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Zylbergold P, Ramakrishnan N, Hebert T. The role of G proteins in assembly and function of Kir3 inwardly rectifying potassium channels. Channels (Austin) 2010; 4:411-21. [PMID: 20855978 DOI: 10.4161/chan.4.5.13327] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Kir3 channels (also known as GIRK channels) are important regulators of electrical excitability in both cardiomyocytes and neurons. Much is known regarding the assembly and function of these channels and the roles that their interacting proteins play in controlling these events. Further, they are one of the best studied effectors of heterotrimeric G proteins in general and Gβγ subunits in particular. However, our understanding of the roles of multiple Gβγ binding sites on Kir3 channels is still rudimentary. We discuss potential roles for Gβγ in channel assembly and trafficking in addition to their known role in cellular signaling.
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Affiliation(s)
- Peter Zylbergold
- Department of Pharmacology and Therapeutics, McGill University, Québec, Canada
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Honda S, Kawaura K, Soeda F, Shirasaki T, Takahama K. The potent inhibitory effect of tipepidine on marble-burying behavior in mice. Behav Brain Res 2010; 216:308-12. [PMID: 20713091 DOI: 10.1016/j.bbr.2010.08.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2010] [Revised: 08/03/2010] [Accepted: 08/08/2010] [Indexed: 10/19/2022]
Abstract
Our previous study revealed that centrally acting non-narcotic antitussives inhibited G-protein-coupled inwardly rectifying K(+) (GIRK) channel currents in brain neurons, and that the tipepidine antitussives had a novel antidepressive-like effect on rats. Furthermore, the antitussives revealed multiplexed ameliorating actions on intractable brain disease models. This study evaluated the therapeutic potential of tipepidine in obsessive-compulsive disorder (OCD) subjects using marble-burying behavior (MBB) tests in mice. In fact, OCD is classified as an anxiety disorder characterized by obsession or compulsion. Although selective 5-HT reuptake inhibitors (SSRIs) are considered first choice agents for the pharmacological treatment of OCD, 50% of patients with OCD failed to respond to SSRIs. The burying of harmless objects such as marbles by mice might reflect the formation of compulsive behavior. The results show that tipepidine reduced MBB in a dose-dependent manner. The effect of tipepidine was significant even at a dosage as small as 5 mg/kg. The tipepidine at 10 mg/kg s.c. nearly abolished MBB without reducing the locomotor activity in mice. It is particularly interesting that the dopamine D₂ antagonist or 5-HT(1A) antagonist partly inhibited the effect of tipepidine on MBB. The results suggest that tipepidine has more of a potent inhibitory effect on MBB, compared with known drugs used for the treatment of OCD, and that the tipepidine action mechanism might differ from that of known drugs.
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Affiliation(s)
- Sokichi Honda
- Department of Environmental and Molecular Health Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan
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Emerging roles for G protein-gated inwardly rectifying potassium (GIRK) channels in health and disease. Nat Rev Neurosci 2010; 11:301-15. [PMID: 20389305 DOI: 10.1038/nrn2834] [Citation(s) in RCA: 456] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels hyperpolarize neurons in response to activation of many different G protein-coupled receptors and thus control the excitability of neurons through GIRK-mediated self-inhibition, slow synaptic potentials and volume transmission. GIRK channel function and trafficking are highly dependent on the channel subunit composition. Pharmacological investigations of GIRK channels and studies in animal models suggest that GIRK activity has an important role in physiological responses, including pain perception and memory modulation. Moreover, abnormal GIRK function has been implicated in altering neuronal excitability and cell death, which may be important in the pathophysiology of diseases such as epilepsy, Down's syndrome, Parkinson's disease and drug addiction. GIRK channels may therefore prove to be a valuable new therapeutic target.
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Hibino H, Inanobe A, Furutani K, Murakami S, Findlay I, Kurachi Y. Inwardly rectifying potassium channels: their structure, function, and physiological roles. Physiol Rev 2010; 90:291-366. [PMID: 20086079 DOI: 10.1152/physrev.00021.2009] [Citation(s) in RCA: 1082] [Impact Index Per Article: 77.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Inwardly rectifying K(+) (Kir) channels allow K(+) to move more easily into rather than out of the cell. They have diverse physiological functions depending on their type and their location. There are seven Kir channel subfamilies that can be classified into four functional groups: classical Kir channels (Kir2.x) are constitutively active, G protein-gated Kir channels (Kir3.x) are regulated by G protein-coupled receptors, ATP-sensitive K(+) channels (Kir6.x) are tightly linked to cellular metabolism, and K(+) transport channels (Kir1.x, Kir4.x, Kir5.x, and Kir7.x). Inward rectification results from pore block by intracellular substances such as Mg(2+) and polyamines. Kir channel activity can be modulated by ions, phospholipids, and binding proteins. The basic building block of a Kir channel is made up of two transmembrane helices with cytoplasmic NH(2) and COOH termini and an extracellular loop which folds back to form the pore-lining ion selectivity filter. In vivo, functional Kir channels are composed of four such subunits which are either homo- or heterotetramers. Gene targeting and genetic analysis have linked Kir channel dysfunction to diverse pathologies. The crystal structure of different Kir channels is opening the way to understanding the structure-function relationships of this simple but diverse ion channel family.
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Affiliation(s)
- Hiroshi Hibino
- Department of Pharmacology, Graduate School of Medicine and The Center for Advanced Medical Engineering and Informatics, Osaka University, Osaka 565-0871, Japan
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Nishizawa D, Nagashima M, Katoh R, Satoh Y, Tagami M, Kasai S, Ogai Y, Han W, Hasegawa J, Shimoyama N, Sora I, Hayashida M, Ikeda K. Association between KCNJ6 (GIRK2) gene polymorphisms and postoperative analgesic requirements after major abdominal surgery. PLoS One 2009; 4:e7060. [PMID: 19756153 PMCID: PMC2738941 DOI: 10.1371/journal.pone.0007060] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 08/13/2009] [Indexed: 12/21/2022] Open
Abstract
Opioids are commonly used as effective analgesics for the treatment of acute and chronic pain. However, considerable individual differences have been widely observed in sensitivity to opioid analgesics. We focused on a G-protein-activated inwardly rectifying potassium (GIRK) channel subunit, GIRK2, that is an important molecule in opioid transmission. In our initial polymorphism search, a total of nine single-nucleotide polymorphisms (SNPs) were identified in the whole exon, 5′-flanking, and exon-intron boundary regions of the KCNJ6 gene encoding GIRK2. Among them, G-1250A and A1032G were selected as representative SNPs for further association studies. In an association study of 129 subjects who underwent major open abdominal surgery, the A/A genotype in the A1032G SNP and -1250G/1032A haplotype were significantly associated with increased postoperative analgesic requirements compared with other genotypes and haplotypes. The total dose (mean±SEM) of rescue analgesics converted to equivalent oral morphine doses was 20.45±9.27 mg, 10.84±2.24 mg, and 13.07±2.39 mg for the A/A, A/G, and G/G genotypes in the A1032G SNP, respectively. Additionally, KCNJ6 gene expression levels in the 1032A/A subjects were significantly decreased compared with the 1032A/G and 1032G/G subjects in a real-time quantitative PCR analysis using human brain tissues, suggesting that the 1032A/A subjects required more analgesics because of lower KCNJ6 gene expression levels and consequently insufficient analgesic effects. The results indicate that the A1032G SNP and G-1250A/A1032G haplotype could serve as markers that predict increased analgesic requirements. Our findings will provide valuable information for achieving satisfactory pain control and open new avenues for personalized pain treatment.
