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Abdelaziz R, Tomczak AP, Neef A, Pardo LA. Revealing a hidden conducting state by manipulating the intracellular domains in K V10.1 exposes the coupling between two gating mechanisms. eLife 2024; 12:RP91420. [PMID: 39259196 PMCID: PMC11390113 DOI: 10.7554/elife.91420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/12/2024] Open
Abstract
The KCNH family of potassium channels serves relevant physiological functions in both excitable and non-excitable cells, reflected in the massive consequences of mutations or pharmacological manipulation of their function. This group of channels shares structural homology with other voltage-gated K+ channels, but the mechanisms of gating in this family show significant differences with respect to the canonical electromechanical coupling in these molecules. In particular, the large intracellular domains of KCNH channels play a crucial role in gating that is still only partly understood. Using KCNH1(KV10.1) as a model, we have characterized the behavior of a series of modified channels that could not be explained by the current models. With electrophysiological and biochemical methods combined with mathematical modeling, we show that the uncovering of an open state can explain the behavior of the mutants. This open state, which is not detectable in wild-type channels, appears to lack the rapid flicker block of the conventional open state. Because it is accessed from deep closed states, it elucidates intermediate gating events well ahead of channel opening in the wild type. This allowed us to study gating steps prior to opening, which, for example, explain the mechanism of gating inhibition by Ca2+-Calmodulin and generate a model that describes the characteristic features of KCNH channels gating.
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Affiliation(s)
- Reham Abdelaziz
- Oncophysiology Group. Max Planck Institute for Multidisciplinary Sciences, City Campus, Göttingen, Germany
| | - Adam P Tomczak
- Oncophysiology Group. Max Planck Institute for Multidisciplinary Sciences, City Campus, Göttingen, Germany
| | - Andreas Neef
- Neurophysics Laboratory, Göttingen Campus Institute for Dynamics of Biological Networks, Göttingen, Germany
| | - Luis A Pardo
- Oncophysiology Group. Max Planck Institute for Multidisciplinary Sciences, City Campus, Göttingen, Germany
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Robak MJ, Saenz V, de Cortie E, Richards-Zawacki CL. Effects of temperature on the interaction between amphibian skin bacteria and Batrachochytrium dendrobatidis. Front Microbiol 2023; 14:1253482. [PMID: 37942072 PMCID: PMC10628663 DOI: 10.3389/fmicb.2023.1253482] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 10/06/2023] [Indexed: 11/10/2023] Open
Abstract
Symbiotic relationships between animals and microbes are important for a range of functions, from digestion to protection from pathogens. However, the impact of temperature variation on these animal-microbe interactions remains poorly understood. Amphibians have experienced population declines and even extinctions on a global scale due to chytridiomycosis, a disease caused by chytrid fungi in the genus Batrachochytrium. Variation in susceptibility to this disease exists within and among host species. While the mechanisms generating differences in host susceptibility remain elusive, differences in immune system components, as well as variation in host and environmental temperatures, have been associated with this variation. The symbiotic cutaneous bacteria of amphibians are another potential cause for variation in susceptibility to chytridiomycosis, with some bacterial species producing antifungal metabolites that prevent the growth of Bd. The growth of both Bd and bacteria are affected by temperature, and thus we hypothesized that amphibian skin bacteria may be more effective at preventing Bd growth at certain temperatures. To test this, we collected bacteria from the skins of frogs, harvested the metabolites they produced when grown at three different temperatures, and then grew Bd in the presence of those metabolites under those same three temperatures in a three-by-three fully crossed design. We found that both the temperature at which cutaneous bacteria were grown (and metabolites produced) as well as the temperature at which Bd is grown can impact the ability of cutaneous bacteria to inhibit the growth of Bd. While some bacterial isolates showed the ability to inhibit Bd growth across multiple temperature treatments, no isolate was found to be inhibitive across all combinations of bacterial incubation or Bd challenge temperatures, suggesting that temperature affects both the metabolites produced and the effectiveness of those metabolites against the Bd pathogen. These findings move us closer to a mechanistic understanding of why chytridiomycosis outbreaks and related amphibian declines are often limited to certain climates and seasons.
