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Miller CN, Li Y, Beier KT, Aoto J. Acute stress causes sex-dependent changes to ventral subiculum synapses, circuitry, and anxiety-like behavior. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.02.606264. [PMID: 39131353 PMCID: PMC11312572 DOI: 10.1101/2024.08.02.606264] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/13/2024]
Abstract
Experiencing a single severe stressor is sufficient to drive sexually dimorphic psychiatric disease development. The ventral subiculum (vSUB) emerges as a site where stress may induce sexually dimorphic adaptations due to its sex-specific organization and pivotal role in stress integration. Using a 1-hr acute restraint stress model, we uncover that stress causes a net decrease in vSUB activity in females that is potent, long-lasting, and driven by adrenergic receptor signaling. By contrast, males exhibit a net increase in vSUB activity that is transient and driven by corticosterone signaling. We further identified sex-dependent changes in vSUB output to the bed nucleus of the stria terminalis and in anxiety-like behavior in response to stress. These findings reveal striking changes in psychiatric disease-relevant brain regions and behavior following stress with sex-, cell-type, and synapse-specificity that contribute to our understanding of sex-dependent adaptations that may shape stress-related psychiatric disease risk.
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Affiliation(s)
- Carley N Miller
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Yuan Li
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA 92697
| | - Kevin T Beier
- Department of Physiology and Biophysics, University of California, Irvine, CA, USA 92697
- Department of Neurobiology and Behavior, University of California, Irvine, CA, USA 92697
- Department of Biomedical Engineering, University of California, Irvine, CA, USA 92697
- Department of Pharmaceutical Sciences, University of California, Irvine, CA, USA 92697
| | - Jason Aoto
- Department of Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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2
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Tureček R, Melichar A, Králíková M, Hrušková B. The role of GABA B receptors in the subcortical pathways of the mammalian auditory system. Front Endocrinol (Lausanne) 2023; 14:1195038. [PMID: 37635966 PMCID: PMC10456889 DOI: 10.3389/fendo.2023.1195038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
GABAB receptors are G-protein coupled receptors for the inhibitory neurotransmitter GABA. Functional GABAB receptors are formed as heteromers of GABAB1 and GABAB2 subunits, which further associate with various regulatory and signaling proteins to provide receptor complexes with distinct pharmacological and physiological properties. GABAB receptors are widely distributed in nervous tissue, where they are involved in a number of processes and in turn are subject to a number of regulatory mechanisms. In this review, we summarize current knowledge of the cellular distribution and function of the receptors in the inner ear and auditory pathway of the mammalian brainstem and midbrain. The findings suggest that in these regions, GABAB receptors are involved in processes essential for proper auditory function, such as cochlear amplifier modulation, regulation of spontaneous activity, binaural and temporal information processing, and predictive coding. Since impaired GABAergic inhibition has been found to be associated with various forms of hearing loss, GABAB dysfunction could also play a role in some pathologies of the auditory system.
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Affiliation(s)
- Rostislav Tureček
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Adolf Melichar
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Michaela Králíková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Bohdana Hrušková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
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3
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Wang B, Zhao M, Su Z, Jin B, Yang X, Zhang C, Guo B, Li J, Hong W, Liu J, Zhao Y, Hou Y, Lai F, Zhang W, Qin L, Zhang W, Luo J, Zheng R. RIIβ-PKA in GABAergic Neurons of Dorsal Median Hypothalamus Governs White Adipose Browning. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2205173. [PMID: 36529950 PMCID: PMC9929258 DOI: 10.1002/advs.202205173] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/18/2022] [Indexed: 06/17/2023]
Abstract
The RIIβ subunit of cAMP-dependent protein kinase A (PKA) is expressed in the brain and adipose tissue. RIIβ-knockout mice show leanness and increased UCP1 in brown adipose tissue. The authors have previously reported that RIIβ reexpression in hypothalamic GABAergic neurons rescues the leanness. However, whether white adipose tissue (WAT) browning contributes to the leanness and whether RIIβ-PKA in these neurons governs WAT browning are unknown. Here, this work reports that RIIβ-KO mice exhibit a robust WAT browning. RIIβ reexpression in dorsal median hypothalamic GABAergic neurons (DMH GABAergic neurons) abrogates WAT browning. Single-cell sequencing, transcriptome sequencing, and electrophysiological studies show increased GABAergic activity in DMH GABAergic neurons of RIIβ-KO mice. Activation of DMH GABAergic neurons or inhibition of PKA in these neurons elicits WAT browning and thus lowers body weight. These findings reveal that RIIβ-PKA in DMH GABAergic neurons regulates WAT browning. Targeting RIIβ-PKA in DMH GABAergic neurons may offer a clinically useful way to promote WAT browning for treating obesity and other metabolic disorders.
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Affiliation(s)
- Bingwei Wang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Miao Zhao
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Zhijie Su
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Baohua Jin
- Department of PharmacologyInstitution of Chinese Integrative MedicineHebei Medical UniversityShijiazhuang050017P. R. China
| | - Xiaoning Yang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Chenyu Zhang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Bingbing Guo
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Jiebo Li
- Institute of Medical PhotonicsBeijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijing100191P. R. China
| | - Weili Hong
- Institute of Medical PhotonicsBeijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijing100191P. R. China
| | - Jiarui Liu
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Yun Zhao
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Yujia Hou
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Futing Lai
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Wei Zhang
- Department of PharmacologyInstitution of Chinese Integrative MedicineHebei Medical UniversityShijiazhuang050017P. R. China
| | - Lihua Qin
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Weiguang Zhang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Jianyuan Luo
- Department of Medical GeneticsSchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
- Department of Biochemistry and Molecular BiologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Ruimao Zheng
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
- Neuroscience Research InstituteKey Laboratory for Neuroscience of Ministry of EducationKey Laboratory for Neuroscience of National Health Commission of the People's Republic of ChinaPeking UniversityBeijing100191P. R. China
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4
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Unravelling biological roles and mechanisms of GABA BR on addiction and depression through mood and memory disorders. Biomed Pharmacother 2022; 155:113700. [PMID: 36152411 DOI: 10.1016/j.biopha.2022.113700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/08/2022] [Accepted: 09/13/2022] [Indexed: 11/23/2022] Open
Abstract
The metabotropic γ-aminobutyric acid type B receptor (GABABR) remains a hotspot in the recent research area. Being an idiosyncratic G-protein coupled receptor family member, the GABABR manifests adaptively tailored functionality under multifarious modulations by a constellation of agents, pointing to cross-talk between receptors and effectors that converge on the domains of mood and memory. This review systematically summarizes the latest achievements in signal transduction mechanisms of the GABABR-effector-regulator complex and probes how the up-and down-regulation of membrane-delimited GABABRs are associated with manifold intrinsic and extrinsic agents in synaptic strength and plasticity. Neuropsychiatric conditions depression and addiction share the similar pathophysiology of synapse inadaptability underlying negative mood-related processes, memory formations, and impairments. In the attempt to emphasize all convergent discoveries, we hope the insights gained on the GABABR system mechanisms of action are conducive to designing more therapeutic candidates so as to refine the prognosis rate of diseases and minimize side effects.
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5
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Onishi Y, Yamamura Y, Hosogi M, Higashi H, Ogita K, Kinjo T, Uno K, Yoneda Y, Kuramoto N. Delayed Expression of Both GABA BR1 and GABA BR2 Subunits in Murine Hippocampal Dentate Gyrus After a Single Systemic Injection of Trimethyltin. Neurochem Res 2022; 47:2780-2792. [PMID: 35737203 DOI: 10.1007/s11064-022-03652-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/26/2022] [Accepted: 06/06/2022] [Indexed: 11/24/2022]
Abstract
Trimethyltin (TMT) has been used as a cytotoxin to neurons rather than glial cells in the mammalian hippocampus. The systemic administration of TMT led to declined fluorescence of ZnAF-2 DA staining as a marker of intact mossy fibers and increased fluorescence of Fluoro-Jade B staining as a marker of degenerated neurons during the initial 2 to 5 days after the administration with later ameliorations within 30 days in the hippocampal dentate gyrus (DG) and CA3 region in mice. On immunoblotting analysis, both GABABR1 and GABABR2 subunit levels increased during 15 to 30 days after TMT along with significant decreases in glutamatergic GluA1 and GluA2/3 receptor subunit levels during 2 to 7 days in the DG, but not in other hippocampal regions such as CA1 and CA3 regions. Immunohistochemical analysis revealed the constitutive and inducible expression of GABABR2 subunit in cells immunoreactive to an astrocytic marker as well as neuronal markers in the DG with the absence of neither GABABR1a nor GABABR1b subunit from cells positive to an astrocytic marker. These results suggest that both GABABR1 and GABABR2 subunits may be up-regulated in cells other than neurons and astroglia in the DG at a late stage of TMT intoxication in mice.
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Affiliation(s)
- Yuki Onishi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Hiroshima International University, Hiroshima, 737-0112, Japan
| | - Yusuke Yamamura
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
| | - Misa Hosogi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Hiroshi Higashi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Kiyokazu Ogita
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
- Setsunan University, 17-8 Ikedanakamachi, Neyagawa, Osaka, 572-8508, Japan
| | - Toshihiko Kinjo
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Kyosuke Uno
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Yukio Yoneda
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Nobuyuki Kuramoto
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan.
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan.
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan.
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Salvati KA, Ritger ML, Davoudian PA, O’Dell F, Wyskiel DR, Souza GMPR, Lu AC, Perez-Reyes E, Drake JC, Yan Z, Beenhakker MP. OUP accepted manuscript. Brain 2022; 145:2332-2346. [PMID: 35134125 PMCID: PMC9337815 DOI: 10.1093/brain/awac037] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 12/20/2021] [Accepted: 12/26/2021] [Indexed: 11/21/2022] Open
Abstract
Metabolism regulates neuronal activity and modulates the occurrence of epileptic seizures. Here, using two rodent models of absence epilepsy, we show that hypoglycaemia increases the occurrence of spike-wave seizures. We then show that selectively disrupting glycolysis in the thalamus, a structure implicated in absence epilepsy, is sufficient to increase spike-wave seizures. We propose that activation of thalamic AMP-activated protein kinase, a sensor of cellular energetic stress and potentiator of metabotropic GABAB-receptor function, is a significant driver of hypoglycaemia-induced spike-wave seizures. We show that AMP-activated protein kinase augments postsynaptic GABAB-receptor-mediated currents in thalamocortical neurons and strengthens epileptiform network activity evoked in thalamic brain slices. Selective thalamic AMP-activated protein kinase activation also increases spike-wave seizures. Finally, systemic administration of metformin, an AMP-activated protein kinase agonist and common diabetes treatment, profoundly increased spike-wave seizures. These results advance the decades-old observation that glucose metabolism regulates thalamocortical circuit excitability by demonstrating that AMP-activated protein kinase and GABAB-receptor cooperativity is sufficient to provoke spike-wave seizures.
