1
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Müller S, Kartheus M, Hendinger E, Hübner DC, Schnell E, Rackow S, Bertsche A, Köhling R, Kirschstein T. Persistent Kv7.2/7.3 downregulation in the rat pilocarpine model of mesial temporal lobe epilepsy. Epilepsy Res 2024; 200:107296. [PMID: 38219422 DOI: 10.1016/j.eplepsyres.2024.107296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 12/04/2023] [Accepted: 01/05/2024] [Indexed: 01/16/2024]
Abstract
Mutations within the Kv7.2 and Kv7.3 genes are well described causes for genetic childhood epilepsies. Knowledge on these channels in acquired focal epilepsy, especially in mesial temporal lobe epilepsy (mTLE), however, is scarce. Here, we used the rat pilocarpine model of drug-resistant mTLE to elucidate both expression and function by quantitative polymerase-chain reaction, immunohistochemistry, and electrophysiology, respectively. We found transcriptional downregulation of Kv7.2 and Kv7.3 as well as reduced Kv7.2 expression in epileptic CA1. Consequences were altered synaptic transmission, hyperexcitability which consisted of epileptiform afterpotentials, and increased susceptibility to acute GABAergic disinhibition. Importantly, blocking Kv7 channels with XE991 increased hyperexcitability in control tissue, but not in chronically epileptic tissue suggesting that the Kv7 deficit had precluded XE991 effects in this tissue. Conversely, XE991 resulted in comparable reduction of the paired-pulse ratio in both experimental groups implying preserved presynaptic Kv7.2 function of Schaffer collateral terminals. Consistent with Kv7.2/7.3 downregulation, the Kv7.3 channel opener β-hydroxybutyrate failed to mitigate hyperexcitability. Our findings demonstrate that compromised Kv7 function is not only relevant in genetic epilepsy, but also in acquired focal epilepsy. Moreover, they help explain reduced anti-seizure efficacy of Kv7 channel openers in drug-resistant epilepsy.
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Affiliation(s)
- Steffen Müller
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany
| | - Mareike Kartheus
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany
| | - Elisabeth Hendinger
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany
| | | | - Emma Schnell
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany
| | - Simone Rackow
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany
| | - Astrid Bertsche
- Department Neuropaediatrics, Hospital for Children and Adolescents, University Medicine Greifswald, Germany
| | - Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany; Center of Transdisciplinary Neurosciences Rostock (CTNR), University Medicine Rostock, Germany
| | - Timo Kirschstein
- Oscar Langendorff Institute of Physiology, University Medicine Rostock, Germany; Center of Transdisciplinary Neurosciences Rostock (CTNR), University Medicine Rostock, Germany.
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2
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Chen KJ, Yoshimura R, Edmundo CA, Truong TM, Civelli O, Alachkar A, Abbott GW. Behavioral and neuro-functional consequences of eliminating the KCNQ3 GABA binding site in mice. Front Mol Neurosci 2023; 16:1192628. [PMID: 37305551 PMCID: PMC10248464 DOI: 10.3389/fnmol.2023.1192628] [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: 03/23/2023] [Accepted: 05/09/2023] [Indexed: 06/13/2023] Open
Abstract
Voltage-gated potassium (Kv) channels formed by α subunits KCNQ2-5 are important in regulating neuronal excitability. We previously found that GABA directly binds to and activates channels containing KCNQ3, challenging the traditional understanding of inhibitory neurotransmission. To investigate the functional significance and behavioral role of this direct interaction, mice with a mutated KCNQ3 GABA binding site (Kcnq3-W266L) were generated and subjected to behavioral studies. Kcnq3-W266L mice exhibited distinctive behavioral phenotypes, of which reduced nociceptive and stress responses were profound and sex-specific. In female Kcnq3-W266L mice, the phenotype was shifted towards more nociceptive effects, while in male Kcnq3-W266L mice, it was shifted towards the stress response. In addition, female Kcnq3-W266L mice exhibited lower motor activity and reduced working spatial memory. The neuronal activity in the lateral habenula and visual cortex was altered in the female Kcnq3-W266L mice, suggesting that GABAergic activation of KCNQ3 in these regions may play a role in the regulation of the responses. Given the known overlap between the nociceptive and stress brain circuits, our data provide new insights into a sex-dependent role of KCNQ3 in regulating neural circuits involved in nociception and stress, via its GABA binding site. These findings identify new targets for effective treatments for neurological and psychiatric conditions such as pain and anxiety.