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Affiliation(s)
- Matthew J. Robak
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, LA, United States
| | - Veronica Saenz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, United States
- Department of Biology, The Pennsylvania State University, State College, PA, United States
| | - Esmee de Cortie
- Falk School of Sustainability and Environment, Chatham University, Pittsburgh, PA, United States
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Aquatic Freshwater Vertebrate Models of Epilepsy Pathology: Past Discoveries and Future Directions for Therapeutic Discovery. Int J Mol Sci 2022; 23:ijms23158608. [PMID: 35955745 PMCID: PMC9368815 DOI: 10.3390/ijms23158608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/29/2022] [Accepted: 07/30/2022] [Indexed: 12/04/2022] Open
Abstract
Epilepsy is an international public health concern that greatly affects patients’ health and lifestyle. About 30% of patients do not respond to available therapies, making new research models important for further drug discovery. Aquatic vertebrates present a promising avenue for improved seizure drug screening and discovery. Zebrafish (Danio rerio) and African clawed frogs (Xenopus laevis and tropicalis) are increasing in popularity for seizure research due to their cost-effective housing and rearing, similar genome to humans, ease of genetic manipulation, and simplicity of drug dosing. These organisms have demonstrated utility in a variety of seizure-induction models including chemical and genetic methods. Past studies with these methods have produced promising data and generated questions for further applications of these models to promote discovery of drug-resistant seizure pathology and lead to effective treatments for these patients.
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Silverio MP, Kraychete GB, Rosado AS, Bonelli RR. Pseudomonas fluorescens Complex and Its Intrinsic, Adaptive, and Acquired Antimicrobial Resistance Mechanisms in Pristine and Human-Impacted Sites. Antibiotics (Basel) 2022; 11:antibiotics11080985. [PMID: 35892375 PMCID: PMC9331890 DOI: 10.3390/antibiotics11080985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 12/16/2022] Open
Abstract
Pseudomonas spp. are ubiquitous microorganisms that exhibit intrinsic and acquired resistance to many antimicrobial agents. Pseudomonas aeruginosa is the most studied species of this genus due to its clinical importance. In contrast, the Pseudomonas fluorescens complex consists of environmental and, in some cases, pathogenic opportunistic microorganisms. The records of antimicrobial-resistant P. fluorescens are quite scattered, which hinders the recognition of patterns. This review compiles published data on antimicrobial resistance in species belonging to the P. fluorescens complex, which were identified through phylogenomic analyses. Additionally, we explored the occurrence of clinically relevant antimicrobial resistance genes in the genomes of the respective species available in the NCBI database. Isolates were organized into two categories: strains isolated from pristine sites and strains isolated from human-impacted or metal-polluted sites. Our review revealed that many reported resistant phenotypes in this complex might be related to intrinsic features, whereas some of them might be ascribed to adaptive mechanisms such as colistin resistance. Moreover, a few studies reported antimicrobial resistance genes (ARGs), mainly β-lactamases. In-silico analysis corroborated the low occurrence of transferable resistance mechanisms in this Pseudomonas complex. Both phenotypic and genotypic assays are necessary to gain insights into the evolutionary aspects of antimicrobial resistance in the P. fluorescens complex and the possible role of these ubiquitous species as reservoirs of clinically important and transmissible ARGs.
