1
|
Yarcusko RS, Song MH, Neuger GC, Romero MF, Piermarini PM, Gillen CM. Function and regulation of the insect NaCCC2 sodium transport proteins. Comp Biochem Physiol A Mol Integr Physiol 2024; 296:111685. [PMID: 38914258 DOI: 10.1016/j.cbpa.2024.111685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 06/21/2024] [Accepted: 06/21/2024] [Indexed: 06/26/2024]
Abstract
NaCCC2 transport proteins, including those from Drosophila melanogaster (Ncc83) and Aedes aegypti (aeCCC2), are an insect-specific clade with sequence similarity to Na+-K+-2Cl- cotransporters. Whereas the Na+-K+-2Cl- cotransporters and other cation-chloride cotransporters are electroneutral, recent work indicates that Ncc83 and aeCCC2 carry charge across membranes. Here, we further characterize the regulation and transport properties of Ncc83 and aeCCC2 expressed in Xenopus oocytes. In cation uptake experiments, Li+ was used as a tracer for Na+ and Rb+ was used as a tracer for K+. Li+ uptake of oocytes expressing either aeCCC2 or Ncc83 was greater than uptake in water-injected controls, activated by hypotonic swelling, and not inhibited by ouabain or ethyl cinnamate. Rb+ uptake of oocytes expressing either aeCCC2 or Ncc83 was not different than water injected controls. In oocytes expressing either aeCCC2 or Ncc83, Li+ uptake plateaued with increasing Li+ concentrations, with apparent Km values in the range of 10 to 20 mM. Following exposure to ouabain, intracellular [Na+] was greater in oocytes expressing aeCCC2 than in controls. Elevating intracellular cAMP (via 8-bromo-cAMP) in Ncc83 oocytes significantly stimulated both Li+ uptake and membrane conductances. Elevating intracellular cAMP in aeCCC2 oocytes did not affect Li+ uptake, but stimulated membrane conductances. Overall, these results confirm that the NaCCC2s resemble other cation-chloride cotransporters in their regulation and some transport properties. However, unlike other cation-chloride cotransporters, they carry charge across membranes.
Collapse
Affiliation(s)
- Ryan S Yarcusko
- Department of Biology, Kenyon College, Gambier, OH 43050, USA
| | | | - Grace C Neuger
- Department of Biology, Kenyon College, Gambier, OH 43050, USA
| | - Michael F Romero
- Physiology and Biomedical Engineering, Mayo Clinic College of Medicine and Science, Rochester, MN 55902, USA
| | - Peter M Piermarini
- Department of Entomology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster, OH 44691, USA
| | | |
Collapse
|
2
|
Seldeslachts A, Peigneur S, Tytgat J. Histamine Receptors: Ex Vivo Functional Studies Enabling the Discovery of Hits and Pathways. MEMBRANES 2023; 13:897. [PMID: 38132901 PMCID: PMC10744718 DOI: 10.3390/membranes13120897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 11/23/2023] [Accepted: 11/24/2023] [Indexed: 12/23/2023]
Abstract
Histamine receptors (HRs) are G-protein-coupled receptors involved in diverse responses triggered by histamine release during inflammation or by encounters with venomous creatures. Four histamine receptors (H1R-H4R) have been cloned and extensively characterized. These receptors are distributed throughout the body and their activation is associated with clinical manifestations such as urticaria (H1R), gastric acid stimulation (H2R), regulation of neurotransmitters in neuronal diseases (H3R), and immune responses (H4R). Despite significant homologous overlap between H3R and H4R, much remains unknown about their precise roles. Even though some drugs have been developed for H1R, H2R, and H3R, not a single H4R antagonist has been approved for clinical use. To enhance our understanding and advance innovative therapeutic targeting of H1R, H2R, H3R, and H4R, we established a robust ex vivo functional platform. This platform features the successful heterologous expression of H1R-H4R in Xenopus laevis oocytes, utilizing an electrophysiological readout. Our findings contribute to a deeper understanding of the function and pharmacological properties of the histamine receptors. Researchers can benefit from the utility of this platform when investigating the effects of histamine receptors and exploring potential therapeutic targets. In doing so, it broadens the horizon of drug discovery, offering new perspectives for therapeutic interventions.
Collapse
Affiliation(s)
| | - Steve Peigneur
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium;
| | - Jan Tytgat
- Toxicology and Pharmacology, KU Leuven, Campus Gasthuisberg, O&N2, Herestraat 49, P.O. Box 922, 3000 Leuven, Belgium;
| |
Collapse
|
3
|
Stanchev LD, Møller-Hansen I, Lojko P, Rocha C, Borodina I. Screening of Saccharomyces cerevisiae metabolite transporters by 13C isotope substrate labeling. Front Microbiol 2023; 14:1286597. [PMID: 38116525 PMCID: PMC10729909 DOI: 10.3389/fmicb.2023.1286597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/10/2023] [Indexed: 12/21/2023] Open
Abstract
The transportome of Saccharomyces cerevisiae comprises approximately 340 membrane-bound proteins, of which very few are well-characterized. Elucidating transporter proteins' function is essential not only for understanding central cellular processes in metabolite exchange with the external milieu but also for optimizing the production of value-added compounds in microbial cell factories. Here, we describe the application of 13C-labeled stable isotopes and detection by targeted LC-MS/MS as a screening tool for identifying Saccharomyces cerevisiae metabolite transporters. We compare the transport assay's sensitivity, reproducibility, and accuracy in yeast transporter mutant cell lines and Xenopus oocytes. As proof of principle, we analyzed the transport profiles of five yeast amino acid transporters. We first cultured yeast transporter deletion or overexpression mutants on uniformly labeled 13C-glucose and then screened their ability to facilitate the uptake or export of an unlabeled pool of amino acids. Individual transporters were further studied by heterologous expression in Xenopus oocytes, followed by an uptake assay with 13C labeled yeast extract. Uptake assays in Xenopus oocytes showed higher reproducibility and accuracy. Although having lower accuracy, the results from S. cerevisiae indicated the system's potential for initial high-throughput screening for native metabolite transporters. We partially confirmed previously reported substrates for all five amino acid transporters. In addition, we propose broader substrate specificity for two of the transporter proteins. The method presented here demonstrates the application of a comprehensive screening platform for the knowledge expansion of the transporter-substrate relationship for native metabolites in S. cerevisiae.
Collapse
Affiliation(s)
| | | | | | | | - Irina Borodina
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| |
Collapse
|
4
|
Fehsenfeld S, Quijada-Rodriguez AR, Zhouyao H, Durant AC, Donini A, Sachs M, Eck P, Weihrauch D. Hiat1 as a new transporter involved in ammonia regulation. Sci Rep 2023; 13:4416. [PMID: 36932112 PMCID: PMC10023664 DOI: 10.1038/s41598-023-31503-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
The orphan transporter hippocampus-abundant transcript 1 (Hiat1) was first identified in the mammalian brain. Its specific substrate specificity, however, has not been investigated to date. Here, we identified and analyzed Hiat1 in a crustacean, the green crab Carcinus maenas. Our phylogenetic analysis showed that Hiat1 protein is conserved at a considerable level between mammals and this invertebrate (ca. 78% identical and conserved amino acids). Functional expression of Carcinus maenas Hiat1 in Xenopus laevis oocytes demonstrated the capability to transport ammonia (likely NH4+) in a sodium-dependent manner. Furthermore, applying quantitative polymerase chain reaction, our results indicated a physiological role for Carcinus maenas Hiat1 in ammonia homeostasis, as mRNA abundance increased in posterior gills in response to elevated circulating hemolymph ammonia upon exposure to high environmental ammonia. Its ubiquitous mRNA expression pattern also suggests an essential role in general cellular detoxification of ammonia. Overall, our results introduce a new ubiquitously expressed ammonia transporter, consequently demanding revision of our understanding of ammonia handling in key model systems from mammalian kidneys to crustacean and fish gills.
Collapse
Affiliation(s)
- Sandra Fehsenfeld
- Département de Biologie, Chimie et Géographie, Université du Quebec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, G5L 3A1, Canada.
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada.
| | - Alex R Quijada-Rodriguez
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
| | - Haonan Zhouyao
- Department of Food and Human Nutritional Sciences, University of Manitoba, 35 Chancellor's Circle, Winnipeg, MB, R3T 2N2, Canada
| | - Andrea C Durant
- Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
- Department of Biological Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada
| | - Andrew Donini
- Department of Biology, York University, 4700 Keele St, Toronto, ON, M3J 1P3, Canada
| | - Maria Sachs
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
| | - Peter Eck
- Department of Food and Human Nutritional Sciences, University of Manitoba, 35 Chancellor's Circle, Winnipeg, MB, R3T 2N2, Canada
| | - Dirk Weihrauch
- Department of Biological Sciences, University of Manitoba, 50 Sifton Road, Winnipeg, MB, R3T 2N2, Canada
| |
Collapse
|
5
|
Bernareggi A, Zangari M, Constanti A, Zacchi P, Borelli V, Mangogna A, Lorenzon P, Zabucchi G. Asbestos Fibers Enhance the TMEM16A Channel Activity in Xenopus Oocytes. MEMBRANES 2023; 13:180. [PMID: 36837683 PMCID: PMC9960392 DOI: 10.3390/membranes13020180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/24/2023] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND The interaction of asbestos fibers with target cell membranes is still poorly investigated. Here, we detected and characterized an enhancement of chloride conductance in Xenopus oocyte cell membranes induced by exposure to crocidolite (Croc) asbestos fibers. METHODS A two-microelectrode voltage clamp technique was used to test the effect of Croc fiber suspensions on outward chloride currents evoked by step membrane depolarization. Calcium imaging experiments were also performed to investigate the variation of 'resting' oocyte [Ca2+]i following asbestos exposure. RESULTS The increase in chloride current after asbestos treatment, was sensitive to [Ca2+]e, and to specific blockers of TMEM16A Ca2+-activated chloride channels, MONNA and Ani9. Furthermore, asbestos treatment elevated the 'resting' [Ca2+]i likelihood by increasing the cell membrane permeability to Ca2 in favor of a tonic activation of TMEME16A channels. Western blot analysis confirmed that TMEME16A protein was endogenously present in the oocyte cell membrane and absorbed by Croc. CONCLUSION the TMEM16A channels endogenously expressed by Xenopus oocytes are targets for asbestos fibers and represent a powerful tool for asbestos-membrane interaction studies. Interestingly, TMEM16A channels are highly expressed in many types of tumors, including some asbestos-related cancers, suggesting them, for the first time, as a possible early target of crocidolite-mediated tumorigenic effects on target cell membranes.
