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Klaczek CE, Goss GG, Glover CN. Mechanistic characterization of waterborne selenite uptake in the water flea, Daphnia magna, indicates water chemistry affects toxicity in coal mine-impacted waters. CONSERVATION PHYSIOLOGY 2024; 12:coad108. [PMID: 38293640 PMCID: PMC10823350 DOI: 10.1093/conphys/coad108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 11/20/2023] [Accepted: 12/15/2023] [Indexed: 02/01/2024]
Abstract
Concentrations of selenium that exceed regulatory guidelines have been associated with coal mining activities and have been linked to detrimental effects on aquatic ecosystems and the organisms therein. Although the major route of selenium uptake in macroinvertebrates is via the diet, the uptake of waterborne selenite (HSeO3-), the prominent form at circumneutral pH, can be an important contributor to selenium body burden and thus selenium toxicity. In the current study, radiolabelled selenite (Se75) was used to characterize the mechanism of selenite uptake in the water flea, Daphnia magna. The concentration dependence (1-32 μM) of selenite uptake was determined in 1-hour uptake assays in artificial waters that independently varied in bicarbonate, chloride, sulphate, phosphate and selenate concentrations. At concentrations representative of those found in highly contaminated waters, selenite uptake was phosphate-dependent and inhibited by foscarnet, a phosphate transport inhibitor. At higher concentrations, selenite uptake was dependent on waterborne bicarbonate concentration and inhibited by the bicarbonate transporter inhibitor DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid). These findings suggest that concentrations of phosphate in coal mining-affected waters could alter selenite uptake in aquatic organisms and could ultimately affect the toxic impacts of selenium in such waters.
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Affiliation(s)
- Chantelle E Klaczek
- Department of Biological Sciences, CW 405 Biological Sciences Bldg., University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Greg G Goss
- Department of Biological Sciences, CW 405 Biological Sciences Bldg., University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Chris N Glover
- Department of Biological Sciences, CW 405 Biological Sciences Bldg., University of Alberta, Edmonton, Alberta T6G 2E9, Canada
- Faculty of Science and Technology and Athabasca River Basin Research Institute, Athabasca University, 1 University Dr., Athabasca, Alberta T9S 3A3, Canada
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2
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Tutol J, Ong WSY, Phelps SM, Peng W, Goenawan H, Dodani SC. Engineering the ChlorON Series: Turn-On Fluorescent Protein Sensors for Imaging Labile Chloride in Living Cells. ACS CENTRAL SCIENCE 2024; 10:77-86. [PMID: 38292617 PMCID: PMC10823515 DOI: 10.1021/acscentsci.3c01088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 11/02/2023] [Accepted: 11/27/2023] [Indexed: 02/01/2024]
Abstract
Beyond its role as the "queen of electrolytes", chloride can also serve as an allosteric regulator or even a signaling ion. To illuminate this essential anion across such a spectrum of biological processes, researchers have relied on fluorescence imaging with genetically encoded sensors. In large part, these have been derived from the green fluorescent protein found in the jellyfish Aequorea victoria. However, a standalone sensor with a turn-on intensiometric response at physiological pH has yet to be reported. Here, we address this technology gap by building on our discovery of the anion-sensitive fluorescent protein mNeonGreen (mNG). The targeted engineering of two non-coordinating residues, namely K143 and R195, in the chloride binding pocket of mNG coupled with an anion walking screening and selection strategy resulted in the ChlorON sensors: ChlorON-1 (K143W/R195L), ChlorON-2 (K143R/R195I), and ChlorON-3 (K143R/R195L). In vitro spectroscopy revealed that all three sensors display a robust turn-on fluorescence response to chloride (20- to 45-fold) across a wide range of affinities (Kd ≈ 30-285 mM). We further showcase how this unique sensing mechanism can be exploited to directly image labile chloride transport with spatial and temporal resolution in a cell model overexpressing the cystic fibrosis transmembrane conductance regulator. Building from this initial demonstration, we anticipate that the ChlorON technology will have broad utility, accelerating the path forward for fundamental and translational aspects of chloride biology.
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Affiliation(s)
- Jasmine
N. Tutol
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Whitney S. Y. Ong
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Shelby M. Phelps
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Weicheng Peng
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Helen Goenawan
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Sheel C. Dodani
- Department
of Chemistry and Biochemistry and Department of Biological Sciences, The University of Texas at Dallas, Richardson, Texas 75080, United States
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3
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Cané L, Saffioti NA, Genetet S, Daza Millone MA, Ostuni MA, Schwarzbaum PJ, Mouro-Chanteloup I, Herlax V. Alpha hemolysin of E. coli induces hemolysis of human erythrocytes independently of toxin interaction with membrane proteins. Biochimie 2024; 216:3-13. [PMID: 37820991 DOI: 10.1016/j.biochi.2023.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Revised: 09/13/2023] [Accepted: 10/08/2023] [Indexed: 10/13/2023]
Abstract
Alpha hemolysin (HlyA) is a hemolytic and cytotoxic protein secreted by uropathogenic strains of E. coli. The role of glycophorins (GPs) as putative receptors for HlyA binding to red blood cells (RBCs) has been debated. Experiments using anti-GPA/GPB antibodies and a GPA-specific epitope nanobody to block HlyA-GP binding on hRBCs, showed no effect on hemolytic activity. Similarly, the hemolysis induced by HlyA remained unaffected when hRBCs from a GPAnull/GPBnull variant were used. Surface Plasmon Resonance experiments revealed similar values of the dissociation constant between GPA and either HlyA, ProHlyA (inactive protoxin), HlyAΔ914-936 (mutant of HlyA lacking the binding domain to GPA) or human serum albumin, indicating that the binding between the proteins and GPA is not specific. Although far Western blot followed by mass spectroscopy analyses suggested that HlyA interacts with Band 3 and spectrins, hemolytic experiments on spectrin-depleted hRBCs and spherocytes, indicated these proteins do not mediate the hemolytic process. Our results unequivocally demonstrate that neither glycophorins, nor Band 3 and spectrins mediate the cytotoxic activity of HlyA on hRBCs, thereby challenging the HlyA-receptor hypothesis. This finding holds significant relevance for the design of anti-toxin therapeutic strategies, particularly in light of the growing antibiotic resistance exhibited by bacteria.
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Affiliation(s)
- Lucía Cané
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata, Argentina
| | - Nicolás Andrés Saffioti
- Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Nanosistemas, Universidad de General San Martín, Avenida 25 de Mayo 1021, San Martín, Buenos Aires, Argentina
| | - Sandrine Genetet
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015, Paris, France
| | - María Antonieta Daza Millone
- Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT- La Plata, CONICET. Universidad Nacional de La Plata, Sucursal 4 Casilla de Correo 16, 1900, La Plata, Argentina
| | - Mariano A Ostuni
- Université Paris Cité and Université des Antilles, INSERM, BIGR, F-75015, Paris, France
| | - Pablo J Schwarzbaum
- Instituto de Química y Fisico-Química Biológicas (IQUIFIB) "Prof. Alejandro C. Paladini", Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina
| | | | - Vanesa Herlax
- Instituto de Investigaciones Bioquímicas de La Plata (INIBIOLP), CCT- La Plata, CONICET. Facultad de Ciencias Médicas. Universidad Nacional de La Plata, Argentina.
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4
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Phelps SM, Tutol JN, Advani D, Peng W, Dodani SC. Unlocking chloride sensing in the red at physiological pH with a fluorescent rhodopsin-based host. Chem Commun (Camb) 2023; 59:8460-8463. [PMID: 37337864 PMCID: PMC11136539 DOI: 10.1039/d3cc01786a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Chloride is a vital ion for all forms of life. Protein-based fluorescent biosensors can enable researchers to visualize chloride in cells but remain underdeveloped. Here, we demonstrate how a single point mutation in an engineered microbial rhodopsin results in ChloRED-1-CFP. This membrane-bound host is a far-red emitting, ratiometric sensor that provides a reversible readout of chloride in live bacteria at physiological pH, setting the stage to investigate the roles of chloride in diverse biological contexts.
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Affiliation(s)
- Shelby M Phelps
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX 75080, USA.
| | - Jasmine N Tutol
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX 75080, USA.
| | - Deeya Advani
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX 75080, USA.
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Weicheng Peng
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX 75080, USA.
- Department of Biological Sciences, The University of Texas at Dallas, Richardson, TX 75080, USA
| | - Sheel C Dodani
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, TX 75080, USA.
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Whittamore JM, Hatch M. Oxalate secretion is stimulated by a cAMP-dependent pathway in the mouse cecum. Pflugers Arch 2023; 475:249-266. [PMID: 36044064 PMCID: PMC9851989 DOI: 10.1007/s00424-022-02742-3] [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: 06/06/2022] [Revised: 08/06/2022] [Accepted: 08/18/2022] [Indexed: 02/01/2023]
Abstract
Elevated levels of the intracellular second messenger cAMP can stimulate intestinal oxalate secretion however the membrane transporters responsible are unclear. Oxalate transport by the chloride/bicarbonate (Cl-/HCO3-) exchanger Slc26a6 or PAT-1 (Putative Anion Transporter 1), is regulated via cAMP when expressed in Xenopus oocytes and cultured cells but whether this translates to the native epithelia is unknown. This study investigated the regulation of oxalate transport by the mouse intestine focusing on transport at the apical membrane hypothesizing PAT-1 is the target of a cAMP-dependent signaling pathway. Adopting the Ussing chamber technique we measured unidirectional 14C-oxalate and 36Cl- flux ([Formula: see text] and [Formula: see text]) across distal ileum, cecum and distal colon, employing forskolin (FSK) and 3-isobutyl-1-methylxanthine (IBMX) to trigger cAMP production. FSK/IBMX initiated a robust secretory response by all segments but the stimulation of net oxalate secretion was confined to the cecum only involving activation of [Formula: see text] and distinct from net Cl- secretion produced by inhibiting [Formula: see text]. Using the PAT-1 knockout (KO) mouse we determined cAMP-stimulated [Formula: see text] was not directly dependent on PAT-1, but it was sensitive to mucosal DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid), although unlikely to be another Cl-/HCO3- exchanger given the lack of trans-stimulation or cis-inhibition by luminal Cl- or HCO3-. The cAMP-activated oxalate efflux was reliant on CFTR (Cystic Fibrosis Transmembrane conductance Regulator) activity, but only in the presence of PAT-1, leading to speculation on the involvement of a multi-transporter regulatory complex. Further investigations at the cellular and molecular level are necessary to define the mechanism and transporter(s) responsible.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA.
- Charles and Jane Pak Center for Mineral Metabolism and Clinical Research | Internal Medicine, UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390-8885, USA.