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Affiliation(s)
- Myllena Pereira Silverio
- Laboratório de Ecologia Molecular Microbiana, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-902, Brazil
- Laboratório de Investigação em Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-902, Brazil
| | - Gabriela Bergiante Kraychete
- Laboratório de Investigação em Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-902, Brazil
| | - Alexandre Soares Rosado
- Laboratório de Ecologia Molecular Microbiana, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-902, Brazil
- Biological and Environmental Sciences and Engineering Division (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Raquel Regina Bonelli
- Laboratório de Investigação em Microbiologia Médica, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro 21941-902, Brazil
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Majumdar R, Hariharan K, Vaishnavi S, Sugumar S. Review on Stenotrophomonas maltophilia: an emerging multidrug-resistant opportunistic pathogen. Recent Pat Biotechnol 2022; 16:329-354. [PMID: 35549857 DOI: 10.2174/1872208316666220512121205] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/10/2021] [Accepted: 12/23/2021] [Indexed: 11/22/2022]
Abstract
Stenotrophomonas maltophilia is an opportunistic pathogen that results in nosocomial infections in immunocompromised individuals. These bacteria colonize on the surface of medical devices and therapeutic equipment like urinary catheters, endoscopes, and ventilators, causing respiratory and urinary tract infections. The low outer membrane permeability of multidrug-resistance efflux systems and the two chromosomally encoded β-lactamases present in S.maltophilia are challenging for arsenal control. The cell-associated and extracellular virulence factors in S.maltophilia are involved in colonization and biofilm formation on the host surfaces. The spread of antibiotic-resistant genes in the pathogenic S.maltophilia attributes to bacterial resistance against a wide range of antibiotics, including penicillin, quinolones, and carbapenems. So far, tetracycline derivatives, fluoroquinolones, and trimethoprim-sulfamethoxazole (TMP-SMX) are considered promising antibiotics against S.maltophilia. Due to the adaptive nature of the intrinsically resistant mechanism towards the number of antibiotics and its ability to acquire new resistance via mutation and horizontal gene transfer, it is quite tricky for medicinal contribution against S.maltophilia. The current review summarizes the literary data of pathogenicity, quorum sensing, biofilm formation, virulence factors, and antibiotic resistance of S.maltophilia.
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Affiliation(s)
- Rikhia Majumdar
- Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, Kattankulathur-603203, Tamilnadu, India
| | - K Hariharan
- Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, Kattankulathur-603203, Tamilnadu, India
| | - S Vaishnavi
- Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, Kattankulathur-603203, Tamilnadu, India
| | - Shobana Sugumar
- Department of Genetic Engineering, School of Bioengineering, SRM Institute of Science and Technology, Kattankulathur-603203, Tamilnadu, India
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Structural Mechanics of the Alpha-2-Macroglobulin Transformation. J Mol Biol 2022; 434:167413. [PMID: 34942166 PMCID: PMC8897276 DOI: 10.1016/j.jmb.2021.167413] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 11/21/2022]
Abstract
Alpha-2-Macroglobulin (A2M) is the critical pan-protease inhibitor of the innate immune system. When proteases cleave the A2M bait region, global structural transformation of the A2M tetramer is triggered to entrap the protease. The structural basis behind the cleavage-induced transformation and the protease entrapment remains unclear. Here, we report cryo-EM structures of native- and intermediate-forms of the Xenopus laevis egg A2M homolog (A2Moo or ovomacroglobulin) tetramer at 3.7-4.1 Å and 6.4 Å resolution, respectively. In the native A2Moo tetramer, two pairs of dimers arrange into a cross-like configuration with four 60 Å-wide bait-exposing grooves. Each bait in the native form threads into an aperture formed by three macroglobulin domains (MG2, MG3, MG6). The bait is released from the narrowed aperture in the induced protomer of the intermediate form. We propose that the intact bait region works as a "latch-lock" to block futile A2M transformation until its protease-mediated cleavage.
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Abstract
Stenotrophomonas maltophilia is an opportunistic pathogen of significant concern to susceptible patient populations. This pathogen can cause nosocomial and community-acquired respiratory and bloodstream infections and various other infections in humans. Sources include water, plant rhizospheres, animals, and foods. Studies of the genetic heterogeneity of S. maltophilia strains have identified several new genogroups and suggested adaptation of this pathogen to its habitats. The mechanisms used by S. maltophilia during pathogenesis continue to be uncovered and explored. S. maltophilia virulence factors include use of motility, biofilm formation, iron acquisition mechanisms, outer membrane components, protein secretion systems, extracellular enzymes, and antimicrobial resistance mechanisms. S. maltophilia is intrinsically drug resistant to an array of different antibiotics and uses a broad arsenal to protect itself against antimicrobials. Surveillance studies have recorded increases in drug resistance for S. maltophilia, prompting new strategies to be developed against this opportunist. The interactions of this environmental bacterium with other microorganisms are being elucidated. S. maltophilia and its products have applications in biotechnology, including agriculture, biocontrol, and bioremediation.
