1
|
Andreyanov M, Heinrich R, Berlin S. Design of Ultrapotent Genetically Encoded Inhibitors of Kv4.2 for Gating Neural Plasticity. J Neurosci 2024; 44:e2295222023. [PMID: 38154956 PMCID: PMC10869153 DOI: 10.1523/jneurosci.2295-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 11/05/2023] [Accepted: 11/22/2023] [Indexed: 12/30/2023] Open
Abstract
The Kv4.2 potassium channel plays established roles in neuronal excitability, while also being implicated in plasticity. Current means to study the roles of Kv4.2 are limited, motivating us to design a genetically encoded membrane tethered Heteropodatoxin-2 (MetaPoda). We find that MetaPoda is an ultrapotent and selective gating-modifier of Kv4.2. We narrow its site of contact with the channel to two adjacent residues within the voltage sensitive domain (VSD) and, with docking simulations, suggest that the toxin binds the VSD from within the membrane. We also show that MetaPoda does not require an external linker of the channel for its activity. In neurons (obtained from female and male rat neonates), MetaPoda specifically, and potently, inhibits all Kv4 currents, leaving all other A-type currents unaffected. Inhibition of Kv4 in hippocampal neurons does not promote excessive excitability, as is expected from a simple potassium channel blocker. We do find that MetaPoda's prolonged expression (1 week) increases expression levels of the immediate early gene cFos and prevents potentiation. These findings argue for a major role of Kv4.2 in facilitating plasticity of hippocampal neurons. Lastly, we show that our engineering strategy is suitable for the swift engineering of another potent Kv4.2-selective membrane-tethered toxin, Phrixotoxin-1, denoted MetaPhix. Together, we provide two uniquely potent genetic tools to study Kv4.2 in neuronal excitability and plasticity.
Collapse
Affiliation(s)
- Michael Andreyanov
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| | - Ronit Heinrich
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| | - Shai Berlin
- Department of Neuroscience, Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa 3525433, Israel
| |
Collapse
|
2
|
McGann AM, Westerkamp GC, Chalasani A, Danzer CSK, Parkins EV, Rajathi V, Horn PS, Pedapati EV, Tiwari D, Danzer SC, Gross C. MiR-324-5p inhibition after intrahippocampal kainic acid-induced status epilepticus does not prevent epileptogenesis in mice. Front Neurol 2023; 14:1280606. [PMID: 38033777 PMCID: PMC10687438 DOI: 10.3389/fneur.2023.1280606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 10/20/2023] [Indexed: 12/02/2023] Open
Abstract
Background Acquired epilepsies are caused by an initial brain insult that is followed by epileptogenesis and finally the development of spontaneous recurrent seizures. The mechanisms underlying epileptogenesis are not fully understood. MicroRNAs regulate mRNA translation and stability and are frequently implicated in epilepsy. For example, antagonism of a specific microRNA, miR-324-5p, before brain insult and in a model of chronic epilepsy decreases seizure susceptibility and frequency, respectively. Here, we tested whether antagonism of miR-324-5p during epileptogenesis inhibits the development of epilepsy. Methods We used the intrahippocampal kainic acid (IHpKa) model to initiate epileptogenesis in male wild type C57BL/6 J mice aged 6-8 weeks. Twenty-four hours after IHpKa, we administered a miR-324-5p or scrambled control antagomir intracerebroventricularly and implanted cortical surface electrodes for EEG monitoring. EEG data was collected for 28 days and analyzed for seizure frequency and duration, interictal spike activity, and EEG power. Brains were collected for histological analysis. Results Histological analysis of brain tissue showed that IHpKa caused characteristic hippocampal damage in most mice regardless of treatment. Antagomir treatment did not affect latency to, frequency, or duration of spontaneous recurrent seizures or interictal spike activity but did alter the temporal development of frequency band-specific EEG power. Conclusion These results suggest that miR-324-5p inhibition during epileptogenesis induced by status epilepticus does not convey anti-epileptogenic effects despite having subtle effects on EEG frequency bands. Our results highlight the importance of timing of intervention across epilepsy development and suggest that miR-324-5p may act primarily as a proconvulsant rather than a pro-epileptogenic regulator.
Collapse
Affiliation(s)
- Amanda M. McGann
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Grace C. Westerkamp
- Division of Child and Adolescent Psychiatry, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Alisha Chalasani
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Cole S. K. Danzer
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Emma V. Parkins
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Valerine Rajathi
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
| | - Paul S. Horn
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Ernest V. Pedapati
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Division of Child and Adolescent Psychiatry, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Durgesh Tiwari
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Steve C. Danzer
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Division of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Anesthesia, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| | - Christina Gross
- Medical Scientist Training Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Neuroscience Graduate Program, University of Cincinnati College of Medicine, Cincinnati, OH, United States
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States
| |
Collapse
|
3
|
Frare C, Pitt SK, Hewett SJ. Sex- and age-dependent contribution of System x c- to cognitive, sensory, and social behaviors revealed by comprehensive behavioral analyses of System x c- null mice. Front Behav Neurosci 2023; 17:1238349. [PMID: 37649973 PMCID: PMC10462982 DOI: 10.3389/fnbeh.2023.1238349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Accepted: 07/31/2023] [Indexed: 09/01/2023] Open
Abstract
Background System xc- (Sxc-) is an important heteromeric amino acid cystine/glutamate exchanger that plays a pivotal role in the CNS by importing cystine into cells while exporting glutamate. Although certain behaviors have been identified as altered in Sxc- null mutant mice, our understanding of the comprehensive impact of Sxc- on behavior remains incomplete. Methods To address this gap, we compared motor, sensory and social behaviors of male and female mice in mice null for Sxc- (SLC7A11sut/sut) with wildtype littermates (SLC7A11+/+) in a comprehensive and systematic manner to determine effects of genotype, sex, age, and their potential interactions. Results Motor performance was not affected by loss of Sxc- in both males and females, although it was impacted negatively by age. Motor learning was specifically disrupted in female mice lacking Sxc- at both 2 and 6 months of age. Further, female SLC7A11sut/sut mice at both ages exhibited impaired sociability, but normal spatial and recognition memory, as well as sensorimotor gating. Finally, pronounced open-space anxiety was displayed by female SLC7A11sut/sut when they were young. In contrast, young SLC7A11sut/sut male mice demonstrated normal sociability, delayed spatial learning, increased open-space anxiety and heightened sensitivity to noise. As they aged, anxiety and noise sensitivity abated but hyperactivity emerged. Discussion We find that the behavioral phenotypes of female SLC7A11sut/sut are similar to those observed in mouse models of autism spectrum disorder, while behaviors of male SLC7A11sut/sut resemble those seen in mouse models of attention deficit hyperactivity disorder. These results underscore the need for further investigation of SLC7A11 in neurodevelopment. By expanding our understanding of the potential involvement of Sxc-, we may gain additional insights into the mechanisms underlying complex neurodevelopmental conditions.
Collapse
Affiliation(s)
| | | | - Sandra J. Hewett
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, NY, United States
| |
Collapse
|
4
|
Sun X, Lv Y, Lin J. The mechanism of sudden unexpected death in epilepsy: A mini review. Front Neurol 2023; 14:1137182. [PMID: 36815002 PMCID: PMC9939452 DOI: 10.3389/fneur.2023.1137182] [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: 01/04/2023] [Accepted: 01/20/2023] [Indexed: 02/08/2023] Open
Abstract
Sudden unexpected death in epilepsy (SUDEP) is defined as a sudden, unexpected, non-traumatic, non-drowning death in a person with epilepsy. SUDEP is generally considered to result from seizure-related cardiac dysfunction, respiratory depression, autonomic nervous dysfunction, or brain dysfunction. Frequency of generalized tonic clonic seizures (GTCS), prone posture, and refractory epilepsy are considered risk factors. SUDEP has also been associated with inherited cardiac ion channel disease and severe obstructive sleep apnea. Most previous studies of SUDEP mechanisms have focused on cardiac and respiratory dysfunction and imbalance of the neural regulatory system. Cardiac-related mechanisms include reduction in heart rate variability and prolongation of QT interval, which can lead to arrhythmias. Laryngospasm and amygdala activation may cause obstructive and central apnea, respectively. Neural mechanisms include impairment of 5-HT and adenosine neuromodulation. The research to date regarding molecular mechanisms of SUDEP is relatively limited. Most studies have focused on p-glycoprotein, catecholamines, potassium channels, and the renin-angiotensin system, all of which affect cardiac and respiratory function.
Collapse
Affiliation(s)
- Xinyi Sun
- School of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, China
| | - Yehui Lv
- School of Basic Medical Sciences, Shanghai University of Medicine and Health Sciences, Shanghai, China,Institute of Wound Prevention and Treatment, Shanghai University of Medicine and Health Sciences, Shanghai, China,*Correspondence: Yehui Lv ✉
| | - Jian Lin
- Institute of Wound Prevention and Treatment, Shanghai University of Medicine and Health Sciences, Shanghai, China,Chongming Hospital Affiliated to Shanghai University of Medicine and Health Sciences, Shanghai, China
| |
Collapse
|
5
|
Therapeutic Implications of microRNAs in Depressive Disorders: A Review. Int J Mol Sci 2022; 23:ijms232113530. [PMID: 36362315 PMCID: PMC9658840 DOI: 10.3390/ijms232113530] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/28/2022] [Accepted: 10/28/2022] [Indexed: 11/06/2022] Open
Abstract
MicroRNAs are hidden players in complex psychophysical phenomena such as depression and anxiety related disorders though the activation and deactivation of multiple proteins in signaling cascades. Depression is classified as a mood disorder and described as feelings of sadness, loss, or anger that interfere with a person’s everyday activities. In this review, we have focused on exploration of the significant role of miRNAs in depression by affecting associated target proteins (cellular and synaptic) and their signaling pathways which can be controlled by the attachment of miRNAs at transcriptional and translational levels. Moreover, miRNAs have potential role as biomarkers and may help to cure depression through involvement and interactions with multiple pharmacological and physiological therapies. Taken together, miRNAs might be considered as promising novel therapy targets themselves and may interfere with currently available antidepressant treatments.
Collapse
|
6
|
CUX2 deficiency causes facilitation of excitatory synaptic transmission onto hippocampus and increased seizure susceptibility to kainate. Sci Rep 2022; 12:6505. [PMID: 35581205 PMCID: PMC9114133 DOI: 10.1038/s41598-022-10715-w] [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: 12/02/2021] [Accepted: 04/11/2022] [Indexed: 01/19/2023] Open
Abstract
CUX2 gene encodes a transcription factor that controls neuronal proliferation, dendrite branching and synapse formation, locating at the epilepsy-associated chromosomal region 12q24 that we previously identified by a genome-wide association study (GWAS) in Japanese population. A CUX2 recurrent de novo variant p.E590K has been described in patients with rare epileptic encephalopathies and the gene is a candidate for the locus, however the mutation may not be enough to generate the genome-wide significance in the GWAS and whether CUX2 variants appear in other types of epilepsies and physiopathological mechanisms are remained to be investigated. Here in this study, we conducted targeted sequencings of CUX2, a paralog CUX1 and its short isoform CASP harboring a unique C-terminus on 271 Japanese patients with a variety of epilepsies, and found that multiple CUX2 missense variants, other than the p.E590K, and some CASP variants including a deletion, predominantly appeared in patients with temporal lobe epilepsy (TLE). The CUX2 variants showed abnormal localization in human cell culture analysis. While wild-type CUX2 enhances dendritic arborization in fly neurons, the effect was compromised by some of the variants. Cux2- and Casp-specific knockout mice both showed high susceptibility to kainate, increased excitatory cell number in the entorhinal cortex, and significant enhancement in glutamatergic synaptic transmission to the hippocampus. CASP and CUX2 proteins physiologically bound to each other and co-expressed in excitatory neurons in brain regions including the entorhinal cortex. These results suggest that CUX2 and CASP variants contribute to the TLE pathology through a facilitation of excitatory synaptic transmission from entorhinal cortex to hippocampus.