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, FL, USA
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6
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Whittamore JM, Hatch M. Oxalate Flux Across the Intestine: Contributions from Membrane Transporters. Compr Physiol 2021; 12:2835-2875. [PMID: 34964122 DOI: 10.1002/cphy.c210013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epithelial oxalate transport is fundamental to the role occupied by the gastrointestinal (GI) tract in oxalate homeostasis. The absorption of dietary oxalate, together with its secretion into the intestine, and degradation by the gut microbiota, can all influence the excretion of this nonfunctional terminal metabolite in the urine. Knowledge of the transport mechanisms is relevant to understanding the pathophysiology of hyperoxaluria, a risk factor in kidney stone formation, for which the intestine also offers a potential means of treatment. The following discussion presents an expansive review of intestinal oxalate transport. We begin with an overview of the fate of oxalate, focusing on the sources, rates, and locations of absorption and secretion along the GI tract. We then consider the mechanisms and pathways of transport across the epithelial barrier, discussing the transcellular, and paracellular components. There is an emphasis on the membrane-bound anion transporters, in particular, those belonging to the large multifunctional Slc26 gene family, many of which are expressed throughout the GI tract, and we summarize what is currently known about their participation in oxalate transport. In the final section, we examine the physiological stimuli proposed to be involved in regulating some of these pathways, encompassing intestinal adaptations in response to chronic kidney disease, metabolic acid-base disorders, obesity, and following gastric bypass surgery. There is also an update on research into the probiotic, Oxalobacter formigenes, and the basis of its unique interaction with the gut epithelium. © 2021 American Physiological Society. Compr Physiol 11:1-41, 2021.
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Affiliation(s)
- Jonathan M Whittamore
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
| | - Marguerite Hatch
- Department of Pathology, Immunology and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, Florida, USA
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7
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McComic SE, Rault LC, Anderson TD, Swale DR. Toxicological analysis of stilbenes against the fall armyworm, Spodoptera frugiperda. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2021; 179:104965. [PMID: 34802515 DOI: 10.1016/j.pestbp.2021.104965] [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: 06/09/2021] [Revised: 08/17/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
The fall armyworm (FAW), Spodoptera frugiperda, is a global pest of multiple economically important row crops and the development of resistance to commercially available insecticidal classes has inhibited FAW control. Thus, there is a need to identify chemical scaffolds that can provide inspiration for the development of novel insecticides for FAW management. This study aimed to assess the sensitivity of central neurons and susceptibility of FAW to chloride channel modulators to establish a platform for repurposing existing insecticides or designing new chemicals capable of controlling FAW. Potency of select chloride channel modulators were initially studied against FAW central neuron firing rate and rank order of potency was determined to be fipronil > lindane > Z-stilbene > DIDS > GABA > E-stilbene. Toxicity bioassays identified fipronil and lindane as the two most toxic modulators studied with topical LD50's of 41 and 75 ng/mg of caterpillar, respectively. Interestingly, Z-stilbene was toxic at 300 ng/mg of caterpillar, but no toxicity was observed with DIDS or E-stilbene. The significant shift in potency between stilbene isomers indicates structure-activity relationships between stilbene chemistry and the binding site in FAW may exist. The data presented in this study defines the potency of select chloride channel modulators to FAW neural activity and survivorship to establish a platform for development of novel chemical agents to control FAW populations. Although stilbenes may hold promise for insecticide development, the low toxicity of the scaffolds tested in this study dampen enthusiasm for their development into FAW specific insecticides.
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Affiliation(s)
- Sarah E McComic
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America
| | - Leslie C Rault
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Troy D Anderson
- University of Nebraska, Department of Entomology, 103 Entomology Hall, Lincoln, NE 68583, United States of America
| | - Daniel R Swale
- Louisiana State University AgCenter, Department of Entomology, Baton Rouge, LA 70803, United States of America.
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8
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Monedero Alonso D, Pérès L, Hatem A, Bouyer G, Egée S. The Chloride Conductance Inhibitor NS3623 Enhances the Activity of a Non-selective Cation Channel in Hyperpolarizing Conditions. Front Physiol 2021; 12:743094. [PMID: 34707512 PMCID: PMC8543036 DOI: 10.3389/fphys.2021.743094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 09/13/2021] [Indexed: 12/29/2022] Open
Abstract
Handbooks of physiology state that the strategy adopted by red blood cells (RBCs) to preserve cell volume is to maintain membrane permeability for cations at its minimum. However, enhanced cation permeability can be measured and observed in specific physiological and pathophysiological situations such as in vivo senescence, storage at low temperature, sickle cell anemia and many other genetic defects affecting transporters, membrane or cytoskeletal proteins. Among cation pathways, cation channels are able to dissipate rapidly the gradients that are built and maintained by the sodium and calcium pumps. These situations are very well-documented but a mechanistic understanding of complex electrophysiological events underlying ion transports is still lacking. In addition, non-selective cation (NSC) channels present in the RBC membrane have proven difficult to molecular identification and functional characterization. For instance, NSC channel activity can be elicited by Low Ionic Strength conditions (LIS): the associated change in membrane potential triggers its opening in a voltage dependent manner. But, whereas this depolarizing media produces a spectacular activation of NSC channel, Gárdos channel-evoked hyperpolarization's have been shown to induce sodium entry through a pathway thought to be conductive and termed Pcat. Using the CCCP method, which allows to follow fast changes in membrane potential, we show here (i) that hyperpolarization elicited by Gárdos channel activation triggers sodium entry through a conductive pathway, (ii) that chloride conductance inhibition unveils such conductive cationic conductance, (iii) that the use of the specific chloride conductance inhibitor NS3623 (a derivative of Neurosearch compound NS1652), at concentrations above what is needed for full anion channel block, potentiates the non-selective cation conductance. These results indicate that a non-selective cation channel is likely activated by the changes in the driving force for cations rather than a voltage dependence mechanism per se.
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Affiliation(s)
- David Monedero Alonso
- Sorbonne Université, CNRS, UMR LBI2M, Station Biologique de Roscoff SBR, Roscoff, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Laurent Pérès
- Sorbonne Université, CNRS, UMR LBI2M, Station Biologique de Roscoff SBR, Roscoff, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Aline Hatem
- Sorbonne Université, CNRS, UMR LBI2M, Station Biologique de Roscoff SBR, Roscoff, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Guillaume Bouyer
- Sorbonne Université, CNRS, UMR LBI2M, Station Biologique de Roscoff SBR, Roscoff, France.,Laboratory of Excellence GR-Ex, Paris, France
| | - Stéphane Egée
- Sorbonne Université, CNRS, UMR LBI2M, Station Biologique de Roscoff SBR, Roscoff, France.,Laboratory of Excellence GR-Ex, Paris, France
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Jakobsen E, Andersen JV, Christensen SK, Siamka O, Larsen MR, Waagepetersen HS, Aldana BI, Bak LK. Pharmacological inhibition of mitochondrial soluble adenylyl cyclase in astrocytes causes activation of AMP-activated protein kinase and induces breakdown of glycogen. Glia 2021; 69:2828-2844. [PMID: 34378239 DOI: 10.1002/glia.24072] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 06/28/2021] [Accepted: 07/30/2021] [Indexed: 12/17/2022]
Abstract
Mobilization of astrocyte glycogen is key for processes such as synaptic plasticity and memory formation but the link between neuronal activity and glycogen breakdown is not fully known. Activation of cytosolic soluble adenylyl cyclase (sAC) in astrocytes has been suggested to link neuronal depolarization and glycogen breakdown partly based on experiments employing pharmacological inhibition of sAC. However, several studies have revealed that sAC located within mitochondria is a central regulator of respiration and oxidative phosphorylation. Thus, pharmacological sAC inhibition is likely to affect both cytosolic and mitochondrial sAC and if bioenergetic readouts are studied, the observed effects are likely to stem from inhibition of mitochondrial rather than cytosolic sAC. Here, we report that a pharmacologically induced inhibition of sAC activity lowers mitochondrial respiration, induces phosphorylation of the metabolic master switch AMP-activated protein kinase (AMPK), and decreases glycogen stores in cultured primary murine astrocytes. From these data and our discussion of the literature, mitochondrial sAC emerges as a key regulator of astrocyte bioenergetics. Lastly, we discuss the challenges of investigating the functional and metabolic roles of cytosolic versus mitochondrial sAC in astrocytes employing the currently available pharmacological tool compounds.
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Affiliation(s)
- Emil Jakobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sofie K Christensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Olga Siamka
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Martin R Larsen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lasse K Bak
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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10
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The role of HCO 3- in propionate-induced anion secretion across rat caecal epithelium. Pflugers Arch 2021; 473:937-951. [PMID: 33914143 PMCID: PMC8164622 DOI: 10.1007/s00424-021-02565-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 03/29/2021] [Accepted: 04/08/2021] [Indexed: 12/25/2022]
Abstract
Propionate, a metabolite from the microbial fermentation of carbohydrates, evokes a release of epithelial acetylcholine in rat caecum resulting in an increase of short-circuit current (Isc) in Ussing chamber experiments. The present experiments were performed in order to characterize the ionic mechanisms underlying this response which has been thought to be due to Cl− secretion. As there are regional differences within the caecal epithelium, the experiments were conducted at oral and aboral rat corpus caeci. In both caecal segments, the propionate-induced Isc (IProp) was inhibited by > 85%, when the experiments were performed either in nominally Cl−- or nominally HCO3−-free buffer. In the case of Cl−, the dependency was restricted to the presence of Cl− in the serosal bath. Bumetanide, a blocker of the Na+-K+-2Cl−-cotransporter, only numerically reduced IProp suggesting that a large part of this current must be carried by an ion other than Cl−. In the aboral caecum, IProp was significantly inhibited by mucosally administered stilbene derivatives (SITS, DIDS, DNDS), which block anion exchangers. Serosal Na+-free buffer reduced IProp significantly in the oral (and numerically also in aboral) corpus caeci. RT-PCR experiments revealed the expression of several forms of Na+-dependent HCO3−-cotransporters in caecum, which might underlie the observed Na+ dependency. These results suggest that propionate sensing in caecum is coupled to HCO3– secretion, which functionally would stabilize luminal pH when the microbial fermentation leads to an increase in the concentration of short-chain fatty acids in the caecal lumen.
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11
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Bi YH, Qiao YM, Wang Z, Zhou ZG. Identification and Characterization of a Periplasmic α-Carbonic Anhydrase (CA) in the Gametophytes of Saccharina japonica (Phaeophyceae). JOURNAL OF PHYCOLOGY 2021; 57:295-310. [PMID: 33128798 DOI: 10.1111/jpy.13091] [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: 11/07/2019] [Accepted: 09/08/2020] [Indexed: 06/11/2023]
Abstract
Periplasmic or external carbonic anhydrases (CAs) have been well accepted as playing a crucial role in the acquisition of dissolved inorganic carbon; however, no cytological evidence or molecular information on these enzymes has been reported in seaweeds to date. In this study, the full-length cDNA sequence coding for a putative periplasmic Sjα-CA2 was cloned from the gametophytes of Saccharina japonica, an industrial brown seaweed. It was 1,728 bp in length and included a 263-bp 5'-untranslated region (UTR), a 577-bp 3'-UTR, and an 888-bp open reading frame encoding a protein precursor consisting of 295 amino acids. The mature protein, after removal of a predicted 28-residue signal peptide, was composed of 267 amino acids with a relative molecular weight of 29.27 kDa. Multisequence alignment and phylogenetic analysis indicated that it was a member of the α-CA family. Enzyme activity assays showed that the recombinant Sjα-CA2 in Escherichia coli possessed CO2 hydration and esterase activities, thus identifying this gene Sjα-CA2 in function. Immunogold electron microscopic observations with the prepared anti-Sjα-CA2 polyclonal antibody illustrated that Sjα-CA2 was located in periplasmic space of the kelp gametophyte cells. Quantitative real-time PCR results revealed that the transcription of Sjα-CA2 was induced by elevated HCO 3 - levels, but it was little changed while the kelp gametophytes were subjected to elevated CO2 concentrations. This study suggests that the periplasmic Sjα-CA2 might play a role in adapting to elevated environmental levels of HCO 3 - by dehydration of HCO 3 - to generate CO2 , which could be readily taken up by S. japonica gametophytes.
