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Yuan X, Wang Y, Li X, Zhong S, Zhou D, Lin X, Fang H, Yang Y, Wang M. Loss-of-function mutation in DDX53 associated with hereditary spastic paraplegia-like disorder. J Mol Med (Berl) 2024; 102:913-926. [PMID: 38753040 DOI: 10.1007/s00109-024-02454-4] [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: 10/31/2023] [Revised: 04/30/2024] [Accepted: 05/03/2024] [Indexed: 06/29/2024]
Abstract
DEAD-box helicase 53 (DDX53) is a member of the DEAD-box protein family of RNA helicases. Unlike other family members that are responsible for RNA metabolism, the biological function of DDX53 and its impact on the human condition are unclear. Herein, we found a full-length DDX53 deletion mutation in a hereditary spastic paraplegia-like (HSP-like) patient with lower extremity spasticity, walking disorder, visual impairment, and lateral ventricular white matter lesions. Bioinformatic analysis revealed that DDX53 was mainly expressed in the cerebellar cortex and may function as a tissue-specific RNA helicase. Transcriptome analysis showed that the expression of multiple brain-associated genes involved in synapse organization, neuron function, and neuromuscular junctions was affected by DDX53 depletion. Moreover, RNA immunoprecipitation sequencing (RIP-seq) analysis showed that DDX53 interacted with 176 genes, and 96 of these genes were associated with the execution of neurofunction, particularly in the regulation of cell projection organization and nervous system development. Collectively, although a more specified cell or animal model is required to fully understand the functional role of DDX53 in the human brain, we report for the first time that the patient with DDX53 defects exhibits HSP-like symptoms and that DDX53 is essential for maintaining neuronal function, with loss-of-function mutation in DDX53 potentially leading to HSP due to impaired RNA metabolism in the nervous system. KEY MESSAGES: DDX53 deficiency was first reported to be associated with HSP disorder. DDX53 exhibited minimal impact on mitochondrial function. DDX53 impaired RNA metabolism in the nervous system.
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Affiliation(s)
- Xiangshu Yuan
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Ya Wang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Xiyuan Li
- Baylor Genetics, Houston, TX, 77030, USA
| | - Sheng Zhong
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Danyi Zhou
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Xianlong Lin
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China
| | - Hezhi Fang
- Key Laboratory of Laboratory Medicine, Ministry of Education, Zhejiang Provincial Key Laboratory of Medical Genetics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, 325035, Zhejiang, China.
| | - Yanling Yang
- Department of Pediatrics, Peking University First Hospital, Beijing, 100034, China.
| | - Maofeng Wang
- Department of Biomedical Sciences Laboratory, Affiliated Dongyang Hospital of Wenzhou Medical University, Dongyang, 322100, Zhejiang, China.
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Martín-Belmonte A, Aguado C, Alfaro-Ruiz R, Kulik A, de la Ossa L, Moreno-Martínez AE, Alberquilla S, García-Carracedo L, Fernández M, Fajardo-Serrano A, Aso E, Shigemoto R, Martín ED, Fukazawa Y, Ciruela F, Luján R. Nanoarchitecture of Ca V2.1 channels and GABA B receptors in the mouse hippocampus: Impact of APP/PS1 pathology. Brain Pathol 2024:e13279. [PMID: 38887180 DOI: 10.1111/bpa.13279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 05/27/2024] [Indexed: 06/20/2024] Open
Abstract
Voltage-gated CaV2.1 (P/Q-type) Ca2+ channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as learning and memory. Despite their recognized importance in neural function, there is limited information on their potential involvement in neurodegenerative conditions such as Alzheimer's disease (AD). Here, we aimed to explore the impact of AD pathology on the density and nanoscale compartmentalization of CaV2.1 channels in the hippocampus in association with GABAB receptors. Histoblotting experiments showed that the density of CaV2.1 channel was significantly reduced in the hippocampus of APP/PS1 mice in a laminar-dependent manner. CaV2.1 channel was enriched in the active zone of the axon terminals and was present at a very low density over the surface of dendritic tree of the CA1 pyramidal cells, as shown by quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL). In APP/PS1 mice, the density of CaV2.1 channel in the active zone was significantly reduced in the strata radiatum and lacunosum-moleculare, while it remained unaltered in the stratum oriens. The decline in Cav2.1 channel density was found to be associated with a corresponding impairment in the GABAergic synaptic function, as evidenced by electrophysiological experiments carried out in the hippocampus of APP/PS1 mice. Remarkably, double SDS-FRL showed a co-clustering of CaV2.1 channel and GABAB1 receptor in nanodomains (~40-50 nm) in wild type mice, while in APP/PS1 mice this nanoarchitecture was absent. Together, these findings suggest that the AD pathology-induced reduction in CaV2.1 channel density and CaV2.1-GABAB1 de-clustering may play a role in the synaptic transmission alterations shown in the AD hippocampus. Therefore, uncovering these layer-dependent changes in P/Q calcium currents associated with AD pathology can benefit the development of future strategies for AD management.
