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Mitten EH, Souders A, Marron Fernandez de Velasco E, Aguado C, Luján R, Wickman K. Chronic ethanol exposure in mice evokes pre- and postsynaptic deficits in GABAergic transmission in ventral tegmental area GABA neurons. Br J Pharmacol 2024. [PMID: 39358985 DOI: 10.1111/bph.17335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 06/26/2024] [Accepted: 07/18/2024] [Indexed: 10/04/2024] Open
Abstract
BACKGROUND AND PURPOSE GABAergic neurons in mouse ventral tegmental area (VTA) exhibit elevated activity during withdrawal following chronic ethanol exposure. While increased glutamatergic input and decreased GABAA receptor sensitivity have been implicated, the impact of inhibitory signaling in VTA GABA neurons has not been fully addressed. EXPERIMENTAL APPROACH We used electrophysiological and ultrastructural approaches to assess the impact of chronic intermittent ethanol vapour exposure in mice on GABAergic transmission in VTA GABA neurons during withdrawal. We used CRISPR/Cas9 ablation to mimic a somatodendritic adaptation involving the GABAB receptor (GABABR) in ethanol-naïve mice to investigate its impact on anxiety-related behaviour. KEY RESULTS The frequency of spontaneous inhibitory postsynaptic currents was reduced in VTA GABA neurons following chronic ethanol treatment and this was reversed by GABABR inhibition, suggesting chronic ethanol strengthens the GABABR-dependent suppression of GABAergic input to VTA GABA neurons. Similarly, paired-pulse depression of GABAA receptor-dependent responses evoked by optogenetic stimulation of nucleus accumbens inputs from ethanol-treated mice was reversed by GABABR inhibition. Somatodendritic currents evoked in VTA GABA neurons by GABABR activation were reduced following ethanol exposure, attributable to the suppression of GIRK (Kir3) channel activity. Mimicking this adaptation enhanced anxiety-related behaviour in ethanol-naïve mice. CONCLUSIONS AND IMPLICATIONS Chronic ethanol weakens the GABAergic regulation of VTA GABA neurons in mice via pre- and postsynaptic mechanisms, likely contributing to their elevated activity during withdrawal and expression of anxiety-related behaviour. As anxiety can promote relapse during abstinence, interventions targeting VTA GABA neuron excitability could represent new therapeutic strategies for treatment of alcohol use disorder.
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Affiliation(s)
- Eric H Mitten
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA
| | - Anna Souders
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Carolina Aguado
- Instituto de Biomedicina de la UCLM (IB-UCLM), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
| | - Rafael Luján
- Instituto de Biomedicina de la UCLM (IB-UCLM), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, USA
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Luo H, Marron Fernandez E, Gansemer B, Frederick M, Aguado C, Luján R, Thayer SA, Wickman K. Amyloid-β oligomers trigger sex-dependent inhibition of GIRK channel activity in hippocampal neurons in mice. Sci Signal 2024; 17:eado4132. [PMID: 39353038 DOI: 10.1126/scisignal.ado4132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 09/10/2024] [Indexed: 10/04/2024]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by amyloid plaques and cognitive decline, the latter of which is thought to be driven by soluble oligomeric amyloid-β (oAβ). The dysregulation of G protein-gated inwardly rectifying K+ (GIRK; also known as Kir3) channels has been implicated in rodent models of AD. Here, seeking mechanistic insights, we uncovered a sex-dependent facet of GIRK-dependent signaling in AD-related amyloid pathophysiology. Synthetic oAβ1-42 suppressed GIRK-dependent signaling in hippocampal neurons from male mice, but not from female mice. This effect required cellular prion protein, the receptor mGluR5, and production of arachidonic acid by the phospholipase PLA2. Although oAβ suppressed GIRK channel activity only in male hippocampal neurons, intrahippocampal infusion of oAβ or genetic suppression of GIRK channel activity in hippocampal pyramidal neurons impaired performance on a memory test in both male and female mice. Moreover, genetic enhancement of GIRK channel activity in hippocampal pyramidal neurons blocked oAβ-induced cognitive impairment in both male and female mice. In APP/PS1 AD model mice, GIRK-dependent signaling was diminished in hippocampal CA1 pyramidal neurons from only male mice before cognitive deficit was detected. However, enhancing GIRK channel activity rescued cognitive deficits in older APP/PS1 mice of both sexes. Thus, whereas diminished GIRK channel activity contributes to cognitive deficits in male mice with increased oAβ burden, enhancing its activity may have therapeutic potential for both sexes.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | | | - Benjamin Gansemer
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - McKinzie Frederick
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Carolina Aguado
- Synaptic Structure Laboratory, Departmento de Ciencias Médicas, Instituto de Biomedicina, Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, Albacete 02006, Spain
| | - Rafael Luján
- Synaptic Structure Laboratory, Departmento de Ciencias Médicas, Instituto de Biomedicina, Facultad de Medicina, Universidad de Castilla-La Mancha, Campus Biosanitario, Albacete 02006, Spain
| | - Stanley A Thayer
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
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3
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Nguyen H, Glaaser IW, Slesinger PA. Direct modulation of G protein-gated inwardly rectifying potassium (GIRK) channels. Front Physiol 2024; 15:1386645. [PMID: 38903913 PMCID: PMC11187414 DOI: 10.3389/fphys.2024.1386645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/08/2024] [Indexed: 06/22/2024] Open
Abstract
Ion channels play a pivotal role in regulating cellular excitability and signal transduction processes. Among the various ion channels, G-protein-coupled inwardly rectifying potassium (GIRK) channels serve as key mediators of neurotransmission and cellular responses to extracellular signals. GIRK channels are members of the larger family of inwardly-rectifying potassium (Kir) channels. Typically, GIRK channels are activated via the direct binding of G-protein βγ subunits upon the activation of G-protein-coupled receptors (GPCRs). GIRK channel activation requires the presence of the lipid signaling molecule, phosphatidylinositol 4,5-bisphosphate (PIP2). GIRK channels are also modulated by endogenous proteins and other molecules, including RGS proteins, cholesterol, and SNX27 as well as exogenous compounds, such as alcohol. In the last decade or so, several groups have developed novel drugs and small molecules, such as ML297, GAT1508 and GiGA1, that activate GIRK channels in a G-protein independent manner. Here, we aim to provide a comprehensive overview focusing on the direct modulation of GIRK channels by G-proteins, PIP2, cholesterol, and novel modulatory compounds. These studies offer valuable insights into the underlying molecular mechanisms of channel function, and have potential implications for both basic research and therapeutic development.
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Affiliation(s)
| | | | - Paul A. Slesinger
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, United States
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Li J, Mei S, Mao X, Wan L, Wang H, Xiao B, Song Y, Gu W, Liu Y, Long L. De novo variants in KCNJ3 are associated with early-onset epilepsy. J Med Genet 2024; 61:319-324. [PMID: 37963718 DOI: 10.1136/jmg-2023-109201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 10/14/2023] [Indexed: 11/16/2023]
Abstract
BACKGROUND KCNJ3 encodes a subunit of G-protein-coupled inwardly rectifying potassium channels, which are important for cellular excitability and inhibitory neurotransmission. However, the genetic basis of KCNJ3 in epilepsy has not been determined. This study aimed to identify the pathogenic KCNJ3 variants in patients with epilepsy. METHODS Trio exome sequencing was performed to determine potential variants of epilepsy. Individuals with KCNJ3 variants were recruited for this study. Detailed clinical information and genetic data were obtained and systematically reviewed. Whole-cell patch-clamp recordings were performed to evaluate the functional consequences of the identified variants. RESULTS Two de novo missense variants (c.998T>C (p.Leu333Ser) and c.938G>A (p. Arg313Gln)) in KCNJ3 were identified in two unrelated families with epilepsy. The variants were absent from the gnomAD database and were assumed to be damaging or probably damaging using multiple bioinformatics tools. They were both located in the C-terminal domain. The amino acid residues were highly conserved among various species. Clinically, the seizures occurred at a young age and were under control after combined treatment. Electrophysiological analysis revealed that the KCNJ3 Leu333Ser and Arg313Gln variants significantly compromised the current activities and exhibited loss-of-function (LOF) effects. CONCLUSION Our findings suggest that de novo LOF variants in KCNJ3 are associated with early-onset epilepsy. Genetic testing of KCNJ3 in patients with epilepsy may serve as a strategy for precision medicine.
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Affiliation(s)
- Juan Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Clinical Research Center for Epileptic Disease of Hunan Province, Central South University, Changsha, Hunan, China
| | - Shiyue Mei
- Henan Provincial Key Laboratory of Children's Genetics and Metabolic Diseases, Children's Hospital Affiliated to Zhengzhou University, Zhengzhou, Henan, China
| | - Xiao Mao
- Department of Medical Genetics, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
- National Health Commission Key Laboratory for Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan, China
| | - Lily Wan
- Department of Anatomy & Neurobiology, Central South University Xiangya School of Medicine, Changsha, Hunan, China
| | - Hua Wang
- Department of Medical Genetics, Hunan Children's Hospital, Changsha, Hunan, China
| | - Bo Xiao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Clinical Research Center for Epileptic Disease of Hunan Province, Central South University, Changsha, Hunan, China
| | - Yanmin Song
- Department of Emergency Medicine, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Weiyue Gu
- Chigene (Beijing) Translational Medical Research Center Co. Ltd, Beijing, China
| | - Yan Liu
- Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Lili Long
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan, China
- Clinical Research Center for Epileptic Disease of Hunan Province, Central South University, Changsha, Hunan, China
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Popova D, Sun J, Chow HM, Hart RP. A critical review of ethanol effects on neuronal firing: A metabolic perspective. ALCOHOL, CLINICAL & EXPERIMENTAL RESEARCH 2024; 48:450-458. [PMID: 38217065 DOI: 10.1111/acer.15266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 12/22/2023] [Accepted: 01/02/2024] [Indexed: 01/14/2024]
Abstract
Ethanol metabolism is relatively understudied in neurons, even though changes in neuronal metabolism are known to affect their activity. Recent work demonstrates that ethanol is preferentially metabolized over glucose as a source of carbon and energy, and it reprograms neurons to a state of reduced energy potential and diminished capacity to utilize glucose once ethanol is exhausted. Ethanol intake has been associated with changes in neuronal firing and specific brain activity (EEG) patterns have been linked with risk for alcohol use disorder (AUD). Furthermore, a haplotype of the inwardly rectifying potassium channel subunit, GIRK2, which plays a critical role in regulating excitability of neurons, has been linked with AUD and shown to be directly regulated by ethanol. At the same time, overexpression of GIRK2 prevents ethanol-induced metabolic changes. Based on the available evidence, we conclude that the mechanisms underlying the effects of ethanol on neuronal metabolism are a novel target for developing therapies for AUD.
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Affiliation(s)
- Dina Popova
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
| | - Jacquelyne Sun
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, Hong Kong
| | - Hei-Man Chow
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong, Hong Kong
- Gerald Choa Neuroscience Institute, The Chinese University of Hong Kong, Hong Kong, Hong Kong
| | - Ronald P Hart
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
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Marron Fernandez de Velasco E, Tipps ME, Haider B, Souders A, Aguado C, Rose TR, Vo BN, DeBaker MC, Luján R, Wickman K. Ethanol-Induced Suppression of G Protein-Gated Inwardly Rectifying K +-Dependent Signaling in the Basal Amygdala. Biol Psychiatry 2023; 94:863-874. [PMID: 37068702 PMCID: PMC10576835 DOI: 10.1016/j.biopsych.2023.04.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 04/05/2023] [Accepted: 04/05/2023] [Indexed: 04/19/2023]
Abstract
BACKGROUND The basolateral amygdala (BLA) regulates mood and associative learning and has been linked to the development and persistence of alcohol use disorder. The GABABR (gamma-aminobutyric acid B receptor) is a promising therapeutic target for alcohol use disorder, and previous work suggests that exposure to ethanol and other drugs can alter neuronal GABABR-dependent signaling. The effect of ethanol on GABABR-dependent signaling in the BLA is unknown. METHODS GABABR-dependent signaling in the mouse BLA was examined using slice electrophysiology following repeated ethanol exposure. Neuron-specific viral genetic manipulations were then used to understand the relevance of ethanol-induced neuroadaptations in the basal amygdala subregion (BA) to mood-related behavior. RESULTS The somatodendritic inhibitory effect of GABABR activation on principal neurons in the basal but not the lateral subregion of the BLA was diminished following ethanol exposure. This adaptation was attributable to the suppression of GIRK (G protein-gated inwardly rectifying K+) channel activity and was mirrored by a redistribution of GABABR and GIRK channels from the surface membrane to internal sites. While GIRK1 and GIRK2 subunits are critical for GIRK channel formation in BA principal neurons, GIRK3 is necessary for the ethanol-induced neuroadaptation. Viral suppression of GIRK channel activity in BA principal neurons from ethanol-naïve mice recapitulated some mood-related behaviors observed in C57BL/6J mice during ethanol withdrawal. CONCLUSIONS The ethanol-induced suppression of GIRK-dependent signaling in BA principal neurons contributes to some of the mood-related behaviors associated with ethanol withdrawal in mice. Approaches designed to prevent this neuroadaptation and/or strengthen GIRK-dependent signaling may prove useful for the treatment of alcohol use disorder.
