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Monarca L, Ragonese F, Biagini A, Sabbatini P, Pacini M, Zucchi A, Spaccapelo R, Ferrari P, Nicolini A, Fioretti B. Electrophysiological Impact of SARS-CoV-2 Envelope Protein in U251 Human Glioblastoma Cells: Possible Implications in Gliomagenesis? Int J Mol Sci 2024; 25:6669. [PMID: 38928376 PMCID: PMC11203726 DOI: 10.3390/ijms25126669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 05/28/2024] [Accepted: 06/11/2024] [Indexed: 06/28/2024] Open
Abstract
SARS-CoV-2 is the causative agent of the COVID-19 pandemic, the acute respiratory disease which, so far, has led to over 7 million deaths. There are several symptoms associated with SARS-CoV-2 infections which include neurological and psychiatric disorders, at least in the case of pre-Omicron variants. SARS-CoV-2 infection can also promote the onset of glioblastoma in patients without prior malignancies. In this study, we focused on the Envelope protein codified by the virus genome, which acts as viroporin and that is reported to be central for virus propagation. In particular, we characterized the electrophysiological profile of E-protein transfected U251 and HEK293 cells through the patch-clamp technique and FURA-2 measurements. Specifically, we observed an increase in the voltage-dependent (Kv) and calcium-dependent (KCa) potassium currents in HEK293 and U251 cell lines, respectively. Interestingly, in both cellular models, we observed a depolarization of the mitochondrial membrane potential in accordance with an alteration of U251 cell growth. We, therefore, investigated the transcriptional effect of E protein on the signaling pathways and found several gene alterations associated with apoptosis, cytokines and WNT pathways. The electrophysiological and transcriptional changes observed after E protein expression could explain the impact of SARS-CoV-2 infection on gliomagenesis.
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Affiliation(s)
- Lorenzo Monarca
- Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy; (L.M.); (F.R.); (A.B.); (P.S.)
- Department of Medicine and Surgery, Perugia Medical School, University of Perugia, 06132 Perugia, Italy;
| | - Francesco Ragonese
- Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy; (L.M.); (F.R.); (A.B.); (P.S.)
| | - Andrea Biagini
- Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy; (L.M.); (F.R.); (A.B.); (P.S.)
- Department of Medicine and Surgery, Perugia Medical School, University of Perugia, 06132 Perugia, Italy;
| | - Paola Sabbatini
- Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy; (L.M.); (F.R.); (A.B.); (P.S.)
| | - Matteo Pacini
- Urology Unit, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy; (M.P.); (A.Z.)
| | - Alessandro Zucchi
- Urology Unit, Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, 56126 Pisa, Italy; (M.P.); (A.Z.)
| | - Roberta Spaccapelo
- Department of Medicine and Surgery, Perugia Medical School, University of Perugia, 06132 Perugia, Italy;
- Interuniversity Consortium for Biotechnology (C.I.B.), 34148 Trieste, Italy
| | - Paola Ferrari
- Department of Oncology, Transplantations and New Technologies in Medicine, University of Pisa, 56126 Pisa, Italy;
| | - Andrea Nicolini
- Department of Oncology, Transplantations and New Technologies in Medicine, University of Pisa, 56126 Pisa, Italy;
| | - Bernard Fioretti
- Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy; (L.M.); (F.R.); (A.B.); (P.S.)
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2
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Pethe A, Hamze M, Giannaki M, Heimrich B, Medina I, Hartmann AM, Roussa E. K +/Cl - cotransporter 2 (KCC2) and Na +/ HCO3- cotransporter 1 (NBCe1) interaction modulates profile of KCC2 phosphorylation. Front Cell Neurosci 2023; 17:1253424. [PMID: 37881493 PMCID: PMC10595033 DOI: 10.3389/fncel.2023.1253424] [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: 07/05/2023] [Accepted: 09/07/2023] [Indexed: 10/27/2023] Open
Abstract
K+/Cl- cotransporter 2 (KCC2) is a major Cl- extruder in mature neurons and is responsible for the establishment of low intracellular [Cl-], necessary for fast hyperpolarizing GABAA-receptor mediated synaptic inhibition. Electrogenic sodium bicarbonate cotransporter 1 (NBCe1) is a pH regulatory protein expressed in neurons and glial cells. An interactome study identified NBCe1 as a possible interaction partner of KCC2. In this study, we investigated the putative effect of KCC2/NBCe1 interaction in baseline and the stimulus-induced phosphorylation pattern and function of KCC2. Primary mouse hippocampal neuronal cultures from wildtype (WT) and Nbce1-deficient mice, as well as HEK-293 cells stably transfected with KCC2WT, were used. The results show that KCC2 and NBCe1 are interaction partners in the mouse brain. In HEKKCC2 cells, pharmacological inhibition of NBCs with S0859 prevented staurosporine- and 4-aminopyridine (4AP)-induced KCC2 activation. In mature cultures of hippocampal neurons, however, S0859 completely inhibited postsynaptic GABAAR and, thus, could not be used as a tool to investigate the role of NBCs in GABA-dependent neuronal networks. In Nbce1-deficient immature hippocampal neurons, baseline phosphorylation of KCC2 at S940 was downregulated, compared to WT, and exposure to staurosporine failed to reduce pKCC2 S940 and T1007. In Nbce1-deficient mature neurons, baseline levels of pKCC2 S940 and T1007 were upregulated compared to WT, whereas after 4AP treatment, pKCC2 S940 was downregulated, and pKCC2 T1007 was further upregulated. Functional experiments showed that the levels of GABAAR reversal potential, baseline intracellular [Cl-], Cl- extrusion, and baseline intracellular pH were similar between WT and Nbce1-deficient neurons. Altogether, our data provide a primary description of the properties of KCC2/NBCe1 protein-protein interaction and implicate modulation of stimulus-mediated phosphorylation of KCC2 by NBCe1/KCC2 interaction-a mechanism with putative pathophysiological relevance.
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Affiliation(s)
- Abhishek Pethe
- Department of Molecular Embryology, Faculty of Medicine, Institute for Anatomy and Cell Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Mira Hamze
- INMED, INSERM, Aix-Marseille University, Marseille, France
| | - Marina Giannaki
- Department of Molecular Embryology, Faculty of Medicine, Institute for Anatomy and Cell Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Bernd Heimrich
- Department of Neuroanatomy, Faculty of Medicine, Institute for Anatomy and Cell Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Igor Medina
- INMED, INSERM, Aix-Marseille University, Marseille, France
| | - Anna-Maria Hartmann
- Division of Neurogenetics, Faculty VI, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
| | - Eleni Roussa
- Department of Molecular Embryology, Faculty of Medicine, Institute for Anatomy and Cell Biology, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
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3
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Li L, Liu Z, Yang H, Li Y, Zeng Q, Chen L, Liu Y, Chen Y, Zhu F, Cao D, Hu J, Shen X. Investigation of novel de novo KCNC2 variants causing severe developmental and early-onset epileptic encephalopathy. Seizure 2022; 101:218-224. [PMID: 36087422 DOI: 10.1016/j.seizure.2022.09.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 09/01/2022] [Accepted: 09/03/2022] [Indexed: 10/14/2022] Open
Abstract
Purpose The voltage-gated potassium channel Kv3.2, encoded by KCNC2, facilitates fast-spiking GABAergic interneurons to fire action potentials at high frequencies. It is pivotal to maintaining excitation/inhibition balance in mammalian brains. This study identified two novel de novo KCNC2 variants, p.Pro470Ser (P470S) and p.Phe382Leu (F382L), in patients with early onset developmental and epileptic encephalopathy (DEE). Methods To examine the molecular basis of DEE, we studied the functional characteristics of variant channels using patch-clamp techniques and computational modeling. Results Whole-cell patch clamp recordings from infected HEK293 cells revealed that channel activation and deactivation kinetics strongly decreased in both Kv3.2 P470S and F382L variant channels. This decrease also occurred in Kv3.2 p.Val471Leu (V471L) channels, known to be associated with DEE. In addition, Kv3.2 F382L and V471L variants exhibited a significant increase in channel conductance and a ∼20 mV negative shift in the threshold for voltage-dependent activation. Simulations of model GABAergic interneurons revealed that all variants decreased neuronal firing frequency. Thus, the variants' net loss-of-function effects disinhibited neural networks. Conclusion Our findings provide compelling evidence supporting the role of KCNC2 as a disease-causing gene in human neurodevelopmental delay and epilepsy.
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Affiliation(s)
- Lin Li
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Zili Liu
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China
| | - Haiyang Yang
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China; Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, CAS Center for Excellence in Brain Science and Intelligence Technology, Shenzhen, Guangdong 518055, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Li
- University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, CAS, Beijing 100101, China
| | - Qi Zeng
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Li Chen
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Yidi Liu
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Yan Chen
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Fengjun Zhu
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Dezhi Cao
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China; Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Jun Hu
- Department of Pediatrics, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, China.
| | - Xuefeng Shen
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China.
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Archana GM, Arunkumar RC, Omkumar RV. Assays for L-type voltage gated calcium channels. Anal Biochem 2022; 656:114827. [PMID: 35964733 DOI: 10.1016/j.ab.2022.114827] [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: 06/16/2021] [Revised: 07/10/2022] [Accepted: 07/19/2022] [Indexed: 11/01/2022]
Abstract
Voltage gated calcium channels (VGCCs) are pursued as drug targets for neurodegenerative and cardiovascular diseases. High throughput drug screening targeting VGCCs depends on patch-clamp electrophysiology or fluorophore-based calcium imaging that requires powerful equipment and specialized expertise thus leading to cost escalation. Moreover, VGCC needs to be transfected into cell lines such as HEK-293. We report the presence of L-type VGCC (L-VGCC) subunit proteins, Cav1.2, α2δ and β in HEK-293 cells and the application of simple methods for its assay. Endogenous expression of the channel in HEK-293 cells overcomes the need for transfection. L-VGCC in HEK-293 cells was activated either by the agonist, BayK8644 or by KCl-mediated depolarization. Activity was detected using the calcium sensing probe, GCaMP6m by live imaging. L-VGCC activity induced enhancement in GCaMP6m fluorescence returned to baseline corresponding to channel-closure. Activity was also shown using a methodology involving end-point detection of the calcium dependent interaction of α-CaMKII with NMDA receptor subunit GluN2B sequence. This methodology further simplifies the assay as it eliminates the need for real time imaging. Activation was blocked by the specific L-type VGCC antagonist, nifedipine. Finding the protein and activity of L-VGCC in HEK-293 cells offers commercially viable assays for drug screening.
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Affiliation(s)
- G M Archana
- Molecular Neurobiology Division, Rajiv Gandhi Centre for Biotechnology, Thycaud, P. O., Thiruvananthapuram, 695014, India; University of Kerala, India
| | - R C Arunkumar
- Molecular Neurobiology Division, Rajiv Gandhi Centre for Biotechnology, Thycaud, P. O., Thiruvananthapuram, 695014, India; University of Kerala, India
| | - R V Omkumar
- Molecular Neurobiology Division, Rajiv Gandhi Centre for Biotechnology, Thycaud, P. O., Thiruvananthapuram, 695014, India.
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Zhang J, Yuan H, Yao X, Chen S. Endogenous ion channels expressed in human embryonic kidney (HEK-293) cells. Pflugers Arch 2022; 474:665-680. [PMID: 35567642 DOI: 10.1007/s00424-022-02700-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/25/2022] [Accepted: 04/30/2022] [Indexed: 12/21/2022]
Abstract
Mammalian expression systems, particularly the human embryonic kidney (HEK-293) cells, combined with electrophysiological studies, have greatly benefited our understanding of the function, characteristic, and regulation of various ion channels. It was previously assumed that the existence of endogenous ion channels in native HEK-293 cells could be negligible. Still, more and more ion channels are gradually reported in native HEK-293 cells, which should draw our attention. In this regard, we summarize the different ion channels that are endogenously expressed in HEK-293 cells, including voltage-gated Na+ channels, Ca2+ channels, K+ channels, Cl- channels, nonselective cation channels, TRP channels, acid-sensitive ion channels, and Piezo channels, which may complicate the recording of the heterogeneously expressed ion channels to a certain degree. We noted that the expression patterns and channel profiles varied with different studies, which may be due to the distinct originality of the cells, cell culture conditions, passage numbers, and different recording protocols. Therefore, a better knowledge of endogenous ion channels may help minimize potential problems in characterizing heterologously expressed ion channels. Based on this, it is recommended that HEK-293 cells from unknown sources should be examined before transfection for the characterization of their functional profile, especially when the expression level of exogenous ion channels does not overwhelm the endogenous ion channels largely, or the current amplitude is not significantly higher than the native currents.