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Affiliation(s)
- Daisuke Nishizawa
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Makoto Nagashima
- Department of Surgery, Toho University Sakura Medical Center, Sakura, Japan
| | - Ryoji Katoh
- Department of Surgery, Toho University Sakura Medical Center, Sakura, Japan
| | - Yasuo Satoh
- Department of Anesthesiology, Toho University Sakura Medical Center, Sakura, Japan
| | - Megumi Tagami
- Department of Anesthesiology, Toho University Sakura Medical Center, Sakura, Japan
| | - Shinya Kasai
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Yasukazu Ogai
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Wenhua Han
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Junko Hasegawa
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
| | - Naohito Shimoyama
- Department of Anesthesiology and Palliative Medicine, National Cancer Center, Tokyo, Japan
| | - Ichiro Sora
- Department of Biological Psychiatry, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Masakazu Hayashida
- Department of Anesthesiology, Saitama Medical University International Medical Center, Hidaka, Japan
| | - Kazutaka Ikeda
- Division of Psychobiology, Tokyo Institute of Psychiatry, Tokyo, Japan
- * E-mail:
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Abstract
The age of an experimental animal can be a critical variable, yet age matters are often overlooked within neuroscience. Many studies make use of young animals, without considering possible differences between immature and mature subjects. This is especially problematic when attempting to model traits or diseases that do not emerge until adulthood. In this commentary we discuss the reasons for this apparent bias in age of experimental animals, and illustrate the problem with a systematic review of published articles on long-term potentiation. Additionally, we review the developmental stages of a rat and discuss the difficulty of using the weight of an animal as a predictor of its age. Finally, we provide original data from our laboratory and review published data to emphasize that development is an ongoing process that does not end with puberty. Developmental changes can be quantitative in nature, involving gradual changes, rapid switches, or inverted U-shaped curves. Changes can also be qualitative. Thus, phenomena that appear to be unitary may be governed by different mechanisms at different ages. We conclude that selection of the age of the animals may be critically important in the design and interpretation of neurobiological studies.
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Affiliation(s)
- James Edgar McCutcheon
- Department of Cellular and Molecular Pharmacology, Rosalind Franklin University of Medicine and Science, The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064, USA
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58
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Abe K, Kato G, Katafuchi T, Tamae A, Furue H, Yoshimura M. Responses to 5-HT in morphologically identified neurons in the rat substantia gelatinosa in vitro. Neuroscience 2008; 159:316-24. [PMID: 19141313 DOI: 10.1016/j.neuroscience.2008.12.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Revised: 12/10/2008] [Accepted: 12/12/2008] [Indexed: 10/21/2022]
Abstract
Bath application of 5-HT (1-1000 muM) induced a tetrodotoxin (TTX)-resistant outward current at the holding membrane potential (V(H)) of -50 mV in 104/162 (64.2%) of substantia gelatinosa (SG) neurons from the rat spinal cord in vitro. The 5-HT-induced outward current was suppressed by an external solution containing Ba(2+), or a pipette solution containing Cs(2)SO(4) and tetraethylammonium. It was reversed near the equilibrium potential of the K(+) channel. The response to 5-HT was abolished 30 min after patch formation with a pipette solution containing guanosine-5-O-(2-thiodiphosphate)-S. The 5-HT-induced outward current was mimicked by a 5-HT(1A) agonist, (+/-)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide, and suppressed by a 5-HT(1A) antagonist, WAY100635, suggesting the 5HT(1A) receptor-mediated activation of K(+) channels in the outward current. In 11/162 (6.8%) SG neurons, 5-HT produced an inward current, which was mimicked by a 5-HT(3) agonist, 1-(m-chlorophenyl)-biguanide (mCPBG). The 5-HT-induced outward currents were observed in vertical cells (21/34) and small islet cells (11/34), while inward currents were induced in islet cells (1/5) and small islet (4/5) cells, but not in vertical cells. It is known that most vertical cells and islet cells in the SG are excitatory (glutamatergic) and inhibitory interneurons, respectively, while small islet cells consist of both excitatory and inhibitory neurons. Bath application of 5-HT or mCPBG increased the amplitude and the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs), but no neurons showed a decrease in sIPSC. Furthermore, frequency, but not amplitude, of miniature IPSCs increased with perfusion with 5-HT in the presence of TTX. These findings, taken together, suggest that 5-HT induces outward currents through 5-HT(1A) receptors in excitatory SG neurons. These findings also suggest that the inward currents are post- and presynaptically evoked through 5-HT(3) receptors, probably in inhibitory neurons.
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Affiliation(s)
- K Abe
- Department of Integrative Physiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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59
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Abstract
G protein-gated inwardly rectifying potassium (GIRK/Kir3) channels mediate the inhibitory effects of many neurotransmitters on excitable cells. Four Girk genes have been identified (Girk1-4). Whereas GIRK4 is associated with the cardiac GIRK channel, Girk4 expression has been detected in a few neuron populations. Here, we used a transgenic mouse expressing enhanced green fluorescent protein (EGFP) under the control of the Girk4 gene promoter to clarify the expression pattern of Girk4 in the brain. Although small subsets of EGFP-positive neurons were evident in some areas, prominent labeling was seen in the hypothalamus. EGFP expression was most pronounced in the ventromedial, paraventricular, and arcuate nuclei, neuron populations implicated in energy homeostasis. Consistent with a contribution of GIRK4-containing channels to energy balance, Girk4 knockout -/- mice were predisposed to late-onset obesity. By 9 months, Girk4-/- mice were approximately 25% heavier than wild-type controls, a difference attributed to greater body fat. Before the development of overweight, Girk4-/- mice exhibited a tendency toward greater food intake and an increased propensity to work for food in an operant task. Girk4-/- mice also exhibited reduced net energy expenditure, despite displaying elevated resting heart rates and core body temperatures. These data implicate GIRK4-containing channels in signaling crucial to energy homeostasis and body weight.
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60
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Intracellular complexes of the beta2 subunit of the nicotinic acetylcholine receptor in brain identified by proteomics. Proc Natl Acad Sci U S A 2007; 104:20570-5. [PMID: 18077321 DOI: 10.1073/pnas.0710314104] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Nicotine acetylcholine receptors (nAChRs) comprise a family of ligand-gated channels widely expressed in the mammalian brain. The beta2 subunit is an abundant protein subunit critically involved in the cognitive and behavioral properties of nicotine as well as in the mechanisms of nicotine addiction. In this work, we used matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-TOF MS/MS) to uncover protein interactions of the intracellular loop of the beta2 subunit and components of immunoprecipitated beta2-nAChR complexes from mouse brain. Using the beta2-knockout mouse to exclude nonspecific binding to the beta2 antibody, we identify 21 nAChR-interacting proteins (NIPs) expressed in brain. Western blot analysis confirmed the association between the beta2 subunit and candidate NIPs. Based on their functional profiles, the hypothesis is suggested that the identified NIPs can regulate the trafficking and signaling of the beta2-nAChR. Interactions of the beta2 subunit with NIPs such as G protein alpha, G protein-regulated inducer of neurite outgrowth 1, and G protein-activated K(+) channel 1 suggest a link between nAChRs and cellular G protein pathways. These findings reveal intracellular interactions of the beta2 subunit and may contribute to the understanding of the mechanisms of nAChR signaling and trafficking in neurons.