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Affiliation(s)
| | - Megan E Tipps
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Bushra Haider
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Anna Souders
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Carolina Aguado
- Departmento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla La Mancha, Campus Biosanitario, La Mancha, Albacete, Spain
| | - Timothy R Rose
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Baovi N Vo
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
| | - Margot C DeBaker
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota
| | - Rafael Luján
- Departmento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla La Mancha, Campus Biosanitario, La Mancha, Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota
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7
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Nguyen NH, Brodsky JL. The cellular pathways that maintain the quality control and transport of diverse potassium channels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194908. [PMID: 36638864 PMCID: PMC9908860 DOI: 10.1016/j.bbagrm.2023.194908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/20/2022] [Accepted: 01/03/2023] [Indexed: 01/12/2023]
Abstract
Potassium channels are multi-subunit transmembrane proteins that permit the selective passage of potassium and play fundamental roles in physiological processes, such as action potentials in the nervous system and organismal salt and water homeostasis, which is mediated by the kidney. Like all ion channels, newly translated potassium channels enter the endoplasmic reticulum (ER) and undergo the error-prone process of acquiring post-translational modifications, folding into their native conformations, assembling with other subunits, and trafficking through the secretory pathway to reach their final destinations, most commonly the plasma membrane. Disruptions in these processes can result in detrimental consequences, including various human diseases. Thus, multiple quality control checkpoints evolved to guide potassium channels through the secretory pathway and clear potentially toxic, aggregation-prone misfolded species. We will summarize current knowledge on the mechanisms underlying potassium channel quality control in the secretory pathway, highlight diseases associated with channel misfolding, and suggest potential therapeutic routes.
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Affiliation(s)
- Nga H Nguyen
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA.
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8
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Kochetkova TO, Maslennikov DN, Tolmacheva ER, Shubina J, Bolshakova AS, Suvorova DI, Degtyareva AV, Orlovskaya IV, Kuznetsova MV, Rachkova AA, Sukhikh GT, Rebrikov DV, Trofimov DY. De Novo Variant in the KCNJ9 Gene as a Possible Cause of Neonatal Seizures. Genes (Basel) 2023; 14:genes14020366. [PMID: 36833293 PMCID: PMC9956824 DOI: 10.3390/genes14020366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/16/2023] [Accepted: 01/25/2023] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND The reduction in next-generation sequencing (NGS) costs allows for using this method for newborn screening for monogenic diseases (MDs). In this report, we describe a clinical case of a newborn participating in the EXAMEN project (ClinicalTrials.gov Identifier: NCT05325749). METHODS The child presented with convulsive syndrome on the third day of life. Generalized convulsive seizures were accompanied by electroencephalographic patterns corresponding to epileptiform activity. Proband WES expanded to trio sequencing was performed. RESULTS A differential diagnosis was made between symptomatic (dysmetabolic, structural, infectious) neonatal seizures and benign neonatal seizures. There were no data in favor of the dysmetabolic, structural, or infectious nature of seizures. Molecular karyotyping and whole exome sequencing were not informative. Trio WES revealed a de novo variant in the KCNJ9 gene (1:160087612T > C, p.Phe326Ser, NM_004983), for which, according to the OMIM database, no association with the disease has been described to date. Three-dimensional modeling was used to predict the structure of the KCNJ9 protein using the known structure of its homologs. According to the predictions, Phe326Ser change possibly disrupts the hydrophobic contacts with the valine side chain. Destabilization of the neighboring structures may undermine the formation of GIRK2/GIRK3 tetramers necessary for their proper functioning. CONCLUSIONS We believe that the identified variant may be the cause of the disease in this patient but further studies, including the search for other patients with the KCNJ9 variants, are needed.
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Martín-Belmonte A, Aguado C, Alfaro-Ruiz R, Moreno-Martínez AE, de la Ossa L, Aso E, Gómez-Acero L, Shigemoto R, Fukazawa Y, Ciruela F, Luján R. Nanoscale alterations in GABAB receptors and GIRK channel organization on the hippocampus of APP/PS1 mice. Alzheimers Res Ther 2022; 14:136. [PMID: 36131327 PMCID: PMC9490896 DOI: 10.1186/s13195-022-01078-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 09/13/2022] [Indexed: 11/10/2022]
Abstract
Alzheimer’s disease (AD) is characterized by a reorganization of brain activity determining network hyperexcitability and loss of synaptic plasticity. Precisely, a dysfunction in metabotropic GABAB receptor signalling through G protein-gated inwardly rectifying K+ (GIRK or Kir3) channels on the hippocampus has been postulated. Thus, we determined the impact of amyloid-β (Aβ) pathology in GIRK channel density, subcellular distribution, and its association with GABAB receptors in hippocampal CA1 pyramidal neurons from the APP/PS1 mouse model using quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL) and proximity ligation in situ assay (P-LISA). In wild type mice, single SDS-FRL detection revealed a similar dendritic gradient for GIRK1 and GIRK2 in CA1 pyramidal cells, with higher densities in spines, and GIRK3 showed a lower and uniform distribution. Double SDS-FRL showed a co-clustering of GIRK2 and GIRK1 in post- and presynaptic compartments, but not for GIRK2 and GIRK3. Likewise, double GABAB1 and GIRK2 SDS-FRL detection displayed a high degree of co-clustering in nanodomains (40–50 nm) mostly in spines and axon terminals. In APP/PS1 mice, the density of GIRK2 and GIRK1, but not for GIRK3, was significantly reduced along the neuronal surface of CA1 pyramidal cells and in axon terminals contacting them. Importantly, GABAB1 and GIRK2 co-clustering was not present in APP/PS1 mice. Similarly, P-LISA experiments revealed a significant reduction in GABAB1 and GIRK2 interaction on the hippocampus of this animal model. Overall, our results provide compelling evidence showing a significant reduction on the cell surface density of pre- and postsynaptic GIRK1 and GIRK2, but not GIRK3, and a decline in GABAB receptors and GIRK2 channels co-clustering in hippocampal pyramidal neurons from APP/PS1 mice, thus suggesting that a disruption in the GABAB receptor–GIRK channel membrane assembly causes dysregulation in the GABAB signalling via GIRK channels in this AD animal model.
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10
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Luo H, Marron Fernandez de Velasco E, Wickman K. Neuronal G protein-gated K + channels. Am J Physiol Cell Physiol 2022; 323:C439-C460. [PMID: 35704701 PMCID: PMC9362898 DOI: 10.1152/ajpcell.00102.2022] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
G protein-gated inwardly rectifying K+ (GIRK/Kir3) channels exert a critical inhibitory influence on neurons. Neuronal GIRK channels mediate the G protein-dependent, direct/postsynaptic inhibitory effect of many neurotransmitters including γ-aminobutyric acid (GABA), serotonin, dopamine, adenosine, somatostatin, and enkephalin. In addition to their complex regulation by G proteins, neuronal GIRK channel activity is sensitive to PIP2, phosphorylation, regulator of G protein signaling (RGS) proteins, intracellular Na+ and Ca2+, and cholesterol. The application of genetic and viral manipulations in rodent models, together with recent progress in the development of GIRK channel modulators, has increased our understanding of the physiological and behavioral impact of neuronal GIRK channels. Work in rodent models has also revealed that neuronal GIRK channel activity is modified, transiently or persistently, by various stimuli including exposure drugs of abuse, changes in neuronal activity patterns, and aversive experience. A growing body of preclinical and clinical evidence suggests that dysregulation of GIRK channel activity contributes to neurological diseases and disorders. The primary goals of this review are to highlight fundamental principles of neuronal GIRK channel biology, mechanisms of GIRK channel regulation and plasticity, the nascent landscape of GIRK channel pharmacology, and the potential relevance of GIRK channels to the pathophysiology and treatment of neurological diseases and disorders.
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Affiliation(s)
- Haichang Luo
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States
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11
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Lee S, Kang BE, Song YK, Baker BJ. A trafficking motif alters GEVI activity implicating persistent protein interactions at the membrane. BIOPHYSICAL REPORTS 2022; 2:100047. [PMID: 36425771 PMCID: PMC9680705 DOI: 10.1016/j.bpr.2022.100047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Accepted: 02/18/2022] [Indexed: 11/30/2022]
Abstract
Efficient plasma-membrane expression is critical for genetically encoded voltage indicators (GEVIs). To improve the plasma-membrane expression, we introduced multiple combinations of plasma-membrane trafficking motifs at different positions to members of the Bongwoori family of GEVIs. An improvement from 20% to 27% in the ΔF/F/100 mV depolarization of the plasma membrane was observed when a Golgi transport motif was inserted near the N-terminus in conjunction with an endoplasmic reticulum release motif near the C-terminus of the protein. Unfortunately, this variant was also slower. The weighted tau on of the variant (25 ms) was more than double the original construct (11 ms). The weighted tau off was >20 ms compared with 10 ms for the original GEVI. The voltage range of the GEVI was also shifted to more negative potentials. Insertion of spacer amino acids between the fluorescent-protein domain and the endoplasmic reticulum release motif at the C-terminus rescued the speed of both the tau on and tau off while restoring the voltage range and maintaining the improved voltage-dependent optical signal. These results suggest that while trafficking motifs do improve plasma-membrane expression, they may also mediate persistent associations that affect the functioning of the protein.
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12
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Taylor EL, Weaver SR, Lorang IM, Arnold KM, Bradley EW, Marron Fernandez de Velasco E, Wickman K, Westendorf JJ. GIRK3 deletion facilitates kappa opioid signaling in chondrocytes, delays vascularization and promotes bone lengthening in mice. Bone 2022; 159:116391. [PMID: 35314385 PMCID: PMC9035100 DOI: 10.1016/j.bone.2022.116391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/03/2022] [Accepted: 03/14/2022] [Indexed: 11/29/2022]
Abstract
Long bones are formed and repaired through the process of endochondral ossification. Activation of G protein-coupled receptor (GPCR) signaling pathways is crucial for skeletal development and long bone growth. G protein-gated inwardly-rectifying K+ (GIRK) channel genes are key functional components and effectors of GPCR signaling pathways in excitable cells of the heart and brain, but their roles in non-excitable cells that directly contribute to endochondral bone formation have not been studied. In this study, we analyzed skeletal phenotypes of Girk2-/-, Girk3-/- and Girk2/3-/- mice. Bones from 12-week-old Girk2-/- mice were normal in length, but femurs and tibiae from Girk3-/- and Girk2/3-/- mice were longer than age-matched controls at 12-weeks-old. Epiphyseal chondrocytes from 5-day-old Girk3-/- mice expressed higher levels of genes involved in collagen chain trimerization and collagen fibril assembly, lower levels of genes encoding VEGF receptors, and produced larger micromasses than wildtype chondrocytes in vitro. Girk3-/- chondrocytes were also more responsive to the kappa opioid receptor (KOR) ligand dynorphin, as evidenced by greater pCREB expression, greater cAMP and GAG production, and upregulation of Col2a1 and Sox9 transcripts. Imaging studies showed that Kdr (Vegfr2) and endomucin expression was dramatically reduced in bones from young Girk3-/- mice, supporting a role for delayed vasculogenesis and extended postnatal endochondral bone growth. Together these data indicate that GIRK3 controls several processes involved in bone lengthening.