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Abstract
A complete characterization of temperature -and voltage-activated TRP channel gating requires a precise determination of the absolute probability of opening in a wide range of voltages, temperatures, and agonist concentrations. We have achieved this in the case of the TRPM8 channel expressed in Xenopus laevis oocytes. Measurements covered an extensive range of probabilities and unprecedented applied voltages up to 500 mV. In this chapter, we describe animal care protocols of patch-clamp pipette preparation, temperature control methods, and analysis of ionic currents to obtain reliable absolute open channel probabilities.
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9
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Abstract
Bacteria of the genus Stenotrophomonas are found throughout the environment, in close association with soil, sewage, and plants. Stenotrophomonas maltophilia, the first member of this genus, is the predominant species, observed in soil, water, plants, animals, and humans. It is also an opportunistic pathogen associated with the increased number of infections in both humans and animals in recent years. In this article, we summarize all Stenotrophomonas species (mainly S. maltophilia) isolated from animals and food products of animal origin and further distinguish all isolates based on antimicrobial susceptibility and resistance phenotypes. The various mechanisms of both intrinsic and acquired antimicrobial resistance, which were mainly identified in S. maltophilia isolates of nosocomial infections, have been classified as follows: multidrug efflux pumps; resistance to β-lactams, aminoglycosides, quinolones, trimethoprim-sulfamethoxazole, and phenicols; and alteration of lipopolysaccharide and two-component regulatory systems. The dissemination, coselection, and persistence of resistance determinants among S. maltophilia isolates have also been elaborated.
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10
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Abstract
The Xenopus oocyte is a specialized single cell of colossal size (>1 mm diameter) that is highly amenable for microinjection and a stalwart model for heterologous expression. Oocytes are easily obtainable, robust in vitro, and faithfully express injected constructs. Their large size translational capacity provides a huge canvas for observing and recording integrated cellular responses-from studies of single molecules within single cells to medium-throughput drug-screening applications. Most eukaryotic promoters suffice for Xenopus expression, and the oocyte can functionally express proteins from many diverse organisms. This protocol provides a basic introduction for scientists keen to perform nuclear microinjections of cDNA constructs. These are easy methods to master, do not require elaborate equipment, and make accessible a wonderful model cell system for studying signaling, transport, cell architecture, and protein function.
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11
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Zhang G, Cui J. Patch-Clamp and Perfusion Techniques to Study Ion Channels Expressed in Xenopus Oocytes. Cold Spring Harb Protoc 2018; 2018:pdb.prot099051. [PMID: 29382809 DOI: 10.1101/pdb.prot099051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Xenopus oocyte expression system is ideal for electrophysiological characterization of voltage-dependent and ligand-dependent ion channels because of its relatively low background of endogenous channels and the large size of the cell. Here, we present a protocol to study voltage- and ligand-dependent activation of ion channels expressed in Xenopus oocytes using patch-clamp techniques designed to control both the membrane voltage and the intracellular solution. In this protocol, the large conductance voltage- and Ca2+-activated K+ (BK) channel is studied as an example. After injection of BK channel mRNA, oocytes are incubated for 2-7 d at 18°C. Inside-out membrane patches containing single or multiple BK channels are excised with perfusion of different solutions during recording. The protocol can be used to study structure-function relations for ion channels and neurotransmitter receptors.
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Affiliation(s)
- Guohui Zhang
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri 63130
| | - Jianmin Cui
- Department of Biomedical Engineering, Center for the Investigation of Membrane Excitability Disorders, Cardiac Bioelectricity and Arrhythmia Center, Washington University, St. Louis, Missouri 63130
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12
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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.