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Affiliation(s)
- Jun Zhang
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Huikai Yuan
- Department of General Surgery, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Xiaoqiang Yao
- School of Biomedical Sciences and Li Ka Shing Institute of Health Science, The Chinese University of Hong Kong, Hong Kong, China
| | - Shuo Chen
- Department of Biopharmaceutical Sciences, School of Pharmacy, Harbin Medical University at Daqing, No. 39 Xinyang Rd, High-tech District, Daqing, 163319, Heilongjiang Province, China.
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Hoekstra M, van Ginneken ACG, Wilders R, Verkerk AO. HCN4 current during human sinoatrial node-like action potentials. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:105-118. [PMID: 34153331 DOI: 10.1016/j.pbiomolbio.2021.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 04/07/2021] [Accepted: 05/14/2021] [Indexed: 12/20/2022]
Abstract
BACKGROUND Despite the many studies carried out over the past 40 years, the contribution of the HCN4 encoded hyperpolarization-activated 'funny' current (If) to pacemaker activity in the mammalian sinoatrial node (SAN), and the human SAN in particular, is still controversial and not fully established. OBJECTIVE To study the contribution of If to diastolic depolarization of human SAN cells and its dependence on heart rate, cAMP levels, and atrial load. METHODS HCN4 channels were expressed in human cardiac myocyte progenitor cells (CMPCs) and HCN4 currents assessed using perforated patch-clamp in traditional voltage clamp mode and during action potential clamp with human SAN-like action potential waveforms with 500-1500 ms cycle length, in absence or presence of forskolin to mimic β-adrenergic stimulation and a -15 mV command potential offset to mimic atrial load. RESULTS Forskolin significantly increased the fully-activated HCN4 current density at -140 mV by 14% and shifted the steady-state activation curve by +7.4 mV without affecting its slope. In addition, forskolin significantly accelerated current activation but slowed deactivation. The HCN4 current did not completely deactivate before the subsequent diastolic depolarization during action potential clamp. The amplitude of HCN4 current increased with increasing cycle length, was significantly larger in the presence of forskolin at all cycle lengths, and was significantly increased upon the negative offset to the command potential. CONCLUSIONS If is active during a human SAN action potential waveform and its amplitude is modulated by heart rate, β-adrenergic stimulation, and diastolic voltage range, such that If is under delicate control.
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Affiliation(s)
- Maaike Hoekstra
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Antoni C G van Ginneken
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Ronald Wilders
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands.
| | - Arie O Verkerk
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands; Department of Experimental Cardiology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
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Cabrera‐Garcia D, Bekdash R, Abbott GW, Yazawa M, Harrison NL. The envelope protein of SARS-CoV-2 increases intra-Golgi pH and forms a cation channel that is regulated by pH. J Physiol 2021; 599:2851-2868. [PMID: 33709461 PMCID: PMC8251088 DOI: 10.1113/jp281037] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Accepted: 03/02/2021] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS We report a novel method for the transient expression of SARS-CoV-2 envelope (E) protein in intracellular organelles and the plasma membrane of mammalian cells and Xenopus oocytes. Intracellular expression of SARS-CoV-2 E protein increases intra-Golgi pH. By targeting the SARS-CoV-2 E protein to the plasma membrane, we show that it forms a cation channel, viroporin, that is modulated by changes of pH. This method for studying the activity of viroporins may facilitate screening for new antiviral drugs to identify novel treatments for COVID-19. ABSTRACT The envelope (E) protein of coronaviruses such as SARS-CoV-1 is proposed to form an ion channel or viroporin that participates in viral propagation and pathogenesis. Here we developed a technique to study the E protein of SARS-CoV-2 in mammalian cells by directed targeting using a carboxyl-terminal fluorescent protein tag, mKate2. The wild-type SARS-CoV-2 E protein can be trafficked to intracellular organelles, notably the endoplasmic reticulum-Golgi intermediate complex, where its expression increases pH inside the organelle. We also succeeded in targeting SARS-CoV-2 E to the plasma membrane, which enabled biophysical analysis using whole-cell patch clamp recording in a mammalian cell line, HEK 293 cells, and two-electrode voltage clamp electrophysiology in Xenopus oocytes. The results suggest that the E protein forms an ion channel that is permeable to monovalent cations such as Na+ , Cs+ and K+ . The E current is nearly time- and voltage-independent when E protein is expressed in mammalian cells, and is modulated by changes of pH. At pH 6.0 and 7.4, the E protein current is activated, whereas at pH 8.0 and 9.0, the amplitude of E protein current is reduced, and in oocytes the inward E current fades at pH 9 in a time- and voltage-dependent manner. Using this directed targeting method and electrophysiological recordings, potential inhibitors of the E protein can be screened and subsequently investigated for antiviral activity against SARS-CoV-2 in vitro and possible efficacy in treating COVID-19.
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Affiliation(s)
| | - Ramsey Bekdash
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
- Columbia Stem Cell Initiative, Department of Rehabilitation and Regenerative MedicineColumbia UniversityNew YorkNYUSA
| | - Geoffrey W. Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of MedicineUniversity of CaliforniaIrvineCAUSA
| | - Masayuki Yazawa
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
- Columbia Stem Cell Initiative, Department of Rehabilitation and Regenerative MedicineColumbia UniversityNew YorkNYUSA
| | - Neil L. Harrison
- Department of AnesthesiologyColumbia UniversityNew YorkNYUSA
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
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8
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Wu T, Nguyen HX, Bursac N. In vitro discovery of novel prokaryotic ion channel candidates for antiarrhythmic gene therapy. Methods Enzymol 2021; 654:407-434. [PMID: 34120724 DOI: 10.1016/bs.mie.2021.03.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Sudden cardiac death continues to have a devastating impact on public health prompting the continued efforts to develop more effective therapies for cardiac arrhythmias. Among different approaches to normalize function of ion channels and prevent arrhythmogenic remodeling of tissue substrate, cardiac cell and gene therapies are emerging as promising strategies to restore and maintain normal heart rhythm. Specifically, the ability to genetically enhance electrical excitability of diseased hearts through voltage-gated sodium channel (VGSC) gene transfer could improve velocity of action potential conduction and act to stop reentrant circuits underlying sustained arrhythmias. For this purpose, prokaryotic VGSC genes are promising therapeutic candidates due to their small size (<1kb) and potential to be effectively packaged in adeno-associated viral (AAV) vectors and delivered to cardiomyocytes for stable, long-term expression. This article describes a versatile method to discover and characterize novel prokaryotic ion channels for use in gene and cell therapies for heart disease including cardiac arrhythmias. Detailed protocols are provided for: (1) identification of potential ion channel candidates from large genomic databases, (2) candidate screening and characterization using site-directed mutagenesis and engineered human excitable cell system and, (3) candidate validation using electrophysiological techniques and an in vitro model of impaired cardiac impulse conduction.
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Affiliation(s)
- Tianyu Wu
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Hung X Nguyen
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, NC, United States.
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9
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Gu K, Qian D, Qin H, Cui C, Fernando WCHA, Wang D, Wang J, Cao K, Chen M. A novel mutation in KCNH2 yields loss-of-function of hERG potassium channel in long QT syndrome 2. Pflugers Arch 2021; 473:219-229. [PMID: 33449212 DOI: 10.1007/s00424-021-02518-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 12/24/2020] [Accepted: 01/07/2021] [Indexed: 12/16/2022]
Abstract
Mutations in hERG (human ether-à-go-go-related gene) potassium channel are closely associated with long QT syndromes. By direct Sanger sequencing, we identified a novel KCNH2 mutation W410R in the patient with long QT syndrome 2 (LQT2). However, the electrophysiological functions of this mutation remain unknown. In comparison to hERGWT channels, hERGW410R channels have markedly decreased total and surface expressions. W410R mutation dramatically reduces hERG channel currents (IKr) and shifts its steady-state activation curve to depolarization. Moreover, hERGW410R channels make dominant-negative effects on hERGWT channels. Significantly, we find hERG channel blocker E-4031 could partially rescue the function of hERGW410R channels by increasing the membrane expression. By using in silico model, we reveal that hERGW410R channels obviously elongate the repolarization of human ventricular myocyte action potentials. Collectively, W410R mutation decreases the currents of hERG channel, because of diminished membrane expression of mutant channels, that subsequently leads to elongated repolarization of cardiomyocyte, which might induce the pathogenesis of LQT2. Furthermore, E-4031 could partially rescue the decreased activity of hERGW410R channels. Thus, our work identifies a novel loss-of-function mutation in KCNH2 gene, which might provide a rational basis for the management of LQT2.
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Affiliation(s)
- Kai Gu
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China
| | - Duoduo Qian
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China
| | - Huiyuan Qin
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China
| | - Chang Cui
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China
| | - W C Hewith A Fernando
- Department of Physiology, Nanjing Medical University, 101 Longmian Ave, Nanjing, 211166, China
| | - Daowu Wang
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China.,State Key Laboratory of Reproductive Medicine, the Centre for Clinical Reproductive Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, China
| | - Juejin Wang
- Department of Physiology, Nanjing Medical University, 101 Longmian Ave, Nanjing, 211166, China.
| | - Kejiang Cao
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China.
| | - Minglong Chen
- Department of Cardiology, The First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029, China.
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10
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Cserép C, Pósfai B, Lénárt N, Fekete R, László ZI, Lele Z, Orsolits B, Molnár G, Heindl S, Schwarcz AD, Ujvári K, Környei Z, Tóth K, Szabadits E, Sperlágh B, Baranyi M, Csiba L, Hortobágyi T, Maglóczky Z, Martinecz B, Szabó G, Erdélyi F, Szipőcs R, Tamkun MM, Gesierich B, Duering M, Katona I, Liesz A, Tamás G, Dénes Á. Microglia monitor and protect neuronal function through specialized somatic purinergic junctions. Science 2019; 367:528-537. [PMID: 31831638 DOI: 10.1126/science.aax6752] [Citation(s) in RCA: 366] [Impact Index Per Article: 73.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 10/14/2019] [Accepted: 12/03/2019] [Indexed: 12/16/2022]
Abstract
Microglia are the main immune cells in the brain and have roles in brain homeostasis and neurological diseases. Mechanisms underlying microglia-neuron communication remain elusive. Here, we identified an interaction site between neuronal cell bodies and microglial processes in mouse and human brain. Somatic microglia-neuron junctions have a specialized nanoarchitecture optimized for purinergic signaling. Activity of neuronal mitochondria was linked with microglial junction formation, which was induced rapidly in response to neuronal activation and blocked by inhibition of P2Y12 receptors. Brain injury-induced changes at somatic junctions triggered P2Y12 receptor-dependent microglial neuroprotection, regulating neuronal calcium load and functional connectivity. Thus, microglial processes at these junctions could potentially monitor and protect neuronal functions.