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Affiliation(s)
- Yan-Hui Bi
- National Demonstration Center for the Experimental Teaching of Fisheries Science, Shanghai Ocean University, Shanghai, 201306, China
| | - Ya-Ming Qiao
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred by Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China
| | - Zhen Wang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources Conferred by Ministry of Education, Shanghai Ocean University, Shanghai, 201306, China
| | - Zhi-Gang Zhou
- International Research Center for Marine Biosciences Conferred by Ministry of Science and Technology, Shanghai Ocean University, Shanghai, 201306, China
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Ivanov IT, Paarvanova BK. Differential dielectroscopic data on the relation of erythrocyte membrane skeleton to erythrocyte deformability and flicker. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2021; 50:69-86. [PMID: 33442752 DOI: 10.1007/s00249-020-01491-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 12/13/2020] [Accepted: 12/20/2020] [Indexed: 10/22/2022]
Abstract
Two dielectric relaxations, βsp (1.5 MHz) and γ1sp (7 MHz), have been detected on spectrin-based membrane skeleton (MS) of red blood cells (RBCs) using the plot of admittance changes at the spectrin denaturation temperature (Ivanov and Paarvanova in Bioelectrochemistry 110: 59-68, 2016, Electrochim Acta 317: 289-300, 2019a). In this study, we treated RBCs and RBC ghost membranes with agents that make membranes rigid and suppress membrane flicker, and studied the effect on βsp and γ1sp relaxations. Diamide (diazene dicarboxylic acid bis-(N,N-dimethylamide)) (up to 0.85 mM), taurine mustard (tris(2-chloroethyl)amine) (up to 2 mM), known to specifically cross-link and stiffen spectrin, and glutaraldehyde (up to 0.044%) all inhibited the relaxations in RBC ghost membranes. Similar inhibition was obtained resealing RBC ghost membranes with 2,3-diphosphoglicerate (up to 15 mM), binding WGA (wheat germ agglutinin) (up to 0.025 mg/ml) to exofacial aspect of RBCs, incubating RBCs in hypotonic (200 mOsm) and hypertonic (600-900 mOsm) media and depleting RBCs of ATP. By contrast, concanavalin A (1 mg/ml) and DIDS (4,4'-diiso-thiocyanato stilbene-2,2'-disulfonic acid) (75 μM, pH 8.2), both known to bind specifically band 3 integral protein of RBCs without effect on RBC membrane rigidity, did not affect the relaxations. We conclude there might be a relation between the strength of dielectric relaxations on MS spectrin and the deformability and flicker of RBC membrane.
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Affiliation(s)
- Ivan T Ivanov
- Department of Physics and Biophysics, Roentgenology and Radiology, Medical Faculty of Thracian University, 6000, Stara Zagora, Bulgaria.
| | - Boyana K Paarvanova
- Department of Physics and Biophysics, Roentgenology and Radiology, Medical Faculty of Thracian University, 6000, Stara Zagora, Bulgaria
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Koster AK, Reese AL, Kuryshev Y, Wen X, McKiernan KA, Gray EE, Wu C, Huguenard JR, Maduke M, Du Bois J. Development and validation of a potent and specific inhibitor for the CLC-2 chloride channel. Proc Natl Acad Sci U S A 2020; 117:32711-32721. [PMID: 33277431 PMCID: PMC7768775 DOI: 10.1073/pnas.2009977117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
CLC-2 is a voltage-gated chloride channel that is widely expressed in mammalian tissues. In the central nervous system, CLC-2 appears in neurons and glia. Studies to define how this channel contributes to normal and pathophysiological function in the central nervous system raise questions that remain unresolved, in part due to the absence of precise pharmacological tools for modulating CLC-2 activity. Herein, we describe the development and optimization of AK-42, a specific small-molecule inhibitor of CLC-2 with nanomolar potency (IC50 = 17 ± 1 nM). AK-42 displays unprecedented selectivity (>1,000-fold) over CLC-1, the closest CLC-2 homolog, and exhibits no off-target engagement against a panel of 61 common channels, receptors, and transporters expressed in brain tissue. Computational docking, validated by mutagenesis and kinetic studies, indicates that AK-42 binds to an extracellular vestibule above the channel pore. In electrophysiological recordings of mouse CA1 hippocampal pyramidal neurons, AK-42 acutely and reversibly inhibits CLC-2 currents; no effect on current is observed on brain slices taken from CLC-2 knockout mice. These results establish AK-42 as a powerful tool for investigating CLC-2 neurophysiology.
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Affiliation(s)
- Anna K Koster
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305
| | - Austin L Reese
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305
| | - Yuri Kuryshev
- Charles River Laboratories Cleveland, Inc., Cleveland, OH 44128
| | - Xianlan Wen
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305
| | - Keri A McKiernan
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Erin E Gray
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Caiyun Wu
- Charles River Laboratories Cleveland, Inc., Cleveland, OH 44128
| | - John R Huguenard
- Department of Neurology & Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305;
| | - Merritt Maduke
- Department of Molecular & Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305;
| | - J Du Bois
- Department of Chemistry, Stanford University, Stanford, CA 94305;
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The anion exchanger PAT-1 (Slc26a6) does not participate in oxalate or chloride transport by mouse large intestine. Pflugers Arch 2020; 473:95-106. [PMID: 33205229 DOI: 10.1007/s00424-020-02495-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 10/23/2020] [Accepted: 11/10/2020] [Indexed: 01/20/2023]
Abstract
The membrane-bound transport proteins responsible for oxalate secretion across the large intestine remain unidentified. The apical chloride/bicarbonate (Cl-/HCO3-) exchanger encoded by Slc26a6, known as PAT-1 (putative anion transporter 1), is a potential candidate. In the small intestine, PAT-1 makes a major contribution to oxalate secretion but whether this role extends into the large intestine has not been directly tested. Using the PAT-1 knockout (KO) mouse, we compared the unidirectional absorptive ([Formula: see text]) and secretory ([Formula: see text]) flux of oxalate and Cl- across cecum, proximal colon, and distal colon from wild-type (WT) and KO mice in vitro. We also utilized the non-specific inhibitor DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid) to confirm a role for PAT-1 in WT large intestine and (in KO tissues) highlight any other apical anion exchangers involved. Under symmetrical, short-circuit conditions the cecum and proximal colon did not transport oxalate on a net basis, whereas the distal colon supported net secretion. We found no evidence for the participation of PAT-1, or indeed any other DIDS-sensitive transport mechanism, in oxalate or Cl- by the large intestine. Most unexpectedly, mucosal DIDS concurrently stimulated [Formula: see text] and [Formula: see text] by 25-68% across each segment without impacting net transport. For the colon, these changes were directly proportional to increased transepithelial conductance suggesting this response was the result of bidirectional paracellular flux. In conclusion, PAT-1 does not contribute to oxalate or Cl- transport by the large intestine, and we urge caution when using DIDS with mouse colonic epithelium.
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Huang W, Han S, Jiang H, Gu S, Li W, Gontero B, Maberly SC. External α-carbonic anhydrase and solute carrier 4 are required for bicarbonate uptake in a freshwater angiosperm. JOURNAL OF EXPERIMENTAL BOTANY 2020; 71:6004-6014. [PMID: 32721017 DOI: 10.1093/jxb/eraa351] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
The freshwater monocot Ottelia alismoides is the only known species to operate three CO2-concentrating mechanisms (CCMs): constitutive bicarbonate (HCO3-) use, C4 photosynthesis, and facultative Crassulacean acid metabolism, but the mechanism of HCO3- use is unknown. We found that the inhibitor of an anion exchange protein, 4,4'-diisothio-cyanatostilbene-2,2'-disulfonate (DIDS), prevented HCO3- use but also had a small effect on CO2 uptake. An inhibitor of external carbonic anhydrase (CA), acetazolamide (AZ), reduced the affinity for CO2 uptake but also prevented HCO3- use via an effect on the anion exchange protein. Analysis of mRNA transcripts identified a homologue of solute carrier 4 (SLC4) responsible for HCO3- transport, likely to be the target of DIDS, and a periplasmic α-carbonic anhydrase 1 (α-CA1). A model to quantify the contribution of the three different pathways involved in inorganic carbon uptake showed that passive CO2 diffusion dominates inorganic carbon uptake at high CO2 concentrations. However, as CO2 concentrations fall, two other pathways become predominant: conversion of HCO3- to CO2 at the plasmalemma by α-CA1 and transport of HCO3- across the plasmalemma by SLC4. These mechanisms allow access to a much larger proportion of the inorganic carbon pool and continued photosynthesis during periods of strong carbon depletion in productive ecosystems.