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Affiliation(s)
- Kathryn A Salvati
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
- Epilepsy Research Laboratory and Weil Institute for Neurosciences, Department of Neurological Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Matthew L Ritger
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Pasha A Davoudian
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
- MD-PhD Program, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Finnegan O’Dell
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Daniel R Wyskiel
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - George M P R Souza
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Adam C Lu
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Edward Perez-Reyes
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Joshua C Drake
- Department of Human Nutrition, Foods and Exercise, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
- The Robert M. Berne Center for Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Zhen Yan
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
- The Robert M. Berne Center for Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
- Department of Medicine, University of Virginia School of Medicine, Charlottesville, VA, USA
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Mark P Beenhakker
- Correspondence to: Mark P. Beenhakker Department of Pharmacology University of Virginia School of Medicine Charlottesville, VA, 22908, USA E-mail:
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7
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Hamad MIK, Jbara A, Rabaya O, Petrova P, Daoud S, Melliti N, Meseke M, Lutz D, Petrasch-Parwez E, Schwitalla JC, Mark MD, Herlitze S, Reiss G, Herz J, Förster E. Reelin signaling modulates GABA B receptor function in the neocortex. J Neurochem 2021; 156:589-603. [PMID: 32083308 PMCID: PMC7442713 DOI: 10.1111/jnc.14990] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 01/27/2020] [Accepted: 02/18/2020] [Indexed: 11/27/2022]
Abstract
Reelin is a protein that is best known for its role in controlling neuronal layer formation in the developing cortex. Here, we studied its role for post-natal cortical network function, which is poorly explored. To preclude early cortical migration defects caused by Reelin deficiency, we used a conditional Reelin knock-out (RelncKO ) mouse, and induced Reelin deficiency post-natally. Induced Reelin deficiency caused hyperexcitability of the neocortical network in vitro and ex vivo. Blocking Reelin binding to its receptors ApoER2 and VLDLR resulted in a similar effect. Hyperexcitability in RelncKO organotypic slice cultures could be rescued by co-culture with wild-type organotypic slice cultures. Moreover, the GABAB receptor (GABAB R) agonist baclofen failed to activate and the antagonist CGP35348 failed to block GABAB Rs in RelncKO mice. Immunolabeling of RelncKO cortical slices revealed a reduction in GABAB R1 and GABAB R2 surface expression at the plasma membrane and western blot of RelncKO cortical tissue revealed decreased phosphorylation of the GABAB R2 subunit at serine 892 and increased phosphorylation at serine 783, reflecting receptor deactivation and proteolysis. These data show a role of Reelin in controlling early network activity, by modulating GABAB R function. Cover Image for this issue: https://doi.org/10.1111/jnc.15054.
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Affiliation(s)
- Mohammad I K Hamad
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
- Institute for Anatomy and Clinical Morphology, School of Medicine, Faculty of Health, Herdecke University, Witten, Witten
| | - Abdalrahim Jbara
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Obada Rabaya
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Petya Petrova
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Solieman Daoud
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Nesrine Melliti
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Maurice Meseke
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - David Lutz
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | - Elisabeth Petrasch-Parwez
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
| | | | - Melanie D Mark
- Department of Behavioral Neuroscience, Ruhr University Bochum, Bochum, Germany
| | - Stefan Herlitze
- Department of Zoology and Neurobiology, Ruhr University Bochum, Bochum, Germany
| | - Gebhard Reiss
- Institute for Anatomy and Clinical Morphology, School of Medicine, Faculty of Health, Herdecke University, Witten, Witten
| | - Joachim Herz
- Departments of Molecular Genetics, Neuroscience, Neurology and Neurotherapeutics, Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Eckart Förster
- Department of Neuroanatomy and Molecular Brain Research, Ruhr University Bochum, Medical Faculty, Bochum, Germany
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8
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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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9
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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10
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Regulated expression and function of the GABA B receptor in human pancreatic beta cell line and islets. Sci Rep 2020; 10:13469. [PMID: 32778664 PMCID: PMC7417582 DOI: 10.1038/s41598-020-69758-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 06/26/2020] [Indexed: 02/06/2023] Open
Abstract
G protein-coupled receptors are seven transmembrane signaling molecules that are involved in a wide variety of physiological processes. They constitute a large protein family of receptors with almost 300 members detected in human pancreatic islet preparations. However, the functional role of these receptors in pancreatic islets is unknown in most cases. We generated a new stable human beta cell line from neonatal pancreas. This cell line, named ECN90 expresses both subunits (GABBR1 and GABBR2) of the metabotropic GABAB receptor compared to human islet. In ECN90 cells, baclofen, a specific GABAB receptor agonist, inhibits cAMP signaling causing decreased expression of beta cell-specific genes such as MAFA and PCSK1, and reduced insulin secretion. We next demonstrated that in primary human islets, GABBR2 mRNA expression is strongly induced under cAMP signaling, while GABBR1 mRNA is constitutively expressed. We also found that induction and activation of the GABAB receptor in human islets modulates insulin secretion.
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11
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Extracellular Signal-Regulated Kinases Mediate an Autoregulation of GABA B-Receptor-Activated Whole-Cell Current in Locus Coeruleus Neurons. Sci Rep 2020; 10:7869. [PMID: 32398643 PMCID: PMC7217949 DOI: 10.1038/s41598-020-64292-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 04/09/2020] [Indexed: 11/09/2022] Open
Abstract
The norepinephrine-releasing neurons in the locus coeruleus (LC) are well known to regulate wakefulness/arousal. They display active firing during wakefulness and a decreased discharge rate during sleep. We have previously reported that LC neurons express large numbers of GABAB receptors (GABABRs) located at peri-/extrasynaptic sites and are subject to tonic inhibition due to the continuous activation of GABABRs by ambient GABA, which is significantly higher during sleep than during wakefulness. In this study, we further showed using western blot analysis that the activation of GABABRs with baclofen could increase the level of phosphorylated extracellular signal-regulated kinase 1 (ERK1) in LC tissue. Recordings from LC neurons in brain slices showed that the inhibition of ERK1/2 with U0126 and FR180204 accelerated the decay of whole-cell membrane current induced by prolonged baclofen application. In addition, the inhibition of ERK1/2 also increased spontaneous firing and reduced tonic inhibition of LC neurons after prolonged exposure to baclofen. These results suggest a new role of GABABRs in mediating ERK1-dependent autoregulation of the stability of GABABR-activated whole-cell current, in addition to its well-known effect on gated potassium channels, to cause a tonic current in LC neurons.
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12
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Direct Interaction of PP2A Phosphatase with GABA B Receptors Alters Functional Signaling. J Neurosci 2020; 40:2808-2816. [PMID: 32111696 PMCID: PMC7117905 DOI: 10.1523/jneurosci.2654-19.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 01/02/2020] [Accepted: 02/18/2020] [Indexed: 01/16/2023] Open
Abstract
Addictive drugs usurp the brain's intrinsic mechanism for reward, leading to compulsive and destructive behaviors. In the ventral tegmental area (VTA), the center of the brain's reward circuit, GABAergic neurons control the excitability of dopamine (DA) projection neurons and are the site of initial psychostimulant-dependent changes in signaling. Previous work established that cocaine/methamphetamine exposure increases protein phosphatase 2A (PP2A) activity, which dephosphorylates the GABABR2 subunit, promotes internalization of the GABAB receptor (GABABR) and leads to smaller GABABR-activated G-protein-gated inwardly rectifying potassium (GIRK) currents in VTA GABA neurons. How the actions of PP2A become selective for a particular signaling pathway is poorly understood. Here, we demonstrate that PP2A can associate directly with a short peptide sequence in the C terminal domain of the GABABR1 subunit, and that GABABRs and PP2A are in close proximity in rodent neurons (mouse/rat; mixed sexes). We show that this PP2A-GABABR interaction can be regulated by intracellular Ca2+ Finally, a peptide that potentially reduces recruitment of PP2A to GABABRs and thereby limits receptor dephosphorylation increases the magnitude of baclofen-induced GIRK currents. Thus, limiting PP2A-dependent dephosphorylation of GABABRs may be a useful strategy to increase receptor signaling for treating diseases.SIGNIFICANCE STATEMENT Dysregulation of GABAB receptors (GABABRs) underlies altered neurotransmission in many neurological disorders. Protein phosphatase 2A (PP2A) is involved in dephosphorylating and subsequent internalization of GABABRs in models of addiction and depression. Here, we provide new evidence that PP2A B55 regulatory subunit interacts directly with a small region of the C-terminal domain of the GABABR1 subunit, and that this interaction is sensitive to intracellular Ca2+ We demonstrate that a short peptide corresponding to the PP2A interaction site on GABABR1 competes for PP2A binding, enhances phosphorylation GABABR2 S783, and affects functional signaling through GIRK channels. Our study highlights how targeting PP2A dependent dephosphorylation of GABABRs may provide a specific strategy to modulate GABABR signaling in disease conditions.
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The Therapeutic Potential of the Labdane Diterpenoid Forskolin. APPLIED SCIENCES-BASEL 2019. [DOI: 10.3390/app9194089] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Forskolin is mainly found in the root of a plant called Coleus forskohlii (Willd.) Briq., which has been used in the traditional medicine of Indian Ayurvedic and Southeast Asia since ancient times. Forskolin is responsible for the pharmacological activity of this species. Forskolin is a labdane diterpenoid with a wide biological effect. Several studies suggested a positive role of forskolin on heart complications, respiratory disorders, high blood pressure, obesity, and asthma. There are numerous clinical and pre-clinical studies representing the effect of forskolin on the above-mentioned disorders but more clinical studies need to be performed to support its efficacy.
