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Lee HM, Yoon SH, Kim MG, Hahn SJ, Choi BH. Effects of rosiglitazone, an antidiabetic drug, on Kv3.1 channels. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2023; 27:95-103. [PMID: 36575937 PMCID: PMC9806636 DOI: 10.4196/kjpp.2023.27.1.95] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/20/2022] [Accepted: 10/22/2022] [Indexed: 12/29/2022]
Abstract
Rosiglitazone is a thiazolidinedione-class antidiabetic drug that reduces blood glucose and glycated hemoglobin levels. We here investigated the interaction of rosiglitazone with Kv3.1 expressed in Chinese hamster ovary cells using the whole-cell patch-clamp technique. Rosiglitazone rapidly and reversibly inhibited Kv3.1 currents in a concentration-dependent manner (IC50 = 29.8 μM) and accelerated the decay of Kv3.1 currents without modifying the activation kinetics. The rosiglitazone-mediated inhibition of Kv3.1 channels increased steeply in a sigmoidal pattern over the voltage range of -20 to +30 mV, whereas it was voltage-independent in the voltage range above +30 mV, where the channels were fully activated. The deactivation of Kv3.1 current, measured along with tail currents, was also slowed by the drug. In addition, the steady-state inactivation curve of Kv3.1 by rosiglitazone shifts to a negative potential without significant change in the slope value. All the results with the use dependence of the rosiglitazone-mediated blockade suggest that rosiglitazone acts on Kv3.1 channels as an open channel blocker.
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Affiliation(s)
- Hyang Mi Lee
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Seong Han Yoon
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Min-Gul Kim
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea
| | - Sang June Hahn
- Department of Physiology, Medical Research Center, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea
| | - Bok Hee Choi
- Department of Pharmacology, Institute for Medical Sciences, Jeonbuk National University Medical School, Jeonju 54097, Korea,Correspondence Bok Hee Choi, E-mail:
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Li L, Liu Z, Yang H, Li Y, Zeng Q, Chen L, Liu Y, Chen Y, Zhu F, Cao D, Hu J, Shen X. Investigation of novel de novo KCNC2 variants causing severe developmental and early-onset epileptic encephalopathy. Seizure 2022; 101:218-224. [PMID: 36087422 DOI: 10.1016/j.seizure.2022.09.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 09/01/2022] [Accepted: 09/03/2022] [Indexed: 10/14/2022] Open
Abstract
Purpose The voltage-gated potassium channel Kv3.2, encoded by KCNC2, facilitates fast-spiking GABAergic interneurons to fire action potentials at high frequencies. It is pivotal to maintaining excitation/inhibition balance in mammalian brains. This study identified two novel de novo KCNC2 variants, p.Pro470Ser (P470S) and p.Phe382Leu (F382L), in patients with early onset developmental and epileptic encephalopathy (DEE). Methods To examine the molecular basis of DEE, we studied the functional characteristics of variant channels using patch-clamp techniques and computational modeling. Results Whole-cell patch clamp recordings from infected HEK293 cells revealed that channel activation and deactivation kinetics strongly decreased in both Kv3.2 P470S and F382L variant channels. This decrease also occurred in Kv3.2 p.Val471Leu (V471L) channels, known to be associated with DEE. In addition, Kv3.2 F382L and V471L variants exhibited a significant increase in channel conductance and a ∼20 mV negative shift in the threshold for voltage-dependent activation. Simulations of model GABAergic interneurons revealed that all variants decreased neuronal firing frequency. Thus, the variants' net loss-of-function effects disinhibited neural networks. Conclusion Our findings provide compelling evidence supporting the role of KCNC2 as a disease-causing gene in human neurodevelopmental delay and epilepsy.
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Affiliation(s)
- Lin Li
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Zili Liu
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China
| | - Haiyang Yang
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China; Guangdong Provincial Key Laboratory of Brain Connectome and Behavior, CAS Center for Excellence in Brain Science and Intelligence Technology, Shenzhen, Guangdong 518055, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Li
- University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, CAS, Beijing 100101, China
| | - Qi Zeng
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Li Chen
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Yidi Liu
- Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Yan Chen
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Fengjun Zhu
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Dezhi Cao
- Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China; Department of Neurology, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China
| | - Jun Hu
- Department of Pediatrics, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, China.
| | - Xuefeng Shen
- The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China.
