1
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Zhang YJ, Wang TS, Zhu XM, Yu LF, Zhang LM, Zhou YF, Wang Y, Zhou SZ. Biallelic variants of KCNQ2 in early infantile developmental and epileptic encephalopathy. Seizure 2024; 116:159-161. [PMID: 36934001 DOI: 10.1016/j.seizure.2023.03.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 03/02/2023] [Accepted: 03/11/2023] [Indexed: 03/14/2023] Open
Affiliation(s)
- Yun-Jian Zhang
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Tian-Shuang Wang
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Xiao-Mei Zhu
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Li-Fei Yu
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Lin-Mei Zhang
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Yuan-Feng Zhou
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Yi Wang
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China
| | - Shui-Zhen Zhou
- Department of Neurology, National Children's Medical Center, Children's Hospital of Fudan University, Shanghai, China.
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2
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Knight D, Mahida S, Kelly M, Poduri A, Olson HE. Ezogabine impacts seizures and development in patients with KCNQ2 developmental and epileptic encephalopathy. Epilepsia 2023. [PMID: 37096745 DOI: 10.1111/epi.17627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 04/03/2023] [Accepted: 04/24/2023] [Indexed: 04/26/2023]
Abstract
Genetic variants in KCNQ2 are associated with a range of epilepsies, from self- limited (familial) neonatal-infantile epilepsy to developmental and epileptic encephalopathy (DEE). We retrospectively reviewed clinical data from eight patients with KCNQ2-related DEE who were treated with ezogabine. Treatment was initiated at a median age of 8 months (range 7 weeks to 2.5 years) and continued for a median of 2.6 years (range 7 months to 4.5 years). Five individuals had daily seizures at baseline and experienced at least 50% seizure reduction with treatment, sustained in four. One individual with two to four yearly seizures improved to rare events. Two individuals were seizure-free; treatment targeted cognition and development. Developmental improvements were reported in all eight patients. Weaning of ezogabine was associated with increased seizure frequency (N = 4), agitation and irritability (N = 2), poor sleep (N = 1), and developmental regression (N = 2). These data suggest that treatment with ezogabine is effective at reducing seizure burden and is associated with improved development. Minimal side effects were observed. Weaning was associated with increased seizures and behavioral disturbances in a subset. An approach targeting potassium channel dysfunction with ezogabine is warranted in patients with KCNQ2-related DEE.
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Affiliation(s)
- Devon Knight
- Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA, USA
| | - Sonal Mahida
- Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA, USA
| | - Mckenna Kelly
- Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA, USA
- University of Colorado School of Medicine, Denver, CO, USA
| | - Annapurna Poduri
- Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA, USA
| | - Heather E Olson
- Epilepsy Genetics Program, Boston Children's Hospital, Boston, MA, USA
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3
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Edmond MA, Hinojo-Perez A, Wu X, Perez Rodriguez ME, Barro-Soria R. Distinctive mechanisms of epilepsy-causing mutants discovered by measuring S4 movement in KCNQ2 channels. eLife 2022; 11:77030. [PMID: 35642783 PMCID: PMC9197397 DOI: 10.7554/elife.77030] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 05/31/2022] [Indexed: 01/10/2023] Open
Abstract
Neuronal KCNQ channels mediate the M-current, a key regulator of membrane excitability in the central and peripheral nervous systems. Mutations in KCNQ2 channels cause severe neurodevelopmental disorders, including epileptic encephalopathies. However, the impact that different mutations have on channel function remains poorly defined, largely because of our limited understanding of the voltage-sensing mechanisms that trigger channel gating. Here, we define the parameters of voltage sensor movements in wt-KCNQ2 and channels bearing epilepsy-associated mutations using cysteine accessibility and voltage clamp fluorometry (VCF). Cysteine modification reveals that a stretch of eight to nine amino acids in the S4 becomes exposed upon voltage sensing domain activation of KCNQ2 channels. VCF shows that the voltage dependence and the time course of S4 movement and channel opening/closing closely correlate. VCF reveals different mechanisms by which different epilepsy-associated mutations affect KCNQ2 channel voltage-dependent gating. This study provides insight into KCNQ2 channel function, which will aid in uncovering the mechanisms underlying channelopathies.
