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Mom R, Mocquet V, Auguin D, Réty S. Aquaporin Modulation by Cations, a Review. Curr Issues Mol Biol 2024; 46:7955-7975. [PMID: 39194687 DOI: 10.3390/cimb46080470] [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: 07/05/2024] [Revised: 07/18/2024] [Accepted: 07/22/2024] [Indexed: 08/29/2024] Open
Abstract
Aquaporins (AQPs) are transmembrane channels initially discovered for their role in water flux facilitation through biological membranes. Over the years, a much more complex and subtle picture of these channels appeared, highlighting many other solutes accommodated by AQPs and a dense regulatory network finely tuning cell membranes' water permeability. At the intersection between several transduction pathways (e.g., cell volume regulation, calcium signaling, potassium cycling, etc.), this wide and ancient protein family is considered an important therapeutic target for cancer treatment and many other pathophysiologies. However, a precise and isoform-specific modulation of these channels function is still challenging. Among the modulators of AQPs functions, cations have been shown to play a significant contribution, starting with mercury being historically associated with the inhibition of AQPs since their discovery. While the comprehension of AQPs modulation by cations has improved, a unifying molecular mechanism integrating all current knowledge is still lacking. In an effort to extract general trends, we reviewed all known modulations of AQPs by cations to capture a first glimpse of this regulatory network. We paid particular attention to the associated molecular mechanisms and pinpointed the residues involved in cation binding and in conformational changes tied up to the modulation of the channel function.
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Affiliation(s)
- Robin Mom
- Laboratoire de Biologie et Modelisation de la Cellule, Ecole Normale Superieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Universite Claude Bernard Lyon 1, 46 allee d'Italie, F-69364 Lyon, France
| | - Vincent Mocquet
- Laboratoire de Biologie et Modelisation de la Cellule, Ecole Normale Superieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Universite Claude Bernard Lyon 1, 46 allee d'Italie, F-69364 Lyon, France
| | - Daniel Auguin
- Laboratoire de Physiologie, Ecologie et Environnement (P2E), UPRES EA 1207/USC INRAE-1328, UFR Sciences et Techniques, Université d'Orléans, F-45067 Orléans, France
| | - Stéphane Réty
- Laboratoire de Biologie et Modelisation de la Cellule, Ecole Normale Superieure de Lyon, CNRS, UMR 5239, Inserm, U1293, Universite Claude Bernard Lyon 1, 46 allee d'Italie, F-69364 Lyon, France
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Fischbarg J, Hernandez JA, Rubashkin AA, Iserovich P, Cacace VI, Kusnier CF. Epithelial Fluid Transport is Due to Electro-osmosis (80%), Plus Osmosis (20%). J Membr Biol 2017. [PMID: 28623474 PMCID: PMC5489618 DOI: 10.1007/s00232-017-9966-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Epithelial fluid transport, an important physiological process shrouded in a long-standing enigma, may finally be moving closer to a solution. We propose that, for the corneal endothelium, relative proportions for the driving forces for fluid transport are 80% of paracellular electro-osmosis, and 20% classical transcellular osmosis. These operate in a cyclical process with a period of 9.2 s, which is dictated by the decrease and exhaustion of cellular Na+. Paracellular electro-osmosis is sketched here, and partially discussed as much as the subject still allows; transcellular osmosis is presented at length.
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Affiliation(s)
- Jorge Fischbarg
- Ininca, Conicet, Univ. of Buenos Aires2, Buenos Aires, Argentina.