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Wang S, Yu Y, Wang X, Deng X, Ma J, Liu Z, Gu W, Sun D. Emerging evidence of genotype–phenotype associations of developmental and epileptic encephalopathy due to KCNC2 mutation: Identification of novel R405G. Front Mol Neurosci 2022; 15:950255. [PMID: 36090251 PMCID: PMC9453199 DOI: 10.3389/fnmol.2022.950255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 07/20/2022] [Indexed: 11/13/2022] Open
Abstract
Developmental and epileptic encephalopathies (DEEs) have high genetic heterogeneity, and DEE due to the potassium voltage-gated channel subfamily C member 2 (KCNC2) variant remains poorly understood, given the scarcity of related case studies. We report on two unrelated Chinese patients, an 11-year-old boy and a 5-year-old girl, diagnosed with global developmental delay (GDD), intellectual disability (ID), and focal impaired awareness seizure characterized by generalized spike and wave complexes on electroencephalogram (EEG) in the absence of significant brain lesions. Whole-exome sequencing (WES) and electrophysiological analysis were performed to detect genetic variants and evaluate functional changes of the mutant KCNC2, respectively. Importantly, we identified a novel gain-of-function KCNC2 variant, R405G, in both patients. Previously reported variants, V471L, R351K, T437A, and T437N, and novel R405G were found in multiple unrelated patients with DEE, showing consistent genotype–phenotype associations. These findings emphasize that the KCNC2 gene is causative for DEE and facilitates treatment and prognosis in patients with DEE due to KCNC2 mutations.
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Affiliation(s)
- Sumei Wang
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yejing Yu
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xu Wang
- Department of Neurology, Changchun Children’s Hospital, Changchun, China
| | - Xiaolong Deng
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jiehui Ma
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhisheng Liu
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Weiyue Gu
- Chigene (Beijing) Translational Medical Research Center Co. Ltd., Beijing, China
| | - Dan Sun
- Department of Pediatric Neurology, Wuhan Children’s Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- *Correspondence: Dan Sun,
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Rydzanicz M, Zwoliński P, Gasperowicz P, Pollak A, Kostrzewa G, Walczak A, Konarzewska M, Płoski R. A recurrent de novo variant supports KCNC2 involvement in the pathogenesis of developmental and epileptic encephalopathy. Am J Med Genet A 2021; 185:3384-3389. [PMID: 34448338 DOI: 10.1002/ajmg.a.62455] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 07/12/2021] [Accepted: 07/22/2021] [Indexed: 11/11/2022]
Abstract
Developmental and epileptic encephalopathies (DEE) are a heterogenous group of conditions characterized by the co-occurrence of epilepsy and intellectual/developmental disability. Despite several known DEE-related genes, including these encoding ion channels, still many cases remain without molecular diagnosis. Here, we present a 2-year-old girl with severe DEE in whom whole exome sequencing revealed de novo p.(Val471Leu) variant in the KCNC2 encoding Kv3.2, a voltage-gated potassium channel. To the best of our knowledge, this is the third DEE case due to KCNC2 mutation. Our clinical and molecular findings, particularly the recurrence of p.(Val471Leu) in patient with similar clinical phenotype, further support KCNC2 as a novel DEE-associated gene.
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Affiliation(s)
| | | | - Piotr Gasperowicz
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Agnieszka Pollak
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Grażyna Kostrzewa
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | - Anna Walczak
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
| | | | - Rafał Płoski
- Department of Medical Genetics, Medical University of Warsaw, Warsaw, Poland
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5
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Zhou C, Liu M, Mei X, Li Q, Zhang W, Deng P, He Z, Xi Y, Tong T, Pi H, Lu Y, Chen C, Zhang L, Yu Z, Zhou Z, He M. Histone hypoacetylation contributes to neurotoxicity induced by chronic nickel exposure in vivo and in vitro. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 783:147014. [PMID: 34088129 DOI: 10.1016/j.scitotenv.2021.147014] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Revised: 04/04/2021] [Accepted: 04/04/2021] [Indexed: 06/12/2023]
Abstract
Nickel (Ni) is a heavy metal that is both an environmental pollutant and a threat to human health. However, the effects of Ni on the central nervous system in susceptible populations have not been well established. In the present study, the neurotoxicity of Ni and its underlying mechanism were investigated in vivo and in vitro. Ni exposure through drinking water (10 mg Ni/L, 12 weeks) caused learning and memory impairment in mice. Reduced dendrite complexity was observed in both Ni-exposed mouse hippocampi and Ni-treated (200 μM, 72 h) primary cultured hippocampal neurons. The levels of histone acetylation, especially at histone H3 lysine 9 (H3K9ac), were reduced in Ni-exposed mouse hippocampi and cultured neurons. RNA sequencing and chromatin immunoprecipitation (ChIP) sequencing analyses revealed that H3K9ac-modulated gene expression were downregulated. Treatment with sodium butyrate, a histone deacetylase inhibitor, attenuated Ni-induced H3K9 hypoacetylation, neural gene downregulation and dendrite complexity reduction in cultured neurons. Sodium butyrate also restored Ni-induced memory impairment in mice. These results indicate that Ni-induced H3K9 hypoacetylation may be a contributor to the neurotoxicity of Ni. The finding that Ni disturbs histone acetylation in the nervous system may provide new insight into the health risk of chronic Ni exposure.