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Affiliation(s)
- Michaela A Edmond
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
| | - Andy Hinojo-Perez
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
| | - Xiaoan Wu
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, United States
| | - Marta E Perez Rodriguez
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, United States
| | - Rene Barro-Soria
- Department of Medicine, Miller School of Medicine, University of Miami, Miami, United States
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4
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Zhang HXB, Heckman L, Niday Z, Jo S, Fujita A, Shim J, Pandey R, Al Jandal H, Jayakar S, Barrett LB, Smith J, Woolf CJ, Bean BP. Cannabidiol activates neuronal Kv7 channels. eLife 2022; 11:73246. [PMID: 35179483 PMCID: PMC8856652 DOI: 10.7554/elife.73246] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 02/09/2022] [Indexed: 01/10/2023] Open
Abstract
Cannabidiol (CBD), a chemical found in the Cannabis sativa plant, is a clinically effective antiepileptic drug whose mechanism of action is unknown. Using a fluorescence-based thallium flux assay, we performed a large-scale screen and found enhancement of flux through heterologously expressed human Kv7.2/7.3 channels by CBD. Patch-clamp recordings showed that CBD acts at submicromolar concentrations to shift the voltage dependence of Kv7.2/7.3 channels in the hyperpolarizing direction, producing a dramatic enhancement of current at voltages near –50 mV. CBD enhanced native M-current in mouse superior cervical ganglion starting at concentrations of 30 nM and also enhanced M-current in rat hippocampal neurons. The potent enhancement of Kv2/7.3 channels by CBD may contribute to its effectiveness as an antiepileptic drug by reducing neuronal hyperexcitability.
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Affiliation(s)
| | - Laurel Heckman
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Zachary Niday
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Sooyeon Jo
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Akie Fujita
- Department of Neurobiology, Harvard Medical School, Boston, United States
| | - Jaehoon Shim
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Roshan Pandey
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Hoor Al Jandal
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Selwyn Jayakar
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Lee B Barrett
- F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Jennifer Smith
- ICCB-Longwood Screening Facility and Department of Immunology, Harvard Medical School, Boston, United States
| | - Clifford J Woolf
- Department of Neurobiology, Harvard Medical School, Boston, United States.,F.M. Kirby Neurobiology Research Center, Boston Children's Hospital, Boston, United States
| | - Bruce P Bean
- Department of Neurobiology, Harvard Medical School, Boston, United States
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5
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Abstract
The trigeminal nerve (V) is the fifth and largest of all cranial nerves, and it is responsible for detecting sensory stimuli that arise from the craniofacial area. The nerve is divided into three branches: ophthalmic (V1), maxillary (V2), and mandibular (V3); their cell bodies are located in the trigeminal ganglia and they make connections with second-order neurons in the trigeminal brainstem sensory nuclear complex. Ascending projections via the trigeminothalamic tract transmit information to the thalamus and other brain regions responsible for interpreting sensory information. One of the most common forms of craniofacial pain is trigeminal neuralgia. Trigeminal neuralgia is characterized by sudden, brief, and excruciating facial pain attacks in one or more of the V branches, leading to a severe reduction in the quality of life of affected patients. Trigeminal neuralgia etiology can be classified into idiopathic, classic, and secondary. Classic trigeminal neuralgia is associated with neurovascular compression in the trigeminal root entry zone, which can lead to demyelination and a dysregulation of voltage-gated sodium channel expression in the membrane. These alterations may be responsible for pain attacks in trigeminal neuralgia patients. The antiepileptic drugs carbamazepine and oxcarbazepine are the first-line pharmacological treatment for trigeminal neuralgia. Their mechanism of action is a modulation of voltage-gated sodium channels, leading to a decrease in neuronal activity. Although carbamazepine and oxcarbazepine are the first-line treatment, other drugs may be useful for pain control in trigeminal neuralgia. Among them, the anticonvulsants gabapentin, pregabalin, lamotrigine and phenytoin, baclofen, and botulinum toxin type A can be coadministered with carbamazepine or oxcarbazepine for a synergistic approach. New pharmacological alternatives are being explored such as the active metabolite of oxcarbazepine, eslicarbazepine, and the new Nav1.7 blocker vixotrigine. The pharmacological profiles of these drugs are addressed in this review.