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Affiliation(s)
- Csaba Cserép
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Balázs Pósfai
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary.,Szentágothai János Doctoral School of Neuroscience, Semmelweis University, Budapest, Hungary
| | - Nikolett Lénárt
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Rebeka Fekete
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary.,Szentágothai János Doctoral School of Neuroscience, Semmelweis University, Budapest, Hungary
| | - Zsófia I László
- Szentágothai János Doctoral School of Neuroscience, Semmelweis University, Budapest, Hungary.,Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Zsolt Lele
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Barbara Orsolits
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Gábor Molnár
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Szeged, Hungary
| | - Steffanie Heindl
- Institute for Stroke and Dementia Research, Ludwig-Maximilians-University, Munich, Germany
| | - Anett D Schwarcz
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Katinka Ujvári
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Zsuzsanna Környei
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Krisztina Tóth
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary.,Szentágothai János Doctoral School of Neuroscience, Semmelweis University, Budapest, Hungary
| | - Eszter Szabadits
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Beáta Sperlágh
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Budapest, Hungary
| | - Mária Baranyi
- Laboratory of Molecular Pharmacology, Institute of Experimental Medicine, Budapest, Hungary
| | - László Csiba
- MTA-DE Cerebrovascular and Neurodegenerative Research Group, Department of Neurology, University of Debrecen, Debrecen, Hungary
| | - Tibor Hortobágyi
- Institute of Pathology, Faculty of Medicine, University of Szeged, Szeged, Hungary.,Department of Old Age Psychiatry, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.,Centre for Age-Related Medicine, SESAM, Stavanger University Hospital, Stavanger, Norway
| | - Zsófia Maglóczky
- Human Brain Research Laboratory, Institute of Experimental Medicine, Budapest, Hungary
| | - Bernadett Martinecz
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary
| | - Gábor Szabó
- Medical Gene Technology Unit, Institute of Experimental Medicine, Budapest, Hungary
| | - Ferenc Erdélyi
- Medical Gene Technology Unit, Institute of Experimental Medicine, Budapest, Hungary
| | - Róbert Szipőcs
- Institute for Solid State Physics and Optics of Wigner RCP, Budapest, Hungary
| | - Michael M Tamkun
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Benno Gesierich
- Institute for Stroke and Dementia Research, Ludwig-Maximilians-University, Munich, Germany
| | - Marco Duering
- Institute for Stroke and Dementia Research, Ludwig-Maximilians-University, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - István Katona
- Momentum Laboratory of Molecular Neurobiology, Institute of Experimental Medicine, Budapest, Hungary
| | - Arthur Liesz
- Institute for Stroke and Dementia Research, Ludwig-Maximilians-University, Munich, Germany.,Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Gábor Tamás
- MTA-SZTE Research Group for Cortical Microcircuits of the Hungarian Academy of Sciences, Department of Physiology, Anatomy and Neuroscience, University of Szeged, Szeged, Hungary
| | - Ádám Dénes
- Momentum Laboratory of Neuroimmunology, Institute of Experimental Medicine, Budapest, Hungary.
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11
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Ponce A, Castillo A, Hinojosa L, Martinez-Rendon J, Cereijido M. The expression of endogenous voltage-gated potassium channels in HEK293 cells is affected by culture conditions. Physiol Rep 2019; 6:e13663. [PMID: 29665277 PMCID: PMC5903699 DOI: 10.14814/phy2.13663] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 02/23/2018] [Accepted: 03/05/2018] [Indexed: 01/06/2023] Open
Abstract
HEK293 cells are widely used as a host for expression of heterologous proteins; yet, little care has been taken to characterize their endogenous membrane components, including ion channels. In this work, we aimed to describe the biophysical and pharmacological properties of endogenous, voltage‐dependent potassium currents (IKv). We also examined how its expression depends on culture conditions. We used the electrophysiological technique of whole‐cell patch clamp to record ion currents from HEK293 cells. We found that HEK cells express endogenous, voltage‐dependent potassium currents. We also found that diverse culture conditions, such as the passage number, the cell density, the type of serum that complements the culture media and the substratum, affect the magnitude and shape of IKv, resulting from the relative contribution of fast, slow, and noninactivating component currents. Incubation of cells in mature monolayers with trypsin–EDTA, notoriously reduces the magnitude and modifies the shape of voltage‐dependent potassium endogenous currents; nonetheless HEK cells recover IKv′s magnitude and shape within 6 h after replating, with a process that requires synthesis of new mRNA and protein subunits, as evidenced by the fact that actinomycin D and cycloheximide, inhibitors of synthesis of mRNA and protein, respectively, impair the recovery of IKv after trypsinization. In addition to be useful as a model expression system, HEK293 may be useful to understand how cells regulate the density of ion channels on the membrane.
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Affiliation(s)
- Arturo Ponce
- Department of Physiology, Biophysics and Neurosciences, Center For Research and Advanced Studies (Cinvestav), México D. F., México
| | - Aida Castillo
- Department of Physiology, Biophysics and Neurosciences, Center For Research and Advanced Studies (Cinvestav), México D. F., México
| | - Lorena Hinojosa
- Department of Physiology, Biophysics and Neurosciences, Center For Research and Advanced Studies (Cinvestav), México D. F., México
| | - Jacqueline Martinez-Rendon
- Department of Physiology, Biophysics and Neurosciences, Center For Research and Advanced Studies (Cinvestav), México D. F., México
| | - Marcelino Cereijido
- Department of Physiology, Biophysics and Neurosciences, Center For Research and Advanced Studies (Cinvestav), México D. F., México
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12
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N-Cinnamoylanthranilates as human TRPA1 modulators: Structure-activity relationships and channel binding sites. Eur J Med Chem 2019; 170:141-156. [DOI: 10.1016/j.ejmech.2019.02.074] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Revised: 02/27/2019] [Accepted: 02/27/2019] [Indexed: 01/14/2023]
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13
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Memon T, Yarishkin O, Reilly CA, Križaj D, Olivera BM, Teichert RW. trans-Anethole of Fennel Oil is a Selective and Nonelectrophilic Agonist of the TRPA1 Ion Channel. Mol Pharmacol 2019; 95:433-441. [PMID: 30679204 DOI: 10.1124/mol.118.114561] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2018] [Accepted: 01/18/2019] [Indexed: 11/22/2022] Open
Abstract
Transient receptor potential (TRP) cation channels are molecular targets of various natural products. TRPA1, a member of TRP channel family, is specifically activated by natural products such as allyl isothiocyanate (mustard oil), cinnamaldehyde (cinnamon), and allicin (garlic). In this study, we demonstrated that TRPA1 is also a target of trans-anethole in fennel oil (FO) and fennel seed extract. Similar to FO, trans-anethole selectively elicited calcium influx in TRPA1-expressing mouse sensory neurons of the dorsal root and trigeminal ganglia. These FO- and anethole-induced calcium responses were blocked by a selective TRPA1 channel antagonist, HC-030031. Moreover, both FO and trans-anethole induced calcium influx and transmembrane currents in HEK293 cells stably overexpressing human TRPA1 channels, but not in regular HEK293 cells. Mutation of the amino acids S873 and T874 binding site of human TRPA1 significantly attenuated channel activation by trans-anethole, whereas pretreating with glutathione, a nucleophile, did not. Conversely, activation of TRPA1 by the electrophile allyl isothiocyanate was abolished by glutathione, but was ostensibly unaffected by mutation of the ST binding site. Finally, it was found that trans-anethole was capable of desensitizing TRPA1, and unlike allyl isothiocyanate, it failed to induce nocifensive behaviors in mice. We conclude that trans-anethole is a selective, nonelectrophilic, and seemingly less-irritating agonist of TRPA1.
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Affiliation(s)
- Tosifa Memon
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
| | - Oleg Yarishkin
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
| | - Christopher A Reilly
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
| | - David Križaj
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
| | - Baldomero M Olivera
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
| | - Russell W Teichert
- Departments of Biology (T.M., B.M.O., R.W.T.), Pharmacology and Toxicology (T.M., C.A.R.), and Ophthalmology and Visual Sciences (O.Y., D.K.), University of Utah, Salt Lake City, Utah
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14
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Nguyen HX, Kirkton RD, Bursac N. Generation and customization of biosynthetic excitable tissues for electrophysiological studies and cell-based therapies. Nat Protoc 2018; 13:927-945. [PMID: 29622805 PMCID: PMC6050172 DOI: 10.1038/nprot.2018.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We describe a two-stage protocol to generate electrically excitable and actively conducting cell networks with stable and customizable electrophysiological phenotypes. Using this method, we have engineered monoclonally derived excitable tissues as a robust and reproducible platform to investigate how specific ion channels and mutations affect action potential (AP) shape and conduction. In the first stage of the protocol, we combine computational modeling, site-directed mutagenesis, and electrophysiological techniques to derive optimal sets of mammalian and/or prokaryotic ion channels that produce specific AP shape and conduction characteristics. In the second stage of the protocol, selected ion channels are stably expressed in unexcitable human cells by means of viral or nonviral delivery, followed by flow cytometry or antibiotic selection to purify the desired phenotype. This protocol can be used with traditional heterologous expression systems or primary excitable cells, and application of this method to primary fibroblasts may enable an alternative approach to cardiac cell therapy. Compared with existing methods, this protocol generates a well-defined, relatively homogeneous electrophysiological phenotype of excitable cells that facilitates experimental and computational studies of AP conduction and can decrease arrhythmogenic risk upon cell transplantation. Although basic cell culture and molecular biology techniques are sufficient to generate excitable tissues using the described protocol, experience with patch-clamp techniques is required to characterize and optimize derived cell populations.
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Affiliation(s)
- Hung X Nguyen
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA. Correspondence should be addressed to N.B. ()
| | - Robert D Kirkton
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA. Correspondence should be addressed to N.B. ()
| | - Nenad Bursac
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA. Correspondence should be addressed to N.B. ()
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15
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Voros O, Szilagyi O, Balajthy A, Somodi S, Panyi G, Hajdu P. The C-terminal HRET sequence of Kv1.3 regulates gating rather than targeting of Kv1.3 to the plasma membrane. Sci Rep 2018; 8:5937. [PMID: 29650988 PMCID: PMC5897520 DOI: 10.1038/s41598-018-24159-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 03/08/2018] [Indexed: 12/13/2022] Open
Abstract
Kv1.3 channels are expressed in several cell types including immune cells, such as T lymphocytes. The targeting of Kv1.3 to the plasma membrane is essential for T cell clonal expansion and assumed to be guided by the C-terminus of the channel. Using two point mutants of Kv1.3 with remarkably different features compared to the wild-type Kv1.3 (A413V and H399K having fast inactivation kinetics and tetraethylammonium-insensitivity, respectively) we showed that both Kv1.3 channel variants target to the membrane when the C-terminus was truncated right after the conserved HRET sequence and produce currents identical to those with a full-length C-terminus. The truncation before the HRET sequence (NOHRET channels) resulted in reduced membrane-targeting but non-functional phenotypes. NOHRET channels did not display gating currents, and coexpression with wild-type Kv1.3 did not rescue the NOHRET-A413V phenotype, no heteromeric current was observed. Interestingly, mutants of wild-type Kv1.3 lacking HRET(E) (deletion) or substituted with five alanines for the HRET(E) motif expressed current indistinguishable from the wild-type. These results demonstrate that the C-terminal region of Kv1.3 immediately proximal to the S6 helix is required for the activation gating and conduction, whereas the presence of the distal region of the C-terminus is not exclusively required for trafficking of Kv1.3 to the plasma membrane.
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Affiliation(s)
- Orsolya Voros
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Orsolya Szilagyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - András Balajthy
- Department of Pediatrics, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Sándor Somodi
- Department of Internal Medicine, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 1 Egyetem sq., 4032, Hungary. MTA-DE-NAP B Ion Channel Structure-Function Research Group, RCMM, University of Debrecen, 400, Debrecen, Hungary
| | - Péter Hajdu
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary. .,Department of Biophysics and Cell Biology, Faculty of Dentistry, University of Debrecen, 400, 1 Egyetem sq., Debrecen, 4032, Hungary.