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Affiliation(s)
- Alejandro Martín-Belmonte
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Carolina Aguado
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Rocío Alfaro-Ruiz
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Akos Kulik
- Institute for Physiology II, Medical Faculty, University of Freiburg, Freiburg, Germany
| | - Luis de la Ossa
- Departamento de Sistemas Informáticos, Escuela Superior de Ingeniería Informática, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Ana Esther Moreno-Martínez
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Samuel Alberquilla
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Lucía García-Carracedo
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Miriam Fernández
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Ana Fajardo-Serrano
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
| | - Ester Aso
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Eduardo D Martín
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Faculty of Medical Science, University of Fukui, Fukui, Japan
- Life Science Innovation Center, University of Fukui, Fukui, Japan
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Rafael Luján
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
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Lee SJ, Maeda S, Gao J, Nichols CG. Oxidation Driven Reversal of PIP 2-dependent Gating in GIRK2 Channels. FUNCTION 2023; 4:zqad016. [PMID: 37168492 PMCID: PMC10165546 DOI: 10.1093/function/zqad016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 03/24/2023] [Accepted: 04/03/2023] [Indexed: 05/13/2023] Open
Abstract
Physiological activity of G protein gated inward rectifier K+ (GIRK, Kir3) channel, dynamically regulated by three key ligands, phosphoinositol-4,5-bisphosphate (PIP2), Gβγ, and Na+, underlies cellular electrical response to multiple hormones and neurotransmitters in myocytes and neurons. In a reducing environment, matching that inside cells, purified GIRK2 (Kir3.2) channels demonstrate low basal activity, and expected sensitivity to the above ligands. However, under oxidizing conditions, anomalous behavior emerges, including rapid loss of PIP2 and Na+-dependent activation and a high basal activity in the absence of any agonists, that is now paradoxically inhibited by PIP2. Mutagenesis identifies two cysteine residues (C65 and C190) as being responsible for the loss of PIP2 and Na+-dependent activity and the elevated basal activity, respectively. The results explain anomalous findings from earlier studies and illustrate the potential pathophysiologic consequences of oxidation on GIRK channel function, as well as providing insight to reversed ligand-dependence of Kir and KirBac channels.
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Affiliation(s)
| | - Shoji Maeda
- Department of Pharmacology, Medical School, University of Michigan, Ann Arbor, Michigan, USA
| | - Jian Gao
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Colin G Nichols
- Department of Cell Biology and Physiology and the Center for Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
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Intrathecal Baclofen for Spasticity: Is There an Effect on Bladder Function? Report of Three Cases and Review of the Literature. Biomedicines 2022; 10:biomedicines10123266. [PMID: 36552022 PMCID: PMC9775073 DOI: 10.3390/biomedicines10123266] [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: 11/15/2022] [Revised: 12/07/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
INTRODUCTION traumatic brain injury (TBI) is very often associated with spasticity. Medical interventions may include medications such as baclofen, a Gamma-Aminobutyric Acid (GABA) -receptor agonist of poor lipid solubility. Intrathecal baclofen (ITB) administration is a contemporary treatment option which minimizes adverse effects in contrast with the oral form of the drug. Regarding low urinary tract dysfunction, TBI, as a suprapontine lesion, results in neurogenic detrusor overactivity. Frequency, urgency and urge incontinence are the predominant signs and symptoms of this condition. Our study aims to report the potential changes in bladder function in patients with spasticity, due to TBI, after the implantation of the baclofen pump and the control of spasticity. MATERIAL AND METHODS We report three cases of TBI whose spasticity responded well to ITB. We evaluated our medical reports regarding bladder function retrospectively, before and after baclofen pump implantation. We compared the data of bladder diaries and urodynamic parameters. RESULTS Bladder function was improved in all patients. Regarding bladder diaries; the number of incontinence and micturition episodes was decreased and the volume per void was slightly increased. Regarding urodynamic parameters; bladder capacity and reflex volume increased, Pdetmax decreased, PVR was the same and DLPP was slightly decreased. CONCLUSIONS Although the baclofen pump is implanted to treat spasticity, detrusor activity may be also affected. Therefore, patients' urologic profiles should also be reevaluated after ITB. Further prospective studies are required to investigate the effect of ITB on bladder function in the clinical field and also at the basic science level.
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Cediel ML, Stawarski M, Blanc X, Nosková L, Magner M, Platzer K, Gburek-Augustat J, Baldridge D, Constantino JN, Ranza E, Bettler B, Antonarakis SE. GABBR1 monoallelic de novo variants linked to neurodevelopmental delay and epilepsy. Am J Hum Genet 2022; 109:1885-1893. [PMID: 36103875 PMCID: PMC9606381 DOI: 10.1016/j.ajhg.2022.08.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 08/15/2022] [Indexed: 01/25/2023] Open
Abstract
GABAB receptors are obligatory heterodimers responsible for prolonged neuronal inhibition in the central nervous system. The two receptor subunits are encoded by GABBR1 and GABBR2. Variants in GABBR2 have been associated with a Rett-like phenotype (MIM: 617903), epileptic encephalopathy (MIM: 617904), and milder forms of developmental delay with absence epilepsy. To date, however, no phenotypes associated with pathogenic variants of GABBR1 have been established. Through GeneMatcher, we have ascertained four individuals who each have a monoallelic GABBR1 de novo non-synonymous variant; these individuals exhibit motor and/or language delay, ranging from mild to severe, and in one case, epilepsy. Further phenotypic features include varying degrees of intellectual disability, learning difficulties, autism, ADHD, ODD, sleep disorders, and muscular hypotonia. We functionally characterized the four de novo GABBR1 variants, p.Glu368Asp, p.Ala397Val, p.Ala535Thr, and p.Gly673Asp, in transfected HEK293 cells. GABA fails to efficiently activate the variant receptors, most likely leading to an increase in the excitation/inhibition balance in the central nervous system. Variant p.Gly673Asp in transmembrane domain 3 (TMD3) renders the receptor completely inactive, consistent with failure of the receptor to reach the cell surface. p.Glu368Asp is located near the orthosteric binding site and reduces GABA potency and efficacy at the receptor. GABA exhibits normal potency but decreased efficacy at the p.Ala397Val and p.Ala535Thr variants. Functional characterization of GABBR1-related variants provides a rationale for understanding the severity of disease phenotypes and points to possible therapeutic strategies.
