1
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Lin H, Li J, Zhang Q, Yang H, Chen S. C-type inactivation and proton modulation mechanisms of the TASK3 channel. Proc Natl Acad Sci U S A 2024; 121:e2320345121. [PMID: 38630723 PMCID: PMC11046659 DOI: 10.1073/pnas.2320345121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/19/2024] [Indexed: 04/19/2024] Open
Abstract
The TWIK-related acid-sensitive K+ channel 3 (TASK3) belongs to the two-pore domain (K2P) potassium channel family, which regulates cell excitability by mediating a constitutive "leak" potassium efflux in the nervous system. Extracellular acidification inhibits TASK3 channel, but the molecular mechanism by which channel inactivation is coupled to pH decrease remains unclear. Here, we report the cryo-electron microscopy structures of human TASK3 at neutral and acidic pH. Structural comparison revealed selectivity filter (SF) rearrangements upon acidification, characteristic of C-type inactivation, but with a unique structural basis. The extracellular mouth of the SF was prominently dilated and simultaneously blocked by a hydrophobic gate. His98 protonation shifted the conformational equilibrium between the conductive and C-type inactivated SF toward the latter by engaging a cation-π interaction with Trp78, consistent with molecular dynamics simulations and electrophysiological experiments. Our work illustrated how TASK3 is gated in response to extracellular pH change and implies how physiological stimuli might directly modulate the C-type gating of K2P channels.
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Affiliation(s)
- Huajian Lin
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
| | - Junnan Li
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Qiansen Zhang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Huaiyu Yang
- Shanghai Key Laboratory of Regulatory Biology, Institute of Biomedical Sciences, School of Life Sciences, East China Normal University, Shanghai200241, China
| | - Shanshuang Chen
- Shanghai Institute of Precision Medicine, Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai200125, China
- Department of Otolaryngology-Head and Neck Surgery, Ninth People’s Hospital, Shanghai200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai200125, China
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2
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Lai H, Gao M, Yang H. The potassium channels: Neurobiology and pharmacology of tinnitus. J Neurosci Res 2024; 102:e25281. [PMID: 38284861 DOI: 10.1002/jnr.25281] [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: 04/23/2023] [Revised: 10/27/2023] [Accepted: 11/16/2023] [Indexed: 01/30/2024]
Abstract
Tinnitus is a widespread public health issue that imposes a significant social burden. The occurrence and maintenance of tinnitus have been shown to be associated with abnormal neuronal activity in the auditory pathway. Based on this view, neurobiological and pharmacological developments in tinnitus focus on ion channels and synaptic neurotransmitter receptors in neurons in the auditory pathway. With major breakthroughs in the pathophysiology and research methodology of tinnitus in recent years, the role of the largest family of ion channels, potassium ion channels, in modulating the excitability of neurons involved in tinnitus has been increasingly demonstrated. More and more potassium channels involved in the neural mechanism of tinnitus have been discovered, and corresponding drugs have been developed. In this article, we review animal (mouse, rat, hamster, and guinea-pig), human, and genetic studies on the different potassium channels involved in tinnitus, analyze the limitations of current clinical research on potassium channels, and propose future prospects. The aim of this review is to promote the understanding of the role of potassium ion channels in tinnitus and to advance the development of drugs targeting potassium ion channels for tinnitus.
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Affiliation(s)
- Haohong Lai
- Department of Otolaryngology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Minqian Gao
- Department of Otolaryngology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
- Department of Hearing and Speech-Language Science, Guangzhou Xinhua University, Guangzhou, China
| | - Haidi Yang
- Department of Otolaryngology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
- Department of Hearing and Speech-Language Science, Guangzhou Xinhua University, Guangzhou, China
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3
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Lim WM, Chin EWM, Tang BL, Chen T, Goh ELK. WNK3 Maintains the GABAergic Inhibitory Tone, Synaptic Excitation and Neuronal Excitability via Regulation of KCC2 Cotransporter in Mature Neurons. Front Mol Neurosci 2021; 14:762142. [PMID: 34858138 PMCID: PMC8631424 DOI: 10.3389/fnmol.2021.762142] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 10/14/2021] [Indexed: 11/13/2022] Open
Abstract
The activation of chloride (Cl−)permeable gamma (γ)-aminobutyric acid type A(GABAA) receptors induces synaptic inhibition in mature and excitation in immature neurons. This developmental “switch” in GABA function controlled by its polarity depends on the postnatal decrease in intraneuronal Cl− concentration mediated by KCC2, a member of cation-chloride cotransporters (CCCs). The serine-threonine kinase WNK3 (With No Lysine [K]), is a potent regulator of all CCCs and is expressed in neurons. Here, we characterized the functions of WNK3 and its role in GABAergic signaling in cultured embryonic day 18 (E18) hippocampal neurons. We observed a decrease in WNK3 expression as neurons mature. Knocking down of WNK3 significantly hyperpolarized EGABA in mature neurons (DIV13–15) but had no effect on immature neurons (DIV6–8). This hyperpolarized EGABA in WNK3-deficient neurons was not due to the total expression of NKCC1 and KCC2, that remained unchanged. However, there was a reduction in phosphorylated KCC2 at the membrane, suggesting an increase in KCC2 chloride export activity. Furthermore, hyperpolarized EGABA observed in WNK3-deficient neurons can be reversed by the KCC2 inhibitor, VU024055, thus indicating that WNK3 acts through KCC2 to influence EGABA. Notably, WNK3 knockdown resulted in morphological changes in mature but not immature neurons. Electrophysiological characterization of WNK3-deficient mature neurons revealed reduced capacitances but increased intrinsic excitability and synaptic excitation. Hence, our study demonstrates that WNK3 maintains the “adult” GABAergic inhibitory tone in neurons and plays a role in the morphological development of neurons and excitability.
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Affiliation(s)
- Wee Meng Lim
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, Singapore, Singapore
| | - Eunice W M Chin
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore.,NUS Graduate School for Integrative Sciences and Engineering, Singapore, Singapore.,Neuroscience and Mental Health Faculty, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Bor Luen Tang
- NUS Graduate School for Integrative Sciences and Engineering, Singapore, Singapore.,Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Tingting Chen
- School of Pharmacy, Nantong University, Nantong, China
| | - Eyleen L K Goh
- Neuroscience Academic Clinical Programme, Duke-NUS Medical School, Singapore, Singapore.,Neuroscience and Mental Health Faculty, Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
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4
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Two-Pore-Domain Potassium (K 2P-) Channels: Cardiac Expression Patterns and Disease-Specific Remodelling Processes. Cells 2021; 10:cells10112914. [PMID: 34831137 PMCID: PMC8616229 DOI: 10.3390/cells10112914] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/18/2021] [Accepted: 10/22/2021] [Indexed: 12/23/2022] Open
Abstract
Two-pore-domain potassium (K2P-) channels conduct outward K+ currents that maintain the resting membrane potential and modulate action potential repolarization. Members of the K2P channel family are widely expressed among different human cell types and organs where they were shown to regulate important physiological processes. Their functional activity is controlled by a broad variety of different stimuli, like pH level, temperature, and mechanical stress but also by the presence of lipids or pharmacological agents. In patients suffering from cardiovascular diseases, alterations in K2P-channel expression and function have been observed, suggesting functional significance and a potential therapeutic role of these ion channels. For example, upregulation of atrial specific K2P3.1 (TASK-1) currents in atrial fibrillation (AF) patients was shown to contribute to atrial action potential duration shortening, a key feature of AF-associated atrial electrical remodelling. Therefore, targeting K2P3.1 (TASK-1) channels might constitute an intriguing strategy for AF treatment. Further, mechanoactive K2P2.1 (TREK-1) currents have been implicated in the development of cardiac hypertrophy, cardiac fibrosis and heart failure. Cardiovascular expression of other K2P channels has been described, functional evidence in cardiac tissue however remains sparse. In the present review, expression, function, and regulation of cardiovascular K2P channels are summarized and compared among different species. Remodelling patterns, observed in disease models are discussed and compared to findings from clinical patients to assess the therapeutic potential of K2P channels.
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5
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Wu J, Kaczmarek LK. Modulation of Neuronal Potassium Channels During Auditory Processing. Front Neurosci 2021; 15:596478. [PMID: 33613177 PMCID: PMC7887315 DOI: 10.3389/fnins.2021.596478] [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: 08/19/2020] [Accepted: 01/11/2021] [Indexed: 11/16/2022] Open
Abstract
The extraction and localization of an auditory stimulus of interest from among multiple other sounds, as in the ‘cocktail-party’ situation, requires neurons in auditory brainstem nuclei to encode the timing, frequency, and intensity of sounds with high fidelity, and to compare inputs coming from the two cochleae. Accurate localization of sounds requires certain neurons to fire at high rates with high temporal accuracy, a process that depends heavily on their intrinsic electrical properties. Studies have shown that the membrane properties of auditory brainstem neurons, particularly their potassium currents, are not fixed but are modulated in response to changes in the auditory environment. Here, we review work focusing on how such modulation of potassium channels is critical to shaping the firing pattern and accuracy of these neurons. We describe how insights into the role of specific channels have come from human gene mutations that impair localization of sounds in space. We also review how short-term and long-term modulation of these channels maximizes the extraction of auditory information, and how errors in the regulation of these channels contribute to deficits in decoding complex auditory information.
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Affiliation(s)
- Jing Wu
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, United States
| | - Leonard K Kaczmarek
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, United States
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6
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Li Z, Ma Y, Zhou F, Jia X, Zhan J, Tan H, Wang X, Yang T, Liu Q. Identification of MicroRNA-Potassium Channel Messenger RNA Interactions in the Brain of Rats With Post-traumatic Epilepsy. Front Mol Neurosci 2021; 13:610090. [PMID: 33597846 PMCID: PMC7882489 DOI: 10.3389/fnmol.2020.610090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 12/21/2020] [Indexed: 12/14/2022] Open
Abstract
Background: Dysregulated expression of microRNAs and potassium channels have been reported for their contributions to seizure onset. However, the microRNA–potassium channel gene interactions in traumatic brain injury-induced post-traumatic epilepsy (PTE) remain unknown. Methods: PTE was induced in male rats by intracranial injection with ferrous chloride (0.1 mol/L, 1 μl/min) at the right frontal cortex. Electroencephalography was recorded at 60 min, as well as day 1, 7, and 30, and the behavioral seizures were assessed before injection and at different time points after injection. Rats were killed on day 30 after injection. The right frontal cortex samples were collected and subjected to high throughput messenger RNA (mRNA) and microRNA sequencing. A network of differentially expressed potassium channel mRNAs and microRNAs was constructed using OryCun2.0 and subjected to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. The differential mRNA and microRNA expressions were verified using quantitative real-time-PCR. The microRNA–mRNA was subject to the Pearson correlation analysis. Results: A PTE rat model was successfully established, as evidenced by behavioral seizures and epileptiform discharges on electroencephalography in PTE rats compared with sham rats. Among the 91 mRNAs and 40 microRNAs that were significantly differentially expressed in the PTE rat brain, 4 mRNAs and 10 microRNAs were associated with potassium channels. Except for potassium calcium-activated channel subfamily N member 2, the other three potassium channel mRNAs were negatively correlated with seven microRNAs. These microRNA–mRNA pairs were enriched in annotations and pathways related to neuronal ion channels and neuroinflammation. Quantitative real-time-PCR and correlation analysis verified negative correlations in miR-449a-5p-KCNH2, miR-98-5p-KCNH2, miR-98-5p-KCNK15, miR-19b-3p-KCNK15, and miR-301a-3p-KCNK15 pairs. Conclusion: We identified microRNA–potassium channel mRNA interactions associated with PTE, providing potential diagnostic markers and therapeutic targets for PTE.