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Affiliation(s)
- Kiki J. Chen
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
| | - Ryan Yoshimura
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Clarissa Adriana Edmundo
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
| | - Tri Minh Truong
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
| | - Olivier Civelli
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
| | - Amal Alachkar
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, University of California, Irvine, Irvine, CA, United States
- UC Irvine Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA, United States
- Institute for Genomics and Bioinformatics, School of Information and Computer Sciences, University of California, Irvine, Irvine, CA, United States
| | - Geoffrey W. Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States
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3
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Falsaperla R, Marino SD, Salomone G, Madia F, Marino S, Tardino LG, Scalia B, Ruggieri M. Impressive efficacy of the ketogenic diet in a KCNQ2 encephalopathy infant: a case report and exhaustive literature review. Transl Pediatr 2023; 12:292-300. [PMID: 36891363 PMCID: PMC9986782 DOI: 10.21037/tp-22-258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 12/09/2022] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND KCNQ2 encephalopathy is characterized by neonatal-onset epilepsy and developmental impairment, due to "de novo" KCNQ2 pathogenic variants. According to literature data, sodium channel blocking agents appear to be the best treatment options for the disease. Reports describing the use of ketogenic diet (KD) in the KCNQ2 pediatric population are limited. The non-conservative amino acid substitution p.Ser122Leu in KCNQ2 is associated with a broad spectrum of inheritance modalities, clinical phenotypes and outcomes; no previous reports of the same variant treated with KD are available in literature. CASE DESCRIPTION We described a 22-month-old female with seizure onset on day 2 of life. At three months of age, she presented refractory status epilepticus (SE) that did not respond to midazolam and carbamazepine, which was added once a "de novo" p.Ser122Leu KCNQ2 variant was demonstrated. KD was the only treatment that led to cessation of seizures. The baby maintained seizures remission and achieved neurodevelopmental milestones. CONCLUSIONS To define an overt genotype-phenotype correlation for KCNQ2 pathogenic variants is a challenge; we propose the KD as a valuable treatment for refractory seizures and impaired neurodevelopment in infants harboring "de novo" mutations in the KCNQ2 gene.
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Affiliation(s)
- Raffaele Falsaperla
- Neonatology and Neonatal Intensive Care Unit, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy.,Unit of Pediatrics and Pediatric Emergency, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy
| | - Simona Domenica Marino
- Unit of Pediatrics and Pediatric Emergency, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy
| | | | - Francesca Madia
- Unit of Medical Genetics, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Silvia Marino
- Unit of Pediatrics and Pediatric Emergency, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy
| | - Lucia Giovanna Tardino
- Unit of Pediatrics and Pediatric Emergency, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy
| | - Bruna Scalia
- Neonatology and Neonatal Intensive Care Unit, Hospital Policlinico "G. Rodolico-San Marco", University of Catania, Catania, Italy
| | - Martino Ruggieri
- Unit of Rare Diseases of the Nervous System in Childhood, Section of Pediatrics and Child Neuropsychiatry, Department of Clinical and Experimental Medicine, University of Catania, Catania, Italy
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4
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Dyńka D, Kowalcze K, Paziewska A. The Role of Ketogenic Diet in the Treatment of Neurological Diseases. Nutrients 2022; 14:5003. [PMID: 36501033 PMCID: PMC9739023 DOI: 10.3390/nu14235003] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 11/20/2022] [Accepted: 11/21/2022] [Indexed: 11/26/2022] Open
Abstract
Over a hundred years of study on the favourable effect of ketogenic diets in the treatment of epilepsy have contributed to a long-lasting discussion on its potential influence on other neurological diseases. A significant increase in the number of scientific studies in that field has been currently observed. The aim of this paper is a widespread, thorough analysis of the available scientific evidence in respect of the role of the ketogenic diet in the therapy of neurological diseases such as: epilepsy, Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS) and migraine. A wide range of the mechanisms of action of the ketogenic diet has been demonstrated in neurological diseases, including, among other effects, its influence on the reduction in inflammatory conditions and the amount of reactive oxygen species (ROS), the restoration of the myelin sheath of the neurons, the formation and regeneration of mitochondria, neuronal metabolism, the provision of an alternative source of energy for neurons (ketone bodies), the reduction in glucose and insulin concentrations, the reduction in amyloid plaques, the induction of autophagy, the alleviation of microglia activation, the reduction in excessive neuronal activation, the modulation of intestinal microbiota, the expression of genes, dopamine production and the increase in glutamine conversion into GABA. The studies discussed (including randomised controlled studies), conducted in neurological patients, have stressed the effectiveness of the ketogenic diet in the treatment of epilepsy and have demonstrated its promising therapeutic potential in Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS) and migraine. A frequent advantage of the diet was demonstrated over non-ketogenic diets (in the control groups) in the therapy of neurological diseases, with simultaneous safety and feasibility when conducting the nutritional model.
