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Guo Q, Fu J, Yuan L, Liao Y, Li M, Li X, Yi B, Zhang J, Gao B. Diversity analysis of sea anemone peptide toxins in different tissues of Heteractis crispa based on transcriptomics. Sci Rep 2024; 14:7684. [PMID: 38561372 PMCID: PMC10985097 DOI: 10.1038/s41598-024-58402-2] [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: 11/27/2023] [Accepted: 03/28/2024] [Indexed: 04/04/2024] Open
Abstract
Peptide toxins found in sea anemones venom have diverse properties that make them important research subjects in the fields of pharmacology, neuroscience and biotechnology. This study used high-throughput sequencing technology to systematically analyze the venom components of the tentacles, column, and mesenterial filaments of sea anemone Heteractis crispa, revealing the diversity and complexity of sea anemone toxins in different tissues. A total of 1049 transcripts were identified and categorized into 60 families, of which 91.0% were proteins and 9.0% were peptides. Of those 1049 transcripts, 416, 291, and 307 putative proteins and peptide precursors were identified from tentacles, column, and mesenterial filaments respectively, while 428 were identified when the datasets were combined. Of these putative toxin sequences, 42 were detected in all three tissues, including 33 proteins and 9 peptides, with the majority of peptides being ShKT domain, β-defensin, and Kunitz-type. In addition, this study applied bioinformatics approaches to predict the family classification, 3D structures, and functional annotation of these representative peptides, as well as the evolutionary relationships between peptides, laying the foundation for the next step of peptide pharmacological activity research.
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Affiliation(s)
- Qiqi Guo
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China
| | - Jinxing Fu
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China
| | - Lin Yuan
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China
- Department of Pharmacy, 928th Hospital of PLA Joint Logistics Support Force, Haikou, China
| | - Yanling Liao
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China
| | - Ming Li
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China
| | - Xinzhong Li
- School of Health and Life Sciences, Teesside University, Middlesbrough, UK
| | - Bo Yi
- Department of Pharmacy, 928th Hospital of PLA Joint Logistics Support Force, Haikou, China
| | - Junqing Zhang
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China.
| | - Bingmiao Gao
- Engineering Research Center of Tropical Medicine Innovation and Transformation, Ministry of Education, International Joint Research Center of Human-machine Intelligent Collaborative for Tumor Precision Diagnosis and Treatment of Hainan Province, School of Pharmacy, Hainan Medical University, Haikou, China.
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Primak AL, Orlov NA, Peigneur S, Tytgat J, Ignatova AA, Denisova KR, Yakimov SA, Kirpichnikov MP, Nekrasova OV, Feofanov AV. AgTx2-GFP, Fluorescent Blocker Targeting Pharmacologically Important K v1.x (x = 1, 3, 6) Channels. Toxins (Basel) 2023; 15:toxins15030229. [PMID: 36977120 PMCID: PMC10056440 DOI: 10.3390/toxins15030229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/14/2023] [Accepted: 03/16/2023] [Indexed: 03/30/2023] Open
Abstract
The growing interest in potassium channels as pharmacological targets has stimulated the development of their fluorescent ligands (including genetically encoded peptide toxins fused with fluorescent proteins) for analytical and imaging applications. We report on the properties of agitoxin 2 C-terminally fused with enhanced GFP (AgTx2-GFP) as one of the most active genetically encoded fluorescent ligands of potassium voltage-gated Kv1.x (x = 1, 3, 6) channels. AgTx2-GFP possesses subnanomolar affinities for hybrid KcsA-Kv1.x (x = 3, 6) channels and a low nanomolar affinity to KcsA-Kv1.1 with moderate dependence on pH in the 7.0-8.0 range. Electrophysiological studies on oocytes showed a pore-blocking activity of AgTx2-GFP at low nanomolar concentrations for Kv1.x (x = 1, 3, 6) channels and at micromolar concentrations for Kv1.2. AgTx2-GFP bound to Kv1.3 at the membranes of mammalian cells with a dissociation constant of 3.4 ± 0.8 nM, providing fluorescent imaging of the channel membranous distribution, and this binding depended weakly on the channel state (open or closed). AgTx2-GFP can be used in combination with hybrid KcsA-Kv1.x (x = 1, 3, 6) channels on the membranes of E. coli spheroplasts or with Kv1.3 channels on the membranes of mammalian cells for the search and study of nonlabeled peptide pore blockers, including measurement of their affinity.
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Affiliation(s)
- Alexandra L Primak
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Nikita A Orlov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Steve Peigneur
- Toxicology and Pharmacology, Campus Gasthuisberg O&N2, University of Leuven (KU Leuven), Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Jan Tytgat
- Toxicology and Pharmacology, Campus Gasthuisberg O&N2, University of Leuven (KU Leuven), Herestraat 49, P.O. Box 922, B-3000 Leuven, Belgium
| | - Anastasia A Ignatova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Kristina R Denisova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Sergey A Yakimov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Mikhail P Kirpichnikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
| | - Oksana V Nekrasova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
| | - Alexey V Feofanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, 119234 Moscow, Russia
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He S, Moutaoufik MT, Islam S, Persad A, Wu A, Aly KA, Fonge H, Babu M, Cayabyab FS. HERG channel and cancer: A mechanistic review of carcinogenic processes and therapeutic potential. Biochim Biophys Acta Rev Cancer 2020; 1873:188355. [PMID: 32135169 DOI: 10.1016/j.bbcan.2020.188355] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 02/28/2020] [Accepted: 02/28/2020] [Indexed: 12/21/2022]
Abstract
The human ether-à-go-go related gene (HERG) encodes the alpha subunit of Kv11.1, which is a voltage-gated K+ channel protein mainly expressed in heart and brain tissue. HERG plays critical role in cardiac repolarization, and mutations in HERG can cause long QT syndrome. More recently, evidence has emerged that HERG channels are aberrantly expressed in many kinds of cancer cells and play important roles in cancer progression. HERG could therefore be a potential biomarker for cancer and a possible molecular target for anticancer drug design. HERG affects a number of cellular processes, including cell proliferation, apoptosis, angiogenesis and migration, any of which could be affected by dysregulation of HERG. This review provides an overview of available information on HERG channel as it relates to cancer, with focus on the mechanism by which HERG influences cancer progression. Molecular docking attempts suggest two possible protein-protein interactions of HERG with the ß1-integrin receptor and the transcription factor STAT-1 as novel HERG-directed therapeutic targeting which avoids possible cardiotoxicity. The role of epigenetics in regulating HERG channel expression and activity in cancer will also be discussed. Finally, given its inherent extracellular accessibility as an ion channel, we discuss regulatory roles of this molecule in cancer physiology and therapeutic potential. Future research should be directed to explore the possibilities of therapeutic interventions targeting HERG channels while minding possible complications.
