1
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Debreczeni D, Baukál D, Pergel E, Veres I, Czirják G. Critical contribution of the intracellular C-terminal region to TRESK channel activity is revealed by the epithelial Na + current ratio (ENaR) method. J Biol Chem 2023; 299:104737. [PMID: 37084812 DOI: 10.1016/j.jbc.2023.104737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 04/15/2023] [Accepted: 04/17/2023] [Indexed: 04/23/2023] Open
Abstract
TRESK (K2P18.1) possesses unique structural proportions within the K2P background potassium channel family. The previously described TRESK regulatory mechanisms are based on the long intracellular loop between the second and third transmembrane segments (TMS). However, the functional significance of the exceptionally short intracellular C-terminal region (iCtr) following the fourth TMS has not yet been examined. In the present study, we investigated TRESK constructs modified at the iCtr by two-electrode voltage clamp and the newly developed epithelial sodium current ratio (ENaR) method in Xenopus oocytes. The ENaR method allowed the evaluation of channel activity by exclusively using electrophysiology, and provided data that are otherwise not readily available under whole-cell conditions. TRESK homodimer was connected with two ENaC (epithelial Na+ channel) heterotrimers and the Na+ current was measured as an internal reference, proportional to the number of channels in the plasma membrane. Modifications of TRESK iCtr resulted in diverse functional effects, indicating a complex contribution of this region to K+ channel activity. Mutations of positive residues in proximal iCtr locked TRESK in a low activity, calcineurin-insensitive state, although this phosphatase binds to distant motifs in the loop region. Accordingly, mutations in proximal iCtr may prevent the transmission of modulation to the gating machinery. Replacing distal iCtr with a sequence designed to interact with the inner surface of the plasma membrane increased the activity of the channel to unprecedented levels, as indicated by ENaR and single channel measurements. In conclusion, the distal iCtr is a major positive determinant of TRESK function.
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Affiliation(s)
| | - Dóra Baukál
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Enikő Pergel
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Irén Veres
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Gábor Czirják
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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2
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Zhao Y, Pasanen M, Rysä J. Placental ion channels: potential target of chemical exposure. Biol Reprod 2022; 108:41-51. [PMID: 36173899 PMCID: PMC9843680 DOI: 10.1093/biolre/ioac186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 09/23/2022] [Accepted: 09/29/2022] [Indexed: 01/21/2023] Open
Abstract
The placenta is an important organ for the exchange of substances between the fetus and the mother, hormone secretion, and fetoplacental immunological defense. Placenta has an organ-specific distribution of ion channels and trophoblasts, and placental vessels express a large number of ion channels. Several placental housekeeping activities and pregnancy complications are at least partly controlled by ion channels, which are playing an important role in regulating hormone secretion, trophoblastic homeostasis, ion transport, and vasomotor activity. The function of several placental ion channels (Na, Ca, and Cl ion channels, cation channel, nicotinic acetylcholine receptors, and aquaporin-1) is known to be influenced by chemical exposure, i.e., their responses to different chemicals have been tested and confirmed in experimental models. Here, we review the possibility that placental ion channels are targets of toxicological concern in terms of placental function, fetal growth, and development.
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Affiliation(s)
- Yi Zhao
- Department of Obstetrics, The First Affiliated Hospital of China Medical University, Shenyang, Liaoning, China
| | - Markku Pasanen
- School of Pharmacy, University of Eastern Finland, Kuopio, Finland
| | - Jaana Rysä
- Correspondence: School of Pharmacy, University of Eastern Finland, POB 1627, Kuopio 70211, Finland. Tel: +358403552412; E-mail:
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3
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K 2P18.1 translates T cell receptor signals into thymic regulatory T cell development. Cell Res 2022; 32:72-88. [PMID: 34702947 PMCID: PMC8547300 DOI: 10.1038/s41422-021-00580-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 08/25/2021] [Indexed: 02/07/2023] Open
Abstract
It remains largely unclear how thymocytes translate relative differences in T cell receptor (TCR) signal strength into distinct developmental programs that drive the cell fate decisions towards conventional (Tconv) or regulatory T cells (Treg). Following TCR activation, intracellular calcium (Ca2+) is the most important second messenger, for which the potassium channel K2P18.1 is a relevant regulator. Here, we identify K2P18.1 as a central translator of the TCR signal into the thymus-derived Treg (tTreg) selection process. TCR signal was coupled to NF-κB-mediated K2P18.1 upregulation in tTreg progenitors. K2P18.1 provided the driving force for sustained Ca2+ influx that facilitated NF-κB- and NFAT-dependent expression of FoxP3, the master transcription factor for Treg development and function. Loss of K2P18.1 ion-current function induced a mild lymphoproliferative phenotype in mice, with reduced Treg numbers that led to aggravated experimental autoimmune encephalomyelitis, while a gain-of-function mutation in K2P18.1 resulted in increased Treg numbers in mice. Our findings in human thymus, recent thymic emigrants and multiple sclerosis patients with a dominant-negative missense K2P18.1 variant that is associated with poor clinical outcomes indicate that K2P18.1 also plays a role in human Treg development. Pharmacological modulation of K2P18.1 specifically modulated Treg numbers in vitro and in vivo. Finally, we identified nitroxoline as a K2P18.1 activator that led to rapid and reversible Treg increase in patients with urinary tract infections. Conclusively, our findings reveal how K2P18.1 translates TCR signals into thymic T cell fate decisions and Treg development, and provide a basis for the therapeutic utilization of Treg in several human disorders.
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Mini-Review: Two Brothers in Crime - The Interplay of TRESK and TREK in Human Diseases. Neurosci Lett 2021; 769:136376. [PMID: 34852287 DOI: 10.1016/j.neulet.2021.136376] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/17/2021] [Accepted: 11/25/2021] [Indexed: 02/07/2023]
Abstract
TWIK-related spinal cord potassium (TRESK) and TWIK-related potassium (TREK) channels are both subfamilies of the two-pore domain potassium (K2P) channel group. Despite major structural, pharmacological, as well as biophysical differences, emerging data suggest that channels of these two subfamilies are functionally more closely related than previously assumed. Recent studies, for instance, indicate an assembling of TRESK and TREK subunits, leading to the formation of heterodimeric channels with different functional properties compared to homodimeric ones. Formation of tandems consisting of TRESK and TREK subunits might thus multiply the functional diversity of both TRESK and TREK activity. Based on the involvement of these channels in the pathophysiology of migraine, we here highlight the role as well as the impact of the interplay of TRESK and TREK subunits in the context of different disease settings. In this regard, we focus on their involvement in migraine and pain syndromes, as well as on their influence on (neuro-)inflammatory processes. Furthermore, we describe the potential implications for innovative therapeutic strategies that take advantage of TRESK and TREK modulation as well as obstacles encountered in the development of therapies related to the aforementioned diseases.
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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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Kim GT, Siregar AS, Kim EJ, Lee ES, Nyiramana MM, Woo MS, Hah YS, Han J, Kang D. Upregulation of TRESK Channels Contributes to Motor and Sensory Recovery after Spinal Cord Injury. Int J Mol Sci 2020; 21:ijms21238997. [PMID: 33256222 PMCID: PMC7731147 DOI: 10.3390/ijms21238997] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 11/22/2020] [Accepted: 11/24/2020] [Indexed: 12/27/2022] Open
Abstract
TWIK (tandem-pore domain weak inward rectifying K+)-related spinal cord K+ channel (TRESK), a member of the two-pore domain K+ channel family, is abundantly expressed in dorsal root ganglion (DRG) neurons. It is well documented that TRESK expression is changed in several models of peripheral nerve injury, resulting in a shift in sensory neuron excitability. However, the role of TRESK in the model of spinal cord injury (SCI) has not been fully understood. This study investigates the role of TRESK in a thoracic spinal cord contusion model, and in transgenic mice overexpressed with the TRESK gene (TGTRESK). Immunostaining analysis showed that TRESK was expressed in the dorsal and ventral neurons of the spinal cord. The TRESK expression was increased by SCI in both dorsal and ventral neurons. TRESK mRNA expression was upregulated in the spinal cord and DRG isolated from the ninth thoracic (T9) spinal cord contusion rats. The expression was significantly upregulated in the spinal cord below the injury site at acute time points (6, 24, and 48 h) after SCI (p < 0.05). In addition, TRESK expression was markedly increased in DRGs below and adjacent to the injury site. TRESK was expressed in inflammatory cells. In addition, the number and fluorescence intensity of TRESK-positive neurons increased in the dorsal and ventral horns of the spinal cord after SCI. TGTRESK SCI mice showed faster paralysis recovery and higher mechanical threshold compared to wild-type (WT)-SCI mice. TGTRESK mice showed lower TNF-α concentrations in the blood than WT mice. In addition, IL-1β concentration and apoptotic signals in the caudal spinal cord and DRG were significantly decreased in TGTRESK SCI mice compared to WT-SCI mice (p < 0.05). These results indicate that TRESK upregulated following SCI contributes to the recovery of paralysis and mechanical pain threshold by suppressing the excitability of motor and sensory neurons and inflammatory and apoptotic processes.