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61
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Aguado C, Colón J, Ciruela F, Schlaudraff F, Cabañero MJ, Perry C, Watanabe M, Liss B, Wickman K, Luján R. Cell type-specific subunit composition of G protein-gated potassium channels in the cerebellum. J Neurochem 2007; 105:497-511. [PMID: 18088366 DOI: 10.1111/j.1471-4159.2007.05153.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
G protein-gated inwardly rectifying potassium (GIRK/Kir3) channels regulate cellular excitability and neurotransmission. In this study, we used biochemical and morphological techniques to analyze the cellular and subcellular distributions of GIRK channel subunits, as well as their interactions, in the mouse cerebellum. We found that GIRK1, GIRK2, and GIRK3 subunits co-precipitated with one another in the cerebellum and that GIRK subunit ablation was correlated with reduced expression levels of residual subunits. Using quantitative RT-PCR and immunohistochemical approaches, we found that GIRK subunits exhibit overlapping but distinct expression patterns in various cerebellar neuron subtypes. GIRK1 and GIRK2 exhibited the most widespread and robust labeling in the cerebellum, with labeling particularly prominent in granule cells. A high degree of molecular diversity in the cerebellar GIRK channel repertoire is suggested by labeling seen in less abundant neuron populations, including Purkinje neurons (GIRK1/GIRK2/GIRK3), basket cells (GIRK1/GIRK3), Golgi cells (GIRK2/GIRK4), stellate cells (GIRK3), and unipolar brush cells (GIRK2/GIRK3). Double-labeling immunofluorescence and electron microscopies showed that GIRK subunits were mainly found at post-synaptic sites. Altogether, our data support the existence of rich GIRK molecular and cellular diversity, and provide a necessary framework for functional studies aimed at delineating the contribution of GIRK channels to synaptic inhibition in the cerebellum.
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Affiliation(s)
- Carolina Aguado
- Departamento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
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62
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Labouèbe G, Lomazzi M, Cruz HG, Creton C, Luján R, Li M, Yanagawa Y, Obata K, Watanabe M, Wickman K, Boyer SB, Slesinger PA, Lüscher C. RGS2 modulates coupling between GABAB receptors and GIRK channels in dopamine neurons of the ventral tegmental area. Nat Neurosci 2007; 10:1559-68. [PMID: 17965710 DOI: 10.1038/nn2006] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 10/01/2007] [Indexed: 02/07/2023]
Abstract
Agonists of GABA(B) receptors exert a bi-directional effect on the activity of dopamine (DA) neurons of the ventral tegmental area, which can be explained by the fact that coupling between GABA(B) receptors and G protein-gated inwardly rectifying potassium (GIRK) channels is significantly weaker in DA neurons than in GABA neurons. Thus, low concentrations of agonists preferentially inhibit GABA neurons and thereby disinhibit DA neurons. This disinhibition might confer reinforcing properties on addictive GABA(B) receptor agonists such as gamma-hydroxybutyrate (GHB) and its derivatives. Here we show that, in DA neurons of mice, the low coupling efficiency reflects the selective expression of heteromeric GIRK2/3 channels and is dynamically modulated by a member of the regulator of G protein signaling (RGS) protein family. Moreover, repetitive exposure to GHB increases the GABA(B) receptor-GIRK channel coupling efficiency through downregulation of RGS2. Finally, oral self-administration of GHB at a concentration that is normally rewarding becomes aversive after chronic exposure. On the basis of these results, we propose a mechanism that might underlie tolerance to GHB.
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Affiliation(s)
- Gwenaël Labouèbe
- Department of Basic Neurosciences, Medical Faculty, University of Geneva, 1, Michel- Servet, CH-1211 Geneva, Switzerland
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63
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Subunit stoichiometry of heterologously expressed G-protein activated inwardly rectifying potassium channels analysed by fluorescence intensity ratio measurement. Pflugers Arch 2007; 455:1017-24. [DOI: 10.1007/s00424-007-0358-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 09/21/2007] [Indexed: 11/25/2022]
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Eulitz D, Prüss H, Derst C, Veh RW. Heterogeneous Distribution of Kir3 Potassium Channel Proteins Within Dopaminergic Neurons in the Mesencephalon of the Rat Brain. Cell Mol Neurobiol 2007; 27:285-302. [PMID: 17235695 DOI: 10.1007/s10571-006-9118-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 09/06/2006] [Indexed: 11/25/2022]
Abstract
1. Dopaminergic neurons in the substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) of the ventral mesencephalon play an important role in the regulation of the parallel basal ganglia loops.2. We have raised affinity-purified polyclonal rabbit antibodies specific for all four members of the Kir3 family of inwardly rectifying potassium channels (Kir3.1-Kir3.4) to investigate the distribution of the channel proteins in the dopaminergic neurons of the rat mesencephalon at light and electron microscopic level. In addition, immunocytochemical double labeling with tyrosine hydroxylase (TH), a marker of dopaminergic neurons, were performed.3. All Kir3 channels were present in this region. However, the individual proteins showed differential cellular and subcellular distributions.4. Kir3.1 immunoreactivity was found in SNc fibers and some neurons of the substantia nigra pars reticulata (SNr). Few Kir3.3-positive neurons were found in the SNc. However, a strong Kir3.3 signal was identified in the SNr neuropil. Weak Kir3.4 staining was detected in neuronal somata as well as in dendritic fibers of both parts of the SN.5. In the VTA, Kir3.1, Kir3.3, and Kir3.4 showed only weak staining of neuropil structures. The distribution of the Kir3.2 channel protein was especially striking with strong labeling in the SNc and in the lateral but not central VTA.6. Our results suggest that the heterogeneously distributed Kir3.2 channel proteins could help to discriminate the dopaminergic neurons of VTA and SNc.