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Affiliation(s)
- Maria Lucia Cediel
- Medigenome, Swiss Institute of Genomic Medicine, 1207 Geneva, Switzerland
| | - Michal Stawarski
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
| | - Xavier Blanc
- Medigenome, Swiss Institute of Genomic Medicine, 1207 Geneva, Switzerland
| | - Lenka Nosková
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Martin Magner
- Department of Pediatrics and Inherited Metabolic Disorders, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic; Department of Pediatrics, First Faculty of Medicine, Charles University and University Thomayer Hospital in Prague, Prague, Czech Republic
| | - Konrad Platzer
- Institute of Human Genetics, University of Leipzig Medical Center, Leipzig, Germany
| | - Janina Gburek-Augustat
- Division of Neuropaediatrics, Hospital for Children and Adolescents, University Hospital Leipzig, Leipzig, Germany
| | | | | | - Emmanuelle Ranza
- Medigenome, Swiss Institute of Genomic Medicine, 1207 Geneva, Switzerland
| | - Bernhard Bettler
- Department of Biomedicine, Pharmazentrum, University of Basel, Klingelbergstrasse 50/70, 4056 Basel, Switzerland
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Nayak AP, An SS. Anxiolytics for Bronchodilation: Refinements to GABA A Agonists for Asthma Relief. Am J Respir Cell Mol Biol 2022; 67:419-420. [PMID: 35901197 PMCID: PMC9564927 DOI: 10.1165/rcmb.2022-0287ed] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- Ajay P. Nayak
- Center for Translational Medicine,Department of MedicineThomas Jefferson UniversityPhiladelphia, Pennsylvania
| | - Steven S. An
- Rutgers Institute for Translational Medicine and ScienceNew Brunswick, New Jersey,Rutgers-Robert Wood Johnson Medical SchoolThe State University of New JerseyPiscataway, New Jersey
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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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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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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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Density of GABA B Receptors Is Reduced in Granule Cells of the Hippocampus in a Mouse Model of Alzheimer's Disease. Int J Mol Sci 2020; 21:ijms21072459. [PMID: 32252271 PMCID: PMC7177735 DOI: 10.3390/ijms21072459] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 12/22/2022] Open
Abstract
Metabotropic γ-aminobutyric acid (GABAB) receptors contribute to the control of network activity and information processing in hippocampal circuits by regulating neuronal excitability and synaptic transmission. The dysfunction in the dentate gyrus (DG) has been implicated in Alzheimer´s disease (AD). Given the involvement of GABAB receptors in AD, to determine their subcellular localisation and possible alteration in granule cells of the DG in a mouse model of AD at 12 months of age, we used high-resolution immunoelectron microscopic analysis. Immunohistochemistry at the light microscopic level showed that the regional and cellular expression pattern of GABAB1 was similar in an AD model mouse expressing mutated human amyloid precursor protein and presenilin1 (APP/PS1) and in age-matched wild type mice. High-resolution immunoelectron microscopy revealed a distance-dependent gradient of immunolabelling for GABAB receptors, increasing from proximal to distal dendrites in both wild type and APP/PS1 mice. However, the overall density of GABAB receptors at the neuronal surface of these postsynaptic compartments of granule cells was significantly reduced in APP/PS1 mice. Parallel to this reduction in surface receptors, we found a significant increase in GABAB1 at cytoplasmic sites. GABAB receptors were also detected at presynaptic sites in the molecular layer of the DG. We also found a decrease in plasma membrane GABAB receptors in axon terminals contacting dendritic spines of granule cells, which was more pronounced in the outer than in the inner molecular layer. Altogether, our data showing post- and presynaptic reduction in surface GABAB receptors in the DG suggest the alteration of the GABAB-mediated modulation of excitability and synaptic transmission in granule cells, which may contribute to the cognitive dysfunctions in the APP/PS1 model of AD.
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Abstract
BACKGROUND Baclofen pumps provide treatment of symptoms of spasticity for disease processes such as cerebral palsy and traumatic brain injury. These devices provide continuous infusion or periodic dosing of intrathecal baclofen (ITB). Traditionally, these pumps have been placed subcutaneously. Subcutaneous device placement has been associated with infection and extrusion. Baclofen pumps are large and range from 8 to 10 cm in diameter and 4 to 8 cm in width. Patients requiring device placement typically have a paucity of subcutaneous tissue. Cachexia coupled with the size and bulk of these devices leads to increased protusion and friction. Submuscular placement provides a well-vascularized pocket that directs the device inward eliminating protrusion and decreasing the potential for soft tissue breakdown. METHODS A retrospective chart review of ITB pump placement in a submuscular plane by a single plastic surgeon at a major academic center in conjunction with a neurosurgeon was performed. Inclusion criteria were cases of primary placement or replacement of ITB pumps and spasticity requiring ITB. Major complications included infection, extrusion, and reoperation. RESULTS Five patients during a 5-month period were treated with submuscular placement of ITB pumps. Average age of patients included was 18.4 years. Average preoperative body mass index was 18.8 kg/m, with values ranging from 15.8 to 20.1 kg/m. Medical histories of patients included diagnoses of cerebral palsy and traumatic brain injury causing spasticity. The most frequently cited reason for plastic surgical consultation preoperatively was cachexia. Two patients had previous baclofen pumps placed subcutaneously. Average follow-up was 6 months and ranged from 3 to 13 months. There were no major complications. One patient had a small seroma that spontaneously resolved. No patient had wound healing problems, and there were no extrusions of implanted devices or reoperations. CONCLUSION Submuscular placement of baclofen pumps provides a well-vascularized and stable environment for device placement that minimizes the dangers of pump extrusion and infection. Patients who require treatment with ITB commonly have severe cachexia, which makes subcutaneous device placement high risk. Submuscular placement should be performed in all patients with body mass index less than 20 kg/m.