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Affiliation(s)
- Earnest L Taylor
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, United States of America; Department of Cell Biology, University of North Carolina, NC, United States of America
| | - Samantha R Weaver
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, United States of America
| | - Ian M Lorang
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, United States of America; University of Washington School of Medicine, Seattle, WA, United States of America
| | - Katherine M Arnold
- Mayo Clinic Graduate School of Biomedical Sciences, Mayo Clinic, Rochester, MN, United States of America
| | - Elizabeth W Bradley
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, United States of America; Department of Orthopedic Surgery, University of Minnesota, Minneapolis, MN, United States of America
| | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, MN, United States of America
| | - Jennifer J Westendorf
- Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN, United States of America; Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, United States of America.
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13
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Coyote-Maestas W, Nedrud D, He Y, Schmidt D. Determinants of trafficking, conduction, and disease within a K + channel revealed through multiparametric deep mutational scanning. eLife 2022; 11:e76903. [PMID: 35639599 PMCID: PMC9273215 DOI: 10.7554/elife.76903] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 05/27/2022] [Indexed: 01/04/2023] Open
Abstract
A long-standing goal in protein science and clinical genetics is to develop quantitative models of sequence, structure, and function relationships to understand how mutations cause disease. Deep mutational scanning (DMS) is a promising strategy to map how amino acids contribute to protein structure and function and to advance clinical variant interpretation. Here, we introduce 7429 single-residue missense mutations into the inward rectifier K+ channel Kir2.1 and determine how this affects folding, assembly, and trafficking, as well as regulation by allosteric ligands and ion conduction. Our data provide high-resolution information on a cotranslationally folded biogenic unit, trafficking and quality control signals, and segregated roles of different structural elements in fold stability and function. We show that Kir2.1 surface trafficking mutants are underrepresented in variant effect databases, which has implications for clinical practice. By comparing fitness scores with expert-reviewed variant effects, we can predict the pathogenicity of 'variants of unknown significance' and disease mechanisms of known pathogenic mutations. Our study in Kir2.1 provides a blueprint for how multiparametric DMS can help us understand the mechanistic basis of genetic disorders and the structure-function relationships of proteins.
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Affiliation(s)
- Willow Coyote-Maestas
- Department of Biochemistry, Molecular Biology and Biophysics, University of MinnesotaMinneapolisUnited States
| | - David Nedrud
- Department of Biochemistry, Molecular Biology and Biophysics, University of MinnesotaMinneapolisUnited States
| | - Yungui He
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
| | - Daniel Schmidt
- Department of Genetics, Cell Biology and Development, University of MinnesotaMinneapolisUnited States
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14
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Kasatkina LA, Verkhusha VV. Transgenic mice encoding modern imaging probes: Properties and applications. Cell Rep 2022; 39:110845. [PMID: 35613592 PMCID: PMC9183799 DOI: 10.1016/j.celrep.2022.110845] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/31/2022] [Accepted: 04/28/2022] [Indexed: 12/04/2022] Open
Abstract
Modern biology is increasingly reliant on optical technologies, including visualization and longitudinal monitoring of cellular processes. The major limitation here is the availability of animal models to track the molecules and cells in their natural environment in vivo. Owing to the integrity of the studied tissue and the high stability of transgene expression throughout life, transgenic mice encoding fluorescent proteins and biosensors represent unique tools for in vivo studies in norm and pathology. We review the strategies for targeting probe expression in specific tissues, cell subtypes, or cellular compartments. We describe the application of transgenic mice expressing fluorescent proteins for tracking protein expression patterns, apoptotic events, tissue differentiation and regeneration, neurogenesis, tumorigenesis, and cell fate mapping. We overview the possibilities of functional imaging of secondary messengers, neurotransmitters, and ion fluxes. Finally, we provide the rationale and perspectives for the use of transgenic imaging probes in translational research and drug discovery.
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Affiliation(s)
- Ludmila A Kasatkina
- Department of Genetics and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Vladislav V Verkhusha
- Department of Genetics and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA; Medicum, Faculty of Medicine, University of Helsinki, Helsinki 00290, Finland.
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15
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5-HT2A receptor dysregulation in a schizophrenia relevant mouse model of NMDA receptor hypofunction. Transl Psychiatry 2022; 12:168. [PMID: 35459266 PMCID: PMC9033804 DOI: 10.1038/s41398-022-01930-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 03/22/2022] [Accepted: 04/08/2022] [Indexed: 11/30/2022] Open
Abstract
Blockade of N-methyl-D-aspartate receptors (NMDAR) is known to augment cortical serotonin 2A receptors (5-HT2ARs), which is implicated in psychosis. However, the pathways from NMDAR hypofunction to 5-HT2AR up-regulation are unclear. Here we addressed in mice whether genetic deletion of the indispensable NMDAR-subunit Grin1 principally in corticolimbic parvalbumin-positive fast-spiking interneurons, could up-regulate 5-HT2ARs leading to cortical hyper-excitability. First, in vivo local-field potential recording revealed that auditory cortex in Grin1 mutant mice became hyper-excitable upon exposure to acoustic click-train stimuli that release 5-HT in the cortex. This excitability increase was reproduced ex vivo where it consisted of an increased frequency of action potential (AP) firing in layer 2/3 pyramidal neurons of mutant auditory cortex. Application of the 5-HT2AR agonist TCB-2 produced similar results. The effect of click-trains was reversed by the 5-HT2AR antagonist M100907 both in vivo and ex vivo. Increase in AP frequency of pyramidal neurons was also reversed by application of Gαq protein inhibitor BIM-46187 and G protein-gated inwardly-rectifying K+ (GIRK) channel activator ML297. In fast-spiking interneurons, 5-HT2AR activation normally promotes GABA release, contributing to decreased excitability of postsynaptic pyramidal neurons, which was missing in the mutants. Moreover, unlike the controls, the GABAA receptor antagonist (+)-bicuculline had little effect on AP frequency of mutant pyramidal neurons, indicating a disinhibition state. These results suggest that the auditory-induced hyper-excitable state is conferred via GABA release deficits from Grin1-lacking interneurons leading to 5-HT2AR dysregulation and GIRK channel suppression in cortical pyramidal neurons, which could be involved in auditory psychosis.
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16
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Coyote-Maestas W, Nedrud D, Suma A, He Y, Matreyek KA, Fowler DM, Carnevale V, Myers CL, Schmidt D. Probing ion channel functional architecture and domain recombination compatibility by massively parallel domain insertion profiling. Nat Commun 2021; 12:7114. [PMID: 34880224 PMCID: PMC8654947 DOI: 10.1038/s41467-021-27342-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 11/16/2021] [Indexed: 11/10/2022] Open
Abstract
Protein domains are the basic units of protein structure and function. Comparative analysis of genomes and proteomes showed that domain recombination is a main driver of multidomain protein functional diversification and some of the constraining genomic mechanisms are known. Much less is known about biophysical mechanisms that determine whether protein domains can be combined into viable protein folds. Here, we use massively parallel insertional mutagenesis to determine compatibility of over 300,000 domain recombination variants of the Inward Rectifier K+ channel Kir2.1 with channel surface expression. Our data suggest that genomic and biophysical mechanisms acted in concert to favor gain of large, structured domain at protein termini during ion channel evolution. We use machine learning to build a quantitative biophysical model of domain compatibility in Kir2.1 that allows us to derive rudimentary rules for designing domain insertion variants that fold and traffic to the cell surface. Positional Kir2.1 responses to motif insertion clusters into distinct groups that correspond to contiguous structural regions of the channel with distinct biophysical properties tuned towards providing either folding stability or gating transitions. This suggests that insertional profiling is a high-throughput method to annotate function of ion channel structural regions.
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Affiliation(s)
- Willow Coyote-Maestas
- grid.17635.360000000419368657Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN 55455 USA
| | - David Nedrud
- grid.17635.360000000419368657Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN 55455 USA
| | - Antonio Suma
- grid.264727.20000 0001 2248 3398Department of Chemistry, Temple University, Philadelphia, PA 19122 USA
| | - Yungui He
- grid.17635.360000000419368657Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN 55455 USA
| | - Kenneth A. Matreyek
- grid.67105.350000 0001 2164 3847Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH 44106 USA
| | - Douglas M. Fowler
- grid.34477.330000000122986657Department of Genome Sciences, University of Washington, Seattle, WA 98115 USA ,grid.34477.330000000122986657Department of Bioengineering, University of Washington, Seattle, WA 98115 USA
| | - Vincenzo Carnevale
- grid.264727.20000 0001 2248 3398Department of Chemistry, Temple University, Philadelphia, PA 19122 USA
| | - Chad L. Myers
- grid.17635.360000000419368657Department of Computer Science and Engineering, University of Minnesota, Minneapolis, MN 55455 USA
| | - Daniel Schmidt
- Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, MN, 55455, USA.
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17
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Alfaro-Ruiz R, Martín-Belmonte A, Aguado C, Hernández F, Moreno-Martínez AE, Ávila J, Luján R. The Expression and Localisation of G-Protein-Coupled Inwardly Rectifying Potassium (GIRK) Channels Is Differentially Altered in the Hippocampus of Two Mouse Models of Alzheimer's Disease. Int J Mol Sci 2021; 22:ijms222011106. [PMID: 34681766 PMCID: PMC8541655 DOI: 10.3390/ijms222011106] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 10/11/2021] [Accepted: 10/12/2021] [Indexed: 12/31/2022] Open
Abstract
G protein-gated inwardly rectifying K+ (GIRK) channels are the main targets controlling excitability and synaptic plasticity on hippocampal neurons. Consequently, dysfunction of GIRK-mediated signalling has been implicated in the pathophysiology of Alzheimer´s disease (AD). Here, we provide a quantitative description on the expression and localisation patterns of GIRK2 in two transgenic mice models of AD (P301S and APP/PS1 mice), combining histoblots and immunoelectron microscopic approaches. The histoblot technique revealed differences in the expression of GIRK2 in the two transgenic mice models. The expression of GIRK2 was significantly reduced in the hippocampus of P301S mice in a laminar-specific manner at 10 months of age but was unaltered in APP/PS1 mice at 12 months compared to age-matched wild type mice. Ultrastructural approaches using the pre-embedding immunogold technique, demonstrated that the subcellular localisation of GIRK2 was significantly reduced along the neuronal surface of CA1 pyramidal cells, but increased in its frequency at cytoplasmic sites, in both P301S and APP/PS1 mice. We also found a decrease in plasma membrane GIRK2 channels in axon terminals contacting dendritic spines of CA1 pyramidal cells in P301S and APP/PS1 mice. These data demonstrate for the first time a redistribution of GIRK channels from the plasma membrane to intracellular sites in different compartments of CA1 pyramidal cells. Altogether, the pre- and post-synaptic reduction of GIRK2 channels suggest that GIRK-mediated alteration of the excitability in pyramidal cells could contribute to the cognitive dysfunctions as described in the two AD animal models.
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Affiliation(s)
- Rocío Alfaro-Ruiz
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain; (R.A.-R.); (A.M.-B.); (C.A.); (A.E.M.-M.)
| | - Alejandro Martín-Belmonte
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain; (R.A.-R.); (A.M.-B.); (C.A.); (A.E.M.-M.)
| | - Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain; (R.A.-R.); (A.M.-B.); (C.A.); (A.E.M.-M.)
| | - Félix Hernández
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas, ISCIII, 28049 Madrid, Spain; (F.H.); (J.Á.)
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, 28049 Madrid, Spain
| | - Ana Esther Moreno-Martínez
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain; (R.A.-R.); (A.M.-B.); (C.A.); (A.E.M.-M.)
| | - Jesús Ávila
- Centro de Investigación Biomédica en Red Sobre Enfermedades Neurodegenerativas, ISCIII, 28049 Madrid, Spain; (F.H.); (J.Á.)