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Affiliation(s)
- Zheng Li
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Yixun Ma
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Fengjuan Zhou
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Xiao Jia
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Jingjing Zhan
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Huachao Tan
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Xu Wang
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Tiantong Yang
- Key Laboratory of Evidence Science, Institute of Evidence Law and Forensic Science, China University of Political Science and Law, Ministry of Education, Beijing, China.,Collaborative Innovation Center of Judicial Civilization, Beijing, China
| | - Quan Liu
- Hubei University of Police, Wuhan, China
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7
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Ceder MM, Aggarwal T, Hosseini K, Maturi V, Patil S, Perland E, Williams MJ, Fredriksson R. CG4928 Is Vital for Renal Function in Fruit Flies and Membrane Potential in Cells: A First In-Depth Characterization of the Putative Solute Carrier UNC93A. Front Cell Dev Biol 2020; 8:580291. [PMID: 33163493 PMCID: PMC7591606 DOI: 10.3389/fcell.2020.580291] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Accepted: 09/16/2020] [Indexed: 01/23/2023] Open
Abstract
The number of transporter proteins that are not fully characterized is immense. Here, we used Drosophila melanogaster and human cell lines to perform a first in-depth characterization of CG4928, an ortholog to the human UNC93A, of which little is known. Solute carriers regulate and maintain biochemical pathways important for the body, and malfunctioning transport is associated with multiple diseases. Based on phylogenetic analysis, CG4928 is closely related to human UNC93A and has a secondary and a tertiary protein structure and folding similar to major facilitator superfamily transporters. Ubiquitous knockdown of CG4928 causes flies to have a reduced secretion rate from the Malpighian tubules; altering potassium content in the body and in the Malpighian tubules, homologous to the renal system; and results in the development of edema. The edema could be rescued by using amiloride, a common diuretic, and by maintaining the flies on ion-free diets. CG4928-overexpressing cells did not facilitate the transport of sugars and amino acids; however, proximity ligation assay revealed that CG4928 co-localized with TASK1 channels. Overexpression of CG4928 resulted in induced apoptosis and cytotoxicity, which could be restored when cells were kept in high-sodium media. Furthermore, the basal membrane potential was observed to be disrupted. Taken together, the results indicate that CG4928 is of importance for generating the cellular membrane potential by an unknown manner. However, we speculate that it most likely acts as a regulator or transporter of potassium flows over the membrane.
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Affiliation(s)
- Mikaela M Ceder
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Tanya Aggarwal
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Kimia Hosseini
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Varun Maturi
- Department of Pharmacy, Drug Delivery, Uppsala University, Uppsala, Sweden
| | - Sourabh Patil
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Emelie Perland
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
| | - Michael J Williams
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
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8
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Ceder MM, Lekholm E, Klaesson A, Tripathi R, Schweizer N, Weldai L, Patil S, Fredriksson R. Glucose Availability Alters Gene and Protein Expression of Several Newly Classified and Putative Solute Carriers in Mice Cortex Cell Culture and D. melanogaster. Front Cell Dev Biol 2020; 8:579. [PMID: 32733888 PMCID: PMC7358622 DOI: 10.3389/fcell.2020.00579] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 06/15/2020] [Indexed: 12/16/2022] Open
Abstract
Many newly identified solute carriers (SLCs) and putative transporters have the possibility to be intricately involved in glucose metabolism. Here we show that many transporters of this type display a high degree of regulation at both mRNA and protein level following no or low glucose availability in mouse cortex cultures. We show that this is also the case in Drosophila melanogaster subjected to starvation or diets with different sugar content. Interestingly, re-introduction of glucose to media, or refeeding flies, normalized the gene expression of a number of the targets, indicating a fast and highly dynamic control. Our findings demonstrate high conservation of these transporters and how dependent both cell cultures and organisms are on gene and protein regulation during metabolic fluctuations. Several transporter genes were regulated simultaneously maybe to initiate alternative metabolic pathways as a response to low glucose levels, both in the cell cultures and in D. melanogaster. Our results display that newly identified SLCs of Major Facilitator Superfamily type, as well as the putative transporters included in our study, are regulated by glucose availability and could be involved in several cellular aspects dependent of glucose and/or its metabolites. Recently, a correlation between dysregulation of glucose in the central nervous system and numerous diseases such as obesity, type 2 diabetes mellitus as well as neurological disease such as Alzheimer’s and Parkinson’s diseases indicate a complex regulation and fine tuning of glucose levels in the brain. The fact that almost one third of transporters and transporter-related proteins remain orphans with unknown or contradictive substrate profile, location and function, pinpoint the need for further research about them to fully understand their mechanistic role and their impact on cellular metabolism.
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Affiliation(s)
- Mikaela M Ceder
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Emilia Lekholm
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Axel Klaesson
- Pharmaceutical Cell Biology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Rekha Tripathi
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Nadine Schweizer
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Lydia Weldai
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Sourabh Patil
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
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9
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A lower X-gate in TASK channels traps inhibitors within the vestibule. Nature 2020; 582:443-447. [PMID: 32499642 DOI: 10.1038/s41586-020-2250-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 03/12/2020] [Indexed: 12/23/2022]
Abstract
TWIK-related acid-sensitive potassium (TASK) channels-members of the two pore domain potassium (K2P) channel family-are found in neurons1, cardiomyocytes2-4 and vascular smooth muscle cells5, where they are involved in the regulation of heart rate6, pulmonary artery tone5,7, sleep/wake cycles8 and responses to volatile anaesthetics8-11. K2P channels regulate the resting membrane potential, providing background K+ currents controlled by numerous physiological stimuli12-15. Unlike other K2P channels, TASK channels are able to bind inhibitors with high affinity, exceptional selectivity and very slow compound washout rates. As such, these channels are attractive drug targets, and TASK-1 inhibitors are currently in clinical trials for obstructive sleep apnoea and atrial fibrillation16. In general, potassium channels have an intramembrane vestibule with a selectivity filter situated above and a gate with four parallel helices located below; however, the K2P channels studied so far all lack a lower gate. Here we present the X-ray crystal structure of TASK-1, and show that it contains a lower gate-which we designate as an 'X-gate'-created by interaction of the two crossed C-terminal M4 transmembrane helices at the vestibule entrance. This structure is formed by six residues (243VLRFMT248) that are essential for responses to volatile anaesthetics10, neurotransmitters13 and G-protein-coupled receptors13. Mutations within the X-gate and the surrounding regions markedly affect both the channel-open probability and the activation of the channel by anaesthetics. Structures of TASK-1 bound to two high-affinity inhibitors show that both compounds bind below the selectivity filter and are trapped in the vestibule by the X-gate, which explains their exceptionally low washout rates. The presence of the X-gate in TASK channels explains many aspects of their physiological and pharmacological behaviour, which will be beneficial for the future development and optimization of TASK modulators for the treatment of heart, lung and sleep disorders.
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10
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Genetic variants of rs1275988 and rs2586886 in TWIK-related acid-sensitive K+ channel-1 gene may be potential risk factors for obese patients with obstructive sleep apnea. Chin Med J (Engl) 2020; 132:2059-2065. [PMID: 31436597 PMCID: PMC6793785 DOI: 10.1097/cm9.0000000000000401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background: The pathogenesis of obstructive sleep apnea (OSA) remains not fully understood. This study aimed to explore the mechanism of OSA by assessing the association between the human tandem of P domains in a weak inwardly rectifying K+ channel (TWIK)-related acid-sensitive K+ channel-1 (TASK-1) gene and OSA. Methods: A total of 164 patients with severe OSA and 171 patients without OSA were recruited from the Center for Hypertension of People's Hospital of Xinjiang Uygur Autonomous Region (China) from April to December in 2016. Two single nucleotide polymorphisms (rs1275988 and rs2586886) in the TASK-1 gene were selected and genotyped using a kompetitive allele specific polymerase chain reaction genotyping system. Clinical-pathological characteristics and genotype data were compared between the severe and non-OSA groups to explore the association between TASK-1 gene polymorphism and severe OSA. Results: There were no significant differences in genotype distribution, allele frequency, and the recessive and dominant model of the two selected single nucleotide polymorphisms (rs1275988 and rs2586886) between the severe and non-OSA groups in the total population (P > 0.05). However, for patients with a body mass index (BMI) ≥28 kg/m2, the distribution of genotypes and alleles, and the recessive model (GG + GA vs. AA) exhibited significant differences between the severe and non-OSA group (for genotypes: P = 0.014 and P = 0.026; for alleles: P = 0.006 and P = 0.011; for the recessive model: P = 0.005 and P = 0.009, respectively). The simple logistic regression analysis revealed that the GG genotype was a risk factor for OSA. The odds ratio (OR) and 95% confidence intervals (CI) were 4.902 (1.582–15.186, P = 0.006) for rs1275988 and 4.420 (1.422–13.734, P = 0.010) for rs2586886, respectively. In multivariate logistic regression analysis, the combination of GG genotypes of rs1275988 with BMI ≥28 kg/m2 increased the risk of severe OSA (OR = 8.916, 95% CI 4.506–17.645, P < 0.001). Conclusion: Both the GG genotype of rs1275988 and GG genotype of rs2586886 in the TASK-1 gene may play as potential risk factors in obese patients with OSA.
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11
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Bedoya M, Rinné S, Kiper AK, Decher N, González W, Ramírez D. TASK Channels Pharmacology: New Challenges in Drug Design. J Med Chem 2019; 62:10044-10058. [PMID: 31260312 DOI: 10.1021/acs.jmedchem.9b00248] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Rational drug design targeting ion channels is an exciting and always evolving research field. New medicinal chemistry strategies are being implemented to explore the wild chemical space and unravel the molecular basis of the ion channels modulators binding mechanisms. TASK channels belong to the two-pore domain potassium channel family and are modulated by extracellular acidosis. They are extensively distributed along the cardiovascular and central nervous systems, and their expression is up- and downregulated in different cancer types, which makes them an attractive therapeutic target. However, TASK channels remain unexplored, and drugs designed to target these channels are poorly selective. Here, we review TASK channels properties and their known blockers and activators, considering the new challenges in ion channels drug design and focusing on the implementation of computational methodologies in the drug discovery process.