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Affiliation(s)
- Dirk Eulitz
- Centrum für Anatomie, Institut für Integrative Neuroanatomie, Charité-Universitätsmedizin Berlin, Philippstrasse 12, D-10115 Berlin, Germany
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65
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Loucif AJC, Bonnavion P, Macri B, Golmard JL, Boni C, Melfort M, Leonard G, Lesch KP, Adrien J, Jacquin TD. Gender-dependent regulation of G-protein-gated inwardly rectifying potassium current in dorsal raphe neurons in knock-out mice devoid of the 5-hydroxytryptamine transporter. ACTA ACUST UNITED AC 2007; 66:1475-88. [PMID: 17013926 DOI: 10.1002/neu.20321] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Agonists at G-protein-coupled receptors in neurons of the dorsal raphe nucleus (DRN) of knock-out mice devoid of the serotonin transporter (5-HTT(-/-)) exhibit lower efficacy to inhibit cellular discharge than in wild-type counterparts. Using patch-clamp whole-cell recordings, we found that a G-protein-gated inwardly rectifying potassium (GIRK) current is involved in the inhibition of spike discharge induced by 5-HT1A agonists (5-carboxamidotryptamine (5-CT) and (+/-)-2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide (8-OH-DPAT); 50 nM-30 microM) in both wild-type and 5-HTT(-/-) female and male mice. These effects were mimicked by 5'-guanylyl-imido-diphosphate (Gpp(NH)p; 400 microM) dialysis into cells with differences between genders. The 5-HTT(-/-) knock-out mutation reduced the current density induced by Gpp(NH)p in females but not in males. These data suggest that the decreased response of 5-HT1A receptors to agonists in 5-HTT(-/-) mutants reflects notably alteration in the coupling between G-proteins and GIRK channels in females but not in males. Accordingly, gender differences in central 5-HT neurotransmission appear to depend-at least in part-on sex-related variations in corresponding receptor-G protein signaling mechanisms.
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Affiliation(s)
- Alexandre Julien Châu Loucif
- UMR 677, INSERM/UPMC, NeuroPsychoPharmacologie, Faculté de Médecine Pierre et Marie Curie, Site Pitié-Salpêtrière, 91 Boulevard de l'Hôpital, 75634 Paris Cedex 13, France
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66
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Best TK, Siarey RJ, Galdzicki Z. Ts65Dn, a Mouse Model of Down Syndrome, Exhibits Increased GABAB-Induced Potassium Current. J Neurophysiol 2007; 97:892-900. [PMID: 17093127 DOI: 10.1152/jn.00626.2006] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Down syndrome (DS) is the most common nonheritable cause of mental retardation. DS is the result of the presence of an extra chromosome 21 and its phenotype may be a consequence of overexpressed genes from that chromosome. One such gene is Kcnj6/Girk2, which encodes the G-protein-coupled inward rectifying potassium channel subunit 2 (GIRK2). We have recently shown that the DS mouse model, Ts65Dn, overexpresses GIRK2 throughout the brain and in particular the hippocampus. Here we report that this overexpression leads to a significant increase (∼2-fold) in GABAB-mediated GIRK current in primary cultured hippocampal neurons. The dose response curves for peak and steady-state GIRK current density is significantly shifted left toward lower concentrations of baclofen in Ts65Dn neurons compared with diploid controls, consistent with increased functional expression of GIRK channels. Stationary fluctuation analysis of baclofen-induced GIRK current from Ts65Dn neurons indicated no significant change in single-channel conductance compared with diploid. However, significant increases in GIRK channel density was found in Ts65Dn neurons. In normalized baclofen-induced GIRK current and GIRK current kinetics no difference was found between diploid and Ts65Dn neurons, which suggests unimpaired mechanisms of interaction between GIRK channel and GABAB receptor. These results indicate that increased expression of GIRK2 containing channels have functional consequences that likely affect the balance between excitatory and inhibitory neuronal transmission.
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Affiliation(s)
- Tyler K Best
- Neuroscience Graduate Program, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA
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67
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David M, Richer M, Mamarbachi AM, Villeneuve LR, Dupré DJ, Hebert TE. Interactions between GABA-B1 receptors and Kir 3 inwardly rectifying potassium channels. Cell Signal 2006; 18:2172-81. [PMID: 16809021 DOI: 10.1016/j.cellsig.2006.05.014] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2006] [Accepted: 05/11/2006] [Indexed: 12/01/2022]
Abstract
gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the mammalian brain. It acts via both ionotropic GABA-A and metabotropic GABA-B receptors. We evaluated the interaction of receptors with members of the inwardly rectifying potassium (Kir 3) channel family, which also play an important role in neuronal transmission and membrane excitability. These channels are functionally regulated by GABA-B receptors. Possible physical interactions between GABA-B receptor and Kir 3 channels expressed in HEK cells were evaluated using Bioluminescence Resonance Energy Transfer (BRET) experiments, co-immunoprecipitation and confocal microscopy. Our data indicate that Kir 3 channels and Gbetagamma subunits can interact with the GABA-B(1) subunits independently of the GABA-B(2) subunit or Kir 3.4 which are ultimately responsible for their targetting to the cell surface. Thus signalling complexes containing GABA-B receptors, G proteins and Kir channels are formed shortly after biosynthesis most likely in the endoplasmic reticulum.
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Affiliation(s)
- Martin David
- Département de biochimie, Université de Montréal, Canada
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Harashima C, Jacobowitz DM, Witta J, Borke RC, Best TK, Siarey RJ, Galdzicki Z. Abnormal expression of the G-protein-activated inwardly rectifying potassium channel 2 (GIRK2) in hippocampus, frontal cortex, and substantia nigra of Ts65Dn mouse: a model of Down syndrome. J Comp Neurol 2006; 494:815-33. [PMID: 16374808 PMCID: PMC2929960 DOI: 10.1002/cne.20844] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ts65Dn, a mouse model of Down syndrome (DS), demonstrates abnormal hippocampal synaptic plasticity and behavioral abnormalities related to spatial learning and memory. The molecular mechanisms leading to these impairments have not been identified. In this study, we focused on the G-protein-activated inwardly rectifying potassium channel 2 (GIRK2) gene that is highly expressed in the hippocampus region. We studied the expression pattern of GIRK subunits in Ts65Dn and found that GIRK2 was overexpressed in all analyzed Ts65Dn brain regions. Interestingly, elevated levels of GIRK2 protein in the Ts65Dn hippocampus and frontal cortex correlated with elevated levels of GIRK1 protein. This suggests that heteromeric GIRK1-GIRK2 channels are overexpressed in Ts65Dn hippocampus and frontal cortex, which could impair excitatory input and modulate spike frequency and synaptic kinetics in the affected regions. All GIRK2 splicing isoforms examined were expressed at higher levels in the Ts65Dn in comparison to the diploid hippocampus. The pattern of GIRK2 expression in the Ts65Dn mouse brain revealed by in situ hybridization and immunohistochemistry was similar to that previously reported in the rodent brain. However, in the Ts65Dn mouse a strong immunofluorescent staining of GIRK2 was detected in the lacunosum molecular layer of the CA3 area of the hippocampus. In addition, tyrosine hydroxylase containing dopaminergic neurons that coexpress GIRK2 were more numerous in the substantia nigra compacta and ventral tegmental area in the Ts65Dn compared to diploid controls. In summary, the regional localization and the increased brain levels coupled with known function of the GIRK channel may suggest an important contribution of GIRK2 containing channels to Ts65Dn and thus to DS neurophysiological phenotypes.