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Affiliation(s)
- Damian Dyńka
- Institute of Health Sciences, Faculty of Medical and Health Sciences, Siedlce University of Natural Sciences and Humanities, 08-110 Siedlce, Poland
| | - Katarzyna Kowalcze
- Institute of Health Sciences, Faculty of Medical and Health Sciences, Siedlce University of Natural Sciences and Humanities, 08-110 Siedlce, Poland
| | - Agnieszka Paziewska
- Institute of Health Sciences, Faculty of Medical and Health Sciences, Siedlce University of Natural Sciences and Humanities, 08-110 Siedlce, Poland
- Department of Neuroendocrinology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland
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5
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Costa TJ, Linder BA, Hester S, Fontes M, Pernomian L, Wenceslau CF, Robinson AT, McCarthy CG. The janus face of ketone bodies in hypertension. J Hypertens 2022; 40:2111-2119. [PMID: 35969209 PMCID: PMC9733433 DOI: 10.1097/hjh.0000000000003243] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Hypertension is the most important risk factor for the development of terminal cardiovascular diseases, such as heart failure, chronic kidney disease, and atherosclerosis. Lifestyle interventions to lower blood pressure are generally desirable prior to initiating pharmaceutical drug treatments, which may have undesirable side effects. Ketogenic interventions are popular but the scientific literature supporting their efficacy is specific to certain interventions and outcomes in animal models and patient populations. For example, although caloric restriction has its own inherent difficulties (e.g. it requires high levels of motivation and adherence is difficult), it has unequivocally been associated with lowering blood pressure in hypertensive patients. On the other hand, the antihypertensive efficacy of ketogenic diets is inconclusive, and this is surprising, given that these diets have been largely helpful in mitigating metabolic syndrome and promoting longevity. It is possible that side effects associated with ketogenic diets (e.g. dyslipidemia) aggravate the hypertensive phenotype. However, given the recent data from our group, and others, reporting that the most abundant ketone body, β-hydroxybutyrate, can have positive effects on endothelial and vascular health, there is hope that ketone bodies can be harnessed as a therapeutic strategy to combat hypertension. Therefore, we conclude this review with a summary of the type and efficacy of ketone supplements. We propose that ketone supplements warrant investigation as low-dose antihypertensive therapy that decreases total peripheral resistance with minimal adverse side effects.