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Affiliation(s)
- Mauricio Bedoya
- Centro de Bioinformática y Simulación Molecular (CBSM) , Universidad de Talca , 1 Poniente No. 1141 , 3460000 Talca , Chile
| | - Susanne Rinné
- Institute for Physiology and Pathophysiology, Vegetative Physiology and Marburg Center for Mind, Brain and Behavior, MCMBB , Philipps-University of Marburg , Deutschhausstraße 2 , Marburg 35037 , Germany
| | - Aytug K Kiper
- Institute for Physiology and Pathophysiology, Vegetative Physiology and Marburg Center for Mind, Brain and Behavior, MCMBB , Philipps-University of Marburg , Deutschhausstraße 2 , Marburg 35037 , Germany
| | - Niels Decher
- Institute for Physiology and Pathophysiology, Vegetative Physiology and Marburg Center for Mind, Brain and Behavior, MCMBB , Philipps-University of Marburg , Deutschhausstraße 2 , Marburg 35037 , Germany
| | - Wendy González
- Centro de Bioinformática y Simulación Molecular (CBSM) , Universidad de Talca , 1 Poniente No. 1141 , 3460000 Talca , Chile.,Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD) , Universidad de Talca , 1 Poniente No. 1141 , 3460000 Talca , Chile
| | - David Ramírez
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud , Universidad Autónoma de Chile , El Llano Subercaseaux 2801, Piso 6 , 8900000 Santiago , Chile
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12
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Goutierre M, Al Awabdh S, Donneger F, François E, Gomez-Dominguez D, Irinopoulou T, Menendez de la Prida L, Poncer JC. KCC2 Regulates Neuronal Excitability and Hippocampal Activity via Interaction with Task-3 Channels. Cell Rep 2019; 28:91-103.e7. [PMID: 31269453 DOI: 10.1016/j.celrep.2019.06.001] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 04/18/2019] [Accepted: 05/30/2019] [Indexed: 10/26/2022] Open
Abstract
KCC2 regulates neuronal transmembrane chloride gradients and thereby controls GABA signaling in the brain. KCC2 downregulation is observed in numerous neurological and psychiatric disorders. Paradoxical, excitatory GABA signaling is usually assumed to contribute to abnormal network activity underlying the pathology. We tested this hypothesis and explored the functional impact of chronic KCC2 downregulation in the rat dentate gyrus. Although the reversal potential of GABAA receptor currents is depolarized in KCC2 knockdown neurons, this shift is compensated by depolarization of the resting membrane potential. This reflects downregulation of leak potassium currents. We show KCC2 interacts with Task-3 (KCNK9) channels and is required for their membrane expression. Increased neuronal excitability upon KCC2 suppression altered dentate gyrus rhythmogenesis, which could be normalized by chemogenetic hyperpolarization. Our data reveal KCC2 downregulation engages complex synaptic and cellular alterations beyond GABA signaling that perturb network activity thus offering additional targets for therapeutic intervention.
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Affiliation(s)
- Marie Goutierre
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France
| | - Sana Al Awabdh
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France
| | - Florian Donneger
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France
| | - Emeline François
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France
| | - Daniel Gomez-Dominguez
- Instituto Cajal, Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28002, Spain
| | - Theano Irinopoulou
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France
| | | | - Jean Christophe Poncer
- INSERM UMR-S 1270, 75005 Paris, France; Sorbonne Université, 75005 Paris, France; Institut du Fer à Moulin, 75005 Paris, France.
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13
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Zobeiri M, Chaudhary R, Blaich A, Rottmann M, Herrmann S, Meuth P, Bista P, Kanyshkova T, Lüttjohann A, Narayanan V, Hundehege P, Meuth SG, Romanelli MN, Urbano FJ, Pape HC, Budde T, Ludwig A. The Hyperpolarization-Activated HCN4 Channel is Important for Proper Maintenance of Oscillatory Activity in the Thalamocortical System. Cereb Cortex 2019; 29:2291-2304. [PMID: 30877792 PMCID: PMC6458902 DOI: 10.1093/cercor/bhz047] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 02/15/2019] [Accepted: 02/21/2019] [Indexed: 11/14/2022] Open
Abstract
Hyperpolarization-activated cation channels are involved, among other functions, in learning and memory, control of synaptic transmission and epileptogenesis. The importance of the HCN1 and HCN2 isoforms for brain function has been demonstrated, while the role of HCN4, the third major neuronal HCN subunit, is not known. Here we show that HCN4 is essential for oscillatory activity in the thalamocortical (TC) network. HCN4 is selectively expressed in various thalamic nuclei, excluding the thalamic reticular nucleus. HCN4-deficient TC neurons revealed a massive reduction of Ih and strongly reduced intrinsic burst firing, whereas the current was normal in cortical pyramidal neurons. In addition, evoked bursting in a thalamic slice preparation was strongly reduced in the mutant mice probes. HCN4-deficiency also significantly slowed down thalamic and cortical oscillations during active wakefulness. Taken together, these results establish that thalamic HCN4 channels are essential for the production of rhythmic intrathalamic oscillations and determine regular TC oscillatory activity during alert states.
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Affiliation(s)
- Mehrnoush Zobeiri
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Rahul Chaudhary
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Anne Blaich
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Matthias Rottmann
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Stefan Herrmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Patrick Meuth
- Klinik für Neurologie mit Institut für Translationale Neurologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - Pawan Bista
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Tatyana Kanyshkova
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Annika Lüttjohann
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Venu Narayanan
- Klinik für Neurologie mit Institut für Translationale Neurologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - Petra Hundehege
- Klinik für Neurologie mit Institut für Translationale Neurologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - Sven G Meuth
- Klinik für Neurologie mit Institut für Translationale Neurologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - Maria Novella Romanelli
- Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence, Via Ugo Schiff 6, Sesto Fiorentino, Italy
| | | | - Hans-Christian Pape
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Thomas Budde
- Institut für Physiologie I, Westfälische Wilhelms-Universität, Münster, Germany
| | - Andreas Ludwig
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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14
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Li WY, Wang A, Jin H, Zou Y, Wang Z, Wang W, Kang J. Transient upregulation of TASK-1 expression in the hypoglossal nucleus during chronic intermittent hypoxia is reduced by serotonin 2A receptor antagonist. J Cell Physiol 2019; 234:17886-17895. [PMID: 30864194 DOI: 10.1002/jcp.28419] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 02/10/2019] [Accepted: 02/14/2019] [Indexed: 11/11/2022]
Abstract
Hypoglossal motoneurons innervate genioglossus muscle, the contraction of which is critical in the maintenance of upper airway patency in patients with obstructive sleep apnea. As a potassium channel distributed in hypoglossal motoneurons, TWIK-related acid-sensitive K+ channel-1 (TASK-1) could be inhibited by 5-HT. This study aimed to investigate if TASK-1 expression in hypoglossal nucleus could be influenced by chronic intermittent hypoxia (CIH) and 5-HT2A receptors antagonist. Two hundred twenty-eight rats were exposed to CIH or normoxia (NO) in the presence and absence of 5-HT 2A receptor antagonist (MDL-100907) microinjected into the hypoglossal nucleus. The expression of 5-HT and TASK-1 in the hypoglossal nucleus were detected by immunohistochemistry and reverse transcription quantitative polymerase chain reaction on the 1st, 3rd, 7th, 14th and 21st day of CIH exposure. The mean optical density (MOD) of 5-HT in the XII nucleus was significantly increased in the CIH and CIH + MDL group than the NO group on the 7th and 21st day ( p < 0.05). Compared with the NO group, the MOD and gene expression of TASK-1 in the CIH group was significantly increased on the 7th and 14th day ( p < 0.05), then normalized on the 21st day. The TASK-1 expression in the CIH + MDL group was significantly lower than the CIH + PBS and CIH group on the 7th and 14th day ( p < 0.05). The CIH-induced transiently upregulation of the TASK-1 expression in the hypoglossal nucleus could be reversed by 5-HT 2A receptor antagonist, indicating that the modulation of the TASK-1 expression in response to CIH involves 5-HT and 5-HT 2A receptors, and this CIH effect might be 5-HT 2A receptor-dependent.
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Affiliation(s)
- Wen-Yang Li
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Aidi Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Hongyu Jin
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Ying Zou
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Zanfeng Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Wei Wang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
| | - Jian Kang
- Institute of Respiratory Disease, The First Hospital of China Medical University, Shenyang, Liaoning, China
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15
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Choi JH, Yarishkin O, Kim E, Bae Y, Kim A, Kim SC, Ryoo K, Cho CH, Hwang EM, Park JY. TWIK-1/TASK-3 heterodimeric channels contribute to the neurotensin-mediated excitation of hippocampal dentate gyrus granule cells. Exp Mol Med 2018; 50:1-13. [PMID: 30416196 PMCID: PMC6230555 DOI: 10.1038/s12276-018-0172-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 07/16/2018] [Accepted: 07/23/2018] [Indexed: 01/15/2023] Open
Abstract
Two-pore domain K+ (K2P) channels have been shown to modulate neuronal excitability. The physiological role of TWIK-1, the first identified K2P channel, in neuronal cells is largely unknown, and we reported previously that TWIK-1 contributes to the intrinsic excitability of dentate gyrus granule cells (DGGCs) in mice. In the present study, we investigated the coexpression of TWIK-1 and TASK-3, another K2P member, in DGGCs. Immunohistochemical staining data showed that TASK-3 proteins were highly localized in the proximal dendrites and soma of DGGCs, and this localization is similar to the expression pattern of TWIK-1. TWIK-1 was shown to associate with TASK-3 in DGGCs of mouse hippocampus and when both genes were overexpressed in COS-7 cells. shRNA-mediated gene silencing demonstrated that TWIK-1/TASK-3 heterodimeric channels displayed outwardly rectifying currents and contributed to the intrinsic excitability of DGGCs. Neurotensin-neurotensin receptor 1 (NT-NTSR1) signaling triggered the depolarization of DGGCs by inhibiting TWIK-1/TASK-3 heterodimeric channels, causing facilitated excitation of DGGCs. Taken together, our study clearly showed that TWIK-1/TASK-3 heterodimeric channels contribute to the intrinsic excitability of DGGCs and that their activities are regulated by NT-NTSR1 signaling.
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Affiliation(s)
- Jae Hyouk Choi
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea.,Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology, Seoul, 02792, Republic of Korea
| | - Oleg Yarishkin
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea
| | - Eunju Kim
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea.,School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea
| | - Yeonju Bae
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea
| | - Ajung Kim
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea.,KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, 02447, Republic of Korea
| | - Seung-Chan Kim
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea.,School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea
| | - Kanghyun Ryoo
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea
| | - Chang-Hoon Cho
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea
| | - Eun Mi Hwang
- Korea Institute of Science and Technology (KIST), Center for Functional Connectomics, Seoul, 02792, Republic of Korea. .,Division of Bio-Medical Science and Technology, KIST School, Korea University of Science and Technology, Seoul, 02792, Republic of Korea. .,KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul, 02447, Republic of Korea.
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul, 02841, Republic of Korea.
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16
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Fullana MN, Ferrés-Coy A, Ortega JE, Ruiz-Bronchal E, Paz V, Meana JJ, Artigas F, Bortolozzi A. Selective Knockdown of TASK3 Potassium Channel in Monoamine Neurons: a New Therapeutic Approach for Depression. Mol Neurobiol 2018; 56:3038-3052. [PMID: 30088175 DOI: 10.1007/s12035-018-1288-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/30/2018] [Indexed: 12/25/2022]
Abstract
Current pharmacological treatments for major depressive disorder (MDD) are severely compromised by both slow action and limited efficacy. RNAi strategies have been used to evoke antidepressant-like effects faster than classical drugs. Using small interfering RNA (siRNA), we herein show that TASK3 potassium channel knockdown in monoamine neurons induces antidepressant-like responses in mice. TASK3-siRNAs were conjugated to cell-specific ligands, sertraline (Ser) or reboxetine (Reb), to promote their selective accumulation in serotonin (5-HT) and norepinephrine (NE) neurons, respectively, after intranasal delivery. Following neuronal internalization of conjugated TASK3-siRNAs, reduced TASK3 mRNA and protein levels were found in the brainstem 5-HT and NE cell groups. Moreover, Ser-TASK3-siRNA induced robust antidepressant-like behaviors, enhanced the hippocampal plasticity, and potentiated the fluoxetine-induced increase on extracellular 5-HT. Similar responses, yet of lower magnitude, were detected for Reb-TASK3-siRNA. These findings provide substantial support for TASK3 as a potential target, and RNAi-based strategies as a novel therapeutic approach to treat MDD.