Collapse
Affiliation(s)
- Annalisa Bernareggi
- Department of Life Sciences, University of Trieste, Via Fleming 22, 34127 Trieste, Italy
| | - Martina Zangari
- Department of Life Sciences, University of Trieste, Via Fleming 22, 34127 Trieste, Italy
| | - Andrew Constanti
- Department of Pharmacology, UCL School of Pharmacy, 29/39 Brunswick Square, London WC1N 1AX, UK
| | - Paola Zacchi
- Department of Life Sciences, University of Trieste, Via Valerio 28/1, 34127 Trieste, Italy
| | - Violetta Borelli
- Department of Life Sciences, University of Trieste, Via Valerio 28/1, 34127 Trieste, Italy
| | - Alessandro Mangogna
- Institute for Maternal and Child Health—IRCCS Burlo Garofolo, Via Dell’Istria 65/1, 34137 Trieste, Italy
| | - Paola Lorenzon
- Department of Life Sciences, University of Trieste, Via Fleming 22, 34127 Trieste, Italy
| | - Giuliano Zabucchi
- Department of Life Sciences, University of Trieste, Via Valerio 28/1, 34127 Trieste, Italy
| |
Collapse
|
6
|
Ivorra I, Alberola-Die A, Cobo R, González-Ros JM, Morales A. Xenopus Oocytes as a Powerful Cellular Model to Study Foreign Fully-Processed Membrane Proteins. MEMBRANES 2022; 12:986. [PMID: 36295745 PMCID: PMC9610954 DOI: 10.3390/membranes12100986] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 06/16/2023]
Abstract
The use of Xenopus oocytes in electrophysiological and biophysical research constitutes a long and successful story, providing major advances to the knowledge of the function and modulation of membrane proteins, mostly receptors, ion channels, and transporters. Earlier reports showed that these cells are capable of correctly expressing heterologous proteins after injecting the corresponding mRNA or cDNA. More recently, the Xenopus oocyte has become an outstanding host-cell model to carry out detailed studies on the function of fully-processed foreign membrane proteins after their microtransplantation to the oocyte. This review focused on the latter overall process of transplanting foreign membrane proteins to the oocyte after injecting plasma membranes or purified and reconstituted proteins. This experimental approach allows for the study of both the function of mature proteins, with their native stoichiometry and post-translational modifications, and their putative modulation by surrounding lipids, mostly when the protein is purified and reconstituted in lipid matrices of defined composition. Remarkably, this methodology enables functional microtransplantation to the oocyte of membrane receptors, ion channels, and transporters from different sources including human post-mortem tissue banks. Despite the large progress achieved over the last decades on the structure, function, and modulation of neuroreceptors and ion channels in healthy and pathological tissues, many unanswered questions remain and, most likely, Xenopus oocytes will continue to help provide valuable responses.
Collapse
Affiliation(s)
- Isabel Ivorra
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Armando Alberola-Die
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - Raúl Cobo
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| | - José Manuel González-Ros
- Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche (IDiBE), Universidad Miguel Hernández, E-03202 Elche, Spain
| | - Andrés Morales
- Departamento de Fisiología, Genética y Microbiología, Universidad de Alicante, Apdo 99, E-03080 Alicante, Spain
| |
Collapse
|
7
|
Bhatt M, Di Iacovo A, Romanazzi T, Roseti C, Cinquetti R, Bossi E. The "www" of Xenopus laevis Oocytes: The Why, When, What of Xenopus laevis Oocytes in Membrane Transporters Research. MEMBRANES 2022; 12:membranes12100927. [PMID: 36295686 PMCID: PMC9610376 DOI: 10.3390/membranes12100927] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 05/16/2023]
Abstract
After 50 years, the heterologous expression of proteins in Xenopus laevis oocytes is still essential in many research fields. New approaches and revised protocols, but also classical methods, such as the two-electrode voltage clamp, are applied in studying membrane transporters. New and old methods for investigating the activity and the expression of Solute Carriers (SLC) are reviewed, and the kinds of experiment that are still useful to perform with this kind of cell are reported. Xenopus laevis oocytes at the full-grown stage have a highly efficient biosynthetic apparatus that correctly targets functional proteins at the defined compartment. This small protein factory can produce, fold, and localize almost any kind of wild-type or recombinant protein; some tricks are required to obtain high expression and to verify the functionality. The methodologies examined here are mainly related to research in the field of membrane transporters. This work is certainly not exhaustive; it has been carried out to be helpful to researchers who want to quickly find suggestions and detailed indications when investigating the functionality and expression of the different members of the solute carrier families.
Collapse
Affiliation(s)
- Manan Bhatt
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Angela Di Iacovo
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Tiziana Romanazzi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Cristina Roseti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
| | - Raffaella Cinquetti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
| | - Elena Bossi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
- Correspondence:
| |
Collapse
|
8
|
Tyerman SD, McGaughey SA, Qiu J, Yool AJ, Byrt CS. Adaptable and Multifunctional Ion-Conducting Aquaporins. ANNUAL REVIEW OF PLANT BIOLOGY 2021; 72:703-736. [PMID: 33577345 DOI: 10.1146/annurev-arplant-081720-013608] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Aquaporins function as water and neutral solute channels, signaling hubs, disease virulence factors, and metabolon components. We consider plant aquaporins that transport ions compared to some animal counterparts. These are candidates for important, as yet unidentified, cation and anion channels in plasma, tonoplast, and symbiotic membranes. For those individual isoforms that transport ions, water, and gases, the permeability spans 12 orders of magnitude. This requires tight regulation of selectivity via protein interactions and posttranslational modifications. A phosphorylation-dependent switch between ion and water permeation in AtPIP2;1 might be explained by coupling between the gates of the four monomer water channels and the central pore of the tetramer. We consider the potential for coupling between ion and water fluxes that could form the basis of an electroosmotic transducer. A grand challenge in understanding the roles of ion transporting aquaporins is their multifunctional modes that are dependent on location, stress, time, and development.
Collapse
Affiliation(s)
- Stephen D Tyerman
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Samantha A McGaughey
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
| | - Jiaen Qiu
- Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Glen Osmond, South Australia 5064, Australia; ,
| | - Andrea J Yool
- Adelaide Medical School, University of Adelaide, Adelaide, South Australia 5005, Australia;
| | - Caitlin S Byrt
- ARC Centre of Excellence for Translational Photosynthesis, Division of Plant Sciences, Research School of Biology, Australian National University, Acton, Australian Capital Territory 0200, Australia; ,
| |
Collapse
|
9
|
Fairweather SJ, Okada S, Gauthier-Coles G, Javed K, Bröer A, Bröer S. A GC-MS/Single-Cell Method to Evaluate Membrane Transporter Substrate Specificity and Signaling. Front Mol Biosci 2021; 8:646574. [PMID: 33928121 PMCID: PMC8076599 DOI: 10.3389/fmolb.2021.646574] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 02/17/2021] [Indexed: 12/18/2022] Open
Abstract
Amino acid transporters play a vital role in metabolism and nutrient signaling pathways. Typically, transport activity is investigated using single substrates and competing amounts of other amino acids. We used GC-MS and LC-MS for metabolic screening of Xenopus laevis oocytes expressing various human amino acid transporters incubated in complex media to establish their comprehensive substrate profiles. For most transporters, amino acid selectivity matched reported substrate profiles. However, we could not detect substantial accumulation of cationic amino acids by SNAT4 and ATB0,+ in contrast to previous reports. In addition, comparative substrate profiles of two related sodium neutral amino acid transporters known as SNAT1 and SNAT2, revealed the latter as a significant leucine accumulator. As a consequence, SNAT2, but not SNAT1, was shown to be an effective activator of the eukaryotic cellular growth regulator mTORC1. We propose, that metabolomic profiling of membrane transporters in Xe nopus laevis oocytes can be used to test their substrate specificity and role in intracellular signaling pathways.
Collapse
Affiliation(s)
- Stephen J. Fairweather
- Research School of Biology, Australian National University, Canberra, ACT, Australia
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
| | - Shoko Okada
- Commonwealth Scientific and Industrial Research Institute (CSIRO) Land and Water, Canberra, ACT, Australia
| | | | - Kiran Javed
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Angelika Bröer
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Stefan Bröer
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| |
Collapse
|
10
|
Huang KM, Uddin ME, DiGiacomo D, Lustberg MB, Hu S, Sparreboom A. Role of SLC transporters in toxicity induced by anticancer drugs. Expert Opin Drug Metab Toxicol 2020; 16:493-506. [PMID: 32276560 DOI: 10.1080/17425255.2020.1755253] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION . Membrane transporters are integral to the maintenance of cellular integrity of all tissue and cell types. While transporters play an established role in the systemic pharmacokinetics of therapeutic drugs, tissue specific expression of uptake transporters can serve as an initiating mechanism that governs the accumulation and impact of cytotoxic drugs. AREAS COVERED . This review provides an overview of organic cation transporters as determinants of chemotherapy-induced toxicities. We also provide insights into the recently updated FDA guidelines for in vitro drug interaction studies, with a particular focus on the class of tyrosine kinase inhibitors as perpetrators of transporter-mediated drug interactions. EXPERT OPINION . Studies performed over the last few decades have highlighted the important role of basolateral uptake and apical efflux transporters in the pathophysiology of drug-induced organ damage. Increased understanding of the mechanisms that govern the accumulation of cytotoxic drugs has provided insights into the development of novel strategies to prevent debilitating toxicities. Furthermore, we argue that current regulatory guidelines provide inadequate recommendations for in vitro studies to identify substrates or inhibitors of drug transporters. Therefore, the translational and predictive power of FDA-approved drugs as modulators of transport function remains ambiguous and warrants further revision of the current guidelines.