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Phosphoproteomic analysis of cocaine memory extinction and reconsolidation in the nucleus accumbens. Psychopharmacology (Berl) 2019; 236:531-543. [PMID: 30411139 PMCID: PMC6374162 DOI: 10.1007/s00213-018-5071-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/04/2018] [Indexed: 12/25/2022]
Abstract
RATIONALE Environmental stimuli, or cues, associated with the use of drugs such as cocaine are one of the primary drivers of relapse. Thus, identifying mechanisms to reduce the motivational properties of drug cues is an important research goal. OBJECTIVES The purpose of this study was to identify cellular signaling events in the nucleus accumbens (NAc) that are induced when a cocaine cue memory is either extinguished through repeated cue presentation in the absence of drug, or when the memory is reactivated and reconsolidated by a brief cue re-exposure. Signaling events specific to extinction or reconsolidation represent potential targets for pharmacotherapeutics that may enhance extinction or disrupt reconsolidation to reduce the likelihood of relapse. METHODS Male Sprague-Dawley rats were trained to self-administer cocaine paired with an audiovisual cue. Following a period of self-administration, the memory for the cocaine-associated cue was either extinguished, reactivated, or not manipulated (control) 15 min before sacrifice. Tissue from the NAc was subsequently analyzed using mass spectrometry based phosphoproteomics to identify cellular signaling events induced by each condition. RESULTS Extinction and reconsolidation of the cocaine cue memory produced both common and distinct changes in protein phosphorylation. Notably, there were no significant changes in protein phosphorylation that were modulated in the opposite direction by the two behavioral conditions. Comparison of NAc phosphoproteomic changes to previously identified changes in the basolateral amygdala (BLA) revealed that cue extinction increases phosphorylation at serine (S) 883 of the GABAB receptor subunit 2 and on S14 of syntaxin 1a in both regions, while no common regional signaling events were identified in the reconsolidation group. CONCLUSIONS Phosphoproteomics is a useful tool for identifying signaling cascades involved in different memory processes and revealed novel potential targets for selectively targeting extinction versus reconsolidation of a cocaine cue memory. Furthermore, cross region analysis suggests that cue extinction may produce unique signaling events associated with increased inhibitory signaling.
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Czéh B, Vardya I, Varga Z, Febbraro F, Csabai D, Martis LS, Højgaard K, Henningsen K, Bouzinova EV, Miseta A, Jensen K, Wiborg O. Long-Term Stress Disrupts the Structural and Functional Integrity of GABAergic Neuronal Networks in the Medial Prefrontal Cortex of Rats. Front Cell Neurosci 2018; 12:148. [PMID: 29973870 PMCID: PMC6020798 DOI: 10.3389/fncel.2018.00148] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Accepted: 05/14/2018] [Indexed: 12/12/2022] Open
Abstract
Clinical and experimental data suggest that fronto-cortical GABAergic deficits contribute to the pathophysiology of major depressive disorder (MDD). To further test this hypothesis, we used a well characterized rat model for depression and examined the effect of stress on GABAergic neuron numbers and GABA-mediated synaptic transmission in the medial prefrontal cortex (mPFC) of rats. Adult male Wistar rats were subjected to 9-weeks of chronic mild stress (CMS) and based on their hedonic-anhedonic behavior they were behaviorally phenotyped as being stress-susceptible (anhedonic) or stress-resilient. Post mortem quantitative histopathology was used to examine the effect of stress on parvalbumin (PV)-, calretinin- (CR), calbindin- (CB), cholecystokinin- (CCK), somatostatin-(SST) and neuropeptide Y-positive (NPY+) GABAergic neuron numbers in all cortical subareas of the mPFC (anterior cingulate (Cg1), prelimbic (PrL) and infralimbic (IL) cortexes). In vitro, whole-cell patch-clamp recordings from layer II–III pyramidal neurons of the ventral mPFC was used to examine GABAergic neurotransmission. The cognitive performance of the animals was assessed in a hippocampal-prefrontal-cortical circuit dependent learning task. Stress exposure reduced the number of CCK-, CR- and PV-positive GABAergic neurons in the mPFC, most prominently in the IL cortex. Interestingly, in the stress-resilient animals, we found higher number of neuropeptide Y-positive neurons in the entire mPFC. The electrophysiological analysis revealed reduced frequencies of spontaneous and miniature IPSCs in the anhedonic rats and decreased release probability of perisomatic-targeting GABAergic synapses and alterations in GABAB receptor mediated signaling. In turn, pyramidal neurons showed higher excitability. Anhedonic rats were also significantly impaired in the object-place paired-associate learning task. These data demonstrate that long-term stress results in functional and structural deficits of prefrontal GABAergic networks. Our findings support the concept that fronto-limbic GABAergic dysfunctions may contribute to emotional and cognitive symptoms of MDD.
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Affiliation(s)
- Boldizsár Czéh
- Department of Clinical Medicine, Aarhus University, Risskov, Denmark.,Neurobiology of Stress Research Group, János Szentágothai Research Centre & Centre for Neuroscience, Pécs, Hungary.,Department of Laboratory Medicine, University of Pécs, Medical School, Pécs, Hungary
| | - Irina Vardya
- Synaptic Physiology Laboratory, Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Zsófia Varga
- Neurobiology of Stress Research Group, János Szentágothai Research Centre & Centre for Neuroscience, Pécs, Hungary
| | - Fabia Febbraro
- Department of Clinical Medicine, Aarhus University, Risskov, Denmark
| | - Dávid Csabai
- Neurobiology of Stress Research Group, János Szentágothai Research Centre & Centre for Neuroscience, Pécs, Hungary
| | | | | | - Kim Henningsen
- Department of Clinical Medicine, Aarhus University, Risskov, Denmark
| | - Elena V Bouzinova
- Department of Clinical Medicine, Aarhus University, Risskov, Denmark
| | - Attila Miseta
- Department of Laboratory Medicine, University of Pécs, Medical School, Pécs, Hungary
| | - Kimmo Jensen
- Synaptic Physiology Laboratory, Department of Biomedicine, Aarhus University, Aarhus, Denmark.,Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Ove Wiborg
- Department of Clinical Medicine, Aarhus University, Risskov, Denmark.,Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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TERUNUMA M. Diversity of structure and function of GABA B receptors: a complexity of GABA B-mediated signaling. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2018; 94:390-411. [PMID: 30541966 PMCID: PMC6374141 DOI: 10.2183/pjab.94.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/09/2018] [Indexed: 05/24/2023]
Abstract
γ-aminobutyric acid type B (GABAB) receptors are broadly expressed in the nervous system and play an important role in neuronal excitability. GABAB receptors are G protein-coupled receptors that mediate slow and prolonged inhibitory action, via activation of Gαi/o-type proteins. GABAB receptors mediate their inhibitory action through activating inwardly rectifying K+ channels, inactivating voltage-gated Ca2+ channels, and inhibiting adenylate cyclase. Functional GABAB receptors are obligate heterodimers formed by the co-assembly of R1 and R2 subunits. It is well established that GABAB receptors interact not only with G proteins and effectors but also with various proteins. This review summarizes the structure, subunit isoforms, and function of GABAB receptors, and discusses the complexity of GABAB receptors, including how receptors are localized in specific subcellular compartments, the mechanism regulating cell surface expression and mobility of the receptors, and the diversity of receptor signaling through receptor crosstalk and interacting proteins.
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Affiliation(s)
- Miho TERUNUMA
- Division of Oral Biochemistry, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
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Kang JY, Chadchankar J, Vien TN, Mighdoll MI, Hyde TM, Mather RJ, Deeb TZ, Pangalos MN, Brandon NJ, Dunlop J, Moss SJ. Deficits in the activity of presynaptic γ-aminobutyric acid type B receptors contribute to altered neuronal excitability in fragile X syndrome. J Biol Chem 2017; 292:6621-6632. [PMID: 28213518 PMCID: PMC5399111 DOI: 10.1074/jbc.m116.772541] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 02/07/2017] [Indexed: 11/06/2022] Open
Abstract
The behavioral and anatomical deficits seen in fragile X syndrome (FXS) are widely believed to result from imbalances in the relative strengths of excitatory and inhibitory neurotransmission. Although modified neuronal excitability is thought to be of significance, the contribution that alterations in GABAergic inhibition play in the pathophysiology of FXS are ill defined. Slow sustained neuronal inhibition is mediated by γ-aminobutyric acid type B (GABAB) receptors, which are heterodimeric G-protein-coupled receptors constructed from R1a and R2 or R1b and R2 subunits. Via the activation of Gi/o, they limit cAMP accumulation, diminish neurotransmitter release, and induce neuronal hyperpolarization. Here we reveal that selective deficits in R1a subunit expression are seen in Fmr1 knock-out mice (KO) mice, a widely used animal model of FXS, but the levels of the respective mRNAs were unaffected. Similar trends of R1a expression were seen in a subset of FXS patients. GABAB receptors (GABABRs) exert powerful pre- and postsynaptic inhibitory effects on neurotransmission. R1a-containing GABABRs are believed to mediate presynaptic inhibition in principal neurons. In accordance with this result, deficits in the ability of GABABRs to suppress glutamate release were seen in Fmr1-KO mice. In contrast, the ability of GABABRs to suppress GABA release and induce postsynaptic hyperpolarization was unaffected. Significantly, this deficit contributes to the pathophysiology of FXS as the GABABR agonist (R)-baclofen rescued the imbalances between excitatory and inhibitory neurotransmission evident in Fmr1-KO mice. Collectively, our results provided evidence that selective deficits in the activity of presynaptic GABABRs contribute to the pathophysiology of FXS.