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Affiliation(s)
- Chao Zhou
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Mengyu Liu
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China; Department of Medical Laboratory, General Hospital of the Central Theater Command of the Chinese People's Liberation Army, 430070 Wuhan, People's Republic of China
| | - Xiang Mei
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Qian Li
- Department of Otolaryngology Head and Neck Surgery, Xinqiao Hospital, Army Medical University, 400037 Chongqing, People's Republic of China
| | - Wenjuan Zhang
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Ping Deng
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Zhixin He
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Yu Xi
- Department of Environmental Medicine, School of Public Health, Department of Emergency Medicine, First Affiliated Hospital, School of Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Tong Tong
- Department of Environmental Medicine, School of Public Health, Department of Emergency Medicine, First Affiliated Hospital, School of Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China
| | - Huifeng Pi
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Yonghui Lu
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Chunhai Chen
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Lei Zhang
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China
| | - Zhengping Yu
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China.
| | - Zhou Zhou
- Department of Environmental Medicine, School of Public Health, Department of Emergency Medicine, First Affiliated Hospital, School of Medicine, Zhejiang University, 310058 Hangzhou, People's Republic of China.
| | - Mindi He
- Department of Occupational Health, Army Medical University, 400038 Chongqing, People's Republic of China.
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Nikitin ES, Vinogradova LV. Potassium channels as prominent targets and tools for the treatment of epilepsy. Expert Opin Ther Targets 2021; 25:223-235. [PMID: 33754930 DOI: 10.1080/14728222.2021.1908263] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
INTRODUCTION K+ channels are of great interest to epilepsy research as mutations in their genes are found in humans with inherited epilepsy. At the level of cellular physiology, K+ channels control neuronal intrinsic excitability and are the main contributors to membrane repolarization of active neurons. Recently, a genetically modified voltage-dependent K+ channel has been patented as a remedy for epileptic seizures. AREAS COVERED We review the role of potassium channels in excitability, clinical and experimental evidence for the association of potassium channelopathies with epilepsy, the targeting of K+ channels by drugs, and perspectives of gene therapy in epilepsy with the expression of extra K+ channels in the brain. EXPERT OPINION Control over K+ conductance is of great potential benefit for the treatment of epilepsy. Nowadays, gene therapy affecting K+ channels is one of the most promising approaches to treat pharmacoresistant focal epilepsy.
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Affiliation(s)
- E S Nikitin
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia
| | - L V Vinogradova
- Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, Russia
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7
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Rademacher A, Schwarz N, Seiffert S, Pendziwiat M, Rohr A, van Baalen A, Helbig I, Weber Y, Muhle H. Whole-Exome Sequencing in NF1-Related West Syndrome Leads to the Identification of KCNC2 as a Novel Candidate Gene for Epilepsy. Neuropediatrics 2020; 51:368-372. [PMID: 32392612 DOI: 10.1055/s-0040-1710524] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Patients with neurofibromatosis type 1 (NF1) have an increased risk for West syndrome (WS), but the underlying mechanisms linking NF1 and WS are unknown. In contrast to other neurocutaneous syndromes, intracerebral abnormalities explaining the course of infantile spasms (IS) are often absent and the seizure outcome is usually favorable. Several studies have investigated a potential genotype-phenotype correlation between NF1 and seizure susceptibility, but an association was not identified. Therefore, we identified three patients with NF1-related WS (NF1-WS) in a cohort of 51 NF1 patients and performed whole-exome sequencing (WES) to identify genetic modifiers. In two NF1 patients with WS and good seizure outcome, we did not identify variants in epilepsy-related genes. However, in a single patient with NF1-WS and transition to drug-resistant epilepsy, we identified a de novo variant in KCNC2 (c.G499T, p.D167Y) coding for Kv3.2 as a previously undescribed potassium channel to be correlated to epilepsy. Electrophysiological studies of the identified KCNC2 variant demonstrated both a strong loss-of-function effect for the current amplitude and a gain-of-function effect for the channel activation recommending a complex network effect. These results suggest that systematic genetic analysis for potentially secondary genetic etiologies in NF1 patients and severe epilepsy presentations should be done.