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, 28049 Madrid, Spain
| | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02008 Albacete, Spain; (R.A.-R.); (A.M.-B.); (C.A.); (A.E.M.-M.)
- Correspondence: ; Tel.: +34-967-599200 (ext. 2196)
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18
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Abstract
K+ channels enable potassium to flow across the membrane with great selectivity. There are four K+ channel families: voltage-gated K (Kv), calcium-activated (KCa), inwardly rectifying K (Kir), and two-pore domain potassium (K2P) channels. All four K+ channels are formed by subunits assembling into a classic tetrameric (4x1P = 4P for the Kv, KCa, and Kir channels) or tetramer-like (2x2P = 4P for the K2P channels) architecture. These subunits can either be the same (homomers) or different (heteromers), conferring great diversity to these channels. They share a highly conserved selectivity filter within the pore but show different gating mechanisms adapted for their function. K+ channels play essential roles in controlling neuronal excitability by shaping action potentials, influencing the resting membrane potential, and responding to diverse physicochemical stimuli, such as a voltage change (Kv), intracellular calcium oscillations (KCa), cellular mediators (Kir), or temperature (K2P).
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19
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Therapeutic potential of targeting G protein-gated inwardly rectifying potassium (GIRK) channels in the central nervous system. Pharmacol Ther 2021; 223:107808. [PMID: 33476640 DOI: 10.1016/j.pharmthera.2021.107808] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Accepted: 01/05/2021] [Indexed: 12/15/2022]
Abstract
G protein-gated inwardly rectifying potassium channels (Kir3/GirK) are important for maintaining resting membrane potential, cell excitability and inhibitory neurotransmission. Coupled to numerous G protein-coupled receptors (GPCRs), they mediate the effects of many neurotransmitters, neuromodulators and hormones contributing to the general homeostasis and particular synaptic plasticity processes, learning, memory and pain signaling. A growing number of behavioral and genetic studies suggest a critical role for the appropriate functioning of the central nervous system, as well as their involvement in many neurologic and psychiatric conditions, such as neurodegenerative diseases, mood disorders, attention deficit hyperactivity disorder, schizophrenia, epilepsy, alcoholism and drug addiction. Hence, GirK channels emerge as a very promising tool to be targeted in the current scenario where these conditions already are or will become a global public health problem. This review examines recent findings on the physiology, function, dysfunction, and pharmacology of GirK channels in the central nervous system and highlights the relevance of GirK channels as a worthful potential target to improve therapies for related diseases.
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20
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Cui M, Alhamshari Y, Cantwell L, Ei-Haou S, Eptaminitaki GC, Chang M, Abou-Assali O, Tan H, Xu K, Masotti M, Plant LD, Thakur GA, Noujaim SF, Milnes J, Logothetis DE. A benzopyran with antiarrhythmic activity is an inhibitor of Kir3.1-containing potassium channels. J Biol Chem 2021; 296:100535. [PMID: 33713702 PMCID: PMC8086025 DOI: 10.1016/j.jbc.2021.100535] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 03/03/2021] [Accepted: 03/09/2021] [Indexed: 01/20/2023] Open
Abstract
Atrial fibrillation (AF) is the most commonly diagnosed cardiac arrhythmia and is associated with increased morbidity and mortality. Currently approved AF antiarrhythmic drugs have limited efficacy and/or carry the risk of ventricular proarrhythmia. The cardiac acetylcholine activated inwardly rectifying K+ current (IKACh), composed of Kir3.1/Kir3.4 heterotetrameric and Kir3.4 homotetrameric channel subunits, is one of the best validated atrial-specific ion channels. Previous research pointed to a series of benzopyran derivatives with potential for treatment of arrhythmias, but their mechanism of action was not defined. Here, we characterize one of these compounds termed Benzopyran-G1 (BP-G1) and report that it selectively inhibits the Kir3.1 (GIRK1 or G1) subunit of the KACh channel. Homology modeling, molecular docking, and molecular dynamics simulations predicted that BP-G1 inhibits the IKACh channel by blocking the central cavity pore. We identified the unique F137 residue of Kir3.1 as the critical determinant for the IKACh-selective response to BP-G1. The compound interacts with Kir3.1 residues E141 and D173 through hydrogen bonds that proved critical for its inhibitory activity. BP-G1 effectively blocked the IKACh channel response to carbachol in an in vivo rodent model and displayed good selectivity and pharmacokinetic properties. Thus, BP-G1 is a potent and selective small-molecule inhibitor targeting Kir3.1-containing channels and is a useful tool for investigating the role of Kir3.1 heteromeric channels in vivo. The mechanism reported here could provide the molecular basis for future discovery of novel, selective IKACh channel blockers to treat atrial fibrillation with minimal side effects.
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Affiliation(s)
- Meng Cui
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA.
| | - Yaser Alhamshari
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Lucas Cantwell
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Said Ei-Haou
- Department of Cardiac Biology, Xention Ltd, Cambridge, UK
| | - Giasemi C Eptaminitaki
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Mengmeng Chang
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Obada Abou-Assali
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - Haozhou Tan
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Keman Xu
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Meghan Masotti
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Leigh D Plant
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA; Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA
| | - Sami F Noujaim
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, USA
| | - James Milnes
- Department of Cardiac Biology, Xention Ltd, Cambridge, UK
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts, USA; Department of Chemistry and Chemical Biology, College of Science, Northeastern University, Boston, Massachusetts, USA; Center for Drug Discovery, Northeastern University, Boston, Massachusetts, USA.
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21
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Estadella I, Pedrós-Gámez O, Colomer-Molera M, Bosch M, Sorkin A, Felipe A. Endocytosis: A Turnover Mechanism Controlling Ion Channel Function. Cells 2020; 9:E1833. [PMID: 32759790 PMCID: PMC7463639 DOI: 10.3390/cells9081833] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/30/2020] [Accepted: 08/02/2020] [Indexed: 01/08/2023] Open
Abstract
Ion channels (IChs) are transmembrane proteins that selectively drive ions across membranes. The function of IChs partially relies on their abundance and proper location in the cell, fine-tuned by the delicate balance between secretory, endocytic, and degradative pathways. The disruption of this balance is associated with several diseases, such as Liddle's and long QT syndromes. Because of the vital role of these proteins in human health and disease, knowledge of ICh turnover is essential. Clathrin-dependent and -independent mechanisms have been the primary mechanisms identified with ICh endocytosis and degradation. Several molecular determinants recognized by the cellular internalization machinery have been discovered. Moreover, specific conditions can trigger the endocytosis of many IChs, such as the activation of certain receptors, hypokalemia, and some drugs. Ligand-dependent receptor activation primarily results in the posttranslational modification of IChs and the recruitment of important mediators, such as β-arrestins and ubiquitin ligases. However, endocytosis is not a final fate. Once internalized into endosomes, IChs are either sorted to lysosomes for degradation or recycled back to the plasma membrane. Rab proteins are crucial participants during these turnover steps. In this review, we describe the major ICh endocytic pathways, the signaling inputs triggering ICh internalization, and the key mediators of this essential cellular process.
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Affiliation(s)
- Irene Estadella
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Oriol Pedrós-Gámez
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Magalí Colomer-Molera
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
| | - Manel Bosch
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
- Centres Científics i Tecnològics de la Universitat de Barcelona (CCiTUB), Universitat de Barcelona, 08028 Barcelona, Spain
| | - Alexander Sorkin
- Department of Cell Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA;
| | - Antonio Felipe
- Molecular Physiology Laboratory, Departament de Bioquímica i Biomedicina Molecular, Institut de Biomedicina (IBUB), Universitat de Barcelona, 08028 Barcelona, Spain; (I.E.); (O.P.-G.); (M.C.-M.); (M.B.)
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22
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Lyu C, Lyu GW, Mulder J, Martinez A, Shi TJS. G Protein-Gated Inwardly Rectifying Potassium Channel Subunit 3 is Upregulated in Rat DRGs and Spinal Cord After Peripheral Nerve Injury. J Pain Res 2020; 13:419-429. [PMID: 32110090 PMCID: PMC7034995 DOI: 10.2147/jpr.s233744] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 01/28/2020] [Indexed: 12/15/2022] Open
Abstract
Background G protein-gated inwardly rectifying potassium (GIRK) channels are involved in the regulation of neuronal excitability. Four GIRK subunits (GIRK1-4) are expressed in rat dorsal root ganglia (DRGs). Recently, we have characterized the expression of GIRK1 and −2, and both are downregulated in rat DRGs and spinal cord after a complete sciatic nerve transection (axotomy). Here, we aimed to study the neurochemical characteristics of GIRK3, and its regulation in rat DRGs and spinal cord induced by nerve injury. Methods A sciatic nerve axotomy was performed to study the influences of injury on GIRK3 expression in DRGs and spinal cord. A dorsal root rhizotomy and a sciatic nerve crush were employed to study the axonal transport of GIRK3 protein, respectively. Immunohistochemistry analysis was employed for investigating the neurochemical characteristics of GIRK3. Results In control DRGs, ~18% of neuron profiles (NPs) were GIRK3-positive (+), and ~41%, ~48% and ~45% of GIRK3+ NPs were CGRP+, IB4+ and NF200+, respectively. GIRK3-like immunoreactivity was observed in glabrous skin of hind paws and axons originating from DRG neurons. Fourteen days after axotomy, more than one-third of DRG NPs were GIRK3+, and among these ~51% and ~56% coexpressed galanin and neuropeptide Y, respectively. In control animals, a small group of interneurons found in the dorsal horn was GIRK3+. In addition, GIRK3+ processes could be observed in superficial laminae of spinal dorsal horn. After nerve injury, the intensity of GIRK3-like immunoreactivity in the superficial layers was increased. Evidence based on rhizotomy and sciatic nerve crush indicated both anterograde and retrograde transport of GIRK3. Conclusion Our study demonstrates that GIRK3 is expressed in sensory neurons and spinal cord. GIRK3 has both anterograde and retrograde axonal transport. GIRK3 expression can be regulated by peripheral nerve injury.
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Affiliation(s)
- Chuang Lyu
- State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, Harbin 150069, People's Republic of China
| | - Gong-Wei Lyu
- Department of Neurology, 1st Hospital of Harbin Medical University, Harbin 150001, People's Republic of China
| | - Jan Mulder
- Department of Neuroscience, Karolinska Institutet, Stockholm SE-171 77, Sweden.,Science for Life Laboratory, Karolinska Institutet, Stockholm SE-171 65, Sweden
| | - Aurora Martinez
- Department of Biomedicine, University of Bergen, Bergen 5009, Norway
| | - Tie-Jun Sten Shi
- Department of Biomedicine, University of Bergen, Bergen 5009, Norway
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23
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Xu Y, Cantwell L, Molosh AI, Plant LD, Gazgalis D, Fitz SD, Dustrude ET, Yang Y, Kawano T, Garai S, Noujaim SF, Shekhar A, Logothetis DE, Thakur GA. The small molecule GAT1508 activates brain-specific GIRK1/2 channel heteromers and facilitates conditioned fear extinction in rodents. J Biol Chem 2020; 295:3614-3634. [PMID: 31953327 DOI: 10.1074/jbc.ra119.011527] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 01/09/2020] [Indexed: 01/31/2023] Open
Abstract
G-protein-gated inwardly-rectifying K+ (GIRK) channels are targets of Gi/o-protein-signaling systems that inhibit cell excitability. GIRK channels exist as homotetramers (GIRK2 and GIRK4) or heterotetramers with nonfunctional homomeric subunits (GIRK1 and GIRK3). Although they have been implicated in multiple conditions, the lack of selective GIRK drugs that discriminate among the different GIRK channel subtypes has hampered investigations into their precise physiological relevance and therapeutic potential. Here, we report on a highly-specific, potent, and efficacious activator of brain GIRK1/2 channels. Using a chemical screen and electrophysiological assays, we found that this activator, the bromothiophene-substituted small molecule GAT1508, is specific for brain-expressed GIRK1/2 channels rather than for cardiac GIRK1/4 channels. Computational models predicted a GAT1508-binding site validated by experimental mutagenesis experiments, providing insights into how urea-based compounds engage distant GIRK1 residues required for channel activation. Furthermore, we provide computational and experimental evidence that GAT1508 is an allosteric modulator of channel-phosphatidylinositol 4,5-bisphosphate interactions. Through brain-slice electrophysiology, we show that subthreshold GAT1508 concentrations directly stimulate GIRK currents in the basolateral amygdala (BLA) and potentiate baclofen-induced currents. Of note, GAT1508 effectively extinguished conditioned fear in rodents and lacked cardiac and behavioral side effects, suggesting its potential for use in pharmacotherapy for post-traumatic stress disorder. In summary, our findings indicate that the small molecule GAT1508 has high specificity for brain GIRK1/2 channel subunits, directly or allosterically activates GIRK1/2 channels in the BLA, and facilitates fear extinction in a rodent model.