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Affiliation(s)
- Ji-Yong Kang
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Jayashree Chadchankar
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Thuy N Vien
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | | | - Thomas M Hyde
- the Lieber Institute for Brain Development and
- Departments of Neurology and Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Robert J Mather
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience, Innovative Medicines and Early Development, AstraZeneca, Waltham, Massachusetts 02451
| | - Tarek Z Deeb
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Menelas N Pangalos
- Innovative Medicines and Early Development, AstraZeneca, Melbourn Science Park, Cambridge Road, Royston Herts SG8 6EE, United Kingdom, and
| | - Nicholas J Brandon
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience, Innovative Medicines and Early Development, AstraZeneca, Waltham, Massachusetts 02451
| | - John Dunlop
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
- Neuroscience, Innovative Medicines and Early Development, AstraZeneca, Waltham, Massachusetts 02451
| | - Stephen J Moss
- From the AstraZeneca Tufts Laboratory for Basic and Translational Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111,
- Neuroscience, Innovative Medicines and Early Development, AstraZeneca, Waltham, Massachusetts 02451
- the Department of Neuroscience, Physiology and Pharmacology, University College, London WC1E 6BT, United Kingdom
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Yang Z, Yang F, Zhang D, Liu Z, Lin A, Liu C, Xiao P, Yu X, Sun JP. Phosphorylation of G Protein-Coupled Receptors: From the Barcode Hypothesis to the Flute Model. Mol Pharmacol 2017; 92:201-210. [DOI: 10.1124/mol.116.107839] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Accepted: 02/23/2017] [Indexed: 12/21/2022] Open
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KCTD Hetero-oligomers Confer Unique Kinetic Properties on Hippocampal GABAB Receptor-Induced K+ Currents. J Neurosci 2016; 37:1162-1175. [PMID: 28003345 DOI: 10.1523/jneurosci.2181-16.2016] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 11/29/2016] [Accepted: 12/12/2016] [Indexed: 11/21/2022] Open
Abstract
GABAB receptors are the G-protein coupled receptors for the main inhibitory neurotransmitter in the brain, GABA. GABAB receptors were shown to associate with homo-oligomers of auxiliary KCTD8, KCTD12, KCTD12b, and KCTD16 subunits (named after their T1 K+-channel tetramerization domain) that regulate G-protein signaling of the receptor. Here we provide evidence that GABAB receptors also associate with hetero-oligomers of KCTD subunits. Coimmunoprecipitation experiments indicate that two-thirds of the KCTD16 proteins in the hippocampus of adult mice associate with KCTD12. We show that the KCTD proteins hetero-oligomerize through self-interacting T1 and H1 homology domains. Bioluminescence resonance energy transfer measurements in live cells reveal that KCTD12/KCTD16 hetero-oligomers associate with both the receptor and the G-protein. Electrophysiological experiments demonstrate that KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties on G-protein-activated Kir3 currents. During prolonged receptor activation (one min) KCTD12/KCTD16 hetero-oligomers produce moderately desensitizing fast deactivating K+ currents, whereas KCTD12 and KCTD16 homo-oligomers produce strongly desensitizing fast deactivating currents and nondesensitizing slowly deactivating currents, respectively. During short activation (2 s) KCTD12/KCTD16 hetero-oligomers produce nondesensitizing slowly deactivating currents. Electrophysiological recordings from hippocampal neurons of KCTD knock-out mice are consistent with these findings and indicate that KCTD12/KCTD16 hetero-oligomers increase the duration of slow IPSCs. In summary, our data demonstrate that simultaneous assembly of distinct KCTDs at the receptor increases the molecular and functional repertoire of native GABAB receptors and modulates physiologically induced K+ current responses in the hippocampus. SIGNIFICANCE STATEMENT The KCTD proteins 8, 12, and 16 are auxiliary subunits of GABAB receptors that differentially regulate G-protein signaling of the receptor. The KCTD proteins are generally assumed to function as homo-oligomers. Here we show that the KCTD proteins also assemble hetero-oligomers in all possible dual combinations. Experiments in live cells demonstrate that KCTD hetero-oligomers form at least tetramers and that these tetramers directly interact with the receptor and the G-protein. KCTD12/KCTD16 hetero-oligomers impart unique kinetic properties to GABAB receptor-induced Kir3 currents in heterologous cells. KCTD12/KCTD16 hetero-oligomers are abundant in the hippocampus, where they prolong the duration of slow IPSCs in pyramidal cells. Our data therefore support that KCTD hetero-oligomers modulate physiologically induced K+ current responses in the brain.
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Hannan S, Gerrow K, Triller A, Smart TG. Phospho-dependent Accumulation of GABABRs at Presynaptic Terminals after NMDAR Activation. Cell Rep 2016; 16:1962-73. [PMID: 27498877 PMCID: PMC4987283 DOI: 10.1016/j.celrep.2016.07.021] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/19/2016] [Accepted: 07/09/2016] [Indexed: 11/24/2022] Open
Abstract
Here, we uncover a mechanism for regulating the number of active presynaptic GABAB receptors (GABABRs) at nerve terminals, an important determinant of neurotransmitter release. We find that GABABRs gain access to axon terminals by lateral diffusion in the membrane. Their relative accumulation is dependent upon agonist activation and the presence of the two distinct sushi domains that are found only in alternatively spliced GABABR1a subunits. Following brief activation of NMDA receptors (NMDARs) using glutamate, GABABR diffusion is reduced, causing accumulation at presynaptic terminals in a Ca(2+)-dependent manner that involves phosphorylation of GABABR2 subunits at Ser783. This signaling cascade indicates how synaptically released glutamate can initiate, via a feedback mechanism, increased levels of presynaptic GABABRs that limit further glutamate release and excitotoxicity.
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Affiliation(s)
- Saad Hannan
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Kim Gerrow
- Biologie Cellulaire de la Synapse, Inserm U1024, Institute of Biology, École Normale Supérieure (ENS), 46 rue d'Ulm, Paris 75005, France
| | - Antoine Triller
- Biologie Cellulaire de la Synapse, Inserm U1024, Institute of Biology, École Normale Supérieure (ENS), 46 rue d'Ulm, Paris 75005, France
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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Li J, Ye C, Mansmann UR. Comparing Patient-Derived Xenograft and Computational Response Prediction for Targeted Therapy in Patients of Early-Stage Large Cell Lung Cancer. Clin Cancer Res 2016; 22:2167-76. [PMID: 26637276 DOI: 10.1158/1078-0432.ccr-15-2401] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 11/17/2015] [Indexed: 11/16/2022]
Abstract
PURPOSE Targeted therapy (TT) provides highly effective cancer treatment for appropriately selected individuals. A major challenge of TT is to select patients who would benefit most. EXPERIMENTAL DESIGN The study uses cancer material from 25 patients primarily diagnosed with non-small cell lung cancer (NSCLC). Patient-derived xenografts (PDXs) are treated with cetuximab and erlotinib. Treatment response is measured by tumor shrinkage comparing tumor volume at day 25 (V25) with tumor volume at baseline (V0). Shrinkage below 40% is considered as treatment response: V25/V0 < 0.4 (<40%). Furthermore, RNA-seq data from each tumor sample are used to predict tumor response to either treatment using an in silico molecular signaling map (MSM) approach. RESULTS PDX response was 40% (10/25; 95% CI [21.13%, 61.34%]) under cetuximab and 20% (5/25; 95% CI [6.83%, 40.70%]) under erlotinib. MSM predicted response was 48% (12/25; 95% CI [27.8%, 68.7%]) under cetuximab and 40% (10/25; 95% CI [21.13%, 61.34%]) under erlotinib. Agreement between PDX and MSM response prediction is substantial under cetuximab and erlotinib: 84% (21/25, P = 0.001) and 80% (20/25, P = 0.003). A total of 5 from the 25 patients have been treated with cetuximab showing a clinical response identical to both predictions. CONCLUSIONS For NSCLC patients, this proof-of-concept study shows a considerable agreement in response prediction from MSM and PDX approaches, but MSM saves time and laboratory resources. Our result indicates the potential of MSM-based approach for clinical decision making when selecting cancer TTs. Clin Cancer Res; 22(9); 2167-76. ©2015 AACR.
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Affiliation(s)
- Jian Li
- Institute for Medical Informatics, Biometry and Epidemiology, Ludwig-Maximilians-Universität München, Munich, Germany. German Cancer Consortium (DKTK), Heidelberg, Germany. German Cancer Research Center (DKFZ), Heidelberg, Germany.
| | - Changkun Ye
- Medical Research Center of Yu Huang Hospital, Yu Huang, Zhejiang, PR China
| | - Ulrich R Mansmann
- Institute for Medical Informatics, Biometry and Epidemiology, Ludwig-Maximilians-Universität München, Munich, Germany. German Cancer Consortium (DKTK), Heidelberg, Germany
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Lahaie N, Kralikova M, Prézeau L, Blahos J, Bouvier M. Post-endocytotic Deubiquitination and Degradation of the Metabotropic γ-Aminobutyric Acid Receptor by the Ubiquitin-specific Protease 14. J Biol Chem 2016; 291:7156-70. [PMID: 26817839 DOI: 10.1074/jbc.m115.686907] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2015] [Indexed: 02/01/2023] Open
Abstract
Mechanisms controlling the metabotropic γ-aminobutyric acid receptor (GABAB) cell surface stability are still poorly understood. In contrast with many other G protein-coupled receptors (GPCR), it is not subject to agonist-promoted internalization, but is constitutively internalized and rapidly down-regulated. In search of novel interacting proteins regulating receptor fate, we report that the ubiquitin-specific protease 14 (USP14) interacts with the GABAB(1b)subunit's second intracellular loop. Probing the receptor for ubiquitination using bioluminescence resonance energy transfer (BRET), we detected a constitutive and phorbol 12-myristate 13-acetate (PMA)-induced ubiquitination of the receptor at the cell surface. PMA also increased internalization and accelerated receptor degradation. Overexpression of USP14 decreased ubiquitination while treatment with a small molecule inhibitor of the deubiquitinase (IU1) increased receptor ubiquitination. Treatment with the internalization inhibitor Dynasore blunted both USP14 and IU1 effects on the receptor ubiquitination state, suggesting a post-endocytic site of action. Overexpression of USP14 also led to an accelerated degradation of GABABin a catalytically independent fashion. We thus propose a model whereby cell surface ubiquitination precedes endocytosis, after which USP14 acts as an ubiquitin-binding protein that targets the ubiquitinated receptor to lysosomal degradation and promotes its deubiquitination.
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Affiliation(s)
- Nicolas Lahaie
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada
| | - Michaela Kralikova
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Laurent Prézeau
- Institut de Génomique Fonctionnelle, Université de Montpellier 1 and 2, 34090 Montpellier, France
| | - Jaroslav Blahos
- Institute of Molecular Genetics, Academy of Science of the Czech Republic, 14220 Prague 4, Czech Republic, and
| | - Michel Bouvier
- From the Department of Biochemistry and Institute for Research in Immunology and Cancer, Université de Montréal, Montréal, Quebec H3T 1J4, Canada,
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Role of GABA(B) receptors in learning and memory and neurological disorders. Neurosci Biobehav Rev 2016; 63:1-28. [PMID: 26814961 DOI: 10.1016/j.neubiorev.2016.01.007] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/31/2015] [Accepted: 01/21/2016] [Indexed: 01/13/2023]
Abstract
Although it is evident from the literature that altered GABAB receptor function does affect behavior, these results often do not correspond well. These differences could be due to the task protocol, animal strain, ligand concentration, or timing of administration utilized. Because several clinical populations exhibit learning and memory deficits in addition to altered markers of GABA and the GABAB receptor, it is important to determine whether altered GABAB receptor function is capable of contributing to the deficits. The aim of this review is to examine the effect of altered GABAB receptor function on synaptic plasticity as demonstrated by in vitro data, as well as the effects on performance in learning and memory tasks. Finally, data regarding altered GABA and GABAB receptor markers within clinical populations will be reviewed. Together, the data agree that proper functioning of GABAB receptors is crucial for numerous learning and memory tasks and that targeting this system via pharmaceuticals may benefit several clinical populations.