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Affiliation(s)
- Annika Rademacher
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Niklas Schwarz
- Department of Neurology and Epileptology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Simone Seiffert
- Department of Neurology and Epileptology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Manuela Pendziwiat
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Axel Rohr
- Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany.,Vancouver General Hospital, Vancouver, British Columbia, Canada
| | - Andreas van Baalen
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany
| | - Ingo Helbig
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany.,Children's Hospital of Philadelphia and Perelman School of Medicine University of Pennsylvania, Philadelphia, Pennsylvania, United States
| | - Yvonne Weber
- Department of Neurology and Epileptology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Department of Epileptology and Neurology, University of Aachen, Aachen, Germany
| | - Hiltrud Muhle
- Department of Neuropediatrics, University Medical Center Schleswig-Holstein, Christian-Albrechts University of Kiel, Kiel, Germany
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8
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Vetri L, Calì F, Vinci M, Amato C, Roccella M, Granata T, Freri E, Solazzi R, Romano V, Elia M. A de novo heterozygous mutation in KCNC2 gene implicated in severe developmental and epileptic encephalopathy. Eur J Med Genet 2020; 63:103848. [DOI: 10.1016/j.ejmg.2020.103848] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Revised: 12/15/2019] [Accepted: 01/12/2020] [Indexed: 12/11/2022]
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9
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Tai YS, Yang SC, Hsieh YC, Huang YB, Wu PC, Tsai MJ, Tsai YH, Lin MW. A Novel Model for Studying Voltage-Gated Ion Channel Gene Expression during Reversible Ischemic Stroke. Int J Med Sci 2019; 16:60-67. [PMID: 30662329 PMCID: PMC6332493 DOI: 10.7150/ijms.27442] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 10/31/2018] [Indexed: 12/21/2022] Open
Abstract
The dysfunction of voltage-gated ion channels contributes to the pathology of ischemic stroke. In this study, we developed rat models of transient ischemic attack (TIA) and reversible ischemic neurological deficit (RIND) that was induced via the injection of artificial embolic particles during full consciousness, that allow us to monitor the neurologic deficit and positron emission tomography (PET) scans in real-time. We then evaluated the infarction volume of brain tissue was confirmed by 2,3,5-triphenyl tetrazolium chloride (TTC) staining, and gene expressions were evaluated by quantitative real-time PCR (qPCR). We found that rats with TIA or RIND exhibited neurological deficits as determined by negative TTC and PET findings. However, the expression of voltage-gated sodium channels in the hippocampus was significantly up-regulated in the qPCR array study. Furthermore, an altered expression of sodium channel β-subunits and potassium channels, were observed in RIND compared to TIA groups. In conclusion, to our knowledge, this is the first report of the successful evaluation of voltage-gated ion channel gene expression in TIA and RIND animal models. This model will aid future studies in investigating pathophysiological mechanisms, and in developing new therapeutic compounds for the treatment of TIA and RIND.
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Affiliation(s)
- Yun-Shen Tai
- Department of Surgery, E-Da Hospital, Kaohsiung, Taiwan
| | - Shih-Chieh Yang
- Department of Orthopedic Surgery, E-Da Hospital, Kaohsiung, Taiwan
| | - Yi-Chun Hsieh
- Department of Anesthesiology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Yaw-Bin Huang
- School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan.,Center for Stem Cell Research, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Pao-Chu Wu
- School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ming-Jun Tsai
- Department of Neurology, China Medical University Hospital, Taichung, Taiwan.,School of Medicine, China Medical University, Taichung, Taiwan.,Department of Neurology, China Medical University, An-Nan Hospital, Tainan, Taiwan
| | - Yi-Hung Tsai
- School of Pharmacy, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Ming-Wei Lin
- Center for Stem Cell Research, Kaohsiung Medical University, Kaohsiung, Taiwan.,Department of Medical Research, E-Da Hospital/ E-Da Cancer Hospital, Kaohsiung, Taiwan
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10
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Kaczmarek LK, Zhang Y. Kv3 Channels: Enablers of Rapid Firing, Neurotransmitter Release, and Neuronal Endurance. Physiol Rev 2017; 97:1431-1468. [PMID: 28904001 PMCID: PMC6151494 DOI: 10.1152/physrev.00002.2017] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 04/24/2017] [Accepted: 05/05/2017] [Indexed: 12/11/2022] Open
Abstract
The intrinsic electrical characteristics of different types of neurons are shaped by the K+ channels they express. From among the more than 70 different K+ channel genes expressed in neurons, Kv3 family voltage-dependent K+ channels are uniquely associated with the ability of certain neurons to fire action potentials and to release neurotransmitter at high rates of up to 1,000 Hz. In general, the four Kv3 channels Kv3.1-Kv3.4 share the property of activating and deactivating rapidly at potentials more positive than other channels. Each Kv3 channel gene can generate multiple protein isoforms, which contribute to the high-frequency firing of neurons such as auditory brain stem neurons, fast-spiking GABAergic interneurons, and Purkinje cells of the cerebellum, and to regulation of neurotransmitter release at the terminals of many neurons. The different Kv3 channels have unique expression patterns and biophysical properties and are regulated in different ways by protein kinases. In this review, we cover the function, localization, and modulation of Kv3 channels and describe how levels and properties of the channels are altered by changes in ongoing neuronal activity. We also cover how the protein-protein interaction of these channels with other proteins affects neuronal functions, and how mutations or abnormal regulation of Kv3 channels are associated with neurological disorders such as ataxias, epilepsies, schizophrenia, and Alzheimer's disease.