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Affiliation(s)
- Gyu-Tae Kim
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
| | - Adrian S. Siregar
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Eun-Jin Kim
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
| | - Eun-Shin Lee
- Department of Rehabilitation Medicine, College of Medicine, Gyeongsang National University, Jinju 52727, Korea;
| | - Marie Merci Nyiramana
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
| | - Min Seok Woo
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
| | - Young-Sool Hah
- Biomedical Research Institute, Gyeongsang National University Hospital, Jinju 52727, Korea;
| | - Jaehee Han
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
| | - Dawon Kang
- Department of Physiology and Institute of Health Sciences, College of Medicine, Gyeongsang National University, Jinju 52727, Korea; (G.-T.K.); (A.S.S.); (E.-J.K.); (M.M.N.); (M.S.W.); (J.H.)
- Department of Convergence Medical Science, Gyeongsang National University, Jinju 52727, Korea
- Correspondence: ; Tel.: +82-55-772-8044
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7
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The Background K + Channel TRESK in Sensory Physiology and Pain. Int J Mol Sci 2020; 21:ijms21155206. [PMID: 32717813 PMCID: PMC7432782 DOI: 10.3390/ijms21155206] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 12/18/2022] Open
Abstract
TRESK belongs to the K2P family of potassium channels, also known as background or leak potassium channels due to their biophysical properties and their role regulating membrane potential of cells. Several studies to date have highlighted the role of TRESK in regulating the excitability of specific subtypes of sensory neurons. These findings suggest TRESK could be involved in pain sensitivity. Here, we review the different evidence available that involves the channel in pain and sensory perception, from studies knocking out the channel or overexpressing it to identified mutations that link the channel to migraine pain. In addition, the therapeutic possibilities are discussed, as targeting the channel seems an interesting therapeutic approach to reduce nociceptor activation and to decrease pain.
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8
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Imbrici P, Nematian-Ardestani E, Hasan S, Pessia M, Tucker SJ, D'Adamo MC. Altered functional properties of a missense variant in the TRESK K + channel (KCNK18) associated with migraine and intellectual disability. Pflugers Arch 2020; 472:923-930. [PMID: 32394190 DOI: 10.1007/s00424-020-02382-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 04/16/2020] [Accepted: 04/22/2020] [Indexed: 12/16/2022]
Abstract
Mutations in the KCNK18 gene that encodes the TRESK K2P potassium channel have previously been linked with typical familial migraine with aura. Recently, an atypical clinical case has been reported in which a male individual carrying the p.Trp101Arg (W101R) missense mutation in the KCNK18 gene was diagnosed with intellectual disability and migraine with brainstem aura. Here we report the functional characterization of this new missense variant. This mutation is located in a highly conserved residue close to the selectivity filter, and our results show although these mutant channels retain their K+ selectivity and calcineurin-dependent regulation, the variant causes an overall dramatic loss of TRESK channel function as well as an initial dominant-negative effect when co-expressed with wild-type channels in Xenopus laevis oocytes. The dramatic functional consequences of this mutation thereby support a potentially pathogenic role for this variant and provide further insight into the relationship between the structure and function of this ion channel.
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Affiliation(s)
- Paola Imbrici
- Department of Pharmacy-Drug Sciences, University of Bari "Aldo Moro", Bari, Italy
| | - Ehsan Nematian-Ardestani
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta
| | - Sonia Hasan
- Department of Physiology, Faculty of Medicine, Kuwait University, Kuwait City, Kuwait
| | - Mauro Pessia
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.,Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, UK
| | - Maria Cristina D'Adamo
- Department of Physiology & Biochemistry, Faculty of Medicine and Surgery, University of Malta, MSD, Msida, 2080, Malta.
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TRESK K + Channel Activity Regulates Trigeminal Nociception and Headache. eNeuro 2019; 6:ENEURO.0236-19.2019. [PMID: 31308053 PMCID: PMC6664143 DOI: 10.1523/eneuro.0236-19.2019] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 06/23/2019] [Indexed: 02/07/2023] Open
Abstract
Although TWIK-related spinal cord K+ (TRESK) channel is expressed in all primary afferent neurons in trigeminal ganglia (TG) and dorsal root ganglia (DRG), whether TRESK activity regulates trigeminal pain processing is still not established. Dominant-negative TRESK mutations are associated with migraine but not with other types of pain in humans, suggesting that genetic TRESK dysfunction preferentially affects the generation of trigeminal pain, especially headache. Using TRESK global knock-out mice as a model system, we found that loss of TRESK in all TG neurons selectively increased the intrinsic excitability of small-diameter nociceptors, especially those that do not bind to isolectin B4 (IB4-). Similarly, loss of TRESK resulted in hyper-excitation of the small IB4- dural afferent neurons but not those that bind to IB4 (IB4+). Compared with wild-type littermates, both male and female TRESK knock-out mice exhibited more robust trigeminal nociceptive behaviors, including headache-related behaviors, whereas their body and visceral pain responses were normal. Interestingly, neither the total persistent outward current nor the intrinsic excitability was altered in adult TRESK knock-out DRG neurons, which may explain why genetic TRESK dysfunction is not associated with body and/or visceral pain in humans. We reveal for the first time that, among all primary afferent neurons, TG nociceptors are the most vulnerable to the genetic loss of TRESK. Our findings indicate that endogenous TRESK activity regulates trigeminal nociception, likely through controlling the intrinsic excitability of TG nociceptors. Importantly, we provide evidence that genetic loss of TRESK significantly increases the likelihood of developing headache.
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Verapamil Inhibits TRESK (K 2P18.1) Current in Trigeminal Ganglion Neurons Independently of the Blockade of Ca 2+ Influx. Int J Mol Sci 2018; 19:ijms19071961. [PMID: 29973548 PMCID: PMC6073232 DOI: 10.3390/ijms19071961] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 06/27/2018] [Accepted: 07/02/2018] [Indexed: 12/29/2022] Open
Abstract
Tandem pore domain weak inward rectifier potassium channel (TWIK)-related spinal cord K⁺ (TRESK; K2P18.1) channel is the only member of the two-pore domain K⁺ (K2P) channel family that is activated by an increase in intracellular Ca2+ concentration ([Ca2+]i) and linked to migraines. This study was performed to identify the effect of verapamil, which is an L-type Ca2+ channel blocker and a prophylaxis for migraines, on the TRESK channel in trigeminal ganglion (TG) neurons, as well as in a heterologous system. Single-channel and whole-cell currents were recorded in TG neurons and HEK-293 cells transfected with mTRESK using patch-clamping techniques. In TG neurons, changes in [Ca2+]i were measured using the fluo-3-AM Ca2+ indicator. Verapamil, nifedipine, and NiCl₂ inhibited the whole-cell currents in HEK-293 cells overexpressing mTRESK with IC50 values of 5.2, 54.3, and >100 μM, respectively. The inhibitory effect of verapamil on TRESK channel was also observed in excised patches. In TG neurons, verapamil (10 μM) inhibited TRESK channel activity by approximately 76%. The TRESK channel activity was not dependent on the presence of extracellular Ca2+. In addition, the inhibitory effect of verapamil on the TRESK channel remained despite the absence of extracellular Ca2+. These findings show that verapamil inhibits the TRESK current independently of the blockade of Ca2+ influx in TG neurons. Verapamil will be able to exert its pharmacological effects by modulating TRESK, as well as Ca2+ influx, in TG neurons in vitro. We suggest that verapamil could be used as an inhibitor for identifying TRESK channel in TG neurons.
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pH-sensitive K+ channel TREK-1 is a novel target in pancreatic cancer. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1994-2003. [DOI: 10.1016/j.bbadis.2016.07.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 06/16/2016] [Accepted: 07/15/2016] [Indexed: 12/17/2022]
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12
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Kyeong KS, Hong SH, Kim YC, Cho W, Myung SC, Lee MY, You RY, Kim CH, Kwon SY, Suzuki H, Park YJ, Jeong EH, Kim HS, Kim H, Lim SW, Xu WX, Lee SJ, Ji IW. Myometrial relaxation of mice via expression of two pore domain acid sensitive K(+) (TASK-2) channels. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:547-56. [PMID: 27610042 PMCID: PMC5015002 DOI: 10.4196/kjpp.2016.20.5.547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Revised: 08/01/2016] [Accepted: 08/08/2016] [Indexed: 11/17/2022]
Abstract
Myometrial relaxation of mouse via expression of two-pore domain acid sensitive (TASK) channels was studied. In our previous report, we suggested that two-pore domain acid-sensing K+ channels (TASK-2) might be one of the candidates for the regulation of uterine circular smooth muscles in mice. In this study, we tried to show the mechanisms of relaxation via TASK-2 channels in marine myometrium. Isometric contraction measurements and patch clamp technique were used to verify TASK conductance in murine myometrium. Western blot and immunehistochemical study under confocal microscopy were used to investigate molecular identity of TASK channel. In this study, we showed that TEA and 4-AP insensitive non-inactivating outward K+ current (NIOK) may be responsible for the quiescence of murine pregnant longitudinal myometrium. The characteristics of NIOK coincided with two-pore domain acid-sensing K+ channels (TASK-2). NIOK in the presence of K+ channel blockers was inhibited further by TASK inhibitors such as quinidine, bupivacaine, lidocaine, and extracellular acidosis. Furthermore, oxytocin and estrogen inhibited NIOK in pregnant myometrium. When compared to non-pregnant myometrium, pregnant myometrium showed stronger inhibition of NIOK by quinidine and increased immunohistochemical expression of TASK-2. Finally, TASK-2 inhibitors induced strong myometrial contraction even in the presence of L-methionine, a known inhibitor of stretch-activated channels in the longitudinal myometrium of mouse. Activation of TASK-2 channels seems to play an essential role for relaxing uterus during pregnancy and it might be one of the alternatives for preventing preterm delivery.