Collapse
Affiliation(s)
- Kevin M Huang
- Division of Pharmaceutics and Pharmacology, College of Pharmacy and Comprehensive Cancer Center, the Ohio State University , Columbus, OH, USA
| | - Muhammad Erfan Uddin
- Division of Pharmaceutics and Pharmacology, College of Pharmacy and Comprehensive Cancer Center, the Ohio State University , Columbus, OH, USA
| | - Duncan DiGiacomo
- Division of Pharmaceutics and Pharmacology, College of Pharmacy and Comprehensive Cancer Center, the Ohio State University , Columbus, OH, USA
| | - Maryam B Lustberg
- Department of Medical Oncology, College of Medicine, the Ohio State University and Comprehensive Cancer Center , Columbus, OH, USA
| | - Shuiying Hu
- Division of Pharmaceutics and Pharmacology, College of Pharmacy and Comprehensive Cancer Center, the Ohio State University , Columbus, OH, USA
| | - Alex Sparreboom
- Division of Pharmaceutics and Pharmacology, College of Pharmacy and Comprehensive Cancer Center, the Ohio State University , Columbus, OH, USA
| |
Collapse
|
11
|
Shear force modulates the activity of acid-sensing ion channels at low pH or in the presence of non-proton ligands. Sci Rep 2019; 9:6781. [PMID: 31043630 PMCID: PMC6494901 DOI: 10.1038/s41598-019-43097-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 04/16/2019] [Indexed: 12/17/2022] Open
Abstract
Acid-sensing ion channels (ASICs) belong to the degenerin/epithelial sodium channel protein family that form mechanosensitive ion channels. Evidence as to whether or not ASICs activity is directly modulated by mechanical force is lacking. Human ASICs (hASIC1V3, hASIC2a and hASIC3a) were heterologously expressed as homomeric channels in Xenopus oocytes and two-electrode voltage-clamp recordings were performed. hASIC3a was expressed in HEK-293 cells and currents measured by whole-cell patch-clamp recordings. ASIC currents in response to shear force (SF) were measured at pH 7.4, acidic pH, or in the presence of non-proton ligands at pH 7.4. SF was applied via a fluid stream generated through a pressurized perfusion system. No effect was observed at pH 7.4. Increased transient currents for each homomeric channel were observed when elevated SF was applied in conjunction with acidic pH (6.0-4.0). The sustained current was not (hASIC2a) or only slightly increased (hASIC1V3 and hASIC3a). SF-induced effects were not seen in water injected oocytes and were blocked by amiloride. Non-proton ligands activated a persistent current in hASIC1V3 and cASIC1 (MitTx) and hASIC3a (GMQ) at pH 7.4. Here SF caused a further current increase. Results suggest that ASICs do have an intrinsic ability to respond to mechanical force, supporting their role as mechanosensors in certain local environments.
Collapse
|
12
|
Engineered Passive Potassium Conductance in the KR2 Sodium Pump. Biophys J 2019; 116:1941-1951. [PMID: 31036257 DOI: 10.1016/j.bpj.2019.04.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 03/31/2019] [Accepted: 04/03/2019] [Indexed: 11/23/2022] Open
Abstract
Light-driven sodium pumps (NaRs) are microbial rhodopsins that utilize light energy to actively transport sodium ions out of the cell. Here, we used targeted mutagenesis and electrophysiological methods in living cells to demonstrate that NaRs can be converted into light-activated cation channels by molecular engineering. Specifically, introduction of the R109Q mutation into the sodium ion pump of Dokdonia eikasta (KR2) results in passive ion conductance, with a high preference for potassium over sodium ions. However, in this mutant, residual active outward pumping of sodium ions competes with passive inward transport of potassium. Channel-like behavior could also be achieved by introduction of other mutations into the KR2 counterion complex, and further, these modifications were transferrable to other NaRs. Combining the R109Q replacement with modifications at position S70 removed the residual sodium pumping and greatly enhanced the channel-like activity. However, passive photocurrents were only observed in leak mutants if the KR2 counterions, D116 and D251, were deprotonated, which was only observed under alkaline conditions. Overall, our results reveal that interactions between R109 and the nearby residues, L75, S70, D116, and D251, prevent passive backflow during ion transport in NaRs.
Collapse
|
13
|
Sanz A, Pike S, Khan MA, Carrió-Seguí À, Mendoza-Cózatl DG, Peñarrubia L, Gassmann W. Copper uptake mechanism of Arabidopsis thaliana high-affinity COPT transporters. PROTOPLASMA 2019; 256:161-170. [PMID: 30043153 DOI: 10.1007/s00709-018-1286-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 07/11/2018] [Indexed: 05/24/2023]
Abstract
Copper (Cu) is an essential plant micronutrient. Under scarcity, Cu2+ is reduced to Cu+ and taken up through specific high-affinity transporters (COPTs). In Arabidopsis, the COPT family consists of six members, either located at the plasma membrane (COPT1, COPT2, and COPT6) or in internal membranes (COPT3 and COPT5). Cu uptake by COPT proteins has been mainly assessed through complementation studies in corresponding yeast mutants, but the mechanism of this transport has not been elucidated. To test whether Cu is incorporated by an electrogenic mechanism, electrophysiological changes induced by Cu addition were studied in Arabidopsis thaliana. Mutant (T-DNA insertion mutants, copt2-1 and copt5-2) and overexpressing lines (COPT1OE and COPT5OE) with altered expression of COPT transporters were compared to wild-type plants. No significant changes of the membrane potential (Em) were detected, regardless of genotype or Cu concentration supplied. In contrast, membrane depolarization was detected in response to iron supply in both wild-type and in mutant or transgenic plants. Similar results were obtained for trans-plant potentials (TPP). GFP fusions of the plasma membrane COPT2 and the internal COPT5 transporters were expressed in Xenopus laevis oocytes to potentiate Cu uptake signals, and the cRNA-injected oocytes were tested for electrical currents upon Cu addition using two-electrode voltage clamp. Results with oocytes confirmed those obtained in plants. Cu accumulation in injected oocytes was measured by ICP-OES, and a significant increase in Cu content with respect to controls occurred in oocytes expressing COPT2:GFP. The possible mechanisms driving this transport are discussed in this manuscript.
Collapse
Affiliation(s)
- Amparo Sanz
- Dpt de Biologia Vegetal, Universitat de València, c/ Dr Moliner 50, 46100-Burjassot, Valencia, Spain.
| | - Sharon Pike
- Division of Plant Sciences, CS Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, 1201 Rollins St, Columbia, MO, 65211, USA
| | - Mather A Khan
- Division of Plant Sciences, CS Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, 1201 Rollins St, Columbia, MO, 65211, USA
| | - Àngela Carrió-Seguí
- Dpt de Bioquímica i Biologia Molecular and ERI Biotecmed, Universitat de València, c/ Dr Moliner 50, 46100-Burjassot, Valencia, Spain
| | - David G Mendoza-Cózatl
- Division of Plant Sciences, CS Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, 1201 Rollins St, Columbia, MO, 65211, USA
| | - Lola Peñarrubia
- Dpt de Bioquímica i Biologia Molecular and ERI Biotecmed, Universitat de València, c/ Dr Moliner 50, 46100-Burjassot, Valencia, Spain
| | - Walter Gassmann
- Division of Plant Sciences, CS Bond Life Sciences Center, and Interdisciplinary Plant Group, University of Missouri, 1201 Rollins St, Columbia, MO, 65211, USA
| |
Collapse
|
14
|
Franz MC, Pujol-Giménez J, Montalbetti N, Fernandez-Tenorio M, DeGrado TR, Niggli E, Romero MF, Hediger MA. Reassessment of the Transport Mechanism of the Human Zinc Transporter SLC39A2. Biochemistry 2018; 57:3976-3986. [PMID: 29791142 DOI: 10.1021/acs.biochem.8b00511] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The human zinc transporter SLC39A2, also known as ZIP2, was shown to mediate zinc transport that could be inhibited at pH <7.0 and stimulated by HCO3-, suggesting a Zn2+/HCO3- cotransport mechanism [Gaither, L. A., and Eide, D. J. (2000) J. Biol. Chem. 275, 5560-5564]. In contrast, recent experiments in our laboratory indicated that the functional activity of ZIP2 increases at acidic pH [Franz, M. C., et al. (2014) J. Biomol. Screening 19, 909-916]. The study presented here was therefore designed to reexamine the findings about the pH dependence and to extend the functional characterization of ZIP2. Our current results show that ZIP2-mediated transport is modulated by extracellular pH but independent of the H+ driving force. Also, in our experiments, ZIP2-mediated transport is not modulated by extracellular HCO3-. Moreover, a high extracellular [K+], which induces depolarization, inhibited ZIP2-mediated transport, indicating that the transport mechanism is voltage-dependent. We also show that ZIP2 mediates the uptake of Cd2+ ( Km ∼ 1.57 μM) in a pH-dependent manner ( KH+ ∼ 66 nM). Cd2+ transport is inhibited by extracellular [Zn2+] (IC50 ∼ 0.32 μM), [Cu2+] (IC50 ∼ 1.81 μM), and to a lesser extent [Co2+], but not by [Mn2+] or [Ba2+]. Fe2+ is not transported by ZIP2. Accordingly, the substrate selectivity of ZIP2 decreases in the following order: Zn2+ > Cd2+ ≥ Cu2+ > Co2+. Altogether, we propose that ZIP2 is a facilitated divalent metal ion transporter that can be modulated by extracellular pH and membrane potential. Given that ZIP2 expression has been reported in acidic environments [Desouki, M. M., et al. (2007) Mol. Cancer 6, 37; Inoue, Y., et al. (2014) J. Biol. Chem. 289, 21451-21462; Tao, Y. T., et al. (2013) Mol. Biol. Rep. 40, 4979-4984], we suggest that the herein described H+-mediated regulatory mechanism might be important for determining the velocity and direction of the transport process.
Collapse
Affiliation(s)
- Marie C Franz
- University of Bern , Institute of Biochemistry and Molecular Medicine, and National Center of Competence in Research, NCCR TransCure , Bühlstrasse 28 , 3012 Bern , Switzerland
| | - Jonai Pujol-Giménez
- University of Bern , Institute of Biochemistry and Molecular Medicine, and National Center of Competence in Research, NCCR TransCure , Bühlstrasse 28 , 3012 Bern , Switzerland
| | - Nicolas Montalbetti
- University of Bern , Institute of Biochemistry and Molecular Medicine, and National Center of Competence in Research, NCCR TransCure , Bühlstrasse 28 , 3012 Bern , Switzerland
| | | | - Timothy R DeGrado
- Department of Physiology and Biomedical Engineering , Mayo Clinic College of Medicine and Science , Rochester , Minnesota 55905 , United States
| | - Ernst Niggli
- University of Bern , Department of Physiology , Buehlplatz 5 , 3012 Bern , Switzerland
| | - Michael F Romero
- Department of Physiology and Biomedical Engineering , Mayo Clinic College of Medicine and Science , Rochester , Minnesota 55905 , United States
| | - Matthias A Hediger
- University of Bern , Institute of Biochemistry and Molecular Medicine, and National Center of Competence in Research, NCCR TransCure , Bühlstrasse 28 , 3012 Bern , Switzerland
| |
Collapse
|
15
|
Zhang J, Mohamad FH, Wong JH, Mohamad H, Ismail AH, Mohamed Yusoff AA, Osman H, Wong KT, Idris Z, Abdullah JM. The Effects of 4-Hydroxybenzoic Acid Identified from Bamboo ( Dendrocalamus asper) Shoots on Kv1.4 Channel. Malays J Med Sci 2018; 25:101-113. [PMID: 29599640 DOI: 10.21315/mjms2018.25.1.12] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Accepted: 12/30/2017] [Indexed: 10/17/2022] Open
Abstract
Background Bamboo shoot has been used as a treatment for epilepsy in traditional Chinese medicine for generations to treat neuronal disorders such as convulsive, dizziness and headaches. 4-hydroxybenzoic acid (4-hba) is a non-flavonoid phenol found abundantly in Dendrocalamus asper shoots (bamboo), fruits (strawberries and apples) and flowers. Kv1.4 is a rapidly inactivating Shaker-related member of the voltage-gated potassium channels with two inactivation mechanisms; the fast N-type and slow C-type. It plays vital roles in repolarisation, hyperpolarisation and signaling the restoration of resting membrane potential through the regulation of the movement of K+ across the cellular membrane. Methods Chemical compounds from Dendrocalamus asper bamboo shoots were purified and identified as major palmitic acids mixed with other minor fatty acids, palmitic acid, 4-hydroxybenzaldehyde, lauric acid, 4-hydroxybenzoic acid and cholest-4-ene-3-one. The response of synthetic 4-hydroxybenzoic acid was tested on Kv1.4 potassium channel which was injected into viable oocytes that was extracted from Xenopus laevis. The current were detected by the two-microelectrode voltage clamp, holding potential starting from -80 mV with 20 mV step-up until +80 mV. Readings of treatments with 0.1% DMSO, 4-hba concentrations and K channel blockers were taken at +60 mV. The ratio of tail/peak amplitude is the index of the activity of the Kv1.4 channels with n ≥ 6 (number of oocytes tested). The decreases of the ratios of five different concentrations (1 μM, 10 μM, 100 μM, 1 mM and 2.5 mM) were compared with 0.1% DMSO as the control. Results All concentration showed statistically significant results with P < 0.05 except for 100 μM. The normalised current of the 4-hba concentrations were compared with potassium channel blockers (TEA and 4-AP) and all groups showed statistically significant results. This study also showed that time taken for each concentration to affect Kv1.4 does not play any significant roles. Conclusion 4-hydroxybenzoic acid was found to be able to enhance the inactivation of Kv1.4 by lowering the membrane potential so that the abnormal neuronal firing can be inhibited. With IC50 slightly higher than 10 μM, increasing concentrations (100 μM, 1 mM and 2.5 mM) had shown to exhibit toxicity effects. The best concentration from this study is 10 μM with Hill slope of 0.1799.