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Affiliation(s)
- Siyi He
- Department of Surgery, Neuroscience Research Group, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | | | - Saadul Islam
- Department of Surgery, Neuroscience Research Group, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Amit Persad
- Department of Surgery, Neuroscience Research Group, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Adam Wu
- Department of Surgery, Neuroscience Research Group, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Khaled A Aly
- Department of Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Humphrey Fonge
- Department of Medical Imaging, University of Saskatchewan, Saskatoon, Saskatchewan S7N 0W8, Canada; Department of Medical Imaging, Royal University Hospital, Saskatoon, Saskatchewan S7N 0W8, Canada
| | - Mohan Babu
- Department of Biochemistry, University of Regina, Regina, SK S4S 0A2, Canada
| | - Francisco S Cayabyab
- Department of Surgery, Neuroscience Research Group, College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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Cnidarian peptide neurotoxins: a new source of various ion channel modulators or blockers against central nervous systems disease. Drug Discov Today 2018; 24:189-197. [PMID: 30165198 DOI: 10.1016/j.drudis.2018.08.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/13/2018] [Accepted: 08/10/2018] [Indexed: 01/17/2023]
Abstract
Cnidaria provide the largest source of bioactive peptides for new drug development. The venoms contain enzymes, potent pore-forming toxins and neurotoxins. The neurotoxins can immobilize predators rapidly when discharged via modifying sodium-channel-gating or blocking the potassium channel during the repolarization stage. Most cnidarian neurotoxins remain conserved under the strong influence of negative selection. Neuroactive peptides targeting the central nervous system through affinity with ion channels could provide insight leading to drug treatment of neurological diseases, which arise from ion channel dysfunctions. Although marine resources offer thousands of possible peptides, only one peptide derived from Cnidaria: ShK-186, also named dalazatide, has reached the pharmaceutical market. This review focuses on neuroprotective agents derived from cnidarian neurotoxic peptides.
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Jiménez-Vargas JM, Possani LD, Luna-Ramírez K. Arthropod toxins acting on neuronal potassium channels. Neuropharmacology 2017; 127:139-160. [PMID: 28941737 DOI: 10.1016/j.neuropharm.2017.09.025] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 09/13/2017] [Accepted: 09/15/2017] [Indexed: 01/01/2023]
Abstract
Arthropod venoms are a rich mixture of biologically active compounds exerting different physiological actions across diverse phyla and affecting multiple organ systems including the central nervous system. Venom compounds can inhibit or activate ion channels, receptors and transporters with high specificity and affinity providing essential insights into ion channel function. In this review, we focus on arthropod toxins (scorpions, spiders, bees and centipedes) acting on neuronal potassium channels. A brief description of the K+ channels classification and structure is included and a compendium of neuronal K+ channels and the arthropod toxins that modify them have been listed. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- Juana María Jiménez-Vargas
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Lourival D Possani
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Avenida Universidad, 2001, Colonia Chamilpa, Apartado Postal 510-3, Cuernavaca 62210, Mexico
| | - Karen Luna-Ramírez
- Illawarra Health and Medical Research Institute, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
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Mauerhöfer M, Bauer CK. Effects of Temperature on Heteromeric Kv11.1a/1b and Kv11.3 Channels. Biophys J 2017; 111:504-523. [PMID: 27508435 DOI: 10.1016/j.bpj.2016.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 06/30/2016] [Accepted: 07/01/2016] [Indexed: 01/17/2023] Open
Abstract
Kv11.1 channels are crucial in cardiac physiology, and there is increasing evidence of physiological roles of different Kv11 channels outside the heart. The HERG (human Kv11.1a) channel has previously been shown to carry substantially more current at elevated temperatures, and we have now comparably investigated the temperature dependence of neuronal Kv11.3 channels and the more ubiquitous heteromeric Kv11.1a/1b channels. Transiently expressed rat Kv11 channels were studied at 21°C, 30°C, and 35°C. At near-physiological temperature, the maximal sustained outward current density was almost three times the mean value obtained at room temperature for Kv11.1a/1b, and increased by ∼150% for Kv11.3. For both channels, reduced inactivation contributed to the current increase at higher temperature. Elevated temperature moved Kv11.1a/1b isochronal activation curves to more negative potentials, but shifted the potential of half-maximal Kv11.3 channel activation to more depolarized values and reduced its voltage sensitivity. Thus, increased temperature stabilized the open state over the closed state of Kv11.1a/1b channels and exerted the opposite effect on Kv11.3 channel activation. Both Kv11 channels exhibited an overall high temperature sensitivity of most gating parameters, with remarkably high Q10 factors of ∼5 for the rate of Kv11.1a/1b activation. The Q10 factors for Kv11.3 gating were more uniform, but still higher for activation than for inactivation kinetics. The results demonstrate that characteristic differences between Kv11.1a/1b and Kv11.3 determined at room temperature do not necessarily apply to physiological conditions. The data provided here can aid in the design of models that will enhance our understanding of the role of Kv11 currents in excitable cells.
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Affiliation(s)
- Maike Mauerhöfer
- Department of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Christiane K Bauer
- Department of Cellular and Integrative Physiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
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Huang CS, Wang GH, Tai CH, Hu CC, Yang YC. Antiarrhythmics cure brain arrhythmia: The imperativeness of subthalamic ERG K + channels in parkinsonian discharges. SCIENCE ADVANCES 2017; 3:e1602272. [PMID: 28508055 PMCID: PMC5425237 DOI: 10.1126/sciadv.1602272] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Accepted: 03/15/2017] [Indexed: 06/07/2023]
Abstract
ERG K+ channels have long been known to play a crucial role in shaping cardiac action potentials and, thus, appropriate heart rhythms. The functional role of ERG channels in the central nervous system, however, remains elusive. We demonstrated that ERG channels exist in subthalamic neurons and have similar gating characteristics to those in the heart. ERG channels contribute crucially not only to the setting of membrane potential and, consequently, the firing modes, but also to the configuration of burst discharges and, consequently, the firing frequency and automaticity of the subthalamic neurons. Moreover, modulation of subthalamic discharges via ERG channels effectively modulates locomotor behaviors. ERG channel inhibitors ameliorate parkinsonian symptoms, whereas enhancers render normal animals hypokinetic. Thus, ERG K+ channels could be vital to the regulation of both cardiac and neuronal rhythms and may constitute an important pathophysiological basis and pharmacotherapeutic target for the growing list of neurological disorders related to "brain arrhythmias."
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Affiliation(s)
- Chen-Syuan Huang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Guan-Hsun Wang
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- School of Medicine, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Chun-Hwei Tai
- Department of Neurology, National Taiwan University Hospital, Taipei, Taiwan
| | - Chun-Chang Hu
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
| | - Ya-Chin Yang
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan
- Neuroscience Research Center, Chang Gung Memorial Hospital, Linkou Medical Center, Tao-Yuan, Taiwan
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Restano-Cassulini R, Garcia W, Paniagua-Solís JF, Possani LD. Antivenom Evaluation by Electrophysiological Analysis. Toxins (Basel) 2017; 9:E74. [PMID: 28241514 PMCID: PMC5371829 DOI: 10.3390/toxins9030074] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 02/21/2017] [Accepted: 02/21/2017] [Indexed: 12/17/2022] Open
Abstract
Scorpion stings on humans are medically relevant because they may contain toxins that specifically target ion channels. During antivenom production, pharmaceutical companies must use a large number of experimental animals to ensure the antivenom's efficacy according to pharmacopeia methods. Here we present an electrophysiological alternative for the evaluation of horse antivenoms produced against two species of Moroccan scorpions: Buthus mardochei and Androctonus mauretanicus. Human sodium and potassium channels and acetylcholine nicotinic receptors were analyzed by standard patch-clamp techniques. The results showed that the antivenom is capable of reversing ion current disruption caused by the venom application. We propose the use of this in vitro technique for antivenom evaluation as an alternative to using a large number of live animals.