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Affiliation(s)
- Leonard K Kaczmarek
- Departments of Pharmacology and of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
| | - Yalan Zhang
- Departments of Pharmacology and of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut
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11
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Wang B, Ke W, Guang J, Chen G, Yin L, Deng S, He Q, Liu Y, He T, Zheng R, Jiang Y, Zhang X, Li T, Luan G, Lu HD, Zhang M, Zhang X, Shu Y. Firing Frequency Maxima of Fast-Spiking Neurons in Human, Monkey, and Mouse Neocortex. Front Cell Neurosci 2016; 10:239. [PMID: 27803650 PMCID: PMC5067378 DOI: 10.3389/fncel.2016.00239] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 09/30/2016] [Indexed: 12/13/2022] Open
Abstract
Cortical fast-spiking (FS) neurons generate high-frequency action potentials (APs) without apparent frequency accommodation, thus providing fast and precise inhibition. However, the maximal firing frequency that they can reach, particularly in primate neocortex, remains unclear. Here, by recording in human, monkey, and mouse neocortical slices, we revealed that FS neurons in human association cortices (mostly temporal) could generate APs at a maximal mean frequency (Fmean) of 338 Hz and a maximal instantaneous frequency (Finst) of 453 Hz, and they increase with age. The maximal firing frequency of FS neurons in the association cortices (frontal and temporal) of monkey was even higher (Fmean 450 Hz, Finst 611 Hz), whereas in the association cortex (entorhinal) of mouse it was much lower (Fmean 215 Hz, Finst 342 Hz). Moreover, FS neurons in mouse primary visual cortex (V1) could fire at higher frequencies (Fmean 415 Hz, Finst 582 Hz) than those in association cortex. We further validated our in vitro data by examining spikes of putative FS neurons in behaving monkey and mouse. Together, our results demonstrate that the maximal firing frequency of FS neurons varies between species and cortical areas.
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Affiliation(s)
- Bo Wang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal UniversityBeijing, China; Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of SciencesShanghai, China
| | - Wei Ke
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Jing Guang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of Sciences Shanghai, China
| | - Guang Chen
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of Sciences Shanghai, China
| | - Luping Yin
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of Sciences Shanghai, China
| | - Suixin Deng
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Quansheng He
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Yaping Liu
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Ting He
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Rui Zheng
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of Sciences Shanghai, China
| | - Yanbo Jiang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, and University of Chinese Academy of Sciences Shanghai, China
| | - Xiaoxue Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Tianfu Li
- Department of Neurosurgery, Brain Institute, and Department of Neurology, Epilepsy Center, Beijing Sanbo Brain Hospital, Capital Medical University Beijing, China
| | - Guoming Luan
- Department of Neurosurgery, Brain Institute, and Department of Neurology, Epilepsy Center, Beijing Sanbo Brain Hospital, Capital Medical University Beijing, China
| | - Haidong D Lu
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Mingsha Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Xiaohui Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
| | - Yousheng Shu
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, The Collaborative Innovation Center for Brain Science, Beijing Normal University Beijing, China
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12
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Abstract
This review attempts to give a concise and up-to-date overview on the role of potassium channels in epilepsies. Their role can be defined from a genetic perspective, focusing on variants and de novo mutations identified in genetic studies or animal models with targeted, specific mutations in genes coding for a member of the large potassium channel family. In these genetic studies, a demonstrated functional link to hyperexcitability often remains elusive. However, their role can also be defined from a functional perspective, based on dynamic, aggravating, or adaptive transcriptional and posttranslational alterations. In these cases, it often remains elusive whether the alteration is causal or merely incidental. With ∼80 potassium channel types, of which ∼10% are known to be associated with epilepsies (in humans) or a seizure phenotype (in animals), if genetically mutated, a comprehensive review is a challenging endeavor. This goal may seem all the more ambitious once the data on posttranslational alterations, found both in human tissue from epilepsy patients and in chronic or acute animal models, are included. We therefore summarize the literature, and expand only on key findings, particularly regarding functional alterations found in patient brain tissue and chronic animal models.
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Affiliation(s)
- Rüdiger Köhling
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
| | - Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock, Rostock 18057, Germany
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13
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Abstract
In excitable cells, ion channels are frequently challenged by repetitive stimuli, and their responses shape cellular behavior by regulating the duration and termination of bursts of action potentials. We have investigated the behavior of Shaker family voltage-gated potassium (Kv) channels subjected to repetitive stimuli, with a particular focus on Kv1.2. Genetic deletion of this subunit results in complete mortality within 2 weeks of birth in mice, highlighting a critical physiological role for Kv1.2. Kv1.2 channels exhibit a unique property described previously as "prepulse potentiation," in which activation by a depolarizing step facilitates activation in a subsequent pulse. In this study, we demonstrate that this property enables Kv1.2 channels to exhibit use-dependent activation during trains of very brief depolarizations. Also, Kv subunits usually assemble into heteromeric channels in the central nervous system, generating diversity of function and sensitivity to signaling mechanisms. We demonstrate that other Kv1 channel types do not exhibit use-dependent activation, but this property is conferred in heteromeric channel complexes containing even a single Kv1.2 subunit. This regulatory mechanism is observed in mammalian cell lines as well as primary cultures of hippocampal neurons. Our findings illustrate that use-dependent activation is a unique property of Kv1.2 that persists in heteromeric channel complexes and may influence function of hippocampal neurons.