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Lima Neto JX, Bezerra KS, Barbosa ED, Oliveira JIN, Manzoni V, Soares-Rachetti VP, Albuquerque EL, Fulco UL. Exploring the Binding Mechanism of GABAB Receptor Agonists and Antagonists through in Silico Simulations. J Chem Inf Model 2019; 60:1005-1018. [DOI: 10.1021/acs.jcim.9b01025] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- José X. Lima Neto
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Katyanna S. Bezerra
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Emmanuel D. Barbosa
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Jonas I. N. Oliveira
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Vinícius Manzoni
- Instituto de Física, Universidade Federal do Alagoas, 57072-970 Maceió-AL, Brazil
| | - Vanessa P. Soares-Rachetti
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Eudenilson L. Albuquerque
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
| | - Umberto L. Fulco
- Departamento de Biofísica e Farmacologia, Universidade Federal do Rio Grande do Norte, 59072-970 Natal-RN, Brazil
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孙 智, 陈 倩, 李 明, 马 维, 赵 旭, 黄 卓. [Chronic phosphoproteomic in temporal lobe epilepsy mouse models induced by kainic acid]. BEIJING DA XUE XUE BAO. YI XUE BAN = JOURNAL OF PEKING UNIVERSITY. HEALTH SCIENCES 2019; 51:197-205. [PMID: 30996354 PMCID: PMC7441195 DOI: 10.19723/j.issn.1671-167x.2019.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Indexed: 06/09/2023]
Abstract
OBJECTIVE To investigate functions of proteins and signaling pathways involved in epileptogenesis during the chronic stage of temporal lobe epilepsy in mouse models. METHODS Kainic acid-induced temporal lobe epilepsy models were conducted, when reaching stage 4 using racine scale, the mice of experimental group were supposed to be successfully established. Pentobarbital sodium was injected to stop epileptic seizure in case of death. Twenty-eight days after the kainic acid injection, when the experimental group generally turned into chronic spontaneous seizures, mice hippocampal tissues were extracted from the control and the experimental groups respectively for phosphoproteomic. Enriched phosphorylated proteins were detected using mass spectrometry, only the proteins whose density was greater than 106 were analyzed by matching the Gene Ontology (GO) database, Kyoto Encyclopedia of Genes and Genomes (KEGG) database and STRING database to detect proteins involved in epileptogenesis in protein functions, signaling pathways and protein-protein interaction respectively. After that, literatures were reviewed about the key proteins. RESULTS (1) Total of 12 697 phosphorylation sites of enriched proteins were detected by mass spectrometry, and there were 159 sites whose phosphorylation levels were significantly different from the control (P<0.001). (2) GO database showed that 35.7% of the 159 sites were about "catalytic activity", 39.5% were about "binding" and 20.8% were about "cell communication", and the 159 proteins also participated in many biological processes, such as "primary metabolic process" "response to stimulus" "developmental process" "localization" and "phosphate-containing compound metabolic process". (3) KEGG database showed that the 159 protein sites mainly involved in 10 signaling pathways: glutamatergic synapse, Ras signaling pathway, African trypanosomiasis, Cocaine addiction, Circadian entrainment, Amyotrophic lateral sclerosis (ALS), Long-term potentiation, Endocytosis, Gap junction, Nicotine addiction. (4) STRING database showed that the protein-protein interaction network formed by the 159 proteins was focused on Grin1/Dlg3, Arhgef 2/Arhgap33/Tiam1 and Sptnb1/3/4/Add3/Ank2 protein group respectively. (5) Phosphorylation levels of Grin1, Arhgef 2, Arhgap33, Tiam1, Sptbn1/2/4 and Ank2 in experimental group were significantly higher than in the control (P<0.001). CONCLUSION Phosphoproteomic illustrated integral distribution of phosphorylated proteins at the chronic stage of temporal lobe epilepsy in the mouse model. Literatures showed that most key proteins were closely related to epileptogenesis, suggesting that some proteins or signaling pathways may play a role in epileptogenesis, such as dopamine and Kir3.1.