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Affiliation(s)
- Wenmin Huang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
- Aix Marseille Univ CNRS, BIP UMR 7281, IMM, FR 3479, 31 Chemin Joseph Aiguier, Marseille Cedex 20, France
| | - Shijuan Han
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
- University of the Chinese Academy of Sciences, Beijing, China
| | - Hongsheng Jiang
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
| | - Shuping Gu
- Shanghai Sequen Bio-info Studio, Shanghai, China
| | - Wei Li
- Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Wuhan, China
| | - Brigitte Gontero
- Aix Marseille Univ CNRS, BIP UMR 7281, IMM, FR 3479, 31 Chemin Joseph Aiguier, Marseille Cedex 20, France
| | - Stephen C Maberly
- Lake Ecosystems Group, UK Centre for Ecology & Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster, UK
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16
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Kaur G, Javed W, Ponomarenko O, Shekh K, Swanlund DP, Zhou JR, Summers KL, Casini A, Wenzel MN, Casey JR, Cordat E, Pickering IJ, George GN, Leslie EM. Human red blood cell uptake and sequestration of arsenite and selenite: Evidence of seleno-bis(S-glutathionyl) arsinium ion formation in human cells. Biochem Pharmacol 2020; 180:114141. [PMID: 32652143 DOI: 10.1016/j.bcp.2020.114141] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/24/2020] [Accepted: 07/06/2020] [Indexed: 01/07/2023]
Abstract
Over 200 million people worldwide are exposed to the human carcinogen, arsenic, in contaminated drinking water. In laboratory animals, arsenic and the essential trace element, selenium, can undergo mutual detoxification through the formation of the seleno-bis(S-glutathionyl) arsinium ion [(GS)2AsSe]-, which undergoes biliary and fecal elimination. [(GS)2AsSe]-, formed in animal red blood cells (RBCs), sequesters arsenic and selenium, and slows the distribution of both compounds to peripheral tissues susceptible to toxic effects. In human RBCs, the influence of arsenic on selenium accumulation, and vice versa, is largely unknown. The study aims were to characterize arsenite (AsIII) and selenite (SeIV) uptake by human RBCs, to determine if SeIV and AsIII increase the respective accumulation of the other in human RBCs, and ultimately to determine if this occurs through the formation and sequestration of [(GS)2AsSe]-. 75SeIV accumulation was temperature and Cl--dependent, inhibited by 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid (H2DIDS) (IC50 1 ± 0.2 µM), and approached saturation at 30 µM, suggesting uptake is mediated by the erythrocyte anion-exchanger 1 (AE1 or Band 3, gene SLC4A1). HEK293 cells overexpressing AE1 showed concentration-dependent 75SeIV uptake. 73AsIII uptake by human RBCs was temperature-dependent, partly reduced by aquaglyceroporin 3 inhibitors, and not saturated. AsIII increased 75SeIV accumulation (in the presence of albumin) and SeIV increased 73AsIII accumulation in human RBCs. Near-edge X-ray absorption spectroscopy revealed the formation of [(GS)2AsSe]- in human RBCs exposed to both AsIII and SeIV. The sequestration of [(GS)2AsSe]- in human RBCs potentially slows arsenic distribution to susceptible tissues and could reduce arsenic-induced disease.
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Affiliation(s)
- Gurnit Kaur
- Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, University of Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Canada
| | - Warda Javed
- Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada
| | - Olena Ponomarenko
- Department of Geological Sciences, University of Saskatchewan, Canada
| | - Kamran Shekh
- Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada
| | - Diane P Swanlund
- Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada
| | - Janet R Zhou
- Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, University of Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Canada
| | - Kelly L Summers
- Department of Geological Sciences, University of Saskatchewan, Canada; Department of Chemistry, University of Saskatchewan, Canada
| | - Angela Casini
- School of Chemistry, Cardiff University, UK; Department of Chemistry, Technical University of Munich, Germany
| | | | - Joseph R Casey
- Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada; Department of Biochemistry, University of Alberta, Canada
| | - Emmanuelle Cordat
- Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada
| | - Ingrid J Pickering
- Department of Geological Sciences, University of Saskatchewan, Canada; Department of Chemistry, University of Saskatchewan, Canada
| | - Graham N George
- Department of Geological Sciences, University of Saskatchewan, Canada; Department of Chemistry, University of Saskatchewan, Canada
| | - Elaine M Leslie
- Division of Analytical and Environmental Toxicology, Department of Laboratory Medicine and Pathology, University of Alberta, Canada; Membrane Protein Disease Research Group, University of Alberta, Canada; Department of Physiology, University of Alberta, Canada.
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Vu PD, Rault LC, Jenson LJ, Bloomquist JR, Anderson TD. Voltage-gated chloride channel blocker DIDS as an acaricide for Varroa mites. PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2020; 167:104603. [PMID: 32527437 DOI: 10.1016/j.pestbp.2020.104603] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 06/11/2023]
Abstract
The Varroa mite is a primary driver behind periodical losses of honey bee colonies. These mites require honey bees for food and reproduction and, in turn, elicit physiological deficiencies and diseases that compromise colony health. Current acaricides for Varroa mite control, such as Apistan® (the pyrethroid tau-fluvalinate), CheckMite+® (the organophosphate coumaphos), and Apivar® (the formamidine amitraz) target the nervous system, can have adverse health effects on honey bees, and have limited effectiveness due to reported resistance issues. New target sites are needed to circumvent these obstacles in Varroa mite management, and voltage-gated chloride channels (VGCCs) are promising candidates due to their important role in the maintenance of nerve and muscle excitability in arthropod pests. Toxicological analysis of Varroa mites sensitive to tau-fluvalinate and coumaphos and Varroa mites with reduced sensitivity to these acaricides showed a significant increase in metabolic detoxification enzyme activities for the latter. Acetylcholinesterase activity in the Varroa mites exhibiting reduced mortality to coumaphos was significantly less sensitive to coumaphos-oxon compared to coumaphos-sensitive Varroa mites, which suggests target-site insensitivity to the acaricide. Voltage-gated chloride channel blocker DIDS had significantly greater field efficacy compared to Apistan® and CheckMite+® against Varroa mites from honey bee hives where tau-fluvalinate and coumaphos were observed to be ineffective, respectively. These data suggest that DIDS, and potentially other stilbene chemistries, might serve as candidates for continued field efficacy testing of alternative acaricides in apiaries where Apistan®- and CheckMite+® efficacy has been. reduced or lost for Varroa mites.
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Affiliation(s)
- Philene D Vu
- Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Leslie C Rault
- Department of Entomology, University of Nebraska, Lincoln, NE, USA
| | - Lacey J Jenson
- Department of Entomology, Virginia Tech, Blacksburg, VA, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, USA
| | - Troy D Anderson
- Department of Entomology, University of Nebraska, Lincoln, NE, USA.
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D'Silva NM, O'Donnell MJ. Mechanisms of transport of H +, Na + and K +, across the distal gastric caecum of larval Aedes aegypti. JOURNAL OF INSECT PHYSIOLOGY 2020; 121:103997. [PMID: 31846613 DOI: 10.1016/j.jinsphys.2019.103997] [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: 11/07/2019] [Revised: 12/09/2019] [Accepted: 12/11/2019] [Indexed: 06/10/2023]
Abstract
Measured changes in ion fluxes, transepithelial potential (TEP) and basolateral membrane potential (Vb) in response to ion transporter inhibitors were used to assess the mechanisms of transport of H+, Na+ and K+, across the distal gastric caecum of larval Aedes aegypti, a vector of yellow fever. Preparations were stimulated with 5-hydroxytryptamine (5-HT, 10-6 M) in order to maintain stable rates of H+, Na+, and K+ transport across the distal caecum. Transepithelial potential (TEP), basolateral membrane potential (Vb), and H+, Na+ and K+ fluxes all declined after the addition of a vacuolar-type H+-ATPase (VA) inhibitor, n-ethlymaleimide (NEM), consistent with a primary role for VA in energizing ion transport across the distal gastric caecum. Amiloride also inhibited H+, Na+, and K+ fluxes, consistent with an apically expressed VA that is coupled to a cation:H+ antiporter (AeNHE8), analogous to the coupling of apical VA and cation:nH+ antiporter in Malpighian tubules. A working model of transport of H+, Na+ and K+ across the distal gastric caecum proposes that coupling of VA and AeNHE8 in the apical membrane leads to the removal of intracellular Na+ or K+, thus creating favourable ion gradients to promote the activity of two transporters in the basal membrane, cation:H+ antiporter (AeNHE3) and a bumetanide-sensitive cation chloride cotransporter (CCC).
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Affiliation(s)
- N M D'Silva
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - M J O'Donnell
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada.
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Paschon V, Morena BC, Correia FF, Beltrame GR, Dos Santos GB, Cristante AF, Kihara AH. VDAC1 is essential for neurite maintenance and the inhibition of its oligomerization protects spinal cord from demyelination and facilitates locomotor function recovery after spinal cord injury. Sci Rep 2019; 9:14063. [PMID: 31575916 PMCID: PMC6773716 DOI: 10.1038/s41598-019-50506-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 09/04/2019] [Indexed: 02/08/2023] Open
Abstract
During the progression of the neurodegenerative process, mitochondria participates in several intercellular signaling pathways. Voltage-dependent anion-selective channel 1 (VDAC1) is a mitochondrial porin involved in the cellular metabolism and apoptosis intrinsic pathway in many neuropathological processes. In spinal cord injury (SCI), after the primary cell death, a secondary response that comprises the release of pro-inflammatory molecules triggers apoptosis, inflammation, and demyelination, often leading to the loss of motor functions. Here, we investigated the functional role of VDAC1 in the neurodegeneration triggered by SCI. We first determined that in vitro targeted ablation of VDAC1 by specific morpholino antisense nucleotides (MOs) clearly promotes neurite retraction, whereas a pharmacological blocker of VDAC1 oligomerization (4, 4′-diisothiocyanatostilbene-2, 2′-disulfonic acid, DIDS), does not cause this effect. We next determined that, after SCI, VDAC1 undergoes conformational changes, including oligomerization and N-terminal exposition, which are important steps in the triggering of apoptotic signaling. Considering this, we investigated the effects of DIDS in vivo application after SCI. Interestingly, blockade of VDAC1 oligomerization decreases the number of apoptotic cells without interfering in the neuroinflammatory response. DIDS attenuates the massive oligodendrocyte cell death, subserving undisputable motor function recovery. Taken together, our results suggest that the prevention of VDAC1 oligomerization might be beneficial for the clinical treatment of SCI.
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Affiliation(s)
- Vera Paschon
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil.
| | - Beatriz Cintra Morena
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil
| | - Felipe Fernandes Correia
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil
| | - Giovanna Rossi Beltrame
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil
| | - Gustavo Bispo Dos Santos
- Instituto de Ortopedia e Traumatologia, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil
| | - Alexandre Fogaça Cristante
- Instituto de Ortopedia e Traumatologia, Faculdade de Medicina da Universidade de São Paulo, São Paulo, SP, Brazil
| | - Alexandre Hiroaki Kihara
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil.
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Ivanov I, Paarvanova B. Thermal dielectroscopy study on the vertical and horizontal interactions in erythrocyte sub-membrane skeleton. Electrochim Acta 2019. [DOI: 10.1016/j.electacta.2019.05.159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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21
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Jaunet-Lahary T, Vercauteren DP, Fleury F, Laurent AD. Computational simulations determining disulfonic stilbene derivative bioavailability within human serum albumin. Phys Chem Chem Phys 2019; 20:18020-18030. [PMID: 29931001 DOI: 10.1039/c8cp00704g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Disulfonic stilbene (DS) derivatives are a member of the large family of compounds widely employed in medicine and biology as modulators for membrane transporters or inhibitors of a protein involved in DNA repair. They constitute interesting compounds that have not yet been investigated within the bioavailability framework. No crystallographic structures exist involving such compounds embedded in the most common drug carrier, human serum albumin (HSA). The present work studies, for the first time, the physico-chemical features driving the inclusion of three DS derivatives (amino, nitro and acetamido, named DADS, DNDS and DATDS, respectively) within the four common HSA binding sites using combined molecular docking and molecular dynamics simulations. A careful analysis of each ligand within each of the studied binding sites is carried out, highlighting specific interactions and key residues playing a role in stabilizing the ligand within each pocket. The comparison between DADS, DNDS and DATDS reveals that depending on the binding site, the conclusions are rather different. For instance, the IB binding site shows a specificity to DADS compounds while IIIA is the most favorable site for DNDS and DATDS.