| | - Julio A Hernandez
- Biophysics Section, Science Faculty, Univ. of the Republic, Montevideo, Uruguay
| | - Andrey A Rubashkin
- Institute of Cytology of the Russian Academy of Science, St. Petersburg, Russia
| | | | | | - Carlos F Kusnier
- Ininca, Conicet, Univ. of Buenos Aires2, Buenos Aires, Argentina
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Mercury inhibits the L170C mutant of aquaporin Z by making waters clog the water channel. Biophys Chem 2011; 160:69-74. [PMID: 21963041 DOI: 10.1016/j.bpc.2011.07.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 07/14/2011] [Accepted: 07/25/2011] [Indexed: 11/22/2022]
Abstract
We conduct in silico experiments of the L170C mutant of the Escherichia coli aquaporin Z (AQPZ) with and without mercury bonded to residue Cys 170. We find that bonding mercury to Cys 170 does not induce consequential structural changes to the protein. We further find that mercury does not stick in the middle of the water channel to simply occlude water permeation, but resides on the wall of the water pore. However, we observe that the water permeation coefficient of L170C-Hg(+) (with one mercury ion bonded to Cys 170) is approximately half of that of the mercury-free L170C. We examine the interactions between the mercury ion and the waters in its vicinity and find that five to six waters are strongly attracted by the mercury ion, occluding the space of the water channel. Therefore we conclude that mercury, at low concentration, inhibits AQPZ-L170C mutant by making water molecules clog the water channel.
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Mathew LG, Campbell EM, Yool AJ, Fabrick JA. Identification and characterization of functional aquaporin water channel protein from alimentary tract of whitefly, Bemisia tabaci. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2011; 41:178-190. [PMID: 21146609 DOI: 10.1016/j.ibmb.2010.12.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 11/03/2010] [Accepted: 12/02/2010] [Indexed: 05/30/2023]
Abstract
Some hemipteran xylem and phloem-feeding insects have evolved specialized alimentary structures or filter chambers that rapidly transport water for excretion or osmoregulation. In the whitefly, Bemisia tabaci, mass movement of water through opposing alimentary tract tissues within the filter chamber is likely facilitated by an aquaporin protein. B. tabaci aquaporin-1 (BtAQP1) possesses characteristic aquaporin topology and conserved pore-forming residues found in water-specific aquaporins. As predicted for an integral transmembrane protein, recombinant BtAQP1 expressed in cultured insect cells localized within the plasma membrane. BtAQP1 is primarily expressed in early instar nymphs and adults, where in adults it is localized in the filter chamber and hindgut. Xenopus oocytes expressing BtAQP1 were water permeable and mercury-sensitive, both characteristics of classical water-specific aquaporins. These data support the hypothesis that BtAQP1 is a water transport protein within the specialized filter chamber of the alimentary tract and functions to translocate water across tissues for maintenance of osmotic pressure and/or excretion of excess dietary fluid.
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Affiliation(s)
- Lolita G Mathew
- USDA-ARS, U.S. Arid Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85138, USA
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Jacobsen Ø, Klaveness J, Petter Ottersen O, Reza Amiry-Moghaddam M, Rongved P. Synthesis of cyclic peptide analogues of the 310 helical Pro138-Gly144 segment of human aquaporin-4 by olefin metathesis. Org Biomol Chem 2009; 7:1599-611. [DOI: 10.1039/b823559g] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Starodubtseva MN, Tattersall AL, Kuznetsova TG, Yegorenkov NI, Ellory JC. Structural and functional changes in the membrane and membrane skeleton of red blood cells induced by peroxynitrite. Bioelectrochemistry 2008; 73:155-62. [DOI: 10.1016/j.bioelechem.2008.01.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 12/16/2007] [Accepted: 01/17/2008] [Indexed: 12/15/2022]
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Savage DF, Stroud RM. Structural basis of aquaporin inhibition by mercury. J Mol Biol 2007; 368:607-17. [PMID: 17376483 PMCID: PMC3535476 DOI: 10.1016/j.jmb.2007.02.070] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2006] [Revised: 02/19/2007] [Accepted: 02/20/2007] [Indexed: 11/28/2022]
Abstract
The aquaporin family of channels was defined based on the inhibition of water transport by mercurial compounds. Despite the important role of mercurials, little is known about the structural changes involved upon mercury binding leading to channel inhibition. To elucidate the mechanism we designed a mutant, T183C, of aquaporin Z (AqpZ) patterned after the known mercury-sensitive site of aquaporin 1 (AQP1) and determined the X-ray crystal structures of the unbound and mercury blocked states. Superposition of the two structures shows no conformational rearrangement upon mercury binding. In the blocked structure, there are two mercury sites, one bound to Cys183 and occluding the pore, and a second, also bound to the same cysteine but found buried in an interstitial cavity. To test the mechanism of blockade we designed a different mutant, L170C, to produce a more effective mercury block at the pore site. In a dose-response inhibition study, this mutant was 20 times more sensitive to mercury than wild-type AqpZ and four times more sensitive than T183C. The X-ray structure of L170C shows four mercury atoms at, or near, the pore site defined in the T183C structure and no structural change upon mercury binding. Thus, we elucidate a steric inhibition mechanism for this important class of channels by mercury.