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Affiliation(s)
- 智明 孙
- 北京大学药学院分子与细胞药理学系 天然药物与仿生药物国家重点实验室 系统生物医学研究所, 北京 100191Institute of Systems Biomedicine, State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, Peking University School of Pharmaceutical Science, Beijing 100191, China
| | - 倩 陈
- 北京大学药学院分子与细胞药理学系 天然药物与仿生药物国家重点实验室 系统生物医学研究所, 北京 100191Institute of Systems Biomedicine, State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, Peking University School of Pharmaceutical Science, Beijing 100191, China
| | - 明华 李
- 北京大学药学院分子与细胞药理学系 天然药物与仿生药物国家重点实验室 系统生物医学研究所, 北京 100191Institute of Systems Biomedicine, State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, Peking University School of Pharmaceutical Science, Beijing 100191, China
| | - 维宁 马
- 中国医科大学附属盛京医院神经外科, 沈阳 110000Department of Neurosurgery, Sheng Jing Hospital affiliated to China Medical University, Shenyang 110000, China
| | - 旭阳 赵
- 北京大学药学院分子与细胞药理学系 天然药物与仿生药物国家重点实验室 系统生物医学研究所, 北京 100191Institute of Systems Biomedicine, State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, Peking University School of Pharmaceutical Science, Beijing 100191, China
- 北京大学基础医学院北京肿瘤系统生物学重点实验室, 北京 100191Beijing Key Laboratory of Tumor Systems Biology, Peking University School of Basic Medical Science, Beijing 100191, China
| | - 卓 黄
- 北京大学药学院分子与细胞药理学系 天然药物与仿生药物国家重点实验室 系统生物医学研究所, 北京 100191Institute of Systems Biomedicine, State Key Laboratory of Natural and Biomimetic Drugs, Department of Molecular and Cellular Pharmacology, Peking University School of Pharmaceutical Science, Beijing 100191, China
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Kulik Á, Booker SA, Vida I. Differential distribution and function of GABABRs in somato-dendritic and axonal compartments of principal cells and interneurons in cortical circuits. Neuropharmacology 2018; 136:80-91. [DOI: 10.1016/j.neuropharm.2017.10.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/12/2017] [Accepted: 10/13/2017] [Indexed: 12/24/2022]
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15
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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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16
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Shen W, Nan C, Nelson PT, Ripps H, Slaughter MM. GABA B receptor attenuation of GABA A currents in neurons of the mammalian central nervous system. Physiol Rep 2017; 5:5/6/e13129. [PMID: 28348006 PMCID: PMC5371550 DOI: 10.14814/phy2.13129] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 11/18/2016] [Indexed: 11/24/2022] Open
Abstract
Ionotropic receptors are tightly regulated by second messenger systems and are often present along with their metabotropic counterparts on a neuron's plasma membrane. This leads to the hypothesis that the two receptor subtypes can interact, and indeed this has been observed in excitatory glutamate and inhibitory GABA receptors. In both systems the metabotropic pathway augments the ionotropic receptor response. However, we have found that the metabotropic GABAB receptor can suppress the ionotropic GABAA receptor current, in both the in vitro mouse retina and in human amygdala membrane fractions. Expression of amygdala membrane microdomains in Xenopus oocytes by microtransplantation produced functional ionotropic and metabotropic GABA receptors. Most GABAA receptors had properties of α‐subunit containing receptors, with ~5% having ρ‐subunit properties. Only GABAA receptors with α‐subunit‐like properties were regulated by GABAB receptors. In mouse retinal ganglion cells, where only α‐subunit‐containing GABAA receptors are expressed, GABAB receptors suppressed GABAA receptor currents. This suppression was blocked by GABAB receptor antagonists, G‐protein inhibitors, and GABAB receptor antibodies. Based on the kinetic differences between metabotropic and ionotropic receptors, their interaction would suppress repeated, rapid GABAergic inhibition.
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Affiliation(s)
- Wen Shen
- Department of Biomedical Science, Charles E. Schmidt College of Medicine Florida Atlantic University, Boca Raton, Florida
| | - Changlong Nan
- Department of Biomedical Science, Charles E. Schmidt College of Medicine Florida Atlantic University, Boca Raton, Florida
| | - Peter T Nelson
- Division of Neuropathology, Department of Pathology, University of Kentucky, Lexington, Kentucky.,Sanders-Brown Centre on Aging, University of Kentucky, Lexington, Kentucky
| | - Harris Ripps
- Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine, Chicago, Illinois.,Whitman Investigator, Marine Biological Laboratory, Woods Hole, Massachusetts
| | - Malcolm M Slaughter
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York
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17
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Differential association of GABA B receptors with their effector ion channels in Purkinje cells. Brain Struct Funct 2017; 223:1565-1587. [PMID: 29177691 PMCID: PMC5869904 DOI: 10.1007/s00429-017-1568-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 11/10/2017] [Indexed: 11/23/2022]
Abstract
Metabotropic GABAB receptors mediate slow inhibitory effects presynaptically and postsynaptically through the modulation of different effector signalling pathways. Here, we analysed the distribution of GABAB receptors using highly sensitive SDS-digested freeze-fracture replica labelling in mouse cerebellar Purkinje cells. Immunoreactivity for GABAB1 was observed on presynaptic and, more abundantly, on postsynaptic compartments, showing both scattered and clustered distribution patterns. Quantitative analysis of immunoparticles revealed a somato-dendritic gradient, with the density of immunoparticles increasing 26-fold from somata to dendritic spines. To understand the spatial relationship of GABAB receptors with two key effector ion channels, the G protein-gated inwardly rectifying K+ (GIRK/Kir3) channel and the voltage-dependent Ca2+ channel, biochemical and immunohistochemical approaches were performed. Co-immunoprecipitation analysis demonstrated that GABAB receptors co-assembled with GIRK and CaV2.1 channels in the cerebellum. Using double-labelling immunoelectron microscopic techniques, co-clustering between GABAB1 and GIRK2 was detected in dendritic spines, whereas they were mainly segregated in the dendritic shafts. In contrast, co-clustering of GABAB1 and CaV2.1 was detected in dendritic shafts but not spines. Presynaptically, although no significant co-clustering of GABAB1 and GIRK2 or CaV2.1 channels was detected, inter-cluster distance for GABAB1 and GIRK2 was significantly smaller in the active zone than in the dendritic shafts, and that for GABAB1 and CaV2.1 was significantly smaller in the active zone than in the dendritic shafts and spines. Thus, GABAB receptors are associated with GIRK and CaV2.1 channels in different subcellular compartments. These data provide a better framework for understanding the different roles played by GABAB receptors and their effector ion channels in the cerebellar network.