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Affiliation(s)
- Titouan Jaunet-Lahary
- Laboratoire CEISAM - UMR CNRS 6230, Université de Nantes, 2 Rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
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22
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Abstract
CLC proteins are a ubiquitously expressed family of chloride-selective ion channels and transporters. A dearth of pharmacological tools for modulating CLC gating and ion conduction limits investigations aimed at understanding CLC structure/function and physiology. Herein, we describe the design, synthesis, and evaluation of a collection of N-arylated benzimidazole derivatives (BIMs), one of which (BIM1) shows unparalleled (>20-fold) selectivity for CLC-Ka over CLC-Kb, the two most closely related human CLC homologs. Computational docking to a CLC-Ka homology model has identified a BIM1 binding site on the extracellular face of the protein near the chloride permeation pathway in a region previously identified as a binding site for other less selective inhibitors. Results from site-directed mutagenesis experiments are consistent with predictions of this docking model. The residue at position 68 is 1 of only ∼20 extracellular residues that differ between CLC-Ka and CLC-Kb. Mutation of this residue in CLC-Ka and CLC-Kb (N68D and D68N, respectively) reverses the preference of BIM1 for CLC-Ka over CLC-Kb, thus showing the critical role of residue 68 in establishing BIM1 selectivity. Molecular docking studies together with results from structure-activity relationship studies with 19 BIM derivatives give insight into the increased selectivity of BIM1 compared with other inhibitors and identify strategies for further developing this class of compounds.
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23
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Rackwitz R, Gäbel G. Permeation of acetate across sheep ruminal epithelium is partly mediated by an anion channel. Res Vet Sci 2018; 117:10-17. [DOI: 10.1016/j.rvsc.2017.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 10/24/2017] [Accepted: 11/10/2017] [Indexed: 01/21/2023]
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24
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Wong P. A hypothesis of target cell formation in sickle cell disease. Med Hypotheses 2016; 93:102-5. [PMID: 27372866 DOI: 10.1016/j.mehy.2016.05.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/18/2016] [Accepted: 05/19/2016] [Indexed: 11/22/2022]
Abstract
A fraction of erythrocytes appear as target cells in stained blood smears in sickle cell disease, due to a inheritance of the hemoglobin variant Hb S, polymerizing upon deoxygenation. These cells appear in a three dimension as thin cups. A process of their formation in this disease is proposed based on a band 3-based mechanism of the erythrocyte shape control, able to explain the erythrocyte echinocytosis by glucose depletion. It indicates that their formation is due to a stomatocytogenic slow outward transport of the dibasic form of endogenous Pi with an H(+) by band 3, promoted by the decrease of the Donnan ratio, which decreases cell pH and volume, attributed by a decrease of cell KCl concentration by the higher efflux of K(+)Cl(-) cotransport and Ca(2+) activation of the Gardos channel. Its implications are briefly discussed with respect to target cells per se, target cell formation in other hemoglobinopathies, acquired and inherited disorders of the lipid metabolism and dehydrated hereditary stomatocytosis as well as a stomatocyte presence in a double heterozygote of Hb S and Hb C and of an involvement of the process of target cell formation in acanthocytosis in acquired and inherited disorders.
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Affiliation(s)
- P Wong
- Laboratoire de Chimie des Protéines, Montréal, Québec, Canada.
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25
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Ben-Hail D, Shoshan-Barmatz V. VDAC1-interacting anion transport inhibitors inhibit VDAC1 oligomerization and apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1612-23. [DOI: 10.1016/j.bbamcr.2016.04.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Revised: 03/01/2016] [Accepted: 04/06/2016] [Indexed: 10/22/2022]
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Jaunet-Lahary T, Goupille A, Jacquemin D, Fleury F, Graton J, Laurent AD. A Joint Theoretical and Experimental Study of the Behavior of the DIDS Inhibitor and its Derivatives. Chemphyschem 2016; 17:2434-45. [DOI: 10.1002/cphc.201600107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Indexed: 11/08/2022]
Affiliation(s)
- Titouan Jaunet-Lahary
- Laboratoire CEISAM-UMR CNR 6230; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
| | - Anaïs Goupille
- Laboratoire CEISAM-UMR CNR 6230; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
| | - Denis Jacquemin
- Laboratoire CEISAM-UMR CNR 6230; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
- Institut Universitaire de France; 1, rue Descartes 75005 Paris Cedex 05 France
| | - Fabrice Fleury
- Laboratoire UFIP-UMR CNR 6286; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
| | - Jérôme Graton
- Laboratoire CEISAM-UMR CNR 6230; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
| | - Adèle D. Laurent
- Laboratoire CEISAM-UMR CNR 6230; Université de Nantes; 2 Rue de la Houssinière, BP 92208 44322 Nantes Cedex 3 France
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Ivanov IT, Paarvanova B. Dielectric relaxations on erythrocyte membrane as revealed by spectrin denaturation. Bioelectrochemistry 2016; 110:59-68. [PMID: 27071054 DOI: 10.1016/j.bioelechem.2016.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 03/25/2016] [Accepted: 03/26/2016] [Indexed: 11/30/2022]
Abstract
We studied the effect of spectrin denaturation at 49.5°C (TA) on the dielectric relaxations and related changes in the complex impedance, Z*, complex capacitance, C*, and dielectric loss curve of suspensions containing human erythrocytes, erythrocyte ghost membranes (EMs) and Triton-X-100 residues of EMs. The loss curve prior to, minus the loss curve after TA, resulted in a bell-shaped peak at 1.5MHz. The changes in the real and imaginary components of Z* and C* at TA, i.e., ΔZre, ΔZim, ΔCre and ΔCim, calculated in the same way, strongly varied with frequency. Between 1.0 and 12MHz the -ΔZim vs ΔZre, and ΔCim vs ΔCre plots depicted semicircles with critical frequencies, fcr, at 2.5MHz expressing recently reported relaxation of spectrin dipoles. Between 0.02 and 1.0MHz the -ΔZim vs ΔZre plot exhibited another relaxation whose fcr mirrored that of beta relaxation. This relaxation was absent on Triton-X-shells, while on erythrocytes and EMs it was inhibited by selective dissociation of either attachment sites between spectrin and bilayer. Considering above findings and inaccessibility of cytosole to outside field at such frequencies, the latter relaxation was assumed originating from a piezoelectric effect on the highly deformable spectrin filaments.
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Affiliation(s)
- I T Ivanov
- Dept. of Physics, Biophysics, Reontgenology and Radiology, Medical Faculty, Thracian University, Stara Zagora 6000, Bulgaria.
| | - B Paarvanova
- Dept. of Physics, Biophysics, Reontgenology and Radiology, Medical Faculty, Thracian University, Stara Zagora 6000, Bulgaria
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Gray AL, Coleman DT, Castore RF, Mohyeldin MM, El Sayed KA, Cardelli JA. Isothiocyanatostilbenes as novel c-Met inhibitors. Oncotarget 2015; 6:41180-93. [PMID: 26543230 PMCID: PMC4747398 DOI: 10.18632/oncotarget.5748] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 09/17/2015] [Indexed: 01/17/2023] Open
Abstract
The hepatocyte growth factor receptor (HGFR or c-Met) is a driver of multiple cancer subtypes. While there are several c-Met inhibitors in development, few have been approved for clinical use, warranting the need for continued research and development of c-Met targeting therapeutic modalities. The research presented here demonstrates a particular class of compounds known as isothiocyanatostilbenes can act as c-Met inhibitors in multiple cancer cell lines. Specifically, we found that 4,4′-Diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) and 4,4′-Diisothiocyanatodihydrostilbene-2,2′-disulfonic acid (H2DIDS) had c-Met inhibitory effective doses in the low micromolar range while 4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid (SITS) and 4,4′-dinitrostilbene-2, 2′-disulfonic acid (DNDS) exhibited IC50s 100 to 1000 fold higher. These compounds displayed much greater selectivity for inhibiting c-Met activation compared to similar receptor tyrosine kinases. In addition, DIDS and H2DIDS reduced hepatocyte growth factor (HGF)-induced, but not epidermal growth factor (EGF)-induced, cell scattering, wound healing, and 3-dimensional (3D) proliferation of tumor cell spheroids. In-cell and cell-free assays suggested that DIDS and H2DIDS can inhibit and reverse c-Met phosphorylation, similar to SU11274. Additional data demonstrated that DIDS is tolerable in vivo. These data provide preliminary support for future studies examining DIDS, H2DIDS, and derivatives as potential c-Met therapeutics.
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Affiliation(s)
- Alana L Gray
- Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, USA.,Feist-Weiller Cancer Center, Shreveport, LA, USA
| | - David T Coleman
- Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, USA.,Feist-Weiller Cancer Center, Shreveport, LA, USA
| | - Reneau F Castore
- Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, USA.,Feist-Weiller Cancer Center, Shreveport, LA, USA
| | | | | | - James A Cardelli
- Louisiana State University Health Sciences Center - Shreveport, Shreveport, LA, USA.,Feist-Weiller Cancer Center, Shreveport, LA, USA
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Bicarbonate transporters in corals point towards a key step in the evolution of cnidarian calcification. Sci Rep 2015; 5:9983. [PMID: 26040894 PMCID: PMC4650655 DOI: 10.1038/srep09983] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 03/24/2015] [Indexed: 12/19/2022] Open
Abstract
The bicarbonate ion (HCO3−) is involved in two major physiological processes in corals, biomineralization and photosynthesis, yet no molecular data on bicarbonate transporters are available. Here, we characterized plasma membrane-type HCO3− transporters in the scleractinian coral Stylophora pistillata. Eight solute carrier (SLC) genes were found in the genome: five homologs of mammalian-type SLC4 family members, and three of mammalian-type SLC26 family members. Using relative expression analysis and immunostaining, we analyzed the cellular distribution of these transporters and conducted phylogenetic analyses to determine the extent of conservation among cnidarian model organisms. Our data suggest that the SLC4γ isoform is specific to scleractinian corals and responsible for supplying HCO3− to the site of calcification. Taken together, SLC4γ appears to be one of the key genes for skeleton building in corals, which bears profound implications for our understanding of coral biomineralization and the evolution of scleractinian corals within cnidarians.