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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
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Gauer JS, Tumova S, Lippiat JD, Kerimi A, Williamson G. Differential patterns of inhibition of the sugar transporters GLUT2, GLUT5 and GLUT7 by flavonoids. Biochem Pharmacol 2018; 152:11-20. [PMID: 29548810 DOI: 10.1016/j.bcp.2018.03.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Accepted: 03/09/2018] [Indexed: 11/16/2022]
Abstract
Only limited data are available on the inhibition of the sugar transporter GLUT5 by flavonoids or other classes of bioactives. Intestinal GLUT7 is poorly characterised and no information exists concerning its inhibition. We aimed to study the expression of GLUT7 in Caco-2/TC7 intestinal cells, and evaluate inhibition of glucose transport by GLUT2 and GLUT7, and of fructose transport by GLUT2, GLUT5 and GLUT7, by flavonoids. Differentiated Caco-2/TC7 cell monolayers were used to investigate GLUT7 expression, as well as biotinylation and immunofluorescence to assess GLUT7 location. For mechanistic sugar transport studies, X. laevis oocytes were injected with individual mRNA, and GLUT protein expression on oocyte membranes was confirmed. Oocytes were incubated with D-[14C(U)]-glucose or D-[14C(U)]-fructose in the presence of flavonoids, and uptake was estimated by liquid scintilation counting. In differentiated Caco-2/TC7 cell monolayers, GLUT7 was mostly expressed apically. When applied apically, or to both compartments, sorbitol, galactose, L-glucose or sucrose did not affect GLUT7 mRNA expression. Fructose applied to both sides increased GLUT7 mRNA (13%, p ≤ 0.001) and total GLUT7 protein (2.7-fold, p ≤ 0.05), while the ratio between apical, basolateral and total GLUT7 protein was unchanged. In the X. laevis oocyte model, GLUT2-mediated glucose and fructose transport were inhibited by quercetin, (-)-epigallocatechin gallate (EGCG) and apigenin, GLUT5-mediated fructose transport was inhibited by apigenin and EGCG, but not by quercetin, and GLUT7-mediated uptake of both glucose and fructose was inhibited by apigenin, but not by quercetin nor EGCG. Expression of GLUT7 was increased by fructose, but only when applied to Caco-2/TC7 cells both apically and basolaterally. Since GLUT2, GLUT5 and GLUT7 show different patterns of inhibition by the tested flavonoids, we suggest that they have the potential to be used as investigational tools to distinguish sugar transporter activity in different biological settings.
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Affiliation(s)
- Julia S Gauer
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, UK
| | - Sarka Tumova
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, UK
| | - Jonathan D Lippiat
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Asimina Kerimi
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, UK
| | - Gary Williamson
- School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, UK.
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14
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Abstract
Xenopus oocytes and oocyte extracts are the starting material for a variety of experimental approaches. Oocytes are obtained by surgical removal of the ovary from anesthetized females. Although oocytes may be used while they remain within their ovarian follicle, it is more practical to work with defolliculated oocytes. Defolliculation can be performed either manually or enzymatically. Here we present a protocol for the isolation and separation of Xenopus oocytes at various developmental stages, and guidelines for maintaining oocytes in culture.
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Affiliation(s)
- Karen Newman
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, Florida 33136
| | - Tristan Aguero
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, Florida 33136
| | - Mary Lou King
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, Florida 33136
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15
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Kubat Öktem E, Mruk K, Chang J, Akin A, Kobertz WR, Brown RH. Mutant SOD1 protein increases Nav1.3 channel excitability. J Biol Phys 2016; 42:351-70. [PMID: 27072680 DOI: 10.1007/s10867-016-9411-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 02/10/2016] [Indexed: 02/07/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a lethal paralytic disease caused by the degeneration of motor neurons in the spinal cord, brain stem, and motor cortex. Mutations in the gene encoding copper/zinc superoxide dismutase (SOD1) are present in ~20% of familial ALS and ~2% of all ALS cases. The most common SOD1 gene mutation in North America is a missense mutation substituting valine for alanine (A4V). In this study, we analyze sodium channel currents in oocytes expressing either wild-type or mutant (A4V) SOD1 protein. We demonstrate that the A4V mutation confers a propensity to hyperexcitability on a voltage-dependent sodium channel (Nav1.3) mediated by heightened total Na(+) conductance and a hyperpolarizing shift in the voltage dependence of Nav1.3 activation. To estimate the impact of these channel effects on excitability in an intact neuron, we simulated these changes in the program NEURON; this shows that the changes induced by mutant SOD1 increase the spontaneous firing frequency of the simulated neuron. These findings are consistent with the view that excessive excitability of neurons is one component in the pathogenesis of this disease.