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18
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G-Protein Coupled Receptors Targeted by Analgesic Venom Peptides. Toxins (Basel) 2017; 9:toxins9110372. [PMID: 29144441 PMCID: PMC5705987 DOI: 10.3390/toxins9110372] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 11/13/2017] [Accepted: 11/13/2017] [Indexed: 12/14/2022] Open
Abstract
Chronic pain is a complex and debilitating condition associated with a large personal and socioeconomic burden. Current pharmacological approaches to treating chronic pain such as opioids, antidepressants and anticonvulsants exhibit limited efficacy in many patients and are associated with dose-limiting side effects that hinder their clinical use. Therefore, improved strategies for the pharmacological treatment of pathological pain are urgently needed. G-protein coupled receptors (GPCRs) are ubiquitously expressed on the surface of cells and act to transduce extracellular signals and regulate physiological processes. In the context of pain, numerous and diverse families of GPCRs expressed in pain pathways regulate most aspects of physiological and pathological pain and are thus implicated as potential targets for therapy of chronic pain. In the search for novel compounds that produce analgesia via GPCR modulation, animal venoms offer an enormous and virtually untapped source of potent and selective peptide molecules. While many venom peptides target voltage-gated and ligand-gated ion channels to inhibit neuronal excitability and blunt synaptic transmission of pain signals, only a small proportion are known to interact with GPCRs. Of these, only a few have shown analgesic potential in vivo. Here we review the current state of knowledge regarding venom peptides that target GPCRs to produce analgesia, and their development as therapeutic compounds.
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19
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Carletti R, Tacconi S, Mugnaini M, Gerrard P. Receptor distribution studies. Curr Opin Pharmacol 2017; 35:94-100. [PMID: 28803835 DOI: 10.1016/j.coph.2017.07.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 07/23/2017] [Indexed: 12/18/2022]
Abstract
Receptor distribution studies have played a key role in the characterization of receptor systems (e.g. GABAB, NMDA (GluNRs), and Neurokinin 1) and in generating hypotheses to exploit these systems as potential therapeutic targets. Distribution studies can provide important information on the potential role of candidate receptors in normal physiology/disease and alert for possible adverse effects of targeting the receptors. Moreover, they can provide valuable information relating to quantitative target engagement (e.g. % receptor occupancy) to drive mechanistic pharmacokinetic/pharmacodynamic (PK/PD) hypotheses for compounds in the Drug Discovery process. Finally, receptor distribution and quantitative target engagement studies can be used to validate truly translational technologies such as PET ligands and pharmacoEEG paradigms to facilitate bridging of the preclinical/clinical interface and thus increase probability of success.
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Affiliation(s)
- Renzo Carletti
- Center of Drug Discovery & Development, Aptuit S.r.l., via Fleming 4, 37135 Verona, Italy.
| | - Stefano Tacconi
- Center of Drug Discovery & Development, Aptuit S.r.l., via Fleming 4, 37135 Verona, Italy
| | - Manolo Mugnaini
- Neuroscience Discovery, AbbVie Deutschland GmbH & Co. KG, Knollstraße 50, 67061 Ludwigshafen, Germany
| | - Philip Gerrard
- Center of Drug Discovery & Development, Aptuit S.r.l., via Fleming 4, 37135 Verona, Italy
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20
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Brondino N, Fusar-Poli L, Panisi C, Damiani S, Barale F, Politi P. Pharmacological Modulation of GABA Function in Autism Spectrum Disorders: A Systematic Review of Human Studies. J Autism Dev Disord 2016; 46:825-39. [PMID: 26443675 DOI: 10.1007/s10803-015-2619-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Autism spectrum disorders are an emerging health problem worldwide, but little is known about their pathogenesis. It has been hypothesized that autism may result from an imbalance between excitatory glutamatergic and inhibitory GABAergic pathways. Commonly used medications such as valproate, acamprosate, and arbaclofen may act on the GABAergic system and be a potential treatment for people with ASD. The present systematic review aimed at evaluating the state-of-the-art of clinical trials of GABA modulators in autism. To date there is insufficient evidence to suggest the use of these drugs in autistic subjects, even if data are promising. Of note, short-term use of all the reviewed medications appears to be safe. Future well designed trials are needed to elucidate these preliminary findings.