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16
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Schrapers KT, Sponder G, Liebe F, Liebe H, Stumpff F. The bovine TRPV3 as a pathway for the uptake of Na +, Ca 2+, and NH 4+. PLoS One 2018; 13:e0193519. [PMID: 29494673 PMCID: PMC5832270 DOI: 10.1371/journal.pone.0193519] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2017] [Accepted: 02/13/2018] [Indexed: 12/22/2022] Open
Abstract
Absorption of ammonia from the gastrointestinal tract results in problems that range from hepatic encephalopathy in humans to poor nitrogen efficiency of cattle with consequences for the global climate. Previous studies on epithelia and cells from the native ruminal epithelium suggest functional involvement of the bovine homologue of TRPV3 (bTRPV3) in ruminal NH4+ transport. Since the conductance of TRP channels to NH4+ has never been studied, bTRPV3 was overexpressed in HEK-293 cells and investigated using the patch-clamp technique and intracellular calcium imaging. Control cells contained the empty construct. Divalent cations blocked the conductance for monovalent cations in both cell types, with effects higher in cells expressing bTRPV3. In bTRPV3 cells, but not in controls, menthol, thymol, carvacrol, or 2-APB stimulated whole cell currents mediated by Na+, Cs+, NH4+, and K+, with a rise in intracellular Ca2+ observed in response to menthol. While only 25% of control patches showed single-channel events (with a conductance of 40.8 ± 11.9 pS for NH4+ and 25.0 ± 5.8 pS for Na+), 90% of bTRPV3 patches showed much larger conductances of 127.8 ± 4.2 pS for Na+, 240.1 ± 3.6 pS for NH4+, 34.0 ± 1.7 pS for Ca2+, and ~ 36 pS for NMDG+. Open probability, but not conductance, rose with time after patch excision. In conjunction with previous research, we suggest that bTRPV3 channels may play a role in the transport of Na+, K+, Ca2+ and NH4+ across the rumen with possible repercussions for understanding the function of TRPV3 in other epithelia.
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Affiliation(s)
- Katharina T. Schrapers
- Institute of Veterinary Physiology, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Gerhard Sponder
- Institute of Veterinary Physiology, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Franziska Liebe
- Institute of Veterinary Physiology, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Hendrik Liebe
- Institute of Veterinary Physiology, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
| | - Friederike Stumpff
- Institute of Veterinary Physiology, Faculty of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany
- * E-mail:
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17
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Wu M, White HV, Boehm BA, Meriney CJ, Kerrigan K, Frasso M, Liang M, Gotway EM, Wilcox MR, Johnson JW, Wipf P, Meriney SD. New Cav2 calcium channel gating modifiers with agonist activity and therapeutic potential to treat neuromuscular disease. Neuropharmacology 2017; 131:176-189. [PMID: 29246857 DOI: 10.1016/j.neuropharm.2017.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 11/28/2017] [Accepted: 12/10/2017] [Indexed: 12/13/2022]
Abstract
Voltage-gated calcium channels (VGCCs) are critical regulators of many cellular functions, including the activity-dependent release of chemical neurotransmitter from nerve terminals. At nerve terminals, the Cav2 family of VGCCs are closely positioned with neurotransmitter-containing synaptic vesicles. The relationship between calcium ions and transmitter release is such that even subtle changes in calcium flux through VGCCs have a strong influence on the magnitude of transmitter released. Therefore, modulators of the calcium influx at nerve terminals have the potential to strongly affect transmitter release at synapses. We have previously developed novel Cav2-selective VGCC gating modifiers (notably GV-58) that slow the deactivation of VGCC current, increasing total calcium ion flux. Here, we describe ten new gating modifiers based on the GV-58 structure that extend our understanding of the structure-activity relationship for this class of molecules and extend the range of modulation of channel activities. In particular, we show that one of these new compounds (MF-06) was more efficacious than GV-58, another (KK-75) acts more quickly on VGCCs than GV-58, and a third (KK-20) has a mix of increased speed and efficacy. A subset of these new VGCC agonist gating modifiers can increase transmitter release during action potentials at neuromuscular synapses, and as such, show potential as therapeutics for diseases with a presynaptic deficit that results in neuromuscular weakness. Further, several of these new compounds can be useful tool compounds for the study of VGCC gating and function.
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Affiliation(s)
- Man Wu
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Hayley V White
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Blake A Boehm
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Christopher J Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Kaylan Kerrigan
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Michael Frasso
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Mary Liang
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Erika M Gotway
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Madeleine R Wilcox
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Jon W Johnson
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Peter Wipf
- Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Stephen D Meriney
- Department of Neuroscience, Center for Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, United States.
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18
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Jenson LJ, Sun B, Bloomquist JR. Voltage-sensitive potassium channels expressed after 20-Hydroxyecdysone treatment of a mosquito cell line. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2017; 87:75-80. [PMID: 28668511 DOI: 10.1016/j.ibmb.2017.06.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 06/24/2017] [Accepted: 06/26/2017] [Indexed: 06/07/2023]
Abstract
The goal of this research was to express receptors and ion channels in hormone-treated insect cell lines. Treatment of Anopheles gambiae Sua1B cells with 20-hydroxyecdysone showed an inhibition of cell growth over a time course of three days, with no change in cellular morphology. The effect of 20-hydroxyecdysone was enhanced in the presence of the potassium channel blocker 4-aminopyridine, but not tetraethylammonium. Concentration-response curves of 4-aminopyridine in the presence of 42 μM (1 mg/ml) 20-hydroxyecdysone showed similar IC50 values (6-10 μM) across 3 day exposures. Whole cell patch clamp confirmed the expression of delayed-rectifier (Kv2) potassium channels in hormone-supplemented Sua1B cells, whereas untreated Sua1B cells showed no evidence of Kv2 expression. The hormone-induced expression of Kv2 channels occurred in as little as 4 h after treatment, but were not observed after 24 h of exposure to 20-hydroxyecdysone, suggesting they played a role in cell death. The expressed channels had current-voltage relationships diagnostic for the Kv2 subtype, and were inhibited with an IC50 = 13 mM of tetraethylammonium. Overall, these parameters were similar to Anopheles gambiae Kv2 potassium channels expressed in HEK-293 cells. The induced presence of ion channels (and possibly receptors) in these cells has potential utility for high throughput screening and basic neuroscience research.
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Affiliation(s)
- Lacey J Jenson
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32601, USA; Bedoukian Research Inc., 21 Finance Drive, Danbury, CT, 06810, USA
| | - Baonan Sun
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32601, USA
| | - Jeffrey R Bloomquist
- Emerging Pathogens Institute, Department of Entomology and Nematology, University of Florida, Gainesville, FL, 32601, USA.
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19
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Chan FHL, Yang R, Lai KWC. Development of the Electric Equivalent Model for the Cytoplasmic Microinjection of Small Adherent Cells. MICROMACHINES 2017; 8:mi8070216. [PMID: 30400407 PMCID: PMC6189767 DOI: 10.3390/mi8070216] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 06/25/2017] [Accepted: 07/04/2017] [Indexed: 11/16/2022]
Abstract
A novel approach utilizing current feedback for the cytoplasmic microinjection of biological cells is proposed. In order to realize the cytoplasmic microinjection on small adherent cells (diameter < 30 μm and thickness < 10 μm), an electrical model is built and analyzed according to the electrochemical properties of target cells. In this study, we have verified the effectiveness of the current measurement for monitoring the injection process and the study of ion channel activities for verifying the cell viability of the cells after the microinjection.
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Affiliation(s)
- Florence Hiu Ling Chan
- Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China.
- Centre for Robotics and Automation, City University of Hong Kong, Hong Kong, China.
| | - Runhuai Yang
- Department of Biomedical Engineering, Anhui Medical University, Hefei 230032, China.
| | - King Wai Chiu Lai
- Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Hong Kong, China.
- Centre for Robotics and Automation, City University of Hong Kong, Hong Kong, China.
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20
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Soderlund DM, Tan J, He B. Functional reconstitution of rat Na v1.6 sodium channels in vitro for studies of pyrethroid action. Neurotoxicology 2017; 60:142-149. [PMID: 27013268 PMCID: PMC5031521 DOI: 10.1016/j.neuro.2016.03.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Revised: 03/17/2016] [Accepted: 03/17/2016] [Indexed: 01/14/2023]
Abstract
The ability to reconstitute sodium channel function and pharmacology in vitro using cloned subunits of known structure has greatly enhanced our understanding of the action of pyrethroid insecticides at this target and the structural determinants of resistance and interspecies selectivity. However, the use of reconstituted channels raises three critical questions: (1) Which subunits and subunit combinations should be used? (2) Which heterologous expression system is preferred? (3) Which combination of subunits and expression system best represents the function of native neuronal channels in the organism of interest? This review considers these questions from the perspective of recent research in this laboratory on the action of pyrethroid insecticides on rat Nav1.6 sodium channels by comparing the effects of heteroligomeric complex composition on channel function and insecticide response when channels are expressed in either Xenopus oocytes or stably-transformed HEK293 cells. These comparisons provide new insight into the influence of cellular context on the functional and pharmacological properties of expressed channels, the modulatory effects of sodium channel auxiliary subunits on the action of pyrethroids, and the relative fidelity of the Xenopus oocyte and HEK293 cell expression systems as model systems for studying of channel function and pyrethroid action.
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Affiliation(s)
- David M Soderlund
- Department of Entomology, Cornell University, Geneva, NY 14456, USA.
| | | | - Bingjun He
- College of Life Sciences, Nankai University, Tianjin 300071, China
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21
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Modeling an Excitable Biosynthetic Tissue with Inherent Variability for Paired Computational-Experimental Studies. PLoS Comput Biol 2017; 13:e1005342. [PMID: 28107358 PMCID: PMC5291544 DOI: 10.1371/journal.pcbi.1005342] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 02/03/2017] [Accepted: 12/31/2016] [Indexed: 12/17/2022] Open
Abstract
To understand how excitable tissues give rise to arrhythmias, it is crucially necessary to understand the electrical dynamics of cells in the context of their environment. Multicellular monolayer cultures have proven useful for investigating arrhythmias and other conduction anomalies, and because of their relatively simple structure, these constructs lend themselves to paired computational studies that often help elucidate mechanisms of the observed behavior. However, tissue cultures of cardiomyocyte monolayers currently require the use of neonatal cells with ionic properties that change rapidly during development and have thus been poorly characterized and modeled to date. Recently, Kirkton and Bursac demonstrated the ability to create biosynthetic excitable tissues from genetically engineered and immortalized HEK293 cells with well-characterized electrical properties and the ability to propagate action potentials. In this study, we developed and validated a computational model of these excitable HEK293 cells (called “Ex293” cells) using existing electrophysiological data and a genetic search algorithm. In order to reproduce not only the mean but also the variability of experimental observations, we examined what sources of variation were required in the computational model. Random cell-to-cell and inter-monolayer variation in both ionic conductances and tissue conductivity was necessary to explain the experimentally observed variability in action potential shape and macroscopic conduction, and the spatial organization of cell-to-cell conductance variation was found to not impact macroscopic behavior; the resulting model accurately reproduces both normal and drug-modified conduction behavior. The development of a computational Ex293 cell and tissue model provides a novel framework to perform paired computational-experimental studies to study normal and abnormal conduction in multidimensional excitable tissue, and the methodology of modeling variation can be applied to models of any excitable cell. One of the major challenges in trying to understand how arrhythmias can form in cardiac tissue is studying how the electrical activity of cardiac cells is affected by their surroundings. Current approaches have focused on studying cardiac cells in vitro and using computational models to elucidate the mechanisms behind experimental findings. However, tissue culture techniques are limited to working with neonatal, rather than adult, cells, and computational modeling of these cells has proven challenging. In this work, we have a developed a new approach for conducting paired experimental and computational studies by using a cell line engineered with the minimum machinery for excitability, and a computational model derived and validated directly from this cell line. In order to create a model that reproduces the diversity, rather than simply the average behavior, of experimental studies, we have incorporated a simple yet novel method of inherent variability, and explored what types of experimental variation must be incorporated into the model to recapitulate experimental findings. Using this new platform for paired experimental-computational studies with inherent variability, we will be able to study and better understand how changes in cardiac structure such as fibrosis and heterogeneity lead to conduction slowing, conduction failure, and arrhythmogenesis.