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Kao L, Azimov R, Abuladze N, Newman D, Kurtz I. Human SLC4A11-C functions as a DIDS-stimulatable H⁺(OH⁻) permeation pathway: partial correction of R109H mutant transport. Am J Physiol Cell Physiol 2014; 308:C176-88. [PMID: 25394471 DOI: 10.1152/ajpcell.00271.2014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The SLC4A11 gene mutations cause a variety of genetic corneal diseases, including congenital hereditary endothelial dystrophy 2 (CHED2), Harboyan syndrome, some cases of Fuchs' endothelial dystrophy (FECD), and possibly familial keratoconus. Three NH2-terminal variants of the human SLC4A11 gene, named SLC4A11-A, -B, and -C are known. The SLC4A11-B variant has been the focus of previous studies. Both the expression of the SLC4A11-C variant in the cornea and its functional properties have not been characterized, and therefore its potential pathophysiological role in corneal diseases remains to be explored. In the present study, we demonstrate that SLC4A11-C is the predominant SLC4A11 variant expressed in human corneal endothelial mRNA and that the transporter functions as an electrogenic H(+)(OH(-)) permeation pathway. Disulfonic stilbenes, including 4,4'-diisothiocyano-2,2'-stilbenedisulfonate (DIDS), 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonate (H2DIDS), and 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonate (SITS), which are known to bind covalently, increased SLC4A11-C-mediated H(+)(OH(-)) flux by 150-200% without having a significant effect in mock-transfected cells. Noncovalently interacting 4,4'-diaminostilbene-2,2'-disulfonate (DADS) was without effect. We tested the efficacy of DIDS on the functionally impaired R109H mutant (SLC4A11-C numbering) that causes CHED2. DIDS (1 mM) increased H(+)(OH(-)) flux through the mutant transporter by ∼40-90%. These studies provide a basis for future testing of more specific chemically modified dilsulfonic stilbenes as potential therapeutic agents to improve the functional impairment of specific SLC4A11 mutant transporters.
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Affiliation(s)
- Liyo Kao
- Division of Nephrology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and
| | - Rustam Azimov
- Division of Nephrology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and
| | - Natalia Abuladze
- Division of Nephrology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and
| | - Debra Newman
- Division of Nephrology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and
| | - Ira Kurtz
- Division of Nephrology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California; and Brain Research Institute, University of California Los Angeles, Los Angeles, California
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31
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Prati F, Goldman-Pinkovich A, Lizzi F, Belluti F, Koren R, Zilberstein D, Bolognesi ML. Quinone-amino acid conjugates targeting Leishmania amino acid transporters. PLoS One 2014; 9:e107994. [PMID: 25254495 PMCID: PMC4177859 DOI: 10.1371/journal.pone.0107994] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/22/2014] [Indexed: 01/23/2023] Open
Abstract
The aim of the present study was to investigate the feasibility of targeting Leishmania transporters via appropriately designed chemical probes. Leishmania donovani, the parasite that causes visceral leishmaniasis, is auxotrophic for arginine and lysine and has specific transporters (LdAAP3 and LdAAP7) to import these nutrients. Probes 1–15 were originated by conjugating cytotoxic quinone fragments (II and III) with amino acids (i.e. arginine and lysine) by means of an amide linkage. The toxicity of the synthesized conjugates against Leishmania extracellular (promastigotes) and intracellular (amastigotes) forms was investigated, as well their inhibition of the relevant amino acid transporters. We observed that some conjugates indeed displayed toxicity against the parasites; in particular, 7 was identified as the most potent derivative (at concentrations of 1 µg/mL and 2.5 µg/mL residual cell viability was reduced to 15% and 48% in promastigotes and amastigotes, respectively). Notably, 6, while retaining the cytotoxic activity of quinone II, displayed no toxicity against mammalian THP1 cells. Transport assays indicated that the novel conjugates inhibited transport activity of lysine, arginine and proline transporters. Furthermore, our analyses suggested that the toxic conjugates might be translocated by the transporters into the cells. The non-toxic probes that inhibited transport competed with the natural substrates for binding to the transporters without being translocated. Thus, it is likely that 6, by exploiting amino acid transporters, can selectively deliver its toxic effects to Leishmania cells. This work provides the first evidence that amino acid transporters of the human pathogen Leishmania might be modulated by small molecules, and warrants their further investigation from drug discovery and chemical biology perspectives.
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Affiliation(s)
- Federica Prati
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | | | - Federica Lizzi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | - Federica Belluti
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy
| | - Roni Koren
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Dan Zilberstein
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Maria Laura Bolognesi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum University of Bologna, Bologna, Italy
- * E-mail:
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Ju M, Scott-Ward TS, Liu J, Khuituan P, Li H, Cai Z, Husbands SM, Sheppard DN. Loop diuretics are open-channel blockers of the cystic fibrosis transmembrane conductance regulator with distinct kinetics. Br J Pharmacol 2014; 171:265-78. [PMID: 24117047 DOI: 10.1111/bph.12458] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 09/21/2013] [Accepted: 09/26/2013] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE Loop diuretics are widely used to inhibit the Na(+), K(+), 2Cl(-) co-transporter, but they also inhibit the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. Here, we investigated the mechanism of CFTR inhibition by loop diuretics and explored the effects of chemical structure on channel blockade. EXPERIMENTAL APPROACH Using the patch-clamp technique, we tested the effects of bumetanide, furosemide, piretanide and xipamide on recombinant wild-type human CFTR. KEY RESULTS When added to the intracellular solution, loop diuretics inhibited CFTR Cl(-) currents with potency approaching that of glibenclamide, a widely used CFTR blocker with some structural similarity to loop diuretics. To begin to study the kinetics of channel blockade, we examined the time dependence of macroscopic current inhibition following a hyperpolarizing voltage step. Like glibenclamide, piretanide blockade of CFTR was time and voltage dependent. By contrast, furosemide blockade was voltage dependent, but time independent. Consistent with these data, furosemide blocked individual CFTR Cl(-) channels with 'very fast' speed and drug-induced blocking events overlapped brief channel closures, whereas piretanide inhibited individual channels with 'intermediate' speed and drug-induced blocking events were distinct from channel closures. CONCLUSIONS AND IMPLICATIONS Structure-activity analysis of the loop diuretics suggests that the phenoxy group present in bumetanide and piretanide, but absent in furosemide and xipamide, might account for the different kinetics of channel block by locking loop diuretics within the intracellular vestibule of the CFTR pore. We conclude that loop diuretics are open-channel blockers of CFTR with distinct kinetics, affected by molecular dimensions and lipophilicity.
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Affiliation(s)
- Min Ju
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Ando M, Wong MKS, Takei Y. Mechanisms of guanylin action on water and ion absorption at different regions of seawater eel intestine. Am J Physiol Regul Integr Comp Physiol 2014; 307:R653-63. [PMID: 24990857 DOI: 10.1152/ajpregu.00543.2013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Guanylin (GN) inhibited water absorption and short-circuit current (Isc) in seawater eel intestine. Similar inhibition was observed after bumetanide, and the effect of bumetanide was abolished by GN or vice versa, suggesting that both act on the same target, Na(+)-K(+)-2Cl(-) cotransporter (NKCC), which is a key player for the Na(+)-K(+)-Cl(-) transport system responsible for water absorption in marine teleost intestine. However, effect of GN was always greater than that of bumetanide: 10% greater in middle intestine (MI) and 40% in posterior intestine (PI) for Isc, and 25% greater in MI and 34% in PI for water absorption. After treatment with GN, Isc decreased to zero, but 20-30% water absorption still remained. The remainder may be due to the Cl(-)/HCO3 (-) exchanger and Na(+)-Cl(-) cotransporter (NCC), since inhibitors for these transporters almost nullified the remaining water absorption. Quantitative PCR analysis revealed the presence of major proteins involved in water absorption; the NKCC2β and AQP1 genes whose expression was markedly upregulated after seawater acclimation. The SLC26A6 (anion exchanger) and NCCβ genes were also expressed in small amounts. Consistent with the inhibitors' effect, expression of NKCC2β was MI > PI, and that of NCCβ was MI << PI. The present study showed that GN not only inhibits the bumetanide-sensitive Na(+)-K(+)-Cl(-) transport system governed by NKCC2β, but also regulates unknown ion transporters different from GN-insensitive SLC26A6 and NCC. A candidate is cystic fibrosis transmembrane conductance regulator Cl(-) channel, as demonstrated in mammals, but its expression is low in eel intestine, and its role may be minor, as indicated by the small effect of its inhibitors.
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Affiliation(s)
- Masaaki Ando
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Marty K S Wong
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
| | - Yoshio Takei
- Laboratory of Physiology, Department of Marine Bioscience, Atmosphere and Ocean Research Institute, The University of Tokyo, Chiba, Japan
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Romero MF, Chen AP, Parker MD, Boron WF. The SLC4 family of bicarbonate (HCO₃⁻) transporters. Mol Aspects Med 2013; 34:159-82. [PMID: 23506864 DOI: 10.1016/j.mam.2012.10.008] [Citation(s) in RCA: 239] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 08/28/2012] [Indexed: 01/13/2023]
Abstract
The SLC4 family consists of 10 genes (SLC4A1-5; SLC4A7-11). All encode integral membrane proteins with very similar hydropathy plots-consistent with 10-14 transmembrane segments. Nine SLC4 members encode proteins that transport HCO3(-) (or a related species, such as CO3(2-)) across the plasma membrane. Functionally, eight of these proteins fall into two major groups: three Cl-HCO3 exchangers (AE1-3) and five Na(+)-coupled HCO3(-) transporters (NBCe1, NBCe2, NBCn1, NBCn2, NDCBE). Two of the Na(+)-coupled transporters (NBCe1, NBCe2) are electrogenic; the other three Na(+)-coupled HCO3(-) transporters and all three AEs are electroneutral. In addition, two other SLC4 members (AE4, SLC4A9 and BTR1, SLC4A11) do not yet have a firmly established function. Most, though not all, SLC4 members are functionally inhibited by 4,4'-diisothiocyanatostilbene-2,2'-disulfonate (DIDS). SLC4 proteins play important roles many modes of acid-base homeostasis: the carriage of CO2 by erythrocytes, the transport of H(+) or HCO3(-) by several epithelia, as well as the regulation of cell volume and intracellular pH.
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Affiliation(s)
- Michael F Romero
- Physiology & Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
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35
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Loqman MY, Bush PG, Farquharson C, Hall AC. Suppression of mammalian bone growth by membrane transport inhibitors. J Cell Biochem 2013; 114:658-68. [PMID: 23059814 DOI: 10.1002/jcb.24408] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 09/21/2012] [Indexed: 12/12/2022]
Abstract
Bone lengthening during skeletal growth is driven primarily by the controlled enlargement of growth plate (GP) chondrocytes. The cellular mechanisms are unclear but membrane transporters are probably involved. We investigated the role of the Na(+)/H(+) antiporter (NHE1) and anion exchanger (AE2) in bone lengthening and GP chondrocyte hypertrophy in Sprague-Dawley 7-day-old rat (P7) bone rudiments using the inhibitors EIPA (5-(N-ethyl-N-isopropyl)amiloride) and DIDS (4,4-diidothiocyano-2,2-stilbenedisulphonate), respectively. We have also determined cell-associated levels of these transporters along the GP using fluorescent immunohistochemistry (FIHC). Culture of bones with EIPA or DIDS inhibited rudiment growth (50% at approx. 250 and 25 µM, respectively). Both decreased the size of the hypertrophic zone (P < 0.05) but had no effect on overall length or cell density of the GP. In situ chondrocyte volume in proliferative and hypertrophic zones was decreased (P < 0.01) with EIPA but not DIDS. FIHC labeling of NHE1 was relatively high and constant along the GP but declined steeply in the late hypertrophic zone. In contrast, AE2 labeling was relatively low in proliferative zone cells but increased (P < 0.05) reaching a maximum in the early hypertrophic zone, before falling rapidly in the late hypertrophic zone suggesting AE2 might regulate the transition phase of chondrocytes between proliferative and hypertrophic zones. The inhibition of bone growth by EIPA may be due to a reduction to chondrocyte volume set-point. However the effect of DIDS was unclear but could result from inhibition of AE2 and blocking of the transition phase. These results demonstrate that NHE1 and AE2 are important regulators of bone growth.