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Affiliation(s)
- Rita Restano-Cassulini
- Instituto de Biotecnologia, National Autonomous University of México, Av. Univeresidad 2001, Col. Chamilpa, Cuernavaca 62210, Morelos, Mexico.
| | - Walter Garcia
- Instituto Bioclón S.A. de C.V., Calle Miguel Laurent 427, Del. Benito Juarez, Ciudad de México 03100, Mexico.
| | - Jorge F Paniagua-Solís
- Laboratorios Silanes, S.A. de C.V., Amores 1304, Colonia del Valle, Ciudad de México 03100, Mexico.
| | - Lourival D Possani
- Instituto de Biotecnologia, National Autonomous University of México, Av. Univeresidad 2001, Col. Chamilpa, Cuernavaca 62210, Morelos, Mexico.
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Housley DM, Housley GD, Liddell MJ, Jennings EA. Scorpion toxin peptide action at the ion channel subunit level. Neuropharmacology 2016; 127:46-78. [PMID: 27729239 DOI: 10.1016/j.neuropharm.2016.10.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/06/2016] [Accepted: 10/06/2016] [Indexed: 12/19/2022]
Abstract
This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of excitable tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'
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Affiliation(s)
- David M Housley
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia.
| | - Gary D Housley
- Translational Neuroscience Facility and Department of Physiology, School of Medical Sciences, UNSW Australia, Sydney, NSW 2052, Australia
| | - Michael J Liddell
- Centre for Tropical Environmental and Sustainability Science and College of Science & Engineering, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia
| | - Ernest A Jennings
- College of Medicine and Dentistry, Cairns Campus, James Cook University, Cairns, Queensland 4878, Australia; Centre for Biodiscovery and Molecular Development of Therapeutics, James Cook University, Queensland 4878, Australia; Australian Institute of Tropical Health and Medicine, James Cook University, Cairns Campus, QLD, Australia
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Rao VR, Perez-Neut M, Kaja S, Gentile S. Voltage-gated ion channels in cancer cell proliferation. Cancers (Basel) 2015; 7:849-75. [PMID: 26010603 PMCID: PMC4491688 DOI: 10.3390/cancers7020813] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 05/12/2015] [Indexed: 12/22/2022] Open
Abstract
Changes of the electrical charges across the surface cell membrane are absolutely necessary to maintain cellular homeostasis in physiological as well as in pathological conditions. The opening of ion channels alter the charge distribution across the surface membrane as they allow the diffusion of ions such as K+, Ca++, Cl.
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Affiliation(s)
- Vidhya R Rao
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago 2160 S. 1s tAve, Maywood, IL 60153, USA.
| | - Mathew Perez-Neut
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago 2160 S. 1s tAve, Maywood, IL 60153, USA.
| | - Simon Kaja
- Department of Ophthalmology and Vision Research Center, School of Medicine, University of Missouri-Kansas City, 2411 Holmes St., Kansas City, MO 64108, USA.
| | - Saverio Gentile
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago 2160 S. 1s tAve, Maywood, IL 60153, USA.
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11
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Quintero-Hernández V, Jiménez-Vargas J, Gurrola G, Valdivia H, Possani L. Scorpion venom components that affect ion-channels function. Toxicon 2013; 76:328-42. [PMID: 23891887 PMCID: PMC4089097 DOI: 10.1016/j.toxicon.2013.07.012] [Citation(s) in RCA: 193] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Accepted: 07/16/2013] [Indexed: 12/31/2022]
Abstract
The number and types of venom components that affect ion-channel function are reviewed. These are the most important venom components responsible for human intoxication, deserving medical attention, often requiring the use of specific anti-venoms. Special emphasis is given to peptides that recognize Na(+)-, K(+)- and Ca(++)-channels of excitable cells. Knowledge generated by direct isolation of peptides from venom and components deduced from cloned genes, whose amino acid sequences are deposited into databanks are nowadays in the order of 1.5 thousands, out of an estimate biodiversity closed to 300,000. Here the diversity of components is briefly reviewed with mention to specific references. Structural characteristic are discussed with examples taken from published work. The principal mechanisms of action of the three different types of peptides are also reviewed. Na(+)-channel specific venom components usually are modifier of the open and closing kinetic mechanisms of the ion-channels, whereas peptides affecting K(+)-channels are normally pore blocking agents. The Ryanodine Ca(++)-channel specific peptides are known for causing sub-conducting stages of the channels conductance and some were shown to be able to internalize penetrating inside the muscle cells.
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Affiliation(s)
- V. Quintero-Hernández
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
| | - J.M. Jiménez-Vargas
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
| | - G.B. Gurrola
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
- Cardiovascular Center 2139, Michigan University, Ann Arbor, MI 48109-5644, U.S.A
| | - H.H.F. Valdivia
- Cardiovascular Center 2139, Michigan University, Ann Arbor, MI 48109-5644, U.S.A
| | - L.D. Possani
- Department of Molecular Medicine and Bioprocesses, Instituto de Biotecnologia, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Apartado Postal 510-3, Cuernavaca 62210, Morelos, Mexico
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12
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Erg potassium currents of neonatal mouse Purkinje cells exhibit fast gating kinetics and are inhibited by mGluR1 activation. J Neurosci 2013; 33:16729-40. [PMID: 24133274 DOI: 10.1523/jneurosci.5523-12.2013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
We investigated the subthreshold properties of an erg (ether-à-go-go-related gene) K(+) current in Purkinje cells of neonatal mice. Action potentials recorded from Purkinje cells in cerebellar slices exhibited a decreased threshold potential and increased frequency of spontaneous and repetitive activity following application of the specific erg channel blocker E-4031. Accommodation was absent before and after drug application. The erg current of these Purkinje cells activated at membrane potentials near -60 mV and exhibited fast gating kinetics. The functional importance of fast gating subthreshold erg channels in Purkinje cells was corroborated by comparing the results of action potential clamp experiments with erg1a, erg1b, erg2, and erg3 currents heterologously expressed in HEK cells. Computer simulations based on a NEURON model of Purkinje cells only reproduced the effects of the native erg current when an erg channel conductance like that of erg3 was included. Experiments with subunit-sensitive toxins (BeKm-1, APETx1) indicated that erg channels in Purkinje cells are presumably mediated by heteromeric erg1/erg3 or modified erg1 channels. Following mGluR1 activation, the native erg current was reduced by ∼70%, brought about by reduction of the maximal erg current and a shift of the activation curve to more positive potentials. The Purkinje cell erg current contributed to the sustained current component of the biphasic mGluR1 response. Activation of mGluR1 by the agonist 3,4-dihydroxyphenylglycol increased Purkinje cell excitability, similar to that induced by E-4031. The results indicated that erg currents can be modulated and may contribute to the mGluR1-induced plasticity changes in Purkinje cells.
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Hayashi M, Novak I. Molecular basis of potassium channels in pancreatic duct epithelial cells. Channels (Austin) 2013; 7:432-41. [PMID: 23962792 PMCID: PMC4042478 DOI: 10.4161/chan.26100] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Potassium channels regulate excitability, epithelial ion transport, proliferation, and apoptosis. In pancreatic ducts, K+ channels hyperpolarize the membrane potential and provide the driving force for anion secretion. This review focuses on the molecular candidates of functional K+ channels in pancreatic duct cells, including KCNN4 (KCa3.1), KCNMA1 (KCa1.1), KCNQ1 (Kv7.1), KCNH2 (Kv11.1), KCNH5 (Kv10.2), KCNT1 (KCa4.1), KCNT2 (KCa4.2), and KCNK5 (K2P5.1). We will give an overview of K+ channels with respect to their electrophysiological and pharmacological characteristics and regulation, which we know from other cell types, preferably in epithelia, and, where known, their identification and functions in pancreatic ducts and in adenocarcinoma cells. We conclude by pointing out some outstanding questions and future directions in pancreatic K+ channel research with respect to the physiology of secretion and pancreatic pathologies, including pancreatitis, cystic fibrosis, and cancer, in which the dysregulation or altered expression of K+ channels may be of importance.