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Affiliation(s)
- Tiago J. Costa
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
| | | | - Seth Hester
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
| | - Milene Fontes
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
| | - Laena Pernomian
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
| | - Camilla F. Wenceslau
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
| | | | - Cameron G. McCarthy
- Cardiovascular Translational Research Center, University of South Carolina School of Medicine, Columbia, South Carolina
- Department of Cell Biology and Anatomy, University of South Carolina School of Medicine, Columbia, South Carolina
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6
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De La Rossa A, Laporte MH, Astori S, Marissal T, Montessuit S, Sheshadri P, Ramos-Fernández E, Mendez P, Khani A, Quairiaux C, Taylor EB, Rutter J, Nunes JM, Carleton A, Duchen MR, Sandi C, Martinou JC. Paradoxical neuronal hyperexcitability in a mouse model of mitochondrial pyruvate import deficiency. eLife 2022; 11:72595. [PMID: 35188099 PMCID: PMC8860443 DOI: 10.7554/elife.72595] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 01/21/2022] [Indexed: 11/22/2022] Open
Abstract
Neuronal excitation imposes a high demand of ATP in neurons. Most of the ATP derives primarily from pyruvate-mediated oxidative phosphorylation, a process that relies on import of pyruvate into mitochondria occuring exclusively via the mitochondrial pyruvate carrier (MPC). To investigate whether deficient oxidative phosphorylation impacts neuron excitability, we generated a mouse strain carrying a conditional deletion of MPC1, an essential subunit of the MPC, specifically in adult glutamatergic neurons. We found that, despite decreased levels of oxidative phosphorylation and decreased mitochondrial membrane potential in these excitatory neurons, mice were normal at rest. Surprisingly, in response to mild inhibition of GABA mediated synaptic activity, they rapidly developed severe seizures and died, whereas under similar conditions the behavior of control mice remained unchanged. We report that neurons with a deficient MPC were intrinsically hyperexcitable as a consequence of impaired calcium homeostasis, which reduced M-type potassium channel activity. Provision of ketone bodies restored energy status, calcium homeostasis and M-channel activity and attenuated seizures in animals fed a ketogenic diet. Our results provide an explanation for the seizures that frequently accompany a large number of neuropathologies, including cerebral ischemia and diverse mitochondriopathies, in which neurons experience an energy deficit.
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Affiliation(s)
| | | | - Simone Astori
- Laboratory of Behavioral Genetics, Ecole Polytechnique Fédérale de Lausanne
| | - Thomas Marissal
- Institut de Neurobiologie de la Méditerranée (INMED), Université d'Aix- Marseille
- Department of Basic Neuroscience, University of Geneva
| | | | - Preethi Sheshadri
- Department of Cell and Developmental Biology, University College London
| | | | | | - Abbas Khani
- Department of Basic Neuroscience, University of Geneva
| | | | - Eric B Taylor
- Department of Biochemistry and Fraternal Order of Eagles Diabetes Research Center, Carver College of Medicine, University of Iowa
| | - Jared Rutter
- Howard Hughes Medical Institute and Department of Biochemistry, University of Utah School of Medicine
| | | | - Alan Carleton
- Department of Basic Neuroscience, University of Geneva
| | - Michael R Duchen
- Department of Cell and Developmental Biology, University College London
| | - Carmen Sandi
- Laboratory of Behavioral Genetics, Ecole Polytechnique Fédérale de Lausanne
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7
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Zhang HXB, Heckman L, Niday Z, Jo S, Fujita A, Shim J, Pandey R, Al Jandal H, Jayakar S, Barrett LB, Smith J, Woolf CJ, Bean BP. Cannabidiol activates neuronal Kv7 channels. eLife 2022; 11:73246. [PMID: 35179483 PMCID: PMC8856652 DOI: 10.7554/elife.73246] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 02/09/2022] [Indexed: 01/10/2023] Open
Abstract
Cannabidiol (CBD), a chemical found in the Cannabis sativa plant, is a clinically effective antiepileptic drug whose mechanism of action is unknown. Using a fluorescence-based thallium flux assay, we performed a large-scale screen and found enhancement of flux through heterologously expressed human Kv7.2/7.3 channels by CBD. Patch-clamp recordings showed that CBD acts at submicromolar concentrations to shift the voltage dependence of Kv7.2/7.3 channels in the hyperpolarizing direction, producing a dramatic enhancement of current at voltages near –50 mV. CBD enhanced native M-current in mouse superior cervical ganglion starting at concentrations of 30 nM and also enhanced M-current in rat hippocampal neurons. The potent enhancement of Kv2/7.3 channels by CBD may contribute to its effectiveness as an antiepileptic drug by reducing neuronal hyperexcitability.