Collapse
Affiliation(s)
- Jingli Zhang
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Fatin H Mohamad
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Jia Hui Wong
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Habsah Mohamad
- Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia
| | - Abdul Hadi Ismail
- Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia
| | - Abdul Aziz Mohamed Yusoff
- Center for Neuroscience Services and Research, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.,Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Hasnah Osman
- School of Chemical Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia
| | - Kok Tong Wong
- School of Chemical Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia
| | - Zamzuri Idris
- Center for Neuroscience Services and Research, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.,Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.,Department of Neurosciences, Hospital Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Jafri Malin Abdullah
- Center for Neuroscience Services and Research, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.,Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia.,Department of Neurosciences, Hospital Universiti Sains Malaysia, Jalan Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
| |
Collapse
|
16
|
A Molecular Basis for the Inhibition of Transient Receptor Potential Vanilloid Type 1 by Gomisin A. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2017; 2017:6451905. [PMID: 29234417 PMCID: PMC5684552 DOI: 10.1155/2017/6451905] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 08/02/2017] [Indexed: 11/18/2022]
Abstract
Transient receptor potential (TRP) channel has critical actions as conditional sensors in primary afferent neurons. We studied the regulatory action of gomisin A on TRPV1 channel current in this report. Schisandra chinensis contains bioactive compounds such as the gomisin derivatives and their related compounds. Coapplication with gomisin A inhibited the capsaicin-mediated inward peak current. This inhibitory effect of gomisin A on capsaicin-induced inward current showed concentration-dependence and was reversible. The half maximal inhibitory concentration of gomisin A was 62.7 ± 8.4 µM. In addition, this inhibition occurred in a noncompetition regulation mode and voltage insensitive manner. Furthermore, molecular docking studies of gomisin A on TRPV1 showed that it interacted predominantly with residues at cavities in the segments 1 and 2 of each subunit. Four potential binding sites for this ligand in the extracellular region at sensor domain of TRPV1 channel were identified. Point mutagenesis studies were undertaken, and gomisin A potency decreased for both the Y453A and N467A mutants. The double mutation of Y453 and N467 significantly attenuated inhibitory effects by gomisin A. In summary, this study revealed the molecular basis for the interaction between TRPV1 and gomisin A and provides a novel potent interaction ligand.
Collapse
|
17
|
Carvalho S, Molina-López J, Parsons D, Corpe C, Maret W, Hogstrand C. Differential cytolocation and functional assays of the two major human SLC30A8 (ZnT8) isoforms. J Trace Elem Med Biol 2017; 44:116-124. [PMID: 28965566 DOI: 10.1016/j.jtemb.2017.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Revised: 06/02/2017] [Accepted: 06/06/2017] [Indexed: 11/22/2022]
Abstract
The non-synonymous single nucleotide polymorphism (SNP) rs13266634 in human zinc transporter 8, ZnT8 (SLC30A8), leads to a R325 variant, which is associated with an increased risk of developing Type 2 Diabetes (T2D). Although the molecular details remain unknown, the mutation is thought to alter the kinetics of zinc transport into insulin granules in pancreatic β-cells. Nevertheless, analysis of ZnT8 sequences from several animals shows that the amino acid at position 325 is poorly conserved. Apart from this particular SNP, human ZnT8 also has two isoforms (splice variants) that differ in length regarding a 49 amino acid N-terminal extension. When expressed in human embryonic kidney (HEK293) cells, the long isoform was present in the plasma membrane in addition to internal membranes, whereas the short isoform was localized mostly to internal membranes. Our observation that human ZnT8 variants and isoforms expressed in Xenopus laevis oocytes are all localized at the cell surface allowed us to develop a zinc transport assay using the radioactive isotope 65Zn. We found no detectable differences in zinc transport between W and R variants and no statistically significant differences between long and short isoforms of the W325 variant. Our findings of differential cytolocation of ZnT8 isoforms could be relevant for β-cell zinc metabolism in health and disease.
Collapse
Affiliation(s)
- Sandra Carvalho
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Jorge Molina-López
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK; Department of Physiology, Institute of Nutrition and Food Technology "José Mataix", University of Granada, Spain
| | - Douglas Parsons
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Christopher Corpe
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK
| | - Wolfgang Maret
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK.
| | - Christer Hogstrand
- Diabetes and Nutritional Sciences Division, Faculty of Life Sciences and Medicine, King's College London, London, UK
| |
Collapse
|
18
|
Paiz-Candia B, Islas AA, Sánchez-Solano A, Mancilla-Simbro C, Scior T, Millan-PerezPeña L, Salinas-Stefanon EM. Mefloquine inhibits voltage dependent Nav1.4 channel by overlapping the local anaesthetic binding site. Eur J Pharmacol 2017; 796:215-223. [DOI: 10.1016/j.ejphar.2017.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 12/21/2016] [Accepted: 01/02/2017] [Indexed: 10/20/2022]
|
19
|
Characterization of specific allosteric effects of the Na+ channel β1 subunit on the Nav1.4 isoform. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2016; 46:485-494. [DOI: 10.1007/s00249-016-1193-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 11/23/2016] [Accepted: 11/30/2016] [Indexed: 11/26/2022]
|
20
|
Myers EJ, Yuan L, Felmlee MA, Lin YY, Jiang Y, Pei Y, Wang O, Li M, Xing XP, Marshall A, Xia WB, Parker MD. A novel mutant Na + /HCO3 - cotransporter NBCe1 in a case of compound-heterozygous inheritance of proximal renal tubular acidosis. J Physiol 2016; 594:6267-6286. [PMID: 27338124 DOI: 10.1113/jp272252] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/08/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The inheritance of two defective alleles of SLC4A4, the gene that encodes the widely-expressed electrogenic sodium bicarbonate cotransporter NBCe1, results in the bicarbonate-wasting disease proximal renal tubular acidosis (pRTA). In the present study, we report the first case of compound-heterozygous inheritance of pRTA (p.Arg510His/p.Gln913Arg) in an individual with low blood pH, blindness and neurological signs that resemble transient ischaemic attacks. We employ fluorescence microscopy on non-polarized (human embryonic kidney) and polarized (Madin-Darby canine kidney) renal cell lines and electrophysiology on Xenopus oocytes to characterize the mutant transporters (R510H and Q913R). Both mutant transporters exhibit enhanced intracellular retention in renal cells, an observation that probably explains the HCO3- transport deficit in the individual. Both mutants retain a close-to-normal per molecule Na+ /HCO3- cotransport activity in Xenopus oocytes, suggesting that they are suitable candidates for folding-correction therapy. However, Q913R expression is uniquely associated with a depolarizing, HCO3- independent, Cl- -conductance in oocytes that could have pathological consequences if expressed in the cells of patients. ABSTRACT Proximal renal tubular acidosis (pRTA) is a rare, recessively-inherited disease characterized by abnormally acidic blood, blindness, as well as below average height and weight. pRTA is typically associated with homozygous mutation of the solute carrier 4 family gene SLC4A4. SLC4A4 encodes the electrogenic sodium bicarbonate cotransporter NBCe1, a membrane protein that acts to maintain intracellular and plasma pH. We present the first description of a case of compound-heterozygous inheritance of pRTA. The individual has inherited two mutations in NBCe1: p.Arg510His (R510H) and p.Gln913Arg (Q913R), one from each parent. In addition to the usual features of pRTA, the patient exhibits unusual signs, such as muscle spasms and fever. We have recreated these mutant transporters for expression in model systems. We find that both of the mutant proteins exhibit substantial intracellular retention when expressed in mammalian renal cell lines. When expressed in Xenopus oocytes, we find that the R510H and Q913R-mutant NBCe1 molecules exhibit apparently normal Na+ /HCO3- cotransport activity but that Q913R is associated with an unusual HCO3- independent anion-leak. We conclude that a reduced accumulation of NBCe1 protein in the basolateral membrane of proximal-tubule epithelia is the most probable cause of pRTA in this case. We further note that the Q913R-associated anion-leak could itself be pathogenic if expressed in the plasma membrane of mammalian cells, compromising the benefit of strategies aiming to enhance mutant NBCe1 accumulation in the plasma membrane.