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Affiliation(s)
- Mikio Hayashi
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
| | - Ivana Novak
- Department of Biology; University of Copenhagen; Copenhagen, Denmark
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14
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Vandenberg JI, Perry MD, Perrin MJ, Mann SA, Ke Y, Hill AP. hERG K+ Channels: Structure, Function, and Clinical Significance. Physiol Rev 2012; 92:1393-478. [DOI: 10.1152/physrev.00036.2011] [Citation(s) in RCA: 463] [Impact Index Per Article: 38.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The human ether-a-go-go related gene (hERG) encodes the pore-forming subunit of the rapid component of the delayed rectifier K+ channel, Kv11.1, which are expressed in the heart, various brain regions, smooth muscle cells, endocrine cells, and a wide range of tumor cell lines. However, it is the role that Kv11.1 channels play in the heart that has been best characterized, for two main reasons. First, it is the gene product involved in chromosome 7-associated long QT syndrome (LQTS), an inherited disorder associated with a markedly increased risk of ventricular arrhythmias and sudden cardiac death. Second, blockade of Kv11.1, by a wide range of prescription medications, causes drug-induced QT prolongation with an increase in risk of sudden cardiac arrest. In the first part of this review, the properties of Kv11.1 channels, including biogenesis, trafficking, gating, and pharmacology are discussed, while the second part focuses on the pathophysiology of Kv11.1 channels.
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Affiliation(s)
- Jamie I. Vandenberg
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Matthew D. Perry
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Mark J. Perrin
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Stefan A. Mann
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Ying Ke
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
| | - Adam P. Hill
- Mark Cowley Lidwill Research Programme in Cardiac Electrophysiology, Victor Chang Cardiac Research Institute, Sydney, New South Wales, Australia; St Vincent's Clinical School, University of New South Wales, New South Wales, Australia; and University of Ottawa Heart Institute, Ottawa, Canada
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15
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Jiménez-Vargas JM, Restano-Cassulini R, Possani LD. Toxin modulators and blockers of hERG K(+) channels. Toxicon 2012; 60:492-501. [PMID: 22497787 DOI: 10.1016/j.toxicon.2012.03.024] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 03/27/2012] [Indexed: 12/24/2022]
Abstract
The K(+) channel encoded by the Ether-á-go-go-Related Gene (ERG) is expressed in different tissues of different animal species. There are at least three subtypes of this channel, being the sub-type 1 (ERG1) crucial in the repolarization phase of the cardiac action potential. Mutations in this gene can affect the properties of the channel producing the type II long QT syndrome (LQTS2) and many drugs are also known to affect this channel with a similar side effect. Various scorpion, spider and sea anemone toxins affect the ERG currents by blocking the ion-conducting pore from the external side or by modulating channel gating through binding to the voltage-sensor domain. By doing so, these toxins become very useful tools for better understanding the structural and functional characteristics of these ion channels. This review discusses the interaction between the ERG channels and the peptides isolated from venoms of these animals. Special emphasis is placed on scorpion toxins, although the effects of several spider venom toxins and anemone toxins will be also revised.
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Affiliation(s)
- J M Jiménez-Vargas
- Department of Molecular Medicine and Bioprocesses, Institute of Biotechnology, National Autonomous University of Mexico, Av. Universidad 2001, P.O. Box 501-3, Cuernavaca 62210, Mexico.
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Isolation and characterization of two novel scorpion toxins: The alpha-toxin-like CeII8, specific for Na(v)1.7 channels and the classical anti-mammalian CeII9, specific for Na(v)1.4 channels. Toxicon 2010; 56:613-23. [PMID: 20600228 DOI: 10.1016/j.toxicon.2010.06.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 06/08/2010] [Accepted: 06/11/2010] [Indexed: 11/23/2022]
Abstract
Scorpion beta-toxins represent a particular pharmacological group of voltage-gated sodium channel (VGSC) neurotoxins. They typically shift the voltage dependence of activation to more hyperpolarizing potentials and reduce the peak current amplitude by binding to receptor-site 4. Here, we report the purification and functional characterization of the first voltage-gated sodium channel toxins, CeII8 and CeII9, isolated from the scorpion Centruroides elegans (Thorell, 1876), which is responsible for deadly cases of intoxication in Mexico. The soluble venom was fractionated by gel filtration and ion-exchange chromatography, followed by reversed-phase HPLC. The toxins CeII8 and CeII9 were further purified and both their amino acid sequence and molecular weight were determined. Both toxins were electrophysiologically characterized on four mammalian VGSCs (rNa(v)1.2, rNa(v)1.4, hNa(v)1.5 and rNa(v)1.7) expressed heterologously in Xenopus laevis oocytes, using the two-electrode voltage-clamp technique. Although CeII8 has the highest sequence similarity with scorpion alpha-toxins, inhibiting the inactivation of VGSCs, 300 nM toxin had a clear beta-toxin effect and was selective towards Na(v)1.7, involved in short-term and inflammatory pain. To the best of our knowledge, CeII8 is the first beta-toxin active on Na(v)1.7. CeII9, a typical anti-mammalian beta-toxin, selectively modulated Na(v)1.4 at a concentration of 700 nM and was, in contrast to CeII8, found to be lethal to mice. Interestingly, both toxins, despite their differences in amino acid sequence, only altered the biophysical properties of a fraction of the expressed sodium channels. Since these effects have also been reported for the beta-toxin CssIV, the bioactive surfaces of the toxins have been compared to each other.
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17
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Arcangeli A, Becchetti A. New Trends in Cancer Therapy: Targeting Ion Channels and Transporters. Pharmaceuticals (Basel) 2010; 3:1202-1224. [PMID: 27713296 PMCID: PMC4034029 DOI: 10.3390/ph3041202] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 03/25/2010] [Accepted: 03/29/2010] [Indexed: 02/07/2023] Open
Abstract
The expression and activity of different channel types mark and regulate specific stages of cancer establishment and progression. Blocking channel activity impairs the growth of some tumors, both in vitro and in vivo, which opens a new field for pharmaceutical research. However, ion channel blockers may produce serious side effects, such as cardiac arrhythmias. For instance, Kv11.1 (hERG1) channels are aberrantly expressed in several human cancers, in which they control different aspects of the neoplastic cell behaviour. hERG1 blockers tend to inhibit cancer growth. However they also retard the cardiac repolarization, thus lengthening the electrocardiographic QT interval, which can lead to life-threatening ventricular arrhythmias. Several possibilities exist to produce less harmful compounds, such as developing specific drugs that bind hERG1 channels in the open state or disassemble the ion channel/integrin complex which appears to be crucial in certain stages of neoplastic progression. The potential approaches to improve the efficacy and safety of ion channel targeting in oncology include: (1) targeting specific conformational channel states; (2) finding ever more specific inhibitors, including peptide toxins, for channel subtypes mainly expressed in well-identified tumors; (3) using specific ligands to convey traceable or cytotoxic compounds; (4) developing channel blocking antibodies; (5) designing new molecular tools to decrease channel expression in selected cancer types. Similar concepts apply to ion transporters such as the Na⁺/K⁺ pump and the Na⁺/H⁺ exchanger. Pharmacological targeting of these transporters is also currently being considered in anti-neoplastic therapy.