Collapse
|
7
|
Murphy JG, Gutzmann JJ, Lin L, Hu J, Petralia RS, Wang YX, Hoffman DA. R-type voltage-gated Ca 2+ channels mediate A-type K + current regulation of synaptic input in hippocampal dendrites. Cell Rep 2022; 38:110264. [PMID: 35045307 PMCID: PMC10496648 DOI: 10.1016/j.celrep.2021.110264] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 12/02/2021] [Accepted: 12/22/2021] [Indexed: 01/22/2023] Open
Abstract
The subthreshold voltage-gated transient K+ current (IA) carried by pore-forming Kv4.2 subunits regulates the propagation of synaptic input, dendritic excitability, and synaptic plasticity in CA1 pyramidal neuron dendrites of the hippocampus. We report that the Ca2+ channel subunit Cav2.3 regulates IA in this cell type. We initially identified Cav2.3 as a Kv4.2-interacting protein in a proteomic screen and we confirmed Cav2.3-Kv4.2 complex association using multiple techniques. Functionally, Cav2.3 Ca2+-entry increases Kv4.2-mediated whole-cell current due to an increase in Kv4.2 surface expression. Using pharmacology and Cav2.3 knockout mice, we show that Cav2.3 regulates the dendritic gradient of IA. Furthermore, the loss of Cav2.3 function leads to the enhancement of AMPA receptor-mediated synaptic currents and NMDA receptor-mediated spine Ca2+ influx. These results propose that Cav2.3 and Kv4.2 are integral constituents of an ion channel complex that affects synaptic function in the hippocampus.
Collapse
Affiliation(s)
- Jonathan G Murphy
- Molecular Neurophysiology and Biophysics Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jakob J Gutzmann
- Molecular Neurophysiology and Biophysics Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Lin Lin
- Molecular Neurophysiology and Biophysics Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jiahua Hu
- Molecular Neurophysiology and Biophysics Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ronald S Petralia
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ya-Xian Wang
- Advanced Imaging Core, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Dax A Hoffman
- Molecular Neurophysiology and Biophysics Section, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
8
|
Rayff da Silva P, do Nascimento Gonzaga TKS, Maia RE, Araújo da Silva B. Ionic Channels as Potential Targets for the Treatment of Autism Spectrum Disorder: A Review. Curr Neuropharmacol 2022; 20:1834-1849. [PMID: 34370640 PMCID: PMC9886809 DOI: 10.2174/1570159x19666210809102547] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/23/2021] [Accepted: 07/24/2021] [Indexed: 11/22/2022] Open
Abstract
Autism spectrum disorder (ASD) is a neurological condition that directly affects brain functions and can culminate in delayed intellectual development, problems in verbal communication, difficulties in social interaction, and stereotyped behaviors. Its etiology reveals a genetic basis that can be strongly influenced by socio-environmental factors. Ion channels controlled by ligand voltage-activated calcium, sodium, and potassium channels may play important roles in modulating sensory and cognitive responses, and their dysfunctions may be closely associated with neurodevelopmental disorders such as ASD. This is due to ionic flow, which is of paramount importance to maintaining physiological conditions in the central nervous system and triggers action potentials, gene expression, and cell signaling. However, since ASD is a multifactorial disease, treatment is directed only to secondary symptoms. Therefore, this research aims to gather evidence concerning the principal pathophysiological mechanisms involving ion channels in order to recognize their importance as therapeutic targets for the treatment of central and secondary ASD symptoms.
Collapse
Affiliation(s)
| | | | | | - Bagnólia Araújo da Silva
- Address correspondence to this author at the Postgraduate Program in Natural Synthetic and Bioactive Products, Heath Sciences Center, Federal University of Paraíba - Campus I, 58051-085, Via Ipê Amarelo, S/N, João Pessoa, Paraíba, Brazil; Tel: ++55-83-99352-5595; E-mail:
| |
Collapse
|
9
|
Sears SMS, Roberts SH, Hewett SJ. Hyperexcitability and brain morphological differences in mice lacking the cystine/glutamate antiporter, system x c. J Neurosci Res 2021; 99:3339-3353. [PMID: 34747522 DOI: 10.1002/jnr.24971] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 09/11/2021] [Accepted: 09/16/2021] [Indexed: 01/17/2023]
Abstract
System xc - (Sxc - ) is a heteromeric antiporter (L-cystine/L-glutamate exchanger) expressed predominately on astrocytes in the central nervous system. Its activity contributes importantly to the maintenance of the ambient extracellular glutamate levels, as well as, to cellular redox homeostasis. Since alterations in glutamate levels and redox modifications could cause structural changes, we analyzed gross regional morphology of thionin-stained brain sections and cellular and subcellular morphology of Golgi-Cox stained layer V pyramidal neurons in the primary motor cortex (PM1) of mice naturally null for SLC7A11 (SLC7A11sut/sut )-the gene that encodes the substrate specific light chain (xCT) for Sxc - . Intriguingly, in comparison to age- and sex-matched wild-type (SLC7A11+/+ ) littermate controls, we found morphologic changes-including increased dendritic complexity and mushroom spine area in males and reduced corpus callosum and soma size in females-that have previously been described, in each case, as morphological correlates of excitability. Consistent with this, we found that both male and female SLC7A11sut/sut mice had lower convulsive seizure thresholds and greater seizure severity than their sex-matched wild-type (SLC7A11+/+ ) littermates after acute challenge with two pharmacologically distinct chemoconvulsants: the Glu receptor agonist, kainic acid (KA), or the GABAA receptor antagonist, pentylenetetrazole (PTZ). These results suggest that the loss of Sxc - signaling in males and females perturbs excitatory/inhibitory (E/I) balance in vivo, potentially through its regulation of cellular and subcellular morphology.
Collapse
Affiliation(s)
- Sheila M S Sears
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| | - Sarah H Roberts
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, Syracuse University, Syracuse, New York, USA
| |
Collapse
|
10
|
Bondar A, Shubina L. The Relationship Between the Rhythmic Components of the Brain Electrical Activity During the Development of Status Epilepticus: An Operational Model of Brain Rhythms Generation. Brain Connect 2021; 12:571-583. [PMID: 34486376 DOI: 10.1089/brain.2021.0108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background/Introduction: Despite the fact that brain rhythms are widely studied and officially classified, there is no consensus on their relationship, which can shed light on the genesis of rhythmic activity, its synchronization, functional role, and the formation of pathological reactions. Using the experimental status epilepticus (SE) as a model of brain in a hypersynchronized state with well-defined rhythms, we aimed to study the relationship between the rhythmic components of the brain electrical activity. Materials and Methods: Local field potentials (LFPs) were recorded simultaneously from the hippocampus, entorhinal cortex, medial septum, and amygdala during normal conditions and after kainic acid (KA) administration in waking guinea pigs. The dynamical spectral LFP properties were analyzed with the aid of Fast Fourier transform. Results: KA induces prominent SE with periodic combination of epileptiform discharge complexes and relatively quiet interdischarge intervals in the electrical activity of the brain. We have shown that new components appeared in the LFP spectra during the development of SE, representing a sequential doubling of the frequency, which had initially been dominating in the background records. Discussion: The phenomenon of frequency doubling can be interpreted as the octave principle of the LFP spectrum rhythmic carcass structure. The spectra of discharge complexes represent an alternation of harmonic spectra, where fundamental frequency coincides with one of the doubled frequencies dominating in the interdischarge activity. Using a nonlinear recurrent operation of rhythm multiplication and the obtained data we propose an operational model of the generation of rhythms and pathological discharges in the brain based on the octave principle. Impact statement In this study, we examined the relationship between the rhythmic components of the electrical activity of the limbic structures during the experimental status epilepticus and propose an operational model of brain rhythms generation based on the octave principle. Our study demonstrates that using fundamental principles (nonlinearity and the presence of recurrence), it is possible to explain the genesis and phenomenology of the electrical activity of brain structures in normal and pathological conditions.
Collapse
Affiliation(s)
- Alexandr Bondar
- Department of Reception Mechanisms, Institute of Cell Biophysics of Russian Academy of Sciences, Pushchino, Russian Federation
| | - Liubov Shubina
- Laboratory of Systemic organization of Neurons, Institute of Theoretical and Experimental Biophysics of Russian Academy of Sciences, Pushchino, Russian Federation
| |
Collapse
|
11
|
Xu W, Wang Y, Qi X, Li K, Zhou L, Sha S, Wang X, Wu C, Du Y, Chen L. Involvement of TRPV4 in changes in rapidly inactivating potassium channels in the early stage of pilocarpine-induced status epilepticus in mice. J Cell Physiol 2021; 237:856-867. [PMID: 34415059 DOI: 10.1002/jcp.30558] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/06/2021] [Accepted: 08/11/2021] [Indexed: 11/11/2022]
Abstract
The rapidly inactivating potassium current (IA ) is important in controlling neuronal action potentials. Altered IA function and K+ channel expression have been found in epilepsy, and activation of the transient receptor potential vanilloid 4 (TRPV4) channel is involved in epilepsy pathogenesis. This study examined whether TRPV4 affects Kv4.2 and K+ channel interacting protein (KCHIP) expression and IA changes following pilocarpine-induced status epilepticus (PISE) in mice. Herein, hippocampal protein levels of Kv4.2 and KCHIP2 increased 3 h-3 d and decreased 7-30 d; that of KCHIP1 increased 3-24 h and decreased 3-30 d post-PISE. The TRPV4 antagonist HC-067047 attenuated the increased protein levels of Kv4.2 and KCHIP2 but not that of KCHIP1 post-PISE. The TRPV4 agonist GSK1016790A increased hippocampal protein levels of Kv4.2 and KCHIP2 but had no effect on KCHIP1 expression. HC-067047 attenuated the increased IA in hippocampal pyramidal neurons 24 h and 3 d post-PISE. GSK1016790A increased IA in hippocampal pyramidal neurons, shifting the voltage-dependent inactivation curve toward depolarization. The GSK1016790A-induced increase of IA was blocked by protein kinase A and calcium/calmodulin-dependent kinase II antagonists but was unaffected by protein kinase C antagonists. We conclude that TRPV4 activation may be responsible for the increases of Kv4.2 and KCHIP2 expression in hippocampi and IA in hippocampal pyramidal neurons in PISE mice, which are likely compensatory measures for hyperexcitability at the early stage of epilepsy.
Collapse
Affiliation(s)
- Weixing Xu
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Yue Wang
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Xiuting Qi
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Kunpeng Li
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Li Zhou
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Sha Sha
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Xiaoli Wang
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| | - Chunfeng Wu
- Department of Neurology, Children's Hospital of Nanjing Medical University, Nanjing, P.R. China
| | - Yimei Du
- Department of cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P.R. China
| | - Lei Chen
- Department of Physiology, Nanjing Medical University, Nanjing, P.R. China
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Maqoud F, Scala R, Hoxha M, Zappacosta B, Tricarico D. ATP-sensitive potassium channel subunits in the neuroinflammation: novel drug targets in neurodegenerative disorders. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2021; 21:130-149. [PMID: 33463481 DOI: 10.2174/1871527320666210119095626] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 08/07/2020] [Accepted: 08/28/2020] [Indexed: 11/22/2022]
Abstract
Arachidonic acids and its metabolites modulate plenty of ligand-gated, voltage-dependent ion channels, and metabolically regulated potassium channels including ATP-sensitive potassium channels (KATP). KATP channels are hetero-multimeric complexes of sulfonylureas receptors (SUR1, SUR2A or SUR2B) and the pore-forming subunits (Kir6.1 and Kir6.2) likewise expressed in the pre-post synapsis of neurons and inflammatory cells, thereby affecting their proliferation and activity. KATP channels are involved in amyloid-β (Aβ)-induced pathology, therefore emerging as therapeutic targets against Alzheimer's and related diseases. The modulation of these channels can represent an innovative strategy for the treatment of neurodegenerative disorders; nevertheless, the currently available drugs are not selective for brain KATP channels and show contrasting effects. This phenomenon can be a consequence of the multiple physiological roles of the different varieties of KATP channels. Openings of cardiac and muscular KATP channel subunits, is protective against caspase-dependent atrophy in these tissues and some neurodegenerative disorders, whereas in some neuroinflammatory diseases benefits can be obtained through the inhibition of neuronal KATP channel subunits. For example, glibenclamide exerts an anti-inflammatory effect in respiratory, digestive, urological, and central nervous system (CNS) diseases, as well as in ischemia-reperfusion injury associated with abnormal SUR1-Trpm4/TNF-α or SUR1-Trpm4/ Nos2/ROS signaling. Despite this strategy is promising, glibenclamide may have limited clinical efficacy due to its unselective blocking action of SUR2A/B subunits also expressed in cardiovascular apparatus with pro-arrhythmic effects and SUR1 expressed in pancreatic beta cells with hypoglycemic risk. Alternatively, neuronal selective dual modulators showing agonist/antagonist actions on KATP channels can be an option.