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Falsafi SK, Ghafari M, Miklósi AG, Engidawork E, Gröger M, Höger H, Lubec G. Mouse hippocampal GABAB1 but not GABAB2 subunit-containing receptor complex levels are paralleling retrieval in the multiple-T-maze. Front Behav Neurosci 2015; 9:276. [PMID: 26539091 PMCID: PMC4609755 DOI: 10.3389/fnbeh.2015.00276] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 09/28/2015] [Indexed: 11/13/2022] Open
Abstract
GABAB receptors are heterodimeric G-protein coupled receptors known to be involved in learning and memory. Although a role for GABAB receptors in cognitive processes is evident, there is no information on hippocampal GABAB receptor complexes in a multiple T maze (MTM) task, a robust paradigm for evaluation of spatial learning. Trained or untrained (yoked control) C57BL/6J male mice (n = 10/group) were subjected to the MTM task and sacrificed 6 h following their performance. Hippocampi were taken, membrane proteins extracted and run on blue native PAGE followed by immunoblotting with specific antibodies against GABAB1, GABAB1a, and GABAB2. Immunoprecipitation with subsequent mass spectrometric identification of co-precipitates was carried out to show if GABAB1 and GABAB2 as well as other interacting proteins co-precipitate. An antibody shift assay (ASA) and a proximity ligation assay (PLA) were also used to see if the two GABAB subunits are present in the receptor complex. Single bands were observed on Western blots, each representing GABAB1, GABAB1a, or GABAB2 at an apparent molecular weight of approximately 100 kDa. Subsequently, densitometric analysis revealed that levels of GABAB1 and GABAB1a but not GABAB2- containing receptor complexes were significantly higher in trained than untrained groups. Immunoprecipitation followed by mass spectrometric studies confirmed the presence of GABAB1, GABAB2, calcium calmodulin kinases I and II, GluA1 and GluA2 as constituents of the complex. ASA and PLA also showed the presence of the two subunits of GABAB receptor within the complex. It is shown that increased levels of GABAB1 subunit-containing complexes are paralleling performance in a land maze.
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Affiliation(s)
- Soheil K Falsafi
- Department of Pediatrics, Medical University of Vienna Vienna, Austria
| | - Maryam Ghafari
- Department of Pediatrics, Medical University of Vienna Vienna, Austria
| | - András G Miklósi
- Department of Pediatrics, Medical University of Vienna Vienna, Austria
| | - Ephrem Engidawork
- Department of Pharmacology and Clinical Pharmacy, School of Pharmacy, College of Health Sciences, Addis Ababa University Addis Ababa, Ethiopia
| | - Marion Gröger
- Skin and Endothelium Research Division, Department of Dermatology, Medical University Vienna, Austria
| | - Harald Höger
- Core Unit of Biomedical Research, Division of Laboratory Animal Science and Genetics, Medical University of Vienna Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna Vienna, Austria
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Zhang Z, Zhang W, Huang S, Sun Q, Wang Y, Hu Y, Sun N, Zhang Y, Jiang Z, Minato N, Pin JP, Su L, Liu J. GABAB receptor promotes its own surface expression by recruiting a Rap1-dependent signaling cascade. J Cell Sci 2015; 128:2302-13. [DOI: 10.1242/jcs.167056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 05/05/2015] [Indexed: 12/11/2022] Open
Abstract
ABSTRACT
G-protein-coupled receptors (GPCRs) are key players in cell signaling, and their cell surface expression is tightly regulated. For many GPCRs such as β2-AR (β2-adrenergic receptor), receptor activation leads to downregulation of receptor surface expression, a phenomenon that has been extensively characterized. By contrast, some other GPCRs, such as GABAB receptor, remain relatively stable at the cell surface even after prolonged agonist treatment; however, the underlying mechanisms are unclear. Here, we identify the small GTPase Rap1 as a key regulator for promoting GABAB receptor surface expression. Agonist stimulation of GABAB receptor signals through Gαi/o to inhibit Rap1GAPII (also known as Rap1GAP1b, an isoform of Rap1GAP1), thereby activating Rap1 (which has two isoforms, Rap1a and Rap1b) in cultured cerebellar granule neurons (CGNs). The active form of Rap1 is then recruited to GABAB receptor through physical interactions in CGNs. This Rap1-dependent signaling cascade promotes GABAB receptor surface expression by stimulating receptor recycling. Our results uncover a new mechanism regulating GPCR surface expression and also provide a potential explanation for the slow, long-lasting inhibitory action of GABA neurotransmitter.
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Affiliation(s)
- Zongyong Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Wenhua Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Siluo Huang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qian Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yunyun Wang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yongjian Hu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Ninghua Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yilei Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhihua Jiang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Nagahiro Minato
- Department of Immunology and Cell Biology, Kyoto University, Kyoto 606-8501, Japan
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université Montpellier 1 et 2, Montpellier cedex 5 34094, France
| | - Li Su
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
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26
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Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors. Eur J Pharmacol 2015; 763:233-40. [PMID: 25981296 DOI: 10.1016/j.ejphar.2015.05.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 03/06/2015] [Accepted: 05/11/2015] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors are divided into three classes (A, B and C) based on homology of their seven transmembrane domains. Class C is the smallest class with 22 human receptor subtypes including eight metabotropic glutamate (mGlu1-8) receptors, two GABAB receptors (GABAB1 and GABAB2), three taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we review the existence of post-translational modifications in class C G protein-coupled receptors and their regulatory roles, with particular focus on glycosylation, phosphorylation, ubiquitination, SUMOylation, disulphide bonding and lipidation.
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Raveh A, Turecek R, Bettler B. Mechanisms of fast desensitization of GABA(B) receptor-gated currents. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 73:145-65. [PMID: 25637440 DOI: 10.1016/bs.apha.2014.11.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors (GABA(B)Rs) regulate the excitability of most neurons in the central nervous system by modulating the activity of enzymes and ion channels. In the sustained presence of the neurotransmitter γ-aminobutyric acid, GABA(B)Rs exhibit a time-dependent decrease in the receptor response-a phenomenon referred to as homologous desensitization. Desensitization prevents excessive receptor influences on neuronal activity. Much work focused on the mechanisms of GABA(B)R desensitization that operate at the receptor and control receptor expression at the plasma membrane. Over the past few years, it became apparent that GABA(B)Rs additionally evolved mechanisms for faster desensitization. These mechanisms operate at the G protein rather than at the receptor and inhibit G protein signaling within seconds of agonist exposure. The mechanisms for fast desensitization are ideally suited to regulate receptor-activated ion channel responses, which influence neuronal activity on a faster timescale than effector enzymes. Here, we provide an update on the mechanisms for fast desensitization of GABA(B)R responses and discuss physiological and pathophysiological implications.
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Affiliation(s)
- Adi Raveh
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland; Department of Auditory Neuroscience, Institute of Experimental Medicine, ASCR, Prague, Czech Republic
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland.
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Benke D, Balakrishnan K, Zemoura K. Regulation of Cell Surface GABAB Receptors. DIVERSITY AND FUNCTIONS OF GABA RECEPTORS: A TRIBUTE TO HANNS MÖHLER, PART B 2015; 73:41-70. [DOI: 10.1016/bs.apha.2014.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Rajalu M, Fritzius T, Adelfinger L, Jacquier V, Besseyrias V, Gassmann M, Bettler B. Pharmacological characterization of GABAB receptor subtypes assembled with auxiliary KCTD subunits. Neuropharmacology 2015; 88:145-54. [DOI: 10.1016/j.neuropharm.2014.08.020] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 08/14/2014] [Accepted: 08/23/2014] [Indexed: 01/23/2023]
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30
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Adelfinger L, Turecek R, Ivankova K, Jensen AA, Moss SJ, Gassmann M, Bettler B. GABAB receptor phosphorylation regulates KCTD12-induced K⁺ current desensitization. Biochem Pharmacol 2014; 91:369-79. [PMID: 25065880 PMCID: PMC4402209 DOI: 10.1016/j.bcp.2014.07.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 01/08/2023]
Abstract
GABAB receptors assemble from GABAB1 and GABAB2 subunits. GABAB2 additionally associates with auxiliary KCTD subunits (named after their K(+) channel tetramerization-domain). GABAB receptors couple to heterotrimeric G-proteins and activate inwardly-rectifying K(+) channels through the βγ subunits released from the G-protein. Receptor-activated K(+) currents desensitize in the sustained presence of agonist to avoid excessive effects on neuronal activity. Desensitization of K(+) currents integrates distinct mechanistic underpinnings. GABAB receptor activity reduces protein kinase-A activity, which reduces phosphorylation of serine-892 in GABAB2 and promotes receptor degradation. This form of desensitization operates on the time scale of several minutes to hours. A faster form of desensitization is induced by the auxiliary subunit KCTD12, which interferes with channel activation by binding to the G-protein βγ subunits. Here we show that the two mechanisms of desensitization influence each other. Serine-892 phosphorylation in heterologous cells rearranges KCTD12 at the receptor and slows KCTD12-induced desensitization. Likewise, protein kinase-A activation in hippocampal neurons slows fast desensitization of GABAB receptor-activated K(+) currents while protein kinase-A inhibition accelerates fast desensitization. Protein kinase-A fails to regulate fast desensitization in KCTD12 knock-out mice or knock-in mice with a serine-892 to alanine mutation, thus demonstrating that serine-892 phosphorylation regulates KCTD12-induced desensitization in vivo. Fast current desensitization is accelerated in hippocampal neurons carrying the serine-892 to alanine mutation, showing that tonic serine-892 phosphorylation normally limits KCTD12-induced desensitization. Tonic serine-892 phosphorylation is in turn promoted by assembly of receptors with KCTD12. This cross-regulation of serine-892 phosphorylation and KCTD12 activity sharpens the response during repeated receptor activation.
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Affiliation(s)
- Lisa Adelfinger
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland; Institute of Experimental Medicine, ASCR, Videnska 1083, 14220 Prague 4-Krc, Czech Republic
| | - Klara Ivankova
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | - Anders A Jensen
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Martin Gassmann
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
| | - Bernhard Bettler
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland.
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31
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Terunuma M, Haydon PG, Pangalos MN, Moss SJ. Purinergic receptor activation facilitates astrocytic GABAB receptor calcium signalling. Neuropharmacology 2014; 88:74-81. [PMID: 25261019 DOI: 10.1016/j.neuropharm.2014.09.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/04/2014] [Accepted: 09/06/2014] [Indexed: 12/11/2022]
Abstract
Gamma-aminobutyric acid B receptors (GABABRs) are heterodimeric G-protein coupled receptors, which mediate slow synaptic inhibition in the brain. Emerging evidence suggests astrocytes also express GABABRs, although their physiological significance remains unknown. To begin addressing this issue, we have used imaging and biochemical analysis to examine the role GABABRs play in regulating astrocytic Ca(2+) signalling. Using live imaging of cultured cortical astrocytes loaded with calcium indicator Fluo-4/AM, we found that astrocytic GABABRs are able to induce astrocytic calcium transients only if they are pre-activated by P2 purinoceptors (P2YRs). The GABABR-mediated calcium transients were attenuated by the removal of extracellular calcium. Furthermore, P2YRs enhance the phosphorylation of astrocytic GABABR R2 subunits on both serine 783 (S783) and serine 892 (S892), two phosphorylation sites that are well known to regulate the activity and the cell surface stability of GABABRs. Collectively these results suggest that P2YR mediated signalling is an important determinant of GABABR activity and phosphorylation in astrocytes.