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Affiliation(s)
| | - Laurel Heckman
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Zachary Niday
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sooyeon Jo
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Akie Fujita
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Jaehoon Shim
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Roshan Pandey
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Hoor Al Jandal
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Selwyn Jayakar
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Lee B Barrett
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Jennifer Smith
- ICCB-Longwood Screening Facility and Department of Immunology, Harvard Medical School, Boston, United States
| | - Clifford J Woolf
- Department of Neurobiology, Harvard Medical School, Boston, United States.,F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Bruce P Bean
- Department of Neurobiology, Harvard Medical School, Boston, United States
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8
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Abstract
Since prehistory, human species have depended on plants for both food and medicine. Even in countries with ready access to modern medicines, alternative treatments are still highly regarded and commonly used. Unlike modern pharmaceuticals, many botanical medicines are in widespread use despite a lack of safety and efficacy data derived from controlled clinical trials and often unclear mechanisms of action. Contributing to this are the complex and undefined composition and likely multifactorial mechanisms of action and multiple targets of many botanical medicines. Here, we review the newfound importance of the ubiquitous KCNQ subfamily of voltage-gated potassium channels as targets for botanical medicines, including basil, capers, cilantro, lavender, fennel, chamomile, ginger, and Camellia, Sophora, and Mallotus species. We discuss the implications for the traditional use of these plants for disorders such as seizures, hypertension, and diabetes and the molecular mechanisms of plant secondary metabolite effects on KCNQ channels.
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Affiliation(s)
- Kaitlyn E Redford
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California 92697, USA;
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, California 92697, USA;
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9
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García-Rodríguez D, Giménez-Cassina A. Ketone Bodies in the Brain Beyond Fuel Metabolism: From Excitability to Gene Expression and Cell Signaling. Front Mol Neurosci 2021; 14:732120. [PMID: 34512261 PMCID: PMC8429829 DOI: 10.3389/fnmol.2021.732120] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 07/27/2021] [Indexed: 12/12/2022] Open
Abstract
Ketone bodies are metabolites that replace glucose as the main fuel of the brain in situations of glucose scarcity, including prolonged fasting, extenuating exercise, or pathological conditions such as diabetes. Beyond their role as an alternative fuel for the brain, the impact of ketone bodies on neuronal physiology has been highlighted by the use of the so-called “ketogenic diets,” which were proposed about a century ago to treat infantile seizures. These diets mimic fasting by reducing drastically the intake of carbohydrates and proteins and replacing them with fat, thus promoting ketogenesis. The fact that ketogenic diets have such a profound effect on epileptic seizures points to complex biological effects of ketone bodies in addition to their role as a source of ATP. In this review, we specifically focus on the ability of ketone bodies to regulate neuronal excitability and their effects on gene expression to respond to oxidative stress. Finally, we also discuss their capacity as signaling molecules in brain cells.
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Affiliation(s)
- Darío García-Rodríguez
- Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa" (CBMSO UAM-CSIC), Universidad Autónoma de Madrid, Madrid, Spain
| | - Alfredo Giménez-Cassina
- Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa" (CBMSO UAM-CSIC), Universidad Autónoma de Madrid, Madrid, Spain
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10
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Control of Biophysical and Pharmacological Properties of Potassium Channels by Ancillary Subunits. Handb Exp Pharmacol 2021; 267:445-480. [PMID: 34247280 DOI: 10.1007/164_2021_512] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Potassium channels facilitate and regulate physiological processes as diverse as electrical signaling, ion, solute and hormone secretion, fluid homeostasis, hearing, pain sensation, muscular contraction, and the heartbeat. Potassium channels are each formed by either a tetramer or dimer of pore-forming α subunits that co-assemble to create a multimer with a K+-selective pore that in most cases is capable of functioning as a discrete unit to pass K+ ions across the cell membrane. The reality in vivo, however, is that the potassium channel α subunit multimers co-assemble with ancillary subunits to serve specific physiological functions. The ancillary subunits impart specific physiological properties that are often required for a particular activity in vivo; in addition, ancillary subunit interaction often alters the pharmacology of the resultant complex. In this chapter the modes of action of ancillary subunits on K+ channel physiology and pharmacology are described and categorized into various mechanistic classes.
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11
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Kurata HT. Chemical regulation of Kv7 channels: Diverse scaffolds, sites, and mechanisms of action. J Gen Physiol 2020; 152:151830. [PMID: 32484852 PMCID: PMC7398145 DOI: 10.1085/jgp.202012598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kv7 channels are powerfully regulated by a wide variety of physiological and pharmacological signals. Larsson et al. describe the direct modulation of Kv7 channels by endocannabinoids and explore how combinations of Kv7 activators with distinct subtype specificities might lead to effective and selective drug cocktails.