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Affiliation(s)
- M Neus Fullana
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - Albert Ferrés-Coy
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - Jorge E Ortega
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain.,Department of Pharmacology, University of Basque Country UPV/EHU and BioCruces Health Research Institute, Bizkaia, Spain
| | - Esther Ruiz-Bronchal
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - Verónica Paz
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - J Javier Meana
- Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain.,Department of Pharmacology, University of Basque Country UPV/EHU and BioCruces Health Research Institute, Bizkaia, Spain
| | - Francesc Artigas
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain.,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain.,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain
| | - Analia Bortolozzi
- Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona, Spain. .,Department of Neurochemistry and Neuropharmacology, IIBB-CSIC (Consejo Superior de Investigaciones Científicas), Barcelona, Spain. .,Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII, Madrid, Spain.
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17
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Sex-dependent differences in the in vivo respiratory phenotype of the TASK-1 potassium channel knockout mouse. Respir Physiol Neurobiol 2017; 245:13-28. [DOI: 10.1016/j.resp.2016.11.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Revised: 11/04/2016] [Accepted: 11/07/2016] [Indexed: 11/19/2022]
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18
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Ceder MM, Lekholm E, Hellsten SV, Perland E, Fredriksson R. The Neuronal and Peripheral Expressed Membrane-Bound UNC93A Respond to Nutrient Availability in Mice. Front Mol Neurosci 2017; 10:351. [PMID: 29163028 PMCID: PMC5671512 DOI: 10.3389/fnmol.2017.00351] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 10/13/2017] [Indexed: 12/31/2022] Open
Abstract
Many transporters such as the solute carriers belonging to the Major facilitator superfamily Pfam clan are orphans in that their tissue and cellular localization as well as substrate profile and function are still unknown. Here we have characterized the putative solute carrier UNC93A. We aimed to investigate the expression profile on both protein and mRNA level of UNC93A in mouse since it has not been clarified. UNC93A staining was found in cortex, hippocampus and cerebellum. It was found to be expressed in many neurons, but not all, with staining located in close proximity to the plasma membrane. Furthermore, we aimed to extend the starvation data available for Unc93a in hypothalamic cell cultures from mouse. We investigated the Unc93a alterations with focus on amino acid deprivation in embryonic cortex cells from mice as well as 24 h starvation in adult male mice and compared it to recently studied putative and known solute carriers. Unc93a expression was found both in the brain and peripheral organs, in low to moderate levels in the adult mice and was affected by amino acid deprivation in embryonic cortex cultures and starvation in in vivo samples. In conclusion, the membrane-bound UNC93A is expressed in both the brain and peripheral tissues and responds to nutrient availability in mice.
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Affiliation(s)
- Mikaela M Ceder
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Emilia Lekholm
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Sofie V Hellsten
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Emelie Perland
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
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19
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Buehler PK, Bleiler D, Tegtmeier I, Heitzmann D, Both C, Georgieff M, Lesage F, Warth R, Thomas J. Abnormal respiration under hyperoxia in TASK-1/3 potassium channel double knockout mice. Respir Physiol Neurobiol 2017; 244:17-25. [PMID: 28673876 DOI: 10.1016/j.resp.2017.06.009] [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: 03/08/2017] [Revised: 06/23/2017] [Accepted: 06/24/2017] [Indexed: 01/29/2023]
Abstract
Despite intensive research, the exact function of TASK potassium channels in central and peripheral chemoreception is still under debate. In this study, we investigated the respiration of unrestrained TASK-3 (TASK-3-/-) and TASK-1/TASK-3 double knockout (TASK-1/3-/-) adult male mice in vivo using a plethysmographic device. Ventilation parameters of TASK-3-/- mice were normal under control condition (21% O2) and upon hypoxia and hypercapnia they displayed the physiological increase of ventilation. TASK-1/3-/- mice showed increased ventilation under control conditions. This increase of ventilation was caused by increased tidal volumes (VT), a phenomenon similarly observed in TASK-1-/- mice. Under acute hypoxia, TASK-1/3-/- mice displayed the physiological increase of the minute volume. Interestingly, this increase was not related to an increase of the respiratory frequency (fR), as observed in wild-type mice, but was caused by a strong increase of VT. This particular respiratory phenotype is reminiscent of the respiratory phenotype of carotid body-denervated rodents in the compensated state. Acute hypercapnia (5% CO2) stimulated ventilation in TASK-1/3-/- and wild-type mice to a similar extent; however, at higher CO2 concentrations (>5% CO2) the stimulation of ventilation was more pronounced in TASK-1/3-/- mice. At hyperoxia (100% O2), TASK-1-/-, TASK-3-/- and wild-type mice showed the physiological small decrease of ventilation. In sharp contrast, TASK-1/3-/- mice exhibited an abnormal increase of ventilation under hyperoxia. In summary, these measurements showed a grossly normal respiration of TASK-3-/- mice and a respiratory phenotype of TASK-1/3-/- mice that was characterized by a markedly enhanced tidal volume, similar to the one observed in TASK-1-/- mice. The abnormal hyperoxia response, exclusively found in TASK-1/3-/- double mutant mice, indicates that both TASK-1 and TASK-3 are essential for the hyperoxia-induced hypoventilation. The peculiar respiratory phenotype of TASK-1/3 knockout mice is reminiscent of the respiration of animals with long-term carotid body dysfunction. Taken together, TASK-1 and TASK-3 appear to serve specific and distinct roles in the complex processes underlying chemoreception and respiratory control.
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Affiliation(s)
- Philipp K Buehler
- University Children's Hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland
| | - Doris Bleiler
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany; Department of Anaesthesia, University Hospital Regensburg, 93042 Regensburg, Germany
| | - Ines Tegtmeier
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany
| | - Dirk Heitzmann
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany; University Medical Centre Mannheim, V. Medical Clinic, Theodor-Kutzer-Ufer 1-3, 68167 Mannheim, Germany
| | - Christian Both
- University Children's Hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland
| | - Michael Georgieff
- Institute of Anesthesiology, University of Ulm, D-89081 Ulm, Germany
| | - Florian Lesage
- Université Côte d'Azur, Inserm, CNRS, Institut de Pharmacologie Moléculaire et Cellulaire, LabEx ICST, 660 Route des Lucioles, 06560, Valbonne, France
| | - Richard Warth
- Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany
| | - Jörg Thomas
- University Children's Hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland.
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20
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Nagata S, Nakamura S, Nakayama K, Mochizuki A, Yamamoto M, Inoue T. Postnatal changes in glutamatergic inputs of jaw-closing motoneuron dendrites. Brain Res Bull 2016; 127:47-55. [PMID: 27568204 DOI: 10.1016/j.brainresbull.2016.08.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 07/15/2016] [Accepted: 08/23/2016] [Indexed: 11/26/2022]
Abstract
Dendrites of masseter (jaw-closing) motoneurons (MMNs) are well developed and ramify extensively throughout the trigeminal motor nucleus and often extend into the adjacent reticular formation. It is possible that the dendrites have active properties, which are altered with the development of the orofacial musculoskeletal system. Thus, we examined the changes in somatic voltage responses evoked by photostimulation of the MMN dendrites by laser photolysis of caged glutamate from postnatal day (P) 2-5 and 9-12 rats. We photostimulated 39 spots that were arranged around each recorded neuron in a concave shape and found that the dendritic stimulation induced somatic depolarization in the presence of tetrodotoxin in all MMNs. With increasing photostimulation intensity, the responses grew in amplitude up to a certain threshold, where a step-like increase in amplitude occurred. In 75% of P2-5 MMNs, the step-like increase in amplitude, which was blocked by 20μM D(-)-2-amino-5-phosphonovaleric acid application, corresponded to the NMDA spikes/plateau potentials. In contrast, at P9-12 the responses became significantly smaller in amplitude and shorter in duration and only one neuron out of 12 MMNs showed NMDA spikes/plateau potentials. These results suggest that the glutamatergic responses evoked by photostimulation of the MMN dendrites change during the first two postnatal weeks, and these changes may be involved in the transition from suckling to chewing during postnatal development.
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Affiliation(s)
- Shoko Nagata
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan; Department of Periodontology, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta-ku, Tokyo, 145-8515, Japan
| | - Shiro Nakamura
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan.
| | - Kiyomi Nakayama
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Ayako Mochizuki
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
| | - Matsuo Yamamoto
- Department of Periodontology, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta-ku, Tokyo, 145-8515, Japan
| | - Tomio Inoue
- Department of Oral Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo, 142-8555, Japan
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21
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The Possible Role of TASK Channels in Rank-Ordered Recruitment of Motoneurons in the Dorsolateral Part of the Trigeminal Motor Nucleus. eNeuro 2016; 3:eN-NWR-0138-16. [PMID: 27482536 PMCID: PMC4951569 DOI: 10.1523/eneuro.0138-16.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 06/21/2016] [Indexed: 01/11/2023] Open
Abstract
Because a rank-ordered recruitment of motor units occurs during isometric contraction of jaw-closing muscles, jaw-closing motoneurons (MNs) may be recruited in a manner dependent on their soma sizes or input resistances (IRs). In the dorsolateral part of the trigeminal motor nucleus (dl-TMN) in rats, MNs abundantly express TWIK (two-pore domain weak inwardly rectifying K channel)-related acid-sensitive-K(+) channel (TASK)-1 and TASK3 channels, which determine the IR and resting membrane potential. Here we examined how TASK channels are involved in IR-dependent activation/recruitment of MNs in the rat dl-TMN by using multiple methods. The real-time PCR study revealed that single large MNs (>35 μm) expressed TASK1 and TASK3 mRNAs more abundantly compared with single small MNs (15-20 μm). The immunohistochemistry revealed that TASK1 and TASK3 channels were complementarily distributed in somata and dendrites of MNs, respectively. The density of TASK1 channels seemed to increase with a decrease in soma diameter while there were inverse relationships between the soma size of MNs and IR, resting membrane potential, or spike threshold. Dual whole-cell recordings obtained from smaller and larger MNs revealed that the recruitment of MNs depends on their IRs in response to repetitive stimulation of the presumed Ia afferents. 8-Bromoguanosine-cGMP decreased IRs in small MNs, while it hardly changed those in large MNs, and subsequently decreased the difference in spike-onset latency between the smaller and larger MNs, causing a synchronous activation of MNs. These results suggest that TASK channels play critical roles in rank-ordered recruitment of MNs in the dl-TMN.
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22
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Renigunta V, Schlichthörl G, Daut J. Much more than a leak: structure and function of K₂p-channels. Pflugers Arch 2015; 467:867-94. [PMID: 25791628 DOI: 10.1007/s00424-015-1703-7] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 11/27/2022]
Abstract
Over the last decade, we have seen an enormous increase in the number of experimental studies on two-pore-domain potassium channels (K2P-channels). The collection of reviews and original articles compiled for this special issue of Pflügers Archiv aims to give an up-to-date summary of what is known about the physiology and pathophysiology of K2P-channels. This introductory overview briefly describes the structure of K2P-channels and their function in different organs. Its main aim is to provide some background information for the 19 reviews and original articles of this special issue of Pflügers Archiv. It is not intended to be a comprehensive review; instead, this introductory overview focuses on some unresolved questions and controversial issues, such as: Do K2P-channels display voltage-dependent gating? Do K2P-channels contribute to the generation of action potentials? What is the functional role of alternative translation initiation? Do K2P-channels have one or two or more gates? We come to the conclusion that we are just beginning to understand the extremely complex regulation of these fascinating channels, which are often inadequately described as 'leak channels'.