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Affiliation(s)
- Chie Harashima
- Department of Anatomy, Physiology and Genetics, USUHS School of Medicine, Bethesda, MD
| | - David M. Jacobowitz
- Department of Anatomy, Physiology and Genetics, USUHS School of Medicine, Bethesda, MD
- Laboratory of Clinical Science, NIMH, Bethesda, MD
| | - Jassir Witta
- Department of Pharmacology, USUHS School of Medicine, Bethesda, MD
| | - Rosemary C. Borke
- Department of Anatomy, Physiology and Genetics, USUHS School of Medicine, Bethesda, MD
- Neuroscience Program, USUHS School of Medicine, Bethesda, MD
| | - Tyler K. Best
- Neuroscience Program, USUHS School of Medicine, Bethesda, MD
| | - Richard J. Siarey
- Department of Anatomy, Physiology and Genetics, USUHS School of Medicine, Bethesda, MD
| | - Zygmunt Galdzicki
- Department of Anatomy, Physiology and Genetics, USUHS School of Medicine, Bethesda, MD
- Neuroscience Program, USUHS School of Medicine, Bethesda, MD
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69
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70
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Huang CS, Shi SH, Ule J, Ruggiu M, Barker LA, Darnell RB, Jan YN, Jan LY. Common molecular pathways mediate long-term potentiation of synaptic excitation and slow synaptic inhibition. Cell 2005; 123:105-18. [PMID: 16213216 DOI: 10.1016/j.cell.2005.07.033] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2005] [Revised: 07/03/2005] [Accepted: 07/28/2005] [Indexed: 01/22/2023]
Abstract
Synaptic plasticity, the cellular correlate for learning and memory, involves signaling cascades in the dendritic spine. Extensive studies have shown that long-term potentiation (LTP) of the excitatory postsynaptic current (EPSC) through glutamate receptors is induced by activation of N-methyl-D-asparate receptor (NMDA-R)--the coincidence detector--and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Here we report that the same signaling pathway in the postsynaptic CA1 pyramidal neuron also causes LTP of the slow inhibitory postsynaptic current (sIPSC) mediated by metabotropic GABA(B) receptors (GABA(B)-Rs) and G protein-activated inwardly rectifying K(+) (GIRK) channels, both residing in dendritic spines as well as shafts. Indicative of intriguing differences in the regulatory mechanisms for excitatory and inhibitory synaptic plasticity, LTP of sIPSC but not EPSC was abolished in mice lacking Nova-2, a neuronal-specific RNA binding protein that is an autoimmune target in paraneoplastic opsoclonus myoclonus ataxia (POMA) patients with latent cancer, reduced inhibitory control of movements, and dementia.
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Affiliation(s)
- Cindy Shen Huang
- Howard Hughes Medical Institute and Departments of Physiology and Biochemistry, University of California, San Francisco, CA 94143, USA
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71
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Kaneda K, Kita H. Synaptically released GABA activates both pre- and postsynaptic GABA(B) receptors in the rat globus pallidus. J Neurophysiol 2005; 94:1104-14. [PMID: 16061489 DOI: 10.1152/jn.00255.2005] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The globus pallidus (GP) contains abundant GABAergic synapses and GABA(B) receptors. To investigate whether synaptically released GABA can activate pre- and postsynaptic GABA(B) receptors in the GP, physiological recordings were performed using rat brain slice preparations. Cell-attached recordings from GABA(A) antagonist-treated preparations revealed that repetitive local stimulation induced a GABA(B) antagonist-sensitive pause in spontaneous firings of GP neurons. Whole cell recordings revealed that the repetitive stimulation evoked fast excitatory postsynaptic potentials followed by a slow inhibitory postsynaptic potential (IPSP) in GP neurons. The slow IPSP was insensitive to a GABA(A) receptor antagonist, increased in amplitude with the application of ionotropic glutamate receptor antagonists, and was suppressed by the GABA(B) antagonist CGP55845. The reversal potential of the slow IPSP was close to the potassium equilibrium potential. These results suggest that synaptically released GABA activated postsynaptic GABA(B) receptors and induced the pause and the slow IPSP. On the other hand, in the neurons that were treated to block postsynaptic GABA(B) responses, CGP55845 increased the amplitudes of repetitive local stimulation-induced GABA(A)-mediated inhibitory postsynaptic currents (IPSCs) but not the ionotropic glutamate-mediated excitatory postsynaptic currents. Moreover, the GABA(B) receptor specific agonist baclofen reduced the frequency of miniature IPSCs without altering their amplitude distributions. These results suggest that synaptically released GABA also activated presynaptic GABA(B) autoreceptors, resulting in decreased GABA release in the GP. Together, we infer that both pre- and postsynaptic GABA(B) receptors may play crucial roles in the control of GP neuronal activity.
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Affiliation(s)
- Katsuyuki Kaneda
- Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis, TN 38163, USA
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72
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Mora SI, Escobar LI. Phosphorylation of a tyrosine at the N-terminus regulates the surface expression of GIRK5 homomultimers. FEBS Lett 2005; 579:3019-23. [PMID: 15896779 DOI: 10.1016/j.febslet.2005.04.056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2005] [Accepted: 04/22/2005] [Indexed: 11/27/2022]
Abstract
The G protein-coupled inwardly rectifying GIRK5 and Delta5GIRK5 splicing variants do not express functional potassium channels. In contrast, Delta25GIRK5 forms functional homomultimers in Xenopus laevis oocytes. A tyrosine is present at the N-term of the non-functional isoforms. We studied the effect of endogenous tyrosine phosphorylation on the GIRK5 surface and functional expression. Unlike wild type channels, GIRK5Y16A and Delta5GIRK5Y16A mutants displayed inwardly rectifying currents and inhibitors of Src tyrosine kinase promoted the traffiking of GIRK5 to the cell surface. This is the first evidence that endogenous phosphorylation of a tyrosine residue in a GIRK channel inhibits its surface expression.
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Affiliation(s)
- S Ivonne Mora
- Departamento de Fisiologia, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, 04510 Mexico, DF
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73
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Milovic S, Steinecker-Frohnwieser B, Schreibmayer W, Weigl LG. The sensitivity of G protein-activated K+ channels toward halothane is essentially determined by the C terminus. J Biol Chem 2004; 279:34240-9. [PMID: 15175324 DOI: 10.1074/jbc.m403448200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-activated K(+) channels (GIRKs or Kir3.x) are targets for the volatile anesthetic, halothane. When coexpressed with the m(2) acetylcholine (ACh) receptor in Xenopus oocytes, agonist-activated GIRK1(F137S)- and GIRK2-mediated currents are inhibited by halothane, whereas in the absence of ACh, high concentrations of halothane induce GIRK1(F137S)-mediated currents. To elucidate the molecular mechanism of halothane action on GIRK currents of different subunit compositions, we constructed deletion mutants of GIRK1(F137S) (GIRK1(Delta363*)) and GIRK2 (GIRK2(Delta356)) lacking the C-terminal ends, as well as chimeric GIRK channels. Mutated GIRK channels showed normal currents when activated by ACh but exhibited different pharmacological properties toward halothane. GIRK2(Delta356) showed no sensitivity against the inhibitory action of halothane but was activated by halothane in the absence of an agonist. GIRK1(Delta363*) was activated by halothane more efficiently. Currents mediated by chimeric channels were inhibited by anesthetic concentrations that were at least 30-fold lower than those necessary to decrease GIRK2 wild type currents. Glutathione S-transferase pulldown experiments did not show displacement of bound Gbetagamma by halothane, indicating that halothane does not interfere with Gbetagamma binding. Single channel experiments revealed an influence of halothane on the gating of the channels: The agonist-induced currents of GIRK1 and GIRK2, carried mainly by brief openings, were inhibited, whereas higher concentrations of the anesthetic promoted long openings of GIRK1 channels. Because the C terminus is crucial for these effects, an interaction of halothane with the channel seems to be involved in the mechanism of current modulation.