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Affiliation(s)
- Yu Xu
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Lucas Cantwell
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Andrei I Molosh
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Leigh D Plant
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Dimitris Gazgalis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Stephanie D Fitz
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Erik T Dustrude
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Yuchen Yang
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Takeharu Kawano
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Sumanta Garai
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115
| | - Sami F Noujaim
- Molecular Pharmacology and Physiology, University of South Florida, Tampa, Florida 33612
| | - Anantha Shekhar
- Department of Psychiatry, Paul and Carole Stark Neurosciences Research Institute, Indiana Clinical and Translational Sciences Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202.
| | - Diomedes E Logothetis
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115.
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences, and Center for Drug Discovery, Northeastern University, Boston, Massachusetts 02115.
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24
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Zangerl-Plessl EM, Qile M, Bloothooft M, Stary-Weinzinger A, van der Heyden MAG. Disease Associated Mutations in K IR Proteins Linked to Aberrant Inward Rectifier Channel Trafficking. Biomolecules 2019; 9:biom9110650. [PMID: 31731488 PMCID: PMC6920955 DOI: 10.3390/biom9110650] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/22/2019] [Accepted: 10/23/2019] [Indexed: 12/28/2022] Open
Abstract
The ubiquitously expressed family of inward rectifier potassium (KIR) channels, encoded by KCNJ genes, is primarily involved in cell excitability and potassium homeostasis. Channel mutations associate with a variety of severe human diseases and syndromes, affecting many organ systems including the central and peripheral neural system, heart, kidney, pancreas, and skeletal muscle. A number of mutations associate with altered ion channel expression at the plasma membrane, which might result from defective channel trafficking. Trafficking involves cellular processes that transport ion channels to and from their place of function. By alignment of all KIR channels, and depicting the trafficking associated mutations, three mutational hotspots were identified. One localized in the transmembrane-domain 1 and immediately adjacent sequences, one was found in the G-loop and Golgi-export domain, and the third one was detected at the immunoglobulin-like domain. Surprisingly, only few mutations were observed in experimentally determined Endoplasmic Reticulum (ER)exit-, export-, or ER-retention motifs. Structural mapping of the trafficking defect causing mutations provided a 3D framework, which indicates that trafficking deficient mutations form clusters. These “mutation clusters” affect trafficking by different mechanisms, including protein stability.
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Affiliation(s)
- Eva-Maria Zangerl-Plessl
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Muge Qile
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Meye Bloothooft
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
| | - Anna Stary-Weinzinger
- Department of Pharmacology and Toxicology, University of Vienna, 1090 Vienna, Austria; (E.-M.Z.-P.); (A.S.-W.)
| | - Marcel A. G. van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, 3584 CM Utrecht, The Netherlands; (M.Q.); (M.B.)
- Correspondence: ; Tel.: +31-887558901
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25
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Abney KK, Bubser M, Du Y, Kozek KA, Bridges TM, Lindsley CW, Daniels JS, Morrison RD, Wickman K, Hopkins CR, Jones CK, Weaver CD. Analgesic Effects of the GIRK Activator, VU0466551, Alone and in Combination with Morphine in Acute and Persistent Pain Models. ACS Chem Neurosci 2019; 10:1294-1299. [PMID: 30474955 DOI: 10.1021/acschemneuro.8b00370] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels are potassium-selective ion channels. As their name suggests, GIRK channels are effectors of Gi/o G protein-couple receptors whereby activation of these GPCRs leads to increased GIRK channel activity resulting in decreased cellular excitability. In this way, GIRK channels play diverse roles in physiology as effectors of Gi/o-coupled GPCRs: peacemaking in the heart rate, modulation of hormone secretion in endocrine tissues, as well as numerous CNS functions including learning, memory, and addiction/reward. Notably, GIRK channels are widely expressed along the spinothalamic tract and are positioned to play roles in both ascending and descending pain pathways. More notably, GIRK channel knockout and knock-down studies have found that GIRK channels play a major role in the action of opioid analgesics which act predominantly through Gi/o-coupled, opioid-activated GPCRs (e.g., μ-opioid receptors). Recent advances in GIRK channel pharmacology have led to the development of small molecules that directly and selectively activate GIRK channels. Based on research implicating the involvement of GIRK channels in pain pathways and as effectors of opioid analgesics, we conducted a study to determine whether direct pharmacological activation of GIRK channels could produce analgesic efficacy and/or augment the analgesic efficacy morphine, an opioid receptor agonist capable of activating μ-opioid receptors as well as other opioid receptor subtypes. In the present study, we demonstrate that the small-molecule GIRK activator, VU0466551, has analgesic effects when dosed alone or in combination with submaximally effective doses of morphine.
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Affiliation(s)
- Kristopher K. Abney
- School of Graduate Studies and Research, Meharry Medical College, Nashville, Tennessee 37208, United States
| | - Michael Bubser
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, Tennessee 37232, United States
| | - Yu Du
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Krystian A. Kozek
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
| | - Thomas M. Bridges
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, Tennessee 37232, United States
| | - Craig W. Lindsley
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, Tennessee 37232, United States
| | | | | | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Corey R. Hopkins
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Carrie K. Jones
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Vanderbilt Center for Neuroscience Drug Discovery, Nashville, Tennessee 37232, United States
| | - C. David Weaver
- Vanderbilt Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, United States
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee 37232, United States
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26
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GIRK Channel Activity in Dopamine Neurons of the Ventral Tegmental Area Bidirectionally Regulates Behavioral Sensitivity to Cocaine. J Neurosci 2019; 39:3600-3610. [PMID: 30837265 DOI: 10.1523/jneurosci.3101-18.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 02/17/2019] [Accepted: 02/22/2019] [Indexed: 12/19/2022] Open
Abstract
Dopamine (DA) neurons of the VTA have been widely implicated in the cellular and behavioral responses to drugs of abuse. Inhibitory G protein signaling mediated by GABAB receptors (GABABRs) and D2 DA receptors (D2Rs) regulates the excitability of VTA DA neurons, DA neurotransmission, and behaviors modulated by DA. Most of the somatodendritic inhibitory effect of GABABR and D2R activation on DA neurons reflects the activation of G protein-gated inwardly rectifying K+ (GIRK) channels. Furthermore, GIRK-dependent signaling in VTA DA neurons can be weakened by exposure to psychostimulants and strengthened by phasic DA neuron firing. The objective of this study was to determine how the strength of GIRK channel activity in VTA DA neurons influences sensitivity to cocaine. We used a Cre-dependent viral strategy to overexpress the individual GIRK channel subunits in VTA DA neurons of male and female adult mice, leading to enhancement (GIRK2) or suppression (GIRK3) of GIRK channel activity. Overexpression of GIRK3 decreased somatodendritic GABABR- and D2R-dependent signaling and increased cocaine-induced locomotor activity, whereas overexpression of GIRK2 increased GABABR-dependent signaling and decreased cocaine-induced locomotion. Neither manipulation impacted anxiety- or depression-related behavior, despite the link between such behaviors and DA signaling. Together, these data show that behavioral sensitivity to cocaine in mice is inversely proportional to the strength of GIRK channel activity in VTA DA neurons and suggest that direct activators of the unique VTA DA neuron GIRK channel subtype (GIRK2/GIRK3 heteromer) could represent a promising therapeutic target for treatment of addiction.SIGNIFICANCE STATEMENT Inhibitory G protein signaling in dopamine (DA) neurons, including that mediated by G protein-gated inwardly rectifying K+ (GIRK) channels, has been implicated in behavioral sensitivity to cocaine. Here, we used a viral approach to bidirectionally manipulate GIRK channel activity in DA neurons of the VTA. We found that decreasing GIRK channel activity in VTA DA neurons increased behavioral sensitivity to cocaine, whereas increasing GIRK channel activity decreased behavioral sensitivity to cocaine. These manipulations did not alter anxiety- or depression-related behaviors. These data highlight the unique GIRK channel subtype in VTA DA neurons as a possible therapeutic target for addiction.
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27
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Kozek KA, Du Y, Sharma S, Prael FJ, Spitznagel BD, Kharade SV, Denton JS, Hopkins CR, Weaver CD. Discovery and Characterization of VU0529331, a Synthetic Small-Molecule Activator of Homomeric G Protein-Gated, Inwardly Rectifying, Potassium (GIRK) Channels. ACS Chem Neurosci 2019; 10:358-370. [PMID: 30136838 PMCID: PMC6528656 DOI: 10.1021/acschemneuro.8b00287] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
G protein-gated, inwardly rectifying, potassium (GIRK) channels are important regulators of cellular excitability throughout the body. GIRK channels are heterotetrameric and homotetrameric combinations of the Kir3.1-4 (GIRK1-4) subunits. Different subunit combinations are expressed throughout the central nervous system (CNS) and the periphery, and most of these combinations contain a GIRK1 subunit. For example, the predominance of GIRK channels in the CNS are composed of GIRK1 and GIRK2 subunits, while the GIRK channels in cardiac atrial myocytes are made up mostly of GIRK1 and GIRK4 subunits. Although the vast majority of GIRK channels contain a GIRK1 subunit, discrete populations of cells that express non-GIRK1-containing GIRK (non-GIRK1/X) channels do exist. For instance, dopaminergic neurons in the ventral tegmental area of the brain, associated with addiction and reward, do not express the GIRK1 subunit. Targeting these non-GIRK1/X channels with subunit-selective pharmacological probes could lead to important insights into how GIRK channels are involved in reward and addiction. Such insights may, in turn, reveal therapeutic opportunities for the treatment or prevention of addiction. Previously, our laboratory discovered small molecules that can specifically modulate the activity of GIRK1-containing GIRK channels. However, efforts to generate compounds active on non-GIRK1/X channels from these scaffolds have been unsuccessful. Recently, ivermectin was shown to modulate non-GIRK1/X channels, and historically, ivermectin is known to modulate a wide variety of neuronal channels and receptors. Further, ivermectin is a complex natural product, which makes it a challenging starting point for development of more selective, effective, and potent compounds. Thus, while ivermectin provides proof-of-concept as a non-GIRK1/X channel activator, it is of limited utility. Therefore, we sought to discover a synthetic small molecule that would serve as a starting point for the development of non-GIRK1/X channel modulators. To accomplish this, we used a high-throughput thallium flux assay to screen a 100 000-compound library in search of activators of homomeric GIRK2 channels. Using this approach, we discovered VU0529331, the first synthetic small molecule reported to activate non-GIRK1/X channels, to our knowledge. This discovery represents the first step toward developing potent and selective non-GIRK1/X channel probes. Such molecules will help elucidate the role of GIRK channels in addiction, potentially establishing a foundation for future development of therapies utilizing targeted GIRK channel modulation.