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Affiliation(s)
- Kyu-Sang Kyeong
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Seung Hwa Hong
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Young Chul Kim
- Department Physiology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Woong Cho
- Department of Pharmacology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Sun Chul Myung
- Department of Urology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Moo Yeol Lee
- Department of Physiology, College of Medicine, Chung-Ang University, Seoul 06974, Korea
| | - Ra Young You
- Department Physiology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Chan Hyung Kim
- Department of Pharmacology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | | | - Hikaru Suzuki
- Department of Physiology, Nagoya City University Medical School, Nagoya 467-8601, Japan
| | - Yeon Jin Park
- Department of Obstetrics and Gynecology, Cheongju St. Mary's Hospital, Cheongju 28323, Korea
| | - Eun-Hwan Jeong
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Hak Soon Kim
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Heon Kim
- Department of Preventive Medicine, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Seung Woon Lim
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Wen-Xie Xu
- Department of Physiology, Shanghai Jiaotong University, School of Medicine, Shanghai, 200240, P.R. China
| | - Sang Jin Lee
- Department of Medical Education, Chungbuk National University College of Medicine, Cheongju 28644, Korea
| | - Il Woon Ji
- Department of Obstetrics and Gynecology, Chungbuk National University College of Medicine, Cheongju 28644, Korea
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13
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Park H, Kim EJ, Han J, Han J, Kang D. Effects of analgesics and antidepressants on TREK-2 and TRESK currents. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2016; 20:379-85. [PMID: 27382354 PMCID: PMC4930906 DOI: 10.4196/kjpp.2016.20.4.379] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Revised: 05/04/2016] [Accepted: 05/09/2016] [Indexed: 01/18/2023]
Abstract
TWIK-related K+ channel-2 (TREK-2) and TWIK-related spinal cord K+ (TRESK) channel are members of two-pore domain K+ channel family. They are well expressed and help to set the resting membrane potential in sensory neurons. Modulation of TREK-2 and TRESK channels are involved in the pathogenesis of pain, and specifi c activators of TREK-2 and TRESK may be benefi cial for the treatment of pain symptoms. However, the effect of commonly used analgesics on TREK-2 and TRESK channels are not known. Here, we investigated the effect of analgesics on TREK-2 and TRESK channels. The effects of analgesics were examined in HEK cells transfected with TREK-2 or TRESK. Amitriptyline, citalopram, escitalopram, and fluoxetine significantly inhibited TREK-2 and TRESK currents in HEK cells (p<0.05, n=10). Acetaminophen, ibuprofen, nabumetone, and bupropion inhibited TRESK, but had no effect on TREK-2. These results show that all analgesics tested in this study inhibit TRESK activity. Further study is needed to identify the mechanisms by which the analgesics modulate TREK-2 and TRESK differently.
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Affiliation(s)
- Hyun Park
- Department of Neurosurgery, Gyeongsang National University Hospital, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 52727, Korea
| | - Eun-Jin Kim
- Department of Physiology, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 52727, Korea
| | - Jaehee Han
- Department of Physiology, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 52727, Korea
| | - Jongwoo Han
- Department of Neurosurgery, Gyeongsang National University Hospital, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 52727, Korea
| | - Dawon Kang
- Department of Physiology, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 52727, Korea
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14
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Ehling P, Meuth P, Eichinger P, Herrmann AM, Bittner S, Pawlowski M, Pankratz S, Herty M, Budde T, Meuth SG. Human T cells in silico: Modelling their electrophysiological behaviour in health and disease. J Theor Biol 2016; 404:236-250. [PMID: 27288542 DOI: 10.1016/j.jtbi.2016.06.001] [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: 03/03/2016] [Revised: 05/27/2016] [Accepted: 06/01/2016] [Indexed: 01/27/2023]
Abstract
Although various types of ion channels are known to have an impact on human T cell effector functions, their exact mechanisms of influence are still poorly understood. The patch clamp technique is a well-established method for the investigation of ion channels in neurons and T cells. However, small cell sizes and limited selectivity of pharmacological blockers restrict the value of this experimental approach. Building a realistic T cell computer model therefore can help to overcome these kinds of limitations as well as reduce the overall experimental effort. The computer model introduced here was fed off ion channel parameters from literature and new experimental data. It is capable of simulating the electrophysiological behaviour of resting and activated human CD4(+) T cells under basal conditions and during extracellular acidification. The latter allows for the very first time to assess the electrophysiological consequences of tissue acidosis accompanying most forms of inflammation.
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Affiliation(s)
- Petra Ehling
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany.
| | - Patrick Meuth
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany
| | - Paul Eichinger
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany; Department of Neuroradiology, Klinikum rechts der Isar, Technische Universität München TUM, Ismaninger Strasse 22, 81675 Munich, Germany
| | - Alexander M Herrmann
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany
| | - Stefan Bittner
- Department of Neurology, University Medical Center of the Johannes Gutenberg-University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany
| | - Matthias Pawlowski
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany; Wellcome Trust and MRC Cambridge Stem Cell Institute, and Anne McLaren Laboratory for Regenerative Medicine, University of Cambridge, West Forvie Building, Forvie Site, Robinson Way, Cambridge, UK
| | - Susann Pankratz
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany
| | - Michael Herty
- RWTH Aachen University, Mathematics (Continuous optimization), Templergraben 55, 52056 Aachen, Germany
| | - Thomas Budde
- Institute of Physiology I, Westfälische Wilhelms-Universität Münster, Robert-Koch-Str. 27a, 48149 Münster, Germany
| | - Sven G Meuth
- Department of Neurology, and Institute of Translational Neurology, Westfälische Wilhelms-Universität Münster, Albert-Schweitzer-Campus 1, Building A1, 48149 Münster, Germany
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15
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Veale EL, Mathie A. Aristolochic acid, a plant extract used in the treatment of pain and linked to Balkan endemic nephropathy, is a regulator of K2P channels. Br J Pharmacol 2016; 173:1639-52. [PMID: 26914156 PMCID: PMC4842925 DOI: 10.1111/bph.13465] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 02/08/2016] [Accepted: 02/15/2016] [Indexed: 01/08/2023] Open
Abstract
Background and Purpose Aristolochic acid (AristA) is found in plants used in traditional medicines to treat pain. We investigated the action of AristA on TREK and TRESK, potassium (K2P) channels, which are potential therapeutic targets in pain. Balkan endemic nephropathy (BEN) is a renal disease associated with AristA consumption. A mutation of TASK‐2 (K2P5.1) channels (T108P) is seen in some patients susceptible to BEN, so we investigated how both this mutation and AristA affected TASK‐2 channels. Experimental Approach Currents through wild‐type and mutated human K2P channels expressed in tsA201 cells were measured using whole‐cell patch‐clamp recordings in the presence and absence of AristA. Key Results TREK‐1‐ and TREK‐2‐mediated currents were enhanced by AristA (100 μM), whereas TRESK was inhibited. Inhibition of TRESK did not depend on the phosphorylation of key intracellular serines but was completely blocked by mutation of bulky residues in the inner pore (F145A_F352A). The TASK‐2_T108P mutation markedly reduced both current density and ion selectivity. A related mutation (T108C) had similar but less marked effects. External alkalization and application of flufenamic acid enhanced TASK‐2 and TASK‐2_T108C current but did not affect TASK‐2_T108P current. AristA (300 μM) produced a modest enhancement of TASK‐2 current. Conclusions and Implications Enhancement of TREK‐1 and TREK‐2 and inhibition of TRESK by AristA may contribute to therapeutically useful effects of this compound in pain. Whilst AristA is unlikely to interact directly with TASK‐2 channels in BEN, loss of functional TASK‐2 channels may indirectly increase susceptibility to AristA toxicity.
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Affiliation(s)
- Emma L Veale
- Medway School of Pharmacy, University of Kent, Kent, UK
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16
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Chen H, Zuo D, Zhang J, Zhou M, Ma L. Classification of 2-pore domain potassium channels based on rectification under quasi-physiological ionic conditions. Channels (Austin) 2015; 8:503-8. [PMID: 25616686 DOI: 10.4161/19336950.2014.973779] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
It is generally expected that 2-pore domain K(+) (K2P) channels are open or outward rectifiers in asymmetric physiological K(+) gradients, following the Goldman-Hodgkin-Katz (GHK) current equation. Although cloned K2P channels have been extensively studied, their current-voltage (I-V) relationships are not precisely characterized and previous definitions are contradictory. Here we study all the functional channels from 6 mammalian K2P subfamilies in transfected Chinese hamster ovary cells with patch-clamp technique, and examine whether their I-V relationships are described by the GHK current equation. K2P channels display 2 distinct types of I-V curves in asymmetric physiological K(+) gradients. Two K2P isoforms in the TWIK subfamily conduct large inward K(+) currents and have a nearly linear I-V curve. Ten isoforms from 5 other K2P subfamilies conduct small inward K(+) currents and exhibit open rectification, but fits with the GHK current equation cannot precisely reveal the differences in rectification among K2P channels. The Rectification Index, a ratio of limiting I-V slopes for outward and inward currents, is used to quantitatively describe open rectification of each K2P isoform, which is previously qualitatively defined as strong or weak open rectification. These results systematically and precisely classify K2P channels and suggest that TWIK K(+) channels have a unique feature in regulating cellular function.