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14
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Wolfart J, Laker D. Homeostasis or channelopathy? Acquired cell type-specific ion channel changes in temporal lobe epilepsy and their antiepileptic potential. Front Physiol 2015; 6:168. [PMID: 26124723 PMCID: PMC4467176 DOI: 10.3389/fphys.2015.00168] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 05/19/2015] [Indexed: 01/16/2023] Open
Abstract
Neurons continuously adapt the expression and functionality of their ion channels. For example, exposed to chronic excitotoxicity, neurons homeostatically downscale their intrinsic excitability. In contrast, the “acquired channelopathy” hypothesis suggests that proepileptic channel characteristics develop during epilepsy. We review cell type-specific channel alterations under different epileptic conditions and discuss the potential of channels that undergo homeostatic adaptations, as targets for antiepileptic drugs (AEDs). Most of the relevant studies have been performed on temporal lobe epilepsy (TLE), a widespread AED-refractory, focal epilepsy. The TLE patients, who undergo epilepsy surgery, frequently display hippocampal sclerosis (HS), which is associated with degeneration of cornu ammonis subfield 1 pyramidal cells (CA1 PCs). Although the resected human tissue offers insights, controlled data largely stem from animal models simulating different aspects of TLE and other epilepsies. Most of the cell type-specific information is available for CA1 PCs and dentate gyrus granule cells (DG GCs). Between these two cell types, a dichotomy can be observed: while DG GCs acquire properties decreasing the intrinsic excitability (in TLE models and patients with HS), CA1 PCs develop channel characteristics increasing intrinsic excitability (in TLE models without HS only). However, thorough examination of data on these and other cell types reveals the coexistence of protective and permissive intrinsic plasticity within neurons. These mechanisms appear differentially regulated, depending on the cell type and seizure condition. Interestingly, the same channel molecules that are upregulated in DG GCs during HS-related TLE, appear as promising targets for future AEDs and gene therapies. Hence, GCs provide an example of homeostatic ion channel adaptation which can serve as a primer when designing novel anti-epileptic strategies.
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Affiliation(s)
- Jakob Wolfart
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
| | - Debora Laker
- Oscar Langendorff Institute of Physiology, University of Rostock Rostock, Germany
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15
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Lin CH, Yang CT, Tsai MC, Wu YT, MacDonald I, Wang ML, Wu CH, Leung YM, Chen YH. (±)3,4-Methylenedioxyamphetamine inhibits the TEA-sensitive K+ current in the hippocampal neuron and the Kv2.1 current expressed in H1355 cells. Neuropharmacology 2015; 89:100-12. [DOI: 10.1016/j.neuropharm.2014.09.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2013] [Revised: 08/20/2014] [Accepted: 09/04/2014] [Indexed: 10/24/2022]
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16
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Genetic association of KCNA5 and KCNJ3 polymorphisms in Korean children with epilepsy. Mol Cell Toxicol 2014. [DOI: 10.1007/s13273-014-0024-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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17
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Yasuda T, Cuny H, Adams DJ. Kv3.1 channels stimulate adult neural precursor cell proliferation and neuronal differentiation. J Physiol 2013; 591:2579-91. [PMID: 23478135 DOI: 10.1113/jphysiol.2012.249151] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Adult neural stem/precursor cells (NPCs) play a pivotal role in neuronal plasticity throughout life. Among ion channels identified in adult NPCs, voltage-gated delayed rectifier K(+) (KDR) channels are dominantly expressed. However, the KDR channel subtype and its physiological role are still undefined. We used real-time quantitative RT-PCR and gene knockdown techniques to identify a major functional KDR channel subtype in adult NPCs. Dominant mRNA expression of Kv3.1, a high voltage-gated KDR channel, was quantitatively confirmed. Kv3.1 gene knockdown with specific small interfering RNAs (siRNA) for Kv3.1 significantly inhibited Kv3.1 mRNA expression by 63.9% (P < 0.001) and KDR channel currents by 52.2% (P < 0.001). This indicates that Kv3.1 is the subtype responsible for producing KDR channel outward currents. Resting membrane properties, such as resting membrane potential, of NPCs were not affected by Kv3.1 expression. Kv3.1 knockdown with 300 nm siRNA inhibited NPC growth (increase in cell numbers) by 52.9% (P < 0.01). This inhibition was attributed to decreased cell proliferation, not increased cell apoptosis. We also established a convenient in vitro imaging assay system to evaluate NPC differentiation using NPCs from doublecortin-green fluorescent protein transgenic mice. Kv3.1 knockdown also significantly reduced neuronal differentiation by 31.4% (P < 0.01). We have demonstrated that Kv3.1 is a dominant functional KDR channel subtype expressed in adult NPCs and plays key roles in NPC proliferation and neuronal lineage commitment during differentiation.