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Affiliation(s)
- Natascia Brondino
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy.
| | - Laura Fusar-Poli
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy
| | - Cristina Panisi
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy
| | - Stefano Damiani
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy
| | - Francesco Barale
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy
| | - Pierluigi Politi
- Department of Brain and Behavioral Sciences, University of Pavia, Via Bassi 21, 27100, Pavia, Italy
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21
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GABAergic Regulation of Adult Hippocampal Neurogenesis. Mol Neurobiol 2016; 54:5497-5510. [DOI: 10.1007/s12035-016-0072-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/18/2016] [Indexed: 01/17/2023]
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22
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Sodium salicylate potentiates the GABAB-GIRK pathway to suppress rebound depolarization in neurons of the rat's medial geniculate body. Hear Res 2015; 332:104-112. [PMID: 26688177 DOI: 10.1016/j.heares.2015.11.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 11/16/2015] [Accepted: 11/23/2015] [Indexed: 12/15/2022]
Abstract
Rebound depolarization (RD) is a voltage response to the offset from pre-hyperpolarization of neuronal membrane potential, which manifests a particular form of the postsynaptic membrane potential response to inhibitory presynaptic inputs. We previously demonstrated that sodium salicylate (NaSal), a tinnitus inducer, can drastically suppress the RD in neurons of rat medial geniculate body (MGB) (Su et al, 2012; PLoS ONE 7, e46969). The purpose of the present study was to investigate the underlying cellular mechanism by using whole-cell patch-clamp recordings in rat MGB slices. NaSal (1.4 mM) had no effects on the current mediated by T-type Ca(2+) channels, indicating that it does not target these channels to suppress the RD. Instead, NaSal was shown to hyperpolarize the resting membrane potential to suppress the RD. NaSal had no effects on the current mediated by hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, indicating that it does not target these channels to hyperpolarize the resting membrane potential. NaSal induced an outward leak current that could be abolished by CGP55845, a GABAB receptor blocker, or respectively by Ba(2+) and Tertiapin-Q, blockers for G-protein-gated inwardly rectifying potassium (GIRK) channels, indicating that NaSal potentiates the GABAB-GIRK pathway to hyperpolarize the resting membrane potential. Our study demonstrates that NaSal targets GABAB receptors to alter functional behaviors of MGB neurons, which may be implicated in NaSal-induced tinnitus.
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23
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Kasten CR, Boehm SL. Identifying the role of pre-and postsynaptic GABA(B) receptors in behavior. Neurosci Biobehav Rev 2015; 57:70-87. [PMID: 26283074 DOI: 10.1016/j.neubiorev.2015.08.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 06/18/2015] [Accepted: 08/09/2015] [Indexed: 12/15/2022]
Abstract
Although many reviews exist characterizing the molecular differences of GABAB receptor isoforms, there is no current review of the in vivo effects of these isoforms. The current review focuses on whether the GABAB1a and GABAB1b isoforms contribute differentially to behaviors in isoform knockout mice. The roles of these receptors have primarily been characterized in cognitive, anxiety, and depressive phenotypes. Currently, the field supports a role of GABAB1a in memory maintenance and protection against an anhedonic phenotype, whereas GABAB1b appears to be involved in memory formation and a susceptibility to developing an anhedonic phenotype. Although GABAB receptors have been strongly implicated in drug abuse phenotypes, no isoform-specific work has been done in this field. Future directions include developing site-specific isoform knockdown to identify the role of different brain regions in behavior, as well as identifying how these isoforms are involved in development of behavioral phenotypes.
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Affiliation(s)
- Chelsea R Kasten
- Department of Psychology, Indianapolis University Purdue University-Indianapolis, 402N Blackford St LD 124, Indianapolis, IN 46202, United States.
| | - Stephen L Boehm
- Department of Psychology, Indianapolis University Purdue University-Indianapolis, 402N Blackford St LD 124, Indianapolis, IN 46202, United States; Indiana Alcohol Research Center, 545 Barnhill Drive EH 317, Indianapolis, IN, United States.
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Melé M, Ferreira PG, Reverter F, DeLuca DS, Monlong J, Sammeth M, Young TR, Goldmann JM, Pervouchine DD, Sullivan TJ, Johnson R, Segrè AV, Djebali S, Niarchou A, Wright FA, Lappalainen T, Calvo M, Getz G, Dermitzakis ET, Ardlie KG, Guigó R. Human genomics. The human transcriptome across tissues and individuals. Science 2015; 348:660-5. [PMID: 25954002 PMCID: PMC4547472 DOI: 10.1126/science.aaa0355] [Citation(s) in RCA: 859] [Impact Index Per Article: 95.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Transcriptional regulation and posttranscriptional processing underlie many cellular and organismal phenotypes. We used RNA sequence data generated by Genotype-Tissue Expression (GTEx) project to investigate the patterns of transcriptome variation across individuals and tissues. Tissues exhibit characteristic transcriptional signatures that show stability in postmortem samples. These signatures are dominated by a relatively small number of genes—which is most clearly seen in blood—though few are exclusive to a particular tissue and vary more across tissues than individuals. Genes exhibiting high interindividual expression variation include disease candidates associated with sex, ethnicity, and age. Primary transcription is the major driver of cellular specificity, with splicing playing mostly a complementary role; except for the brain, which exhibits a more divergent splicing program. Variation in splicing, despite its stochasticity, may play in contrast a comparatively greater role in defining individual phenotypes.