Collapse
Affiliation(s)
- Evan J Myers
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA
| | - Lu Yuan
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Melanie A Felmlee
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA.,Department of Pharmaceutics and Medicinal Chemistry, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, California, USA
| | - Yuan-Yuan Lin
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Yan Jiang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Yu Pei
- Department of Endocrinology, Chinese People's Army General Hospital, Beijing, China
| | - Ou Wang
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Mei Li
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Xiao-Ping Xing
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Aniko Marshall
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA
| | - Wei-Bo Xia
- Department of Endocrinology, Key Laboratory of Endocrinology of Ministry of Health, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China.
| | - Mark D Parker
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA. .,Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA. .,State University of New York Eye Institutes, University at Buffalo: The State University of New York, Buffalo, New York, NY, USA.
| |
Collapse
|
21
|
Braguy J, Zurbriggen MD. Synthetic strategies for plant signalling studies: molecular toolbox and orthogonal platforms. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 87:118-38. [PMID: 27227549 DOI: 10.1111/tpj.13218] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 05/11/2016] [Accepted: 05/13/2016] [Indexed: 05/15/2023]
Abstract
Plants deploy a wide array of signalling networks integrating environmental cues with growth, defence and developmental responses. The high level of complexity, redundancy and connection between several pathways hampers a comprehensive understanding of involved functional and regulatory mechanisms. The implementation of synthetic biology approaches is revolutionizing experimental biology in prokaryotes, yeasts and animal systems and can likewise contribute to a new era in plant biology. This review gives an overview on synthetic biology approaches for the development and implementation of synthetic molecular tools and techniques to interrogate, understand and control signalling events in plants, ranging from strategies for the targeted manipulation of plant genomes up to the spatiotemporally resolved control of gene expression using optogenetic approaches. We also describe strategies based on the partial reconstruction of signalling pathways in orthogonal platforms, like yeast, animal and in vitro systems. This allows a targeted analysis of individual signalling hubs devoid of interconnectivity with endogenous interacting components. Implementation of the interdisciplinary synthetic biology tools and strategies is not exempt of challenges and hardships but simultaneously most rewarding in terms of the advances in basic and applied research. As witnessed in other areas, these original theoretical-experimental avenues will lead to a breakthrough in the ability to study and comprehend plant signalling networks.
Collapse
Affiliation(s)
- Justine Braguy
- Institute of Synthetic Biology and CEPLAS, University of Düsseldorf, Universitätstrasse 1, Building 26.12.U1.25, Düsseldorf, 40225, Germany
- King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Matias D Zurbriggen
- Institute of Synthetic Biology and CEPLAS, University of Düsseldorf, Universitätstrasse 1, Building 26.12.U1.25, Düsseldorf, 40225, Germany
| |
Collapse
|
22
|
Chen Y, Ma J, Miller AJ, Luo B, Wang M, Zhu Z, Ouwerkerk PBF. OsCHX14 is Involved in the K+ Homeostasis in Rice (Oryza sativa) Flowers. PLANT & CELL PHYSIOLOGY 2016; 57:1530-1543. [PMID: 27903806 DOI: 10.1093/pcp/pcw088] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 04/26/2016] [Indexed: 05/22/2023]
Abstract
Previously we showed in the osjar1 mutants that the lodicule senescence which controls the closing of rice flowers was delayed. This resulted in florets staying open longer when compared with the wild type. The gene OsJAR1 is silenced in osjar1 mutants and is a key member of the jasmonic acid (JA) signaling pathway. We found that K concentrations in lodicules and flowers of osjar1-2 were significantly elevated compared with the wild type, indicating that K+ homeostasis may play a role in regulating the closure of rice flowers. The cation/H+ exchanger (CHX) family from rice was screened for potential K+ transporters involved as many members of this family in Arabidopsis were exclusively or preferentially expressed in flowers. Expression profiling confirmed that among 17 CHX genes in rice, OsCHX14 was the only member that showed an expression polymorphism, not only in osjar1 mutants but also in RNAi (RNA interference) lines of OsCOI1, another key member of the JA signaling pathway. This suggests that the expression of OsCHX14 is regulated by the JA signaling pathway. Green fluorescent protein (GFP)-tagged OsCHX14 protein was preferentially localized to the endoplasmic reticulum. Promoter-β-glucuronidase (GUS) analysis of transgenic rice revealed that OsCHX14 is mainly expressed in lodicules and the region close by throughout the flowering process. Characterization in yeast and Xenopus laevis oocytes verified that OsCHX14 is able to transport K+, Rb+ and Cs+ in vivo. Our data suggest that OsCHX14 may play an important role in K+ homeostasis during flowering in rice.
Collapse
Affiliation(s)
- Yi Chen
- Institute of Biology (IBL), Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333 BE, PO Box 9505, 2300 RA Leiden, The Netherlands
- Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, UK
- Department of Sustainable Soils and Grassland Systems, Rothamsted Research, Harpenden AL5 2JQ, UK
| | - Jingkun Ma
- Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Anthony J Miller
- Department of Metabolic Biology, John Innes Centre, Norwich NR4 7UH, UK
| | - Bingbing Luo
- State Key Laboratory of Crop Genetics and Germplasm Enhancement, MOA Key Laboratory of Plant Nutrition and Fertilization in Low-Middle Reaches of the Yangtze River, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 219500, China
| | - Mei Wang
- Institute of Biology (IBL), Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333 BE, PO Box 9505, 2300 RA Leiden, The Netherlands
- TNO Quality of Life, Zernikedreef 9, 2333 CK Leiden, PO Box 2215, 2301 CE Leiden, The Netherlands
| | - Zhen Zhu
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 1 West Beichen Road, Chaoyang District, Beijing, 100101 China
| | - Pieter B F Ouwerkerk
- Institute of Biology (IBL), Leiden University, Sylvius Laboratory, Sylviusweg 72, 2333 BE, PO Box 9505, 2300 RA Leiden, The Netherlands
| |
Collapse
|
23
|
Yaneff A, Vitali V, Amodeo G. PIP1 aquaporins: Intrinsic water channels or PIP2 aquaporin modulators? FEBS Lett 2015; 589:3508-15. [PMID: 26526614 DOI: 10.1016/j.febslet.2015.10.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 10/14/2015] [Accepted: 10/15/2015] [Indexed: 10/22/2022]
Abstract
The highly conserved plant aquaporins, known as Plasma membrane Intrinsic Proteins (PIPs), are the main gateways for cell membrane water exchange. Years of research have described in detail the properties of the PIP2 subfamily. However, characterizing the PIP1 subfamily has been difficult due to the failure to localize to the plasma membrane. In addition, the discovery of the PIP1-PIP2 interaction suggested that PIP1 aquaporins could be regulated by a complex posttranslational mechanism that involves trafficking, heteromerization and fine-tuning of channel activity. This review not only considers the evidence and findings but also discusses the complexity of PIP aquaporins. To establish a new benchmark in PIP regulation, we propose to consider PIP1-PIP2 pairs as functional units for the purpose of future research into their physiological roles.
Collapse
Affiliation(s)
- Agustín Yaneff
- Departamento de Biodiversidad de Biología Experimental and Instituto de Biodiversidad y Biología Experimental (IBBEA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Victoria Vitali
- Departamento de Biodiversidad de Biología Experimental and Instituto de Biodiversidad y Biología Experimental (IBBEA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Gabriela Amodeo
- Departamento de Biodiversidad de Biología Experimental and Instituto de Biodiversidad y Biología Experimental (IBBEA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.
| |
Collapse
|
24
|
Lykke K, Töllner K, Römermann K, Feit PW, Erker T, MacAulay N, Löscher W. Structure-activity relationships of bumetanide derivatives: correlation between diuretic activity in dogs and inhibition of the human NKCC2A transporter. Br J Pharmacol 2015; 172:4469-4480. [PMID: 26101812 PMCID: PMC4562508 DOI: 10.1111/bph.13231] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 05/28/2015] [Accepted: 06/12/2015] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE The N-K-Cl cotransporters (NKCCs) mediate the coupled, electroneutral movement of Na+ , K+ and Cl- ions across cell membranes. There are two isoforms of this cation co-transporter, NKCC1 and NKCC2. NKCC2 is expressed primarily in the kidney and is the target of diuretics such as bumetanide. Bumetanide was discovered by screening ∼5000 3-amino-5-sulfamoylbenzoic acid derivatives, long before NKCC2 was identified in the kidney. Therefore, structure-activity studies on effects of bumetanide derivatives on NKCC2 are not available. EXPERIMENTAL APPROACH In this study, the effect of a series of diuretically active bumetanide derivatives was investigated on human NKCC2 variant A (hNKCC2A) expressed in Xenopus laevis oocytes. KEY RESULTS Bumetanide blocked hNKCC2A transport with an IC50 of 4 μM. There was good correlation between the diuretic potency of bumetanide and its derivatives in dogs and their inhibition of hNKCC2A (r2 = 0.817; P < 0.01). Replacement of the carboxylic group of bumetanide by a non-ionic residue, for example, an anilinomethyl group, decreased inhibition of hNKCC2A, indicating that an acidic group was required for transporter inhibition. Exchange of the phenoxy group of bumetanide for a 4-chloroanilino group or the sulfamoyl group by a methylsulfonyl group resulted in compounds with higher potency to inhibit hNKCC2A than bumetanide. CONCLUSIONS AND IMPLICATIONS The X. laevis oocyte expression system used in these experiments allowed analysis of the structural requirements that determine relative potency of loop diuretics on human NKCC2 splice variants, and may lead to the discovery of novel high-ceiling diuretics.
Collapse
Affiliation(s)
- Kasper Lykke
- Department of Cellular and Molecular Medicine, University of CopenhagenCopenhagen, Denmark
| | - Kathrin Töllner
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine HannoverHannover, Germany
- Center for Systems NeuroscienceHannover, Germany
| | - Kerstin Römermann
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine HannoverHannover, Germany
- Center for Systems NeuroscienceHannover, Germany
| | - Peter W Feit
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine HannoverHannover, Germany
| | - Thomas Erker
- Department of Medicinal Chemistry, University of ViennaVienna, Austria
| | - Nanna MacAulay
- Department of Cellular and Molecular Medicine, University of CopenhagenCopenhagen, Denmark
| | - Wolfgang Löscher
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine HannoverHannover, Germany
- Center for Systems NeuroscienceHannover, Germany
| |
Collapse
|
25
|
Zwart R, Peeva PM, Rong JX, Sher E. Electrophysiological characterization of human and mouse sodium-dependent citrate transporters (NaCT/SLC13A5) reveal species differences with respect to substrate sensitivity and cation dependence. J Pharmacol Exp Ther 2015; 355:247-54. [PMID: 26324167 DOI: 10.1124/jpet.115.226902] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 08/28/2015] [Indexed: 01/01/2023] Open
Abstract
The citric acid cycle intermediate citrate plays a crucial role in metabolic processes such as fatty acid synthesis, glucose metabolism, and β-oxidation. Citrate is imported from the circulation across the plasma membrane into liver cells mainly by the sodium-dependent citrate transporter (NaCT; SLC13A5). Deletion of NaCT from mice led to metabolic changes similar to caloric restriction; therefore, NaCT has been proposed as an attractive therapeutic target for the treatment of obesity and type 2 diabetes. In this study, we expressed mouse and human NaCT into Xenopus oocytes and examined some basic functional properties of those transporters. Interestingly, striking differences were found between mouse and human NaCT with respect to their sensitivities to citric acid cycle intermediates as substrates for these transporters. Mouse NaCT had at least 20- to 800-fold higher affinity for these intermediates than human NaCT. Mouse NaCT is fully active at physiologic plasma levels of citrate, but its human counterpart is not. Replacement of extracellular sodium by other monovalent cations revealed that human NaCT was markedly less dependent on extracellular sodium than mouse NaCT. The low sensitivity of human NaCT for citrate raises questions about the translatability of this target from the mouse to the human situation and raises doubts about the validity of this transporter as a therapeutic target for the treatment of metabolic diseases in humans.