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Affiliation(s)
- Miho Terunuma
- Department of Cell Physiology and Pharmacology, College of Medicine, Biological Sciences and Psychology, University of Leicester, University Road, Leicester LE1 9HN, UK.
| | - Philip G Haydon
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA
| | - Menelas N Pangalos
- Innovative Medicines, AstraZeneca, Mereside, Alderley Park, Cheshire SK10 4TG, UK
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA 02111, USA; Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
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32
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Blankenburg S, Balfanz S, Hayashi Y, Shigenobu S, Miura T, Baumann O, Baumann A, Blenau W. Cockroach GABAB receptor subtypes: molecular characterization, pharmacological properties and tissue distribution. Neuropharmacology 2014; 88:134-44. [PMID: 25242738 DOI: 10.1016/j.neuropharm.2014.08.022] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Revised: 08/10/2014] [Accepted: 08/23/2014] [Indexed: 11/29/2022]
Abstract
γ-aminobutyric acid (GABA) is the predominant inhibitory neurotransmitter in the central nervous system (CNS). Its effects are mediated by either ionotropic GABAA receptors or metabotropic GABAB receptors. GABAB receptors regulate, via Gi/o G-proteins, ion channels, and adenylyl cyclases. In humans, GABAB receptor subtypes are involved in the etiology of neurologic and psychiatric disorders. In arthropods, however, these members of the G-protein-coupled receptor family are only inadequately characterized. Interestingly, physiological data have revealed important functions of GABAB receptors in the American cockroach, Periplaneta americana. We have cloned cDNAs coding for putative GABAB receptor subtypes 1 and 2 of P. americana (PeaGB1 and PeaGB2). When both receptor proteins are co-expressed in mammalian cells, activation of the receptor heteromer with GABA leads to a dose-dependent decrease in cAMP production. The pharmacological profile differs from that of mammalian and Drosophila GABAB receptors. Western blot analyses with polyclonal antibodies have revealed the expression of PeaGB1 and PeaGB2 in the CNS of the American cockroach. In addition to the widespread distribution in the brain, PeaGB1 is expressed in salivary glands and male accessory glands. Notably, PeaGB1-like immunoreactivity has been detected in the GABAergic salivary neuron 2, suggesting that GABAB receptors act as autoreceptors in this neuron.
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Affiliation(s)
- S Blankenburg
- Institute of Biochemistry and Biology, Department of Animal Physiology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany.
| | - S Balfanz
- Institute of Complex Systems, Zelluläre Biophysik (ICS-4), Research Center Jülich, Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - Y Hayashi
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.
| | - S Shigenobu
- NIBB Core Research Facilities, National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, 444-8585, Japan.
| | - T Miura
- Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan.
| | - O Baumann
- Institute of Biochemistry and Biology, Department of Animal Physiology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany.
| | - A Baumann
- Institute of Complex Systems, Zelluläre Biophysik (ICS-4), Research Center Jülich, Forschungszentrum Jülich, 52425, Jülich, Germany.
| | - W Blenau
- Institut für Bienenkunde, Polytechnische Gesellschaft, Goethe-Universität Frankfurt am Main, FB Biowissenschaften, Karl-von-Frisch-Weg 2, 61440, Oberursel, Germany.
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Huyghe D, Nakamura Y, Terunuma M, Faideau M, Haydon P, Pangalos MN, Moss SJ. Glutamine synthetase stability and subcellular distribution in astrocytes are regulated by γ-aminobutyric type B receptors. J Biol Chem 2014; 289:28808-15. [PMID: 25172509 DOI: 10.1074/jbc.m114.583534] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Emerging evidence suggests that functional γ-aminobutyric acid B receptors (GABABRs) are expressed by astrocytes within the mammalian brain. GABABRs are heterodimeric G-protein-coupled receptors that are composed of R1/R2 subunits. To date, they have been characterized in neurons as the principal mediators of sustained inhibitory signaling; however their roles in astrocytic physiology have been ill defined. Here we reveal that the cytoplasmic tail of the GABABR2 subunit binds directly to the astrocytic protein glutamine synthetase (GS) and that this interaction determines the subcellular localization of GS. We further demonstrate that the binding of GS to GABABR2 increases the steady state expression levels of GS in heterologous cells and in mouse primary astrocyte culture. Mechanistically this increased stability of GS in the presence of GABABR2 occurs via reduced proteasomal degradation. Collectively, our results suggest a novel role for GABABRs as regulators of GS stability. Given the critical role that GS plays in the glutamine-glutamate cycle, astrocytic GABABRs may play a critical role in supporting both inhibitory and excitatory neurotransmission.
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Affiliation(s)
- Deborah Huyghe
- From the Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Yasuko Nakamura
- From the Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Miho Terunuma
- Department of Cell Physiology and Pharmacology, College of Medicine, Biological Sciences and Psychology, University of Leicester, University Road, Leicester LE1 9HN, United Kingdom
| | - Mathilde Faideau
- Department of Experimental Dementia Research, Lund University SE-221 00 Lund, Sweden
| | - Philip Haydon
- From the Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Menelas N Pangalos
- Innovative Medicines, AstraZeneca, Mereside, Alderley Park, Cheshire SK10 4TF, United Kingdom, and
| | - Stephen J Moss
- From the Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts 02111, Department of Neuroscience, Physiology & Pharmacology, University College London, London WC1E 6B, United Kingdom
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Valenzuela JI, Jaureguiberry-Bravo M, Salas DA, Ramírez OA, Cornejo VH, Lu HE, Blanpied TA, Couve A. Transport along the dendritic endoplasmic reticulum mediates the trafficking of GABAB receptors. J Cell Sci 2014; 127:3382-95. [PMID: 24895402 DOI: 10.1242/jcs.151092] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In neurons, secretory organelles within the cell body are complemented by the dendritic endoplasmic reticulum (ER) and Golgi outposts (GOPs), whose role in neurotransmitter receptor trafficking is poorly understood. γ-aminobutyric acid (GABA) type B metabotropic receptors (GABABRs) regulate the efficacy of synaptic transmission throughout the brain. Their plasma membrane availability is controlled by mechanisms involving an ER retention motif and assembly-dependent ER export. Thus, they constitute an ideal molecular model to study ER trafficking, but the extent to which the dendritic ER participates in GABABR biosynthesis has not been thoroughly explored. Here, we show that GABAB1 localizes preferentially to the ER in dendrites and moves long distances within this compartment. Not only diffusion but also microtubule and dynein-dependent mechanisms control dendritic ER transport. GABABRs insert throughout the somatodendritic plasma membrane but dendritic post-ER carriers containing GABABRs do not fuse selectively with GOPs. This study furthers our understanding of the spatial selectivity of neurotransmitter receptors for dendritic organelles.
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Affiliation(s)
- José I Valenzuela
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
| | - Matías Jaureguiberry-Bravo
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
| | - Daniela A Salas
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
| | - Omar A Ramírez
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Program of Anatomy and Development, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
| | - Víctor H Cornejo
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
| | - Hsiangmin E Lu
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA Program in Molecular Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Thomas A Blanpied
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA Program in Neuroscience, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Andrés Couve
- Program of Physiology and Biophysics, ICBM, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile Biomedical Neuroscience Institute, BNI, Faculty of Medicine, Universidad de Chile, Santiago CP8380453, Chile
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Auxiliary GABAB Receptor Subunits Uncouple G Protein βγ Subunits from Effector Channels to Induce Desensitization. Neuron 2014; 82:1032-44. [DOI: 10.1016/j.neuron.2014.04.015] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/01/2014] [Indexed: 01/07/2023]
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Postsynaptic GABAB receptor activity regulates excitatory neuronal architecture and spatial memory. J Neurosci 2014; 34:804-16. [PMID: 24431439 DOI: 10.1523/jneurosci.3320-13.2013] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cognitive dysfunction is a common symptom in many neuropsychiatric disorders and directly correlates with poor patient outcomes. The majority of prolonged inhibitory signaling in the brain is mediated via GABAB receptors (GABABRs), but the molecular function of these receptors in cognition is ill defined. To explore the significance of GABABRs in neuronal activity and cognition, we created mice with enhanced postsynaptic GABABR signaling by mutating the serine 783 in receptor R2 subunit (S783A), which decreased GABABR degradation. Enhanced GABABR activity reduced the expression of immediate-early gene-encoded protein Arc/Arg3.1, effectors that are critical for long-lasting memory. Intriguingly, S783A mice exhibited increased numbers of excitatory synapses and surface AMPA receptors, effects that are consistent with decreased Arc/Arg3.1 expression. These deficits in Arc/Arg3.1 and neuronal morphology lead to a deficit in spatial memory consolidation. Collectively our results suggest a novel and unappreciated role for GABABR activity in determining excitatory neuronal architecture and spatial memory via their ability to regulate Arc/Arg3.1.
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Xu C, Zhang W, Rondard P, Pin JP, Liu J. Complex GABAB receptor complexes: how to generate multiple functionally distinct units from a single receptor. Front Pharmacol 2014; 5:12. [PMID: 24575041 PMCID: PMC3920572 DOI: 10.3389/fphar.2014.00012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 01/22/2014] [Indexed: 01/05/2023] Open
Abstract
The main inhibitory neurotransmitter, GABA, acts on both ligand-gated and G protein-coupled receptors, the GABAA/C and GABAB receptors, respectively. The later play important roles in modulating many synapses, both at the pre- and post-synaptic levels, and are then still considered as interesting targets to treat a number of brain diseases, including addiction. For many years, several subtypes of GABAB receptors were expected, but cloning revealed only two genes that work in concert to generate a single type of GABAB receptor composed of two subunits. Here we will show that the signaling complexity of this unit receptor type can be largely increased through various ways, including receptor stoichiometry, subunit isoforms, cell-surface expression and localization, crosstalk with other receptors, or interacting proteins. These recent data revealed how complexity of a receptor unit can be increased, observation that certainly are not unique to the GABAB receptor.