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Affiliation(s)
- Mohamad Y Loqman
- Centre for Integrative Physiology, School of Biomedical Sciences, George Square, University of Edinburgh, Edinburgh EH8 9XD, Scotland, UK
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36
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Vilas GL, Loganathan SK, Liu J, Riau AK, Young JD, Mehta JS, Vithana EN, Casey JR. Transmembrane water-flux through SLC4A11: a route defective in genetic corneal diseases. Hum Mol Genet 2013; 22:4579-90. [PMID: 23813972 PMCID: PMC3889808 DOI: 10.1093/hmg/ddt307] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Three genetic corneal dystrophies [congenital hereditary endothelial dystrophy type 2 (CHED2), Harboyan syndrome and Fuchs endothelial corneal dystrophy] arise from mutations of the SLC4a11 gene, which cause blindness from fluid accumulation in the corneal stroma. Selective transmembrane water conductance controls cell size, renal fluid reabsorption and cell division. All known water-channelling proteins belong to the major intrinsic protein family, exemplified by aquaporins (AQPs). Here we identified SLC4A11, a member of the solute carrier family 4 of bicarbonate transporters, as an unexpected addition to known transmembrane water movement facilitators. The rate of osmotic-gradient driven cell-swelling was monitored in Xenopus laevis oocytes and HEK293 cells, expressing human AQP1, NIP5;1 (a water channel protein from plant), hCNT3 (a human nucleoside transporter) and human SLC4A11. hCNT3-expressing cells swelled no faster than control cells, whereas SLC4A11-mediated water permeation at a rate about half that of some AQP proteins. SLC4A11-mediated water movement was: (i) similar to some AQPs in rate; (ii) uncoupled from solute-flux; (iii) inhibited by stilbene disulfonates (classical SLC4 inhibitors); (iv) inactivated in one CHED2 mutant (R125H). Localization of AQP1 and SLC4A11 in human and murine corneal (apical and basolateral, respectively) suggests a cooperative role in mediating trans-endothelial water reabsorption. Slc4a11(-/-) mice manifest corneal oedema and distorted endothelial cells, consistent with loss of a water-flux. Observed water-flux through SLC4A11 extends the repertoire of known water movement pathways and call for a re-examination of explanations for water movement in human tissues.
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Affiliation(s)
- Gonzalo L Vilas
- Membrane Protein Disease Research Group, Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Abstract
The lack of small-molecule inhibitors for anion-selective transporters and channels has impeded our understanding of the complex mechanisms that underlie ion passage. The ubiquitous CLC "Chloride Channel" family represents a unique target for biophysical and biochemical studies because its distinctive protein fold supports both passive chloride channels and secondary-active chloride-proton transporters. Here, we describe the synthesis and characterization of a specific small-molecule inhibitor directed against a CLC antiporter (ClC-ec1). This compound, 4,4'-octanamidostilbene-2,2'-disulfonate (OADS), inhibits ClC-ec1 with low micromolar affinity and has no specific effect on a CLC channel (ClC-1). Inhibition of ClC-ec1 occurs by binding to two distinct intracellular sites. The location of these sites and the lipid dependence of inhibition suggest potential mechanisms of action. This compound will empower research to elucidate differences between antiporter and channel mechanisms and to develop treatments for CLC-mediated disorders.
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New insights into roles of acidocalcisomes and contractile vacuole complex in osmoregulation in protists. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 305:69-113. [PMID: 23890380 DOI: 10.1016/b978-0-12-407695-2.00002-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking.
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Abstract
The synergistic effects of hemoglobin, carbonic anhydrase and the band 3 protein make red blood cells the ideal vehicle for oxygen delivering to the tissues. As long as oxygen is supplied by these ideal vehicles, oxygen intoxication of the tissues is precluded. Band 3 protein mediates the "Chloride-Shift", i.e., the anion exchange of Cl(-)/HCO(3) (-). Because of the Chloride-Shift, red blood cells are able to recognize metabolically active tissues and to supply the minimum amount of oxygen to the tissues. Investigation into the molecular mechanisms of the anion exchange mediated by the band 3 protein was introduced.
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40
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Alexandrou D, Walters DV. The role of Cl- in the regulation of ion and liquid transport in the intact alveolus during β-adrenergic stimulation. Exp Physiol 2012; 98:576-84. [PMID: 22872661 DOI: 10.1113/expphysiol.2012.066159] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The epithelium of the developing lung displays an evolving liquid transport phenotype, in which Cl(-) secretion during fetal life is rapidly switched to Na(+) absorption perinatally. However, the mechanisms underlying the homeostasis of the thin layer of liquid lining the postnatal pulmonary epithelium remain elusive. In particular, it remains unclear whether the stimulated clearance of excess alveolar liquid is mediated via transepithelial Cl(-) transport. Our study is a pharmacological analysis with the aim of addressing this issue, which is of major physiological significance in cases of pulmonary oedema from any cause. We measured the rate of transepithelial liquid movement (J(v)) with (125)I-albumin, in the in situ perfused adult rat lung. Transepithelial Cl(-) transport was studied with the use of the Cl(-) channel inhibitor NPPB in the resting state and during stimulation with the β(2)-adrenergic agonist terbutaline. The study of J(v) in these conditions revealed the following findings: (1) there is net absorption of excess of alveolar liquid in the resting, unstimulated state, which is predominantly amiloride sensitive; (2) inhibition of Cl(-) transport with NPPB in the resting state results in a 1.6-fold increase in net absorption of alveolar liquid; and (3) the terbutaline-stimulated net absorption of the excess liquid is enhanced by 2.8-fold in the presence of NPPB. Our results are suggestive of the functional presence of secretory, but not absorptive, Cl(-) mechanisms and show that transepithelial Cl(-) transport is not part of the mechanism underlying lung liquid clearance in response to β-adrenergic stimulation.
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Henkin AH, Ortegon AM, Cho S, Shen WJ, Falcon A, Kraemer FB, Lee SJ, Stahl A. Evidence for protein-mediated fatty acid efflux by adipocytes. Acta Physiol (Oxf) 2012; 204:562-70. [PMID: 21951599 DOI: 10.1111/j.1748-1716.2011.02367.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
AIM The hormonally controlled mobilization and release of fatty acids from adipocytes into the circulation is an important physiological process required for energy homeostasis. While uptake of fatty acids by adipocytes has been suggested to be predominantly protein-mediated, it is unclear whether the efflux of fatty acids also requires membrane proteins. METHODS We used fluorescent fatty acid efflux assays and colorimetric assays for free fatty acids and glycerol to identify inhibitors with effects on fatty acid efflux, but not lipolysis, in 3T3-L1 adipocytes. We assessed the effect of these inhibitors on a fibroblast-based cell line expressing fatty acid transport protein 1, hormone-sensitive lipase and perilipin, which presumably lacks adipocyte-specific proteins for fatty acid efflux. RESULTS We identified 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) as an inhibitor of fatty acid efflux that did not impair lipolysis or the cellular exit of glycerol but lead to an accumulation of intracellular fatty acids. In contrast, fatty acid efflux by the reconstituted cellular model for fatty acid efflux was responsive to lipolytic stimuli, but insensitive to DIDS inhibition. CONCLUSION We propose that adipocytes specifically express an as yet unidentified DIDS-sensitive protein that enhances the efflux of fatty acids and therefore may lead to novel treatment approaches for obesity-related disorders characterized by abnormal lipid fluxes and ectopic triglyceride accumulation.
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Affiliation(s)
- A H Henkin
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, USA
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Gill M, Bartolo RC, Demmers K, Harfoot N, Fan S, Butt G. The distribution and expression of CFTR restricts electrogenic anion secretion to the ileum of the brushtail possum, Trichosurus vulpecula. ACTA ACUST UNITED AC 2011; 214:1943-54. [PMID: 21562182 DOI: 10.1242/jeb.053371] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In eutherian mammals, fluid secretion is essential for intestinal function. This is driven by electrogenic Cl(-) secretion, which involves a NaK2Cl cotransporter (NKCC1) in the enterocyte basolateral membrane and the cystic fibrosis transmembrane conductance regulator (CFTR) in the apical membrane. However, in the possum ileum, NKCC1 expression is low and secretagogues stimulate electrogenic HCO(3)(-) secretion driven by a basolateral NaHCO(3) cotransporter (pNBCe1). Here we investigated whether electrogenic anion secretion occurs in possum duodenum and jejunum and determined the role of CFTR in possum intestinal anion secretion. Prostaglandin E(2) (PGE(2)) and forskolin stimulated a large increase in ileal short-circuit current (I(sc)), consistent with electrogenic HCO(3)(-) secretion, but had little effect on the duodenal and jejunal I(sc). Furthermore, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and N-(2-naphthalenyl)-[(3,5-dibromo-2,4-dihydroxyphenyl)methylene]glycine hydrazide (GlyH101) inhibited cloned possum CFTR in cultured cells and the PGE(2)-stimulated ileal I(sc), implicating CFTR in ileal HCO(3)(-) secretion. Consistent with this, CFTR is expressed in the apical membrane of ileal crypt and lower villous cells, which also express pNBCe1 in the basolateral membrane. In contrast, duodenal and jejunal CFTR expression is low relative to the ileum. Jejunal pNBCe1 expression is also low, whereas duodenal and ileal pNBCe1 expression are comparable. All regions have low NKCC1 expression. These results indicate that cAMP-dependent electrogenic Cl(-) secretion does not occur in the possum small intestine because of the absence of CFTR and NKCC1. Furthermore, CFTR functions as the apical anion conductance associated with HCO(3)(-) secretion and its distribution limits electrogenic HCO(3)(-) secretion to the ileum.