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Affiliation(s)
- Haijun Chen
- a Department of Biological Sciences ; University at Albany; State University of New York ; Albany , NY USA
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17
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Zhang H, Cilz NI, Yang C, Hu B, Dong H, Lei S. Depression of neuronal excitability and epileptic activities by group II metabotropic glutamate receptors in the medial entorhinal cortex. Hippocampus 2015; 25:1299-313. [DOI: 10.1002/hipo.22437] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/24/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Haopeng Zhang
- Department of Basic Sciences; School of Medicine and Health Sciences, University of North Dakota; Grand Forks North Dakota
- Department of Anesthesiology; Xijing Hospital, Fourth Military Medical University; Xi'an Shaanxi Province China
| | - Nicholas I. Cilz
- Department of Basic Sciences; School of Medicine and Health Sciences, University of North Dakota; Grand Forks North Dakota
| | - Chuanxiu Yang
- Department of Basic Sciences; School of Medicine and Health Sciences, University of North Dakota; Grand Forks North Dakota
| | - Binqi Hu
- Department of Basic Sciences; School of Medicine and Health Sciences, University of North Dakota; Grand Forks North Dakota
| | - Hailong Dong
- Department of Anesthesiology; Xijing Hospital, Fourth Military Medical University; Xi'an Shaanxi Province China
| | - Saobo Lei
- Department of Basic Sciences; School of Medicine and Health Sciences, University of North Dakota; Grand Forks North Dakota
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18
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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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19
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Placing ion channels into a signaling network of T cells: from maturing thymocytes to healthy T lymphocytes or leukemic T lymphoblasts. BIOMED RESEARCH INTERNATIONAL 2015; 2015:750203. [PMID: 25866806 PMCID: PMC4383400 DOI: 10.1155/2015/750203] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 09/19/2014] [Indexed: 12/20/2022]
Abstract
T leukemogenesis is a multistep process, where the genetic errors during T cell maturation cause the healthy progenitor to convert into the leukemic precursor that lost its ability to differentiate but possesses high potential for proliferation, self-renewal, and migration. A new misdirecting "leukemogenic" signaling network appears, composed by three types of participants which are encoded by (1) genes implicated in determined stages of T cell development but deregulated by translocations or mutations, (2) genes which normally do not participate in T cell development but are upregulated, and (3) nondifferentially expressed genes which become highly interconnected with genes expressed differentially. It appears that each of three groups may contain genes coding ion channels. In T cells, ion channels are implicated in regulation of cell cycle progression, differentiation, activation, migration, and cell death. In the present review we are going to reveal a relationship between different genetic defects, which drive the T cell neoplasias, with calcium signaling and ion channels. We suggest that changes in regulation of various ion channels in different types of the T leukemias may provide the intracellular ion microenvironment favorable to maintain self-renewal capacity, arrest differentiation, induce proliferation, and enhance motility.
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20
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Enyedi P, Czirják G. Properties, regulation, pharmacology, and functions of the K₂p channel, TRESK. Pflugers Arch 2014; 467:945-58. [PMID: 25366493 DOI: 10.1007/s00424-014-1634-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 10/09/2014] [Accepted: 10/12/2014] [Indexed: 12/21/2022]
Abstract
TWIK-related spinal cord K(+) channel (TRESK) is the gene product of KCNK18, the last discovered leak potassium K2P channel gene. Under resting conditions, TRESK is constitutively phosphorylated at two regulatory regions. Protein kinase A (PKA) and microtubule affinity-regulating (MARK) kinases can be applied in experiments to phosphorylate these sites of TRESK expressed in Xenopus oocytes, respectively. Upon generation of a calcium signal, TRESK is dephosphorylated and thereby activated by calcineurin. In this process, the binding of calcineurin to the channel by non-catalytic interacting sites is essential. The phosphorylation/dephosphorylation regulatory process is modified by 14-3-3 proteins. Human, but not murine TRESK is also activated by protein kinase C. TRESK is expressed most abundantly in sensory neurons of the dorsal root ganglia (DRG) and trigeminal ganglia, and the channel modifies certain forms of nociceptive afferentation. In a large pedigree, a dominant negative mutant TRESK allele was found to co-segregate perfectly with migraine phenotype. While this genetic defect may be responsible only for a very small fraction of migraine cases, specific TRESK activation is expected to exert beneficial effect in common forms of the disease.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, P.O. Box 259, 1444, Budapest, Hungary,
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21
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Wareing M. Oxygen sensitivity, potassium channels, and regulation of placental vascular tone. Microcirculation 2014; 21:58-66. [PMID: 23710683 DOI: 10.1111/micc.12069] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 05/21/2013] [Indexed: 12/17/2022]
Abstract
The human fetoplacental vasculature is a low-resistance circulation with deoxygenated arterial relative to venous blood. The placenta lacks neuronal innervation suggesting that local physical (e.g., oxygenation; flow rate), paracrine (e.g., endothelial cell nitric oxide), and circulating (e.g., angiotensin II) factors will contribute to blood flow regulation in small fetoplacental vessels. Oxygenation (specifically hypoxia) has received particular attention. At the macro-level, hypoxic challenge increases vascular resistance, but the data's physiological relevance remains questionable. K(+) channels are a diverse family of proteins known to play important roles in the normal physiological functions of endothelial and smooth muscle cells of a variety of vascular beds. K(+) channels are categorized by their predicted transmembrane structure or gating properties. A small number of perfused placental cotyledon and isolated blood vessels studies have assessed K(+) channel activity. Specific activator/inhibitor application suggests functional voltage-gated channels, whereas toxin inhibitor studies have documented KCa channel activity. Pharmacological KATP channel activation significantly dilates preconstricted placental arteries and veins. There is a paucity of cell subtype-specific expression studies of placental K(+) channels. This review focuses on the roles of K(+) channels and oxygenation in controlling reactivity of small fetoplacental blood vessels.
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Affiliation(s)
- Mark Wareing
- Maternal and Fetal Health Research Centre, Institute of Human Development, University of Manchester, Manchester, UK; Maternal and Fetal Health Research Centre, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
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22
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Activation of neurotensin receptor 1 facilitates neuronal excitability and spatial learning and memory in the entorhinal cortex: beneficial actions in an Alzheimer's disease model. J Neurosci 2014; 34:7027-42. [PMID: 24828655 DOI: 10.1523/jneurosci.0408-14.2014] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurotensin (NT) is a tridecapeptide distributed in the CNS, including the entorhinal cortex (EC), a structure that is crucial for learning and memory and undergoes the earliest pathological alterations in Alzheimer's disease (AD). Whereas NT has been implicated in modulating cognition, the cellular and molecular mechanisms by which NT modifies cognitive processes and the potential therapeutic roles of NT in AD have not been determined. Here we examined the effects of NT on neuronal excitability and spatial learning in the EC, which expresses high density of NT receptors. Brief application of NT induced persistent increases in action potential firing frequency, which could last for at least 1 h. NT-induced facilitation of neuronal excitability was mediated by downregulation of TREK-2 K(+) channels and required the functions of NTS1, phospholipase C, and protein kinase C. Microinjection of NT or NTS1 agonist, PD149163, into the EC increased spatial learning as assessed by the Barnes Maze Test. Activation of NTS1 receptors also induced persistent increases in action potential firing frequency and significantly improved the memory status in APP/PS1 mice, an animal model of AD. Our study identifies a cellular substrate underlying learning and memory and suggests that NTS1 agonists may exert beneficial actions in an animal model of AD.