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Affiliation(s)
- Eder Gambeta
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Juliana G Chichorro
- Department of Pharmacology, Biological Sciences Sector, Federal University of Parana, Curitiba, Brazil
| | - Gerald W. Zamponi
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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6
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Dirkx N, Miceli F, Taglialatela M, Weckhuysen S. The Role of Kv7.2 in Neurodevelopment: Insights and Gaps in Our Understanding. Front Physiol 2020; 11:570588. [PMID: 33192566 PMCID: PMC7657400 DOI: 10.3389/fphys.2020.570588] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 09/07/2020] [Indexed: 11/13/2022] Open
Abstract
Kv7.2 subunits encoded by the KCNQ2 gene constitute a critical molecular component of the M-current, a subthreshold voltage-gated potassium current controlling neuronal excitability by dampening repetitive action potential firing. Pathogenic loss-of-function variants in KCNQ2 have been linked to epilepsy since 1998, and there is ample functional evidence showing that dysfunction of the channel indeed results in neuronal hyperexcitability. The recent description of individuals with severe developmental delay with or without seizures due to pathogenic variants in KCNQ2 (KCNQ2-encephalopathy) reveals that Kv7.2 channels also have an important role in neurodevelopment. Kv7.2 channels are expressed already very early in the developing brain when key developmental processes such as proliferation, differentiation, and synaptogenesis play a crucial role in brain morphogenesis and maturation. In this review, we will discuss the available evidence for a role of Kv7.2 channels in these neurodevelopmental processes, focusing in particular on insights derived from KCNQ2-related human phenotypes, from the spatio-temporal expression of Kv7.2 and other Kv7 family member, and from cellular and rodent models, highlighting critical gaps and research strategies to be implemented in the future. Lastly, we propose a model which divides the M-current activity in three different developmental stages, correlating with the cell characteristics during these particular periods in neuronal development, and how this can be linked with KCNQ2-related disorders. Understanding these mechanisms can create opportunities for new targeted therapies for KCNQ2-encephalopathy.
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Affiliation(s)
- Nina Dirkx
- Applied and Translational Neurogenomics Group, VIB Center for Molecular Neurology, Vlaams Instituut voor Biotechnologie, Antwerp, Belgium
| | - Francesco Miceli
- Section of Pharmacology, Department of Neuroscience, University of Naples Federico II, Naples, Italy
| | - Maurizio Taglialatela
- Section of Pharmacology, Department of Neuroscience, University of Naples Federico II, Naples, Italy
| | - Sarah Weckhuysen
- Applied and Translational Neurogenomics Group, VIB Center for Molecular Neurology, Vlaams Instituut voor Biotechnologie, Antwerp, Belgium.,Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.,Department of Neurology, Antwerp University Hospital, Antwerp, Belgium
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7
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Tran B, Ji ZG, Xu M, Tsuchida TN, Cooper EC. Two KCNQ2 Encephalopathy Variants in the Calmodulin-Binding Helix A Exhibit Dominant-Negative Effects and Altered PIP 2 Interaction. Front Physiol 2020; 11:1144. [PMID: 33041849 PMCID: PMC7518097 DOI: 10.3389/fphys.2020.571813] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 08/18/2020] [Indexed: 11/13/2022] Open
Abstract
Heterozygous missense variants in KCNQ2, which encodes the potassium channel subunit Kv7.2, are among the most common genetic causes of severe neonatal-onset epileptic encephalopathy. Because about 20% of known severe Kv7.2 missense changes lie within the intracellular C-terminal region, improving understanding of the underlying pathogenic mechanisms is important. We analyzed the basis for the severe phenotypes of Kv7.2 A337T and A337G, variants in the C-terminal’s calmodulin (CaM)-binding Helix A. When expressed heterologously in mammalian cells, alone or in combination with wild type Kv7.2 or with wild type Kv7.2 and Kv7.3, both variants strongly suppressed channel currents. A337T channels expressed alone exhibited significantly reduced protein half-life and surface