Critical aspects of the state of the state of knowledge on osmosis, a topic that has been studied since 19th century, are reviewed and integrated with the available information provided by in vivo, in vitro and in silico approaches.
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Affiliation(s)
- Karina Alleva
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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16
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Abstract
Water molecules confined to pores with sub-nanometre diameters form single-file hydrogen-bonded chains. In such nanoscale confinement, water has unusual physical properties that are exploited in biology and hold promise for a wide range of biomimetic and nanotechnological applications. The latter can be realized by carbon and boron nitride nanotubes which confine water in a relatively non-specific way and lend themselves to the study of intrinsic properties of single-file water. As a consequence of strong water-water hydrogen bonds, many characteristics of single-file water are conserved in biological and synthetic pores despite differences in their atomistic structures. Charge transport and orientational order in water chains depend sensitively on and are mainly determined by electrostatic effects. Thus, mimicking functions of biological pores with apolar pores and corresponding external fields gives insight into the structure-function relation of biological pores and allows the development of technical applications beyond the molecular devices found in living systems. In this Perspective, we revisit results for single-file water in apolar pores, and examine the similarities and the differences between these simple systems and water in more complex pores.
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Affiliation(s)
- Jürgen Köfinger
- Laboratory of Chemical Physics, Bldg. 5, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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Ozu M, Dorr RA, Teresa Politi M, Parisi M, Toriano R. Water flux through human aquaporin 1: inhibition by intracellular furosemide and maximal response with high osmotic gradients. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2011; 40:737-46. [PMID: 21373963 DOI: 10.1007/s00249-011-0687-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2010] [Revised: 01/13/2011] [Accepted: 02/16/2011] [Indexed: 10/18/2022]
Abstract
This work studies water permeability properties of human aquaporin 1 (hAQP1) expressed in Xenopus laevis oocyte membranes, applying a technique where cellular content is replaced with a known medium, with the possibility of measuring intracellular pressure. Consequences on water transport-produced by well-known anisotonic gradients and by the intracellular effect of probable aquaporin inhibitors-were tested. In this way, the specific intracellular inhibition of hAQP1 by the diuretic drug furosemide was demonstrated. In addition, experiments imposing anisotonic mannitol gradients with a constant ionic strength showed that the relationship between water flux and the applied mannitol gradient deflects from a perfect osmometer response when the gradient is higher than 150 mosmol kg (W) (-1) . These results would indicate that the passage of water molecules through hAQP1 may have a maximum rate. As a whole, this work demonstrates the technical advantage of controlling both intracellular pressure and medium composition in order to study biophysical properties of hAQP1, and contributes information on water channel behavior under osmotic challenges and the discovery of new inhibitors.
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Affiliation(s)
- Marcelo Ozu
- Laboratorio de Biomembranas, Departamento de Fisiología y Biofísica, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, 7º Piso, C1121ABG Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina.
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18
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Chara O, Espelt MV, Krumschnabel G, Schwarzbaum PJ. Regulatory volume decrease and P receptor signaling in fish cells: mechanisms, physiology, and modeling approaches. ACTA ACUST UNITED AC 2011; 315:175-202. [PMID: 21290610 DOI: 10.1002/jez.662] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 11/30/2010] [Indexed: 11/11/2022]
Abstract
For animal cell plasma membranes, the permeability of water is much higher than that of ions and other solutes, and exposure to hyposmotic conditions almost invariably causes rapid water influx and cell swelling. In this situation, cells deploy regulatory mechanisms to preserve membrane integrity and avoid lysis. The phenomenon of regulatory volume decrease, the partial or full restoration of cell volume following cell swelling, is well-studied in mammals, with uncountable investigations yielding details on the signaling network and the effector mechanisms involved in the process. In comparison, cells from other vertebrates and from invertebrates received little attention, despite of the fact that e.g. fish cells could present rewarding model systems given the diversity in ecology and lifestyle of this animal group that may be reflected by an equal diversity of physiological adaptive mechanisms, including those related to cell volume regulation. In this review, we therefore present an overview on the most relevant aspects known on hypotonic volume regulation presently known in fish, summarizing transporters and signaling pathways described so far, and then focus on an aspect we have particularly studied over the past years using fish cell models, i.e. the role of extracellular nucleotides in mediating cell volume recovery of swollen cells. We, furthermore, present diverse modeling approaches developed on the basis of data derived from studies with fish and other models and discuss their potential use for gaining insight into the theoretical framework of volume regulation.
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Affiliation(s)
- Osvaldo Chara
- IFLYSIB (CONICET, UNLP), La Plata, Provincia de Buenos Aires, Argentina
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