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Affiliation(s)
- Sergej Milovic
- Medical University of Vienna, Department of Anesthesia and Intensive Care Medicine (B), Währinger Gürtel 18-20, A-1090 Vienna, Austria
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74
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Grosse G, Eulitz D, Thiele T, Pahner I, Schröter S, Takamori S, Grosse J, Wickman K, Tapp R, Veh RW, Ottersen OP, Ahnert-Hilger G. Axonal sorting of Kir3.3 defines a GABA-containing neuron in the CA3 region of rodent hippocampus. Mol Cell Neurosci 2004; 24:709-24. [PMID: 14664820 DOI: 10.1016/s1044-7431(03)00234-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Hippocampal interneurons comprise a heterogeneous group of locally acting GABAergic neurons. In addition to their variability in cotransmitter content and receptor profile, they express a variety of potassium channels that specify their individual properties. Here we describe a new type of large GABA-containing neuron in rodent hippocampus that is characterized by an axonal sorting of the potassium channel Kir3.3. The parent cell bodies of the Kir3.3-positive axons are located in CA3, as assessed by primary cultures derived from hippocampal subareas. At postnatal day 14 these neurons appear at the border between stratum oriens and stratum pyramidale of CA3, from where their axons pass through stratum pyramidale to join the mossy fiber tract. In adult hippocampus, high levels of Kir3.3 channel protein exist in axons that run with the mossy fiber tract. Kir3.3 and the vesicular GABA transporter could be identified in subpopulations of large synaptic terminals that probably derive from Kir3.3 neurons. Axonal sorting of Kir3.3 appears to be typical of a group of large inhibitory neurons, including Purkinje cells and a novel type of interneuron in CA3. Kir3.3 neurons might modulate the activity of CA3 circuitries and consequently memory processing in the hippocampus.
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Affiliation(s)
- Gisela Grosse
- Institut für Anatomie der Charité, Humboldt-Universität zu Berlin, Schumannstrasse 20/21, 10117 Berlin, Germany
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75
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Cruz HG, Ivanova T, Lunn ML, Stoffel M, Slesinger PA, Lüscher C. Bi-directional effects of GABA(B) receptor agonists on the mesolimbic dopamine system. Nat Neurosci 2004; 7:153-9. [PMID: 14745451 DOI: 10.1038/nn1181] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2003] [Accepted: 12/24/2003] [Indexed: 12/21/2022]
Abstract
The rewarding effect of drugs of abuse is mediated by activation of the mesolimbic dopamine system, which is inhibited by putative anti-craving compounds. Interestingly, different GABA(B) receptor agonists can exert similarly opposing effects on the reward pathway, but the cellular mechanisms involved are unknown. Here we found that the coupling efficacy (EC(50)) of G-protein-gated inwardly rectifying potassium (GIRK, Kir3) channels to GABA(B) receptor was much lower in dopamine neurons than in GABA neurons of the ventral tegmental area (VTA), depending on the differential expression of GIRK subunits. Consequently, in rodent VTA slices, a low concentration of the canonical agonist baclofen caused increased activity, whereas higher doses eventually inhibited dopamine neurons. At behaviorally relevant dosages, baclofen activated GIRK channels in both cell types, but the drug of abuse gamma-hydroxy-butyric acid (GHB) activated GIRK channels only in GABAergic neurons. Thus GABA(B) receptor agonists exert parallel cellular and behavioral effects due to the cell-specific expression of GIRK subunits.
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Affiliation(s)
- Hans G Cruz
- Department of Basic Neurosciences, University of Geneva, 1 Michel Servet, CH-1211 Geneva 4, Switzerland
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76
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Coulson EJ, Reid K, Shipham KM, Morley S, Kilpatrick TJ, Bartlett PF. The role of neurotransmission and the Chopper domain in p75 neurotrophin receptor death signaling. PROGRESS IN BRAIN RESEARCH 2004; 146:41-62. [PMID: 14699955 DOI: 10.1016/s0079-6123(03)46003-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The role of p75 neurotrophin receptor (p75NTR) in mediating cell death is now well characterized, however, it is only recently that details of the death signaling pathway have become clearer. This review focuses on the importance of the juxtamembrane Chopper domain region of p75NTR in this process. Evidence supporting the involvement of K+ efflux, the apoptosome (caspase-9, apoptosis activating factor-1, APAF-1, and Bcl-xL), caspase-3, c-jun kinase, and p53 in the p75NTR cell death pathway is discussed and regulatory roles for the p75NTR ectodomain and death domain are proposed. The role of synaptic activity is also discussed, in particular the importance of neutrotransmitter-activated K+ channels acting as the gatekeepers of cell survival decisions during development and in neurodegenerative conditions.
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Affiliation(s)
- E J Coulson
- Queensland Brain Institute, University of Queensland, Brisbane, Qld, Australia.
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77
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Han J, Kang D, Kim D. Properties and modulation of the G protein-coupled K+ channel in rat cerebellar granule neurons: ATP versus phosphatidylinositol 4,5-bisphosphate. J Physiol 2003; 550:693-706. [PMID: 12807991 PMCID: PMC2343084 DOI: 10.1113/jphysiol.2003.042119] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cerebellar granule (CG) neurons express a G protein-gated K+ current (GIRK) that is involved in the neurotransmitter regulation of the excitatory input to the Purkinje fibres of the cerebellum. Here, we characterized the single-channel behaviour of GIRK in CG neurons, and examined the effects of several known modulators of GIRK and their putative physiological roles. Whole-cell GIRKs were activated by baclofen, a GABAB receptor agonist. In cell-attached patches, baclofen activated GIRK with a single-channel conductance of 34 pS and a mean open time of 0.5 ms. In inside-out patches, application of GTPgammaS to the cytoplasmic side activated GIRK with similar kinetic properties. Addition of 2 mM ATP resulted in a marked increase in GIRK activity and induced longer-lived openings with a mean open time of 2.3 ms (ATP-dependent gating). Brain cytosolic fraction or free fatty acids inhibited this effect of ATP, and this was reversed by addition of purified recombinant brain fatty acid binding protein. Applying phosphatidylinositol 4,5-bisphosphate (PIP2) to inside-out patches in place of ATP also increased GIRK activity; however, only an increase in the frequency of opening was observed. The stimulatory effect of PIP2 on GIRK activity was not inhibited by the cytosolic fraction. Following maximal activation by PIP2, ATP caused an additional 2.2-fold increase in GIRK activity. These results show that GIRKs in CG neurons are regulated by positive and negative modulators that affect frequency as well as open time duration. The net effect is that the ligand-activated GIRK is in the 'low activity' state associated with short-lived openings, mainly due to strong action of the cytosolic inhibitor of ATP-dependent gating. Our results also show that intracellular ATP modulates GIRK via pathways different from that of PIP2 in CG neurons.