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Affiliation(s)
- Vijay Renigunta
- Institute of Physiology and Pathophysiology, Marburg University, 35037, Marburg, Germany
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23
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The role of protein-protein interactions in the intracellular traffic of the potassium channels TASK-1 and TASK-3. Pflugers Arch 2015; 467:1105-20. [PMID: 25559843 DOI: 10.1007/s00424-014-1672-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
Abstract
The intracellular transport of membrane proteins is controlled by trafficking signals: Short peptide motifs that mediate the contact with COPI, COPII or various clathrin-associated coat proteins. In addition, many membrane proteins interact with accessory proteins that are involved in the sorting of these proteins to different intracellular compartments. In the K2P channels, TASK-1 and TASK-3, the influence of protein-protein interactions on sorting decisions has been studied in some detail. Both TASK paralogues interact with the adaptor protein 14-3-3; TASK-1 interacts, in addition, with the adaptor protein p11 (S100A10) and the endosomal SNARE protein syntaxin-8. The role of these interacting proteins in controlling the intracellular traffic of the channels and the underlying molecular mechanisms are summarised in this review. In the case of 14-3-3, the interacting protein masks a retention signal in the C-terminus of the channel; in the case of p11, the interacting protein carries a retention signal that localises the channel to the endoplasmic reticulum; and in the case of syntaxin-8, the interacting protein carries an endocytosis signal that complements an endocytosis signal of the channel. These examples illustrate some of the mechanisms by which interacting proteins may determine the itinerary of a membrane protein within a cell and suggest that the intracellular traffic of membrane proteins may be adapted to the specific functions of that protein by multiple protein-protein interactions.
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The role of acid-sensitive two-pore domain potassium channels in cardiac electrophysiology: focus on arrhythmias. Pflugers Arch 2014; 467:1055-67. [PMID: 25404566 DOI: 10.1007/s00424-014-1637-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/14/2014] [Accepted: 10/21/2014] [Indexed: 10/24/2022]
Abstract
The current kinetics of two-pore domain potassium (K2P) channels resemble those of the steady-state K(+) currents being active during the plateau phase of cardiac action potentials. Recent studies support that K2P channels contribute to these cardiac currents and thereby influence action potential duration in the heart. Ten of the 15 K2P channels present in the human genome are sensitive to variations of the extracellular and/or intracellular pH value. This review focuses on a set of K2P channels which are inhibited by extracellular protons, including the subgroup of tandem of P domains in a weak inward-rectifying K(+) (TWIK)-related acid-sensitive potassium (TASK) and TWIK-related alkaline-activated K(+) (TALK) channels. The role of TWIK-1 in the heart is also discussed since, after successful expression, an extracellular pH dependence, similar to that of TASK-1, was described as a hallmark of TWIK-1. The expression profile in cardiac tissue of different species and the functional data in the heart are summarized. The distinct role of the different acid-sensitive K2P channels in cardiac electrophysiology, inherited forms of arrhythmias and pharmacology, and their role as drug targets is currently emerging and is the subject of this review.
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25
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Bayliss DA, Barhanin J, Gestreau C, Guyenet PG. The role of pH-sensitive TASK channels in central respiratory chemoreception. Pflugers Arch 2014; 467:917-29. [PMID: 25346157 DOI: 10.1007/s00424-014-1633-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 10/08/2014] [Accepted: 10/12/2014] [Indexed: 01/16/2023]
Abstract
A number of the subunits within the family of K2P background K(+) channels are sensitive to changes in extracellular pH in the physiological range, making them likely candidates to mediate various pH-dependent processes. Based on expression patterns within several brainstem neuronal cell groups that are believed to function in CO2/H(+) regulation of breathing, three TASK subunits-TASK-1, TASK-2, and TASK-3-were specifically hypothesized to contribute to this central respiratory chemoreflex. For the acid-sensitive TASK-1 and TASK-3 channels, despite widespread expression at multiple levels within the brainstem respiratory control system (including presumptive chemoreceptor populations), experiments in knockout mice provided no evidence for their involvement in CO2 regulation of breathing. By contrast, the alkaline-activated TASK-2 channel has a more restricted brainstem distribution and was localized to the Phox2b-expressing chemoreceptor neurons of the retrotrapezoid nucleus (RTN). Remarkably, in a Phox2b(27Ala/+) mouse genetic model of congenital central hypoventilation syndrome (CCHS) that is characterized by reduced central respiratory chemosensitivity, selective ablation of Phox2b-expressing RTN neurons was accompanied by a corresponding loss of TASK-2 expression. Furthermore, genetic deletion of TASK-2 blunted RTN neuronal pH sensitivity in vitro, reduced alkaline-induced respiratory network inhibition in situ and diminished the ventilatory response to CO2/H(+) in vivo. Notably, a subpopulation of RTN neurons from TASK-2(-/-) mice retained their pH sensitivity, at least in part due to a residual pH-sensitive background K(+) current, suggesting that other mechanisms (and perhaps other K2P channels) for RTN neuronal pH sensitivity are yet to be identified.
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Affiliation(s)
- Douglas A Bayliss
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, 22908-0735, USA,
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26
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Silent but not dumb: how cellular trafficking and pore gating modulate expression of TWIK1 and THIK2. Pflugers Arch 2014; 467:1121-31. [PMID: 25339226 DOI: 10.1007/s00424-014-1631-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2014] [Revised: 10/09/2014] [Accepted: 10/12/2014] [Indexed: 12/25/2022]
Abstract
Among K2P channels, a few of them turned out to be difficult to express in heterologous systems and were coined "silent subunits". Recent studies have shed light on the mechanisms behind this apparent lack of channel activity at the plasma membrane. For TWIK1 and THIK2 channels, silence is related to a combination of intracellular retention and low intrinsic activity. TWIK1 is constitutively endocytosed from the plasma membrane before being transported to recycling endosomes, whereas THIK2 is restricted to endoplasmic reticulum. These intracellular localizations are related to trafficking signals located in the cytoplasmic parts of the channels. When these motifs are mutated or masked, channels are redistributed at the plasma membrane and produce measurable currents. However, these currents are of modest amplitude. This weak basal activity is due to a hydrophobic barrier in the deep pore that limits water and ions in the conduction pathway. Other silent channels KCNK7, TWIK2, and TASK5 are still under study. Expression and characterization of these K2P channels pave the way for a better understanding of the mechanisms controlling intracellular trafficking of membrane proteins, ion conduction, and channel gating.
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27
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Burgos P, Zúñiga R, Domínguez P, Delgado-López F, Plant LD, Zúñiga L. Differential expression of two-pore domain potassium channels in rat cerebellar granule neurons. Biochem Biophys Res Commun 2014; 453:754-60. [PMID: 25305496 DOI: 10.1016/j.bbrc.2014.10.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 10/03/2014] [Indexed: 11/26/2022]
Abstract
Two pore domain potassium (K2P) channels are mostly present in the central nervous system (CNS) where they play important roles in modulating neuronal excitability. K2P channels give rise to background K(+) currents (IKSO) a key component in setting and maintaining the resting membrane potential in excitable cells. Here, we studied the expression and relative abundances of K2P channels in cerebellar granule neurons (CGNs), combining molecular biology, electrophysiology and immunologic techniques. The CGN IKSO was very sensitive to external pH, as previously reported. Quantitative determination of mRNA expression level demonstrated the existence of an accumulation pattern of transcripts in CGN that encode K2P9>K2P1>K2P3>K2P18>K2P2=K2P10>K2P4>K2P5 subunits. The presence of the major K2P subunits expressed was then confirmed by Western blot and immunofluorescence analysis, demonstrating robust expression of K2P1 (TWIK-1), K2P3 (TASK-1), K2P9 (TASK-3) and K2P18 (TRESK) channel protein. Based, on these results, it is concluded that K2P1, -3, -9 and -18 subunits represent the majority component of IKSO current in CGN.
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Affiliation(s)
- Paulina Burgos
- Centro de Investigaciones Médicas CIM, Escuela de Medicina, Universidad de Talca, Talca, Chile
| | - Rafael Zúñiga
- Centro de Investigaciones Médicas CIM, Escuela de Medicina, Universidad de Talca, Talca, Chile
| | - Pedro Domínguez
- Centro de Investigaciones Médicas CIM, Escuela de Medicina, Universidad de Talca, Talca, Chile
| | | | - Leigh D Plant
- Department of Biochemistry, Brandeis University, Waltham, USA
| | - Leandro Zúñiga
- Centro de Investigaciones Médicas CIM, Escuela de Medicina, Universidad de Talca, Talca, Chile.
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Marinc C, Derst C, Prüss H, Veh RW. Immunocytochemical localization of TASK-3 protein (K2P9.1) in the rat brain. Cell Mol Neurobiol 2014; 34:61-70. [PMID: 24077856 DOI: 10.1007/s10571-013-9987-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Accepted: 09/13/2013] [Indexed: 01/06/2023]
Abstract
Among all K2P channels, TASK-3 shows the most widespread expression in rat brain, regulating neuronal excitability and transmitter release. Using a recently purified and characterized polyclonal monospecific antibody against TASK-3, the entire rat brain was immunocytochemically analyzed for expression of TASK-3 protein. Besides its well-known strong expression in motoneurons and monoaminergic and cholinergic neurons, TASK-3 expression was found in most neurons throughout the brain. However, it was not detected in certain neuronal populations, and neuropil staining was restricted to few areas. Also, it was absent in adult glial cells. In hypothalamic areas, TASK-3 was particularly strongly expressed in the supraoptic and suprachiasmatic nuclei, whereas other hypothalamic nuclei showed lower protein levels. Immunostaining of hippocampal CA1 and CA3 pyramidal neurons showed strongest expression, together with clear staining of CA3 mossy fibers and marked staining also in the dentate gyrus granule cells. In neocortical areas, most neurons expressed TASK-3 with a somatodendritic localization, most obvious in layer V pyramidal neurons. In the cerebellum, TASK-3 protein was found mainly in neurons and neuropil of the granular cell layer, whereas Purkinje cells were only faintly positive. Particularly weak expression was demonstrated in the forebrain. This report provides a comprehensive overview of TASK-3 protein expression in the rat brain.
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29
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Rukova B, Staneva R, Hadjidekova S, Stamenov G, Milanova V, Toncheva D. Whole genome methylation analyses of schizophrenia patients before and after treatment. BIOTECHNOL BIOTEC EQ 2014; 28:518-524. [PMID: 26019538 PMCID: PMC4434134 DOI: 10.1080/13102818.2014.933501] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 05/05/2014] [Indexed: 12/12/2022] Open
Abstract
The aetiology of schizophrenia is still unknown but it involves both heritable and non-heritable factors. DNA methylation is an inheritable epigenetic modification that stably alters gene expression. It takes part in the regulation of neurodevelopment and may be a contributing factor to the pathogenesis of brain diseases. It was found that many of the antipsychotic drugs may lead to epigenetic modifications. We have performed 42 high-resolution genome-wide methylation array analyses to determine the methylation status of 27,627 CpG islands. Differentially methylated regions were studied with samples from 20 Bulgarian individuals divided in four groups according to their gender (12 males/8 females) and their treatment response (6 in complete/14 in incomplete remission). They were compared to two age and sex matched control pools (110 females in female pool/110 males in male pool) before and after treatment. We found significant differences in the methylation profiles between male schizophrenia patients with complete remission and control male pool before treatment (C16orf70, CST3, DDRGK1, FA2H, FLJ30058, MFSD2B, RFX4, UBE2J1, ZNF311) and male schizophrenia patients with complete remission and control male pool after treatment (AP1S3, C16orf59, KCNK15, LOC146336, MGC16384, XRN2) that potentially could be used as target genes for new therapeutic strategies as well as markers for good treatment response. Our data revealed major differences in methylation profiles between male schizophrenia patients in complete remission before and after treatment and healthy controls which supports the hypothesis that antipsychotic drugs may play a role in epigenetic modifications.