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Affiliation(s)
- Takahiro Yasuda
- Center for Clinical Research, School of Medicine, Kobe University Hospital, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
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18
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He S, Shao LR, Rittase WB, Bausch SB. Increased Kv1 channel expression may contribute to decreased sIPSC frequency following chronic inhibition of NR2B-containing NMDAR. Neuropsychopharmacology 2012; 37:1338-56. [PMID: 22218089 PMCID: PMC3327840 DOI: 10.1038/npp.2011.320] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 10/21/2011] [Accepted: 11/29/2011] [Indexed: 12/20/2022]
Abstract
Numerous studies have documented the effects of chronic N-methyl-D-aspartate receptor (NMDAR) blockade on excitatory circuits, but the effects on inhibitory circuitry are not well studied. NR2A- and NR2B-containing NMDARs play differential roles in physiological processes, but the consequences of chronic NR2A- or NR2B-containing NMDAR inhibition on glutamatergic and GABAergic neurotransmission are unknown. We investigated altered GABAergic neurotransmission in dentate granule cells and interneurons following chronic treatment with the NR2B-selective antagonist, Ro25,6981, the NR2A-prefering antagonist, NVP-AAM077, or the non-subunit-selective NMDAR antagonist, D-APV, in organotypic hippocampal slice cultures. Electrophysiological recordings revealed large reductions in spontaneous inhibitory postsynaptic current (sIPSC) frequency in both granule cells and interneurons following chronic Ro25,6981 treatment, which was associated with minimally altered sIPSC amplitude, miniature inhibitory postsynaptic current (mIPSC) frequency, and mIPSC amplitude, suggesting diminished action potential-dependent GABA release. Chronic NVP-AAM077 or D-APV treatment had little effect on these measures. Reduced sIPSC frequency did not arise from downregulated GABA(A)R, altered excitatory or inhibitory drive to interneurons, altered interneuron membrane properties, increased failure rate, decreased action potential-dependent release probability, or mGluR/GABA(B) receptor modulation of GABA release. However, chronic Ro25,6981-mediated reductions in sIPSC frequency were occluded by the K+ channel blockers, dendrotoxin, margatoxin, and agitoxin, but not dendrotoxin-K or XE991. Immunohistochemistry also showed increased Kv1.2, Kv1.3, and Kv1.6 in the dentate molecular layer following chronic Ro25,6981 treatment. Our findings suggest that increased Kv1 channel expression/function contributed to diminished action potential-dependent GABA release following chronic NR2B-containing NMDAR inhibition and that these Kv1 channels may be heteromeric complexes containing Kv1.2, Kv1.3, and Kv1.6.
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Affiliation(s)
- Shuijin He
- Department of Pharmacology, Uniformed Services University School of Medicine, Bethesda, MD, USA
- Graduate Program in Neuroscience, Uniformed Services University School of Medicine, Bethesda, MD, USA
| | - Li-Rong Shao
- Department of Pharmacology, Uniformed Services University School of Medicine, Bethesda, MD, USA
| | - W Bradley Rittase
- Department of Pharmacology, Uniformed Services University School of Medicine, Bethesda, MD, USA
| | - Suzanne B Bausch
- Department of Pharmacology, Uniformed Services University School of Medicine, Bethesda, MD, USA
- Graduate Program in Neuroscience, Uniformed Services University School of Medicine, Bethesda, MD, USA
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19
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Lee SB, Oh YJ, Chung JK, Jeong JH, Lee SD, Park DK, Park KH, Ko JS, Kim DS. Altered PLCβ-1 expression in the gerbil hippocampal complex following spontaneous seizure. BMB Rep 2012; 44:566-71. [PMID: 21944248 DOI: 10.5483/bmbrep.2011.44.9.566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Although the phospholipase C (PLC)β-1 isoform is associated with spontaneous seizure and distinctively expressed in the telencephalon, the distribution of PLCβ-1 expression in the epileptic gerbil hippocampus remains controversial. Therefore, we determined whether PLCβ-1 is associated with spontaneous seizure in an animal model of genetic epilepsy. In the present study, PLCβ-1 immunoreactivity was down-regulated in seizure-sensitive (SS) gerbils more than in seizure-resistant (SR) gerbils. The expression of PLCβ-1 within calretinin (CR)- positive neurons was rarely detected within the dentate hilar region of SS gerbils. PLCβ-1 immunoreactivity in the hippocampus was significantly elevated as compared to that in pre-seizure SS gerbil 3 h post-ictal. These findings suggest that alterations in PLCβ-1 immunoreactivity in the SS gerbil hippocampus may be closely related to the epileptic state of the gerbil brain and transiently elevated PLCβ-1 protein levels following seizure episodes. Such alterations may be compensatory responses in the SS gerbil hippocampus.