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23
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Enyedi P, Veres I, Braun G, Czirják G. Tubulin binds to the cytoplasmic loop of TRESK background K⁺ channel in vitro. PLoS One 2014; 9:e97854. [PMID: 24830385 PMCID: PMC4022642 DOI: 10.1371/journal.pone.0097854] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Accepted: 04/25/2014] [Indexed: 12/02/2022] Open
Abstract
The cytoplasmic loop between the second and third transmembrane segments is pivotal in the regulation of TRESK (TWIK-related spinal cord K+ channel, K2P18.1, KCNK18). Calcineurin binds to this region and activates the channel by dephosphorylation in response to the calcium signal. Phosphorylation-dependent anchorage of 14-3-3 adaptor protein also modulates TRESK at this location. In the present study, we identified molecular interacting partners of the intracellular loop. By an affinity chromatography approach using the cytoplasmic loop as bait, we have verified the specific association of calcineurin and 14-3-3 to the channel. In addition to these known interacting proteins, we observed substantial binding of tubulin to the intracellular loop. Successive truncation of the polypeptide and pull-down experiments from mouse brain cytosol narrowed down the region sufficient for the binding of tubulin to a 16 amino acid sequence: LVLGRLSYSIISNLDE. The first six residues of this sequence are similar to the previously reported tubulin-binding region of P2X2 purinergic receptor. The tubulin-binding site of TRESK is located close to the protein kinase A (PKA)-dependent 14-3-3-docking motif of the channel. We provide experimental evidence suggesting that 14-3-3 competes with tubulin for the binding to the cytoplasmic loop of TRESK. It is intriguing that the 16 amino acid tubulin-binding sequence includes the serines, which were previously shown to be phosphorylated by microtubule-affinity regulating kinases (MARK kinases) and contribute to channel inhibition. Although tubulin binds to TRESK in vitro, it remains to be established whether the two proteins also interact in the living cell.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Irén Veres
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Gabriella Braun
- Department of Physiology, Semmelweis University, Budapest, Hungary
| | - Gábor Czirják
- Department of Physiology, Semmelweis University, Budapest, Hungary
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24
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Guo Z, Liu P, Ren F, Cao YQ. Nonmigraine-associated TRESK K+ channel variant C110R does not increase the excitability of trigeminal ganglion neurons. J Neurophysiol 2014; 112:568-79. [PMID: 24805079 DOI: 10.1152/jn.00267.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent genetic studies suggest that dysfunction of ion channels and transporters may contribute to migraine pathophysiology. A migraine-associated frameshift mutation in the TWIK-related spinal cord K+ (TRESK) channel results in nonfunctional channels. Moreover, mutant TRESK subunits exert a dominant-negative effect on whole cell TRESK currents and result in hyperexcitability of small-diameter trigeminal ganglion (TG) neurons, suggesting that mutant TRESK may increase the gain of the neuronal circuit underlying migraine headache. However, the nonmigraine-associated TRESK C110R variant exhibits the same effect on TRESK currents as the mutant subunits in Xenopus oocytes, suggesting that dysfunction of TRESK is not sufficient to cause migraine. Here, we confirmed that the C110R variant formed nonfunctional channels and exerted a dominant-negative effect on TRESK currents in HEK293T cells, similar to the migraine-associated mutant TRESK. To compare the functional consequences of TRESK mutations/variants in a more physiological setting, we expressed the mutant TRESK and the C110R variant in cultured mouse TG neurons and investigated their effects on background K+ currents and neuronal excitability. Both mutant TRESK and the C110R variant reduced the endogenous TRESK currents in TG neurons, but the effect of the C110R variant was significantly smaller. Importantly, only TG neurons expressing mutant TRESK subunits, but not those expressing the C110R variant, exhibited a significant increase in excitability. Thus only the migraine-associated TRESK mutation, but not the C110R variant, reduces the endogenous TRESK currents to a degree that affects TG excitability. Our results support a potential causal relationship between the frameshift TRESK mutation and migraine susceptibility.
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Affiliation(s)
- Zhaohua Guo
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Ping Liu
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Fei Ren
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
| | - Yu-Qing Cao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri
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25
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Guo Z, Cao YQ. Over-expression of TRESK K(+) channels reduces the excitability of trigeminal ganglion nociceptors. PLoS One 2014; 9:e87029. [PMID: 24466320 PMCID: PMC3900698 DOI: 10.1371/journal.pone.0087029] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 12/20/2013] [Indexed: 01/17/2023] Open
Abstract
TWIK-related spinal cord K+ (TRESK) channel is abundantly expressed in trigeminal ganglion (TG) and dorsal root ganglion neurons and is one of the major background K+ channels in primary afferent neurons. Mutations in TRESK channels are associated with familial and sporadic migraine. In rats, both chronic nerve injury and inflammation alter the expression level of TRESK mRNA. Functional studies indicate that reduction of endogenous TRESK channel activity results in hyper-excitation of primary afferent neurons, suggesting that TRESK is a potential target for the development of new analgesics. However, whether and how enhancing TRESK channel activity would decrease the excitability of primary afferent neurons has not been directly tested. Here, we over-expressed TRESK subunits in cultured mouse TG neurons by lipofectamine-mediated transfection and investigated how this altered the membrane properties and the excitability of the small-diameter TG population. To account for the heterogeneity of neurons, we further divided small TG neurons into two groups, based on their ability to bind to fluorescently-labeled isolectin B (IB4). The transfected TG neurons showed a 2-fold increase in the level of TRESK proteins. This was accompanied by a significant increase in the fraction of lamotrigine-sensitive persistent K+ currents as well as the size of total background K+ currents. Consequently, both IB4-positive and IB4-negative TG neurons over-expressing TRESK subunits exhibited a lower input resistance and a 2-fold increase in the current threshold for action potential initiation. IB4-negative TG neurons over-expressing TRESK subunits also showed a significant reduction of the spike frequency in response to supra-threshold stimuli. Importantly, an increase in TRESK channel activity effectively inhibited capsaicin-evoked spikes in TG neurons. Taken together, our results suggest that potent and specific TRESK channel openers likely would reduce the excitability of primary afferent neurons and therefore are potential therapeutics for the treatment of migraine and other chronic pain symptoms.
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Affiliation(s)
- Zhaohua Guo
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Yu-Qing Cao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
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26
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Liu P, Xiao Z, Ren F, Guo Z, Chen Z, Zhao H, Cao YQ. Functional analysis of a migraine-associated TRESK K+ channel mutation. J Neurosci 2013; 33:12810-24. [PMID: 23904616 PMCID: PMC3728689 DOI: 10.1523/jneurosci.1237-13.2013] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 06/28/2013] [Accepted: 06/28/2013] [Indexed: 11/21/2022] Open
Abstract
Recent genetic and functional studies suggest that migraine may result from abnormal activities of ion channels and transporters. A frameshift mutation in the human TWIK-related spinal cord K(+) (TRESK) channel has been identified in migraine with aura patients in a large pedigree. In Xenopus oocytes, mutant TRESK subunits exert a dominant-negative effect on whole-cell TRESK currents. However, questions remain as to whether and how mutant TRESK subunits affect the membrane properties and the excitability of neurons in the migraine circuit. Here, we investigated the functional consequences of the mutant TRESK subunits in HEK293T cells and mouse trigeminal ganglion (TG) neurons. First, we found that mutant TRESK subunits exhibited dominant-negative effects not only on the size of the whole-cell TRESK currents, but also on the level of TRESK channels on the plasma membrane in HEK293T cells. This likely resulted from the heterodimerization of wild-type and mutant TRESK subunits. Next, we expressed mutant TRESK subunits in cultured TG neurons and observed a significant decrease in the lamotrigine-sensitive K(+) current, suggesting that the mutant TRESK subunits have a dominant-negative effect on currents through the endogenous TRESK channels. Current-clamp recordings showed that neurons expressing mutant TRESK subunits had a higher input resistance, a lower current threshold for action potential initiation, and a higher spike frequency in response to suprathreshold stimuli, indicating that the mutation resulted in hyperexcitability of TG neurons. Our results suggest a possible mechanism through which the TRESK mutation increases the susceptibility of migraine headache.
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Affiliation(s)
- Ping Liu
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Zheman Xiao
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Fei Ren
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Zhaohua Guo
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Ziwei Chen
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Hucheng Zhao
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Yu-Qing Cao
- Washington University Pain Center and
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110
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Rainero I, Rubino E, Paemeleire K, Gai A, Vacca A, De Martino P, Gentile S, Sarchielli P, Pinessi L. Genes and primary headaches: discovering new potential therapeutic targets. J Headache Pain 2013; 14:61. [PMID: 23848401 PMCID: PMC3716727 DOI: 10.1186/1129-2377-14-61] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 06/20/2013] [Indexed: 12/15/2022] Open
Abstract
Genetic studies have clearly shown that primary headaches (migraine, tension-type headache and cluster headache) are multifactorial disorders characterized by a complex interaction between different genes and environmental factors. Genetic association studies have highlighted a potential role in the etiopathogenesis of these disorders for several genes related to vascular, neuronal and neuroendocrine functions. A potential role as a therapeutic target is now emerging for some of these genes. The main purpose of this review is to describe new advances in our knowledge regarding the role of MTHFR, KCNK18, TRPV1, TRPV3 and HCRTR genes in primary headache disorders. Involvement of these genes in primary headaches, as well as their potential role in the therapy of these disorders, will be discussed.
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Affiliation(s)
- Innocenzo Rainero
- Headache Center, Neurology I, Department of Neuroscience, University of Torino, Via Cherasco 15, Torino 10126, Italy.
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28
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Sánchez-Miguel DS, García-Dolores F, Rosa Flores-Márquez M, Delgado-Enciso I, Pottosin I, Dobrovinskaya O. TRESK potassium channel in human T lymphoblasts. Biochem Biophys Res Commun 2013; 434:273-9. [PMID: 23541583 DOI: 10.1016/j.bbrc.2013.02.115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Accepted: 02/22/2013] [Indexed: 12/26/2022]
Abstract
TRESK (TWIK-related spinal cord K(+)) channel, encoded by KCNK18 gene, belongs to the double-pore domain K(+) channel family and in normal conditions is expressed predominantly in the central nervous system. In our previous patch-clamp study on Jurkat T lymphoblasts we have characterized highly selective K(+) channel with pharmacological profile identical to TRESK. In the present work, the presence of KCNK18 mRNA was confirmed in T lymphoblastic cell lines (Jurkat, JCaM, H9) but not in resting peripheral blood lymphocytes of healthy donors. Positive immunostaining for TRESK was demonstrated in lymphoblastic cell lines, in germinal centers of non-tumoral lymph nodes, and in clinical samples of T acute lymphoblastic leukemias/lymphomas. Besides detection in the plasma membrane, intracellular TRESK localization was also revealed. Possible involvement of TRESK channel in lymphocyte proliferation and tumorigenesis is discussed.
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Affiliation(s)
- Dénison Selene Sánchez-Miguel
- Center for Biomedical Research, University of Colima, Av. 25 de Julio 965, Villa San Sebastian, C.P. 28045 Colima, Mexico.