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Affiliation(s)
- Harley T Kurata
- Department of Pharmacology, Alberta Diabetes Institute, University of Alberta, Edmonton, AB, Canada
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12
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Miceli F, Carotenuto L, Barrese V, Soldovieri MV, Heinzen EL, Mandel AM, Lippa N, Bier L, Goldstein DB, Cooper EC, Cilio MR, Taglialatela M, Sands TT. A Novel Kv7.3 Variant in the Voltage-Sensing S 4 Segment in a Family With Benign Neonatal Epilepsy: Functional Characterization and in vitro Rescue by β-Hydroxybutyrate. Front Physiol 2020; 11:1040. [PMID: 33013448 PMCID: PMC7498716 DOI: 10.3389/fphys.2020.01040] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 07/29/2020] [Indexed: 01/09/2023] Open
Abstract
Pathogenic variants in KCNQ2 and KCNQ3, paralogous genes encoding Kv7.2 and Kv7.3 voltage-gated K+ channel subunits, are responsible for early-onset developmental/epileptic disorders characterized by heterogeneous clinical phenotypes ranging from benign familial neonatal epilepsy (BFNE) to early-onset developmental and epileptic encephalopathy (DEE). KCNQ2 variants account for the majority of pedigrees with BFNE and KCNQ3 variants are responsible for a much smaller subgroup, but the reasons for this imbalance remain unclear. Analysis of additional pedigrees is needed to further clarify the nature of this genetic heterogeneity and to improve prediction of pathogenicity for novel variants. We identified a BFNE family with two siblings and a parent affected. Exome sequencing on samples from both parents and siblings revealed a novel KCNQ3 variant (c.719T>G; p.M240R), segregating in the three affected individuals. The M240 residue is conserved among human Kv7.2-5 and lies between the two arginines (R5 and R6) closest to the intracellular side of the voltage-sensing S4 transmembrane segment. Whole cell patch-clamp recordings in Chinese hamster ovary (CHO) cells revealed that homomeric Kv7.3 M240R channels were not functional, whereas heteromeric channels incorporating Kv7.3 M240R mutant subunits with Kv7.2 and Kv7.3 displayed a depolarizing shift of about 10 mV in activation gating. Molecular modeling results suggested that the M240R substitution preferentially stabilized the resting state and possibly destabilized the activated state of the Kv7.3 subunits, a result consistent with functional data. Exposure to β-hydroxybutyrate (BHB), a ketone body generated during the ketogenic diet (KD), reversed channel dysfunction induced by the M240R variant. In conclusion, we describe the first missense loss-of-function (LoF) pathogenic variant within the S4 segment of Kv7.3 identified in patients with BFNE. Studied under conditions mimicking heterozygosity, the M240R variant mainly affects the voltage sensitivity, in contrast to previously analyzed BFNE Kv7.3 variants that reduce current density. Our pharmacological results provide a rationale for the use of KD in patients carrying LoF variants in Kv7.2 or Kv7.3 subunits.