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Affiliation(s)
- Blaga Rukova
- Department of Medical Genetics, Medical University of Sofia , Sofia , Bulgaria
| | - Rada Staneva
- Department of Medical Genetics, Medical University of Sofia , Sofia , Bulgaria
| | - Savina Hadjidekova
- Department of Medical Genetics, Medical University of Sofia , Sofia , Bulgaria
| | | | - Vihra Milanova
- Department of Psychiatry, Medical University of Sofia , Sofia , Bulgaria
| | - Draga Toncheva
- Department of Medical Genetics, Medical University of Sofia , Sofia , Bulgaria
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30
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Altered and dynamic ion selectivity of K+ channels in cell development and excitability. Trends Pharmacol Sci 2014; 35:461-9. [PMID: 25023607 DOI: 10.1016/j.tips.2014.06.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 06/11/2014] [Accepted: 06/12/2014] [Indexed: 12/21/2022]
Abstract
K(+) channels play a key role in regulating cellular excitability. It was thought that the strong K(+) selectivity of these channels was static, only altered by mutations in their selectivity filter, which can cause severe genetic disorders. Recent studies demonstrate that selectivity of K(+) channels can also exhibit dynamic changes. Under acidic conditions or in low extracellular K(+) concentrations, the two-pore domain K(+) channel (K2P) TWIK1 becomes permeable to Na(+), shifting from an inhibitory role to an excitatory role. This phenomenon is responsible for the paradoxical depolarization of human cardiomyocytes in pathological hypokalemia, and therefore may contribute to cardiac arrhythmias. In other cell types, TWIK1 produces depolarizing leak currents under physiological conditions. Dynamic ion selectivity also occurs in other K2P channels. Here we review evidence that dynamic selectivity of K2P channels constitutes a new regulatory mechanism of cellular excitability, whose significance is only now becoming appreciated.
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31
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Potent and selective inhibitors of the TASK-1 potassium channel through chemical optimization of a bis-amide scaffold. Bioorg Med Chem Lett 2014; 24:3968-73. [PMID: 25017033 DOI: 10.1016/j.bmcl.2014.06.032] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 06/09/2014] [Accepted: 06/11/2014] [Indexed: 01/10/2023]
Abstract
TASK-1 is a two-pore domain potassium channel that is important to modulating cell excitability, most notably in the context of neuronal pathways. In order to leverage TASK-1 for therapeutic benefit, its physiological role needs better characterization; however, designing selective inhibitors that avoid the closely related TASK-3 channel has been challenging. In this study, a series of bis-amide derived compounds were found to demonstrate improved TASK-1 selectivity over TASK-3 compared to reported inhibitors. Optimization of a marginally selective hit led to analog 35 which displays a TASK-1 IC50=16 nM with 62-fold selectivity over TASK-3 in an orthogonal electrophysiology assay.
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32
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Renigunta V, Zou X, Kling S, Schlichthörl G, Daut J. Breaking the silence: functional expression of the two-pore-domain potassium channel THIK-2. Pflugers Arch 2013; 466:1735-45. [DOI: 10.1007/s00424-013-1404-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 11/09/2013] [Indexed: 10/26/2022]
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33
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Ehmann H, Hartwich H, Salzig C, Hartmann N, Clément-Ziza M, Ushakov K, Avraham KB, Bininda-Emonds ORP, Hartmann AK, Lang P, Friauf E, Nothwang HG. Time-dependent gene expression analysis of the developing superior olivary complex. J Biol Chem 2013; 288:25865-25879. [PMID: 23893414 DOI: 10.1074/jbc.m113.490508] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The superior olivary complex (SOC) is an essential auditory brainstem relay involved in sound localization. To identify the genetic program underlying its maturation, we profiled the rat SOC transcriptome at postnatal days 0, 4, 16, and 25 (P0, P4, P16, and P25, respectively), using genome-wide microarrays (41,012 oligonucleotides (oligos)). Differences in gene expression between two consecutive stages were highest between P4 and P16 (3.6%) and dropped to 0.06% between P16 and P25. To identify SOC-related genetic programs, we also profiled the entire brain at P4 and P25. The number of differentially expressed oligonucleotides between SOC and brain almost doubled from P4 to P25 (4.4% versus 7.6%). These data demonstrate considerable molecular specification around hearing onset, which is rapidly finalized. Prior to hearing onset, several transcription factors associated with the peripheral auditory system were up-regulated, probably coordinating the development of the auditory system. Additionally, crystallin-γ subunits and serotonin-related genes were highly expressed. The molecular repertoire of mature neurons was sculpted by SOC-related up- and down-regulation of voltage-gated channels and G-proteins. Comparison with the brain revealed a significant enrichment of hearing impairment-related oligos in the SOC (26 in the SOC, only 11 in the brain). Furthermore, 29 of 453 SOC-related oligos mapped within 19 genetic intervals associated with hearing impairment. Together, we identified sequential genetic programs in the SOC, thereby pinpointing candidates that may guide its development and ensure proper function. The enrichment of hearing impairment-related genes in the SOC may have implications for restoring hearing because central auditory structures might be more severely affected than previously appreciated.
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Affiliation(s)
- Heike Ehmann
- From the Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany
| | - Heiner Hartwich
- the Neurogenetics Group, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany
| | - Christian Salzig
- the Department of System Analysis, Prognosis, and Control, Fraunhofer Institute for Industrial Mathematics (ITWM), D-67663 Kaiserslautern, Germany
| | - Nadja Hartmann
- From the Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany
| | | | - Kathy Ushakov
- the Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | - Karen B Avraham
- the Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv 69978, Israel
| | | | - Alexander K Hartmann
- the Computational Theoretical Physics Group, University of Oldenburg, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany, and
| | - Patrick Lang
- the Department of System Analysis, Prognosis, and Control, Fraunhofer Institute for Industrial Mathematics (ITWM), D-67663 Kaiserslautern, Germany
| | - Eckhard Friauf
- From the Animal Physiology Group, Department of Biology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany
| | - Hans Gerd Nothwang
- the Neurogenetics Group, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany,; the Center for Neuroscience, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, Germany,; the Center of Excellence Hearing4all, 26111 Oldenburg, Germany.
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34
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Kim S, Lee Y, Tak HM, Park HJ, Sohn YS, Hwang S, Han J, Kang D, Lee KW. Identification of blocker binding site in mouse TRESK by molecular modeling and mutational studies. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012. [PMID: 23200789 DOI: 10.1016/j.bbamem.2012.11.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
TWIK (tandem-pore domain weak inward rectifying K(+))-related spinal cord K(+) channel, TRESK, a member of the tandem-pore domain K(+) channel family, is the most recently cloned K(2P) channel. TRESK is highly expressed in dorsal root ganglion neuron, a pain sensing neuron, which is a target for analgesics. In this study, a reliable 3D structure for transmembrane (TM) region of mouse TRESK (mTRESK) was constructed, and then the reasonable blocker binding mode of the protein was investigated. The 3D structure of the mTRESK built by homology modeling method was validated with recommend value of stereochemical quality. Based on the validated structure, K(+) channel blocker-bound conformation was obtained by molecular docking and 5ns MD simulation with DPPC lipid bilayer. Our docking study provides the plausible binding mode of known blockers with key interacting residues, especially, F156 and F364. Finally, these modeling results were verified by experimental study with mutation from phenylalanine to alanine (F156A, F364A and F156A/F364A) at the TM2 and TM4. This is the first modeling study for TRESK that can provide structural information of the protein including ligand binding information. These results can be useful in structure based drug design for finding new blockers of the TRESK as potential therapeutic target of pain treatment.
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Affiliation(s)
- Songmi Kim
- Gyeongsang National University, Gazha-dong, Jinju, Republic of Korea
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35
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Kim JH, von Gersdorff H. Suppression of spikes during posttetanic hyperpolarization in auditory neurons: the role of temperature, I(h) currents, and the Na(+)-K(+)-ATPase pump. J Neurophysiol 2012; 108:1924-32. [PMID: 22786951 DOI: 10.1152/jn.00103.2012] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In vivo recordings from postsynaptic neurons in the medial nucleus of the trapezoid body (MNTB), an auditory brain stem nucleus, show that acoustic stimulation produces a burst of spikes followed by a period of hyperpolarization and suppressed spiking activity. The underlying mechanism for this hyperpolarization and reduced spiking is unknown. Furthermore, the mechanisms that control excitability and resting membrane potential are not fully determined for these MNTB neurons. In this study we investigated the excitability of principal neurons from the MNTB after high-frequency afferent fiber stimulation, using whole cell recordings from postnatal day 15-17 rat brain stem slices. We found that Na(+)-K(+)-ATPase activity mediates a progressive hyperpolarization during a prolonged tetanic train and a posttetanic hyperpolarization (PTH) at the end of the train, when postsynaptic action potentials failed to fire. Raising the temperature to more physiological levels (from 22 to 35°C) depolarized the resting membrane potential of both presynaptic and postsynaptic cells and decreased the latency of action potential firing during PTH. Higher temperatures also reduced the presynaptic calyx action potential failure rates by 50% during presynaptic PTH, thus increasing the safety-factor for presynaptic spiking. The effect of temperature on hyperpolarization-activated cation current (I(h)) is reflected in the resting potential at both pre- and postsynaptic neurons. We thus propose that temperature-sensitive Na(+)-K(+)-ATPase activity and I(h) contribute to set the resting membrane potential and produce a brief period of suppressed spiking (or action potential failures) after a prolonged high-frequency afferent tetanus.
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Affiliation(s)
- Jun Hee Kim
- Vollum Institute, Oregon Health & Science University, Portland, Oregon, USA.
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36
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Cadaveira-Mosquera A, Pérez M, Reboreda A, Rivas-Ramírez P, Fernández-Fernández D, Lamas JA. Expression of K2P channels in sensory and motor neurons of the autonomic nervous system. J Mol Neurosci 2012; 48:86-96. [PMID: 22544515 DOI: 10.1007/s12031-012-9780-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 04/11/2012] [Indexed: 02/20/2023]
Abstract
Several types of neurons within the central and peripheral somatic nervous system express two-pore-domain potassium (K2P) channels, providing them with resting potassium conductances. We demonstrate that these channels are also expressed in the autonomic nervous system where they might be important modulators of neuronal excitability. We observed strong mRNA expression of members of the TRESK and TREK subfamilies in both the mouse superior cervical ganglion (mSCG) and the mouse nodose ganglion (mNG). Motor mSCG neurons strongly expressed mRNA transcripts for TRESK and TREK-2 subunits, whereas TASK-1 and TASK-2 subunits were only moderately expressed, with only few or very few transcripts for TREK-1 and TRAAK (TRESK ≈ TREK-2 > TASK-2 ≈ TASK-1 > TREK-1 > TRAAK). Similarly, the TRESK and TREK-1 subunits were the most strongly expressed in sensorial mNG neurons, while TASK-1 and TASK-2 mRNAs were moderately expressed, and fewer TREK-2 and TRAAK transcripts were detected (TRESK ≈ TREK-1 > TASK-1 ≈ TASK-2 > TREK-2 > TRAAK). Moreover, cell-attached single-channel recordings showed a major contribution of TRESK and TREK-1 channels in mNG. As the level of TRESK mRNA expression was not statistically different between the ganglia analysed, the distinct expression of TREK-1 and TREK-2 subunits was the main difference observed between these structures. Our results strongly suggest that TRESK and TREK channels are important modulators of the sensorial and motor information flowing through the autonomic nervous system, probably exerting a strong influence on vagal reflexes.