Collapse
Affiliation(s)
- Fatima Maqoud
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
| | - Rosa Scala
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
| | - Malvina Hoxha
- Department of Chemical-Toxicological and Pharmacological Evaluation of Drugs, Faculty of Pharmacy, "Catholic University Our Lady of Good Counsel", Tirana. Albania
| | - Bruno Zappacosta
- Department of Chemical-Toxicological and Pharmacological Evaluation of Drugs, Faculty of Pharmacy, "Catholic University Our Lady of Good Counsel", Tirana. Albania
| | - Domenico Tricarico
- Department of Pharmacy-Pharmaceutical Science, University of Bari Aldo Moro, via Orabona 4, 70125-I. Italy
| |
Collapse
|
14
|
Shi Z, Lei Z, Wu F, Xia L, Ruan Y, Xu ZC. Increased Sestrin3 Contributes to Post-ischemic Seizures in the Diabetic Condition. Front Neurosci 2021; 14:591207. [PMID: 33519354 PMCID: PMC7843462 DOI: 10.3389/fnins.2020.591207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 12/14/2020] [Indexed: 11/13/2022] Open
Abstract
Seizures are among the most common neurological sequelae of stroke, and diabetes notably increases the incidence of post-ischemic seizures. Recent studies have indicated that Sestrin3 (SESN3) is a regulator of a proconvulsant gene network in human epileptic hippocampus. But the association of SESN3 and post-ischemic seizures in diabetes remains unclear. The present study aimed to reveal the involvement of SESN3 in seizures following transient cerebral ischemia in diabetes. Diabetes was induced in adult male mice and rats via intraperitoneal injection of streptozotocin (STZ). Forebrain ischemia (15 min) was induced by bilateral common carotid artery occlusion, the 2-vessel occlusion (2VO) in mice and 4-vessel occlusion (4VO) in rats. Our results showed that 59% of the diabetic wild-type mice developed seizures after ischemia while no seizures were observed in non-diabetic mice. Although no apparent cell death was detected in the hippocampus of seizure mice within 24 h after the ischemic insult, the expression of SESN3 was significantly increased in seizure diabetic mice after ischemia. The post-ischemic seizure incidence significantly decreased in SESN3 knockout mice. Furthermore, all diabetic rats suffered from post-ischemic seizures and non-diabetic rats have no seizures. Electrophysiological recording showed an increased excitatory synaptic transmission and intrinsic membrane excitability in dentate granule cells of the rat hippocampus, together with decreased I A currents and Kv4.2 expression levels. The above results suggest that SESN3 up-regulation may contribute to neuronal hyperexcitability and seizure generation in diabetic animals after ischemia. Further studies are needed to explore the molecular mechanism of SESN3 in seizure generation after ischemia in diabetic conditions.
Collapse
Affiliation(s)
- Zhongshan Shi
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, United States.,Guangdong-Hongkong-Macau Institute for CNS Regeneration, Jinan University, Guangzhou, China.,Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zhigang Lei
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Fan Wu
- Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Luoxing Xia
- Guangdong-Hongkong-Macau Institute for CNS Regeneration, Jinan University, Guangzhou, China
| | - Yiwen Ruan
- Guangdong-Hongkong-Macau Institute for CNS Regeneration, Jinan University, Guangzhou, China.,Jiangsu Province Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China
| | - Zao C Xu
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, United States
| |
Collapse
|
15
|
Tiwari D, Schaefer TL, Schroeder-Carter LM, Krzeski JC, Bunk AT, Parkins EV, Snider A, Danzer R, Williams MT, Vorhees CV, Danzer SC, Gross C. The potassium channel Kv4.2 regulates dendritic spine morphology, electroencephalographic characteristics and seizure susceptibility in mice. Exp Neurol 2020; 334:113437. [PMID: 32822706 PMCID: PMC7642025 DOI: 10.1016/j.expneurol.2020.113437] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 08/13/2020] [Accepted: 08/17/2020] [Indexed: 01/21/2023]
Abstract
The voltage-gated potassium channel Kv4.2 is a critical regulator of dendritic excitability in the hippocampus and is crucial for dendritic signal integration. Kv4.2 mRNA and protein expression as well as function are reduced in several genetic and pharmacologically induced rodent models of epilepsy and autism. It is not known, however, whether reduced Kv4.2 is just an epiphenomenon or a disease-contributing cause of neuronal hyperexcitability and behavioral impairments in these neurological disorders. To address this question, we used male and female mice heterozygous for a Kv.2 deletion and adult-onset manipulation of hippocampal Kv4.2 expression in male mice to assess the role of Kv4.2 in regulating neuronal network excitability, morphology and anxiety-related behaviors. We observed a reduction in dendritic spine density and reduced proportions of thin and stubby spines but no changes in anxiety, overall activity, or retention of conditioned freezing memory in Kv4.2 heterozygous mice compared with wildtype littermates. Using EEG analyses, we showed elevated theta power and increased spike frequency in Kv4.2 heterozygous mice under basal conditions. In addition, the latency to onset of kainic acid-induced seizures was significantly shortened in Kv4.2 heterozygous mice compared with wildtype littermates, which was accompanied by a significant increase in theta power. By contrast, overexpressing Kv4.2 in wildtype mice through intrahippocampal injection of Kv4.2-expressing lentivirus delayed seizure onset and reduced EEG power. These results suggest that Kv4.2 is an important regulator of neuronal network excitability and dendritic spine morphology, but not anxiety-related behaviors. In the future, manipulation of Kv4.2 expression could be used to alter seizure susceptibility in epilepsy.
Collapse
Affiliation(s)
- Durgesh Tiwari
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Tori L Schaefer
- Division of Psychiatry, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | | | - Joseph C Krzeski
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Alexander T Bunk
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Emma V Parkins
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Andrew Snider
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Reese Danzer
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Michael T Williams
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Charles V Vorhees
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Steve C Danzer
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA; Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA
| | - Christina Gross
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
| |
Collapse
|
16
|
Tiwari D, Brager DH, Rymer JK, Bunk AT, White AR, Elsayed NA, Krzeski JC, Snider A, Schroeder Carter LM, Danzer SC, Gross C. MicroRNA inhibition upregulates hippocampal A-type potassium current and reduces seizure frequency in a mouse model of epilepsy. Neurobiol Dis 2019; 130:104508. [PMID: 31212067 DOI: 10.1016/j.nbd.2019.104508] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 06/12/2019] [Accepted: 06/13/2019] [Indexed: 12/13/2022] Open
Abstract
Epilepsy is often associated with altered expression or function of ion channels. One example of such a channelopathy is the reduction of A-type potassium currents in the hippocampal CA1 region. The underlying mechanisms of reduced A-type channel function in epilepsy are unclear. Here, we show that inhibiting a single microRNA, miR-324-5p, which targets the pore-forming A-type potassium channel subunit Kv4.2, selectively increased A-type potassium currents in hippocampal CA1 pyramidal neurons in mice. Resting membrane potential, input resistance and other potassium currents were not altered. In a mouse model of acquired chronic epilepsy, inhibition of miR-324-5p reduced the frequency of spontaneous seizures and interictal epileptiform spikes supporting the physiological relevance of miR-324-5p-mediated control of A-type currents in regulating neuronal excitability. Mechanistic analyses demonstrated that microRNA-induced silencing of Kv4.2 mRNA is increased in epileptic mice leading to reduced Kv4.2 protein levels, which is mitigated by miR-324-5p inhibition. By contrast, other targets of miR-324-5p were unchanged. These results suggest a selective miR-324-5p-dependent mechanism in epilepsy regulating potassium channel function, hyperexcitability and seizures.
Collapse
Affiliation(s)
- Durgesh Tiwari
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Darrin H Brager
- Center for Learning and Memory, Department of Neuroscience, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jeffrey K Rymer
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Alexander T Bunk
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Angela R White
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Nada A Elsayed
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Joseph C Krzeski
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Andrew Snider
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | | | - Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Anesthesia, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA
| | - Christina Gross
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH 45229, USA.
| |
Collapse
|
17
|
Noh W, Pak S, Choi G, Yang S, Yang S. Transient Potassium Channels: Therapeutic Targets for Brain Disorders. Front Cell Neurosci 2019; 13:265. [PMID: 31263403 PMCID: PMC6585177 DOI: 10.3389/fncel.2019.00265] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 05/28/2019] [Indexed: 01/04/2023] Open
Abstract
Transient potassium current channels (IA channels), which are expressed in most brain areas, have a central role in modulating feedforward and feedback inhibition along the dendroaxonic axis. Loss of the modulatory channels is tightly associated with a number of brain diseases such as Alzheimer’s disease, epilepsy, fragile X syndrome (FXS), Parkinson’s disease, chronic pain, tinnitus, and ataxia. However, the functional significance of IA channels in these diseases has so far been underestimated. In this review, we discuss the distribution and function of IA channels. Particularly, we posit that downregulation of IA channels results in neuronal (mostly dendritic) hyperexcitability accompanied by the imbalanced excitation and inhibition ratio in the brain’s networks, eventually causing the brain diseases. Finally, we propose a potential therapeutic target: the enhanced action of IA channels to counteract Ca2+-permeable channels including NMDA receptors could be harnessed to restore dendritic excitability, leading to a balanced neuronal state.
Collapse
Affiliation(s)
- Wonjun Noh
- Department of Nano-Bioengineering, Incheon National University, Incheon, South Korea
| | - Sojeong Pak
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Geunho Choi
- Department of Computer Science and Engineering, Incheon National University, Incheon, South Korea
| | - Sungchil Yang
- Department of Biomedical Sciences, City University of Hong Kong, Kowloon, Hong Kong
| | - Sunggu Yang
- Department of Nano-Bioengineering, Incheon National University, Incheon, South Korea
| |
Collapse
|
18
|
González OC, Krishnan GP, Timofeev I, Bazhenov M. Ionic and synaptic mechanisms of seizure generation and epileptogenesis. Neurobiol Dis 2019; 130:104485. [PMID: 31150792 DOI: 10.1016/j.nbd.2019.104485] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/23/2019] [Accepted: 05/27/2019] [Indexed: 01/09/2023] Open
Abstract
The biophysical mechanisms underlying epileptogenesis and the generation of seizures remain to be better understood. Among many factors triggering epileptogenesis are traumatic brain injury breaking normal synaptic homeostasis and genetic mutations disrupting ionic concentration homeostasis. Impairments in these mechanisms, as seen in various brain diseases, may push the brain network to a pathological state characterized by increased susceptibility to unprovoked seizures. Here, we review recent computational studies exploring the roles of ionic concentration dynamics in the generation, maintenance, and termination of seizures. We further discuss how ionic and synaptic homeostatic mechanisms may give rise to conditions which prime brain networks to exhibit recurrent spontaneous seizures and epilepsy.