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Affiliation(s)
- Chanjuan Xu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
| | - Wenhua Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
| | - Philippe Rondard
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Universités de Montpellier I & II Montpellier, France
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Universités de Montpellier I & II Montpellier, France
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology Wuhan, China
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Dephosphorylation of endogenous GABA(B) receptor R2 subunit and AMPK α subunits which were measured by in vitro method using transfer membrane. Neurochem Int 2012; 62:137-44. [PMID: 23238131 DOI: 10.1016/j.neuint.2012.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 11/17/2012] [Accepted: 12/05/2012] [Indexed: 01/19/2023]
Abstract
Protein phosphorylation can be regulated by changes in kinase activity, phosphatase activity, or both. GABA(B) receptor R2 subunit (GABA(B)R2) is phosphorylated at S783 by 5'-AMP-activated-protein kinase (AMPK), and this phosphorylation modulates GABA(B) receptor desensitization. Since the GABA(B) receptor is an integral membrane protein, solubilizing GABA(B)R2 is difficult. To circumvent this problem and to identify specific phosphatases that dephosphorylate S783, we employed an in vitro assay based on dephosphorylation of proteins on PVDF membranes by purified phosphatases. Our method allowed us to demonstrate that S783 in GABA(B)R2 is directly dephosphorylated by PP2A (but not by PP1, PP2B nor PP2C) in a dose-dependent and okadaic acid-sensitive manner. We also show that the level of phosphorylation of the catalytic subunit of AMPK at T172 is reduced by PP1, PP2A and PP2C. Our data indicate that PP2A dephosphorylates GABA(B)R2(S783) less efficiently than AMPK(T172), and that additional phosphatases might be involved in S783 dephosphorylation.
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Seddik R, Jungblut SP, Silander OK, Rajalu M, Fritzius T, Besseyrias V, Jacquier V, Fakler B, Gassmann M, Bettler B. Opposite effects of KCTD subunit domains on GABA(B) receptor-mediated desensitization. J Biol Chem 2012; 287:39869-77. [PMID: 23035119 DOI: 10.1074/jbc.m112.412767] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GABA(B) receptors assemble from principle and auxiliary subunits. The principle subunits GABA(B1) and GABA(B2) form functional heteromeric GABA(B(1,2)) receptors that associate with homotetramers of auxiliary KCTD8, -12, -12b, or -16 (named after their K(+) channel tetramerization domain) subunits. These auxiliary subunits constitute receptor subtypes with distinct functional properties. KCTD12 and -12b generate desensitizing receptor responses while KCTD8 and -16 generate largely non-desensitizing receptor responses. The structural elements of the KCTDs underlying these differences in desensitization are unknown. KCTDs are modular proteins comprising a T1 tetramerization domain, which binds to GABA(B2), and a H1 homology domain. KCTD8 and -16 contain an additional C-terminal H2 homology domain that is not sequence-related to the H1 domains. No functions are known for the H1 and H2 domains. Here we addressed which domains and sequence motifs in KCTD proteins regulate desensitization of the receptor response. We found that the H1 domains in KCTD12 and -12b mediate desensitization through a particular sequence motif, T/NFLEQ, which is not present in the H1 domains of KCTD8 and -16. In addition, the H2 domains in KCTD8 and -16 inhibit desensitization when expressed C-terminal to the H1 domains but not when expressed as a separate protein in trans. Intriguingly, the inhibitory effect of the H2 domain is sequence-independent, suggesting that the H2 domain sterically hinders desensitization by the H1 domain. Evolutionary analysis supports that KCTD12 and -12b evolved desensitizing properties by liberating their H1 domains from antagonistic H2 domains and acquisition of the T/NFLEQ motif.
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Affiliation(s)
- Riad Seddik
- Department of Biomedicine, University of Basel, 4056 Basel, Switzerland
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Valdés V, Valenzuela JI, Salas DA, Jaureguiberry-Bravo M, Otero C, Thiede C, Schmidt CF, Couve A. Endoplasmic reticulum sorting and kinesin-1 command the targeting of axonal GABAB receptors. PLoS One 2012; 7:e44168. [PMID: 22952914 PMCID: PMC3428321 DOI: 10.1371/journal.pone.0044168] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Accepted: 07/30/2012] [Indexed: 12/17/2022] Open
Abstract
In neuronal cells the intracellular trafficking machinery controls the availability of neurotransmitter receptors at the plasma membrane, which is a critical determinant of synaptic strength. Metabotropic γ amino-butyric acid (GABA) type B receptors (GABABRs) are neurotransmitter receptors that modulate synaptic transmission by mediating the slow and prolonged responses to GABA. GABABRs are obligatory heteromers constituted by two subunits, GABABR1 and GABABR2. GABABR1a and GABABR1b are the most abundant subunit variants. GABABR1b is located in the somatodendritic domain whereas GABABR1a is additionally targeted to the axon. Sushi domains located at the N-terminus of GABABR1a constitute the only difference between both variants and are necessary and sufficient for axonal targeting. The precise targeting machinery and the organelles involved in sorting and transport have not been described. Here we demonstrate that GABABRs require the Golgi apparatus for plasma membrane delivery but that axonal sorting and targeting of GABABR1a operate in a pre-Golgi compartment. In the axon GABABR1a subunits are enriched in the endoplasmic reticulum (ER), and their dynamic behavior and colocalization with other secretory organelles like the ER-to-Golgi intermediate compartment (ERGIC) suggest that they employ a local secretory route. The transport of axonal GABABR1a is microtubule-dependent and kinesin-1, a molecular motor of the kinesin family, determines axonal localization. Considering that progression of GABABRs through the secretory pathway is regulated by an ER retention motif our data contribute to understand the role of the axonal ER in non-canonical sorting and targeting of neurotransmitter receptors.
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Affiliation(s)
- Viviana Valdés
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - José Ignacio Valenzuela
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Daniela A. Salas
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Matías Jaureguiberry-Bravo
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- School of Biochemistry, Faculty of Biological Science, Universidad Andrés Bello, Santiago, Chile
| | - Carolina Otero
- Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Christina Thiede
- Georg-August-Universität, Fakultät für Physik, Drittes Physikalisches Institut-Biophysik, Göttingen, Germany
| | - Christoph F. Schmidt
- Georg-August-Universität, Fakultät für Physik, Drittes Physikalisches Institut-Biophysik, Göttingen, Germany
| | - Andrés Couve
- Biomedical Neuroscience Institute (BNI), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
- * E-mail:
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Presynaptic GABA(B) receptors decrease neurotransmitter release in vestibular nuclei neurons during vestibular compensation. Neuroscience 2012; 223:333-54. [PMID: 22871524 DOI: 10.1016/j.neuroscience.2012.07.061] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/18/2012] [Accepted: 07/30/2012] [Indexed: 01/25/2023]
Abstract
Unilateral damage to the peripheral vestibular receptors precipitates a debilitating syndrome of oculomotor and balance deficits at rest, which extensively normalize during the first week after the lesion due to vestibular compensation. In vivo studies suggest that GABA(B) receptor activation facilitates recovery. However, the presynaptic or postsynaptic sites of action of GABA(B) receptors in vestibular nuclei neurons after lesions have not been determined. Accordingly, here presynaptic and postsynaptic GABA(B) receptor activity in principal cells of the tangential nucleus, a major avian vestibular nucleus, was investigated using patch-clamp recordings correlated with immunolabeling and confocal imaging of the GABA(B) receptor subunit-2 (GABA(B)R2) in controls and operated chickens shortly after unilateral vestibular ganglionectomy (UVG). Baclofen, a GABA(B) agonist, generated no postsynaptic currents in principal cells in controls, which correlated with weak GABA(B)R2 immunolabeling on principal cell surfaces. However, baclofen decreased miniature excitatory postsynaptic current (mEPSC) and GABAergic miniature inhibitory postsynaptic current (mIPSC) events in principal cells in controls, compensating and uncompensated chickens three days after UVG, indicating the presence of functional GABA(B) receptors on presynaptic terminals. Baclofen decreased GABAergic mIPSC frequency to the greatest extent in principal cells on the intact side of compensating chickens, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 2-labeled terminals. In uncompensated chickens, baclofen decreased mEPSC frequency to the greatest extent in principal cells on the intact side, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 1-labeled terminals. Altogether, these results revealed changes in presynaptic GABA(B) receptor function and expression which differed in compensating and uncompensated chickens shortly after UVG. This work supports an important role for GABA(B) autoreceptor-mediated inhibition in vestibular nuclei neurons on the intact side during early stages of vestibular compensation, and a role for GABA(B) heteroreceptor-mediated inhibition of glutamatergic terminals on the intact side in the failure to recover function.
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Abstract
A growing body of evidence is now connecting neuroendocrine mediators of the stress response to cancer biology. Al-Wadei and colleagues report a study in this issue of the journal (beginning on page 189) that provides a new piece of this evidence, adding the inhibitory neurotransmitter γ-aminobutyric acid to this intricate pathway. Their mouse model study supports the hypothesis that stress mediators contribute to lung cancer progression and that known inhibitors of the stress pathway might block such effects, thus adding to the impetus for studying cancer prevention strategies targeting the stress pathway.
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Gassmann M, Bettler B. Regulation of neuronal GABA(B) receptor functions by subunit composition. Nat Rev Neurosci 2012; 13:380-94. [PMID: 22595784 DOI: 10.1038/nrn3249] [Citation(s) in RCA: 248] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
GABA(B) receptors (GABA(B)Rs) are G protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the CNS. In the past 5 years, notable advances have been made in our understanding of the molecular composition of these receptors. GABA(B)Rs are now known to comprise principal and auxiliary subunits that influence receptor properties in distinct ways. The principal subunits regulate the surface expression and the axonal versus dendritic distribution of these receptors, whereas the auxiliary subunits determine agonist potency and the kinetics of the receptor response. This Review summarizes current knowledge on how the subunit composition of GABA(B)Rs affects the distribution of these receptors, neuronal processes and higher brain functions.
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Affiliation(s)
- Martin Gassmann
- Department of Biomedicine, Institute of Physiology, University of Basel, Klingelbergstr. 50-70, 4056 Basel, Switzerland.
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Padgett CL, Lalive AL, Tan KR, Terunuma M, Munoz MB, Pangalos MN, Martínez-Hernández J, Watanabe M, Moss SJ, Luján R, Lüscher C, Slesinger PA. Methamphetamine-evoked depression of GABA(B) receptor signaling in GABA neurons of the VTA. Neuron 2012; 73:978-89. [PMID: 22405207 DOI: 10.1016/j.neuron.2011.12.031] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2011] [Indexed: 01/06/2023]
Abstract
Psychostimulants induce neuroadaptations in excitatory and fast inhibitory transmission in the ventral tegmental area (VTA). Mechanisms underlying drug-evoked synaptic plasticity of slow inhibitory transmission mediated by GABA(B) receptors and G protein-gated inwardly rectifying potassium (GIRK/Kir(3)) channels, however, are poorly understood. Here, we show that 1 day after methamphetamine (METH) or cocaine exposure both synaptically evoked and baclofen-activated GABA(B)R-GIRK currents were significantly depressed in VTA GABA neurons and remained depressed for 7 days. Presynaptic inhibition mediated by GABA(B)Rs on GABA terminals was also weakened. Quantitative immunoelectron microscopy revealed internalization of GABA(B1) and GIRK2, which occurred coincident with dephosphorylation of serine 783 (S783) in GABA(B2), a site implicated in regulating GABA(B)R surface expression. Inhibition of protein phosphatases recovered GABA(B)R-GIRK currents in VTA GABA neurons of METH-injected mice. This psychostimulant-evoked impairment in GABA(B)R signaling removes an intrinsic brake on GABA neuron spiking, which may augment GABA transmission in the mesocorticolimbic system.