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29
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Intrathecal TRESK gene recombinant adenovirus attenuates spared nerve injury-induced neuropathic pain in rats. Neuroreport 2013; 24:131-6. [DOI: 10.1097/wnr.0b013e32835d8431] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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30
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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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31
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Ma L, Zhang X, Zhou M, Chen H. Acid-sensitive TWIK and TASK two-pore domain potassium channels change ion selectivity and become permeable to sodium in extracellular acidification. J Biol Chem 2012; 287:37145-53. [PMID: 22948150 DOI: 10.1074/jbc.m112.398164] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Two-pore domain K(+) channels (K2P) mediate background K(+) conductance and play a key role in a variety of cellular functions. Among the 15 mammalian K2P isoforms, TWIK-1, TASK-1, and TASK-3 K(+) channels are sensitive to extracellular acidification. Lowered or acidic extracellular pH (pH(o)) strongly inhibits outward currents through these K2P channels. However, the mechanism of how low pH(o) affects these acid-sensitive K2P channels is not well understood. Here we show that in Na(+)-based bath solutions with physiological K(+) gradients, lowered pH(o) largely shifts the reversal potential of TWIK-1, TASK-1, and TASK-3 K(+) channels, which are heterologously expressed in Chinese hamster ovary cells, into the depolarizing direction and significantly increases their Na(+) to K(+) relative permeability. Low pH(o)-induced inhibitions in these acid-sensitive K2P channels are more profound in Na(+)-based bath solutions than in channel-impermeable N-methyl-D-glucamine-based bath solutions, consistent with increases in the Na(+) to K(+) relative permeability and decreases in electrochemical driving forces of outward K(+) currents of the channels. These findings indicate that TWIK-1, TASK-1, and TASK-3 K(+) channels change ion selectivity in response to lowered pH(o), provide insights on the understanding of how extracellular acidification modulates acid-sensitive K2P channels, and imply that these acid-sensitive K2P channels may regulate cellular function with dynamic changes in their ion selectivity.
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Affiliation(s)
- Liqun Ma
- Department of Biological Sciences and the Center for Neuroscience Research, University at Albany, State University of New York, Albany, New York 12222, USA
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32
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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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33
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Enyedi P, Braun G, Czirják G. TRESK: the lone ranger of two-pore domain potassium channels. Mol Cell Endocrinol 2012; 353:75-81. [PMID: 22115960 DOI: 10.1016/j.mce.2011.11.009] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 11/02/2011] [Accepted: 11/08/2011] [Indexed: 12/14/2022]
Abstract
TRESK (TWIK-related spinal cord K(+) channel, KCNK18) belongs to the two-pore domain (K2P) background (leak) potassium channel family. Unlike other K2P channels, TRESK is activated by the calcium signal in heterologous expression systems. The activation is mediated by the calcium/calmodulin-dependent protein phosphatase, calcineurin. TRESK is abundantly expressed in dorsal root and trigeminal ganglia. The active ingredient of Sichuan pepper, sanshool, has been suggested to evoke tingling paresthesia by inhibiting the channel in a mechanoreceptor subpopulation of sensory neurons. Recently, dominant-negative mutation of human TRESK was found to be linked to migraine with aura in a large pedigree. It is hoped that future TRESK agonists may prevent or ameliorate the debilitating symptoms of migraine. It will be interesting to see whether the calcineurin-activated K(+) channel maintains normal excitability in the cerebral cortex thereby arresting cortical spreading depression (CSD), or prevents migraine attack only in the trigeminovascular (TGVS) system.
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Affiliation(s)
- Péter Enyedi
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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34
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Plant LD. A Role for K2P Channels in the Operation of Somatosensory Nociceptors. Front Mol Neurosci 2012; 5:21. [PMID: 22403526 PMCID: PMC3293133 DOI: 10.3389/fnmol.2012.00021] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 02/09/2012] [Indexed: 12/20/2022] Open
Abstract
The ability to sense mechanical, thermal, and chemical stimuli is critical to normal physiology and the perception of pain. Contact with noxious stimuli triggers a complex series of events that initiate innate protective mechanisms designed to minimize or avoid injury. Extreme temperatures, mechanical stress, and chemical irritants are detected by specific ion channels and receptors clustered on the terminals of nociceptive sensory nerve fibers and transduced into electrical information. Propagation of these signals, from distant sites in the body to the spinal cord and the higher processing centers of the brain, is also orchestrated by distinct groups of ion channels. Since their identification in 1995, evidence has emerged to support roles for K2P channels at each step along this pathway, as receptors for physiological and noxious stimuli, and as determinants of nociceptor excitability and conductivity. In addition, the many subtypes of K2P channels expressed in somatosensory neurons are also implicated in mediating the effects of volatile, general anesthetics on the central and peripheral nervous systems. Here, I offer a critical review of the existing data supporting these attributes of K2P channel function and discuss how diverse regulatory mechanisms that control the activity of K2P channels act to govern the operation of nociceptors.
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Affiliation(s)
- Leigh D Plant
- Department of Biochemistry, Brandeis University Waltham, MA, USA
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35
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Zhou J, Yao SL, Yang CX, Zhong JY, Wang HB, Zhang Y. TRESK gene recombinant adenovirus vector inhibits capsaicin-mediated substance P release from cultured rat dorsal root ganglion neurons. Mol Med Rep 2012; 5:1049-52. [PMID: 22307830 PMCID: PMC3493032 DOI: 10.3892/mmr.2012.778] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/19/2012] [Indexed: 12/03/2022] Open
Abstract
The present study was conducted to determine whether the activation of TRESK in the dorsal root ganglion (DRG) by the TRESK gene recombinant adenovirus vector inhibits the capsaicin-evoked substance P (SP) release using a radioimmunoassay. TRESK is an outwardly rectifying K+ current channel that contributes to the resting potential and is the most important background potassium channel in DRG. Previous studies have shown that neuropathic pain (NP) is closely related to the regulation of certain potassium channels in DRG neurons, while DRG-released SP is important in the peripheral mechanism of NP. In the present study, the TRESK gene adenovirus vector significantly enhanced the TRESK mRNA and protein of the cultured rat DRG neurons. Radioimmunoassay analysis revealed that the capsaicin-mediated SP release was significantly inhibited by the TRESK gene recombinant adenovirus vector in rat DRG neurons. These findings suggest that TRESK plays a role in adjusting the release of SP in DRG, which is related to NP.
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Affiliation(s)
- Jun Zhou
- Department of Anesthesiology, First People's Hospital of Foshan, Foshan, Guangdong, PR China.
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36
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Functional analysis of missense variants in the TRESK (KCNK18) K channel. Sci Rep 2012; 2:237. [PMID: 22355750 PMCID: PMC3266952 DOI: 10.1038/srep00237] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 12/23/2011] [Indexed: 01/13/2023] Open
Abstract
A loss of function mutation in the TRESK K2P potassium channel (KCNK18), has recently been linked with typical familial migraine with aura. We now report the functional characterisation of additional TRESK channel missense variants identified in unrelated patients. Several variants either had no apparent functional effect, or they caused a reduction in channel activity. However, the C110R variant was found to cause a complete loss of TRESK function, yet is present in both sporadic migraine and control cohorts, and no variation in KCNK18 copy number was found. Thus despite the previously identified association between loss of TRESK channel activity and migraine in a large multigenerational pedigree, this finding indicates that a single non-functional TRESK variant is not alone sufficient to cause typical migraine and highlights the genetic complexity of this disorder.
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37
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Mistry HD, McCallum LA, Kurlak LO, Greenwood IA, Broughton Pipkin F, Tribe RM. Novel expression and regulation of voltage-dependent potassium channels in placentas from women with preeclampsia. Hypertension 2011; 58:497-504. [PMID: 21730298 DOI: 10.1161/hypertensionaha.111.173740] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Preeclampsia is associated with structural/functional alterations in placental and maternal vasculature. Voltage-dependant potassium channels encoded by KCNQ1-5 genes have been detected in several types of blood vessels where they promote vascular relaxation. Voltage-dependant potassium channel function can be modulated by KCNE1-5-encoded accessory proteins. The aim of this study was to determine whether KCNQ and KCNE genes are differentially expressed in placentas from women with preeclampsia compared with normotensive controls and to examine any differences in those who delivered preterm (<37 weeks) or term. Placental biopsies (from midway between the cord and periphery) were obtained, with consent, from white European control (n=24; term) and preeclamptic (n=22; of whom 8 delivered before 37 weeks' gestation) women. KCNQ/KCNE and GAPDH mRNA expressions were determined by quantitative RT-PCR. Protein expression/localization was assessed using immunohistochemistry. KCNQ3 and KCNE5 mRNA expressions were significantly upregulated in preeclampsia (median [interquartile range]: 1.942 [0.905 to 3.379]) versus controls (0.159 [0.088 to 0.288]; P=0.001) and exhibited a strong positive correlation with each other (P<0.001), suggesting a novel heterodimer. Enhanced protein expression of KCNQ3 and KCNE5 in preeclampsia was confirmed with localization mainly restricted to the syncytiotrophoblast. KCNQ4 and KCNE1 isoforms were suppressed in placentas from term preeclamptic women versus controls (P≤0.05). KCNQ1 mRNA expression was increased and KCNQ5 decreased in the preterm preeclamptic group versus controls (P<0.05). In summary, voltage-dependant potassium channels are expressed and markedly modulated in placentas from preeclamptic women. Differential expression of isoforms may lead to altered cell proliferation. The correlation between KCNQ3 and KCNE5 expression is indicative of a novel channel complex and warrants further investigation.