Collapse
Affiliation(s)
- Oscar C González
- Neurosciences Graduate Program, University of California, San Diego, CA 92093, United States of America; Department of Medicine, University of California, San Diego, CA 92093, United States of America
| | - Giri P Krishnan
- Department of Medicine, University of California, San Diego, CA 92093, United States of America
| | - Igor Timofeev
- Centre de recherche de l'Institut universitaire en santé mentale de Québec (CRIUSMQ), 2601 de la Canardière, Québec, QC, Canada; Department of Psychiatry and Neuroscience, Université Laval, Québec, QC, Canada
| | - Maxim Bazhenov
- Neurosciences Graduate Program, University of California, San Diego, CA 92093, United States of America; Department of Medicine, University of California, San Diego, CA 92093, United States of America.
| |
Collapse
|
19
|
Murphy JG, Hoffman DA. A polybasic motif in alternatively spliced KChIP2 isoforms prevents Ca 2+ regulation of Kv4 channels. J Biol Chem 2019; 294:3683-3695. [PMID: 30622142 DOI: 10.1074/jbc.ra118.006549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/04/2019] [Indexed: 11/06/2022] Open
Abstract
The Kv4 family of A-type voltage-gated K+ channels regulates the excitability in hippocampal pyramidal neuron dendrites and are key determinants of dendritic integration, spike timing-dependent plasticity, long-term potentiation, and learning. Kv4.2 channel expression is down-regulated following hippocampal seizures and in epilepsy, suggesting A-type currents as therapeutic targets. In addition to pore-forming Kv4 subunits, modulatory auxiliary subunits called K+ channel-interacting proteins (KChIPs) modulate Kv4 expression and activity and are required to recapitulate native hippocampal A-type currents in heterologous expression systems. KChIP mRNAs contain multiple start sites and alternative exons that generate considerable N-terminal variation and functional diversity in shaping Kv4 currents. As members of the EF-hand domain-containing neuronal Ca2+ sensor protein family, KChIP auxiliary proteins may convey Ca2+ sensitivity upon Kv4 channels; however, to what degree intracellular Ca2+ regulates KChIP-Kv4.2 complexes is unclear. To answer this question, we expressed KChIP2 with Kv4.2 in HEK293T cells, and, with whole-cell patch-clamp electrophysiology, measured an ∼1.5-fold increase in Kv4.2 current density in the presence of elevated intracellular Ca2+ Intriguingly, the Ca2+ regulation of Kv4 current was specific to KChIP2b and KChIP2c splice isoforms that lack a putative polybasic domain that is present in longer KChIP2a1 and KChIP2a isoforms. Site-directed acidification of the basic residues within the polybasic motif of KChIP2a1 rescued Ca2+-mediated regulation of Kv4 current density. These results support divergent Ca2+ regulation of Kv4 channels mediated by alternative splicing of KChIP2 isoforms. They suggest that distinct KChIP-Kv4 interactions may differentially control excitability and function of hippocampal dendrites.
Collapse
Affiliation(s)
- Jonathan G Murphy
- From the NIGMS and .,Section on Molecular Neurophysiology, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Dax A Hoffman
- Section on Molecular Neurophysiology, NICHD, National Institutes of Health, Bethesda, Maryland 20892
| |
Collapse
|
20
|
Inhibition of Hsp70 Suppresses Neuronal Hyperexcitability and Attenuates Epilepsy by Enhancing A-Type Potassium Current. Cell Rep 2019; 26:168-181.e4. [DOI: 10.1016/j.celrep.2018.12.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 10/06/2018] [Accepted: 12/06/2018] [Indexed: 01/03/2023] Open
|
21
|
Thomas KT, Gross C, Bassell GJ. microRNAs Sculpt Neuronal Communication in a Tight Balance That Is Lost in Neurological Disease. Front Mol Neurosci 2018; 11:455. [PMID: 30618607 PMCID: PMC6299112 DOI: 10.3389/fnmol.2018.00455] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 11/26/2018] [Indexed: 12/13/2022] Open
Abstract
Since the discovery of the first microRNA 25 years ago, microRNAs (miRNAs) have emerged as critical regulators of gene expression within the mammalian brain. miRNAs are small non-coding RNAs that direct the RNA induced silencing complex to complementary sites on mRNA targets, leading to translational repression and/or mRNA degradation. Within the brain, intra- and extracellular signaling events tune the levels and activities of miRNAs to suit the needs of individual neurons under changing cellular contexts. Conversely, miRNAs shape neuronal communication by regulating the synthesis of proteins that mediate synaptic transmission and other forms of neuronal signaling. Several miRNAs have been shown to be critical for brain function regulating, for example, enduring forms of synaptic plasticity and dendritic morphology. Deficits in miRNA biogenesis have been linked to neurological deficits in humans, and widespread changes in miRNA levels occur in epilepsy, traumatic brain injury, and in response to less dramatic brain insults in rodent models. Manipulation of certain miRNAs can also alter the representation and progression of some of these disorders in rodent models. Recently, microdeletions encompassing MIR137HG, the host gene which encodes the miRNA miR-137, have been linked to autism and intellectual disability, and genome wide association studies have linked this locus to schizophrenia. Recent studies have demonstrated that miR-137 regulates several forms of synaptic plasticity as well as signaling cascades thought to be aberrant in schizophrenia. Together, these studies suggest a mechanism by which miRNA dysregulation might contribute to psychiatric disease and highlight the power of miRNAs to influence the human brain by sculpting communication between neurons.
Collapse
Affiliation(s)
- Kristen T. Thomas
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, TN, United States
| | - Christina Gross
- Division of Neurology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH, United States
- Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, United States
| | - Gary J. Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, United States
| |
Collapse
|
22
|
Derera ID, Smith KC, Smith BN. Altered A-type potassium channel function in the nucleus tractus solitarii in acquired temporal lobe epilepsy. J Neurophysiol 2018; 121:177-187. [PMID: 30517061 DOI: 10.1152/jn.00556.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Sudden unexpected death in epilepsy (SUDEP) is among the leading causes of death in people with epilepsy. Individuals with temporal lobe epilepsy (TLE) have a high risk for SUDEP because the seizures are often medically intractable. Neurons in the nucleus tractus solitarii (NTS) have been implicated in mouse models of SUDEP and play a critical role in modulating cardiorespiratory and autonomic output. Increased neuronal excitability of inhibitory, GABAergic neurons in the NTS develops during epileptogenesis, and NTS dysfunction has been implicated in mouse models of SUDEP. In this study we used the pilocarpine-induced status epilepticus model of TLE (i.e., pilo-SE mice) to investigate the A-type voltage-gated K+ channel as a potential contributor to increased excitability in GABAergic NTS neurons during epileptogenesis. Compared with age-matched control mice, pilo-SE mice displayed an increase in spontaneous action potential frequency and half-width 9-12 wk after treatment. Activity of GABAergic NTS neurons from pilo-SE mice showed less sensitivity to 4-aminopyridine. Correspondingly, reduced A-type K+ current amplitude was detected in these neurons, with no change in activation or inactivation kinetics. No changes were observed in Kv4.1, Kv4.2, Kv4.3, KChIP1, KChIP3, or KChIP4 mRNA expression. These changes contribute to the increased excitability in GABAergic NTS neurons that develops in TLE and may provide insight into potential mechanisms contributing to the increased risk for cardiorespiratory collapse and SUDEP in this model. NEW & NOTEWORTHY Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in epilepsy, and dysfunction in central autonomic neurons may play a role. In a mouse model of acquired epilepsy, GABAergic neurons in the nucleus tractus solitarii developed a reduced amplitude of the A-type current, which contributes to the increased excitability seen in these neurons during epileptogenesis. Neuronal excitability changes in inhibitory central vagal circuitry may increase the risk for cardiorespiratory collapse and SUDEP.
Collapse
Affiliation(s)
- Isabel D Derera
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - Katalin Cs Smith
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky.,Department of Neuroscience, College of Medicine, University of Kentucky , Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, College of Medicine, University of Kentucky , Lexington, Kentucky.,Department of Neuroscience, College of Medicine, University of Kentucky , Lexington, Kentucky.,Epilepsy Research Center, University of Kentucky , Lexington, Kentucky
| |
Collapse
|
23
|
Myers TL, Gonzalez OC, Stein JB, Bazhenov M. Characterizing Concentration-Dependent Neural Dynamics of 4-Aminopyridine-Induced Epileptiform Activity. ACTA ACUST UNITED AC 2018; 4. [PMID: 30450487 PMCID: PMC6234984 DOI: 10.4172/2472-0895.1000128] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Epilepsy remains one of the most common neurological disorders. In patients, it is characterized by unprovoked, spontaneous, and recurrent seizures or ictal events. Typically, inter-ictal events or large bouts of population level activity can be measured between seizures and are generally asymptomatic. Decades of research have focused on understanding the mechanisms leading to the development of seizure-like activity using various pro-convulsive pharmacological agents, including 4-aimnopyridine (4AP). However, the lack of consistency in the concentrations used for studying 4AP-induced epileptiform activity in animal models may give rise to differences in results and interpretation thereof. Indeed, the range of 4AP concentration in both in vivo and in vitro studies varies from 3 μM to 40 mM. Here, we explored the effects of various 4AP concentrations on the development and characteristics of hippocampal epileptiform activity in acute mouse brain slices of either sex. Using multi-electrode array recordings, we show that 4AP induces hippocampal epileptiform activity for a broad range of concentrations. The frequency component and the spatiotemporal patterns of the epileptiform activity revealed a dose-dependent response. Finally, in the presence of 4AP, reduction of KCC2 co-transporter activity by KCC2 antagonist VU0240551 prevented the manifestation of the frequency component differences between different concentrations of 4AP. Overall, the study predicts that different concentrations of 4AP can result in the different mechanisms behind hippocampal epileptiform activity, of which some are dependent on the KCC2 co-transporter function.
Collapse
Affiliation(s)
- Timothy L Myers
- Neuroscience Graduate Program, University of California, Riverside, California, United States of America.,Department of Cell Biology and Neuroscience, University of California, Riverside, California, United States of America
| | - Oscar C Gonzalez
- Department of Medicine, University of California, San Diego, California, United States of America.,Neuroscience Graduate Program, University of California, San Diego, California, United States of America
| | - Jacob B Stein
- Department of Cell Biology and Neuroscience, University of California, Riverside, California, United States of America
| | - Maxim Bazhenov
- Department of Medicine, University of California, San Diego, California, United States of America
| |
Collapse
|
24
|
Wang YJ, Hsieh CP, Chan MH, Chan TY, Chen L, Chen HH. Distinct effects of resveratrol on seizures and hyperexcitability induced by NMDA and 4-aminopyridine. Nutr Neurosci 2018; 22:867-876. [DOI: 10.1080/1028415x.2018.1461458] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Ya-Jean Wang
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
- Department of Nursing, Hsin Sheng College of Medical Care and Management, Longtan Township, Taoyuan County, Taiwan
| | - Chung-Pin Hsieh
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
| | - Ming-Huan Chan
- Institute of Neuroscience, National Chengchi University, Taipei City, Taiwan
- Research Center for Mind, Brain, and Learning, National Chengchi University, Taipei City, Taiwan
| | - Tzu-Yi Chan
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
| | - Linyi Chen
- Institute of Molecular Medicine, National Tsing Hua University, Hsinchu, Taiwan
| | - Hwei-Hisen Chen
- Center for Neuropsychiatric Research, National Health Research Institutes, Zhunan, Miaoli County, Taiwan
- Institute of Neuroscience, National Chengchi University, Taipei City, Taiwan
| |
Collapse
|
25
|
Navidhamidi M, Ghasemi M, Mehranfard N. Epilepsy-associated alterations in hippocampal excitability. Rev Neurosci 2018; 28:307-334. [PMID: 28099137 DOI: 10.1515/revneuro-2016-0059] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/03/2016] [Indexed: 11/15/2022]
Abstract
The hippocampus exhibits a wide range of epilepsy-related abnormalities and is situated in the mesial temporal lobe, where limbic seizures begin. These abnormalities could affect membrane excitability and lead to overstimulation of neurons. Multiple overlapping processes refer to neural homeostatic responses develop in neurons that work together to restore neuronal firing rates to control levels. Nevertheless, homeostatic mechanisms are unable to restore normal neuronal excitability, and the epileptic hippocampus becomes hyperexcitable or hypoexcitable. Studies show that there is hyperexcitability even before starting recurrent spontaneous seizures, suggesting although hippocampal hyperexcitability may contribute to epileptogenesis, it alone is insufficient to produce epileptic seizures. This supports the concept that the hippocampus is not the only substrate for limbic seizure onset, and a broader hyperexcitable limbic structure may contribute to temporal lobe epilepsy (TLE) seizures. Nevertheless, seizures also occur in conditions where the hippocampus shows a hypoexcitable phenotype. Since TLE seizures most often originate in the hippocampus, it could therefore be assumed that both hippocampal hypoexcitability and hyperexcitability are undesirable states that make the epileptic hippocampal network less stable and may, under certain conditions, trigger seizures.