Collapse
Affiliation(s)
- Ruud Zwart
- Neuroscience Discovery Research, Lilly Research Centre, Eli Lilly and Company, Windlesham, United Kingdom (R.Z., P.M.P., E.S.); and Lilly China Research and Development Center, Eli Lilly and Company, Shanghai, China (J.X.R.)
| | - Polina M Peeva
- Neuroscience Discovery Research, Lilly Research Centre, Eli Lilly and Company, Windlesham, United Kingdom (R.Z., P.M.P., E.S.); and Lilly China Research and Development Center, Eli Lilly and Company, Shanghai, China (J.X.R.)
| | - James X Rong
- Neuroscience Discovery Research, Lilly Research Centre, Eli Lilly and Company, Windlesham, United Kingdom (R.Z., P.M.P., E.S.); and Lilly China Research and Development Center, Eli Lilly and Company, Shanghai, China (J.X.R.)
| | - Emanuele Sher
- Neuroscience Discovery Research, Lilly Research Centre, Eli Lilly and Company, Windlesham, United Kingdom (R.Z., P.M.P., E.S.); and Lilly China Research and Development Center, Eli Lilly and Company, Shanghai, China (J.X.R.)
| |
Collapse
|
26
|
Pujol-Giménez J, Pérez A, Reyes AM, Loo DDF, Lostao MP. Functional characterization of the human facilitative glucose transporter 12 (GLUT12) by electrophysiological methods. Am J Physiol Cell Physiol 2015; 308:C1008-22. [PMID: 25855082 DOI: 10.1152/ajpcell.00343.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 04/06/2015] [Indexed: 12/11/2022]
Abstract
GLUT12 is a member of the facilitative family of glucose transporters. The goal of this study was to characterize the functional properties of GLUT12, expressed in Xenopus laevis oocytes, using radiotracer and electrophysiological methods. Our results showed that GLUT12 is a facilitative sugar transporter with substrate selectivity: d-glucose ≥ α-methyl-d-glucopyranoside (α-MG) > 2-deoxy-d-glucose(2-DOG) > d-fructose = d-galactose. α-MG is a characteristic substrate of the Na(+)/glucose (SGLT) family and has not been shown to be a substrate of any of the GLUTs. In the absence of sugar, (22)Na(+) was transported through GLUT12 at a higher rate (40%) than noninjected oocytes, indicating that there is a Na(+) leak through GLUT12. Genistein, an inhibitor of GLUT1, also inhibited sugar uptake by GLUT12. Glucose uptake was increased by the PKA activator 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP) but not by the PKC activator phorbol-12-myristate-13-acetate (PMA). In high K(+) concentrations, glucose uptake was blocked. Addition of glucose to the external solution induced an inward current with a reversal potential of approximately -15 mV and was blocked by Cl(-) channel blockers, indicating the current was carried by Cl(-) ions. The sugar-activated Cl(-) currents were unaffected by genistein. In high external K(+) concentrations, sugar-activated Cl(-) currents were also blocked, indicating that GLUT12 activity is voltage dependent. Furthermore, glucose-induced current was increased by the PKA activator 8-Br-cAMP but not by the PKC activator PMA. These new features of GLUT12 are very different from those described for other GLUTs, indicating that GLUT12 must have a specific physiological role within glucose homeostasis, still to be discovered.
Collapse
Affiliation(s)
- Jonai Pujol-Giménez
- Department of Nutrition, Food Science and Physiology, School of Pharmacy, University of Navarra, Pamplona, Spain
| | - Alejandra Pérez
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; and
| | - Alejandro M Reyes
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile; and
| | - Donald D F Loo
- Department of Physiology, David Geffen School of Medicine at University of California, Los Angeles, California
| | - Maria Pilar Lostao
- Department of Nutrition, Food Science and Physiology, School of Pharmacy, University of Navarra, Pamplona, Spain;
| |
Collapse
|
27
|
Abstract
Diseases affecting endodermal organs like the pancreas, lung and gastrointestinal (GI) tract have a substantial impact on human welfare. Since many of these are congenital defects that arise as a result of defects during development broad efforts are focused on understanding the development of these organs so as to better identify risk factors, disease mechanisms and therapeutic targets. Studies implementing model systems, like the amphibian Xenopus, have contributed immensely to our understanding of signaling (e.g. Wnt, FGF, BMP, RA) pathways and gene regulation (e.g. hhex, ptf1a, ngn3) that underlie normal development as well as disease progression. Recent advances in genome engineering further enhance the capabilities of the Xenopus model system for pursuing biomedical research, and will undoubtedly result in a boom of new information underlying disease mechanisms ultimately leading to advancements in diagnosis and therapy.
Collapse
|
28
|
Abstract
The oocytes of the African clawed frog (Xenopus laevis) comprise one of the most widely used membrane protein expression systems. While frequently used for studies of transporters and ion channels, the application of this system to the study of mechanosensitive ion channels has been overlooked, perhaps due to a relative abundance of native expression systems. Recent advances, however, have illustrated the advantages of the oocyte system for studying plant and bacterial mechanosensitive channels. Here we describe in detail the methods used for heterologous expression and characterization of bacterial and plant mechanosensitive channels in Xenopus oocytes.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mail Code 1137, Saint Louis, MO, 63130, USA
| | | |
Collapse
|
29
|
Maierhofer T, Diekmann M, Offenborn JN, Lind C, Bauer H, Hashimoto K, S. Al-Rasheid KA, Luan S, Kudla J, Geiger D, Hedrich R. Site- and kinase-specific phosphorylation-mediated activation of SLAC1, a guard cell anion channel stimulated by abscisic acid. Sci Signal 2014; 7:ra86. [DOI: 10.1126/scisignal.2005703] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
30
|
Do SH, Park SJ, Shin HJ, Paik HS, Zuo Z, Yoon HJ, Ryu JH. Dexmedetomidine increases the activity of excitatory amino acid transporter type 3 expressed in Xenopus oocytes: the involvement of protein kinase C and phosphatidylinositol 3-kinase. Eur J Pharmacol 2014; 738:8-13. [PMID: 24876058 DOI: 10.1016/j.ejphar.2014.05.021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 05/13/2014] [Accepted: 05/13/2014] [Indexed: 10/25/2022]
Abstract
Dexmedetomidine, an α2 adrenergic agonist, has neuroprotective and anticonvulsant properties in addition to its sedative and anxiolytic effects. We hypothesized that dexmedetomidine would increase the activity of excitatory amino acid transporter type 3 (EAAT3) and that this effect would involve protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K), two protein kinases known to regulate EAAT3 activity. EAAT3 was expressed in Xenopus oocytes by injecting its mRNA. Two-electrode voltage clamping was used to record membrane currents before, during, and after application of 30 μM l-glutamate in the presence of 0.1-30 nM dexmedetomidine. Dexmedetomidine-treated oocytes were also exposed to a PKC activator (phorbol-12-myristate-13-acetate [PMA]), PKC inhibitors (chelerythrine, staurosporine, and calphostin C), and PI3K inhibitors (wortmannin and LY294002) before current measurement. Dexmedetomidine application resulted in a concentration-dependent increase in the EAAT3 activity in response to l-glutamate. The kinetic study showed that dexmedetomidine significantly increased the Vmax without changing Km. Treatment of oocytes with PMA significantly increased transporter currents compared with controls, but treatment with dexmedetomidine plus PMA did not further increase the response compared with PMA or dexmedetomidine alone. In addition, pre-treatment of oocytes with PKC inhibitors and PI3K inhibitors significantly abolished the dexmedetomidine-enhanced EAAT3 activity. These results suggest that dexmedetomidine increases the activity of EAAT3 expressed in Xenopus oocytes. PKC and PI3K seem to mediate this effect. These findings may explain the neuroprotective and anticonvulsant effects of dexmedetomidine.
Collapse
Affiliation(s)
- Sang-Hwan Do
- Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea
| | - Seong-Joo Park
- Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea
| | - Hyun-Jung Shin
- Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea
| | - Hye-Sun Paik
- Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, South Korea
| | - Zhiyi Zuo
- Department of Anesthesiology, University of Virginia Health System, Charlottesville, VA, USA
| | - Hea-Jo Yoon
- Department of Anesthesiology and Pain Medicine, Cheil General Hospital, Kwandong University, Seoul, South Korea
| | - Jung-Hee Ryu
- Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, 463-707 Gyeonggi-do, South Korea.
| |
Collapse
|
31
|
Luxardi G, Reid B, Maillard P, Zhao M. Single cell wound generates electric current circuit and cell membrane potential variations that requires calcium influx. Integr Biol (Camb) 2014; 6:662-72. [PMID: 24801267 DOI: 10.1039/c4ib00041b] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Breaching of the cell membrane is one of the earliest and most common causes of cell injury, tissue damage, and disease. If the compromise in cell membrane is not repaired quickly, irreversible cell damage, cell death and defective organ functions will result. It is therefore fundamentally important to efficiently repair damage to the cell membrane. While the molecular aspects of single cell wound healing are starting to be deciphered, its bio-physical counterpart has been poorly investigated. Using Xenopus laevis oocytes as a model for single cell wound healing, we describe the temporal and spatial dynamics of the wound electric current circuitry and the temporal dynamics of cell membrane potential variation. In addition, we show the role of calcium influx in controlling electric current circuitry and cell membrane potential variations. (i) Upon wounding a single cell: an inward electric current appears at the wound center while an outward electric current is observed at its sides, illustrating the wound electric current circuitry; the cell membrane is depolarized; calcium flows into the cell. (ii) During cell membrane re-sealing: the wound center current density is maintained for a few minutes before decreasing; the cell membrane gradually re-polarizes; calcium flow into the cell drops. (iii) In conclusion, calcium influx is required for the formation and maintenance of the wound electric current circuitry, for cell membrane re-polarization and for wound healing.