trafficking and co-immunoprecipitated less CaM. For both variants, increasing cellular phosphatidylinositol 4,5-bisphosphate (PIP2) by overexpression of PI(4)P5-kinase restored current densities. For both variants, the fraction of current suppressed by activation of M1 muscarinic receptors with 10 μM oxotremorine methiodide, which depletes PIP2, was less than for controls. During voltage-sensitive phosphatase-induced transient PIP2 depletion and resynthesize, potassium current inhibition and recovery kinetics were both markedly slowed. These results suggest that these variants may reduce currents by a mechanism not previously described: slowing of PIP2 migration between the bulk membrane and binding sites mediating channel electromechanical coupling. A novel Kv7.2/3-selective opener, SF0034, rescued current amplitudes. Our findings show that these two Helix A variants suppress channel current density strongly, consistent with their severe heterozygous phenotypes, implicate impairment of CaM and PIP2 regulation in KCNQ2 encephalopathy pathogenesis, and highlight the potential usefulness of selective Kv7 openers for this distinctive pathogenic mechanism and patient subgroup.
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Affiliation(s)
- Baouyen Tran
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Zhi-Gang Ji
- Department of Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Mingxuan Xu
- Department of Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Tammy N Tsuchida
- Departments of Pediatrics and Neurology, Children's National Medical Center, Washington, DC, United States
| | - Edward C Cooper
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States.,Department of Neurology, Baylor College of Medicine, Houston, TX, United States.,Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
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8
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Kosenko A, Moftakhar S, Wood MA, Hoshi N. In Vivo Attenuation of M-Current Suppression Impairs Consolidation of Object Recognition Memory. J Neurosci 2020; 40:5847-56. [PMID: 32554550 DOI: 10.1523/JNEUROSCI.0348-20.2020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/08/2020] [Accepted: 06/06/2020] [Indexed: 11/21/2022] Open
Abstract
The M-current is a low voltage-activated potassium current generated by neuronal Kv7 channels. A prominent role of the M-current is to a create transient increase of neuronal excitability in response to neurotransmitters through the suppression of this current. Accordingly, M-current suppression is assumed to be involved in higher brain functions including learning and memory. However, there is little evidence supporting such a role to date. To address this gap, we examined behavioral tasks to assess learning and memory in homozygous Kv7.2 knock-in mice, Kv7.2(S559A), which show reduced M-current suppression while maintaining a normal basal M-current activity in neurons. We found that Kv7.2(S559A) mice had normal object location memory and contextual fear memory, but impaired long-term object recognition memory. Furthermore, short-term memory for object recognition was intact in Kv7.2(S559A) mice. The deficit in long-term object recognition memory was restored by the administration of a selective Kv7 channel inhibitor, XE991, when delivered during the memory consolidation phase. Lastly, c-Fos induction 2 h after training in Kv7.2(S559A) mice was normal in the hippocampus, which corresponds to intact object location memory, but was reduced in the perirhinal cortex, which corresponds to impaired long-term object recognition memory. Together, these results support the overall conclusion that M-current suppression is important for memory consolidation of specific types of memories.SIGNIFICANCE STATEMENT Dynamic regulation of neuronal excitation is a fundamental mechanism for information processing in the brain, which is mediated by changes in synaptic transmissions or by changes in ion channel activity. Some neurotransmitters can facilitate action potential firing by suppression of a low voltage-activated potassium current, M-current. We demonstrate that M-current suppression is critical for establishment of long-term object recognition memory, but is not required for establishment of hippocampus-dependent location memory or contextual memory. This study suggests that M-current suppression is important for stable encoding of specific types of memories.