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Affiliation(s)
- Alba Cadaveira-Mosquera
- Department of Functional Biology, Faculty of Biology, University of Vigo, Campus Lagoas-Marcosende, 36310, Vigo, Spain
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Lesage F, Barhanin J. Molecular physiology of pH-sensitive background K(2P) channels. Physiology (Bethesda) 2012; 26:424-37. [PMID: 22170960 DOI: 10.1152/physiol.00029.2011] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Background K(2P) channels are tightly regulated by different stimuli including variations of external and internal pH. pH sensitivity relies on proton-sensing residues that influence channel gating and activity. Gene inactivation in the mouse is a revealing implication of K(2P) channels in many physiological functions ranging from hormone secretion to central respiratory adaptation. Surprisingly, only a few phenotypic traits of these mice have yet been directly related to the pH sensitivity of K(2P) channels.
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Affiliation(s)
- Florian Lesage
- Institut de Pharmacologie Moléculaire et Cellulaire, Unité Mixte de Recherche 6097 Centre National de la Recherche Scientifique, Valbonne, France.
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Seja P, Schonewille M, Spitzmaul G, Badura A, Klein I, Rudhard Y, Wisden W, Hübner CA, De Zeeuw CI, Jentsch TJ. Raising cytosolic Cl- in cerebellar granule cells affects their excitability and vestibulo-ocular learning. EMBO J 2012; 31:1217-30. [PMID: 22252133 PMCID: PMC3297995 DOI: 10.1038/emboj.2011.488] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 12/06/2011] [Indexed: 11/09/2022] Open
Abstract
Cerebellar cortical throughput involved in motor control comprises granule cells (GCs) and Purkinje cells (PCs), both of which receive inhibitory GABAergic input from interneurons. The GABAergic input to PCs is essential for learning and consolidation of the vestibulo-ocular reflex, but the role of GC excitability remains unclear. We now disrupted the Kcc2 K-Cl cotransporter specifically in either cell type to manipulate their excitability and inhibition by GABA(A)-receptor Cl(-) channels. Although Kcc2 may have a morphogenic role in synapse development, Kcc2 disruption neither changed synapse density nor spine morphology. In both GCs and PCs, disruption of Kcc2, but not Kcc3, increased [Cl(-)](i) roughly two-fold. The reduced Cl(-) gradient nearly abolished GABA-induced hyperpolarization in PCs, but in GCs it merely affected excitability by membrane depolarization. Ablation of Kcc2 from GCs impaired consolidation of long-term phase learning of the vestibulo-ocular reflex, whereas baseline performance, short-term gain-decrease learning and gain consolidation remained intact. These functions, however, were affected by disruption of Kcc2 in PCs. GC excitability plays a previously unknown, but specific role in consolidation of phase learning.
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Affiliation(s)
- Patricia Seja
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | | | - Guillermo Spitzmaul
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
| | | | - Ilse Klein
- Zentrum für Molekulare Neurobiologie (ZMNH), Universität Hamburg, Hamburg, Germany
| | - York Rudhard
- Zentrum für Molekulare Neurobiologie (ZMNH), Universität Hamburg, Hamburg, Germany
| | | | - Christian A Hübner
- Zentrum für Molekulare Neurobiologie (ZMNH), Universität Hamburg, Hamburg, Germany
- Institut für Humangenetik, Universitätsklinikum Jena, Friedrich-Schiller-Universität Jena, Jena, Germany
| | - Chris I De Zeeuw
- Department of Neuroscience, Erasmus MC, Rotterdam, The Netherlands
- Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Thomas J Jentsch
- Leibniz-Institut für Molekulare Pharmakologie (FMP) and Max-Delbrück-Centrum für Molekulare Medizin (MDC), Berlin, Germany
- Zentrum für Molekulare Neurobiologie (ZMNH), Universität Hamburg, Hamburg, Germany
- Cluster of Excellence NeuroCure, Charité-Universitätsmedizin Berlin, Berlin, Germany
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Abstract
BACKGROUND Local anesthetics (LAs) are typically used for regional anesthesia but can be given systemically to mitigate postoperative pain, supplement general anesthesia, or prevent cardiac arrhythmias. However, systemic application or inadvertent intravenous injection can be associated with substantial toxicity, including seizure induction. The molecular basis for this toxic action remains unclear. METHODS We characterized inhibition by different LAs of homomeric and heteromeric K channels containing TASK-1 (K2P3.1, KCNK3) and TASK-3 (K2P9.1, KCNK9) subunits in a mammalian expression system. In addition, we used TASK-1/TASK-3 knockout mice to test the possibility that TASK channels contribute to LA-evoked seizures. RESULTS LAs inhibited homomeric and heteromeric TASK channels in a range relevant for seizure induction; channels containing TASK-1 subunits were most sensitive and IC₅₀ values indicated a rank order potency of bupivacaine > ropivacaine >> lidocaine. LAs induced tonic-clonic seizures in mice with the same rank order potency, but higher LA doses were required to evoke seizures in TASK knockout mice. For bupivacaine, which produced the longest seizure times, seizure duration was significantly shorter in TASK knockout mice; bupivacaine-induced seizures were associated with an increase in electroencephalogram power at frequencies less than 5 Hz in both wild-type and TASK knockout mice. CONCLUSIONS These data suggest that increased neuronal excitability associated with TASK channel inhibition by LAs contributes to seizure induction. Because all LAs were capable of evoking seizures in TASK channel deleted mice, albeit at higher doses, the results imply that other molecular targets must also be involved in this toxic action.
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Klueva J, Lima ADD, Meis S, Voigt T, Munsch T. Hyperpolarization-activated cation current contributes to spontaneous network activity in developing neocortical cultures. Neurosignals 2011; 20:35-47. [PMID: 22094222 DOI: 10.1159/000330813] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 07/15/2011] [Indexed: 11/19/2022] Open
Abstract
The mechanisms underlying spontaneous burst activity (SBA), appearing in networks of embryonic cortical neurons at the end of the first week in vitro, remain elusive. Here we investigated the contribution of the hyperpolarization-activated cation current (I(h)) to SBA in cortical cultures of GAD67-GFP mice. I(h) current could be detected in GFP-positive large GABAergic interneurons (L-INs) and glutamatergic principal neurons (PNs) as early as DIV 5. Under current-clamp conditions, blockers of I(h) current, ZD7288 and Cs⁺, abolished the voltage sag and rebound depolarization. ZD7288 induced a hyperpolarization concomitant with an increase in the membrane input resistance in L-INs and PNs. Voltage-clamp recordings revealed I(h) as slowly activating inward current with a reversal potential close to -50 mV and a mid-activation point around -90 mV. Both, ZD7288 (1-10 μM) and Cs⁺ (1-2 mM) reduced SBA, spontaneous activity-driven Ca²⁺ transients, and frequency as well as amplitude of miniature GABAergic postsynaptic currents. Immunocytochemistry and Western blot demonstrated that HCN1 and HCN2 were the prevalent isoforms of HCN channels expressed in L-INs and PNs. These results suggest an important contribution of HCN channels to the maintenance of SBA in embryonic cortical cultures.
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Affiliation(s)
- Julia Klueva
- Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke-Universität, Magdeburg, Germany
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Immunocytochemical localization of TASK-3 channels in rat motor neurons. Cell Mol Neurobiol 2011; 32:309-18. [PMID: 22011781 DOI: 10.1007/s10571-011-9762-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 10/03/2011] [Indexed: 12/12/2022]
Abstract
Motor neurons are large cholinergic neurons located in the brain stem and spinal cord. In recent years, a functional role for TASK channels in cellular excitability and vulnerability to anesthetics of motor neurons has been described. Using a polyclonal monospecific antibody against the tandem pore domain K(+) channel (K2P channel) TWIK-related acid-sensitive K(+) channel (TASK-3), we analyzed the expression of the TASK-3 protein in motor systems of the rat CNS. Immunocytochemical staining showed strong TASK-3 expression in motor neurons of the facial, trigeminal, ambiguus, and hypoglossal nuclei. Oculomotor nuclei (including trochlear and abducens nucleus) were also strongly positive for TASK-3. The parasympathetic Edinger-Westphal nucleus and dorsal vagal nucleus showed significant, but weaker expression compared with somato- and branchiomotoric neurons. In addition, motor neurons in the anterior horn of the spinal cord were also strongly labeled for TASK-3 immunoreactivity. Based on morphological criteria, TASK-3 was found in the somatodendritic compartment of motor neurons. Cellular staining using methyl green and immunofluorescence double-labeling with anti-vesicular acetylcholine transporter (anti-vAChT) indicated ubiquitous TASK-3 expression in motor neurons, whereas in other brain regions TASK-3 showed a widespread but not ubiquitous expression. In situ hybridization using a TASK-3 specific riboprobe verified the expression of TASK-3 in motor neurons at the mRNA level.
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Immunocytochemical localization of TASK-3 (K(2P)9.1) channels in monoaminergic and cholinergic neurons. Cell Mol Neurobiol 2010; 31:323-35. [PMID: 21082237 DOI: 10.1007/s10571-010-9625-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 10/20/2010] [Indexed: 10/18/2022]
Abstract
Monoaminergic and cholinergic systems are important regulators of cortical and subcortical systems, and a variety of vegetative functions are controlled by the respective neurotransmitters. Neuronal excitability and transmitter release of these neurons are strongly regulated by their potassium conductances carried by Kir and K(2P) channels. Here we describe the generation and characterization of a polyclonal monospecific antibody against rat TASK-3, a major brain K(2P) channel. After removal of cross-reactivities and affinity purification the antibody was characterized by ELISA, immunocytochemistry of TASK-3 transfected cells, and Western blots indicating that the antibody only detects TASK-3 protein, but not its paralogs TASK-1 and TASK-5. Western blot analysis of brain membrane fractions showed a single band around 45 kD, close to the predicted molecular weight of the TASK-3 protein. In addition, specific immunolabeling using the anti-TASK-3 antibody in Western blot analysis and immunocytochemistry was blocked in a concentration dependent manner by its cognate antigen only. Immunocytochemical analysis of rat brain revealed strong expression of TASK-3 channels in serotoninergic neurons of the dorsal and median raphe, noradrenergic neurons of the locus coeruleus, histaminergic neurons of the tuberomammillary nucleus and in the cholinergic neurons of the basal nucleus of Meynert. Immunofluorescence double-labeling experiments with appropriate marker enzymes confirmed the expression of TASK-3 in cholinergic, serotoninergic, and noradrenergic neurons. In the dopaminergic system strong TASK-3 expression was found in the ventral tegmental area, whereas TASK-3 immunoreactivity in the substantia nigra compacta was only weak. All immunocytochemical results were supported by in situ hybridization using TASK-3 specific riboprobes.