Collapse
Affiliation(s)
- Guillaume Luxardi
- Department of Dermatology, University of California Davis, 921 Stockton Blvd, Sacramento, CA 95817, USA.
| | | | | | | |
Collapse
|
32
|
Eck P, Kwon O, Chen S, Mian O, Levine M. The human sodium-dependent ascorbic acid transporters SLC23A1 and SLC23A2 do not mediate ascorbic acid release in the proximal renal epithelial cell. Physiol Rep 2013; 1:e00136. [PMID: 24400138 PMCID: PMC3871451 DOI: 10.1002/phy2.136] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 12/23/2022] Open
Abstract
Sodium-dependent ascorbic acid membrane transporters SLC23A1 and SLC23A2 mediate ascorbic acid (vitamin C) transport into cells. However, it is unknown how ascorbic acid undergoes cellular release, or efflux. We hypothesized that SLC23A1 and SLC23A2 could serve a dual role, mediating ascorbic acid cellular efflux as well as uptake. Renal reabsorption is required for maintaining systemic vitamin C concentrations. Because efflux from nephron cells is necessary for reabsorption, we studied whether SLC23A1 and SLC23A2 mediate efflux of ascorbic acid in the human renal nephron. We found high gene expression of SLC23A1 but no expression of SLC23A2 in the proximal convoluted and straight tubules of humans. These data rule out SLC23A2 as the ascorbic acid release protein in the renal proximal tubular epithelia cell. We utilized a novel dual transporter-based Xenopus laevis oocyte system to investigate the function of the SLC23A1 protein, and found that no ascorbate release was mediated by SLC23A1. These findings were confirmed in mammalian cells overexpressing SLC23A1. Taken together, the data for SLC23A1 show that it too does not have a role in cellular release of ascorbic acid across the basolateral membrane of the proximal tubular epithelial cell, and that SLC23A1 alone is responsible for ascorbic acid uptake across the apical membrane. These findings reiterate the physiological importance of proper functioning of SLC23A1 in maintaining vitamin C levels for health and disease prevention. The ascorbate efflux mechanism in the proximal tubule of the kidney remains to be characterized.
Collapse
Affiliation(s)
- Peter Eck
- Department of Human Nutritional Sciences, University of Manitoba Winnipeg, Manitoba, Canada
| | - Oran Kwon
- Department of Nutritional Science & Food Management, Ewha Womans University Seoul, Republic of Korea
| | - Shenglin Chen
- Molecular and Clinical Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health Bethesda, 20892, Maryland
| | - Omar Mian
- Radiation Oncology, Johns Hopkins Hospital Baltimore, Maryland
| | - Mark Levine
- Molecular and Clinical Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health Bethesda, 20892, Maryland
| |
Collapse
|
33
|
Choi JS, Ryu JH, Zuo Z, Yang SM, Chang HW, Do SH. Riluzole attenuates excitatory amino acid transporter type 3 activity in Xenopus oocytes via protein kinase C inhibition. Eur J Pharmacol 2013; 713:39-43. [DOI: 10.1016/j.ejphar.2013.04.048] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 04/24/2013] [Accepted: 04/26/2013] [Indexed: 11/27/2022]
|
34
|
ABCB1 single nucleotide polymorphisms (1236C>T, 2677G>T, and 3435C>T) do not affect transport activity of human P-glycoprotein. Pharmacogenet Genomics 2013; 23:314-23. [DOI: 10.1097/fpc.0b013e328360d10c] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
35
|
A multi-system approach assessing the interaction of anticonvulsants with P-gp. PLoS One 2013; 8:e64854. [PMID: 23741405 PMCID: PMC3669347 DOI: 10.1371/journal.pone.0064854] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/19/2013] [Indexed: 12/27/2022] Open
Abstract
30% of epilepsy patients receiving antiepileptic drugs (AEDs) are not fully controlled by therapy. The drug transporter hypothesis for refractory epilepsy proposes that P-gp is over expressed at the epileptic focus with a role of P-gp in extruding AEDs from the brain. However, there is controversy regarding whether all AEDs are substrates for this transporter. Our aim was to investigate transport of phenytoin, lamotrigine and carbamazepine by using seven in-vitro transport models. Uptake assays in CEM/VBL cell lines, oocytes expressing human P-gp and an immortalised human brain endothelial cell line (hCMEC/D3) were carried out. Concentration equilibrium transport assays were performed in Caco-2, MDCKII ±P-gp and LLC-PK1±P-gp in the absence or presence of tariquidar, an inhibitor of P-gp. Finally, primary porcine brain endothelial cells were used to determine the apparent permeability (Papp) of the three AEDs in the absence or presence of P-gp inhibitors. We detected weak transport of phenytoin in two of the transport systems (MDCK and LLC-PK1 cells transfected with human P-gp) but not in the remaining five. No P-gp interaction was observed for lamotrigine or carbamazepine in any of the seven validated in-vitro transport models. Neither lamotrigine nor carbamazepine was a substrate for P-gp in any of the model systems tested. Our data suggest that P-gp is unlikely to contribute to the pathogenesis of refractory epilepsy through transport of carbamazepine or lamotrigine.
Collapse
|
36
|
Schroeder I, Gazzarrini S, Ferrara G, Thiel G, Hansen UP, Moroni A. Creation of a reactive oxygen species-insensitive Kcv channel. Biochemistry 2013; 52:3130-7. [PMID: 23578303 DOI: 10.1021/bi3016197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The current of the minimal viral K(+) channel Kcv(PCBV-1) heterologously expressed in Xenopus oocytes is strongly inhibited by reactive oxygen species (ROS) like H(2)O(2). Possible targets for the ROS effect are two cysteines (C53 and C79) and four methionines (M1, M15, M23, and M26). The C53A/C79A and M23L/M26L double mutations maintained the same ROS sensitivity as the wild type. However, M15L as a single mutant or in combination with C53A/C79A and/or M23L/M26L caused a complete loss of sensitivity to H(2)O(2). These results indicate a prominent role of M15 at the cytosolic end of the outer transmembrane helix for gating of Kcv(PCBV-1). Furthermore, even though the channel lacks a canonical voltage sensor, it exhibits a weak voltage sensitivity, resulting in a slight activation in the millisecond range after a voltage step to negative potentials. The M15L mutation inverts this kinetics into an inactivation, underlining the critical role of this residue for gating. The negative slope of the I-V curves of M15L is the same as in the wild type, indicating that the selectivity filter is not involved.
Collapse
Affiliation(s)
- Indra Schroeder
- Department of Biosciences, University of Milan, Via Celoria 26, 20133 Milano, Italy.
| | | | | | | | | | | |
Collapse
|
37
|
Sala-Rabanal M, Li DC, Dake GR, Kurata HT, Inyushin M, Skatchkov SN, Nichols CG. Polyamine transport by the polyspecific organic cation transporters OCT1, OCT2, and OCT3. Mol Pharm 2013; 10:1450-8. [PMID: 23458604 DOI: 10.1021/mp400024d] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Polyamines are ubiquitous organic cations implicated in many physiological processes. Because they are positively charged at physiological pH, carrier-mediated systems are necessary for effective membrane permeation, but the identity of specific polyamine transporter proteins in eukaryotic cells remains unclear. Polyspecific organic cation transporters (OCTs) interact with many natural and xenobiotic monovalent cations and have been reported to transport dicationic compounds, including the short polyamine putrescine. In this study, we used Xenopus oocytes expressing mammalian OCT1 (SLC22A1), OCT2 (SLC22A2), or OCT3 (SLC22A3) to assess binding and transport of longer-chain polyvalent polyamines. In OCT-expressing oocytes, [(3)H]MPP(+) uptake rates were 15- to 35-fold higher than in noninjected oocytes, whereas those for [(3)H]spermidine increased more modestly above the background, up to 3-fold. This reflected up to 20-fold lower affinity for spermidine than for MPP(+); thus, K(0.5) for MPP(+) was ~50 μM in OCT1, ~170 μM in OCT2, and ~60 μM in OCT3, whereas for spermidine, K(0.5) was ~1 mM in OCT1, OCT2, and OCT3. J(max) values for MPP(+) and spermidine were within the same range, suggesting that both compounds are transported at a similar turnover rate. To gain further insight into OCT substrate specificity, we screened a selection of structural polyamine analogues for effect on [(3)H]MPP(+) uptake. In general, blocking potency increased with overall hydrophobic character, which indicates that, as for monovalent cations, hydrophobicity is a major requirement for recognition in polyvalent OCT substrates and inhibitors. Our results demonstrate that the natural polyamines are low affinity, but relatively high turnover, substrates for OCTs. The identification of OCTs as polyamine transport systems may contribute to further understanding of the mechanisms involved in polyamine homeostasis and aid in the design of polyamine-like OCT-targeted drugs.
Collapse
Affiliation(s)
- Monica Sala-Rabanal
- Department of Cell Biology and Physiology, and Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
| | | | | | | | | | | | | |
Collapse
|
38
|
Lin-Moshier Y, Marchant JS. The Xenopus oocyte: a single-cell model for studying Ca2+ signaling. Cold Spring Harb Protoc 2013; 2013:2013/3/pdb.top066308. [PMID: 23457336 DOI: 10.1101/pdb.top066308] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the four decades since the Xenopus oocyte was first demonstrated to have the capacity to translate exogenous mRNAs, this system has been exploited for many different experimental purposes. Typically, the oocyte is used either as a "biological test tube" for heterologous expression of proteins without any particular cell biological insight or, alternatively, it is used for applications where cell biology is paramount, such as investigations of the cellular adaptations that power early development. In this article, we discuss the utility of the Xenopus oocyte for studying Ca(2+) signaling in both these contexts.
Collapse
Affiliation(s)
- Yaping Lin-Moshier
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
| | | |
Collapse
|
39
|
Ochoa-de la Paz LD, Salazar-Soto DB, Reyes JP, Miledi R, Martinez-Torres A. A hyperpolarization-activated ion current of amphibian oocytes. Pflugers Arch 2013; 465:1087-99. [PMID: 23440457 DOI: 10.1007/s00424-013-1231-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Revised: 01/28/2013] [Accepted: 01/30/2013] [Indexed: 11/29/2022]
Abstract
A comparative analysis of a hyperpolarization-activated ion current present in amphibian oocytes was performed using the two-electrode voltage-clamp technique in Xenopus laevis, Xenopus tropicalis, and Ambystoma mexicanum. This current appears to be driven mainly by Cl(-) ions, is independent of Ca(2+), and is made evident by applying extremely negative voltage pulses; it shows a slow activating phase and little or no desensitization. The pharmacological profile of the current is complex. The different channel blocker used for Cl(-), K(+), Na(+) and Ca(2+) conductances, exhibited various degrees of inhibition depending of the species. The profiles illustrate the intricacy of the components that give rise to this current. During X. laevis oogenesis, the hyperpolarization-activated current is present at all stages of oocytes tested (II-VI), and the amplitude of the current increases from about 50 nA in stage I to more than 1 μA in stage VI; nevertheless, there was no apparent modification of the kinetics. Our results suggest that the hyperpolarization-activated current is present both in order Anura and Urodela oocytes. However, the electrophysiological and pharmacological characteristics are quite perplexing and seem to suggest a mixture of ionic conductances that includes the activation of both anionic and cationic channels, most probably transiently opened due to the extreme hyperpolarizion of the plasma membrane. As a possible mechanism for the generation of the current, a kinetic model which fits the data suggests the opening of pores in the plasma membrane whose ion selectivity is dependent on the extracellular Cl(-) concentration. The extreme voltage conditions could induce the opening of otherwise latent pores in plasma membrane proteins (i.e., carriers), resembling the ´slippage´ events already described for some carriers. These observations should be valuable for other groups trying to express cloned, voltage-dependent ion channels in oocytes of amphibian in which hyperpolarizing voltage pulses are applied to activate the channels.