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9
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Hui ZY, Zhang X, Sun HM, Zhou XH. [The Function of Potassium Channel in KCNQ2 G271V Mutants of Benign Familial Neonatal Convulsions]. Sichuan Da Xue Xue Bao Yi Xue Ban 2018; 49:876-880. [PMID: 32677396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
OBJECTIVE To determine the function of potassium channel in KCNQ2 G271V mutants of benign familial neonatal convulsions. METHODS HEK293 cells were transfected with pcDNA3-WT-KCNQ2 and / or pcDNA3-G271V-KCNQ2 and pcDNA3-WT-KCNQ3. The potassium channel function of G271V mutants was assessed using the whole cell patch clamp technique. RESULTS G271V mutants did not show currents in the transfected HEK cells, inducing large depolarizing shift of the conductance voltage relationship and slowing down the current activation kinetics. The required current density was (2.47±0.41) pA/pF (n=12) for the expression of G271V, and whereas (20.53±2.51) pA/pF (n=10,P<0.001) for Kv7.2. G271V mutants abolished currents in the homomeric channel. Kv7.2/Kv7.3 induced robust current was (123.68±15.21) pA/pF (n=15) and Kv7.2/G271V/Kv7.3 (42.71±6.27) pA/pF (n=10), G271V/Kv7.3 induced almost no current (3.74±0.76) pA/pF (n=10,P<0.05), resulting in about 50% reduction of currents in Kv7.2/G271V/Kv7.3 in the heteromultimeric condition. CONCLUSIONS The G271V channel fails to open potassium currents in response to depolarization, indicating a more severe functional defect of the Kv7 potassium channel.
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Affiliation(s)
- Zhi-Yan Hui
- Department of Critical Care Medicine, Yan'an University Affiliated Hospital, Yan'an 716000, China
| | - Xu Zhang
- Department of Critical Care Medicine, Yan'an University Affiliated Hospital, Yan'an 716000, China
| | - Hong-Mei Sun
- Department of Critical Care Medicine, Yan'an University Affiliated Hospital, Yan'an 716000, China
| | - Xi-Hui Zhou
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, China
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10
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Greene DL, Kosenko A, Hoshi N. Attenuating M-current suppression in vivo by a mutant Kcnq2 gene knock-in reduces seizure burden and prevents status epilepticus-induced neuronal death and epileptogenesis. Epilepsia 2018; 59:1908-1918. [PMID: 30146722 DOI: 10.1111/epi.14541] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 07/23/2018] [Accepted: 07/23/2018] [Indexed: 02/06/2023]
Abstract
OBJECTIVES The M-current is a low-threshold voltage-gated potassium current generated by Kv7 subunits that regulates neural excitation. It is important to note that M-current suppression, induced by activation of Gq-coupled neurotransmitter receptors, can dynamically regulate the threshold of action-potential firing and firing frequency. Here we sought to directly examine whether M-current suppression is involved in seizures and epileptogenesis. METHODS Kv7.2 knock-in mice lacking the key protein kinase C (PKC) phosphorylation acceptor site for M-current suppression were generated by introducing an alanine substitution at serine residue 559 of mouse Kv7.2, mKv7.2(S559A). Basic electrophysiologic properties of the M-current between wild-type and Kv7.2(S559A) knock-in mice were analyzed in primary cultured neurons. Homozygous Kv7.2(S559A) knock-in mice were used to evaluate the protective effect of mutant Kv7.2 channel against chemoconvulsant-induced seizures. In addition, pilocarpine-induced neuronal damage and spontaneously recurrent seizures were evaluated after equivalent chemoconvulsant-induced status epilepticus was achieved by coadministration of the M-current-specific channel inhibitor, XE991. RESULT Neurons from Kv7.2(S559A) knock-in mice showed normal basal M-currents. Knock-in mice displayed reduced M-current suppression when challenged by a muscarinic agonist, oxotremorine-M. Kv7.2(S559A) mice were resistant to chemoconvulsant-induced seizures with no mortality. Administration of XE991 transiently exacerbated seizures in knock-in mice equivalent to those of wild-type mice. Valproate, which disrupts neurotransmitter-induced M-current suppression, showed no additional anticonvulsant effect in Kv7.2(S559A) mice. After experiencing status epilepticus, Kv7.2(S559A) knock-in mice did not show seizure-induced cell death or spontaneous recurring seizures. SIGNIFICANCE This study provides evidence that neurotransmitter-induced suppression of M-current generated by Kv7.2-containing channels exacerbates behavioral seizures. In addition, prompt recovery of M-current after status epilepticus prevents subsequent neuronal death and the development of spontaneously recurrent seizures. Therefore, prompt restoration of M-current activity may have a therapeutic benefit for epilepsy.