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Veale EL, Rees KA, Mathie A, Trapp S. Dominant negative effects of a non-conducting TREK1 splice variant expressed in brain. J Biol Chem 2010; 285:29295-304. [PMID: 20605797 DOI: 10.1074/jbc.m110.108423] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Two-pore domain potassium (K(2P)) channels modulate neuronal excitability throughout the entire CNS. The stretch-activated channel TREK1 (K(2P)2.1) is expressed widely in brain and has been linked to depression, neuroprotection, pain perception, and epilepsy. Little, however, is known about the regulation of TREK1 expression on the transcriptional and translational level or about its trafficking to the plasma membrane. Here we have used PCR techniques to identify a splice variant of TREK1 expressed in the brain, which encodes a heavily truncated TREK1 protein retaining a single transmembrane domain. Functional expression of this splice variant TREK1ΔEx4 in tsA201 cells in the presence or absence of wild type TREK1 revealed that TREK1ΔEx4 has no channel activity itself but reduced TREK1 whole cell current amplitude. Confocal analysis of the expression of fluorescently tagged TREK1 variants revealed that TREK1ΔEx4 is translated, but it is retained in the intracellular compartment. Additionally, TREK1ΔEx4 reduced the level of TREK1 expression in the plasma membrane. Long and short forms of TREK1 derived from alternative translation initiation are differentially affected by TREK1ΔEx4, with the short form (lacking the first 41 amino acids at its N terminus) unaffected. This differential regulatory role of TREK1ΔEx4 will alter the functional profile of TREK1 current in neurons where they are expressed. These results indicate that the N-terminal domain and first transmembrane domain of TREK1 are likely to be important for channel dimerization and trafficking to the plasma membrane.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, The Universities of Kent and Greenwich at Medway, Chatham Maritime, Kent ME4 4TB, United Kingdom
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44
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Motoneuronal TASK channels contribute to immobilizing effects of inhalational general anesthetics. J Neurosci 2010; 30:7691-704. [PMID: 20519544 DOI: 10.1523/jneurosci.1655-10.2010] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
General anesthetics cause sedation, hypnosis, and immobilization via CNS mechanisms that remain incompletely understood; contributions of particular anesthetic targets in specific neural pathways remain largely unexplored. Among potential molecular targets for mediating anesthetic actions, members of the TASK subgroup [TASK-1 (K2P3.1) and TASK-3 (K2P9.1)] of background K(+) channels are appealing candidates since they are expressed in CNS sites relevant to anesthetic actions and activated by clinically relevant concentrations of inhaled anesthetics. Here, we used global and conditional TASK channel single and double subunit knock-out mice to demonstrate definitively that TASK channels account for motoneuronal, anesthetic-activated K(+) currents and to test their contributions to sedative, hypnotic, and immobilizing anesthetic actions. In motoneurons from all knock-out mice lines, TASK-like currents were reduced and cells were less sensitive to hyperpolarizing effects of halothane and isoflurane. In an immobilization assay, higher concentrations of both halothane and isoflurane were required to render TASK knock-out animals unresponsive to a tail pinch; in assays of sedation (loss of movement) and hypnosis (loss-of-righting reflex), TASK knock-out mice showed a modest decrease in sensitivity, and only for halothane. In conditional knock-out mice, with TASK channel deletion restricted to cholinergic neurons, immobilizing actions of the inhaled anesthetics and sedative effects of halothane were reduced to the same extent as in global knock-out lines. These data indicate that TASK channels in cholinergic neurons are molecular substrates for select actions of inhaled anesthetics; for immobilization, which is spinally mediated, these data implicate motoneurons as the likely neuronal substrates.
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Protein kinase G dynamically modulates TASK1-mediated leak K+ currents in cholinergic neurons of the basal forebrain. J Neurosci 2010; 30:5677-89. [PMID: 20410120 DOI: 10.1523/jneurosci.5407-09.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Leak K(+) conductance generated by TASK1/3 channels is crucial for neuronal excitability. However, endogenous modulators activating TASK channels in neurons remained unknown. We previously reported that in the presumed cholinergic neurons of the basal forebrain (BF), activation of NO-cGMP-PKG (protein kinase G) pathway enhanced the TASK1-like leak K(+) current (I-K(leak)). As 8-Br-cGMP enhanced the I-K(leak) mainly at pH 7.3 as if changing the I-K(leak) from TASK1-like to TASK3-like current, such an enhancement of the I-K(leak) would result either from an enhancement of hidden TASK3 component or from an acidic shift in the pH sensitivity profile of TASK1 component. In view of the report that protonation of TASK channel decreases its open probability, the present study was designed to examine whether the activation of PKG increases the conductance of TASK1 channels by reducing their binding affinity for H(+), i.e., by increasing K(d) for protonation, or not. We here demonstrate that PKG activation and inhibition respectively upregulate and downregulate TASK1 channels heterologously expressed in PKG-loaded HEK293 cells at physiological pH, by causing shifts in the K(d) in the acidic and basic directions, respectively. Such PKG modulations of TASK1 channels were largely abolished by mutating pH sensor H98. In the BF neurons that were identified to express ChAT and TASK1 channels, similar dynamic modulations of TASK1-like pH sensitivity of I-K(leak) were caused by PKG. It is strongly suggested that PKG activation and inhibition dynamically modulate TASK1 currents at physiological pH by bidirectionally changing K(d) values for protonation of the extracellular pH sensors of TASK1 channels in cholinergic BF neurons.
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Enyedi P, Czirják G. Molecular background of leak K+ currents: two-pore domain potassium channels. Physiol Rev 2010; 90:559-605. [PMID: 20393194 DOI: 10.1152/physrev.00029.2009] [Citation(s) in RCA: 620] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Two-pore domain K(+) (K(2P)) channels give rise to leak (also called background) K(+) currents. The well-known role of background K(+) currents is to stabilize the negative resting membrane potential and counterbalance depolarization. However, it has become apparent in the past decade (during the detailed examination of the cloned and corresponding native K(2P) channel types) that this primary hyperpolarizing action is not performed passively. The K(2P) channels are regulated by a wide variety of voltage-independent factors. Basic physicochemical parameters (e.g., pH, temperature, membrane stretch) and also several intracellular signaling pathways substantially and specifically modulate the different members of the six K(2P) channel subfamilies (TWIK, TREK, TASK, TALK, THIK, and TRESK). The deep implication in diverse physiological processes, the circumscribed expression pattern of the different channels, and the interesting pharmacological profile brought the K(2P) channel family into the spotlight. In this review, we focus on the physiological roles of K(2P) channels in the most extensively investigated cell types, with special emphasis on the molecular mechanisms of channel regulation.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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47
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Luján R. Organisation of potassium channels on the neuronal surface. J Chem Neuroanat 2010; 40:1-20. [PMID: 20338235 DOI: 10.1016/j.jchemneu.2010.03.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 03/10/2010] [Accepted: 03/11/2010] [Indexed: 11/30/2022]
Abstract
Potassium channels are a family of ion channels that govern the intrinsic electrical properties of neurons in the brain. Molecular cloning has revealed over 100 genes encoding the pore-forming alpha subunits of potassium channels in mammals, making them the most diverse subset of ion channels. Multiplicity in this ion channel family is further generated through alternative splicing. The precise location of potassium channels along the dendro-somato-axonic surface of the neurons is an important factor in determining its functional impact. Today, it is widely accepted that potassium channels can be located at any subcellular compartment on the neuronal surface, at synaptic and extrasynaptic sites, from somata to dendritic shafts, dendritic spines, axons or axon terminals. However, they are not evenly distributed on the neuronal surface and depending on the potassium channel subtype, are instead concentrated at different compartments. This selective localization of ion channels to specific neuronal compartments has many different functional implications. One factor necessary to understand the role of potassium channels in neuronal function is to unravel their specialized distribution and subcellular localization within a cell, and this can only be achieved by electron microscopy. In this review, I summarize anatomical findings, describing their distribution in the central nervous system. The distinct regional, cellular and subcellular distribution of potassium channels in the brain will be discussed in view of their possible functional implications.
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Affiliation(s)
- Rafael Luján
- Departamento de Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006 Albacete, Spain.
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48
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Yang JJ, Wang YT, Cheng PC, Kuo YJ, Huang RC. Cholinergic modulation of neuronal excitability in the rat suprachiasmatic nucleus. J Neurophysiol 2010; 103:1397-409. [PMID: 20071625 DOI: 10.1152/jn.00877.2009] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The central cholinergic system regulates both the circadian clock and sleep-wake cycle and may participate in the feedback control of vigilance states on neural excitability in the suprachiasmatic nucleus (SCN) that houses the circadian clock. Here we investigate the mechanisms for cholinergic modulation of SCN neuron excitability. Cell-attached recordings indicate that the nonspecific cholinergic agonist carbachol (CCh) inhibited 55% and excited 21% SCN neurons, leaving 24% nonresponsive. Similar response proportions were produced by two muscarinic receptor [muscarinic acetylcholine receptor (mAChR)] agonists, muscarine and McN-A-343 (M1/4 agonist), but not by two nicotinic receptor (nAChR) agonists, nicotine and choline (alpha7-nAChR agonist), which, however, produced similar response proportions. Whole cell and perforated-patch recordings indicate that CCh inhibition of firing was mediated by membrane hyperpolarization due to activation of background K(+) currents, which were sensitive to submillimolar concentrations of Ba(2+) and to millimolar concentrations of TEA. RT-PCR analysis demonstrated the presence of mRNA for M1 to M5 mAChRs in SCN. The CCh-induced hyperpolarization and activation of background K(+) currents were blocked by M4 antagonists and to a lesser degree by M1 antagonists but were insensitive to the antagonists for M2 or M3, suggesting the involvement of M4 and M1 mAChRs in mediating CCh inhibition of firing. CCh enhancement of firing was mediated by membrane depolarization, as a result of postsynaptic inhibition of background K(+) currents. The multiple actions of cholinergic modulation via multiple receptors and ion channels may allow acetylcholine to finely control SCN neuron excitability in different physiological settings.
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Affiliation(s)
- Jyh-Jeen Yang
- Dept. of Physiology and Pharmacology, Chang Gung University School of Medicine, Kwei-San, Tao-Yuan, Taiwan
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49
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Rank-ordered Recruitment of Masseter Motoneurons during Slow Closing Phase of Mastication Cycle Presumably by the Activity of Mesencephalic Trigeminal Neurons. J Oral Biosci 2010. [DOI: 10.1016/s1349-0079(10)80013-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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50
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Kang Y, Saito M, Toyoda H, Sato H. Recruitment of masseter motoneurons by the presumed spindle Ia inputs. PROGRESS IN BRAIN RESEARCH 2010; 187:163-71. [PMID: 21111207 DOI: 10.1016/b978-0-444-53613-6.00011-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The slow-closing phase of the mastication cycle plays a major role in the mastication of foods. However, the neuronal mechanism underlying the slow-closing phase remains unknown. The isometric contraction of jaw-closing muscles is developed through the recruitment of jaw-closing motoneurons during the slow-closing phase. It is well established that motor units are recruited depending on the order of sizes or input resistances (IRs) of motoneurons, which is known as the size principle. Two-pore-domain acid-sensitive K(+) (TASK1/3) channels are recently found to be the molecular correlates of the IR, and also found to be expressed in the masseter motoneurons. Here, we addressed the question whether spindle Ia inputs onto masseter motoneurons can induce the orderly recruitment of motoneurons in slice preparations of the rat brain using voltage-sensitive dye imaging and whole-cell patch-clamp methods. Voltage-sensitive dye imaging revealed the recruitment of many motoneurons in the whole nucleus of masseter in response to repetitive stimulation of the presumed spindle Ia inputs. Dual whole-cell recordings obtained from two adjacent motoneurons revealed the IR-ordered recruitment of motoneurons in response to repetitive stimulation of the presumed spindle Ia inputs. Thus, Ia inputs are likely to play a crucial role in the orderly recruitment of motoneurons of the trigeminal motor nucleus, which would be progressed during the slow-closing phase of the mastication cycle. Possible involvements of TASK channels in the orderly recruitment are discussed.
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Affiliation(s)
- Youngnam Kang
- Department of Neuroscience & Oral Physiology, Osaka University Graduate School of Dentistry,Yamadaoka, Suita, Osaka, Japan
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