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Affiliation(s)
- Krystian A. Kozek
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Medical Scientist Training Program, Vanderbilt University, Nashville, Tennessee, USA
| | - Yu Du
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Swagat Sharma
- Department of Pharmaceutical Sciences, Center for Drug Discovery, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Francis J. Prael
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Brittany D. Spitznagel
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Sujay V. Kharade
- Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee, USA
| | - Jerod S. Denton
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Anesthesiology, Vanderbilt University, Nashville, Tennessee, USA
| | - Corey R. Hopkins
- Department of Pharmaceutical Sciences, Center for Drug Discovery, College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - C. David Weaver
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
- vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, USA
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28
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GIRK currents in VTA dopamine neurons control the sensitivity of mice to cocaine-induced locomotor sensitization. Proc Natl Acad Sci U S A 2018; 115:E9479-E9488. [PMID: 30228121 PMCID: PMC6176583 DOI: 10.1073/pnas.1807788115] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
GABABR-dependent activation of G protein-gated inwardly rectifying potassium channels (GIRK or KIR3) provides a well-known source of inhibition in the brain, but the details on how this important inhibitory pathway affects neural circuits are lacking. We used sorting nexin 27 (SNX27), an endosomal adaptor protein that associates with GIRK2c and GIRK3 subunits, to probe the role of GIRK channels in reward circuits. A conditional knockout of SNX27 in both substantia nigra pars compacta and ventral tegmental area (VTA) dopamine neurons leads to markedly smaller GABABR- and dopamine D2R-activated GIRK currents, as well as to suprasensitivity to cocaine-induced locomotor sensitization. Expression of the SNX27-insensitive GIRK2a subunit in SNX27-deficient VTA dopamine neurons restored GIRK currents and GABABR-dependent inhibition of spike firing, while also resetting the mouse's sensitivity to cocaine-dependent sensitization. These results establish a link between slow inhibition mediated by GIRK channels in VTA dopamine neurons and cocaine addiction, revealing a therapeutic target for treating addiction.
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29
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Kulik Á, Booker SA, Vida I. Differential distribution and function of GABABRs in somato-dendritic and axonal compartments of principal cells and interneurons in cortical circuits. Neuropharmacology 2018; 136:80-91. [DOI: 10.1016/j.neuropharm.2017.10.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/12/2017] [Accepted: 10/13/2017] [Indexed: 12/24/2022]
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30
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Kurokawa T, Kiyonaka S, Nakata E, Endo M, Koyama S, Mori E, Tran NH, Dinh H, Suzuki Y, Hidaka K, Kawata M, Sato C, Sugiyama H, Morii T, Mori Y. DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K +
Channels. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201709982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tatsuki Kurokawa
- Department of Synthetic Chemistry and Biological Chemistry; Graduate School of Engineering; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
| | - Shigeki Kiyonaka
- Department of Synthetic Chemistry and Biological Chemistry; Graduate School of Engineering; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Department of Technology and Ecology, Hall of Global Environmental Studies; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
| | - Eiji Nakata
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Institute of Advanced Energy; Kyoto University, Gokasho, Uji; Kyoto 611-0011 Japan
| | - Masayuki Endo
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS); Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku; Kyoto 606-8501 Japan
| | - Shohei Koyama
- Department of Synthetic Chemistry and Biological Chemistry; Graduate School of Engineering; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
| | - Emiko Mori
- Department of Synthetic Chemistry and Biological Chemistry; Graduate School of Engineering; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
| | - Nam Ha Tran
- Department of Technology and Ecology, Hall of Global Environmental Studies; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
| | - Huyen Dinh
- Institute of Advanced Energy; Kyoto University, Gokasho, Uji; Kyoto 611-0011 Japan
| | - Yuki Suzuki
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Department of Chemistry; Graduate School of Science; Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku; Kyoto 606-8502 Japan
| | - Kumi Hidaka
- Department of Chemistry; Graduate School of Science; Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku; Kyoto 606-8502 Japan
| | - Masaaki Kawata
- Biomedical Research Institute; National Institute of Advanced Industrial Science and Technology; 1-1-1 Higashi, Tsukuba Ibaraki 305-8566 Japan
| | - Chikara Sato
- Biomedical Research Institute; National Institute of Advanced Industrial Science and Technology; 1-1-1 Higashi, Tsukuba Ibaraki 305-8566 Japan
| | - Hiroshi Sugiyama
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS); Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku; Kyoto 606-8501 Japan
- Department of Chemistry; Graduate School of Science; Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku; Kyoto 606-8502 Japan
| | - Takashi Morii
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Institute of Advanced Energy; Kyoto University, Gokasho, Uji; Kyoto 611-0011 Japan
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry; Graduate School of Engineering; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
- Core Research for Evolutional Science and Technology (Japan); Science and Technology Agency; 4-1-8 Hon-cho, Kawaguchi Saitama 332-0012 Japan
- Department of Technology and Ecology, Hall of Global Environmental Studies; Kyoto University, Kyotodaigakukatsura, Nishikyo-ku; Kyoto 615-8510 Japan
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS); Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku; Kyoto 606-8501 Japan
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31
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Kurokawa T, Kiyonaka S, Nakata E, Endo M, Koyama S, Mori E, Tran NH, Dinh H, Suzuki Y, Hidaka K, Kawata M, Sato C, Sugiyama H, Morii T, Mori Y. DNA Origami Scaffolds as Templates for Functional Tetrameric Kir3 K + Channels. Angew Chem Int Ed Engl 2018; 57:2586-2591. [PMID: 29341462 DOI: 10.1002/anie.201709982] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/15/2017] [Indexed: 01/17/2023]
Abstract
In native systems, scaffolding proteins play important roles in assembling proteins into complexes to transduce signals. This concept is yet to be applied to the assembly of functional transmembrane protein complexes in artificial systems. To address this issue, DNA origami has the potential to serve as scaffolds that arrange proteins at specific positions in complexes. Herein, we report that Kir3 K+ channel proteins are assembled through zinc-finger protein (ZFP)-adaptors at specific locations on DNA origami scaffolds. Specific binding of the ZFP-fused Kir3 channels and ZFP-based adaptors on DNA origami were confirmed by atomic force microscopy and gel electrophoresis. Furthermore, the DNA origami with ZFP binding sites nearly tripled the K+ channel current activity elicited by heterotetrameric Kir3 channels in HEK293T cells. Thus, our method provides a useful template to control the oligomerization states of membrane protein complexes in vitro and in living cells.
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Affiliation(s)
- Tatsuki Kurokawa
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan
| | - Shigeki Kiyonaka
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Department of Technology and Ecology, Hall of Global Environmental Studies, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Eiji Nakata
- Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Masayuki Endo
- Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Shohei Koyama
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Emiko Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan
| | - Nam Ha Tran
- Department of Technology and Ecology, Hall of Global Environmental Studies, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Huyen Dinh
- Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Yuki Suzuki
- Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Kumi Hidaka
- Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Masaaki Kawata
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Chikara Sato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566, Japan
| | - Hiroshi Sugiyama
- Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan.,Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Takashi Morii
- Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
| | - Yasuo Mori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Core Research for Evolutional Science and Technology (Japan), Science and Technology Agency, 4-1-8 Hon-cho, Kawaguchi, Saitama, 332-0012, Japan.,Department of Technology and Ecology, Hall of Global Environmental Studies, Kyoto University, Kyotodaigakukatsura, Nishikyo-ku, Kyoto, 615-8510, Japan.,Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Ushinomiya-cho, Sakyo-ku, Kyoto, 606-8501, Japan
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Expression and relevance of the G protein-gated K + channel in the mouse ventricle. Sci Rep 2018; 8:1192. [PMID: 29352184 PMCID: PMC5775354 DOI: 10.1038/s41598-018-19719-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 01/08/2018] [Indexed: 12/31/2022] Open
Abstract
The atrial G protein-gated inwardly rectifying K+ (GIRK) channel is a critical mediator of parasympathetic influence on cardiac physiology. Here, we probed the details and relevance of the GIRK channel in mouse ventricle. mRNAs for the atrial GIRK channel subunits (GIRK1, GIRK4), M2 muscarinic receptor (M2R), and RGS6, a negative regulator of atrial GIRK-dependent signaling, were detected in mouse ventricle at relatively low levels. The cholinergic agonist carbachol (CCh) activated small GIRK currents in adult wild-type ventricular myocytes that exhibited relatively slow kinetics and low CCh sensitivity; these currents were absent in ventricular myocytes from Girk1-/- or Girk4-/- mice. While loss of GIRK channels attenuated the CCh-induced shortening of action potential duration and suppression of ventricular myocyte excitability, selective ablation of GIRK channels in ventricle had no effect on heart rate, heart rate variability, or electrocardiogram parameters at baseline or after CCh injection. Additionally, loss of ventricular GIRK channels did not impact susceptibility to ventricular arrhythmias. These data suggest that the mouse ventricular GIRK channel is a GIRK1/GIRK4 heteromer, and show that while it contributes to the cholinergic suppression of ventricular myocyte excitability, this influence does not substantially impact cardiac physiology or ventricular arrhythmogenesis in the mouse.
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Prolonged seizure activity causes caspase dependent cleavage and dysfunction of G-protein activated inwardly rectifying potassium channels. Sci Rep 2017; 7:12313. [PMID: 28951616 PMCID: PMC5615076 DOI: 10.1038/s41598-017-12508-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 09/08/2017] [Indexed: 01/09/2023] Open
Abstract
Recurrent high-frequency epileptic seizures cause progressive hippocampal sclerosis, which is associated with caspase-3 activation and NMDA receptor-dependent excitotoxicity. However, the identity of caspase-3 substrates that contribute to seizure-induced hippocampal atrophy remains largely unknown. Here, we show that prolonged high-frequency epileptiform discharges in cultured hippocampal neurons leads to caspase-dependent cleavage of GIRK1 and GIRK2, the major subunits of neuronal G protein-activated inwardly rectifying potassium (GIRK) channels that mediate membrane hyperpolarization and synaptic inhibition in the brain. We have identified caspase-3 cleavage sites in GIRK1 (387ECLD390) and GIRK2 (349YEVD352). The YEVD motif is highly conserved in GIRK2-4, and located within their C-terminal binding sites for Gβγ proteins that mediate membrane-delimited GIRK activation. Indeed, the cleaved GIRK2 displays reduced binding to Gβγ and cannot coassemble with GIRK1. Loss of an ER export motif upon cleavage of GIRK2 abolishes surface and current expression of GIRK2 homotetramic channels. Lastly, kainate-induced status epilepticus causes GIRK1 and GIRK2 cleavage in the hippocampus in vivo. Our findings are the first to show direct cleavage of GIRK1 and GIRK2 subunits by caspase-3, and suggest the possible role of caspase-3 mediated down-regulation of GIRK channel function and expression in hippocampal neuronal injury during prolonged epileptic seizures.
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Marron Fernandez de Velasco E, Zhang L, N Vo B, Tipps M, Farris S, Xia Z, Anderson A, Carlblom N, Weaver CD, Dudek SM, Wickman K. GIRK2 splice variants and neuronal G protein-gated K + channels: implications for channel function and behavior. Sci Rep 2017; 7:1639. [PMID: 28487514 PMCID: PMC5431628 DOI: 10.1038/s41598-017-01820-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 04/03/2017] [Indexed: 11/21/2022] Open
Abstract
Many neurotransmitters directly inhibit neurons by activating G protein-gated inwardly rectifying K+ (GIRK) channels, thereby moderating the influence of excitatory input on neuronal excitability. While most neuronal GIRK channels are formed by GIRK1 and GIRK2 subunits, distinct GIRK2 isoforms generated by alternative splicing have been identified. Here, we compared the trafficking and function of two isoforms (GIRK2a and GIRK2c) expressed individually in hippocampal pyramidal neurons lacking GIRK2. GIRK2a and GIRK2c supported comparable somato-dendritic GIRK currents in Girk2 -/- pyramidal neurons, although GIRK2c achieved a more uniform subcellular distribution in pyramidal neurons and supported inhibitory postsynaptic currents in distal dendrites better than GIRK2a. While over-expression of either isoform in dorsal CA1 pyramidal neurons restored contextual fear learning in a conditional Girk2 -/- mouse line, GIRK2a also enhanced cue fear learning. Collectively, these data indicate that GIRK2 isoform balance within a neuron can impact the processing of afferent inhibitory input and associated behavior.