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Affiliation(s)
- Derek L Greene
- Department of Pharmacology, University of California, Irvine, Irvine, California
| | - Anastasia Kosenko
- Department of Pharmacology, University of California, Irvine, Irvine, California
| | - Naoto Hoshi
- Department of Pharmacology, University of California, Irvine, Irvine, California.,Department of Physiology and Biophysics, University of California, Irvine, Irvine, California
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11
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Erdem FA, Salzer I, Heo S, Chen WQ, Jung G, Lubec G, Boehm S, Yang JW. Updating In Vivo and In Vitro Phosphorylation and Methylation Sites of Voltage-Gated Kv7.2 Potassium Channels. Proteomics 2018; 17. [PMID: 28834300 DOI: 10.1002/pmic.201700015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 07/26/2017] [Indexed: 02/04/2023]
Abstract
Voltage-gated Kv7.2 potassium channels regulate neuronal excitability. The gating of these channels is tightly controlled by various mediators and neurotransmitters acting via G protein-coupled receptors; the underlying signaling cascades involve phosphatidylinositol-4,5-bisphosphate (PIP2 ), Ca2+ /calmodulin, and phosphorylation. Recent studies found that the PIP2 sensitivity of Kv7.2 channels is affected by two posttranslational modifications, phosphorylation and methylation, harboured within putative PIP2 -binding domains. In this study, we updated phosphorylation and methylation sites in Kv7.2 either heterologously expressed in mammalian cells or as GST-fusion proteins exposed to recombinant protein kinases by using LC-MS/MS. In vitro kinase assays revealed that CDK5, protein kinase C (PKC) alpha, PKA, p38 MAPK, CamKIIα, and GSK3β could mediate phosphorylation. Taken together, we provided a comprehensive map of phosphorylation and methylation in Kv7.2 within protein-protein and protein-lipid interaction domains. This may help to interpret the functional roles of individual PTM sites in Kv7.2 channels. All MS data are available via ProteomeXchange with the identifier PXD005567.
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Affiliation(s)
- Fatma Asli Erdem
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Isabella Salzer
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Seok Heo
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Wei-Qiang Chen
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gangsoo Jung
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Neuroproteomics, Paracelsus Medical University of Salzburg, Salzburg, Austria
| | - Stefan Boehm
- Department of Neurophysiology and Neuropharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jae-Won Yang
- Institute of Pharmacology, Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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12
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Valdor M, Wagner A, Röhrs V, Berg J, Fechner H, Schröder W, Tzschentke TM, Bahrenberg G, Christoph T, Kurreck J. RNA interference-based functional knockdown of the voltage-gated potassium channel Kv7.2 in dorsal root ganglion neurons after in vitro and in vivo gene transfer by adeno-associated virus vectors. Mol Pain 2017; 14:1744806917749669. [PMID: 29212407 PMCID: PMC5805000 DOI: 10.1177/1744806917749669] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Activation of the neuronal potassium channel Kv7.2 encoded by the KCNQ2 gene has recently been shown to be an attractive mechanism to inhibit nociceptive transmission. However, potent, selective, and clinically proven activators of Kv7.2/Kv7.3 currents with analgesic properties are still lacking. An important prerequisite for the development of new drugs is a model to test the selectivity of novel agonists by abrogating Kv7.2/Kv7.3 function. Since constitutive knockout mice are not viable, we developed a model based on RNA interference-mediated silencing of KCNQ2. By delivery of a KCNQ2-specific short hairpin RNA with adeno-associated virus vectors, we completely abolished the activity of the specific Kv7.2/Kv7.3-opener ICA-27243 in rat sensory neurons. Results obtained in the silencing experiments were consistent between freshly prepared and cryopreserved dorsal root ganglion neurons, as well as in dorsal root ganglion neurons dissociated and cultured after in vivo administration of the silencing vector by intrathecal injections into rats. Interestingly, the tested associated virus serotypes substantially differed with respect to their transduction capability in cultured neuronal cell lines and primary dorsal root ganglion neurons and the in vivo transfer of transgenes by intrathecal injection of associated virus vectors. However, our study provides the proof-of-concept that RNA interference-mediated silencing of KCNQ2 is a suitable approach to create an ex vivo model for testing the specificity of novel Kv7.2/Kv7.3 agonists.