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Affiliation(s)
- Mike Gill
- Department of Physiology, School of Medical Sciences, University of Otago, Dunedin, New Zealand
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Lahn M, Dosche C, Hille C. Two-photon microscopy and fluorescence lifetime imaging reveal stimulus-induced intracellular Na+ and Cl− changes in cockroach salivary acinar cells. Am J Physiol Cell Physiol 2011; 300:C1323-36. [DOI: 10.1152/ajpcell.00320.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The intracellular ion homeostasis in cockroach salivary acinar cells during salivation is not satisfactorily understood. This is mainly due to technical problems regarding strong tissue autofluorescence and ineffective ion concentration quantification. For minimizing these problems, we describe the successful application of two-photon (2P) microscopy partly in combination with fluorescence lifetime imaging microscopy (FLIM) to record intracellular Na+ and Cl− concentrations ([Na+]i, [Cl−]i) in cockroach salivary acinar cells. Quantitative 2P-FLIM Cl− measurements with the dye N-(ethoxycarbonylmethyl)-6-methoxy-quinolinium bromide indicate that the resting [Cl−]i is 1.6 times above the Cl− electrochemical equilibrium but is not influenced by pharmacological inhibition of the Na+-K+-2Cl− cotransporter (NKCC) and anion exchanger using bumetanide and 4,4′-diisothiocyanatodihydrostilbene-2,2′-disulfonic acid disodium salt. In contrast, rapid Cl− reuptake after extracellular Cl− removal is almost totally NKCC mediated both in the absence and presence of dopamine. However, in physiological saline [Cl−]i does not change during dopamine stimulation although dopamine stimulates fluid secretion in these glands. On the other hand, dopamine causes a decrease in the sodium-binding benzofuran isophthalate tetra-ammonium salt (SBFI) fluorescence and an increase in the Sodium Green fluorescence after 2P excitation. This opposite behavior of both dyes suggests a dopamine-induced [Na+]i rise in the acinar cells, which is supported by the determined 2P-action cross sections of SBFI. The [Na+]i rise is Cl− dependent and inhibited by bumetanide. The Ca2+-ionophore ionomycin also causes a bumetanide-sensitive [Na+]i rise. We propose that a Ca2+-mediated NKCC activity in acinar peripheral cells attributable to dopamine stimulation serves for basolateral Na+ uptake during saliva secretion and that the concomitantly transported Cl− is recycled back to the bath.
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Affiliation(s)
- Mattes Lahn
- Physical Chemistry, Applied Laser Sensing, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Carsten Dosche
- Physical Chemistry, Applied Laser Sensing, Institute of Chemistry, University of Potsdam, Potsdam, Germany
| | - Carsten Hille
- Physical Chemistry, Applied Laser Sensing, Institute of Chemistry, University of Potsdam, Potsdam, Germany
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Tokuda N, Igarashi K, Shimamura T, Yurugi-Kobayashi T, Shiroishi M, Ito K, Sugawara T, Asada H, Murata T, Nomura N, Iwata S, Kobayashi T. Cloning, expression and purification of the anion exchanger 1 homologue from the basidiomycete Phanerochaete chrysosporium. Protein Expr Purif 2011; 79:81-7. [PMID: 21515379 DOI: 10.1016/j.pep.2011.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 04/06/2011] [Accepted: 04/08/2011] [Indexed: 11/27/2022]
Abstract
Anion exchangers are membrane proteins that have been identified in a wide variety of species, where they transport Cl(-) and HCO3(-)across the cell membrane. In this study, we cloned an anion-exchange protein from the genome of the basidiomycete Phanerochaete chrysosporium (PcAEP). PcAEP is a 618-amino acid protein that is homologous to the human anion exchanger (AE1) with 22.9% identity and 40.3% similarity. PcAEP was overexpressed by introducing the PcAEP gene into the genome of Pichia pastoris. As a result, PcAEP localized in the membrane of P. pastoris and was solubilized successfully by n-dodecyl-β-D-maltoside. His-tagged PcAEP was purified as a single band on SDS-PAGE using immobilized metal affinity chromatography and gel filtration chromatography. Purified PcAEP was found to bind to SITS, an inhibitor of the AE family, suggesting that the purified protein is folded properly. PcAEP expressed and purified using the present system could be useful for biological and structural studies of the anion exchange family of proteins.
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Affiliation(s)
- Natsuko Tokuda
- Department of Medical Chemistry, Kyoto University Faculty of Medicine, Sakyo-ku, Kyoto, Japan
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Ivanov IT, Zheleva A, Zlatanov I. Anion exchanger and the resistance against thermal haemolysis. Int J Hyperthermia 2011; 27:286-96. [PMID: 21501030 DOI: 10.3109/02656736.2011.554064] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
4,4'-Diiso-thiocyanato stilbene-2,2'-disulphonic acid (DIDS) is a membrane-impermeable, highly specific covalent inhibitor and powerful thermal stabiliser of the anion exchanger (AE1), the major integral protein of erythrocyte membrane (EM). Suspensions of control and DIDS-treated (15 µM, pH 8.2) human erythrocytes were heated from 20° to 70°C using various but constant heating rates (1-8°C/min). The cellular electrolyte leakage exhibited a sigmoidal response to temperature as detected by conductometry. The critical midpoint temperature of leakage, T(mo), extrapolated to low heating rate (0.5°C/min) was used as a measure for EM thermostability. T(mo) was greater for DIDS-treated erythrocytes, 63.2° ± 0.3°C, than for intact erythrocytes, 60.7° ± 0.2°C. The time, t(1/2), for 50% haemolysis of erythrocytes, exposed to 53°C was used as a measure for the resistance of erythrocytes against thermal haemolysis. The t(1/2) was also greater for DIDS-treated erythrocytes, 63 ± 3 min, than for intact erythrocytes, 38 ± 2 min. The fluorescent label N-(3-pyrenyl)maleimide and EPR spin label 3-maleimido-proxyl, covalently bound to sulphydryl groups of major EM proteins, were used to monitor the changes in molecular motions during transient heating. Both labels reported an intensification of the motional dynamics at the denaturation temperatures of spectrin (50°C) and AE1 (67°C), and, surprisingly, immobilisation of a major EM protein, presumably the AE1, at T(mo). The above results are interpreted in favour of the possible involvement of a predenaturational rearrangement of AE1 copies in the EM thermostability and the resistance against thermal haemolysis.
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Affiliation(s)
- I T Ivanov
- Department of Physics, Biophysics, Roentgenology and Radiology, Medical Faculty, Thracian University, 11 Armeyska str., Stara Zagora, Bulgaria.
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Involvement of carboxyl groups in chloride transport and reversible DIDS binding to band 3 protein in human erythrocytes. Cell Mol Biol Lett 2011; 16:342-58. [PMID: 21442446 PMCID: PMC6275994 DOI: 10.2478/s11658-011-0010-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2011] [Accepted: 03/11/2011] [Indexed: 11/24/2022] Open
Abstract
Noncovalent DIDS binding to Band 3 (AE1) protein in human erythrocyte membranes, modified by non-penetrating, water soluble 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)-carbodiimide iodide (EAC), was studied at 0°C in the presence of 165 mM KCl. Under experimental conditions applied up to (48 ± 5) % of irreversible chloride self-exchange inhibition was observed. The apparent dissociation constant, KD, for “DIDS-Band 3” complex, determined from the chloride transport experiments, was (34 ± 3) nM and (80 ± 12) nM for control and EAC-treated resealed ghosts, respectively. The inhibition constant, Ki, for DIDS was (35 ± 6) nM and (60 ± 8) nM in control and EAC-treated ghosts, respectively. The reduced affinity for DIDS reversible binding was not a result of negative cooperativity of DIDS binding sites of Band 3 oligomer since Hill’s coefficients were indistinguishable from 1 (within the limit error) both for control and EAC-treated ghosts. By using tritium-labeled DIDS, 4,4’-diisothiocyanato-2,2’-stilbenedisulfonate ([3H]DIDS), the association rate constant, k+1 (M−1s−1), was measured. The mean values of (4.3 ± 0.7) × 105 M−1s−1 for control and (2.7 ± 0.7) × 105 M−1s−1 for EAC-treated ghosts were obtained. The mean values for KD, evaluated from [3H]DIDS binding measurements, were (37 ± 9) nM and (90 ± 21) nM for control and EAC-modified ghosts, respectively. The results demonstrate that EAC modification of AE1 reduces about 2-fold the affinity of AE1 for DIDS. It is suggested that half of the subunits are modified near the transport site by EAC.
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Vilas GL, Morgan PE, Loganathan SK, Quon A, Casey JR. A Biochemical Framework for SLC4A11, the Plasma Membrane Protein Defective in Corneal Dystrophies. Biochemistry 2011; 50:2157-69. [DOI: 10.1021/bi101887z] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Gonzalo L. Vilas
- Membrane Protein Disease Research Group, Department of Physiology, and Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Canada T6G 2H7
| | - Patricio E. Morgan
- Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina CP1900
| | - Sampath K. Loganathan
- Membrane Protein Disease Research Group, Department of Physiology, and Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Canada T6G 2H7
| | - Anita Quon
- Membrane Protein Disease Research Group, Department of Physiology, and Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Canada T6G 2H7
| | - Joseph R. Casey
- Membrane Protein Disease Research Group, Department of Physiology, and Department of Biochemistry, School of Molecular and Systems Medicine, University of Alberta, Edmonton, Canada T6G 2H7
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Berger J, Richter K, Clauss WG, Fronius M. Evidence for basolateral Cl- channels as modulators of apical Cl- secretion in pulmonary epithelia of Xenopus laevis. Am J Physiol Regul Integr Comp Physiol 2010; 300:R616-23. [PMID: 21123756 DOI: 10.1152/ajpregu.00464.2010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pulmonary epithelia of air-breathing vertebrates are covered by a thin, fluid layer that is essential for immune defense and gas diffusion. The composition of this layer is maintained by ion transport mechanisms, including Cl(-) transport. The present study focuses on the function of basolateral Cl(-) channels in Xenopus pulmonary epithelia, since knowledge concerning this issue is limited. Therefore, Ussing chamber measurements were performed, and transepithelial short-circuit currents (I(SC)) were monitored. Basolateral application of the Cl(-) channel inhibitor N-phenylanthranilic acid (DPC) resulted in an increase of the I(SC), indicating a DPC-sensitive Cl(-) conductance. This observation was confirmed in experiments using an apical-to-basolateral Cl(-) gradient, with and without nystatin (apical side) to permeabilize the epithelia as well as by establishing an iodide gradient. The DPC-sensitive Cl(-) conductance was influenced by procedures interfering with apical Cl(-) secretion. For example, the effect of forskolin was increased when basolateral Cl(-) channels were blocked by the simultaneous application of DPC. Activation of apical Cl(-) secretion by forskolin/IBMX and subsequent DPC application resulted in a significantly reduced DPC effect. Accordingly, DPC led to an increased apical Cl(-) secretion estimated by an increased 5-nitro-2-(3-phenylpropylamino)benzoic acid-sensitive I(SC). Furthermore, inhibition of basolateral anion exchangers responsible for Cl(-) uptake resulted in a decreased DPC-sensitive current. Taken together, we have evidence concerning the function of basolateral Cl(-) channels in Xenopus pulmonary epithelium and that these channels play a significant role in mediating apical Cl(-) secretion involving a novel Cl(-) recycling mechanism across the basolateral membrane.
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Affiliation(s)
- Jens Berger
- Institute of Animal Physiology, Justus-Liebig Univ. Giessen, Germany
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Celedón G, González G, Lissi E, Cerda T, Bascuñant D, Lepeley M, Pazos F, Lanio ME, Alvarez C. Effect of pre-exposure of human erythrocytes to oxidants on the haemolytic activity of Sticholysin II. A comparison between peroxynitrite and hypochlorous acid. Free Radic Res 2010; 45:400-8. [DOI: 10.3109/10715762.2010.536838] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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