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Affiliation(s)
- Annarosa Arcangeli
- Department of Experimental Pathology and Oncology, University of Florence, Italy.
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Italy.
| | - Andrea Becchetti
- Department of Experimental Pathology and Oncology, University of Florence, Italy
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Italy
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18
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Raschi E, Ceccarini L, De Ponti F, Recanatini M. hERG-related drug toxicity and models for predicting hERG liability and QT prolongation. Expert Opin Drug Metab Toxicol 2009; 5:1005-21. [PMID: 19572824 DOI: 10.1517/17425250903055070] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND hERG K(+) channels have been recognized as a primary antitarget in safety pharmacology. Their blockade, caused by several drugs with different therapeutic indications, may lead to QT prolongation and, eventually, to potentially fatal arrhythmia, namely torsade de pointes. Therefore, a number of preclinical models have been developed to predict hERG liability early in the drug development process. OBJECTIVE The aim of this review is to outline the present state of the art on drug-induced hERG blockade, providing insights on the predictive value of in vitro and in silico models for hERG liability. METHODS On the basis of latest reports, high-throughput preclinical models have been discussed outlining advantages and limitations. CONCLUSION Although no single model has an absolute value, an integrated risk assessment is recommended to predict the pro-arrhythmic risk of a given drug. This prediction requires expertise from different areas and should encompass emerging issues such as interference with hERG trafficking and QT shortening.
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Affiliation(s)
- Emanuel Raschi
- University of Bologna, Department of Pharmacology, Italy
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19
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Redaelli E, Cassulini RR, Silva DF, Clement H, Schiavon E, Zamudio FZ, Odell G, Arcangeli A, Clare JJ, Alagón A, de la Vega RCR, Possani LD, Wanke E. Target promiscuity and heterogeneous effects of tarantula venom peptides affecting Na+ and K+ ion channels. J Biol Chem 2009; 285:4130-4142. [PMID: 19955179 DOI: 10.1074/jbc.m109.054718] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Venom-derived peptide modulators of ion channel gating are regarded as essential tools for understanding the molecular motions that occur during the opening and closing of ion channels. In this study, we present the characterization of five spider toxins on 12 human voltage-gated ion channels, following observations about the target promiscuity of some spider toxins and the ongoing revision of their "canonical" gating-modifying mode of action. The peptides were purified de novo from the venom of Grammostola rosea tarantulas, and their sequences were confirmed by Edman degradation and mass spectrometry analysis. Their effects on seven tetrodotoxin-sensitive Na(+) channels, the three human ether-à-go-go (hERG)-related K(+) channels, and two human Shaker-related K(+) channels were extensively characterized by electrophysiological techniques. All the peptides inhibited ion conduction through all the Na(+) channels tested, although with distinctive patterns. The peptides also affected the three pharmaceutically relevant hERG isoforms differently. At higher concentrations, all peptides also modified the gating of the Na(+) channels by shifting the activation to more positive potentials, whereas more complex effects were recorded on hERG channels. No effects were evident on the two Shaker-related K(+) channels at concentrations well above the IC(50) value for the affected channels. Given the sequence diversity of the tested peptides, we propose that tarantula toxins should be considered both as multimode and target-promiscuous ion channel modulators; both features should not be ignored when extracting mechanistic interpretations about ion channel gating. Our observations could also aid in future structure-function studies and might help the development of novel ion channel-specific drugs.
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Affiliation(s)
- Elisa Redaelli
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy
| | - Rita Restano Cassulini
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy; the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Deyanira Fuentes Silva
- the Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán DF 04510, México
| | - Herlinda Clement
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Emanuele Schiavon
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy
| | - Fernando Z Zamudio
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - George Odell
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Annarosa Arcangeli
- the Dipartimento di Patologia e Oncologia Sperimentali, Università di Firenze, Viale Morgagni 50, 50134 Firenze, Italy
| | - Jeffrey J Clare
- Gene Expression and Protein Biochemistry, GlaxoSmithKline, Medicines Research Centre, Gunnels Wood Road, Stevenage, Herts SG1 2NY, United Kingdom, and
| | - Alejandro Alagón
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Ricardo C Rodríguez de la Vega
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México; the Structural and Computational Biology/Genome Biology Units, European Molecular Biology Laboratory, Meyerhofstrasse 1, Heidelberg 69117, Germany
| | - Lourival D Possani
- the Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca 62210, México
| | - Enzo Wanke
- From the Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, 20126 Milan, Italy.
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21
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Hardy AB, Fox JEM, Giglou PR, Wijesekara N, Bhattacharjee A, Sultan S, Gyulkhandanyan AV, Gaisano HY, MacDonald PE, Wheeler MB. Characterization of Erg K+ channels in alpha- and beta-cells of mouse and human islets. J Biol Chem 2009; 284:30441-52. [PMID: 19690348 DOI: 10.1074/jbc.m109.040659] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated eag-related gene (Erg) K(+) channels regulate the electrical activity of many cell types. Data regarding Erg channel expression and function in electrically excitable glucagon and insulin producing cells of the pancreas is limited. In the present study Erg1 mRNA and protein were shown to be highly expressed in human and mouse islets and in alpha-TC6 and Min6 cells alpha- and beta-cell lines, respectively. Whole cell patch clamp recordings demonstrated the functional expression of Erg1 in alpha- and beta-cells, with rBeKm1, an Erg1 antagonist, blocking inward tail currents elicited by a double pulse protocol. Additionally, a small interference RNA approach targeting the kcnh2 gene (Erg1) induced a significant decrease of Erg1 inward tail current in Min6 cells. To investigate further the role of Erg channels in mouse and human islets, ratiometric Fura-2 AM Ca(2+)-imaging experiments were performed on isolated alpha- and beta-cells. Blocking Erg channels with rBeKm1 induced a transient cytoplasmic Ca(2+) increase in both alpha- and beta-cells. This resulted in an increased glucose-dependent insulin secretion, but conversely impaired glucagon secretion under low glucose conditions. Together, these data present Erg1 channels as new mediators of alpha- and beta-cell repolarization. However, antagonism of Erg1 has divergent effects in these cells; to augment glucose-dependent insulin secretion and inhibit low glucose stimulated glucagon secretion.
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Affiliation(s)
- Alexandre B Hardy
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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22
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Homeostatic control of sensory output in basal vomeronasal neurons: activity-dependent expression of ether-à-go-go-related gene potassium channels. J Neurosci 2009; 29:206-21. [PMID: 19129398 DOI: 10.1523/jneurosci.3656-08.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Conspecific chemosensory communication controls a broad range of social and sexual behaviors. In most mammals, social chemosignals are predominantly detected by sensory neurons of a specialized olfactory subsystem, the vomeronasal organ (VNO). The behavioral relevance of social chemosignaling puts high demands on the accuracy and dynamic range of the underlying transduction mechanisms. However, the physiological concepts implemented to ensure faithful transmission of social information remain widely unknown. Here, we show that sensory neurons in the basal layer of the mouse VNO dynamically control their input-output relationship by activity-dependent regulation of K(+) channel gene expression. Using large-scale expression profiling, immunochemistry, and electrophysiology, we provide molecular and functional evidence for a role of ether-à-go-go-related gene (ERG) K(+) channels as key determinants of cellular excitability. Our findings indicate that an increase in ERG channel expression extends the dynamic range of the stimulus-response function in basal vomeronasal sensory neurons. This novel mechanism of homeostatic plasticity in the periphery of the accessory olfactory system is ideally suited to adjust VNO neurons to a target output range in a layer-specific and use-dependent manner.