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Affiliation(s)
- Hiten D Mistry
- Maternal and Fetal Research Unit, Division of Women's Health, King's College London, St Thomas' Hospital, Westminster Bridge Road, London SE1 7EH, UK.
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38
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Discrete change in volatile anesthetic sensitivity in mice with inactivated tandem pore potassium ion channel TRESK. Anesthesiology 2010; 113:1326-37. [PMID: 21042202 DOI: 10.1097/aln.0b013e3181f90ca5] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND We investigated the role of tandem pore potassium ion channel (K2P) TRESK in neurobehavioral function and volatile anesthetic sensitivity in genetically modified mice. METHODS Exon III of the mouse TRESK gene locus was deleted by homologous recombination using a targeting vector. The genotype of bred mice (wild type, knockout, or heterozygote) was determined using polymerase chain reaction. Morphologic and behavioral evaluations of TRESK knockout mice were compared with wild-type littermates. Sensitivity of bred mice to isoflurane, halothane, sevoflurane, and desflurane were studied by determining the minimum alveolar concentration preventing movement to tail clamping in 50% of each genotype. RESULTS With the exception of decreased number of inactive periods and increased thermal pain sensitivity (20% decrease in latency with hot plate test), TRESK knockout mice had healthy development and behavior. TRESK knockout mice showed a statistically significant 8% increase in isoflurane minimum alveolar concentration compared with wild-type littermates. Sensitivity to other volatile anesthetics was not significantly different. Spontaneous mortality of TRESK knockout mice after initial anesthesia testing was nearly threefold higher than that of wild-type littermates. CONCLUSIONS TRESK alone is not critical for baseline central nervous system function but may contribute to the action of volatile anesthetics. The inhomogeneous change in anesthetic sensitivity corroborates findings in other K2P knockout mice and supports the theory that the mechanism of volatile anesthetic action involves multiple targets. Although it was not shown in this study, a compensatory effect by other K2P channels may also contribute to these observations.
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39
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Deng PY, Xiao Z, Lei S. Distinct modes of modulation of GABAergic transmission by Group I metabotropic glutamate receptors in rat entorhinal cortex. Hippocampus 2010; 20:980-93. [PMID: 19739246 DOI: 10.1002/hipo.20697] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Activation of metabotropic glutamate receptors (mGluRs) modulates synaptic transmission, whereas the roles of mGluRs in GABAergic transmission in the entorhinal cortex (EC) are elusive. Here, we examined the effects of mGluRs on GABAergic transmission onto the principal neurons in the superficial layers of the EC. Bath application of DHPG, a selective Group I mGluR agonist, increased the frequency and amplitude of spontaneous IPSCs (sIPSCs) whereas application of DCG-IV, an agonist for Group II mGluRs or L-AP4, an agonist for Group III mGluRs failed to change significantly sIPSC frequency and amplitude. Bath application of DHPG failed to change significantly the frequency and amplitude of miniature IPSCs (mIPSCs) recorded in the presence of tetradotoxin but significantly reduced the amplitude of IPSCs evoked by extracellular field stimulation or in synaptically connected interneuron-pyramidal neuron pairs in layer III of the EC. DHPG increased the frequency but reduced the amplitude of APs recorded from entorhinal interneurons. Bath application of DHPG generated membrane depolarization and increased the input resistance of GABAergic interneurons. DHPG-mediated depolarization of GABAergic interneurons was mediated by inhibition of background K(+) channels which are insensitive to extracellular Cs(+), TEA, 4-AP, and Ba(2+). DHPG-induced facilitation of sIPSCs was mediated by mGluR(5) and required the function of Galphaq but was independent of phospholipase C activity. Elevation of synaptic glutamate concentration by bath application of glutamate transporter inhibitors significantly increased sIPSC frequency and amplitude demonstrating a physiological role of mGluRs in GABAergic transmission. Our results provide a cellular and molecular mechanism to explain the physiological and pathological roles of mGluRs in the EC.
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Affiliation(s)
- Pan-Yue Deng
- Department of Pharmacology, Physiology and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203, USA
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40
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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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41
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K+ transport characteristics of the plasma membrane tandem-pore channel TPK4 and pore chimeras with its vacuolar homologs. FEBS Lett 2010; 584:2433-9. [PMID: 20412800 DOI: 10.1016/j.febslet.2010.04.038] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2010] [Revised: 04/08/2010] [Accepted: 04/14/2010] [Indexed: 11/23/2022]
Abstract
Vacuolar tandem-pore channels could not be analysed in Xenopus oocytes so far, due to misguided translocation. Owing to the conservation of their pore regions, we were able to prepare functional pore-chimeras between the plasma membrane localised TPK4 and vacuolar TPKs. Thereby, we found evidence that TPK2, TPK3 and TPK5, just like TPK4, form potassium-selective channels with instantaneous current kinetics. Homology modelling and mutational analyses identified a pore-located aspartate residue (Asp110), which is involved in potassium permeation as well as in inward rectification of TPK4. Furthermore, dominant-negative mutations in the selectivity filter of either pore one or two (Asp86,Asp200) rendered TPK4 non-functional. This observation supports the notion that the functional TPK4 channel complex is formed by two subunits.
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42
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Czirják G, Enyedi P. TRESK background K(+) channel is inhibited by phosphorylation via two distinct pathways. J Biol Chem 2010; 285:14549-57. [PMID: 20215114 DOI: 10.1074/jbc.m110.102020] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The two-pore domain K(+) channel, TRESK (TWIK-related spinal cord K(+) channel, KCNK18) is directly regulated by the calcium/calmodulin-dependent phosphatase calcineurin and 14-3-3 adaptor proteins. The calcium signal robustly activates the channel via calcineurin, whereas the anchoring of 14-3-3 interferes with the return of the current to the resting state after the activation in Xenopus oocytes. In the present study, we report that the phosphorylation of TRESK at two distinct regulatory regions, the 14-3-3 binding site (Ser-264) and the cluster of three adjacent serine residues (Ser-274, Ser-276, and Ser-279), are responsible for channel inhibition. The phosphorylation of Ser-264 by protein kinase A accelerated the return of the current of S276E mutant TRESK to the resting state after the calcineurin-dependent activation. In the presence of 14-3-3, the basal current of the S276E mutant was reduced, and its calcineurin-dependent activation was augmented, suggesting that the direct binding of the adaptor protein to TRESK contributed to the basal inhibition of the channel under resting conditions. Unexpectedly, we found that 14-3-3 impeded the recovery of the current of S264E mutant TRESK to the resting state after the calcineurin-dependent activation, despite of the mutated 14-3-3 binding site. This suggests that 14-3-3 inhibited the kinase phosphorylating the regulatory cluster of Ser-274, Ser-276, and Ser-279, independently of the direct interaction between TRESK and 14-3-3. In conclusion, two distinct inhibitory kinase pathways converge on TRESK, and their effect on the calcineurin-dependent regulation is differentially modulated by the functional availability of 14-3-3.
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Affiliation(s)
- Gábor Czirják
- Department of Physiology, Semmelweis University, H-1444 Budapest, Hungary
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Gronich N, Kumar A, Zhang Y, Efimov IR, Soldatov NM. Molecular remodeling of ion channels, exchangers and pumps in atrial and ventricular myocytes in ischemic cardiomyopathy. Channels (Austin) 2010; 4:101-7. [PMID: 20090424 PMCID: PMC2891309 DOI: 10.4161/chan.4.2.10975] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Existing molecular knowledge base of cardiovascular diseases is rudimentary because of lack of specific attribution to cell type and function. The aim of this study was to investigate cell-specific molecular remodeling in human atrial and ventricular myocytes associated with ischemic cardiomyopathy. Our strategy combines two technological innovations, laser-capture microdissection of identified cardiac cells in selected anatomical regions of the heart and splice microarray of a narrow catalog of the functionally most important genes regulating ion homeostasis. We focused on expression of a principal family of genes coding for ion channels, exchangers and pumps (CE&P genes) that are involved in electrical, mechanical and signaling functions of the heart and constitute the most utilized drug targets. We found that (1) CE&P genes remodel in a cell-specific manner: ischemic cardiomyopathy affected 63 CE&P genes in ventricular myocytes and 12 essentially different genes in atrial myocytes. (2) Only few of the identified CE&P genes were previously linked to human cardiac disfunctions. (3) The ischemia-affected CE&P genes include nuclear chloride channels, adrenoceptors, cyclic nucleotide-gated channels, auxiliary subunits of Na(+), K(+) and Ca(2+) channels, and cell-surface CE&Ps. (4) In both atrial and ventricular myocytes ischemic cardiomyopathy reduced expression of CACNG7 and induced overexpression of FXYD1, the gene crucial for Na(+) and K(+) homeostasis. Thus, our cell-specific molecular profiling defined new landmarks for correct molecular modeling of ischemic cardiomyopathy and development of underlying targeted therapies.