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Affiliation(s)
- Jaehee Han
- Department of Physiology, Gyeonsang National University School of Medicine, Chinju, Korea
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78
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Kourrich S, Masmejean F, Martin-Eauclaire MF, Soumireu-Mourat B, Mourre C. Inwardly rectifying Kir3.1 subunit knockdown impairs learning and memory in an olfactory associative task in rat. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 113:97-106. [PMID: 12750011 DOI: 10.1016/s0169-328x(03)00096-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Inward-rectifier potassium channels gated by the direct action of G proteins are activated or inhibited by numerous neurotransmitters and they modulate neuronal excitability. Using an olfactory associative task, the effect of Kir3.1 subunit knockdown was tested on learning and memory. Repeated intracerebroventricular injections of antisense oligodeoxyribonucleotide to the Kir3.1 subunit significantly reduced hippocampal expression of its mRNA target determined by Western blotting. The antisense knockdown had no effect on locomotor and drinking activity or on attention processes. The reduction in Kir3.1 subunit impaired the learning of the odor associations and the procedural side of the task. This reduction correlated with the performance impairment. The results suggest that Kir3.1 channel activity is implicated in the memory processes.
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Affiliation(s)
- Saïd Kourrich
- Laboratoire de Neurobiologie Intégrative et Adaptative, UMR 6149, CNRS-Université de Provence, IBHOP, Faculté des Sciences de St Jérôme, Avenue Normandie-Niemen, 13397 Marseille, cedex 20, France
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79
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Morgan AD, Carroll ME, Loth AK, Stoffel M, Wickman K. Decreased cocaine self-administration in Kir3 potassium channel subunit knockout mice. Neuropsychopharmacology 2003; 28:932-8. [PMID: 12637950 DOI: 10.1038/sj.npp.1300100] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Multiple G protein-linked neurotransmitter systems have been implicated in the behavioral effects of cocaine. While actions of certain neurotransmitter receptor subtypes and transporters have been identified, the role of individual G protein-regulated enzymes and ion channels in the effects of cocaine remains unclear. Here, we assessed the contribution of G protein-gated, inwardly rectifying potassium (Kir3/GIRK) channels to the locomotor-stimulatory and reinforcing effects of cocaine using knockout mice lacking one or both of the key neuronal channel subunits, Kir3.2 and Kir3.3. Cocaine-stimulated increases in horizontal locomotor activity in wild-type, Kir3.2 knockout, Kir3.3 knockout, and Kir3.2/3.3 double knockout mice, with only minor differences observed between the mouse lines. In contrast, Kir3.2 and Kir3.3 knockout mice exhibited dramatically reduced intravenous self-administration of cocaine relative to wild-type mice over a range of cocaine doses. Paradoxically, Kir3.2/3.3 double knockout mice self-administered cocaine at levels significantly higher than either single knockout alone. These findings suggest that Kir3 channels play significant and complex roles in the reinforcing effect of cocaine.
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Affiliation(s)
- Andrew D Morgan
- Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA
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80
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Mitrovic I, Margeta-Mitrovic M, Bader S, Stoffel M, Jan LY, Basbaum AI. Contribution of GIRK2-mediated postsynaptic signaling to opiate and alpha 2-adrenergic analgesia and analgesic sex differences. Proc Natl Acad Sci U S A 2003; 100:271-6. [PMID: 12496346 PMCID: PMC140949 DOI: 10.1073/pnas.0136822100] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The analgesia produced by inhibitory G protein-coupled receptor agonists involves coordinated postsynaptic inhibition via G protein-coupled inwardly rectifying potassium channels (GIRKs) and presynaptic inhibition of neurotransmitter release through regulation of voltage-gated Ca(2+) channels. Here, we used mice lacking the GIRK2 channel subunit to assess the relative contribution of these two effector systems to nociceptive processing in male and female mice. Compared with female WT mice, male WT mice exhibited higher pain thresholds and enhanced opioid (morphine) and alpha(2)-adrenergic (clonidine) receptor-induced antinociception in a spinal reflex test. The GIRK2-null mutation reduced the "pain" threshold in male but not in female mice, effectively eliminating the sex differences in pain threshold. In addition, deletion of GIRK2 channels in mutant mice largely eliminated clonidine antinociception and significantly decreased morphine antinociception. Furthermore, the more pronounced morphine and clonidine-induced antinociception in male mice disappeared in the GIRK2 mutants. Based on the almost complete loss of clonidine-induced antinociception in the mutant mice, we conclude that it is primarily mediated by postsynaptic alpha(2)-adrenergic receptors. In contrast, the significant residual morphine effect in the mutant mice points to the presynaptic mu opioid receptor as a major contributor to its analgesic action. Finally, our results suggest that the reduced pain responsiveness of male compared with female mice results in part from GIRK2-coupled postsynaptic receptors that are activated by endogenous antinociceptive systems.
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Affiliation(s)
- Igor Mitrovic
- Department of Physiology, University of California, San Francisco, 94143, USA
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81
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Marker CL, Cintora SC, Roman MI, Stoffel M, Wickman K. Hyperalgesia and blunted morphine analgesia in G protein-gated potassium channel subunit knockout mice. Neuroreport 2002; 13:2509-13. [PMID: 12499858 DOI: 10.1097/00001756-200212200-00026] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Our aim was to determine whether G protein-gated potassium (Kir3) channels contribute to thermonociception and morphine analgesia. Western blotting was used to probe for the presence of Kir3.1, Kir3.2, Kir3.3, and Kir3.4 subunits in the mouse brain and spinal cord. Hot-plate paw-lick latencies for wild-type, Kir3.2 knockout, Kir3.3 knockout, and Kir3.4 knockout mice were measured at 52 degrees C and 55 degrees C, following the s.c. injection of either saline or 10 mg/kg morphine. Paw-lick latencies for Kir3.4 knockout mice were similar to those of wild-type mice, consistent with the restricted expression pattern of Kir3.4 subunit in the mouse brain. In contrast, Kir3.2 knockout and Kir3.3 knockout mice displayed hyperalgesia at both temperatures tested, and both Kir3.2 knockout and Kir3.3 knockout mice displayed shorter paw-lick latencies following morphine administration, with Kir3.2 knockout mice exhibiting the more dramatic phenotype. Kir3.2/Kir3.3 double knockout mice displayed a greater degree of hyperalgesia than either the Kir3.2 knockout or Kir3.3 knockout mice, while performing similarly to Kir3.2 knockout mice following morphine administration. We conclude that G protein-gated potassium channels containing Kir3.2 and/or Kir3.3 play a significant role in responses to moderate thermal stimuli. Furthermore, the activation of Kir3 channels containing the Kir3.2 subunit contributes to the analgesia evoked by a moderate dose of morphine. As such, receptor-independent Kir3 channel agonists may represent a novel and selective class of analgesic agent.
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Affiliation(s)
- Cheryl L Marker
- Laboratory of Metabolic Diseases, The Rockefeller University, New York, NY 10021, USA
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82
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Abstract
It is estimated that up to 30% of epilepsy patients are poorly treated with available anti-epileptic drugs (AEDs). Thus, there is a medical need for new AEDs with novel mechanisms of action to serve as alternate or adjunct therapy for the treatment of drug-resistant or refractory epilepsy. One potential anti-epileptic mechanism that has not yet been exploited is K(+) channel opening. Considerable genetic, molecular, physiological and pharmacological evidence now exists to support a role for K(+) channels such as KCNQ2/Q3, Kv1.1, KATP and GIRK2 in the control of neuronal excitability and epileptogenesis. Evidence supporting these K(+) channels as novel AED targets will be reviewed in the following article.