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Greenwood IA, Yeung SY, Tribe RM, Ohya S. Loss of functional K+ channels encoded by ether-à-go-go-related genes in mouse myometrium prior to labour onset. J Physiol 2009; 587:2313-26. [PMID: 19332483 DOI: 10.1113/jphysiol.2009.171272] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
There is a growing appreciation that ion channels encoded by the ether-à-go-go-related gene family have a functional impact in smooth muscle in addition to their accepted role in cardiac myocytes and neurones. This study aimed to assess the expression of ERG1-3 (KCNH1-3) genes in the murine myometrium (smooth muscle layer of the uterus) and determine the functional impact of the ion channels encoded by these genes in pregnant and non-pregnant animals. Quantitative RT-PCR did not detect message for ERG2 and 3 in whole myometrial tissue extracts. In contrast, message for two isoforms of mERG1 were readily detected with mERG1a more abundant than mERG1b. In isometric tension studies of non-pregnant myometrium, the ERG channel blockers dofetilide (1 microM), E4031 (1 microM) and Be-KM1 (100 nM) increased spontaneous contractility and ERG activators (PD118057 and NS1643) inhibited spontaneous contractility. In contrast, neither ERG blockade nor activation had any effect on the inherent contractility in myometrium from late pregnant (19 days gestation) animals. Moreover, dofetilide-sensitive K(+) currents with distinctive 'hooked' kinetics were considerably smaller in uterine myocytes from late pregnant compared to non-pregnant animals. Expression of mERG1 isoforms did not alter throughout gestation or upon delivery, but the expression of genes encoding auxillary subunits (KCNE) were up-regulated considerably. This study provides the first evidence for a regulation of ERG-encoded K(+) channels as a precursor to late pregnancy physiological activity.
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Affiliation(s)
- I A Greenwood
- Division of Basic Medical Sciences, Ion Channels And Cell Signaling Research Centre, St George's, University of London, London SW17 0RE, UK.
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24
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Functional properties of human neuronal Kv11 channels. Pflugers Arch 2009; 458:689-700. [DOI: 10.1007/s00424-009-0651-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 02/12/2009] [Indexed: 11/25/2022]
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Diochot S, Lazdunski M. Sea anemone toxins affecting potassium channels. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2009; 46:99-122. [PMID: 19184586 DOI: 10.1007/978-3-540-87895-7_4] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The great diversity of K(+) channels and their wide distribution in many tissues are associated with important functions in cardiac and neuronal excitability that are now better understood thanks to the discovery of animal toxins. During the past few decades, sea anemones have provided a variety of toxins acting on voltage-sensitive sodium and, more recently, potassium channels. Currently there are three major structural groups of sea anemone K(+) channel (SAK) toxins that have been characterized. Radioligand binding and electrophysiological experiments revealed that each group contains peptides displaying selective activities for different subfamilies of K(+) channels. Short (35-37 amino acids) peptides in the group I display pore blocking effects on Kv1 channels. Molecular interactions of SAK-I toxins, important for activity and binding on Kv1 channels, implicate a spot of three conserved amino acid residues (Ser, Lys, Tyr) surrounded by other less conserved residues. Long (58-59 amino acids) SAK-II peptides display both enzymatic and K(+) channel inhibitory activities. Medium size (42-43 amino acid) SAK-III peptides are gating modifiers which interact either with cardiac HERG or Kv3 channels by altering their voltage-dependent properties. SAK-III toxins bind to the S3C region in the outer vestibule of Kv channels. Sea anemones have proven to be a rich source of pharmacological tools, and some of the SAK toxins are now useful drugs for the diagnosis and treatment of autoimmune diseases.
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Affiliation(s)
- Sylvie Diochot
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifi que, Université de Nice-Sophia-Antipolis, 660 Route des Lucioles, Valbonne, 06560, France
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Guasti L, Crociani O, Redaelli E, Pillozzi S, Polvani S, Masselli M, Mello T, Galli A, Amedei A, Wymore RS, Wanke E, Arcangeli A. Identification of a posttranslational mechanism for the regulation of hERG1 K+ channel expression and hERG1 current density in tumor cells. Mol Cell Biol 2008; 28:5043-60. [PMID: 18559421 PMCID: PMC2519704 DOI: 10.1128/mcb.00304-08] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 03/25/2008] [Accepted: 06/04/2008] [Indexed: 01/19/2023] Open
Abstract
A common feature of tumor cells is the aberrant expression of ion channels on their plasma membrane. The molecular mechanisms regulating ion channel expression in cancer cells are still poorly known. K(+) channels that belong to the human ether-a-go-go-related gene 1 (herg1) family are frequently misexpressed in cancer cells compared to their healthy counterparts. We describe here a posttranslational mechanism for the regulation of hERG1 channel surface expression in cancer cells. This mechanism is based on the activity of hERG1 isoforms containing the USO exon. These isoforms (i) are frequently overexpressed in human cancers, (ii) are retained in the endoplasmic reticulum, and (iii) form heterotetramers with different proteins of the hERG family. (iv) The USO-containing heterotetramers are retained intracellularly and undergo ubiquitin-dependent degradation. This process results in decreased hERG1 current (I(hERG1)) density. We detailed such a mechanism in heterologous systems and confirmed its functioning in tumor cells that endogenously express hERG1 proteins. The silencing of USO-containing hERG1 isoforms induces a higher I(hERG1) density in tumors, an effect that apparently regulates neurite outgrowth in neuroblastoma cells and apoptosis in leukemia cells.
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Affiliation(s)
- Leonardo Guasti
- Department of Experimental Pathology and Oncology, University of Florence, Viale G. B. Morgagni 50, 50134 Florence, Italy
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Pasquarelli A. Biochips: Technologies and applications. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2008. [DOI: 10.1016/j.msec.2007.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Honma T, Kawahata S, Ishida M, Nagai H, Nagashima Y, Shiomi K. Novel peptide toxins from the sea anemone Stichodactyla haddoni. Peptides 2008; 29:536-44. [PMID: 18243416 DOI: 10.1016/j.peptides.2007.12.010] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 12/13/2007] [Accepted: 12/14/2007] [Indexed: 11/24/2022]
Abstract
Four peptide toxins, SHTX I-III with crab-paralyzing activity and SHTX IV with crab lethality, were isolated from the sea anemone Stichodactyla haddoni and their primary structures elucidated by protein sequencing and cDNA cloning. SHTX I (new toxin, 28 residues), II (analogue of SHTX I, 28 residues) and III (Kunitz-type protease inhibitor, 62 residues) are potassium channel toxins and SHTX IV (48 residues) is a member of the type 2 sea anemone sodium channel toxins. The precursor protein of SHTX IV is composed of a signal peptide, propart and mature peptide, while the propart is missing in that of SHTX III. In addition to these four toxins, an epidermal growth factor-like peptide was detected in S. haddoni by RT-PCR.