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Affiliation(s)
| | - Lei Zhang
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - Baovi N Vo
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - Megan Tipps
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - Shannon Farris
- National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Zhilian Xia
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - Allison Anderson
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - Nicholas Carlblom
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA
| | - C David Weaver
- Vanderbilt University, Department of Pharmacology, Nashville, TN, 37235, USA
| | - Serena M Dudek
- National Institute of Environmental Health Sciences, Research Triangle Park, NC, 27709, USA
| | - Kevin Wickman
- University of Minnesota, Department of Pharmacology, Minneapolis, MN, 55455, USA.
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Rifkin RA, Moss SJ, Slesinger PA. G Protein-Gated Potassium Channels: A Link to Drug Addiction. Trends Pharmacol Sci 2017; 38:378-392. [PMID: 28188005 DOI: 10.1016/j.tips.2017.01.007] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/08/2017] [Accepted: 01/10/2017] [Indexed: 11/29/2022]
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels are regulators of neuronal excitability in the brain. Knockout mice lacking GIRK channels display altered behavioral responses to multiple addictive drugs, implicating GIRK channels in addictive behaviors. Here, we review the effects of GIRK subunit deletions on the behavioral response to psychostimulants, such as cocaine and methamphetamine. Additionally, exposure of mice to psychostimulants produces alterations in the surface expression of GIRK channels in multiple types of neurons within the reward system of the brain. Thus, we compare the subcellular mechanisms by which drug exposure appears to alter GIRK expression in multiple cell types and provide an outlook on future studies examining the role of GIRK channels in addiction. A greater understanding of how GIRK channels are regulated by addictive drugs may enable the development of therapies to prevent or treat drug abuse.
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Affiliation(s)
- Robert A Rifkin
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Medical Scientist Training Program, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA
| | - Stephen J Moss
- Dept of Neuroscience, Tufts University School of Medicine, Boston, MA 02155, USA; Dept of Neuroscience, Physiology and Pharmacology, University College London, London, WC1E 6BT, UK
| | - Paul A Slesinger
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA.
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Acid-Sensing Ion Channel 2a (ASIC2a) Promotes Surface Trafficking of ASIC2b via Heteromeric Assembly. Sci Rep 2016; 6:30684. [PMID: 27477936 PMCID: PMC4967927 DOI: 10.1038/srep30684] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 07/08/2016] [Indexed: 12/27/2022] Open
Abstract
Acid-sensing ion channels (ASICs) are proton-activated cation channels that play important roles as typical proton sensors during pathophysiological conditions and normal synaptic activities. Among the ASIC subunits, ASIC2a and ASIC2b are alternative splicing products from the same gene, ACCN1. It has been shown that ASIC2 isoforms have differential subcellular distribution: ASIC2a targets the cell surface by itself, while ASIC2b resides in the ER. However, the underlying mechanism for this differential subcellular localization remained to be further elucidated. By constructing ASIC2 chimeras, we found that the first transmembrane (TM1) domain and the proximal post-TM1 domain (17 amino acids) of ASIC2a are critical for membrane targeting of the proteins. We also observed that replacement of corresponding residues in ASIC2b by those of ASIC2a conferred proton-sensitivity as well as surface expression to ASIC2b. We finally confirmed that ASIC2b is delivered to the cell surface from the ER by forming heteromers with ASIC2a, and that the N-terminal region of ASIC2a is additionally required for the ASIC2a-dependent membrane targeting of ASIC2b. Together, our study supports an important role of ASIC2a in membrane targeting of ASIC2b.
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37
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A Role for the GIRK3 Subunit in Methamphetamine-Induced Attenuation of GABAB Receptor-Activated GIRK Currents in VTA Dopamine Neurons. J Neurosci 2016; 36:3106-14. [PMID: 26985023 DOI: 10.1523/jneurosci.1327-15.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Repeated exposure to psychostimulants induces locomotor sensitization and leads to persistent changes in the circuitry of the mesocorticolimbic dopamine (DA) system. G-protein-gated inwardly rectifying potassium (GIRK; also known as Kir3) channels mediate a slow IPSC and control the excitability of DA neurons. Repeated 5 d exposure to psychostimulants decreases the size of the GABAB receptor (GABABR)-activated GIRK currents (IBaclofen) in ventral tegmental area (VTA) DA neurons of mice, but the mechanism underlying this plasticity is poorly understood. Here, we show that methamphetamine-dependent attenuation of GABABR-GIRK currents in VTA DA neurons required activation of both D1R-like and D2R-like receptors. The methamphetamine-dependent decrease in GABABR-GIRK currents in VTA DA neurons did not depend on a mechanism of dephosphorylation of the GABAB R2 subunit found previously for other neurons in the reward pathway. Rather, the presence of the GIRK3 subunit appeared critical for the methamphetamine-dependent decrease of GABABR-GIRK current in VTA DA neurons. Together, these results highlight different regulatory mechanisms in the learning-evoked changes that occur in the VTA with repeated exposure to psychostimulants. SIGNIFICANCE STATEMENT Exposure to addictive drugs such as psychostimulants produces persistent adaptations in inhibitory circuits within the mesolimbic dopamine system, suggesting that addictive behaviors are encoded by changes in the reward neural circuitry. One form of neuroadaptation that occurs with repeated exposure to psychostimulants is a decrease in slow inhibition, mediated by a GABAB receptor and a potassium channel. Here, we examine the subcellular mechanism that links psychostimulant exposure with changes in slow inhibition and reveal that one type of potassium channel subunit is important for mediating the effect of repeated psychostimulant exposure. Dissecting out the components of drug-dependent plasticity and uncovering novel protein targets in the reward circuit may lead to the development of new therapeutics for treating addiction.
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Robertson DN, Sleno R, Nagi K, Pétrin D, Hébert TE, Pineyro G. Design and construction of conformational biosensors to monitor ion channel activation: A prototype FlAsH/BRET-approach to Kir3 channels. Methods 2016. [DOI: 10.1016/j.ymeth.2015.07.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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TRP and Rhodopsin Transport Depends on Dual XPORT ER Chaperones Encoded by an Operon. Cell Rep 2015; 13:573-584. [PMID: 26456832 DOI: 10.1016/j.celrep.2015.09.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 07/30/2015] [Accepted: 09/04/2015] [Indexed: 11/24/2022] Open
Abstract
TRP channels and G protein-coupled receptors (GPCRs) play critical roles in sensory reception. However, the identities of the chaperones that assist GPCRs in translocating from the endoplasmic reticulum (ER) are limited, and TRP ER chaperones are virtually unknown. The one exception for TRPs is Drosophila XPORT. Here, we show that the xport locus is bicistronic and encodes unrelated transmembrane proteins, which enable the signaling proteins that initiate and culminate phototransduction, rhodopsin 1 (Rh1) and TRP, to traffic to the plasma membrane. XPORT-A and XPORT-B are ER proteins, and loss of either has a profound impact on TRP and Rh1 targeting to the light-sensing compartment of photoreceptor cells. XPORT-B complexed in vivo with the Drosophila homolog of the mammalian HSP70 protein, GRP78/BiP, which, in turn, associated with Rh1. Our work highlights a coordinated network of chaperones required for the biosynthesis of the TRP channel and rhodopsin in Drosophila photoreceptor cells.
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Abstract
Genetic studies have linked alterations in Kir7.1 channel to diverse pathologies. We summarize functional relevance of Kir7.1 channel in retinal pigment epithelium (RPE), regulation of channel function by various cytoplasmic metabolites, and mutations that cause channelopathies. At the apical membrane of RPE, K(+) channels contribute to subretinal K(+) homeostasis and support Na(+)/K(+) pump and Na(+)-K(+)-2Cl(-) cotransporter function by providing a pathway for K(+) secretion. Electrophysiological studies have established that barium- and cesium-sensitive inwardly rectifying K(+) (Kir) channels make up a major component of the RPE apical membrane K(+) conductance. Native human RPE expresses transcripts for Kir1.1, Kir2.1, Kir2.2, Kir3.1, Kir3.4, Kir4.2, and Kir6.1, albeit at levels at least 50-fold lower than Kir7.1. Kir7.1 is structurally similar to other Kir channels, consisting of 2 trans-membrane domains, a pore-forming loop that contains the selectivity filter, and 2 cytoplasmic polar tails. Within the cytoplasmic structure, clusters of amino acid sequences form regulatory domains that interact with cellular metabolites and control the opening and closing of the channel. Recent evidence indicated that intrinsic sequence motifs present in Kir7.1 control surface expression. Mutant Kir7.1 channels are associated with inherited eye pathologies such as Snowflake Vitreoretinal Degeneration (SVD) and Lebers Congenital Amaurosis (LCA16). Based on the current evidence, mutations implicated in channelopathies have the potential to be used for genetic testing to diagnose blindness due to Kir7.1.
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Affiliation(s)
- Mohit Kumar
- a Departments of Biotechnology and Bioinformatics ; NIIT University ; Neemrana , Rajasthan , India
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41
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Nagi K, Charfi I, Pineyro G. Kir3 channels undergo arrestin-dependant internalization following delta opioid receptor activation. Cell Mol Life Sci 2015; 72:3543-57. [PMID: 25900661 PMCID: PMC11113637 DOI: 10.1007/s00018-015-1899-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 04/01/2015] [Accepted: 04/02/2015] [Indexed: 10/23/2022]
Abstract
Kir3 channels control excitability in the nervous system and the heart. Their surface expression is strictly regulated, but mechanisms responsible for channel removal from the membrane remain incompletely understood. Using transfected cells, we show that Kir3.1/3.2 channels and delta opioid receptors (DORs) associate in a complex which persists during receptor activation, behaving as a scaffold that allows beta-arrestin (βarr) to interact with both signaling partners. This organization favored co-internalization of DORs and Kir3 channels in a βarr-dependent manner via a clathrin/dynamin-mediated endocytic path. Taken together, these findings identify a new way of modulating Kir3 channel availability at the membrane and assign a putatively novel role for βarrs in regulating canonical effectors for G protein-coupled receptors.