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Affiliation(s)
- David F Savage
- Graduate Group in Biophysics, University of California at San Francisco, San Francisco, CA 94158, USA.
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Weber GJ, Mehr AP, Sirota JC, Aller SG, Decker SE, Dawson DC, Forrest JN. Mercury and zinc differentially inhibit shark and human CFTR orthologues: involvement of shark cysteine 102. Am J Physiol Cell Physiol 2005; 290:C793-801. [PMID: 16236827 DOI: 10.1152/ajpcell.00203.2005] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The apical membrane is an important site of mercury toxicity in shark rectal gland tubular cells. We compared the effects of mercury and other thiol-reacting agents on shark CFTR (sCFTR) and human CFTR (hCFTR) chloride channels using two-electrode voltage clamping of cRNA microinjected Xenopus laevis oocytes. Chloride conductance was stimulated by perfusing with 10 microM forskolin (FOR) and 1 mM IBMX, and then thio-reactive species were added. In oocytes expressing sCFTR, FOR + IBMX mean stimulated Cl(-) conductance was inhibited 69% by 1 microM mercuric chloride and 78% by 5 microM mercuric chloride (IC(50) of 0.8 microM). Despite comparable stimulation of conductance, hCFTR was insensitive to 1 microM HgCl(2) and maximum inhibition was 15% at the highest concentration used (5 microM). Subsequent exposure to glutathione (GSH) did not reverse the inhibition of sCFTR by mercury, but dithiothreitol (DTT) completely reversed this inhibition. Zinc (50-200 microM) also reversibly inhibited sCFTR (40-75%) but did not significantly inhibit hCFTR. Similar inhibition of sCFTR but not hCFTR was observed with an organic mercurial, p-chloromercuriphenylsulfonic acid (pCMBS). The first membrane spanning domain (MSD1) of sCFTR contains two unique cysteines, C102 and C303. A chimeric construct replacing MSD1 of hCFTR with the corresponding sequence of sCFTR was highly sensitive to mercury. Site-specific mutations introducing the first but not the second shark unique cysteine in hCFTR MSD1 resulted in full sensitivity to mercury. These experiments demonstrate a profound difference in the sensitivity of shark vs. human CFTR to inhibition by three thiol-reactive substances, an effect that involves C102 in the shark orthologue.
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Affiliation(s)
- Gerhard J Weber
- Division of Nephrology, Department of Internal Medicine, Yale Univ. School of Medicine, New Haven, CT 06510, USA
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Abstract
Molecular-dynamics simulations were performed on the structures of the water channel aquaporin-1. The results provide an atomistic description of the interactions involved in the water permeation. Two major curvilinear pathways were identified. The simulations confirmed that the water selectivity is due primarily to the size-exclusion effect; i.e., maximally, one water molecule is allowed to pass through the narrow constriction in the aqueous pathway. Most importantly, in contrast to previous proposals, the hydrogen-bonding interactions of water molecules with the polar side chains of Asn-76 and Asn-192 on the strictly conserved Asn-Pro-Ala sequence motifs were found to be essential for maintaining the connectivity of water flow in the narrow constriction region. When Asn-76 and Asn-192 were replaced with near-isosteric hydrophobic residues in the simulation, the aqueous pathways were broken completely. Additionally, the size of the narrow constriction fluctuates significantly during the simulation, which frequently breaks the flow of water and, thus, breaks the single-file water network necessary for proton translocation. Moreover, mutations based on the simulation also have been suggested for further experimental investigation of the water-permeation mechanism of aquaporin-1.
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Affiliation(s)
- Y Kong
- Graduate Program of Structural and Computational Biology and Molecular Biophysics, , Baylor College of Medicine, One Baylor Plaza, BCM-125, Houston, TX 77030, USA
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