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Affiliation(s)
- Tomohiro Honma
- Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Konan-4, Tokyo 108-8477, Japan
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Two novel ergtoxins, blockers of K+-channels, purified from the Mexican scorpion Centruroides elegans elegans. Neurochem Res 2008; 33:1525-33. [PMID: 18338253 DOI: 10.1007/s11064-008-9634-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Accepted: 02/19/2008] [Indexed: 10/22/2022]
Abstract
Voltage-gated potassium channels of the ether-a-go-go related gene (ERG) family are implicated in many important cellular processes. Three such genes have been cloned (erg1, erg2 and erg3) and shown to be expressed in the central nervous system (CNS) of mammalians. This communication describes the isolation and characterization of two isoforms of scorpion toxin (CeErg4 and CeErg5, systematic nomenclature gamma-KTx1.7 and gamma-KTx1.8, respectively) that can discriminate the various subtypes of ERG channels of human and rat. These peptides were purified from the venom of the Mexican scorpion Centruroides elegans elegans. They contain 42 amino acid residues, tightly folded by four disulfide bridges. Both peptides block in a reversible manner human and rat ERG1 channels, but have no effect on human ERG2. They also block completely and irreversibly the rat ERG2 and the human ERG3 channels hence are excellent tools for the discrimination of the various sub-types of ion-channels studied.
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Martínez A, Santiago JL, Cénit MC, de Las Heras V, de la Calle H, Fernández-Arquero M, Arroyo R, de la Concha EG, Urcelay E. IFIH1-GCA-KCNH7 locus: influence on multiple sclerosis risk. Eur J Hum Genet 2008; 16:861-4. [PMID: 18285833 DOI: 10.1038/ejhg.2008.16] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
A recent genome-wide scan of nonsynonymous SNPs and ulterior validation in case-control and family analyses evidenced a susceptibility locus for type 1 diabetes (T1D) on chromosome 2q24.3. We aimed at testing the effect of this locus in other autoimmune diseases with complex genetic background, such as multiple sclerosis (MS). Four SNPs along the locus, rs13422767, rs2111485, rs1990760 and rs2068330, were genotyped using TaqMan MGB chemistry in 311 T1D and 412 MS patients and 535 ethnically matched healthy controls. The previously reported association of this locus was found for the first time in MS (rs2068330, G vs C: P=0.001; OR (95% CI)=0.73 (0.6-0.88)) and a trend for replication was observed in our Spanish diabetic cohort. Therefore, genes included in this locus - IFIH1 interferon induced helicase, GCA grancalcin or the potassium channel KCNH7 - are potential candidates implicated in the pathogenesis of these autoimmune diseases, although strong linkage disequilibrium in the region hampered further localization of the etiologic gene.
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Affiliation(s)
- Alfonso Martínez
- Department of Immunology, Hospital Universitario San Carlos, Madrid, Spain
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31
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Raschi E, Vasina V, Poluzzi E, De Ponti F. The hERG K+ channel: target and antitarget strategies in drug development. Pharmacol Res 2008; 57:181-95. [PMID: 18329284 DOI: 10.1016/j.phrs.2008.01.009] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/21/2008] [Accepted: 01/22/2008] [Indexed: 12/16/2022]
Abstract
The human ether-à-go-go related gene (hERG) K+ channel is of great interest for both basic researchers and clinicians because its blockade by drugs can lead to QT prolongation, which is a risk factor for torsades de pointes, a potentially life-threatening arrhythmia. A growing list of agents with "QT liability" have been withdrawn from the market or restricted in their use, whereas others did not even receive regulatory approval for this reason. Thus, hERG K+ channels have become a primary antitarget (i.e. an unwanted target) in drug development because their blockade causes potentially serious side effects. On the other hand, the recent identification and functional characterization of hERG K+ channels not only in the heart, but also in several other tissues (e.g. neurons, smooth muscle and cancer cells) may have far reaching implications for drug development for a possible exploitation of hERG as a target, especially in oncology and cardiology.
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Affiliation(s)
- Emanuel Raschi
- Department of Pharmacology, University of Bologna, Via Irnerio, 48, I-40126 Bologna BO, Bologna, Italy
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32
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Elmedyb P, Olesen SP, Grunnet M. Activation of ERG2 potassium channels by the diphenylurea NS1643. Neuropharmacology 2007; 53:283-94. [PMID: 17610913 DOI: 10.1016/j.neuropharm.2007.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2007] [Revised: 03/30/2007] [Accepted: 05/15/2007] [Indexed: 12/01/2022]
Abstract
Three members of the ERG potassium channel family have been described (ERG1-3 or Kv 11.1-3). ERG1 is by far the best characterized subtype and it constitutes the molecular component of the cardiac I(Kr) current. All three channel subtypes are expressed in neurons but their function remains unclear. The lack of functional information is at least partly due to the lack of specific pharmacological tools. The compound NS1643 has earlier been reported as an ERG1 channel activator. We found that NS1643 also activates the ERG2 channel; however, the molecular mechanism of the activation differs between the ERG1 and ERG2 channels. This is surprising since ERG1 and ERG2 channels have very similar biophysical and structural characteristics. For ERG2, NS1643 causes a left-ward shift of the activation curve, a faster time-constant of activation and a slower time-constant of inactivation as well as an increased relative importance for the fast component of deactivation to the total deactivation. In contrast, for ERG1, NS1643 causes a right-ward shift in the voltage-dependent release from inactivation but does not affect time-constants of deactivation. Because of these differences in the responses of ERG1 and ERG2 to NS1643, NS1643 can be used as a pharmacological tool to address ERG channel function. It may be useful for revealing physiological functions of ERG channels in neuronal tissue as well as to elucidate the structure-function relationships of the ERG channels.
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Affiliation(s)
- Pernille Elmedyb
- The Danish National Research Foundation Centre for Cardiac Arrhythmia, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
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33
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Zhang M, Liu XS, Diochot S, Lazdunski M, Tseng GN. APETx1 from Sea Anemone Anthopleura elegantissima Is a Gating Modifier Peptide Toxin of the Human Ether-a-go-go- Related Potassium Channel. Mol Pharmacol 2007; 72:259-68. [PMID: 17473056 DOI: 10.1124/mol.107.035840] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We studied the mechanism of action and the binding site of APETx1, a peptide toxin purified from sea anemone, on the human ether-a-go-go-related gene (hERG) channel. Similar to the effects of gating modifier toxins (hanatoxin and SGTx) on the voltage-gated potassium (Kv) 2.1 channel, APETx1 shifts the voltage-dependence of hERG activation in the positive direction and suppresses its current amplitudes elicited by strong depolarizing pulses that maximally activate the channels. The APETx1 binding site is distinctly different from that of a pore-blocking peptide toxin, BeKm-1. Mutations in the S3b region of hERG have dramatic impact on the responsiveness to APETx1: G514C potentiates whereas E518C abolishes the APETx1 effect. Restoring the negative charge at position 518 (methanethiosulfonate ethylsulfonate modification of 518C) partially restores APETx1 responsiveness, supporting an electrostatic interaction between E518 and APETx1. Among the three hERG isoforms, hERG1 and hERG3 are equally responsive to APETx1, whereas hERG2 is insensitive. The key feature seems to be an arginine residue uniquely present at the 514-equivalent position in hERG2, where the other two isoforms possess a glycine. Our data show that APETx1 is a gating modifier toxin of the hERG channel, and its binding site shares characteristics with those of gating modifier toxin binding sites on other Kv channels.
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Affiliation(s)
- M Zhang
- Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, 1101 E. Marshall Street, Richmond, VA 23298, USA
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34
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Wanke E, Restano-Cassulini R. Toxins interacting with ether-à-go-go-related gene voltage-dependent potassium channels. Toxicon 2007; 49:239-48. [PMID: 17097705 DOI: 10.1016/j.toxicon.2006.09.025] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The critical role that ether-à-go-go-related gene (erg) K(+) channels play in mating in Caenorhabditis elegans, neuronal seizures in Drosophila and cardiac action potential repolarization in humans has been well documented. Three erg genes (erg1, erg2 and erg3) have been identified and characterized. A structurally diverse number of compounds block these channels, but do not display specificity among the different channel isoforms. In this review we describe the blocking properties of several peptides, purified from scorpion, sea anemone and spider venoms, which are selective for certain members of the ERG family of channels. These peptides do not behave as classical pore blockers and appear to modify the gating properties of the channel. Genomic studies predict the existence of many other novel peptides with the potential of being more selective for ERG channels than those discussed here.