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Affiliation(s)
- Naomi Gronich
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | - Azad Kumar
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | - Yuwei Zhang
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
| | | | - Nikolai M. Soldatov
- National Institute on Aging; National Institutes of health; Baltimore, MD USA
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N-linked glycosylation determines cell surface expression of two-pore-domain K+ channel TRESK. Biochem Biophys Res Commun 2010; 391:1262-7. [DOI: 10.1016/j.bbrc.2009.12.056] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2009] [Accepted: 12/09/2009] [Indexed: 11/21/2022]
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Han J, Kang D. TRESK channel as a potential target to treat T-cell mediated immune dysfunction. Biochem Biophys Res Commun 2009; 390:1102-5. [PMID: 19852929 DOI: 10.1016/j.bbrc.2009.10.076] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2009] [Accepted: 10/15/2009] [Indexed: 11/25/2022]
Abstract
In this review, we propose that TRESK background K(+) channel could serve as a potential therapeutic target for T-cell mediated immune dysfunction. TRESK has many immune function-related properties. TRESK is abundantly expressed in the thymus, the spleen, and human leukemic T-lymphocytes. TRESK is highly activated by Ca(2+), calcineurin, acetylcholine, and histamine which induce hypertrophy, whereas TRESK is inhibited by immunosuppressants, such as cyclosporin A and FK506. Cyclosporine A and FK506 target the binding site of nuclear factor of activated T-cells (NFAT) to inhibit calcineurin. Interestingly, TRESK possesses an NFAT-like docking site that is present at its intracellular loop. Calcineurin has been found to interact with TRESK via specific NFAT-like docking site. When the T-cell is activated, calcineurin can bind to the NFAT-docking site of TRESK. The activation of both TRESK and NFAT via Ca(2+)-calcineurin-NFAT/TRESK pathway could modulate the transcription of new genes in addition to regulating several aspects of T-cell function.
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Affiliation(s)
- Jaehee Han
- Medical Research Center for Neural Dysfunction, Department of Physiology, Institute of Health Sciences, Gyeongsang National University, School of Medicine, Jinju 660-751, Republic of Korea
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Deng PY, Xiao Z, Yang C, Rojanathammanee L, Grisanti L, Watt J, Geiger JD, Liu R, Porter JE, Lei S. GABA(B) receptor activation inhibits neuronal excitability and spatial learning in the entorhinal cortex by activating TREK-2 K+ channels. Neuron 2009; 63:230-43. [PMID: 19640481 DOI: 10.1016/j.neuron.2009.06.022] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 02/23/2009] [Accepted: 06/29/2009] [Indexed: 11/25/2022]
Abstract
The entorhinal cortex (EC) is regarded as the gateway to the hippocampus and thus is essential for learning and memory. Whereas the EC expresses a high density of GABA(B) receptors, the functions of these receptors in this region remain unexplored. Here, we examined the effects of GABA(B) receptor activation on neuronal excitability in the EC and spatial learning. Application of baclofen, a specific GABA(B) receptor agonist, inhibited significantly neuronal excitability in the EC. GABA(B) receptor-mediated inhibition in the EC was mediated via activating TREK-2, a type of two-pore domain K(+) channels, and required the functions of inhibitory G proteins and protein kinase A pathway. Depression of neuronal excitability in the EC underlies GABA(B) receptor-mediated inhibition of spatial learning as assessed by Morris water maze. Our study indicates that GABA(B) receptors exert a tight control over spatial learning by modulating neuronal excitability in the EC.
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Affiliation(s)
- Pan-Yue Deng
- Department of Pharmacology, Physiology, and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, ND 58203, USA
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Yoo S, Liu J, Sabbadini M, Au P, Xie GX, Yost CS. Regional expression of the anesthetic-activated potassium channel TRESK in the rat nervous system. Neurosci Lett 2009; 465:79-84. [PMID: 19716403 DOI: 10.1016/j.neulet.2009.08.062] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 08/19/2009] [Accepted: 08/24/2009] [Indexed: 01/22/2023]
Abstract
The two-pore-domain potassium (K(2P)) channels contribute to background (leak) potassium currents maintaining the resting membrane potential to play an important role in regulating neuronal excitability. As such they may contribute to nociception and the mechanism of action of volatile anesthetics. In the present study, we examined the protein expression pattern of the K(2P) channel TRESK in the rat central nervous system (CNS) and peripheral nervous system (PNS) by immunohistochemistry. The regional distribution expression pattern of TRESK has both similarities and significant differences from that of other K(2P) channels expressed in the CNS. TRESK expression is broadly found in the brain, spinal cord and dorsal root ganglia (DRG). TRESK expression is highest in important CNS structures, such as specific cortical layers, periaqueductal gray (PAG), granule cell layer of the cerebellum, and dorsal horn of the spinal cord. TRESK expression is also high in small and medium sized DRG neurons. These results provide an anatomic basis for identifying functional roles of TRESK in the rat nervous system.
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Affiliation(s)
- SieHyeon Yoo
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, 513 Parnassus Avenue, Room S-261, San Francisco, CA 94143, USA
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Xiao Z, Deng PY, Yang C, Lei S. Modulation of GABAergic transmission by muscarinic receptors in the entorhinal cortex of juvenile rats. J Neurophysiol 2009; 102:659-69. [PMID: 19494196 DOI: 10.1152/jn.00226.2009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Whereas the entorhinal cortex (EC) receives profuse cholinergic innervations from the basal forebrain and activation of cholinergic receptors has been shown to modulate the activities of the principal neurons and promote the intrinsic oscillations in the EC, the effects of cholinergic receptor activation on GABAergic transmission in this brain region have not been determined. We examined the effects of muscarinic receptor activation on GABA(A) receptor-mediated synaptic transmission in the superficial layers of the EC. Application of muscarine dose-dependently increased the frequency and amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) recorded from the principal neurons in layer II/III via activation of M(3) muscarinic receptors. Muscarine slightly reduced the frequency but had no effects on the amplitude of miniature IPSCs recorded in the presence of tetrodotoxin. Muscarine reduced the amplitude of IPSCs evoked by extracellular field stimulation and by depolarization of GABAergic interneurons in synaptically connected interneuron and pyramidal neuron pairs. Application of muscarine generated membrane depolarization and increased action potential firing frequency but reduced the amplitude of action potentials in GABAergic interneurons. Muscarine-induced depolarization of GABAergic interneurons was mediated by inhibition of background K(+) channels and independent of phospholipase C, intracellular Ca(2+) release, and protein kinase C. Our results demonstrate that activation of muscarinic receptors exerts diverse effects on GABAergic transmission in the EC.
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Affiliation(s)
- Zhaoyang Xiao
- Department of Pharmacology, Physiology and Therapeutics, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58203, USA
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Jang I, La JH, Kim GT, Lee JS, Kim EJ, Lee ES, Kim SJ, Seo JM, Ahn SH, Park JY, Hong SG, Kang D, Han J. Single-Channel Recording of TASK-3-like K Channel and Up-Regulation of TASK-3 mRNA Expression after Spinal Cord Injury in Rat Dorsal Root Ganglion Neurons. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:245-51. [PMID: 19967063 DOI: 10.4196/kjpp.2008.12.5.245] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Single-channel recordings of TASK-1 and TASK-3, members of two-pore domain K(+) channel family, have not yet been reported in dorsal root ganglion (DRG) neurons, even though their mRNA and activity in whole-cell currents have been detected in these neurons. Here, we report single-channel kinetics of the TASK-3-like K(+) channel in DRG neurons and up-regulation of TASK-3 mRNA expression in tissues isolated from animals with spinal cord injury (SCI). In DRG neurons, the single-channel conductance of TASK-3-like K(+) channel was 33.0+/-0.1 pS at -60 mV, and TASK-3 activity fell by 65+/-5% when the extracellular pH was changed from 7.3 to 6.3, indicating that the DRG K(+) channel is similar to cloned TASK-3 channel. TASK-3 mRNA and protein levels in brain, spinal cord, and DRG were significantly higher in injured animals than in sham-operated ones. These results indicate that TASK-3 channels are expressed and functional in DRG neurons and the expression level is up-regulated following SCI, and suggest that TASK-3 channel could act as a potential background K(+) channel under SCI-induced acidic condition.
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Affiliation(s)
- Inseok Jang
- Department of Thoracic Surgery, College of Medicine and Institute of Health Sciences, Gyeongsang National University, Jinju 660-751, Korea
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Heitzmann D, Warth R. Physiology and pathophysiology of potassium channels in gastrointestinal epithelia. Physiol Rev 2008; 88:1119-82. [PMID: 18626068 DOI: 10.1152/physrev.00020.2007] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cells of the gastrointestinal tract are an important barrier between the "milieu interne" and the luminal content of the gut. They perform transport of nutrients, salts, and water, which is essential for the maintenance of body homeostasis. In these epithelia, a variety of K(+) channels are expressed, allowing adaptation to different needs. This review provides an overview of the current literature that has led to a better understanding of the multifaceted function of gastrointestinal K(+) channels, thereby shedding light on pathophysiological implications of impaired channel function. For instance, in gastric mucosa, K(+) channel function is a prerequisite for acid secretion of parietal cells. In epithelial cells of small intestine, K(+) channels provide the driving force for electrogenic transport processes across the plasma membrane, and they are involved in cell volume regulation. Fine tuning of salt and water transport and of K(+) homeostasis occurs in colonic epithelia cells, where K(+) channels are involved in secretory and reabsorptive processes. Furthermore, there is growing evidence for changes in epithelial K(+) channel expression during cell proliferation, differentiation, apoptosis, and, under pathological conditions, carcinogenesis. In the future, integrative approaches using functional and postgenomic/proteomic techniques will help us to gain comprehensive insights into the role of K(+) channels of the gastrointestinal tract.
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Affiliation(s)
- Dirk Heitzmann
- Institute of Physiology and Clinic and Policlinic for Internal Medicine II, Regensburg, Germany
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