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Affiliation(s)
- Karim Nagi
- Sainte-Justine Hospital Research Center, 3175 Cote Ste-Catherine, Montreal, QC H3T 1C5 Canada
- Department of Pharmacology, Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4 Canada
| | - Iness Charfi
- Sainte-Justine Hospital Research Center, 3175 Cote Ste-Catherine, Montreal, QC H3T 1C5 Canada
- Department of Pharmacology, Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4 Canada
| | - Graciela Pineyro
- Sainte-Justine Hospital Research Center, 3175 Cote Ste-Catherine, Montreal, QC H3T 1C5 Canada
- Department of Pharmacology, Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4 Canada
- Department of Psychiatry, Faculty of Medicine, University of Montreal, Montreal, QC H3T 1J4 Canada
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42
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Lyu C, Mulder J, Barde S, Sahlholm K, Zeberg H, Nilsson J, Århem P, Hökfelt T, Fried K, Shi TJS. G protein-gated inwardly rectifying potassium channel subunits 1 and 2 are down-regulated in rat dorsal root ganglion neurons and spinal cord after peripheral axotomy. Mol Pain 2015. [PMID: 26199148 PMCID: PMC4511542 DOI: 10.1186/s12990-015-0044-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Background Increased nociceptive neuronal excitability underlies chronic pain conditions. Various ion channels, including sodium, calcium and potassium channels have pivotal roles in the control of neuronal excitability. The members of the family of G protein-gated inwardly rectifying potassium (GIRK) channels, GIRK1–4, have been implicated in modulating excitability. Here, we investigated the expression and distribution of GIRK1 and GIRK2 in normal and injured dorsal root ganglia (DRGs) and spinal cord of rats. Results We found that ~70% of the DRG neurons expressed GIRK1, while only <10% expressed GIRK2. The neurochemical profiles of GIRK1- and GIRK2-immunoreactive neurons were characterized using the neuronal markers calcitonin gene-related peptide, isolectin-B4 and neurofilament-200, and the calcium-binding proteins calbindin D28k, calretinin, parvalbumin and secretagogin. Both GIRK subunits were expressed in DRG neurons with nociceptive characteristics. However, while GIRK1 was widely expressed in several sensory neuronal subtypes, GIRK2 was detected mainly in a group of small C-fiber neurons. In the spinal dorsal horn, GIRK1- and -2-positive cell bodies and processes were mainly observed in lamina II, but also in superficial and deeper layers. Abundant GIRK1-, but not GIRK2-like immunoreactivity, was found in the ventral horn (laminae VI–X). Fourteen days after axotomy, GIRK1 and GIRK2 were down-regulated in DRG neurons at the mRNA and protein levels. Both after axotomy and rhizotomy there was a reduction of GIRK1- and -2-positive processes in the dorsal horn, suggesting a presynaptic localization of these potassium channels. Furthermore, nerve ligation caused accumulation of both subunits on both sides of the lesion, providing evidence for anterograde and retrograde fast axonal transport. Conclusions Our data support the hypothesis that reduced GIRK function is associated with increased neuronal excitability and causes sensory disturbances in post-injury conditions, including neuropathic pain. Electronic supplementary material The online version of this article (doi:10.1186/s12990-015-0044-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chuang Lyu
- School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. .,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Jan Mulder
- Department of Neuroscience, Science for Life Laboratory, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Swapnali Barde
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Kristoffer Sahlholm
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Hugo Zeberg
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Johanna Nilsson
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Peter Århem
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Tomas Hökfelt
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Kaj Fried
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
| | - Tie-Jun Sten Shi
- School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. .,Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
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Spear JM, Koborssy DA, Schwartz AB, Johnson AJ, Audhya A, Fadool DA, Stagg SM. Kv1.3 contains an alternative C-terminal ER exit motif and is recruited into COPII vesicles by Sec24a. BMC BIOCHEMISTRY 2015; 16:16. [PMID: 26156069 PMCID: PMC4497498 DOI: 10.1186/s12858-015-0045-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 06/26/2015] [Indexed: 12/11/2022]
Abstract
Background Potassium channels play a fundamental role in resetting the resting membrane potential of excitable cells. Determining the intracellular trafficking and localization mechanisms of potassium channels provides a platform to fully characterize their maturation and functionality. Previous investigations have discovered residues or motifs that exist in their primary structure, which directly promote anterograde trafficking of nascent potassium channels. Recently, a non-conical di-acidic motif (E483/484) has been discovered in the C-terminus of the mammalian homologue of the Shaker voltage-gated potassium channel subfamily member 3 (Kv1.3), and was shown to disrupt the anterograde trafficking of Kv1.3. Results We have further investigated the intracellular trafficking requirements of Kv1.3 both in vivo and in vitro. First, three alternative C-terminal acidic residues, E443, E445, E447 were probed for their involvement within the early secretory pathway of Kv1.3. Single point (E443A, E445A, and E447A) and double point (E443A-E445A, E445A-E447A) mutations exhibited no significant changes in their endoplasmic reticulum (ER) retention. The triple point mutant E443A-E445A-E447A displayed a modest ER retention while deletion of the C-terminus showed dramatic ER retention. Second, we demonstrate in vivo the requirement for the Sec24a isoform to confer anterograde trafficking using a siRNA knockdown assay. Third, we show in vitro the association of recombinantly expressed Kv1.3 and Sec24a proteins. Conclusion These results expand upon previous studies aimed at deciphering the Kv1.3 secretory trafficking mechanisms and further show in vitro evidence of the association between Kv1.3 and the COPII cargo adaptor subunit isoform Sec24a. Electronic supplementary material The online version of this article (doi:10.1186/s12858-015-0045-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- John M Spear
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
| | - Dolly Al Koborssy
- Program in Neuroscience, Florida State University, 1107 West Call Street, Tallahassee, FL, 32306, USA.
| | - Austin B Schwartz
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
| | - Adam J Johnson
- Biomolecular Chemistry, University of Wisconsin-Madison, 440 Henry Mall, Madison, WI, 53706, USA.
| | - Anjon Audhya
- Biomolecular Chemistry, University of Wisconsin-Madison, 440 Henry Mall, Madison, WI, 53706, USA.
| | - Debra A Fadool
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA. .,Program in Neuroscience, Florida State University, 1107 West Call Street, Tallahassee, FL, 32306, USA. .,Department of Biological Science, Florida State University, 319 Stadium Drive, Tallahassee, FL, 32306, USA.
| | - Scott M Stagg
- Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA. .,Department of Chemistry and Biochemistry, Florida State University, 91 Chieftan Way, Tallahassee, FL, 32306, USA.
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Glaaser IW, Slesinger PA. Structural Insights into GIRK Channel Function. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:117-60. [PMID: 26422984 DOI: 10.1016/bs.irn.2015.05.014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
G protein-gated inwardly rectifying potassium (GIRK; Kir3) channels, which are members of the large family of inwardly rectifying potassium channels (Kir1-Kir7), regulate excitability in the heart and brain. GIRK channels are activated following stimulation of G protein-coupled receptors that couple to the G(i/o) (pertussis toxin-sensitive) G proteins. GIRK channels, like all other Kir channels, possess an extrinsic mechanism of inward rectification involving intracellular Mg(2+) and polyamines that occlude the conduction pathway at membrane potentials positive to E(K). In the past 17 years, more than 20 high-resolution atomic structures containing GIRK channel cytoplasmic domains and transmembrane domains have been solved. These structures have provided valuable insights into the structural determinants of many of the properties common to all inward rectifiers, such as permeation and rectification, as well as revealing the structural bases for GIRK channel gating. In this chapter, we describe advances in our understanding of GIRK channel function based on recent high-resolution atomic structures of inwardly rectifying K(+) channels discussed in the context of classical structure-function experiments.
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Affiliation(s)
- Ian W Glaaser
- Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Paul A Slesinger
- Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
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45
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GIRK3 gates activation of the mesolimbic dopaminergic pathway by ethanol. Proc Natl Acad Sci U S A 2015; 112:7091-6. [PMID: 25964320 DOI: 10.1073/pnas.1416146112] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
G protein-gated inwardly rectifying potassium (GIRK) channels are critical regulators of neuronal excitability and can be directly activated by ethanol. Constitutive deletion of the GIRK3 subunit has minimal phenotypic consequences, except in response to drugs of abuse. Here we investigated how the GIRK3 subunit contributes to the cellular and behavioral effects of ethanol, as well as to voluntary ethanol consumption. We found that constitutive deletion of GIRK3 in knockout (KO) mice selectively increased ethanol binge-like drinking, without affecting ethanol metabolism, sensitivity to ethanol intoxication, or continuous-access drinking. Virally mediated expression of GIRK3 in the ventral tegmental area (VTA) reversed the phenotype of GIRK3 KO mice and further decreased the intake of their wild-type counterparts. In addition, GIRK3 KO mice showed a blunted response of the mesolimbic dopaminergic (DA) pathway to ethanol, as assessed by ethanol-induced excitation of VTA neurons and DA release in the nucleus accumbens. These findings support the notion that the subunit composition of VTA GIRK channels is a critical determinant of DA neuron sensitivity to drugs of abuse. Furthermore, our study reveals the behavioral impact of this cellular effect, whereby the level of GIRK3 expression in the VTA tunes ethanol intake under binge-type conditions: the more GIRK3, the less ethanol drinking.
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Marron Fernandez de Velasco E, Hearing M, Xia Z, Victoria NC, Luján R, Wickman K. Sex differences in GABA(B)R-GIRK signaling in layer 5/6 pyramidal neurons of the mouse prelimbic cortex. Neuropharmacology 2015; 95:353-60. [PMID: 25843643 DOI: 10.1016/j.neuropharm.2015.03.029] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 03/10/2015] [Accepted: 03/24/2015] [Indexed: 10/23/2022]
Abstract
The medial prefrontal cortex (mPFC) has been implicated in multiple disorders characterized by clear sex differences, including schizophrenia, attention deficit hyperactivity disorder, post-traumatic stress disorder, depression, and drug addiction. These sex differences likely represent underlying differences in connectivity and/or the balance of neuronal excitability within the mPFC. Recently, we demonstrated that signaling via the metabotropic γ-aminobutyric acid receptor (GABABR) and G protein-gated inwardly-rectifying K(+) (GIRK/Kir3) channels modulates the excitability of the key output neurons of the mPFC, the layer 5/6 pyramidal neurons. Here, we report a sex difference in the GABABR-GIRK signaling pathway in these neurons. Specifically, GABABR-dependent GIRK currents recorded in the prelimbic region of the mPFC were larger in adolescent male mice than in female counterparts. Interestingly, this sex difference was not observed in layer 5/6 pyramidal neurons of the adjacent infralimbic cortex, nor was it seen in young adult mice. The sex difference in GABABR-GIRK signaling is not attributable to different expression levels of signaling pathway components, but rather to a phosphorylation-dependent trafficking mechanism. Thus, sex differences related to some diseases associated with altered mPFC function may be explained in part by sex differences in GIRK-dependent signaling in mPFC pyramidal neurons.
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Affiliation(s)
| | - Matthew Hearing
- Department of Neuroscience, University of Minnesota, 6-145 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Zhilian Xia
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Nicole C Victoria
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Rafael Luján
- IDINE, Departmento de Ciencias Médicas, Facultad de Medicina, Universidad de Castilla La Mancha, C/Almansa 14, 02006, Albacete, Spain
| | - Kevin Wickman
- Department of Pharmacology, University of Minnesota, 6-120 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA.
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The role of protein-protein interactions in the intracellular traffic of the potassium channels TASK-1 and TASK-3. Pflugers Arch 2015; 467:1105-20. [PMID: 25559843 DOI: 10.1007/s00424-014-1672-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 12/10/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022]
Abstract
The intracellular transport of membrane proteins is controlled by trafficking signals: Short peptide motifs that mediate the contact with COPI, COPII or various clathrin-associated coat proteins. In addition, many membrane proteins interact with accessory proteins that are involved in the sorting of these proteins to different intracellular compartments. In the K2P channels, TASK-1 and TASK-3, the influence of protein-protein interactions on sorting decisions has been studied in some detail. Both TASK paralogues interact with the adaptor protein 14-3-3; TASK-1 interacts, in addition, with the adaptor protein p11 (S100A10) and the endosomal SNARE protein syntaxin-8. The role of these interacting proteins in controlling the intracellular traffic of the channels and the underlying molecular mechanisms are summarised in this review. In the case of 14-3-3, the interacting protein masks a retention signal in the C-terminus of the channel; in the case of p11, the interacting protein carries a retention signal that localises the channel to the endoplasmic reticulum; and in the case of syntaxin-8, the interacting protein carries an endocytosis signal that complements an endocytosis signal of the channel. These examples illustrate some of the mechanisms by which interacting proteins may determine the itinerary of a membrane protein within a cell and suggest that the intracellular traffic of membrane proteins may be adapted to the specific functions of that protein by multiple protein-protein interactions.
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Dascal N, Kahanovitch U. The Roles of Gβγ and Gα in Gating and Regulation of GIRK Channels. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:27-85. [DOI: 10.1016/bs.irn.2015.06.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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de Velasco EMF, McCall N, Wickman K. GIRK Channel Plasticity and Implications for Drug Addiction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:201-38. [DOI: 10.1016/bs.irn.2015.05.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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GIRK Channels: A Potential Link Between Learning and Addiction. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:239-77. [PMID: 26422987 DOI: 10.1016/bs.irn.2015.05.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The ability of drug-associated cues to reinitiate drug craving and seeking, even after long periods of abstinence, has led to the hypothesis that addiction represents a form of pathological learning, in which drugs of abuse hijack normal learning and memory processes to support long-term addictive behaviors. In this chapter, we review evidence suggesting that G protein-gated inwardly rectifying potassium (GIRK/Kir3) channels are one mechanism through which numerous drugs of abuse can modulate learning and memory processes. We will examine the role of GIRK channels in two forms of experience-dependent long-term changes in neuronal function: homeostatic plasticity and synaptic plasticity. We will also discuss how drug-induced changes in GIRK-mediated signaling can lead to changes that support the development and maintenance of addiction.
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