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Affiliation(s)
- Enzo Wanke
- Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Piazza della Scienza 2, 20126 Milano, Italy.
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Solntseva EI, Bukanova JV, Marchenko E, Skrebitsky VG. Donepezil is a strong antagonist of voltage-gated calcium and potassium channels in molluscan neurons. Comp Biochem Physiol C Toxicol Pharmacol 2007; 144:319-26. [PMID: 17126610 DOI: 10.1016/j.cbpc.2006.10.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Revised: 10/04/2006] [Accepted: 10/15/2006] [Indexed: 11/24/2022]
Abstract
Donepezil is an acetylcholinesterase inhibitor used in Alzheimer's disease therapy. The neuroprotective effect of donepezil has been demonstrated in a number of different models of neurodegeneration including beta-amyloid toxicity. Since the mechanisms of neurodegeneration involve the activation of both Ca(2+)- and K(+)-channels, the study of donepezil action on voltage-gated ionic currents looked advisable. In the present study, the action of donepezil on voltage-gated Ca(2+)- and K(+)-channels was investigated on isolated neurons of the edible snail (Helix pomatia) using the two-microelectrodes voltage-clamp technique. Donepezil rapidly and reversibly inhibited voltage activated Ca(2+)-current (I(Ca)) (IC(50)=7.9 microM) and three types of high threshold K(+)-current: Ca(2+)-dependent K(+)-current (I(C)) (IC(50)=6.4 microM), delayed rectifier K(+)-current (I(DR)) (IC(50)=8.0 microM) and fast transient K(+)-current (I(Adepol)) (IC(50)=9.1 microM). The drug caused a dual effect on low-threshold fast transient K(+)-current (I(A)), potentiating it at low (5 microM) concentration, but inhibiting at higher (7 microM and above) concentration. Donepezil also caused a significant hyperpolarizing shift of the voltage-current relationship of I(Ca) (but not of any type of K(+)-current). Results suggest the possible contribution of the blocking effect of donepezil on the voltage-gated Ca(2+)- and K(+)-channels to the neuroprotective effect of the drug.
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Affiliation(s)
- Elena I Solntseva
- Brain Research Institute, Russian Academy of Medical Sciences, Per. Obukha, 5, 105064, Moscow, Russia
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Abstract
Acid-sensing ion channels (ASICs) channels are proton-gated cationic channels mainly expressed in central and peripheric nervous system and related to the epithelial amiloride-sensitive Na(+) channels and to the degenerin family of ion channels. ASICs comprise four proteins forming functional channel subunits (ASIC1a, ASIC1b, ASIC2a, and ASIC3) and two proteins (ASIC2b and ASIC4) without yet known activators. Functional channels are activated by external pH variations ranging from pH(0.5) 6.8 to 4.0 and currents are characterized by either rapid kinetics of inactivation (ASIC1a, ASIC1b, ASIC3) or slow kinetics of inactivation (ASIC2a) and sometimes the presence of a plateau phase (ASIC3). ASIC1a and ASIC3, which are expressed in nociceptive neurons, have been implicated in inflammation and knockout mice studies support the role of ASIC3 in various pain processes. ASIC1a seems more related to synaptic plasticity, memory, learning and fear conditioning in the CNS. ASIC2a contributes to hearing in the cochlea, sour taste sensation, and visual transduction in the retina. The pharmacology of ASICs is limited to rather nonselective drugs such as amiloride, nonsteroid anti-inflammatory drugs, and neuropeptides. Recently, two peptides, PcTx1 and APETx2, isolated from a spider and a sea anemone, have been characterized as selective and high-affinity inhibitors for ASIC1a and ASIC3 channels, respectively. PcTx1 inhibits ASIC1a homomers with an affinity of 0.7 nM (IC(50)) without any effect on ASIC1a containing heteromers and thus helped to characterize ASIC1a homomeric channels in peripheric and central neurons. PcTx1 acts as a gating modifier since it shifts the channel from the resting to an inactivated state by increasing its affinity for H(+). APETx2 is less selective since it inhibits several ASIC3-containing channels (IC(50) from 63 nM to 2 microM) and to date its mode of action is unknown. Nevertheless, APETx2 structure is related to other sea anemone peptides, which act as gating modifiers on Nav and Kv channels.
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Affiliation(s)
- S Diochot
- Institut de Pharmacologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Sophia-Antipolis, 660 Route des Lucioles, 06560 Valbonne, France
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37
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Abstract
Voltage-activated ion channels open and close in response to changes in membrane voltage, a process that is crucial for electrical signaling in the nervous system. The venom from many poisonous creatures contains a diverse array of small protein toxins that bind to voltage-activated channels and modify the gating mechanism. Hanatoxin and a growing number of related tarantula toxins have been shown to inhibit activation of voltage-activated potassium (K(v)) channels by interacting with their voltage-sensing domains. This review summarizes our current understanding of the mechanism by which these toxins alter gating, the location of the toxin receptor within K(v) channels and the disposition of this receptor with respect to the lipid membrane. The conservation of tarantula toxin receptors among voltage-activated ion channels will also be discussed.
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Affiliation(s)
- Kenton J Swartz
- Molecular Physiology and Biophysics Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
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Yeung SYM, Greenwood IA. Pharmacological and biophysical isolation of K+ currents encoded by ether-à-go-go-related genes in murine hepatic portal vein smooth muscle cells. Am J Physiol Cell Physiol 2006; 292:C468-76. [PMID: 16870833 DOI: 10.1152/ajpcell.00142.2006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have shown that murine portal vein myocytes express ether-à-go-go related genes (ERGs) and exhibit distinctive currents when recorded under symmetrical K(+) conditions. The aim of the present study was to characterize ERG channel currents evoked from a negative holding potential under conditions more pertinent to a physiological scenario to assess the possible functional impact of this conductance. Currents were recorded with ruptured or perforated patch variants of the whole cell technique from a holding potential of -60 mV. Application of three structurally distinct and selective ERG channel blockers, E-4031, dofetilide, and the peptide toxin BeKM-1, all inhibited a significant proportion of the outward current and abolished inward currents with distinctive "hooked" kinetics recorded on repolarization. Dofetilide-sensitive currents at negative potentials evoked by depolarization to +40 mV had a voltage-dependent time to peak and rate of decay characteristic of ERG channels. Application of the novel ERG channel activator PD-118057 (1-10 microM) markedly enhanced the hooked inward currents evoked by membrane depolarization and hyperpolarized the resting membrane potential recorded by current clamp and the perforated patch configuration by approximately 20 mV. In contrast, ERG channel blockade by dofetilide (1 microM) depolarized the resting membrane potential by approximately 8 mV. These data are the first record of ERG channel currents in smooth muscle cells under quasi-physiological conditions that suggest that ERG channels contribute to the resting membrane potential in these cells.
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Affiliation(s)
- Shuk Yin M Yeung
- Division of Basic Medical Sciences, Ion Channels and Cell Signalling Research Centre, St. George's, University of London, London SW17 0RE, UK
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