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Affiliation(s)
- Saet-Byeol Lee
- Department of Anatomy, College of Medicine, Soonchunhyang University, Cheonan 330-090, Korea
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20
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Heo DH, Kang TC. The changes of ERG channel expression after administration of antiepileptic drugs in the hippocampus of epilepsy gerbil model. Neurosci Lett 2012; 507:27-32. [DOI: 10.1016/j.neulet.2011.11.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Revised: 11/25/2011] [Accepted: 11/26/2011] [Indexed: 10/14/2022]
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21
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Position-dependent attenuation by Kv1.6 of N-type inactivation of Kv1.4-containing channels. Biochem J 2011; 438:389-96. [PMID: 21352098 DOI: 10.1042/bj20102169] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Assembly of distinct α subunits of Kv1 (voltage-gated K(+) channels) into tetramers underlies the diversity of their outward currents in neurons. Kv1.4-containing channels normally exhibit N-type rapid inactivation, mediated through an NIB (N-terminal inactivation ball); this can be over-ridden if associated with a Kv1.6 α subunit, via its NIP (N-type inactivation prevention) domain. Herein, NIP function was shown to require positioning of Kv1.6 adjacent to the Kv1.4 subunit. Using a recently devised gene concatenation, heterotetrameric Kv1 channels were expressed as single-chain proteins on the plasmalemma of HEK (human embryonic kidney)-293 cells, so their constituents could be arranged in different positions. Placing the Kv1.4 and 1.6 genes together, followed by two copies of Kv1.2, yielded a K(+) current devoid of fast inactivation. Mutation of critical glutamates within the NIP endowed rapid inactivation. Moreover, separating Kv1.4 and 1.6 with a copy of Kv1.2 gave a fast-inactivating K(+) current with steady-state inactivation shifted to more negative potentials and exhibiting slower recovery, correlating with similar inactivation kinetics seen for Kv1.4-(1.2)(3). Alternatively, separating Kv1.4 and 1.6 with two copies of Kv1.2 yielded slow-inactivating currents, because in this concatamer Kv1.4 and 1.6 should be together. These findings also confirm that the gene concatenation can generate K(+) channels with α subunits in pre-determined positions.
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22
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Pacheco Otalora LF, Skinner F, Oliveira MS, Farrell B, Arshadmansab MF, Pandari T, Garcia I, Robles L, Rosas G, Mello CF, Ermolinsky BS, Garrido-Sanabria ER. Chronic deficit in the expression of voltage-gated potassium channel Kv3.4 subunit in the hippocampus of pilocarpine-treated epileptic rats. Brain Res 2010; 1368:308-16. [PMID: 20971086 DOI: 10.1016/j.brainres.2010.10.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 10/11/2010] [Accepted: 10/14/2010] [Indexed: 10/18/2022]
Abstract
Voltage gated K(+) channels (Kv) are a highly diverse group of channels critical in determining neuronal excitability. Deficits of Kv channel subunit expression and function have been implicated in the pathogenesis of epilepsy. In this study, we investigate whether the expression of the specific subunit Kv3.4 is affected during epileptogenesis following pilocarpine-induced status epilepticus. For this purpose, we used immunohistochemistry, Western blotting assays and comparative analysis of gene expression using TaqMan-based probes and delta-delta cycle threshold (ΔΔCT) method of quantitative real-time polymerase chain reaction (qPCR) technique in samples obtained from age-matched control and epileptic rats. A marked down-regulation of Kv3.4 immunoreactivity was detected in the stratum lucidum and hilus of dentate gyrus in areas corresponding to the mossy fiber system of chronically epileptic rats. Correspondingly, a 20% reduction of Kv3.4 protein levels was detected in the hippocampus of chronic epileptic rats. Real-time quantitative PCR analysis of gene expression revealed that a significant 33% reduction of transcripts for Kv3.4 (gene Kcnc4) occurred after 1 month of pilocarpine-induced status epilepticus and persisted during the chronic phase of the model. These data indicate a reduced expression of Kv3.4 channels at protein and transcript levels in the epileptic hippocampus. Down-regulation of Kv3.4 in mossy fibers may contribute to enhanced presynaptic excitability leading to recurrent seizures in the pilocarpine model of temporal lobe epilepsy.
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Affiliation(s)
- Luis F Pacheco Otalora
- Department of Biological Sciences at the University of Texas at Brownsville and Center for Biomedical Studies, 80 Fort Brown, Brownsville, TX 78520, USA
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