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Zivanovic-Posilovic G, Balenovic D, Barisic I, Strinic D, Stambolija V, Udovicic M, Uzun S, Drmic D, Vlainic J, Bencic ML, Sindic A, Seiwerth S, Sikiric P. Stable gastric pentadecapeptide BPC 157 and bupivacaine. Eur J Pharmacol 2016; 793:56-65. [PMID: 27815173 DOI: 10.1016/j.ejphar.2016.10.035] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 10/24/2016] [Accepted: 10/26/2016] [Indexed: 12/13/2022]
Abstract
Bupivacaine toxicity following accidental overdose still lacks therapeutic solution. However, there are major arguments for testing BPC 157 against bupivacaine toxicity in vivo in rats, in particular, and then finally, in vitro. These are: the lack of any known BPC 157 toxicity, a lifesaving effect via the mitigation of arrhythmias in rats underwent hyperkalemia or digitalis toxicity, the elimination of hyperkalemia and arrhythmias in rats underwent succinylcholine toxicity and finally, the reduction of potassium-induced depolarization in vitro (in HEK293 cells) in severe hyperkalemia. Most importantly, BPC 157 successfully prevents and counteracts bupivacaine cardiotoxicity; BPC 157 is effective even against the worst outcomes such as a severely prolonged QRS complex. Here, rats injected with bupivacaine (100mg/kg IP) exhibited bradycardia, AV-block, ventricular ectopies, ventricular tachycardia, T-wave elevation and asystole. All of the fatalities had developed T-wave elevation, high-degree AV-block, respiratory arrest and asystole. These were largely counteracted by BPC 157 administration (50µg/kg, 10µg/kg, 10ng/kg, or 10pg/kg IP) given 30min before or 1min after the bupivacaine injection. When BPC 157 was given 6min after bupivacaine administration, and after the development of prolonged QRS intervals (20ms), the fatal outcome was markedly postponed. Additionally, the effect of bupivacaine on cell membrane depolarization was explored by measuring membrane voltages (Vm) in HEK293 cells. Bupivacaine (1mM) alone caused depolarization of the cells, while in combination with BPC 157 (1µm), the bupivacaine-induced depolarization was inhibited. Together, these findings suggest that the stable gastric pentadecapeptide BPC 157 should be a potential antidote for bupivacaine cardiotoxicity.
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Affiliation(s)
| | - Diana Balenovic
- Department of Internal Medicine, County Hospital "Dr. Ivo Pedisic", Sisak, Croatia
| | - Ivan Barisic
- Department of Internal Medicine, County Hospital "Pozega", Pozega, Croatia
| | - Dean Strinic
- Department of Internal Medicine, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Vasilije Stambolija
- Department of Anesthesiology and Resuscitation, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Mario Udovicic
- Department of Internal Medicine, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Sandra Uzun
- Department of Anesthesiology and Resuscitation, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Domagoj Drmic
- Department of Pharmacology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Josipa Vlainic
- Laboratory of Molecular Neuropharmacology, Division of Molecular Medicine, Rudjer Boskovic Institute, Zagreb, Croatia
| | - Martina Lovric Bencic
- Department of Internal Medicine, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Aleksandra Sindic
- Department of Physiology and Immunology, Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Sven Seiwerth
- Department of Pathology, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Predrag Sikiric
- Department of Pharmacology, School of Medicine, University of Zagreb, Zagreb, Croatia.
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23
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Ooi A, Wong A, Esau L, Lemtiri-Chlieh F, Gehring C. A Guide to Transient Expression of Membrane Proteins in HEK-293 Cells for Functional Characterization. Front Physiol 2016; 7:300. [PMID: 27486406 PMCID: PMC4949579 DOI: 10.3389/fphys.2016.00300] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/28/2016] [Indexed: 01/17/2023] Open
Abstract
The human embryonic kidney 293 (HEK-293) cells are commonly used as host for the heterologous expression of membrane proteins not least because they have a high transfection efficiency and faithfully translate and process proteins. In addition, their cell size, morphology and division rate, and low expression of native channels are traits that are particularly attractive for current-voltage measurements. Nevertheless, the heterologous expression of complex membrane proteins such as receptors and ion channels for biological characterization and in particular for single-cell applications such as electrophysiology remains a challenge. Expression of functional proteins depends largely on careful step-by-step optimization that includes the design of expression vectors with suitable identification tags, as well as the selection of transfection methods and detection parameters appropriate for the application. Here, we use the heterologous expression of a plant potassium channel, the Arabidopsis thaliana guard cell outward-rectifying K(+) channel, AtGORK (At5G37500) in HEK-293 cells as an example, to evaluate commonly used transfection reagents and fluorescent detection methods, and provide a detailed methodology for optimized transient transfection and expression of membrane proteins for in vivo studies in general and for single-cell applications in particular. This optimized protocol will facilitate the physiological and cellular characterization of complex membrane proteins.
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Affiliation(s)
- Amanda Ooi
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology Thuwal, Saudi Arabia
| | - Aloysius Wong
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and TechnologyThuwal, Saudi Arabia; Institute of Integrative Biology of the Cell, Centre National de la Recherche Scientifique, Le Commissariat à l'Energie Atomique et aux Energies Alternatives, Paris-Sud UniversityGif-Sur-Yvette, France
| | - Luke Esau
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology Thuwal, Saudi Arabia
| | - Fouad Lemtiri-Chlieh
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology Thuwal, Saudi Arabia
| | - Chris Gehring
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology Thuwal, Saudi Arabia
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Abstract
Many high-throughput ion channel assays require the use of voltage-sensitive dyes to detect channel activity in the presence of test compounds. Dye systems employing Förster resonance energy transfer (FRET) between 2 membrane-bound dyes are advantageous in combining high sensitivity, relatively fast response, and ratiometric output. The most widely used FRET voltage dye system employs a coumarin fluorescence donor whose excitation spectrum is pH dependent. The authors have validated a new class of voltage-sensitive FRET donors based on a pyrene moiety. These dyes are significantly brighter than CC2-DMPE and are not pH sensitive in the physiological range. With the new dye system, the authors demonstrate a new high-throughput assay for the acid-sensing ion channel (ASIC) family. They also introduce a novel method for absolute calibration of voltage-sensitive dyes, simultaneously determining the resting membrane potential of a cell. ( Journal of Biomolecular Screening 2007:656-667)
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Affiliation(s)
- Michael P Maher
- Johnson & Johnson Pharmaceutical Research and Development L.L.C., San Diego, California 92121, USA.
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25
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Naughton JR, Connolly T, Varela JA, Lundberg J, Burns MJ, Chiles TC, Christianson JP, Naughton MJ. Shielded Coaxial Optrode Arrays for Neurophysiology. Front Neurosci 2016; 10:252. [PMID: 27375415 PMCID: PMC4899445 DOI: 10.3389/fnins.2016.00252] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 05/21/2016] [Indexed: 11/13/2022] Open
Abstract
Recent progress in the study of the brain has been greatly facilitated by the development of new tools capable of minimally-invasive, robust coupling to neuronal assemblies. Two prominent examples are the microelectrode array (MEA), which enables electrical signals from large numbers of neurons to be detected and spatiotemporally correlated, and optogenetics, which enables the electrical activity of cells to be controlled with light. In the former case, high spatial density is desirable but, as electrode arrays evolve toward higher density and thus smaller pitch, electrical crosstalk increases. In the latter, finer control over light input is desirable, to enable improved studies of neuroelectronic pathways emanating from specific cell stimulation. Here, we introduce a coaxial electrode architecture that is uniquely suited to address these issues, as it can simultaneously be utilized as an optical waveguide and a shielded electrode in dense arrays. Using optogenetically-transfected cells on a coaxial MEA, we demonstrate the utility of the architecture by recording cellular currents evoked from optical stimulation. We also show the capability for network recording by radiating an area of seven individually-addressed coaxial electrode regions with cultured cells covering a section of the extent.
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Affiliation(s)
| | | | - Juan A. Varela
- Department of Psychology, Boston CollegeChestnut Hill, MA, USA
| | - Jaclyn Lundberg
- Department of Psychology, Boston CollegeChestnut Hill, MA, USA
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26
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Feyen P, Colombo E, Endeman D, Nova M, Laudato L, Martino N, Antognazza MR, Lanzani G, Benfenati F, Ghezzi D. Light-evoked hyperpolarization and silencing of neurons by conjugated polymers. Sci Rep 2016; 6:22718. [PMID: 26940513 PMCID: PMC4778138 DOI: 10.1038/srep22718] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 02/18/2016] [Indexed: 11/29/2022] Open
Abstract
The ability to control and modulate the action potential firing in neurons represents a powerful tool for neuroscience research and clinical applications. While neuronal excitation has been achieved with many tools, including electrical and optical stimulation, hyperpolarization and neuronal inhibition are typically obtained through patch-clamp or optogenetic manipulations. Here we report the use of conjugated polymer films interfaced with neurons for inducing a light-mediated inhibition of their electrical activity. We show that prolonged illumination of the interface triggers a sustained hyperpolarization of the neuronal membrane that significantly reduces both spontaneous and evoked action potential firing. We demonstrate that the polymeric interface can be activated by either visible or infrared light and is capable of modulating neuronal activity in brain slices and explanted retinas. These findings prove the ability of conjugated polymers to tune neuronal firing and suggest their potential application for the in-vivo modulation of neuronal activity.
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Affiliation(s)
- Paul Feyen
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Elisabetta Colombo
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
| | - Duco Endeman
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Mattia Nova
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Lucia Laudato
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
| | - Nicola Martino
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Maria Rosa Antognazza
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
| | - Guglielmo Lanzani
- Center for Nano Science and Technology, Istituto Italiano di Tecnologia, Via Pascoli 70/3, 20133 Milano, Italy
- Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
- Department of Experimental Medicine, University of Genova, Viale Benedetto XV 3, 16132 Genova, Italy
| | - Diego Ghezzi
- Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
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27
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Spear JM, Koborssy DA, Schwartz AB, Johnson AJ, Audhya A, Fadool DA, Stagg SM. Kv1.3 contains an alternative C-terminal ER exit motif and is recruited into COPII vesicles by Sec24a. BMC BIOCHEMISTRY 2015; 16:16. [PMID: 26156069 PMCID: PMC4497498 DOI: 10.1186/s12858-015-0045-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 06/26/2015] [Indexed: 12/11/2022]
Abstract
Background Potassium channels play a fundamental role in resetting the resting membrane potential of excitable cells. Determining the intracellular trafficking and localization mechanisms of potassium channels provides a platform to fully characterize their maturation and functionality. Previous investigations have discovered residues or motifs that exist in their primary structure, which directly promote anterograde trafficking of nascent potassium channels. Recently, a non-conical di-acidic motif (E483/484) has been discovered in the C-terminus of the mammalian homologue of the Shaker voltage-gated potassium channel subfamily member 3 (Kv1.3), and was shown to disrupt the anterograde trafficking of Kv1.3. Results We have further investigated the intracellular trafficking requirements of Kv1.3 both in vivo and in vitro. First, three alternative C-terminal acidic residues, E443, E445, E447 were probed for their involvement within the early secretory pathway of Kv1.3. Single point (E443A, E445A, and E447A) and double point (E443A-E445A, E445A-E447A) mutations exhibited no significant changes in their endoplasmic reticulum (ER) retention. The triple point mutant E443A-E445A-E447A displayed a modest ER retention while deletion of the C-terminus showed dramatic ER retention. Second, we demonstrate in vivo the requirement for the Sec24a isoform to confer anterograde trafficking using a siRNA knockdown assay. Third, we show in vitro the association of recombinantly expressed Kv1.3 and Sec24a proteins. Conclusion These results expand upon previous studies aimed at deciphering the Kv1.3 secretory trafficking mechanisms and further show in vitro evidence of the association between Kv1.3 and the COPII cargo adaptor subunit isoform Sec24a. Electronic supplementary material The online version of this article (doi:10.1186/s12858-015-0045-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- John M Spear
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
| | - Dolly Al Koborssy
- Program in Neuroscience, Florida State University, 1107 West Call Street, Tallahassee, FL, 32306, USA.
| | - Austin B Schwartz
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
| | - Adam J Johnson
- Biomolecular Chemistry, University of Wisconsin-Madison, 440 Henry Mall, Madison, WI, 53706, USA.
| | - Anjon Audhya
- Biomolecular Chemistry, University of Wisconsin-Madison, 440 Henry Mall, Madison, WI, 53706, USA.
| | - Debra A Fadool
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA. .,Program in Neuroscience, Florida State University, 1107 West Call Street, Tallahassee, FL, 32306, USA. .,Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL, 32306, USA.
| | - Scott M Stagg
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA. .,Department of Chemistry and Biochemistry, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
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28
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MacKenzie G, Franks NP, Brickley SG. Two-pore domain potassium channels enable action potential generation in the absence of voltage-gated potassium channels. Pflugers Arch 2014; 467:989-99. [PMID: 25482670 PMCID: PMC4428809 DOI: 10.1007/s00424-014-1660-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 11/13/2014] [Accepted: 11/21/2014] [Indexed: 12/18/2022]
Abstract
In this study, we explored the possibility that two-pore domain potassium (K2P) channels are sufficient to support action potential (AP) generation in the absence of conventional voltage-gated potassium (KV) channels. Hodgkin-Huxley parameters were used to mimic the presence of voltage-gated sodium (NaV) channels in HEK-293 cells. Recombinant expression of either TREK-1 or TASK-3 channels was then used to generate a hyperpolarised resting membrane potential (RMP) leading to the characteristic non-linear current-voltage relationship expected of a K2P-mediated conductance. During conductance simulation experiments, both TASK-3 and TREK-1 channels were able to repolarise the membrane once AP threshold was reached, and at physiologically relevant current densities, this K2P-mediated conductance supported sustained AP firing. Moreover, the magnitude of the conductance correlated with the speed of the AP rise in a manner predicted from our computational studies. We discuss the physiological impact of axonal K2P channels and speculate on the possible clinical relevance of K2P channel modulation when considering the actions of general and local anaesthetics.