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Affiliation(s)
- Claire L Padgett
- Peptide Biology Laboratories, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA
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Benke D, Zemoura K, Maier PJ. Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation. World J Biol Chem 2012; 3:61-72. [PMID: 22558486 PMCID: PMC3342575 DOI: 10.4331/wjbc.v3.i4.61] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 12/08/2011] [Accepted: 12/15/2011] [Indexed: 02/05/2023] Open
Abstract
Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength.
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Affiliation(s)
- Dietmar Benke
- Dietmar Benke, Khaled Zemoura, Patrick J Maier, Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Padgett CL, Slesinger PA. GABAB receptor coupling to G-proteins and ion channels. ADVANCES IN PHARMACOLOGY 2010; 58:123-47. [PMID: 20655481 DOI: 10.1016/s1054-3589(10)58006-2] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
GABA(B) receptors have been found to play a key role in regulating membrane excitability and synaptic transmission in the brain. The GABA(B) receptor is a G-protein coupled receptor (GPCR) that associates with a subset of G-proteins (pertussis toxin sensitive Gi/o family), that in turn regulate specific ion channels and trigger cAMP cascades. In this review, we describe the relationships between the GABA(B) receptor, its effectors and associated proteins that mediate GABA(B) receptor function within the brain. We discuss a unique feature of the GABA(B) receptor, the requirement for heterodimerization to produce functional receptors, as well as an increasing body of evidence that suggests GABA(B) receptors comprise a macromolecular signaling heterocomplex, critical for efficient targeting and function of the receptors. Within this complex, GABA(B) receptors associate specifically with Gi/o G-proteins that regulate voltage-gated Ca(2+) (Ca(V)) channels, G-protein activated inwardly rectifying K(+) (GIRK) channels, and adenylyl cyclase. Numerous studies have revealed that lipid rafts, scaffold proteins, targeting motifs in the receptor, and regulators of G-protein signaling (RGS) proteins also contribute to the function of GABA(B) receptors and affect cellular processes such as receptor trafficking and activity-dependent desensitization. This complex regulation of GABA(B) receptors in the brain may provide opportunities for new ways to regulate GABA-dependent inhibition in normal and diseased states of the nervous system.
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Affiliation(s)
- Claire L Padgett
- Peptide Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, USA
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Guetg N, Aziz SA, Holbro N, Turecek R, Rose T, Seddik R, Gassmann M, Moes S, Jenoe P, Oertner TG, Casanova E, Bettler B. NMDA receptor-dependent GABAB receptor internalization via CaMKII phosphorylation of serine 867 in GABAB1. Proc Natl Acad Sci U S A 2010; 107:13924-9. [PMID: 20643921 PMCID: PMC2922270 DOI: 10.1073/pnas.1000909107] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
GABAB receptors are the G-protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the brain. GABAB receptors are abundant on dendritic spines, where they dampen postsynaptic excitability and inhibit Ca2+ influx through NMDA receptors when activated by spillover of GABA from neighboring GABAergic terminals. Here, we show that an excitatory signaling cascade enables spines to counteract this GABAB-mediated inhibition. We found that NMDA application to cultured hippocampal neurons promotes dynamin-dependent endocytosis of GABAB receptors. NMDA-dependent internalization of GABAB receptors requires activation of Ca2+/Calmodulin-dependent protein kinase II (CaMKII), which associates with GABAB receptors in vivo and phosphorylates serine 867 (S867) in the intracellular C terminus of the GABAB1 subunit. Blockade of either CaMKII or phosphorylation of S867 renders GABAB receptors refractory to NMDA-mediated internalization. Time-lapse two-photon imaging of organotypic hippocampal slices reveals that activation of NMDA receptors removes GABAB receptors within minutes from the surface of dendritic spines and shafts. NMDA-dependent S867 phosphorylation and internalization is predominantly detectable with the GABAB1b subunit isoform, which is the isoform that clusters with inhibitory effector K+ channels in the spines. Consistent with this, NMDA receptor activation in neurons impairs the ability of GABAB receptors to activate K+ channels. Thus, our data support that NMDA receptor activity endocytoses postsynaptic GABAB receptors through CaMKII-mediated phosphorylation of S867. This provides a means to spare NMDA receptors at individual glutamatergic synapses from reciprocal inhibition through GABAB receptors.
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Affiliation(s)
- Nicole Guetg
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Said Abdel Aziz
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Niklaus Holbro
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Rostislav Turecek
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
- Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic; and
| | - Tobias Rose
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Riad Seddik
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Martin Gassmann
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Suzette Moes
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Paul Jenoe
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Thomas G. Oertner
- Friedrich Miescher Institute for Biomedical Research, 4058 Basel, Switzerland
| | - Emilio Casanova
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, 4056 Basel, Switzerland
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Prolonged activation of NMDA receptors promotes dephosphorylation and alters postendocytic sorting of GABAB receptors. Proc Natl Acad Sci U S A 2010; 107:13918-23. [PMID: 20643948 DOI: 10.1073/pnas.1000853107] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Slow and persistent synaptic inhibition is mediated by metabotropic GABAB receptors (GABABRs). GABABRs are responsible for the modulation of neurotransmitter release from presynaptic terminals and for hyperpolarization at postsynaptic sites. Postsynaptic GABABRs are predominantly found on dendritic spines, adjacent to excitatory synapses, but the control of their plasma membrane availability is still controversial. Here, we explore the role of glutamate receptor activation in regulating the function and surface availability of GABABRs in central neurons. We demonstrate that prolonged activation of NMDA receptors (NMDA-Rs) leads to endocytosis, a diversion from a recycling route, and subsequent lysosomal degradation of GABABRs. These sorting events are paralleled by a reduction in GABABR-dependent activation of inwardly rectifying K+ channel currents. Postendocytic sorting is critically dependent on phosphorylation of serine 783 (S783) within the GABABR2 subunit, an established substrate of AMP-dependent protein kinase (AMPK). NMDA-R activation leads to a rapid increase in phosphorylation of S783, followed by a slower dephosphorylation, which results from the activity of AMPK and protein phosphatase 2A, respectively. Agonist activation of GABABRs counters the effects of NMDA. Thus, NMDA-R activation alters the phosphorylation state of S783 and acts as a molecular switch to decrease the abundance of GABABRs at the neuronal plasma membrane. Such a mechanism may be of significance during synaptic plasticity or pathological conditions, such as ischemia or epilepsy, which lead to prolonged activation of glutamate receptors.
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Vardya I, Drasbek KR, Gibson KM, Jensen K. Plasticity of postsynaptic, but not presynaptic, GABAB receptors in SSADH deficient mice. Exp Neurol 2010; 225:114-22. [PMID: 20570675 DOI: 10.1016/j.expneurol.2010.05.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 04/26/2010] [Accepted: 05/27/2010] [Indexed: 12/28/2022]
Abstract
Succinic semialdehyde dehydrogenase (SSADH) deficiency is an autosomal-recessively inherited disorder of gamma-aminobutyrate (GABA) catabolism characterized by ataxia and epilepsy. Since SSADH is responsible for GABA break-down downstream of GABA transaminase, patients manifest high extracellular levels of GABA, as well as the GABA(B) receptor (GABA(B)R) agonist gamma-hydroxybutyrate (GHB). SSADH knockout (KO) mice display absence seizures, which progress into lethal tonic-clonic seizures at around 3weeks of age. It is hypothesized that desensitization of GABA(B)Rs plays an important role in the disease, although detailed studies of pre- and postsynaptic GABA(B)Rs are not available. We performed patch-clamp recordings from layer 2/3 pyramidal neurons in neocortical brain slices of wild-type (WT) and SSADH KO mice. Electrical stimulation of GABAergic fibers during wash in of the GABA(B)R agonist baclofen revealed no difference in presynaptic GABA(B)R mediated inhibition of GABA release between WT and SSADH KO mice. In contrast, a significant decrease in postsynaptic baclofen-induced potassium currents was seen in SSADH KO mice. This reduction was unlikely to be caused by accumulation of potassium, GABA or GHB in the brain slices, or an altered expression of regulators of G-protein signaling (RGS) proteins. Finally, adenosine-induced potassium currents were also reduced in SSADH KO mice, which could suggest heterologous desensitization of the G-protein dependent effectors, leading to a reduction in G-protein coupled inwardly rectifying potassium (GIRK) channel responses. Our findings indicate that high GABA and GHB levels desensitize postsynaptic, but not certain presynaptic, GABA(B)Rs, promoting a decrease in GIRK channel function. These changes could contribute to the development of seizures in SSADH KO mice and potentially also in affected patients.
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Affiliation(s)
- Irina Vardya
- Synaptic Physiology Laboratory, Department of Physiology and Biophysics, Aarhus University, Denmark
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50
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Direct interaction of GABAB receptors with M2 muscarinic receptors enhances muscarinic signaling. J Neurosci 2010; 29:15796-809. [PMID: 20016095 DOI: 10.1523/jneurosci.4103-09.2009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Downregulation of G-protein-coupled receptors (GPCRs) provides an important mechanism for reducing neurotransmitter signaling during sustained stimulation. Chronic stimulation of M(2) muscarinic receptors (M(2)Rs) causes internalization of M(2)R and G-protein-activated inwardly rectifying potassium (GIRK) channels in neuronal PC12 cells, resulting in loss of function. Here, we show that coexpression of GABA(B) R2 receptors (GBR2s) rescues both surface expression and function of M(2)R, including M(2)R-induced activation of GIRKs and inhibition of cAMP production. GBR2 showed significant association with M(2)R at the plasma membrane but not other GPCRs (M(1)R, mu-opioid receptor), as detected by fluorescence resonance energy transfer measured with total internal reflection fluorescence microscopy. Unique regions of the proximal C-terminal domains of GBR2 and M(2)R mediate specific binding between M(2)R and GBR2. In the brain, GBR2, but not GBR1, biochemically coprecipitates with M(2)R and overlaps with M(2)R expression in cortical neurons. This novel heteromeric association between M(2)R and GBR2 provides a possible mechanism for altering muscarinic signaling in the brain and represents a previously unrecognized role for GBR2.
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