Collapse
Affiliation(s)
- L D Ochoa-de la Paz
- Departamento de Neurobiología Celular y Molecular, Laboratorio de Neurobiología Molecular y Celular, Instituto de Neurobiología, Campus UNAM Juriquilla, Querétaro, Qro, CP 76230, Mexico.
| | | | | | | | | |
Collapse
|
40
|
Kremer W, Kalbitzer HR, Schreier C, Huber F, Schulze C, Daniel H, Stolz J. A Single-Cell NMR Membrane Transport Assay. Chembiochem 2012; 13:2501-4. [DOI: 10.1002/cbic.201200514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Indexed: 11/11/2022]
|
41
|
Haferkamp I, Linka N. Functional expression and characterisation of membrane transport proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2012; 14:675-90. [PMID: 22639981 DOI: 10.1111/j.1438-8677.2012.00591.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane transporters set the framework organising the complexity of plant metabolism in cells, tissues and organisms. Their substrate specificity and controlled activity in different cells is a crucial part for plant metabolism to run pathways in concert. Transport proteins catalyse the uptake and exchange of ions, substrates, intermediates, products and cofactors across membranes. Given the large number of metabolites, a wide spectrum of transporters is required. The vast majority of in silico annotated membrane transporters in plant genomes, however, has not yet been functionally characterised. Hence, to understand the metabolic network as a whole, it is important to understand how transporters connect and control the metabolic pathways of plant cells. Heterologous expression and in vitro activity studies of recombinant transport proteins have highly improved their functional analysis in the last two decades. This review provides a comprehensive overview of the recent advances in membrane protein expression and functional characterisation using various host systems and transport assays.
Collapse
Affiliation(s)
- I Haferkamp
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - N Linka
- Plant Physiology, Technical University of Kaiserslautern, Kaiserslautern, Germany Plant Biochemistry, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| |
Collapse
|
42
|
Parker MD, Qin X, Williamson RC, Toye AM, Boron WF. HCO(3)(-)-independent conductance with a mutant Na(+)/HCO(3)(-) cotransporter (SLC4A4) in a case of proximal renal tubular acidosis with hypokalaemic paralysis. J Physiol 2012; 590:2009-34. [PMID: 22331414 PMCID: PMC3573318 DOI: 10.1113/jphysiol.2011.224733] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 02/07/2012] [Indexed: 12/14/2022] Open
Abstract
The renal electrogenic Na(+)/HCO(3)(−) cotransporter (NBCe1-A) contributes to the basolateral step of transepithelial HCO(3)(−) reabsorption in proximal tubule epithelia, contributing to the buffering of blood pH. Elsewhere in the body (e.g. muscle cells) NBCe1 variants contribute to, amongst other processes, maintenance of intracellular pH. Others have described a homozygous mutation in NBCe1 (NBCe1-A p.Ala799Val) in an individual with severe proximal renal tubular acidosis (pRTA; usually associated with defective HCO(3)(−) reabsorption in proximal tubule cells) and hypokalaemic periodic paralysis (hypoPP; usually associated with leaky cation channels in muscle cells). Using biotinylation and two-electrode voltage-clamp on Xenopus oocytes expressing NBCe1, we demonstrate that the mutant NBCe1-A (A(A799V)) exhibits a per-molecule transport defect that probably contributes towards the observed pRTA. Furthermore, we find that A(A799V) expression is associated with an unusual HCO(3)(−)-independent conductance that, if associated with mutant NBCe1 in muscle cells, could contribute towards the appearance of hypokalaemic paralysis in the affected individual. We also study three novel lab mutants of NBCe1-A: p.Ala799Ile, p.Ala799Gly and p.Ala799Ser. All three exhibit a per-molecule transport defect, but only A(A799I) exhibits an A(A799V)-like ion conductance. A(A799G) and A(A799S) exhibit unusual outward rectification in their HCO(3)(−)-dependent conductance and A(A799G) exhibits reduced sensitivity to both DIDS and tenidap. A799G is the first mutation shown to affect the apparent tenidap affinity of NBCe1. Finally we show that A(A799V) and A(A799I), which accumulate poorly in the plasma membrane of oocytes, exhibit signs of abnormal intracellular accumulation in a non-polarized renal cell-line.
Collapse
Affiliation(s)
- Mark D Parker
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
| | | | | | | | | |
Collapse
|
43
|
Khokha MK. Xenopuswhite papers and resources: Folding functional genomics and genetics into the frog. Genesis 2012; 50:133-42. [DOI: 10.1002/dvg.22015] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 01/13/2012] [Accepted: 01/15/2012] [Indexed: 02/04/2023]
|
44
|
Maksaev G, Haswell ES. Expression and characterization of the bacterial mechanosensitive channel MscS in Xenopus laevis oocytes. ACTA ACUST UNITED AC 2011; 138:641-9. [PMID: 22084416 PMCID: PMC3226970 DOI: 10.1085/jgp.201110723] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have successfully expressed and characterized mechanosensitive channel of small conductance (MscS) from Escherichia coli in oocytes of the African clawed frog, Xenopus laevis. MscS expressed in oocytes has the same single-channel conductance and voltage dependence as the channel in its native environment. Two hallmarks of MscS activity, the presence of conducting substates at high potentials and reversible adaptation to a sustained stimulus, are also exhibited by oocyte-expressed MscS. In addition to its ease of use, the oocyte system allows the user to work with relatively large patches, which could be an advantage for the visualization of membrane deformation. Furthermore, MscS can now be compared directly to its eukaryotic homologues or to other mechanosensitive channels that are not easily studied in E. coli.
Collapse
Affiliation(s)
- Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, Saint Louis, MO 63130, USA
| | | |
Collapse
|
45
|
Moss DM, Kwan WS, Liptrott NJ, Smith DL, Siccardi M, Khoo SH, Back DJ, Owen A. Raltegravir is a substrate for SLC22A6: a putative mechanism for the interaction between raltegravir and tenofovir. Antimicrob Agents Chemother 2011; 55:879-87. [PMID: 21078936 PMCID: PMC3028780 DOI: 10.1128/aac.00623-10] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 08/07/2010] [Accepted: 11/02/2010] [Indexed: 01/27/2023] Open
Abstract
The identification of transporters of the HIV integrase inhibitor raltegravir could be a factor in an understanding of the pharmacokinetic-pharmacodynamic relationship and reported drug interactions of raltegravir. Here we determined whether raltegravir was a substrate for ABCB1 or the influx transporters SLCO1A2, SLCO1B1, SLCO1B3, SLC22A1, SLC22A6, SLC10A1, SLC15A1, and SLC15A2. Raltegravir transport by ABCB1 was studied with CEM, CEM(VBL100), and Caco-2 cells. Transport by uptake transporters was assessed by using a Xenopus laevis oocyte expression system, peripheral blood mononuclear cells, and primary renal cells. The kinetics of raltegravir transport and competition between raltegravir and tenofovir were also investigated using SLC22A6-expressing oocytes. Raltegravir was confirmed to be an ABCB1 substrate in CEM, CEM(VBL100), and Caco-2 cells. Raltegravir was also transported by SLC22A6 and SLC15A1 in oocyte expression systems but not by other transporters studied. The K(m) and V(max) for SLC22A6 transport were 150 μM and 36 pmol/oocyte/h, respectively. Tenofovir and raltegravir competed for SLC22A6 transport in a concentration-dependent manner. Raltegravir inhibited 1 μM tenofovir with a 50% inhibitory concentration (IC(50)) of 14.0 μM, and tenofovir inhibited 1 μM raltegravir with an IC(50) of 27.3 μM. Raltegravir concentrations were not altered by transporter inhibitors in peripheral blood mononuclear cells or primary renal cells. Raltegravir is a substrate for SLC22A6 and SLC15A1 in the oocyte expression system. However, transport was limited compared to endogenous controls, and these transporters are unlikely to have a great impact on raltegravir pharmacokinetics.
Collapse
Affiliation(s)
- Darren M. Moss
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Wai San Kwan
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Neill J. Liptrott
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Darren L. Smith
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Marco Siccardi
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Saye H. Khoo
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - David J. Back
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| | - Andrew Owen
- Department of Pharmacology and Therapeutics, University of Liverpool, Liverpool, United Kingdom, NIHR Biomedical Research Centre, Royal Liverpool & Broadgreen University Hospitals Trust, Liverpool, United Kingdom
| |
Collapse
|
46
|
Musa-Aziz R, Boron WF, Parker MD. Using fluorometry and ion-sensitive microelectrodes to study the functional expression of heterologously-expressed ion channels and transporters in Xenopus oocytes. Methods 2010; 51:134-45. [PMID: 20051266 PMCID: PMC2905798 DOI: 10.1016/j.ymeth.2009.12.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 12/23/2009] [Accepted: 12/29/2009] [Indexed: 12/17/2022] Open
Abstract
The Xenopus laevis oocyte is a model system for the electrophysiological study of exogenous ion transporters. Three main reasons make the oocyte suitable for this purpose: (a) it has a large cell size (approximately 1mm diameter), (b) it has an established capacity to produce-from microinjected mRNAs or cRNAs-exogenous ion transporters with close-to-physiological post-translational modifications and actions, and (c) its membranes contain endogenous ion-transport activities which are usually smaller in magnitude than the activities of exogenously-expressed ion transporters. The expression of ion transporters as green fluorescent protein fusions allows the fluorometric assay of transporter yield in living oocytes. Monitoring of transporter-mediated movement of ions such as Cl(-), H(+) (and hence base equivalents like OH(-) and HCO(3)(-)), K(+), and Na(+) is achieved by positioning the tips of ion-sensitive microelectrodes inside the oocyte and/or at the surface of the oocyte plasma membrane. The use of ion-sensitive electrodes is critical for studying net ion-movements mediated by electroneutral transporters. The combined use of fluorometry and electrophysiology expedites transporter study by allowing measurement of transporter yield prior to electrophysiological study and correlation of relative transporter yield with transport rates.
Collapse
Affiliation(s)
- Raif Musa-Aziz
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | | | | |
Collapse
|
47
|
Terhag J, Cavara NA, Hollmann M. Cave Canalem: How endogenous ion channels may interfere with heterologous expression in Xenopus oocytes. Methods 2010; 51:66-74. [DOI: 10.1016/j.ymeth.2010.01.034] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 01/26/2010] [Accepted: 01/27/2010] [Indexed: 10/19/2022] Open
|