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Affiliation(s)
- Georgina MacKenzie
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA, 02111, USA
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29
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Liu YQ, Huang WX, Sanchez RM, Min JW, Hu JJ, He XH, Peng BW. Regulation of Kv4.2 A-Type Potassium Channels in HEK-293 Cells by Hypoxia. Front Cell Neurosci 2014; 8:329. [PMID: 25352783 PMCID: PMC4196569 DOI: 10.3389/fncel.2014.00329] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 09/29/2014] [Indexed: 11/13/2022] Open
Abstract
We previously observed that A-type potassium currents were decreased and membrane excitability increased in hippocampal dentate granule cells after neonatal global hypoxia associated with seizures. Here, we studied the effects of hypoxia on the function and expression of Kv4.2 and Kv4.3 α subunit channels, which encode rapidly inactivating A-type K currents, in transfected HEK-293 cells to determine if hypoxia alone could regulate IAin vitro. Global hypoxia in neonatal rat pups resulted in early decreased hippocampal expression of Kv4.2 mRNA and protein with 6 or 12 h post-hypoxia. Whole-cell voltage-clamp recordings revealed that similar times after hypoxia (1%) in vitro decreased peak currents mediated by recombinant Kv4.2 but not Kv4.3 channels. Hypoxia had no significant effect on the voltage-dependencies of activation and inactivation of Kv4.2 channels, but increased the time constant of activation. The same result was observed when Kv4.2 and Kv4.3 channels were co-expressed in a 1:1 ratio. These data suggested that hypoxia directly modulates A-type potassium channels of the subfamily typically expressed in principal hippocampal neurons, and does so in a manner to decrease function. Given the role of IA to slow action potential firing, these data are consistent with a direct effect of hypoxia to decrease IA as a mechanism of increased neuronal excitability and promotion of seizures.
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Affiliation(s)
- Yu-Qiang Liu
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
| | - Wen-Xian Huang
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
| | - Russell M Sanchez
- Department of Surgery, College of Medicine, Texas A&M Health Science Center, Neuroscience Institute, Scott and White Hospital, Central Texas Veterans Health Care System , Temple, TX , USA
| | - Jia-Wei Min
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
| | - Jiang-Jian Hu
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
| | - Xiao-Hua He
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
| | - Bi-Wen Peng
- Department of Physiology, Hubei Provincial Key Laboratory of Developmentally Originated Disorder, School of Basic Medical Sciences, Wuhan University , Wuhan , China
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Yamada H, Haraguchi D, Yasunaga K. Fabrication and Characterization of a K+-Selective Nanoelectrode and Simultaneous Imaging of Topography and Local K+ Flux Using Scanning Electrochemical Microscopy. Anal Chem 2014; 86:8547-52. [DOI: 10.1021/ac502444y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hiroshi Yamada
- Department of Applied Chemistry, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan
| | - Daiki Haraguchi
- Department of Applied Chemistry, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan
| | - Kenji Yasunaga
- Department of Applied Chemistry, National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan
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31
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Boone AN, Senatore A, Chemin J, Monteil A, Spafford JD. Gd3+ and calcium sensitive, sodium leak currents are features of weak membrane-glass seals in patch clamp recordings. PLoS One 2014; 9:e98808. [PMID: 24945283 PMCID: PMC4063719 DOI: 10.1371/journal.pone.0098808] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Accepted: 05/07/2014] [Indexed: 01/13/2023] Open
Abstract
The properties of leaky patch currents in whole cell recording of HEK-293T cells were examined as a means to separate these control currents from expressed sodium and calcium leak channel currents from snail NALCN leak channels possessing both sodium (EKEE) and calcium (EEEE) selectivity filters. Leak currents were generated by the weakening of gigaohm patch seals by artificial membrane rupture using the ZAP function on the patch clamp amplifier. Surprisingly, we found that leak currents generated from the weakened membrane/glass seal can be surprisingly stable and exhibit behavior that is consistent with a sodium leak current derived from an expressible channel. Leaky patch currents differing by 10 fold in size were similarly reduced in size when external sodium ions were replaced with the large monovalent ion NMDG+. Leaky patch currents increased when external Ca2+ (1.2 mM) was lowered to 0.1 mM and were inhibited (>40% to >90%) with 10 µM Gd3+, 100 µM La3+, 1 mM Co2+ or 1 mM Cd2+. Leaky patch currents were relatively insensitive (<30%) to 1 mM Ni2+ and exhibited a variable amount of block with 1 mM verapamil and were insensitive to 100 µM mibefradil or 100 µM nifedipine. We hypothesize that the rapid changes in leak current size in response to changing external cations or drugs relates to their influences on the membrane seal adherence and the electro-osmotic flow of mobile cations channeling in crevices of a particular pore size in the interface between the negatively charged patch electrode and the lipid membrane. Observed sodium leak conductance currents in weak patch seals are reproducible between the electrode glass interface with cell membranes, artificial lipid or Sylgard rubber.
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Affiliation(s)
| | | | - Jean Chemin
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, INSERM, U661, Universités de Montpellier 1 & 2, UMR-5203, Montpellier, France
| | - Arnaud Monteil
- CNRS, UMR-5203, Institut de Génomique Fonctionnelle, INSERM, U661, Universités de Montpellier 1 & 2, UMR-5203, Montpellier, France
| | - J. David Spafford
- Department of Biology, University of Waterloo, Waterloo, Canada
- * E-mail:
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32
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Bartok A, Toth A, Somodi S, Szanto TG, Hajdu P, Panyi G, Varga Z. Margatoxin is a non-selective inhibitor of human Kv1.3 K+ channels. Toxicon 2014; 87:6-16. [PMID: 24878374 DOI: 10.1016/j.toxicon.2014.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/07/2014] [Accepted: 05/12/2014] [Indexed: 11/28/2022]
Abstract
Margatoxin (MgTx), an alpha-KTx scorpion toxin, is considered a selective inhibitor of the Kv1.3K + channel. This peptide is widely used in ion channel research; however, a comprehensive study of its selectivity with electrophysiological methods has not been published yet. The lack of selectivity might lead to undesired side effects upon therapeutic application or may lead to incorrect conclusion regarding the role of a particular ion channel in a physiological or pathophysiological response either in vitro or in vivo. Using the patch-clamp technique we characterized the selectivity profile of MgTx using L929 cells expressing mKv1.1 channels, human peripheral lymphocytes expressing Kv1.3 channels and transiently transfected tsA201 cells expressing hKv1.1, hKv1.2, hKv1.3, hKv1.4-IR, hKv1.5, hKv1.6, hKv1.7, rKv2.1, Shaker-IR, hERG, hKCa1.1, hKCa3.1 and hNav1.5 channels. MgTx is indeed a high affinity inhibitor of Kv1.3 (Kd = 11.7 pM) but is not selective, it inhibits the Kv1.2 channel with similar affinity (Kd = 6.4 pM) and Kv1.1 in the nanomolar range (Kd = 4.2 nM). Based on our comprehensive data MgTX has to be considered a non-selective Kv1.3 inhibitor, and thus, experiments aiming at elucidating the significance of Kv1.3 in in vitro or in vivo physiological responses have to be carefully evaluated.
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Affiliation(s)
- Adam Bartok
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Agnes Toth
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Sandor Somodi
- Division of Metabolic Diseases, Department of Internal Medicine, University of Debrecen, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Tibor G Szanto
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Peter Hajdu
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Dentistry, 98 Nagyerdei krt., Debrecen 4032, Hungary.
| | - Gyorgy Panyi
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary; MTA-DE Cell Biology and Signaling Research Group, 4032 Debrecen, Egyetem tér 1, Hungary. http://biophys.med.unideb.hu/en/node/311
| | - Zoltan Varga
- Department of Biophysics and Cell Biology, University of Debrecen, Faculty of Medicine, 98 Nagyerdei krt., Debrecen 4032, Hungary.
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Mercer RCC, Ma L, Watts JC, Strome R, Wohlgemuth S, Yang J, Cashman NR, Coulthart MB, Schmitt-Ulms G, Jhamandas JH, Westaway D. The prion protein modulates A-type K+ currents mediated by Kv4.2 complexes through dipeptidyl aminopeptidase-like protein 6. J Biol Chem 2013; 288:37241-55. [PMID: 24225951 DOI: 10.1074/jbc.m113.488650] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Widely expressed in the adult central nervous system, the cellular prion protein (PrP(C)) is implicated in a variety of processes, including neuronal excitability. Dipeptidyl aminopeptidase-like protein 6 (DPP6) was first identified as a PrP(C) interactor using in vivo formaldehyde cross-linking of wild type (WT) mouse brain. This finding was confirmed in three cell lines and, because DPP6 directs the functional assembly of K(+) channels, we assessed the impact of WT and mutant PrP(C) upon Kv4.2-based cell surface macromolecular complexes. Whereas a Gerstmann-Sträussler-Scheinker disease version of PrP with eight extra octarepeats was a loss of function both for complex formation and for modulation of Kv4.2 channels, WT PrP(C), in a DPP6-dependent manner, modulated Kv4.2 channel properties, causing an increase in peak amplitude, a rightward shift of the voltage-dependent steady-state inactivation curve, a slower inactivation, and a faster recovery from steady-state inactivation. Thus, the net impact of wt PrP(C) was one of enhancement, which plays a critical role in the down-regulation of neuronal membrane excitability and is associated with a decreased susceptibility to seizures. Insofar as previous work has established a requirement for WT PrP(C) in the Aβ-dependent modulation of excitability in cholinergic basal forebrain neurons, our findings implicate PrP(C) regulation of Kv4.2 channels as a mechanism contributing to the effects of oligomeric Aβ upon neuronal excitability and viability.
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Biochemical, single-channel, whole-cell patch clamp, and pharmacological analyses of endogenous TRPM4 channels in HEK293 cells. Neurosci Lett 2013; 541:105-10. [DOI: 10.1016/j.neulet.2013.02.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2012] [Revised: 12/15/2012] [Accepted: 02/03/2013] [Indexed: 01/24/2023]
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Mourot A, Fehrentz T, Kramer RH. Photochromic potassium channel blockers: design and electrophysiological characterization. Methods Mol Biol 2013; 995:89-105. [PMID: 23494374 DOI: 10.1007/978-1-62703-345-9_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Voltage-gated potassium (K v) channels are membrane proteins that open a selective pore upon membrane depolarization, allowing K(+) ions to flow down their electrochemical gradient. In neurons, K v channels play a key role in repolarizing the membrane potential during the falling phase of the action potential, often resulting in an after hyperpolarization. Opening of K v channels results in a decrease of cellular excitability, whereas closing (or pharmacological block) has the opposite effect, increased excitability. We have developed a series of photosensitive blockers for K v channels that enable reversible, optical regulation of potassium ion flow. Such molecules can be used for remote control of neuronal excitability using light as an on/off switch. Here we describe the design and electrophysiological characterization of photochromic blockers of ion channels. Our focus is on K v channels but in principle, the techniques described here can be applied to other ion channels and signaling proteins.