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Affiliation(s)
- Francesco Miceli
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Lidia Carotenuto
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | - Vincenzo Barrese
- Department of Neuroscience, University of Naples "Federico II", Naples, Italy
| | | | - Erin L Heinzen
- Eshelman School of Pharmacy, Division of Pharmacotherapy and Experimental Therapeutics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.,Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Arthur M Mandel
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States
| | - Natalie Lippa
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Louise Bier
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - David B Goldstein
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States
| | - Edward C Cooper
- Departments of Neurology, Neuroscience, and Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Maria Roberta Cilio
- Department of Pediatrics and Institute of Experimental and Clinical Research, Cliniques universitaires Saint-Luc, Université catholique de Louvain, Brussels, Belgium
| | | | - Tristan T Sands
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY, United States.,Department of Neurology, Columbia University Irving Medical Center, New York, NY, United States
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Redford KE, Abbott GW. The ubiquitous flavonoid quercetin is an atypical KCNQ potassium channel activator. Commun Biol 2020; 3:356. [PMID: 32641720 PMCID: PMC7343821 DOI: 10.1038/s42003-020-1089-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Accepted: 06/18/2020] [Indexed: 12/11/2022] Open
Abstract
Many commonly consumed plants are used as folk medicines, often with unclear molecular mechanisms. Recent studies uncovered the ubiquitous and influential KCNQ family of voltage-gated potassium (Kv) channels as a therapeutic target for several medicinal plant compounds. Capers - immature flower buds of Capparis spinosa - have been consumed for food and medicinal purposes for millennia. Here, we show that caper extract hyperpolarizes cells expressing KCNQ1 or KCNQ2/3 Kv channels. Capers are the richest known natural source of quercetin, the most consumed dietary flavonoid. Quercetin potentiated KCNQ1/KCNE1, KCNQ2/3 and KCNQ4 currents but, unusually, not KCNQ5. Strikingly, quercetin augmented both activation and inactivation of KCNQ1, via a unique KCNQ activation mechanism involving sites atop the voltage sensor and in the pore. The findings uncover a novel potential molecular basis for therapeutic effects of quercetin-rich foods and a new chemical space for atypical modes of KCNQ channel modulation. Kaitlyn E. Redford and Geoffrey W. Abbott show that quercetin, a flavonoid highly expressed in capers, potentiates KCNQ currents to varying degrees depending on the subunit composition of the channel complex. By combining in silico docking, mutagenesis, and electrophysiology they show that this flavonoid can bind KCNQ channels atop the voltage sensor and within the pore module, highlighting an atypical mode of channel modulation.
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Affiliation(s)
- Kaitlyn E Redford
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA.
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Abbott GW. KCNQs: Ligand- and Voltage-Gated Potassium Channels. Front Physiol 2020; 11:583. [PMID: 32655402 PMCID: PMC7324551 DOI: 10.3389/fphys.2020.00583] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 05/11/2020] [Indexed: 12/26/2022] Open
Abstract
Voltage-gated potassium (Kv) channels in the KCNQ (Kv7) family are essential features of a broad range of excitable and non-excitable cell types and are found in organisms ranging from Hydra vulgaris to Homo sapiens. Although they are firmly in the superfamily of S4 domain-bearing voltage-sensing ion channels, KCNQ channels are highly sensitive to a range of endogenous and exogenous small molecules that act directly on the pore, the voltage-sensing domain, or the interface between the two. The focus of this review is regulation of KCNQs by direct binding of neurotransmitters and metabolites from both animals and plants and the role of the latter in the effects of plants consumed for food and as traditional folk medicines. The conceptual question arises: Are KCNQs voltage-gated channels that are also sensitive to ligands or ligand-gated channels that are also sensitive to voltage?
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Affiliation(s)
- Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, Irvine, CA, United States
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15
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Manville RW, Abbott GW. Potassium channels act as chemosensors for solute transporters. Commun Biol 2020; 3:90. [PMID: 32111967 PMCID: PMC7048750 DOI: 10.1038/s42003-020-0820-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/06/2020] [Indexed: 01/27/2023] Open
Abstract
Potassium channels form physical complexes with solute transporters in vivo, yet little is known about their range of possible signaling modalities and the underlying mechanisms. The KCNQ2/3 potassium channel, which generates neuronal M-current, is voltage-gated and its activity is also stimulated by binding of various small molecules. KCNQ2/3 forms reciprocally regulating complexes with sodium-coupled myo-inositol transporters (SMITs) in mammalian neurons. Here, we report that the neurotransmitter γ-aminobutyric acid (GABA) and other small molecules directly regulate myo-inositol transport in rat dorsal root ganglia, and by human SMIT1-KCNQ2/3 complexes in vitro, by inducing a distinct KCNQ2/3 pore conformation. Reciprocally, SMIT1 tunes KCNQ2/3 sensing of GABA and related metabolites. Ion permeation and mutagenesis studies suggest that SMIT1 and GABA similarly alter KCNQ2/3 pore conformation but via different KCNQ subunits and molecular mechanisms. KCNQ channels therefore act as chemosensors to enable co-assembled myo-inositol transporters to respond to diverse stimuli including neurotransmitters, metabolites and drugs.
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Affiliation(s)
- Rίan W Manville
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA
| | - Geoffrey W Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, USA.
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