Collapse
|
26
|
González OC, Shiri Z, Krishnan GP, Myers TL, Williams S, Avoli M, Bazhenov M. Role of KCC2-dependent potassium efflux in 4-Aminopyridine-induced Epileptiform synchronization. Neurobiol Dis 2018; 109:137-147. [PMID: 29045814 PMCID: PMC5710807 DOI: 10.1016/j.nbd.2017.10.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/09/2017] [Accepted: 10/13/2017] [Indexed: 01/23/2023] Open
Abstract
A balance between excitation and inhibition is necessary to maintain stable brain network dynamics. Traditionally, seizure activity is believed to arise from the breakdown of this delicate balance in favor of excitation with loss of inhibition. Surprisingly, recent experimental evidence suggests that this conventional view may be limited, and that inhibition plays a prominent role in the development of epileptiform synchronization. Here, we explored the role of the KCC2 co-transporter in the onset of inhibitory network-induced seizures. Our experiments in acute mouse brain slices, of either sex, revealed that optogenetic stimulation of either parvalbumin- or somatostatin-expressing interneurons induced ictal discharges in rodent entorhinal cortex during 4-aminopyridine application. These data point to a proconvulsive role of GABAA receptor signaling that is independent of the inhibitory input location (i.e., dendritic vs. somatic). We developed a biophysically realistic network model implementing dynamics of ion concentrations to explore the mechanisms leading to inhibitory network-induced seizures. In agreement with experimental results, we found that stimulation of the inhibitory interneurons induced seizure-like activity in a network with reduced potassium A-current. Our model predicts that interneuron stimulation triggered an increase of interneuron firing, which was accompanied by an increase in the intracellular chloride concentration and a subsequent KCC2-dependent gradual accumulation of the extracellular potassium promoting epileptiform ictal activity. When the KCC2 activity was reduced, stimulation of the interneurons was no longer able to induce ictal events. Overall, our study provides evidence for a proconvulsive role of GABAA receptor signaling that depends on the involvement of the KCC2 co-transporter.
Collapse
Affiliation(s)
- Oscar C González
- Neurosciences Graduate Program, University of California, San Diego, CA, United States; Department of Medicine, University of California, San Diego, CA, United States
| | - Zahra Shiri
- Montreal Neurological Institute, McGill University, Montréal, H4H 1R3 Québec, Canada
| | - Giri P Krishnan
- Department of Medicine, University of California, San Diego, CA, United States
| | - Timothy L Myers
- Neuroscience Graduate Program, University of California, Riverside, CA, United States; Department of Cell Biology and Neuroscience, University of California, Riverside, CA, United States
| | - Sylvain Williams
- Douglas Mental Health University Institute, McGill University, Montréal, H4H 1R3 Québec, Canada
| | - Massimo Avoli
- Montreal Neurological Institute, McGill University, Montréal, H4H 1R3 Québec, Canada; Department of Physiology, McGill University, Montréal, H4H 1R3 Québec, Canada
| | - Maxim Bazhenov
- Neurosciences Graduate Program, University of California, San Diego, CA, United States; Department of Medicine, University of California, San Diego, CA, United States.
| |
Collapse
|
27
|
Gross C, Yao X, Engel T, Tiwari D, Xing L, Rowley S, Danielson SW, Thomas KT, Jimenez-Mateos EM, Schroeder LM, Pun RYK, Danzer SC, Henshall DC, Bassell GJ. MicroRNA-Mediated Downregulation of the Potassium Channel Kv4.2 Contributes to Seizure Onset. Cell Rep 2017; 17:37-45. [PMID: 27681419 DOI: 10.1016/j.celrep.2016.08.074] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 07/18/2016] [Accepted: 08/19/2016] [Indexed: 02/05/2023] Open
Abstract
Seizures are bursts of excessive synchronized neuronal activity, suggesting that mechanisms controlling brain excitability are compromised. The voltage-gated potassium channel Kv4.2, a major mediator of hyperpolarizing A-type currents in the brain, is a crucial regulator of neuronal excitability. Kv4.2 expression levels are reduced following seizures and in epilepsy, but the underlying mechanisms remain unclear. Here, we report that Kv4.2 mRNA is recruited to the RNA-induced silencing complex shortly after status epilepticus in mice and after kainic acid treatment of hippocampal neurons, coincident with reduction of Kv4.2 protein. We show that the microRNA miR-324-5p inhibits Kv4.2 protein expression and that antagonizing miR-324-5p is neuroprotective and seizure suppressive. MiR-324-5p inhibition also blocks kainic-acid-induced reduction of Kv4.2 protein in vitro and in vivo and delays kainic-acid-induced seizure onset in wild-type but not in Kcnd2 knockout mice. These results reveal an important role for miR-324-5p-mediated silencing of Kv4.2 in seizure onset.
Collapse
Affiliation(s)
- Christina Gross
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45229, USA; Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Xiaodi Yao
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Tobias Engel
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland
| | - Durgesh Tiwari
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Lei Xing
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Shane Rowley
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Scott W Danielson
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Kristen T Thomas
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Eva M Jimenez-Mateos
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland
| | - Lindsay M Schroeder
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Raymund Y K Pun
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Steve C Danzer
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45229, USA; Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA; Department of Anesthesiology, University of Cincinnati, Cincinnati, OH 45229, USA
| | - David C Henshall
- Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, Dublin 2, Ireland
| | - Gary J Bassell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA; Department of Neurology, Emory University School of Medicine, Atlanta, GA 30322, USA
| |
Collapse
|
28
|
Kim JE, Hyun HW, Min SJ, Lee DS, Jeon AR, Kim MJ, Kang TC. PLPP/CIN Regulates Seizure Activity by the Differential Modulation of Calsenilin Binding to GluN1 and Kv4.2 in Mice. Front Mol Neurosci 2017; 10:303. [PMID: 28993724 PMCID: PMC5622162 DOI: 10.3389/fnmol.2017.00303] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 09/11/2017] [Indexed: 12/28/2022] Open
Abstract
Calsenilin (CSEN) binds to Kv4.2 (an A-type K+ channel) as well as N-methyl-D-aspartate receptor (NMDAR), and modulates their activities. However, the regulatory mechanisms for CSEN-binding to Kv4.2 or NMDAR remain elusive. Here, we demonstrate the novel role of pyridoxal-5′-phosphate phosphatase/chronophin (PLPP/CIN), one of the cofilin-mediated F-actin regulators, in the CSEN binding to Kv4.2 or GluN1 (an NMDAR subunit). PLPP/CIN dephosphorylated CSEN in competition with casein kinase 1, independent of cofilin dephosphorylation. As compared to wild-type mice, PLPP/CIN transgenic (PLPP/CINTg) mice showed the enhancement of Kv4.2–CSEN binding, but the reduction in CSEN–GluN1 binding. In addition, PLPP/CINTg mice exhibited the higher intensity (severity), duration and progression of seizures, but the longer latency of seizure on-set in response to kainic acid. PLPP/CIN knockout mice reversed these phenomena. Therefore, we suggest that PLPP/CIN-mediated CSEN dephosphorylation may play an important role in the functional coupling of NMDAR and Kv4.2, which regulates the neuronal excitability.
Collapse
Affiliation(s)
- Ji-Eun Kim
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - Hye-Won Hyun
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - Su-Ji Min
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - Duk-Shin Lee
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - A Ran Jeon
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - Min Ju Kim
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| | - Tae-Cheon Kang
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym UniversityChuncheon, South Korea
| |
Collapse
|
29
|
Neuron subset-specific Pten deletion induces abnormal skeletal activity in mice. Exp Neurol 2017; 291:98-105. [PMID: 28163158 DOI: 10.1016/j.expneurol.2017.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 01/27/2017] [Accepted: 02/01/2017] [Indexed: 12/13/2022]
Abstract
Individuals with a history of epilepsy are at higher risk for bone fractures compared to the general population. Although clinical studies support an association between low bone mineral density (BMD) and anti-seizure medications, little is known on whether a history of seizures is linked to altered bone health. Therefore, in this study we tested the hypothesis that bone mass, morphology, and bone mineralization are altered by seizures in genetically epileptic animals and in animals subjected to an episode of status epilepticus. In this study, we used NS-Pten conditional knockout mice (a well-studied genetic model of epilepsy). We used microCT analysis to measure BMD, morphology, and mineralization in NS-Pten+/+ (wildtype) and NS-Pten-/- (knockout) mice at 4 and 8weeks, as well as adult Kv4.2+/+ and Kv4.2-/- mice. We measured BMD, bone morphology, and mineralization in adult NS-Pten+/+ mice that received status epilepticus through kainic acid (20mg/kg intraperitoneal). Further, we measured locomotion for NS-Pten+/+ and NS-Pten-/- mice at 4 and 6weeks. We found that NS-Pten-/- mice exhibited low BMD in the tibial metaphysis and midshaft compared to non-epileptic mice. Morphologically, NS-Pten-/- mice exhibited decreased trabecular volume fraction, and endocortical expansion in both the metaphyeal and diaphyseal compartments. In the midshaft, NS-Pten-/- mice exhibited reduced tissue mineral density, indicating impaired mineralization in addition to morphological deficits. NS-Pten-/- mice exhibited hyperactivity in open field testing, suggesting low bone mass in NS-Pten-/- mice was not attributable to hypoactivity. Differences in BMD were not observed following kainate-induced seizures or in the Kv4.2-/- model of seizure susceptibility. Our findings suggest that deletion of Pten in the brain results in impaired bone mass and mineralization, which may contribute to weaker bones and thereby a higher fracture risk.
Collapse
|
30
|
Smith G, Ahmed N, Arbuckle E, Lugo JN. Early-life status epilepticus induces long-term deficits in anxiety and spatial learning in mice. ACTA ACUST UNITED AC 2017; 4:36-45. [PMID: 31890565 DOI: 10.1016/j.ijep.2016.12.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Background One of the most devastating aspects of developmental epilepsy is the long-term impact on behavior. Children with epilepsy show a high co-morbidity with anxiety disorders and autism. Methods To examine whether early-life status epilepticus results in altered anxiety, repetitive behavior, social behavior, and learning and memory, we induced status epilepticus in male C57BL/6 mice on postnatal day (PD) 10. The mice received intraperitoneal injections of either kainic acid (2mg/kg) or 0.9% normal saline. We also included a nontreated control group. Kainic acid induced status epilepticus for approximately 1.5 hrs. At PD60, the adult mice were then tested in a battery of behavioral tasks, including open field activity, elevated-plus maze, light-dark test, marble burying, social chamber, social partition, conditioned fear, novel object recognition, and Morris water maze. Results The early-life seizure group showed consistent increases in anxiety in the open field test (p < 0.05), elevated plus maze (p < 0.05), and light-dark task (p < 0.01). The seizure group showed significant (p < 0.01) impairment in the Morris water maze. There were no differences observed in marble burying, social partition, social chamber, novel object recognition, or delay fear conditioning tasks. Conclusions These results demonstrate that a single insult of status epilepticus during the neonatal period is sufficient to cause specific, long-term impairments in anxiety and spatial learning.
Collapse
Affiliation(s)
- Gregory Smith
- Institute of Biomedical Sciences, Baylor University, Waco, TX 76798, USA
| | - Nowrin Ahmed
- Department of Psychology and Neuroscience, Baylor University, Waco, TX 76798, USA
| | - Erin Arbuckle
- Institute of Biomedical Sciences, Baylor University, Waco, TX 76798, USA
| | - Joaquin N Lugo
- Institute of Biomedical Sciences, Baylor University, Waco, TX 76798, USA
- Department of Psychology and Neuroscience, Baylor University, Waco, TX 76798, USA
| |
Collapse
|
31
|
Superimposing Status Epilepticus on Neuron Subset-Specific PTEN Haploinsufficient and Wild Type Mice Results in Long-term Changes in Behavior. Sci Rep 2016; 6:36559. [PMID: 27819284 PMCID: PMC5098193 DOI: 10.1038/srep36559] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 10/18/2016] [Indexed: 01/09/2023] Open
Abstract
We evaluated the effects of superimposing seizures on a genetic mutation with known involvement in both Autism Spectrum Disorder and in epilepsy. Neuron-subset specific (NS)-Pten heterozygous (HT) and wildtype (WT) adult mice received either intraperitoneal injections of kainic acid (20 mg/kg) to induce status epilepticus or the vehicle (saline). Animals then received a battery of behavioral tasks in order to evaluate activity levels, anxiety, repetitive-stereotyped behavior, social behavior, learning and memory. In the open field task, we found that HT mice after seizures showed a significant increase in total activity and total distance in the surround region of the open field. In the elevated plus maze task, we found that HT mice after seizures displayed increased total distance and velocity as compared to HT mice that did not undergo seizures and WT controls. In the social chamber test, we found the HT mice after seizures displayed an impairment in social behavior. These findings demonstrate that superimposing seizures on a genetic mutation can result in long-term alterations in activity and social behavior in mice.