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Affiliation(s)
- Alexandre Mourot
- Department of Molecular and Cellular Biology, University of California Berkeley, Berkeley, CA, USA.
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36
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Zhang XF, Zhang D, Surowy CS, Yao B, Jarvis MF, McGaraughty S, Neelands TR. Development and validation of a medium-throughput electrophysiological assay for KCNQ2/3 channel openers using QPatch HT. Assay Drug Dev Technol 2012; 11:17-24. [PMID: 23002961 DOI: 10.1089/adt.2012.446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The KCNQ2/3 channel has emerged as a drug target for a number of neurological disorders including pain and epilepsy. Known KCNQ2/3 openers have effects on two distinct biophysical properties of the channel: (1) a hyperpolarizing shift in the voltage dependence of channel activation (V(1/2)), and (2) an increase in channel open probability or peak whole-cell current. The current high-throughput screening assays for KCNQ2/3 openers measure changes of channel activity at sub-peak conductances and the output measure is a combination of effects on V(1/2) shift and peak current. Here, we describe a medium-throughput electrophysiological assay for screening KCNQ2/3 openers using the QPatch HT platform. We employed a double-pulse protocol that measures the shift in V(1/2) and the change in current amplitude at peak conductance voltage. Retigabine along with novel KCNQ2/3 openers were evaluated in this assay. Three classes of KCNQ2/3 openers were identified based on the hyperpolarizing shift in V(1/2) and the change in peak current. All three classes of compounds caused a hyperpolarizing shift in V(1/2), but they were differentiated by their respective effects on peak current amplitude (increase, decrease, or only modestly affecting peak current amplitude). KCNQ2/3 blockers were also identified with this assay. These compounds blocked currents without affecting voltage-dependent activation. In summary, we have developed a medium-throughput assay that can reliably detect changes in the biophysical properties of the KCNQ2/3 channel, V(1/2), and peak current amplitude, and therefore may serve as a reliable assay to evaluate KCNQ2/3 openers and blockers.
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Affiliation(s)
- Xu-Feng Zhang
- Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064-6125, USA.
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37
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Kanda VA, Abbott GW. KCNE Regulation of K(+) Channel Trafficking - a Sisyphean Task? Front Physiol 2012; 3:231. [PMID: 22754540 PMCID: PMC3385356 DOI: 10.3389/fphys.2012.00231] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 06/08/2012] [Indexed: 11/16/2022] Open
Abstract
Voltage-gated potassium (Kv) channels shape the action potentials of excitable cells and regulate membrane potential and ion homeostasis in excitable and non-excitable cells. With 40 known members in the human genome and a variety of homomeric and heteromeric pore-forming α subunit interactions, post-translational modifications, cellular locations, and expression patterns, the functional repertoire of the Kv α subunit family is monumental. This versatility is amplified by a host of interacting proteins, including the single membrane-spanning KCNE ancillary subunits. Here, examining both the secretory and the endocytic pathways, we review recent findings illustrating the surprising virtuosity of the KCNE proteins in orchestrating not just the function, but also the composition, diaspora and retrieval of channels formed by their Kv α subunit partners.
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Affiliation(s)
- Vikram A Kanda
- Department of Biology, Manhattan College Riverdale, New York, NY, USA
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38
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Wen H, Östman J, Bubb KJ, Panayiotou C, Priestley JV, Baker MD, Ahluwalia A. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a novel activator of transient receptor potential vanilloid 1 (TRPV1) channel. J Biol Chem 2012; 287:13868-76. [PMID: 22389490 PMCID: PMC3340178 DOI: 10.1074/jbc.m111.334896] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TRPV1 is a member of the transient receptor potential ion channel family and is gated by capsaicin, the pungent component of chili pepper. It is expressed predominantly in small diameter peripheral nerve fibers and is activated by noxious temperatures >42 °C. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a cytochrome P-450 4A/4F-derived metabolite of the membrane phospholipid arachidonic acid. It is a powerful vasoconstrictor and has structural similarities with other TRPV1 agonists, e.g. the hydroperoxyeicosatetraenoic acid 12-HPETE, and we hypothesized that it may be an endogenous ligand for TRPV1 in sensory neurons innervating the vasculature. Here, we demonstrate that 20-HETE both activates and sensitizes mouse and human TRPV1, in a kinase-dependent manner, involving the residue Ser(502) in heterologously expressed hTRPV1, at physiologically relevant concentrations.
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Affiliation(s)
- Hairuo Wen
- William Harvey Research Institute, Barts and the London Medical School, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, United Kingdom
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Chen CY, Wo AM, Jong DS. A microfluidic concentration generator for dose-response assays on ion channel pharmacology. LAB ON A CHIP 2012; 12:794-801. [PMID: 22222413 DOI: 10.1039/c1lc20548j] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We present a microfluidic device to generate either statically spatial or dynamically temporal logarithmic concentrations. The temporal logarithmic concentration generator was also integrated with planar patch-clamp chips for dose-response assays on ion channels. Proposed serial dilution principle controls the flow pattern at each branching point via designing the flow resistance of microchannels. Simple and linear ratios of the flow resistance results in desired logarithmic concentration at outlets, where the concentrations can be dynamically altered by different combination of valve actuations, were demonstrated. Single-cell pharmacology on ion channels was implemented by sequentially applying logarithmic drug concentrations to patched cells. Inhibitory activity of potassium channels of human embryonic kidney cells was examined by tetraethylammonium solutions. Resulted IC(50) and Hill slope reveal excellent agreement with assays from manually prepared drug concentrations showing the practicability and preciseness of the present approach. Applications include cellular analysis under various drugs and/or logarithmic concentrations at the single-cell level.
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Affiliation(s)
- Chang-Yu Chen
- Institute of Applied Mechanics, National Taiwan University, Taipei 106, Taiwan
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40
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Doczi MA, Damon DH, Morielli AD. A C-terminal PDZ binding domain modulates the function and localization of Kv1.3 channels. Exp Cell Res 2011; 317:2333-41. [PMID: 21726550 DOI: 10.1016/j.yexcr.2011.06.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/07/2011] [Accepted: 06/20/2011] [Indexed: 01/12/2023]
Abstract
The voltage-gated potassium channel, Kv1.3, plays an important role in regulating membrane excitability in diverse cell types ranging from T-lymphocytes to neurons. In the present study, we test the hypothesis that the C-terminal PDZ binding domain modulates the function and localization of Kv1.3. We created a mutant form of Kv1.3 that lacked the last three amino acids of the C-terminal PDZ-binding domain (Kv1.3ΔTDV). This form of Kv1.3 did not bind the PDZ domain containing protein, PSD95. We transfected wild type and mutant Kv1.3 into HEK293 cells and determined if the mutation affected current, Golgi localization, and surface expression of the channel. We found that cells transfected with Kv1.3ΔTDV had greater current and lower Golgi localization than those transfected with Kv1.3. Truncation of the C-terminal PDZ domain did not affect surface expression of Kv1.3. These findings suggest that PDZ-dependent interactions affect both Kv1.3 localization and function. The finding that current and Golgi localization changed without a corresponding change in surface expression suggests that PDZ interactions affect localization and function via independent mechanisms.
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Affiliation(s)
- Megan A Doczi
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05401, USA
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41
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Peigneur S, Billen B, Derua R, Waelkens E, Debaveye S, Béress L, Tytgat J. A bifunctional sea anemone peptide with Kunitz type protease and potassium channel inhibiting properties. Biochem Pharmacol 2011; 82:81-90. [PMID: 21477583 DOI: 10.1016/j.bcp.2011.03.023] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 03/24/2011] [Accepted: 03/25/2011] [Indexed: 12/17/2022]
Abstract
Sea anemone venom is a known source of interesting bioactive compounds, including peptide toxins which are invaluable tools for studying structure and function of voltage-gated potassium channels. APEKTx1 is a novel peptide isolated from the sea anemone Anthopleura elegantissima, containing 63 amino acids cross-linked by 3 disulfide bridges. Sequence alignment reveals that APEKTx1 is a new member of the type 2 sea anemone peptides targeting voltage-gated potassium channels (K(V)s), which also include the kalicludines from Anemonia sulcata. Similar to the kalicludines, APEKTx1 shares structural homology with both the basic pancreatic trypsin inhibitor (BPTI), a very potent Kunitz-type protease inhibitor, and dendrotoxins which are powerful blockers of voltage-gated potassium channels. In this study, APEKTx1 has been subjected to a screening on a wide range of 23 ion channels expressed in Xenopus laevis oocytes: 13 cloned voltage-gated potassium channels (K(V)1.1-K(V)1.6, K(V)1.1 triple mutant, K(V)2.1, K(V)3.1, K(V)4.2, K(V)4.3, hERG, the insect channel Shaker IR), 2 cloned hyperpolarization-activated cyclic nucleotide-sensitive cation non-selective channels (HCN1 and HCN2) and 8 cloned voltage-gated sodium channels (Na(V)1.2-Na(V)1.8 and the insect channel DmNa(V)1). Our data show that APEKTx1 selectively blocks K(V)1.1 channels in a very potent manner with an IC(50) value of 0.9nM. Furthermore, we compared the trypsin inhibitory activity of this toxin with BPTI. APEKTx1 inhibits trypsin with a dissociation constant of 124nM. In conclusion, this study demonstrates that APEKTx1 has the unique feature to combine the dual functionality of a potent and selective blocker of K(V)1.1 channels with that of a competitive inhibitor of trypsin.
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Affiliation(s)
- Steve Peigneur
- Laboratory of Toxicology, University of Leuven (K.U. Leuven), Campus Gasthuisberg O&N2, Herestraat, Belgium.
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42
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Nörenberg W, Hempel C, Urban N, Sobottka H, Illes P, Schaefer M. Clemastine potentiates the human P2X7 receptor by sensitizing it to lower ATP concentrations. J Biol Chem 2011; 286:11067-81. [PMID: 21262970 PMCID: PMC3064161 DOI: 10.1074/jbc.m110.198879] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 01/10/2011] [Indexed: 01/08/2023] Open
Abstract
P2X7 receptors have emerged as potential drug targets for the treatment of medical conditions such as e.g. rheumatoid arthritis and neuropathic pain. To assess the impact of pharmaceuticals on P2X7, we screened a compound library comprising approved or clinically tested drugs and identified several compounds that augment the ATP-triggered P2X7 activity in a stably transfected HEK293 cell line. Of these, clemastine markedly sensitized Ca(2+) entry through P2X7 to lower ATP concentrations. Extracellularly but not intracellularly applied clemastine rapidly and reversibly augmented P2X7-mediated whole-cell currents evoked by non-saturating ATP concentrations. Clemastine also accelerated the ATP-induced pore formation and Yo-Pro-1 uptake, increased the fractional NMDG(+) permeability, and stabilized the open channel conformation of P2X7. Thus, clemastine is an extracellularly binding allosteric modulator of P2X7 that sensitizes P2X7 to lower ATP concentrations and facilitates its pore dilation. The activity of clemastine on native P2X7 receptors, Ca(2+) entry, and whole-cell currents was confirmed in human monocyte-derived macrophages. Similar effects were observed in murine bone marrow-derived macrophages. Consistent with the data on recombinant P2X7, clemastine augmented the ATP-induced cation entry and Yo-Pro-1 uptake. In accordance with the observation that P2X7 controls the cytokine release from LPS-primed macrophages, we found that clemastine augmented the IL-1β release from LPS-primed human macrophages. Collectively, these data point to a sensitization of the recombinantly or natively expressed human P2X7 receptor toward its physiological activator, ATP, possibly leading to a modulation of macrophage-dependent immune responses.