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Affiliation(s)
- Markus Valdor
- 1 14938 Grünenthal GmbH , Pharmacology and Biomarker Development, Aachen, Germany
| | - Anke Wagner
- 2 Department of Applied Biochemistry, Institute of Biotechnology, Berlin University of Technology, Berlin, Germany
| | - Viola Röhrs
- 2 Department of Applied Biochemistry, Institute of Biotechnology, Berlin University of Technology, Berlin, Germany
| | - Johanna Berg
- 2 Department of Applied Biochemistry, Institute of Biotechnology, Berlin University of Technology, Berlin, Germany
| | - Henry Fechner
- 2 Department of Applied Biochemistry, Institute of Biotechnology, Berlin University of Technology, Berlin, Germany
| | - Wolfgang Schröder
- 1 14938 Grünenthal GmbH , Pharmacology and Biomarker Development, Aachen, Germany
| | - Thomas M Tzschentke
- 1 14938 Grünenthal GmbH , Pharmacology and Biomarker Development, Aachen, Germany
| | | | - Thomas Christoph
- 1 14938 Grünenthal GmbH , Pharmacology and Biomarker Development, Aachen, Germany
| | - Jens Kurreck
- 2 Department of Applied Biochemistry, Institute of Biotechnology, Berlin University of Technology, Berlin, Germany
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Ambrosino P, Alaimo A, Bartollino S, Manocchio L, De Maria M, Mosca I, Gomis-Perez C, Alberdi A, Scambia G, Lesca G, Villarroel A, Taglialatela M, Soldovieri MV. Epilepsy-causing mutations in Kv7.2 C-terminus affect binding and functional modulation by calmodulin. Biochim Biophys Acta Mol Basis Dis 2015; 1852:1856-66. [PMID: 26073431 DOI: 10.1016/j.bbadis.2015.06.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 05/14/2015] [Accepted: 06/08/2015] [Indexed: 11/21/2022]
Abstract
Mutations in the KCNQ2 gene, encoding for voltage-gated Kv7.2K(+) channel subunits, are responsible for early-onset epileptic diseases with widely-diverging phenotypic presentation, ranging from Benign Familial Neonatal Seizures (BFNS) to epileptic encephalopathy. In the present study, Kv7.2 BFNS-causing mutations (W344R, L351F, L351V, Y362C, and R553Q) have been investigated for their ability to interfere with calmodulin (CaM) binding and CaM-induced channel regulation. To this aim, semi-quantitative (Far-Western blotting) and quantitative (Surface Plasmon Resonance and dansylated CaM fluorescence) biochemical assays have been performed to investigate the interaction of CaM with wild-type or mutant Kv7.2 C-terminal fragments encompassing the CaM-binding domain; in parallel, mutation-induced changes in CaM-dependent Kv7.2 or Kv7.2/Kv7.3 current regulation were investigated by patch-clamp recordings in Chinese Hamster Ovary (CHO) cells co-expressing Kv7.2 or Kv7.2/Kv7.3 channels and CaM or CaM1234 (a CaM isoform unable to bind Ca(2+)). The results obtained suggest that each BFNS-causing mutation prompts specific biochemical and/or functional consequences; these range from slight alterations in CaM affinity which did not translate into functional changes (L351V), to a significant reduction in the affinity and functional modulation by CaM (L351F, Y362C or R553Q), to a complete functional loss without significant alteration in CaM affinity (W344R). CaM overexpression increased Kv7.2 and Kv7.2/Kv7.3 current levels, and partially (R553Q) or fully (L351F) restored normal channel function, providing a rationale pathogenetic mechanism for mutation-induced channel dysfunction in BFNS, and highlighting the potentiation of CaM-dependent Kv7.2 modulation as a potential therapeutic approach for Kv7.2-related epilepsies.