Collapse
|
32
|
Reduced expression of IA channels is associated with post-ischemic seizures. Epilepsy Res 2016; 124:40-8. [PMID: 27259067 DOI: 10.1016/j.eplepsyres.2016.05.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 12/09/2015] [Accepted: 05/17/2016] [Indexed: 01/04/2023]
Abstract
PURPOSE Post-stroke seizures are considered as a major cause of epilepsy in adults. The pathophysiologic mechanisms resulting in post-stroke seizures are not fully understood. The present study attempted to reveal a new mechanism underlying neuronal hyperexcitability responsible to the seizure development after ischemic stroke. METHODS Transient global ischemia was produced in adult Wistar rats using the 4-vessel occlusion (4-VO) method. The spontaneous behavioral seizures were defined by the Racine scale III-V. The neuronal death in the brain was determined by hematoxylin-eosin staining. The expression levels of A-type potassium channels were analyzed by immunohistochemical staining and western blotting. RESULTS We found that the incidence of spontaneous behavioral seizures increased according to the severity of ischemia with 0% after 15-min ischemia and ∼50% after 25-min ischemia. All behavioral seizures occurred with 48h after ischemia. Morphological analysis indicated that brain damage was not correlated with behavioral seizures. Immunohistochemical staining showed that the expression levels of the A-type potassium channel subunit Kv4.2 was significantly reduced in ischemic brains with behavioral seizures, but not in ischemic brains without seizures. In addition, rats failing to develop spontaneous behavioral seizures within 2days after ischemia were more sensitive to bicuculline-induced seizures at 2 months after ischemia than control rats. Meanwhile, Kv4.2 expression was decreased in brain at 2 months after ischemia. CONCLUSION Our results demonstrated the reduction of Kv4.2 expression might contribute to the development of post-ischemic seizures and long-term increased seizure susceptibility after ischemia. The mechanisms underlying post-stroke seizures and epilepsy is unknown so far. The down-regulation of IA channels may explained the abnormal neuronal hyperexcitability responsible for the seizure development after ischemic stroke.
Collapse
|
33
|
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.
Collapse
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
| |
Collapse
|
34
|
Gupte RP, Kadunganattil S, Shepherd AJ, Merrill R, Planer W, Bruchas MR, Strack S, Mohapatra DP. Convergent phosphomodulation of the major neuronal dendritic potassium channel Kv4.2 by pituitary adenylate cyclase-activating polypeptide. Neuropharmacology 2015; 101:291-308. [PMID: 26456351 DOI: 10.1016/j.neuropharm.2015.10.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/29/2015] [Accepted: 10/03/2015] [Indexed: 12/30/2022]
Abstract
The endogenous neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is secreted by both neuronal and non-neuronal cells in the brain and spinal cord, in response to pathological conditions such as stroke, seizures, chronic inflammatory and neuropathic pain. PACAP has been shown to exert various neuromodulatory and neuroprotective effects. However, direct influence of PACAP on the function of intrinsically excitable ion channels that are critical to both hyperexcitation as well as cell death, remain largely unexplored. The major dendritic K(+) channel Kv4.2 is a critical regulator of neuronal excitability, back-propagating action potentials in the dendrites, and modulation of synaptic inputs. We identified, cloned and characterized the downstream signaling originating from the activation of three PACAP receptor (PAC1) isoforms that are expressed in rodent hippocampal neurons that also exhibit abundant expression of Kv4.2 protein. Activation of PAC1 by PACAP leads to phosphorylation of Kv4.2 and downregulation of channel currents, which can be attenuated by inhibition of either PKA or ERK1/2 activity. Mechanistically, this dynamic downregulation of Kv4.2 function is a consequence of reduction in the density of surface channels, without any influence on the voltage-dependence of channel activation. Interestingly, PKA-induced effects on Kv4.2 were mediated by ERK1/2 phosphorylation of the channel at two critical residues, but not by direct channel phosphorylation by PKA, suggesting a convergent phosphomodulatory signaling cascade. Altogether, our findings suggest a novel GPCR-channel signaling crosstalk between PACAP/PAC1 and Kv4.2 channel in a manner that could lead to neuronal hyperexcitability.
Collapse
Affiliation(s)
- Raeesa P Gupte
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Suraj Kadunganattil
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Andrew J Shepherd
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Ronald Merrill
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - William Planer
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael R Bruchas
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stefan Strack
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA
| | - Durga P Mohapatra
- Department of Pharmacology, The University of Iowa Roy J. and Lucile A. Carver College of Medicine, Iowa City, IA 52242, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA; Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA.
| |
Collapse
|
35
|
Leclercq K, Afrikanova T, Langlois M, De Prins A, Buenafe OE, Rospo CC, Van Eeckhaut A, de Witte PAM, Crawford AD, Smolders I, Esguerra CV, Kaminski RM. Cross-species pharmacological characterization of the allylglycine seizure model in mice and larval zebrafish. Epilepsy Behav 2015; 45:53-63. [PMID: 25845493 DOI: 10.1016/j.yebeh.2015.03.019] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 03/16/2015] [Accepted: 03/17/2015] [Indexed: 01/29/2023]
Abstract
Treatment-resistant seizures affect about a third of patients suffering from epilepsy. To fulfill the need for new medications targeting treatment-resistant seizures, a number of rodent models offer the opportunity to assess a variety of potential treatment approaches. The use of such models, however, has proven to be time-consuming and labor-intensive. In this study, we performed pharmacological characterization of the allylglycine (AG) seizure model, a simple in vivo model for which we demonstrated a high level of treatment resistance. (d,l)-Allylglycine inhibits glutamic acid decarboxylase (GAD) - the key enzyme in γ-aminobutyric acid (GABA) biosynthesis - leading to GABA depletion, seizures, and neuronal damage. We performed a side-by-side comparison of mouse and zebrafish acute AG treatments including biochemical, electrographic, and behavioral assessments. Interestingly, seizure progression rate and GABA depletion kinetics were comparable in both species. Five mechanistically diverse antiepileptic drugs (AEDs) were used. Three out of the five AEDs (levetiracetam, phenytoin, and topiramate) showed only a limited protective effect (mainly mortality delay) at doses close to the TD50 (dose inducing motor impairment in 50% of animals) in mice. The two remaining AEDs (diazepam and sodium valproate) displayed protective activity against AG-induced seizures. Experiments performed in zebrafish larvae revealed behavioral AED activity profiles highly analogous to those obtained in mice. Having demonstrated cross-species similarities and limited efficacy of tested AEDs, we propose the use of AG in zebrafish as a convenient and high-throughput model of treatment-resistant seizures.
Collapse
Affiliation(s)
| | - Tatiana Afrikanova
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Melanie Langlois
- Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - An De Prins
- Center for Neurosciences, C4N, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Olivia E Buenafe
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Chiara C Rospo
- Neuroscience TA, UCB Biopharma, Braine-l'Alleud, Belgium
| | - Ann Van Eeckhaut
- Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Peter A M de Witte
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium
| | - Alexander D Crawford
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium; Luxembourg Center for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| | - Ilse Smolders
- Center for Neurosciences, C4N, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Brussels, Belgium
| | - Camila V Esguerra
- Laboratory for Molecular Biodiscovery, Department of Pharmaceutical and Pharmacological Sciences, University of Leuven, Leuven, Belgium; Chemical Neuroscience Group, Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway.
| | | |
Collapse
|
36
|
Guglielmi L, Servettini I, Caramia M, Catacuzzeno L, Franciolini F, D'Adamo MC, Pessia M. Update on the implication of potassium channels in autism: K(+) channelautism spectrum disorder. Front Cell Neurosci 2015; 9:34. [PMID: 25784856 PMCID: PMC4345917 DOI: 10.3389/fncel.2015.00034] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2014] [Accepted: 01/20/2015] [Indexed: 11/16/2022] Open
Abstract
Autism spectrum disorders (ASDs) are characterized by impaired ability to properly implement environmental stimuli that are essential to achieve a state of social and cultural exchange. Indeed, the main features of ASD are impairments of interpersonal relationships, verbal and non-verbal communication and restricted and repetitive behaviors. These aspects are often accompanied by several comorbidities such as motor delay, praxis impairment, gait abnormalities, insomnia, and above all epilepsy. Genetic analyses of autistic individuals uncovered deleterious mutations in several K+ channel types strengthening the notion that their intrinsic dysfunction may play a central etiologic role in ASD. However, indirect implication of K+ channels in ASD has been also reported. For instance, loss of fragile X mental retardation protein (FMRP) results in K+ channels deregulation, network dysfunction and ASD-like cognitive and behavioral symptoms. This review provides an update on direct and indirect implications of K+ channels in ASDs. Owing to a mounting body of evidence associating a channelopathy pathogenesis to autism and showing that nearly 500 ion channel proteins are encoded by the human genome, we propose to classify ASDs - whose susceptibility is significantly enhanced by ion channels defects, either in a monogenic or multigenic condition - in a new category named “channelAutismSpectrumDisorder” (channelASD; cASD) and introduce a new taxonomy (e.g., Kvx.y-channelASD and likewise Navx.y-channelASD, Cavx.y-channelASD; etc.). This review also highlights some degree of clinical and genetic overlap between K+ channelASDs and K+ channelepsies, whereby such correlation suggests that a subcategory characterized by a channelASD-channelepsy phenotype may be distinguished. Ultimately, this overview aims to further understand the different clinical subgroups and help parse out the distinct biological basis of autism that are essential to establish patient-tailored treatments.
Collapse
Affiliation(s)
- Luca Guglielmi
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia Italy
| | - Ilenio Servettini
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia Italy
| | - Martino Caramia
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia Italy
| | - Maria Cristina D'Adamo
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia Italy
| | - Mauro Pessia
- Section of Physiology and Biochemistry, Department of Experimental Medicine, University of Perugia School of Medicine, Perugia Italy
| |
Collapse
|
37
|
Effects of fluoxetine on protein expression of potassium ion channels in the brain of chronic mild stress rats. Acta Pharm Sin B 2015; 5:55-61. [PMID: 26579425 PMCID: PMC4629207 DOI: 10.1016/j.apsb.2014.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Revised: 12/05/2014] [Accepted: 12/09/2014] [Indexed: 11/23/2022] Open
Abstract
The purpose of this study is to investigate the expression of major potassium channel subtypes in the brain of chronical mild stress (CMS) rats and reveal the effects of fluoxetine on the expression of these channels. Rats were exposed to a variety of unpredictable stress for three weeks and induced anhedonia, lower sucrose preference, locomotor activity and lower body weight. The protein expressions were determined by Western blot. CMS significantly increased the expression of Kv2.1 channel in frontal cortex but not in hippocampus, and the expression level was normalized after fluoxetine treatment. The expression of TREK-1 channel was also obviously increased in frontal cortex in CMS rats. Fluoxetine treatment might prevent this increase. However, the expression of Kv3.1 and Kv4.2 channels was considerably decreased in hippocampus after CMS, and was not affected by fluoxetine. These results suggest that different subtypes of potassium channels are associated with the pathophysiology of depression and that the therapeutical effects of fluoxetine may relate to Kv2.1 and TREK-1 potassium channels.
Collapse
|
38
|
Rainnie DG, Hazra R, Dabrowska J, Guo JD, Li CC, Dewitt S, Muly EC. Distribution and functional expression of Kv4 family α subunits and associated KChIP β subunits in the bed nucleus of the stria terminalis. J Comp Neurol 2014; 522:609-25. [PMID: 24037673 DOI: 10.1002/cne.23435] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 06/28/2013] [Accepted: 07/02/2013] [Indexed: 12/22/2022]
Abstract
Regulation of BNSTALG neuronal firing activity is tightly regulated by the opposing actions of the fast outward potassium current, IA , mediated by α subunits of the Kv4 family of ion channels, and the transient inward calcium current, IT . Together, these channels play a critical role in regulating the latency to action potential onset, duration, and frequency, as well as dendritic back-propagation and synaptic plasticity. Previously we have shown that Type I-III BNSTALG neurons express mRNA transcripts for each of the Kv4 α subunits. However, the biophysical properties of native IA channels are critically dependent on the formation of macromolecular complexes of Kv4 channels with a family of chaperone proteins, the potassium channel-interacting proteins (KChIP1-4). Here we used a multidisciplinary approach to investigate the expression and function of Kv4 channels and KChIPs in neurons of the rat BNSTALG . Using immunofluorescence we demonstrated the pattern of localization of Kv4.2, Kv4.3, and KChIP1-4 proteins in the BNSTALG . Moreover, our single-cell reverse-transcription polymerase chain reaction (scRT-PCR) studies revealed that mRNA transcripts for Kv4.2, Kv4.3, and all four KChIPs were differentially expressed in Type I-III BNSTALG neurons. Furthermore, immunoelectron microscopy revealed that Kv4.2 and Kv4.3 channels were primarily localized to the dendrites and spines of BNSTALG neurons, and are thus ideally situated to modulate synaptic transmission. Consistent with this observation, in vitro patch clamp recordings showed that reducing postsynaptic IA in these neurons lowered the threshold for long-term potentiation (LTP) induction. These results are discussed in relation to potential modulation of IA channels by chronic stress.