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Affiliation(s)
- Wolfgang Nörenberg
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Christoph Hempel
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Nicole Urban
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Helga Sobottka
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Peter Illes
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
| | - Michael Schaefer
- From the Rudolf Boehm Institute of Pharmacology and Toxicology, University of Leipzig, 04107 Leipzig, Germany
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43
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Chen CY, Tu TY, Jong DS, Wo AM. Ion channel electrophysiology via integrated planar patch-clamp chip with on-demand drug exchange. Biotechnol Bioeng 2011; 108:1395-403. [PMID: 21328315 DOI: 10.1002/bit.23068] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 12/29/2010] [Accepted: 01/07/2011] [Indexed: 11/05/2022]
Abstract
Planar patch clamp has revolutionized characterization of ion channel behavior in drug discovery primarily via advancement in high throughput. Lab use of planar technology, however, addresses different requirements and suffers from inflexibility to enable wide range of interrogation via a single cell. This work presents integration of planar patch clamp with microfluidics, achieving multiple solution exchanges for tailor-specific measurement and allowing rapid replacement of the cell-contacting aperture. Studies via endogenously expressed ion channels in HEK 293T cells were commenced to characterize the device. Results reveal the microfluidic concentration generator produces distinct solution/drug combination/concentrations on-demand. Volume-regulated chloride channel and voltage-gated potassium channels in HEK 293T cells immersed in generated solutions under various osmolarities or drug concentrations show unique channel signature under specific condition. Excitation and blockage of ion channels in a single cell was demonstrated via serial solution exchange. Robustness of the reversible bonding and ease of glass substrate replacement were proven via repeated usage of the integrated device. The present approach reveals the capability and flexibility of integrated microfluidic planar patch-clamp system for ion channel assays.
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Affiliation(s)
- Chang-Yu Chen
- Institute of Applied Mechanics, National Taiwan University, 1 Roosevelt Road, Section 4, Taipei 106, Taiwan
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44
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Bhave G, Chauder BA, Liu W, Dawson ES, Kadakia R, Nguyen TT, Lewis LM, Meiler J, Weaver CD, Satlin LM, Lindsley CW, Denton JS. Development of a selective small-molecule inhibitor of Kir1.1, the renal outer medullary potassium channel. Mol Pharmacol 2010; 79:42-50. [PMID: 20926757 DOI: 10.1124/mol.110.066928] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The renal outer medullary potassium (K+) channel, ROMK (Kir1.1), is a putative drug target for a novel class of loop diuretic that would lower blood volume and pressure without causing hypokalemia. However, the lack of selective ROMK inhibitors has hindered efforts to assess its therapeutic potential. In a high-throughput screen for small-molecule modulators of ROMK, we previously identified a potent and moderately selective ROMK antagonist, 7,13-bis(4-nitrobenzyl)-1,4,10-trioxa-7,13-diazacyclopentadecane (VU590), that also inhibits Kir7.1. Because ROMK and Kir7.1 are coexpressed in the nephron, VU590 is not a good probe of ROMK function in the kidney. Here we describe the development of the structurally related inhibitor 2,2'-oxybis(methylene)bis(5-nitro-1H-benzo[d]imidazole) (VU591), which is as potent as VU590 but is selective for ROMK over Kir7.1 and more than 65 other potential off-targets. VU591 seems to block the intracellular pore of the channel. The development of VU591 may enable studies to explore the viability of ROMK as a diuretic target.
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Affiliation(s)
- Gautam Bhave
- Department of Anesthesiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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45
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Tang X, Hang D, Sand A, Kofuji P. Variable loss of Kir4.1 channel function in SeSAME syndrome mutations. Biochem Biophys Res Commun 2010; 399:537-41. [PMID: 20678478 DOI: 10.1016/j.bbrc.2010.07.105] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 07/27/2010] [Indexed: 11/28/2022]
Abstract
SeSAME syndrome is a complex disease characterized by seizures, sensorineural deafness, ataxia, mental retardation and electrolyte imbalance. Mutations in the inwardly rectifying potassium channel Kir4.1 (KCNJ10 gene) have been linked to this condition. Kir4.1 channels are weakly rectifying channels expressed in glia, kidney, cochlea and possibly other tissues. We determined the electrophysiological properties of SeSAME mutant channels after expression in transfected mammalian cells. We found that a majority of mutations (R297C, C140R, R199X, T164I) resulted in complete loss of Kir4.1 channel function while two mutations (R65P and A167V) produced partial loss of function. All mutant channels were rescued upon co-transfection of wild-type Kir4.1 but not Kir5.1 channels. Cell-surface biotinylation assays indicate significant plasma membrane expression of all mutant channels with exception of the non-sense mutant R199X. These results indicate the differential loss of Kir channel function among SeSAME syndrome mutations.
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Affiliation(s)
- Xiaofang Tang
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455,USA
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46
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Milnes JT, Witchel HJ, Leaney JL, Leishman DJ, Hancox JC. Investigating dynamic protocol-dependence of hERG potassium channel inhibition at 37°C: Cisapride versus dofetilide. J Pharmacol Toxicol Methods 2010; 61:178-91. [DOI: 10.1016/j.vascn.2010.02.007] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Revised: 02/03/2010] [Accepted: 02/11/2010] [Indexed: 01/08/2023]
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47
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Human embryonic kidney (HEK293) cells express endogenous voltage-gated sodium currents and Na v 1.7 sodium channels. Neurosci Lett 2009; 469:268-72. [PMID: 20006571 DOI: 10.1016/j.neulet.2009.12.012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 12/04/2009] [Accepted: 12/07/2009] [Indexed: 01/03/2023]
Abstract
Human embryonic kidney (HEK293) cells are widely used for the heterologous expression of voltage- and ligand-gated ion channels. Patch clamp analysis of HEK293 cells in the whole-cell configuration identified voltage-gated, rapidly inactivating inward currents. Peak current amplitudes ranged from less than 100 pA to more than 800 pA, with the majority (84 of 130 cells) in the 100-400 pA range. Transient inward currents were separated into three components on the basis of sensitivity to cadmium and tetrodotoxin (TTX). Application of cadmium (300 microM) reduced current amplitude to 65% of control, consistent with the existence of current carried by a cadmium-sensitive nonspecific cation channel previously identified in HEK293 cells. Application of TTX (500 nM) reduced current amplitude by 47%, consistent with the existence of current carried by a TTX-sensitive voltage-gated sodium channel. Joint application of cadmium and TTX was additive, reducing current amplitude to 28% of control. The residual cadmium- and TTX-resistant currents represent a third pharmacologically distinct component of the rapidly inactivating inward current that was not characterized further. The pyrethroid insecticide tefluthrin (10 microM) prolonged the inactivation of transient currents and induced slowly decaying tail currents, effects that are characteristic of sodium channel modification by pyrethroids. The use of sodium channel isoform-specific primers in polymerase chain reaction amplifications on HEK293 cell first-strand cDNA detected the consistent expression of the human Na(v)1.7 sodium channel isoform in cells that expressed the TTX-sensitive component of current. These results provide evidence for an endogenous TTX-sensitive sodium current in HEK293 cells that is associated primarily with the expression of the Na(v)1.7 sodium channel isoform.
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48
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Chen CY, Tu TY, Chen CH, Jong DS, Wo AM. Patch clamping on plane glass-fabrication of hourglass aperture and high-yield ion channel recording. LAB ON A CHIP 2009; 9:2370-2380. [PMID: 19636469 DOI: 10.1039/b901025d] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Planar patch-clamp has revolutionized ion-channel measurement by eliminating laborious manipulation from the traditional micropipette approach and enabling high throughput. However, low yield in gigaseal formation and/or relatively high cost due to microfabricated processes are two main drawbacks. This paper presents patch clamping on glass substrate-an economical solution without sacrificing gigaseal yield rate. Two-stage CO(2) laser drilling methodology was used to generate an hourglass, funnel-like aperture of a specified diameter with smooth and debris-free surfaces on 150 microm borosilicate cover glass. For 1-3 microm apertures as patch-clamp chips, seal resistance was tested on human embryonic kidney, Chinese hamster ovary, and Jurkat T lymphoma cells with a gigaseal success rate of 62.5%, 43.6% and 66.7% respectively. Results also demonstrated both whole-cell and single channel recording on endogenously expressed ion channels to confirm the capability of different patch configurations.
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Affiliation(s)
- Chang-Yu Chen
- Institute of Applied Mechanics, National Taiwan University, 1 Roosevelt Road, Section 4, Taipei, 106, Taiwan
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49
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Glaudemans B, van der Wijst J, Scola RH, Lorenzoni PJ, Heister A, van der Kemp AW, Knoers NV, Hoenderop JG, Bindels RJ. A missense mutation in the Kv1.1 voltage-gated potassium channel-encoding gene KCNA1 is linked to human autosomal dominant hypomagnesemia. J Clin Invest 2009; 119:936-42. [PMID: 19307729 DOI: 10.1172/jci36948] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Accepted: 01/07/2009] [Indexed: 02/04/2023] Open
Abstract
Primary hypomagnesemia is a heterogeneous group of disorders characterized by renal or intestinal magnesium (Mg2+) wasting, resulting in tetany, cardiac arrhythmias, and seizures. The kidney plays an essential role in maintaining blood Mg2+ levels, with a prominent function for the Mg2+-transporting channel transient receptor potential cation channel, subfamily M, member 6 (TRPM6) in the distal convoluted tubule (DCT). In the DCT, Mg2+ reabsorption is an active transport process primarily driven by the negative potential across the luminal membrane. Here, we studied a family with isolated autosomal dominant hypomagnesemia and used a positional cloning approach to identify an N255D mutation in KCNA1, a gene encoding the voltage-gated potassium (K+) channel Kv1.1. Kv1.1 was found to be expressed in the kidney, where it colocalized with TRPM6 along the luminal membrane of the DCT. Upon overexpression in a human kidney cell line, patch clamp analysis revealed that the KCNA1 N255D mutation resulted in a nonfunctional channel, with a dominant negative effect on wild-type Kv1.1 channel function. These data suggest that Kv1.1 is a renal K+ channel that establishes a favorable luminal membrane potential in DCT cells to control TRPM6-mediated Mg2+ reabsorption.
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Affiliation(s)
- Bob Glaudemans
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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Verkerk AO, Zegers JG, van Ginneken ACG, Wilders R. Dynamic action potential clamp as a powerful tool in the development of a gene-based bio-pacemaker. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:133-6. [PMID: 19162611 DOI: 10.1109/iembs.2008.4649108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The development of a genetically engineered 'biological pacemaker', or 'bio-pacemaker', is a rapidly emerging field of research. One of the approaches in this field is to turn intrinsically quiescent myocardial cells, i.e., atrial or ventricular cells, into pacemaker cells by making them express the cardiac hyperpolarization-activated 'pacemaker current' If (known in neurophysiology as Ih), which is encoded by the hyperpolarization-activated cyclic nucleotide-modulated (HCN) gene family. We carried out 'dynamic action potential clamp' (dAPC) experiments in which we record current from a HEK-293 cell transfected with HCN4, which is the dominant HCN isoform in the sinoatrial (SA) node. This HCN4-transfected HEK-293 cell is voltage-clamped by the action potential generated in a real-time simulation of a human atrial cell (Courtemanche-Ramirez-Nattel model). In a continuous feedback loop, this current is injected into the atrial cell, so that this cell effectively expresses an HCN4-based pacemaker current. With sufficiently high 'expression levels' of HCN4 current the atrial cell is turned into a pacemaker cell with an SA nodal like action potential. Lower expression levels are sufficient if the inward rectifier potassium current (IK1), which is largely responsible for the stable resting potential of atrial cells, is 'down-regulated' by 50%, thus mimicking the gene therapy strategy to create a bio-pacemaker by down-regulation of IK1 and (over-)expression of If. Our dAPC experiments provide direct insights into the effects of introducing HCN4 current into an atrial cell, illustrating that dynamic action potential clamp can be a powerful tool in the process of developing a gene-based bio-pacemaker.
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Affiliation(s)
- Arie O Verkerk
- Department of Physiology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands.
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