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Affiliation(s)
- Alan D Wickenden
- Icagen Inc, Suite 460, 4222 Emperor Boulevard, Durham, NC 27703, USA.
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83
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Zachariou V, Benoit-Marand M, Allen PB, Ingrassia P, Fienberg AA, Gonon F, Greengard P, Picciotto MR. Reduction of cocaine place preference in mice lacking the protein phosphatase 1 inhibitors DARPP 32 or Inhibitor 1. Biol Psychiatry 2002; 51:612-20. [PMID: 11955461 DOI: 10.1016/s0006-3223(01)01318-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Modulation of protein phosphorylation by dopamine is thought to play an important role in drug reward. Protein phosphatase-1 (PP-1) is known to mediate some of the changes in neuronal signaling that occur following activation of the dopaminergic system. METHODS Two endogenous inhibitors of PP-1 are dopamine and cyclic 3', 5' adenosine monophosphate-regulated phosphoprotein (DARPP-32) and Inhibitor-1 (I-1). Knockout mice lacking one or both of these PP-1 inhibitors were tested for responses to cocaine using in vivo amperometry and conditioned place preference. RESULTS Presynaptic dopaminergic function appears to be unaffected by these mutations because stimulation-evoked changes in extracellular dopamine levels were unchanged between wild type mice and mice lacking one or both of these PP-1 inhibitors. In contrast, conditioned place preference to cocaine is reduced in mice lacking DARPP-32, I-1, or both phosphoproteins. This does not appear to be due to a learning deficit because mice lacking both DARPP-32 and I-1 show normal passive avoidance learning. CONCLUSIONS These data imply that increased PP-1 function as a result of deficits in DARPP-32 or I-1 is sufficient to decrease the rewarding properties of cocaine. Furthermore, the mechanism for this altered cocaine place preference does not involve alteration of dopamine release or reuptake.
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Affiliation(s)
- Venetia Zachariou
- Department of Psychiatry, Yale University School of Medicine, 34 Park Street, New Haven, CT 06508, USA
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84
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Di Paolo G, Sankaranarayanan S, Wenk MR, Daniell L, Perucco E, Caldarone BJ, Flavell R, Picciotto MR, Ryan TA, Cremona O, De Camilli P. Decreased synaptic vesicle recycling efficiency and cognitive deficits in amphiphysin 1 knockout mice. Neuron 2002; 33:789-804. [PMID: 11879655 DOI: 10.1016/s0896-6273(02)00601-3] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The function of the clathrin coat in synaptic vesicle endocytosis is assisted by a variety of accessory factors, among which amphiphysin (amphiphysin 1 and 2) is one of the best characterized. A putative endocytic function of amphiphysin was supported by dominant-negative interference studies. We have now generated amphiphysin 1 knockout mice and found that lack of amphiphysin 1 causes a parallel dramatic reduction of amphiphysin 2 selectively in brain. Cell-free assembly of endocytic protein scaffolds is defective in mutant brain extracts. Knockout mice exhibit defects in synaptic vesicle recycling that are unmasked by stimulation and suggest impairments at multiple stages of the cycle. These defects correlate with increased mortality due to rare irreversible seizures and with major learning deficits, suggesting a critical role of amphiphysin for higher brain functions.
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Affiliation(s)
- Gilbert Di Paolo
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA
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85
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Weigl LG, Schreibmayer W. G protein-gated inwardly rectifying potassium channels are targets for volatile anesthetics. Mol Pharmacol 2001; 60:282-9. [PMID: 11455015 DOI: 10.1124/mol.60.2.282] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-gated inwardly rectifying potassium channels (GIRKs) are a family of homo- and hetero-oligomeric K(+) channels composed of different subunits (GIRK1 to 4 in mammals). GIRK4 and GIRK1 are found mainly in the atrium, whereas neuronal cells predominantly express the GIRK1, GIRK2, and GIRK3 isoforms. When activated, GIRK channels slow the firing rate of atrial myocytes and neuronal cells. Because of their key role in controlling excitability, we investigated the influence of a prototypic anesthetic, halothane, on GIRK channels of different subunit composition expressed in Xenopus laevis oocytes. Halothane enhanced background currents through hetero-oligomeric GIRK1/GIRK4 and homo-oligomeric GIRK1(F137S) channels but not through homo-oligomeric GIRK2 channels. This activation of basal current did not depend on the presence of coexpressed G protein-coupled receptors but instead required the presence of G(beta/gamma). In contrast to basal GIRK currents, the agonist-induced GIRK current (via coexpressed m2 muscarinic receptors) was inhibited by halothane. For GIRK1/GIRK4 and GIRK1(F137S) channels this inhibition was most pronounced at low concentrations of the anesthetic (0.1-0.3 mM) and occurred also when channels had been activated by guanosine-5'-O-(3-thio)triphosphate. This inhibition, however, was overridden by high concentrations of halothane (0.9 mM) and augmentation of the agonist-induced current was observed. This increase in agonist-induced current was never seen with GIRK2 homo-oligomeric channels. Agonist-induced currents mediated by GIRK2 channels were always inhibited by halothane with an IC(50) value of approximately 60 microM. These data suggest a direct interaction of halothane with GIRK channels.
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Affiliation(s)
- L G Weigl
- Department for Anaesthesia and General Intensive Care Medicine, University Hospital Vienna, Austria.
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86
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Corey S, Clapham DE. The Stoichiometry of Gbeta gamma binding to G-protein-regulated inwardly rectifying K+ channels (GIRKs). J Biol Chem 2001; 276:11409-13. [PMID: 11148218 DOI: 10.1074/jbc.m100058200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G-protein-coupled inwardly rectifying K(+) (GIRK; Kir3.x) channels are the primary effectors of numerous G-protein-coupled receptors. GIRK channels decrease cellular excitability by hyperpolarizing the membrane potential in cardiac cells, neurons, and secretory cells. Although direct regulation of GIRKs by the heterotrimeric G-protein subunit Gbetagamma has been extensively studied, little is known about the number of Gbetagamma binding sites per channel. Here we demonstrate that purified GIRK (Kir 3.x) tetramers can be chemically cross-linked to exogenously purified Gbetagamma subunits. The observed laddering pattern of Gbetagamma attachment to GIRK4 homotetramers was consistent with the binding of one, two, three, or four Gbetagamma molecules per channel tetramer. The fraction of channels chemically cross-linked to four Gbetagamma molecules increased with increasing Gbetagamma concentrations and approached saturation. These results suggest that GIRK tetrameric channels have four Gbetagamma binding sites. Thus, GIRK (Kir 3.x) channels, like the distantly related cyclic nucleotide-gated channels, are tetramers and exhibit a 1:1 subunit/ligand binding stoichiometry.
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Affiliation(s)
- S Corey
- Neuroscience Program, Mayo Foundation, Rochester, Minnesota 55905, USA
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