Collapse
Affiliation(s)
- Donald G Rainnie
- Department of Psychiatry and Behavioral Sciences, Emory University, Atlanta, Georgia; Division of Behavioral Neuroscience and Psychiatric Disorders, Yerkes National Primate Research Center, Atlanta, Georgia
| | | | | | | | | | | | | |
Collapse
|
39
|
Lei Z, Zhang H, Liang Y, Cui Q, Xu Z, Xu ZC. Reduced expression of IA channels is associated with postischemic seizures in hyperglycemic rats. J Neurosci Res 2014; 92:1775-84. [PMID: 25043828 DOI: 10.1002/jnr.23445] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 04/14/2014] [Accepted: 06/01/2014] [Indexed: 01/04/2023]
Abstract
Poststroke seizures are considered to be the major cause of epilepsy in the elderly. The mechanisms of poststroke seizures remain unclear. A history of diabetes mellitus has been identified as an independent predictor of acute poststroke seizures in stroke patients. The present study sought to reveal the mechanisms for the development of postischemic seizures under hyperglycemic conditions. Transient forebrain ischemia was produced in adult Wistar rats by using the four-vessel occlusion method. At the normal blood glucose level, seizures occurred in ∼50% of rats after 25 min of ischemia. However, in rats with hyperglycemia, the incidence rate of postischemic seizures was significantly increased to 100%. The occurrence of postischemic seizures was not correlated with the severity of brain damage in hyperglycemic rats. Mannitol, an osmotic diuretic agent, could neither prevent postischemic seizures nor alleviate the exacerbated brain damage in the presence of hyperglycemia. K(+) channels play a critical role in controlling neuronal excitability. The expression of A-type K(+) channel subunit Kv4.2 in the hippocampus and the cortex was significantly reduced in hyperglycemic rats with seizures compared with those without seizures. These results suggest that the reduction of Kv4.2 expression could contribute to the development of postischemic seizures in hyperglycemia.
Collapse
Affiliation(s)
- Zhigang Lei
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | | | | | | | | | | |
Collapse
|
40
|
Tabarean IV. Electrical remodeling of preoptic GABAergic neurons involves the Kv1.5 subunit. PLoS One 2014; 9:e96643. [PMID: 24797243 PMCID: PMC4010509 DOI: 10.1371/journal.pone.0096643] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 04/09/2014] [Indexed: 11/18/2022] Open
Abstract
The electrogenic machinery of an excitable cell can adapt in response to changes in input, genetic deficit or in pathological conditions, however the underlying molecular mechanisms are not understood. In cases of genetic deletion it is commonly observed that a channel subunit from the same family replaces the missing one. We have previously reported that Kv4.2−/− preoptic GABAergic neurons display identical firing characteristics to those of wild-type neurons despite having reduced A-type currents, and that, surprisingly, they present a robust upregulation of a delayed rectifier current, the nature of which is unknown. Here, using pharmacology, qPCR and Western blots we report that, although the wild-type neurons express several Kv subunits, the upregulated current is conducted by the Kv1.5 subunit exclusively. Thus, this study reveals the molecular nature of a novel mechanism of electrical remodeling in central neurons.
Collapse
Affiliation(s)
- Iustin V. Tabarean
- The Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
41
|
DiNuzzo M, Mangia S, Maraviglia B, Giove F. Physiological bases of the K+ and the glutamate/GABA hypotheses of epilepsy. Epilepsy Res 2014; 108:995-1012. [PMID: 24818957 DOI: 10.1016/j.eplepsyres.2014.04.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 03/20/2014] [Accepted: 04/01/2014] [Indexed: 01/19/2023]
Abstract
Epilepsy is a heterogeneous family of neurological disorders that manifest as seizures, i.e. the hypersynchronous activity of large population of neurons. About 30% of epileptic patients do not respond to currently available antiepileptic drugs. Decades of intense research have elucidated the involvement of a number of possible signaling pathways, however, at present we do not have a fundamental understanding of epileptogenesis. In this paper, we review the literature on epilepsy under a wide-angle perspective, a mandatory choice that responds to the recurrent and unanswered question about what is epiphenomenal and what is causal to the disease. While focusing on the involvement of K+ and glutamate/GABA in determining neuronal hyperexcitability, emphasis is given to astrocytic contribution to epileptogenesis, and especially to loss-of-function of astrocytic glutamine synthetase following reactive astrogliosis, a hallmark of epileptic syndromes. We finally introduce the potential involvement of abnormal glycogen synthesis induced by excess glutamate in increasing susceptibility to seizures.
Collapse
Affiliation(s)
- Mauro DiNuzzo
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy.
| | - Silvia Mangia
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, USA
| | - Bruno Maraviglia
- Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy; Fondazione Santa Lucia IRCCS, Rome, Italy
| | - Federico Giove
- MARBILab, Museo storico della fisica e Centro di studi e ricerche "Enrico Fermi", Rome, Italy; Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy
| |
Collapse
|
42
|
Shah NH, Aizenman E. Voltage-gated potassium channels at the crossroads of neuronal function, ischemic tolerance, and neurodegeneration. Transl Stroke Res 2013; 5:38-58. [PMID: 24323720 DOI: 10.1007/s12975-013-0297-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/14/2013] [Accepted: 10/14/2013] [Indexed: 11/29/2022]
Abstract
Voltage-gated potassium (Kv) channels are widely expressed in the central and peripheral nervous system and are crucial mediators of neuronal excitability. Importantly, these channels also actively participate in cellular and molecular signaling pathways that regulate the life and death of neurons. Injury-mediated increased K(+) efflux through Kv2.1 channels promotes neuronal apoptosis, contributing to widespread neuronal loss in neurodegenerative disorders such as Alzheimer's disease and stroke. In contrast, some forms of neuronal activity can dramatically alter Kv2.1 channel phosphorylation levels and influence their localization. These changes are normally accompanied by modifications in channel voltage dependence, which may be neuroprotective within the context of ischemic injury. Kv1 and Kv7 channel dysfunction leads to neuronal hyperexcitability that critically contributes to the pathophysiology of human clinical disorders such as episodic ataxia and epilepsy. This review summarizes the neurotoxic, neuroprotective, and neuroregulatory roles of Kv channels and highlights the consequences of Kv channel dysfunction on neuronal physiology. The studies described in this review thus underscore the importance of normal Kv channel function in neurons and emphasize the therapeutic potential of targeting Kv channels in the treatment of a wide range of neurological diseases.
Collapse
Affiliation(s)
- Niyathi Hegde Shah
- Department of Neurobiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, E1456 BST, Pittsburgh, PA, 15261, USA,
| | | |
Collapse
|
43
|
Sánchez Fernández I, Abend NS, Agadi S, An S, Arya R, Carpenter JL, Chapman KE, Gaillard WD, Glauser TA, Goldstein DB, Goldstein JL, Goodkin HP, Hahn CD, Heinzen EL, Mikati MA, Peariso K, Pestian JP, Ream M, Riviello JJ, Tasker RC, Williams K, Loddenkemper T. Gaps and opportunities in refractory status epilepticus research in children: a multi-center approach by the Pediatric Status Epilepticus Research Group (pSERG). Seizure 2013; 23:87-97. [PMID: 24183923 PMCID: PMC6387832 DOI: 10.1016/j.seizure.2013.10.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 10/07/2013] [Accepted: 10/09/2013] [Indexed: 11/29/2022] Open
Abstract
PURPOSE Status epilepticus (SE) is a life-threatening condition that can be refractory to initial treatment. Randomized controlled studies to guide treatment choices, especially beyond first-line drugs, are not available. This report summarizes the evidence that guides the management of refractory convulsive SE (RCSE) in children, defines gaps in our clinical knowledge and describes the development and works of the 'pediatric Status Epilepticus Research Group' (pSERG). METHODS A literature review was performed to evaluate current gaps in the pediatric SE and RCSE literature. In person and online meetings helped to develop and expand the pSERG network. RESULTS The care of pediatric RCSE is largely based on extrapolations of limited evidence derived from adult literature and supplemented with case reports and case series in children. No comparative effectiveness trials have been performed in the pediatric population. Gaps in knowledge include risk factors for SE, biomarkers of SE and RCSE, second- and third-line treatment options, and long-term outcome. CONCLUSION The care of children with RCSE is based on limited evidence. In order to address these knowledge gaps, the multicenter pSERG was established to facilitate prospective collection, analysis, and sharing of de-identified data and biological specimens from children with RCSE. These data will allow identification of treatment strategies associated with better outcomes and delineate evidence-based interventions to improve the care of children with SE.
Collapse
Affiliation(s)
- Iván Sánchez Fernández
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States; Department of Child Neurology, Hospital Sant Joan de Déu, University of Barcelona, Spain
| | - Nicholas S Abend
- Division of Neurology, The Children's Hospital of Philadelphia, The Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States
| | - Satish Agadi
- Section of Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, TX, United States
| | - Sookee An
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Ravindra Arya
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, United States
| | - Jessica L Carpenter
- Department of Epilepsy, Neurophysiology, and Critical Care Neurology, The Children's National Medical Center, George Washington University School of Medicine and Health Sciences, Washington, DC, United States
| | - Kevin E Chapman
- Department of Pediatrics and Neurology, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, United States
| | - William D Gaillard
- Department of Epilepsy, Neurophysiology, and Critical Care Neurology, The Children's National Medical Center, George Washington University School of Medicine and Health Sciences, Washington, DC, United States
| | - Tracy A Glauser
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, United States
| | - David B Goldstein
- Center for Human Genome Variation, Duke University Medical Center, Duke University, Durham, NC, United States
| | - Joshua L Goldstein
- Division of Neurology, Department of Pediatrics, Ann & Robert Lurie's Children's Hospital, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Howard P Goodkin
- Department of Neurology and Department of Pediatrics, The University of Virginia Health System, Charlottesville, VA, United States
| | - Cecil D Hahn
- Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Erin L Heinzen
- Center for Human Genome Variation, Duke University Medical Center, Duke University, Durham, NC, United States
| | - Mohamad A Mikati
- Division of Pediatric Neurology, Duke University Medical Center, Duke University, Durham, NC, United States
| | - Katrina Peariso
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, United States
| | - John P Pestian
- Comprehensive Epilepsy Center, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, United States
| | - Margie Ream
- Division of Pediatric Neurology, Duke University Medical Center, Duke University, Durham, NC, United States
| | - James J Riviello
- Division of Pediatric Neurology, Department of Neurology, New York University Langone Medical Center, New York University School of Medicine, New York, NY, United States
| | - Robert C Tasker
- Department of Neurology, Department of Anesthesiology, Perioperative and Pain Medicine, Division of Critical Care, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States
| | - Korwyn Williams
- Division of Pediatric Neurology, Phoenix Children's Hospital, Phoenix, AZ, United States
| | - Tobias Loddenkemper
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States.
| | | |
Collapse
|
44
|
D'Adamo MC, Catacuzzeno L, Di Giovanni G, Franciolini F, Pessia M. K(+) channelepsy: progress in the neurobiology of potassium channels and epilepsy. Front Cell Neurosci 2013; 7:134. [PMID: 24062639 PMCID: PMC3772396 DOI: 10.3389/fncel.2013.00134] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 08/06/2013] [Indexed: 12/19/2022] Open
Abstract
K(+) channels are important determinants of seizure susceptibility. These membrane proteins, encoded by more than 70 genes, make the largest group of ion channels that fine-tune the electrical activity of neuronal and non-neuronal cells in the brain. Their ubiquity and extremely high genetic and functional diversity, unmatched by any other ion channel type, place K(+) channels as primary targets of genetic variations or perturbations in K(+)-dependent homeostasis, even in the absence of a primary channel defect. It is therefore not surprising that numerous inherited or acquired K(+) channels dysfunctions have been associated with several neurologic syndromes, including epilepsy, which often generate confusion in the classification of the associated diseases. Therefore, we propose to name the K(+) channels defects underlying distinct epilepsies as "K(+) channelepsies," and introduce a new nomenclature (e.g., Kx.y-channelepsy), following the widely used K(+) channel classification, which could be also adopted to easily identify other channelopathies involving Na(+) (e.g., Nav x.y-phenotype), Ca(2+) (e.g., Cav x.y-phenotype), and Cl(-) channels. Furthermore, we discuss novel genetic defects in K(+) channels and associated proteins that underlie distinct epileptic phenotypes in humans, and analyze critically the recent progress in the neurobiology of this disease that has also been provided by investigations on valuable animal models of epilepsy. The abundant and varied lines of evidence discussed here strongly foster assessments for variations in genes encoding for K(+) channels and associated proteins in patients with idiopathic epilepsy, provide new avenues for future investigations, and highlight these proteins as critical pharmacological targets.