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Affiliation(s)
- Elif Kubat Öktem
- Institute of Biomedical Engineering, Boğaziçi University, Istanbul, Turkey. .,REMER (Regenerative and Restorative Medicine Research Center), Istanbul Medipol University, Istanbul, Turkey.
| | - Karen Mruk
- Departments of Chemical and Systems Biology and Developmental Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Joshua Chang
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Ata Akin
- Department of Medical Engineering, Acıbadem University, Istanbul, Turkey
| | - William R Kobertz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Robert H Brown
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA, USA
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Lin-Moshier Y, Marchant JS. Nuclear microinjection to assess how heterologously expressed proteins impact Ca2+ signals in Xenopus oocytes. Cold Spring Harb Protoc 2013; 2013:2013/3/pdb.prot072785. [PMID: 23457340 DOI: 10.1101/pdb.prot072785] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Xenopus oocyte is frequently used for heterologous expression and for studying the spatiotemporal patterning of Ca(2+) signals. Here, we outline a protocol for nuclear microinjection of the Xenopus oocyte for the purpose of studying how subsequently expressed proteins impact intracellular Ca(2+) signals evoked by inositol trisphosphate (InsP3). Injected oocytes can easily be identified by reporter technologies and the impact of heterologously expressed proteins on the generation and properties of InsP3-evoked Ca(2+) signals can be resolved using caged InsP3 and fluorescent Ca(2+) indicators.
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Affiliation(s)
- Yaping Lin-Moshier
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA
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Structural insights into neuronal K+ channel-calmodulin complexes. Proc Natl Acad Sci U S A 2012; 109:13579-83. [PMID: 22869708 DOI: 10.1073/pnas.1207606109] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Calmodulin (CaM) is a ubiquitous intracellular calcium sensor that directly binds to and modulates a wide variety of ion channels. Despite the large repository of high-resolution structures of CaM bound to peptide fragments derived from ion channels, there is no structural information about CaM bound to a fully folded ion channel at the plasma membrane. To determine the location of CaM docked to a functioning KCNQ K(+) channel, we developed an intracellular tethered blocker approach to measure distances between CaM residues and the ion-conducting pathway. Combining these distance restraints with structural bioinformatics, we generated an archetypal quaternary structural model of an ion channel-CaM complex in the open state. These models place CaM close to the cytoplasmic gate, where it is well positioned to modulate channel function.
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Pierce DW, Pejo E, Raines DE, Forman SA. Carboetomidate inhibits alpha4/beta2 neuronal nicotinic acetylcholine receptors at concentrations affecting animals. Anesth Analg 2012; 115:70-2. [PMID: 22543065 DOI: 10.1213/ane.0b013e318254273e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Carboetomidate is an etomidate derivative that produces hypnosis without inhibiting adrenal corticosteroid synthesis. Similar to etomidate, carboetomidate modulates γ-aminobutyric acid type A receptors, but its effects on other ion channel targets of general anesthetics are unknown. METHODS We compared etomidate and carboetomidate effects on human N-methyl-d-aspartate receptors or neuronal nicotinic acetylcholine receptors (nnAChRs) expressed in Xenopus oocytes, using 2-microelectrode voltage clamp electrophysiology. RESULTS Etomidate did not affect either type of receptor at clinically relevant concentrations, whereas carboetomidate concentrations near 50% effective concentration for anesthesia significantly inhibited nnAChRs. CONCLUSIONS Compared with etomidate, carboetomidate's higher hydrophobicity is associated with greater inhibition of nnAChRs.
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Affiliation(s)
- David W Pierce
- Department of Anesthesia, Critical Care and Pain Medicine, Jackson 444, Massachusetts General Hospital, 55 Fruit St., Boston, MA 02114, USA
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