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Wang J, Li Y, Hui Z, Cao M, Shi R, Zhang W, Geng L, Zhou X. Functional analysis of potassium channels in Kv7.2 G271V mutant causing early onset familial epilepsy. Brain Res 2015; 1616:112-22. [PMID: 25960349 DOI: 10.1016/j.brainres.2015.04.060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2014] [Revised: 04/20/2015] [Accepted: 04/24/2015] [Indexed: 01/23/2023]
Abstract
Kv7 (KCNQ) channels underlying a class of voltage-gated K+ current are best known for regulating neuronal excitability. The first glycine (G) residue in the pore helix of Kv7.2 (KCNQ2) subunit is highly conserved among different classes of Kv7 channel family. A missense mutation causing the replacement of the corresponding G residues with a valine (p.G271V) in Kv7.2 was found in a large, four-generation pedigree. Here, we set out to examine the molecular pathomechanism of G271V mutants using patch clamp technology combined with biochemical and immunocytochemical techniques in transiently transfected human embryonic kidney (HEK) 293 cells. The expression of Kv7.2 protein had the same intensity for both wild type (WT) and G271V. In transfected HEK cells, G271V mutants induced large depolarizing shifts of the conductance-voltage relationships and marked slowing of current activation kinetics compared to WT. In addition, G271V mutants abolished currents in homomeric channels, and resulted in about 50% reduction of current in Kv7.2/G271V/Kv7.3 heteromultimeric condition, indicating a more severe functional defect. To test for G271V mutant channel expression in surface membrane, we performed fluorescence confocal microscopy imaging, which revealed no differences between the mutant and WT, suggesting that G271V channels fail to open in response to depolarization even though they are present in the membrane. Furthermore, pharmacologic intervention experiments revealed that upon specific incubation of transfected HEK 293 cells expressing G271V heteromultimeric channels in presence of Kv7 channel enhancer retigabine (ezogabine), the potassium currents increased significantly, suggesting the potential of retigabine as gene-specific therapy.
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Affiliation(s)
- Juanjuan Wang
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Yuan Li
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Zhiyan Hui
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Min Cao
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Ruiming Shi
- Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Wei Zhang
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Limeng Geng
- Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China
| | - Xihui Zhou
- Department of Neonatology, First Affiliated Hospital of Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China; Ion Channel Disease Laboratory, Key Laboratory of Environment and Gene Associated Diseases, Ministry of Education, Xi'an Jiaotong University, No. 277, Yanta West Road, Xi'an, Shaanxi 710061, People's Republic of China.
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Wu YJ, Conway CM, Sun LQ, Machet F, Chen J, Chen P, He H, Bourin C, Calandra V, Polino JL, Davis CD, Heman K, Gribkoff VK, Boissard CG, Knox RJ, Thompson MW, Fitzpatrick W, Weaver D, Harden DG, Natale J, Dworetzky SI, Starrett JE. Discovery of (S,E)-3-(2-fluorophenyl)-N-(1-(3-(pyridin-3-yloxy)phenyl)ethyl)-acrylamide as a potent and efficacious KCNQ2 ( Kv7.2) opener for the treatment of neuropathic pain. Bioorg Med Chem Lett 2013; 23:6188-91. [PMID: 24070783 DOI: 10.1016/j.bmcl.2013.08.092] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2013] [Accepted: 08/26/2013] [Indexed: 12/21/2022]
Abstract
Acrylamide (S)-6, a potent and efficacious KCNQ2 (Kv7.2) opener, demonstrated significant activity in two models of neuropathic pain and in the formalin test, suggesting that KCNQ2 openers may be useful in the treatment of neuropathic pain including diabetic neuropathy.
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Affiliation(s)
- Yong-Jin Wu
- Research and Development, Bristol-Myers Squibb Company, 5 Research Parkway, Wallingford, CT 06492, USA.
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