Collapse
Key Words
- Potassium channels: [Kv1, Kv2, Kv3, Kv4, Kv8, Kv11(HERG), KCa1.1, Kvβ1, Kvβ2, KChIP LGI1, Kir1-Kir7 (GIRK, KATP)]
- autism–epilepsy
- channelopathies
- temporal lobe epilepsy
Collapse
Affiliation(s)
- Maria Cristina D'Adamo
- Faculty of Medicine, Section of Human Physiology, Department of Internal Medicine, University of Perugia Perugia, Italy ; Istituto Euro Mediterraneo di Scienza e Tecnologia, IEMEST Palermo, Italy
| | | | | | | | | |
Collapse
|
45
|
Wang HG, He XP, Li Q, Madison RD, Moore SD, McNamara JO, Pitt GS. The auxiliary subunit KChIP2 is an essential regulator of homeostatic excitability. J Biol Chem 2013; 288:13258-68. [PMID: 23536187 DOI: 10.1074/jbc.m112.434548] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
BACKGROUND The necessity for, or redundancy of, distinctive KChIP proteins is not known. RESULTS Deletion of KChIP2 leads to increased susceptibility to epilepsy and to a reduction in IA and increased excitability in pyramidal hippocampal neurons. CONCLUSION KChIP2 is essential for homeostasis in hippocampal neurons. SIGNIFICANCE Mutations in K(A) channel auxiliary subunits may be loci for epilepsy. The somatodendritic IA (A-type) K(+) current underlies neuronal excitability, and loss of IA has been associated with the development of epilepsy. Whether any one of the four auxiliary potassium channel interacting proteins (KChIPs), KChIP1-KChIP4, in specific neuronal populations is critical for IA is not known. Here we show that KChIP2, which is abundantly expressed in hippocampal pyramidal cells, is essential for IA regulation in hippocampal neurons and that deletion of Kchip2 affects susceptibility to limbic seizures. The specific effects of Kchip2 deletion on IA recorded from isolated hippocampal pyramidal neurons were a reduction in amplitude and shift in the V½ for steady-state inactivation to hyperpolarized potentials when compared with WT neurons. Consistent with the relative loss of IA, hippocampal neurons from Kchip2(-/-) mice showed increased excitability. WT cultured neurons fired only occasional single action potentials, but the average spontaneous firing rate (spikes/s) was almost 10-fold greater in Kchip2(-/-) neurons. In slice preparations, spontaneous firing was detected in CA1 pyramidal neurons from Kchip2(-/-) mice but not from WT. Additionally, when seizures were induced by kindling, the number of stimulations required to evoke an initial class 4 or 5 seizure was decreased, and the average duration of electrographic seizures was longer in Kchip2(-/-) mice compared with WT controls. Together, these data demonstrate that the KChIP2 is essential for physiologic IA modulation and homeostatic stability and that there is a lack of functional redundancy among the different KChIPs in hippocampal neurons.
Collapse
Affiliation(s)
- Hong-Gang Wang
- Division of Cardiology, Department of Medicine, Duke University, Medical Center, Durham, NC 27710, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Saikosaponin a Enhances Transient Inactivating Potassium Current in Rat Hippocampal CA1 Neurons. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2013; 2013:413092. [PMID: 23554830 PMCID: PMC3608310 DOI: 10.1155/2013/413092] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/01/2013] [Indexed: 11/18/2022]
Abstract
Saikosaponin a (SSa), a main constituent of the Chinese herb Bupleurum chinense DC., has been demonstrated to have antiepileptic activity. Recent studies have shown that SSa could inhibit NMDA receptor current and persistent sodium current. However, the effects of SSa on potassium (K+) currents remain unclear. In this study, we tested the effect of SSa on 4AP-induced epileptiform discharges and K+ currents in CA1 neurons of rat hippocampal slices. We found that SSa significantly inhibited epileptiform discharges frequency and duration in hippocampal CA1 neurons in the 4AP seizure model in a dose-dependent manner with an IC50
of 0.7 μM. SSa effectively increased the amplitude of ITotal
and IA, significantly negative-shifted the activation curve, and positive-shifted steady-state curve of IA. However, SSa induced no significant changes in the amplitude and activation curve of IK. In addition, SSa significantly increased the amplitude of 4AP-sensitive K+ current, while there was no significant change in the amplitude of TEA-sensitive K+ current. Together, our data indicate that SSa inhibits epileptiform discharges induced by 4AP in a dose-dependent manner and that SSa exerts selectively enhancing effects on IA. These increases in IA may contribute to the anticonvulsant mechanisms of SSa.
Collapse
|
47
|
Abstract
Ion channel dysfunction or "channelopathy" is a proven cause of epilepsy in the relatively uncommon genetic epilepsies with Mendelian inheritance. But numerous examples of acquired channelopathy in experimental animal models of epilepsy following brain injury have also been demonstrated. Our understanding of channelopathy has grown due to advances in electrophysiology techniques that have allowed the study of ion channels in the dendrites of pyramidal neurons in cortex and hippocampus. The apical dendrites of pyramidal neurons comprise the vast majority of neuronal surface membrane area, and thus the majority of the neuronal ion channel population. Investigation of dendritic ion channels has demonstrated remarkable plasticity in ion channel localization and biophysical properties in epilepsy, many of which produce hyperexcitability and may contribute to the development and maintenance of the epileptic state. Herein we review recent advances in dendritic physiology and cell biology, and their relevance to epilepsy.
Collapse
Affiliation(s)
- Nicholas P Poolos
- Department of Neurology and Regional Epilepsy Center, University of Washington, Seattle, Washington 98104, USA.
| | | |
Collapse
|
48
|
Lugo JN, Brewster AL, Spencer CM, Anderson AE. Kv4.2 knockout mice have hippocampal-dependent learning and memory deficits. Learn Mem 2012; 19:182-9. [PMID: 22505720 DOI: 10.1101/lm.023614.111] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Kv4.2 channels contribute to the transient, outward K(+) current (A-type current) in hippocampal dendrites, and modulation of this current substantially alters dendritic excitability. Using Kv4.2 knockout (KO) mice, we examined the role of Kv4.2 in hippocampal-dependent learning and memory. We found that Kv4.2 KO mice showed a deficit in the learning phase of the Morris water maze (MWM) and significant impairment in the probe trial compared with wild type (WT). Kv4.2 KO mice also demonstrated a specific deficit in contextual learning in the fear-conditioning test, without impairment in the conditioned stimulus or new context condition. Kv4.2 KO mice had normal activity, anxiety levels, and prepulse inhibition compared with WT mice. A compensatory increase in tonic inhibition has been previously described in hippocampal slice recordings from Kv4.2 KO mice. In an attempt to decipher whether increased tonic inhibition contributed to the learning and memory deficits in Kv4.2 KO mice, we administered picrotoxin to block GABA(A) receptors (GABA(A)R), and thereby tonic inhibition. This manipulation had no effect on behavior in the WT or KO mice. Furthermore, total protein levels of the α5 or δ GABA(A)R subunits, which contribute to tonic inhibition, were unchanged in hippocampus. Overall, our findings add to the growing body of evidence, suggesting an important role for Kv4.2 channels in hippocampal-dependent learning and memory.
Collapse
Affiliation(s)
- Joaquin N Lugo
- Cain Foundation Laboratories, Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030, USA
| | | | | | | |
Collapse
|
49
|
Kiselycznyk C, Hoffman DA, Holmes A. Effects of genetic deletion of the Kv4.2 voltage-gated potassium channel on murine anxiety-, fear- and stress-related behaviors. BIOLOGY OF MOOD & ANXIETY DISORDERS 2012; 2:5. [PMID: 22738428 PMCID: PMC3384232 DOI: 10.1186/2045-5380-2-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Accepted: 03/02/2012] [Indexed: 01/06/2023]
Abstract
Background Potassium channels have been proposed to play a role in mechanisms of neural plasticity, and the Kv4.2 subunit has been implicated in the regulation of action-potential back-propagation to the dendrites. Alterations in mechanisms of plasticity have been further proposed to underlie various psychiatric disorders, but the role of Kv4.2 in anxiety or depression is not well understood. Methods In this paper, we analyzed the phenotype Kv4.2 knockout mice based on their neurological function, on a battery of behaviors including those related to anxiety and depression, and on plasticity-related learning tasks. Results We found a novelty-induced hyperactive phenotype in knockout mice, and these mice also displayed increased reactivity to novel stimulus such as an auditory tone. No clear anxiety- or depression-related phenotype was observed, nor any alterations in learning/plasticity-based paradigms. Conclusions We did not find clear evidence for an involvement of Kv4.2 in neuropsychiatric or plasticity-related phenotypes, but there was support for a role in Kv4.2 in dampening excitatory responses to novel stimuli.
Collapse
Affiliation(s)
- Carly Kiselycznyk
- Laboratory of Behavioral and Genomic Neuroscience, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, MD, USA.
| | | | | |
Collapse
|
50
|
Cotella D, Radicke S, Cipriani V, Cavaletto M, Merlin S, Follenzi A, Ravens U, Wettwer E, Santoro C, Sblattero D. N-glycosylation of the mammalian dipeptidyl aminopeptidase-like protein 10 (DPP10) regulates trafficking and interaction with Kv4 channels. Int J Biochem Cell Biol 2012; 44:876-85. [PMID: 22387313 DOI: 10.1016/j.biocel.2012.02.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 02/09/2012] [Accepted: 02/14/2012] [Indexed: 02/01/2023]
Abstract
The dipeptidyl aminopeptidase-like protein 10 (DPP10) is a type II transmembrane protein homologue to the serine protease DPPIV/CD26 but enzymatically inactive. In the mammalian brain, DPP10 forms a complex with voltage-gated potassium channels of the Kv4 family, regulating their cell surface expression and biophysical properties. DPP10 is a glycoprotein containing eight predicted N-glycosylation sites in the extracellular domain. In this study we investigated the role of N-glycosylation on DPP10 trafficking and functional activity. Using site-directed mutagenesis (N to Q) we showed that N-glycosylation occured at six positions. Glycosylation at these specific residues was necessary for DPP10 trafficking to the plasma membrane as observed by flow cytometry. The surface expression levels of the substitutions N90Q, N119Q, N257Q and N342Q were reduced by more than 60%. Hence the interaction with the Kv4.3/KChIP2a channel complex was disrupted preventing the hastening effect of wild type DPP10 on current kinetics. Interestingly, N257 was crucial for this function and its substitution to glutamine completely blocked DPP10 sorting to the cell surface and prevented DPP10 dimerization. In summary, we demonstrated that glycosylation was necessary for both DPP10 trafficking to the cell surface and functional interaction with Kv4 channels.
Collapse
Affiliation(s)
- Diego Cotella
- Department of Health Sciences and Interdisciplinary Research Centre on Autoimmune Diseases (IRCAD), Università del Piemonte Orientale A. Avogadro, Via Solaroli 17, 28100 Novara, Italy.
| | | | | | | | | | | | | | | | | | | |
Collapse
|