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Affiliation(s)
- Marta Melé
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Harvard Department of stem cell and regenerative biology, Harvard University, Cambridge, MA, USA
| | - Pedro G Ferreira
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland. Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland. Swiss Institute of Bioinformatics, Geneva, Switzerland
| | - Ferran Reverter
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain
| | | | - Jean Monlong
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain. McGill University, Montreal, Canada
| | - Michael Sammeth
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain. National Institute for Scientific Computing (LNCC), Petropolis, Rio de Janeiro, Brazil
| | | | - Jakob M Goldmann
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain. Radboud University, Nijmegen, Netherlands
| | - Dmitri D Pervouchine
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain. Faculty of Bioengineering and Bioinformatics, Moscow State University, Leninskie Gory 1-73, 119992 Moscow, Russia
| | | | - Rory Johnson
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain
| | | | - Sarah Djebali
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain
| | - Anastasia Niarchou
- Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland. Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland. Swiss Institute of Bioinformatics, Geneva, Switzerland
| | | | - Tuuli Lappalainen
- Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland. Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland. Swiss Institute of Bioinformatics, Geneva, Switzerland. New York Genome Center, New York, NY, USA. Department of Systems Biology, Columbia University, New York, NY, USA
| | - Miquel Calvo
- Facultat de Biologia, Universitat de Barcelona (UB), Barcelona, Catalonia, Spain
| | - Gad Getz
- Broad Institute of MIT and Harvard, Cambridge, MA, USA. Cancer Center and Department of Pathology, Massachusetts General Hospital, Boston, MA 02114, USA
| | - Emmanouil T Dermitzakis
- Department of Genetic Medicine and Development, University of Geneva, Geneva, Switzerland. Institute for Genetics and Genomics in Geneva (iGE3), University of Geneva, Geneva, Switzerland. Swiss Institute of Bioinformatics, Geneva, Switzerland
| | | | - Roderic Guigó
- Center for Genomic Regulation (CRG), Barcelona, Catalonia, Spain. Universitat Pompeu Fabra (UPF), Barcelona, Catalonia, Spain. Institut Hospital del Mar d'Investigacions Mèdiques (IMIM), Barcelona, Catalonia, Spain. Joint CRG-Barcelona Super Computing Center (BSC)-Institut de Recerca Biomedica (IRB) Program in Computational Biology, Barcelona, Catalonia, Spain.
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Shoemaker PA. Neuronal networks with NMDARs and lateral inhibition implement winner-takes-all. Front Comput Neurosci 2015; 9:12. [PMID: 25741276 PMCID: PMC4332340 DOI: 10.3389/fncom.2015.00012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 01/23/2015] [Indexed: 11/13/2022] Open
Abstract
A neural circuit that relies on the electrical properties of NMDA synaptic receptors is shown by numerical and theoretical analysis to be capable of realizing the winner-takes-all function, a powerful computational primitive that is often attributed to biological nervous systems. This biophysically-plausible model employs global lateral inhibition in a simple feedback arrangement. As its inputs increase, high-gain and then bi- or multi-stable equilibrium states may be assumed in which there is significant depolarization of a single neuron and hyperpolarization or very weak depolarization of other neurons in the network. The state of the winning neuron conveys analog information about its input. The winner-takes-all characteristic depends on the nonmonotonic current-voltage relation of NMDA receptor ion channels, as well as neural thresholding, and the gain and nature of the inhibitory feedback. Dynamical regimes vary with input strength. Fixed points may become unstable as the network enters a winner-takes-all regime, which can lead to entrained oscillations. Under some conditions, oscillatory behavior can be interpreted as winner-takes-all in nature. Stable winner-takes-all behavior is typically recovered as inputs increase further, but with still larger inputs, the winner-takes-all characteristic is ultimately lost. Network stability may be enhanced by biologically plausible mechanisms.
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Nava-Mesa MO, Jiménez-Díaz L, Yajeya J, Navarro-Lopez JD. GABAergic neurotransmission and new strategies of neuromodulation to compensate synaptic dysfunction in early stages of Alzheimer's disease. Front Cell Neurosci 2014; 8:167. [PMID: 24987334 PMCID: PMC4070063 DOI: 10.3389/fncel.2014.00167] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 06/02/2014] [Indexed: 01/06/2023] Open
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by cognitive decline, brain atrophy due to neuronal and synapse loss, and formation of two pathological lesions: extracellular amyloid plaques, composed largely of amyloid-beta peptide (Aβ), and neurofibrillary tangles formed by intracellular aggregates of hyperphosphorylated tau protein. Lesions mainly accumulate in brain regions that modulate cognitive functions such as the hippocampus, septum or amygdala. These brain structures have dense reciprocal glutamatergic, cholinergic, and GABAergic connections and their relationships directly affect learning and memory processes, so they have been proposed as highly susceptible regions to suffer damage by Aβ during AD course. Last findings support the emerging concept that soluble Aβ peptides, inducing an initial stage of synaptic dysfunction which probably starts 20–30 years before the clinical onset of AD, can perturb the excitatory–inhibitory balance of neural circuitries. In turn, neurotransmission imbalance will result in altered network activity that might be responsible of cognitive deficits in AD. Therefore, Aβ interactions on neurotransmission systems in memory-related brain regions such as amygdaloid complex, medial septum or hippocampus are critical in cognitive functions and appear as a pivotal target for drug design to improve learning and dysfunctions that manifest with age. Since treatments based on glutamatergic and cholinergic pharmacology in AD have shown limited success, therapies combining modulators of different neurotransmission systems including recent findings regarding the GABAergic system, emerge as a more useful tool for the treatment, and overall prevention, of this dementia. In this review, focused on inhibitory systems, we will analyze pharmacological strategies to compensate neurotransmission imbalance that might be considered as potential therapeutic interventions in AD.
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Affiliation(s)
| | - Lydia Jiménez-Díaz
- Neurophysiology and Behavior Lab, Centro Regional de Investigaciones Biomédicas, School of Medicine of Ciudad Real, University of Castilla-La Mancha Ciudad Real, Spain
| | - Javier Yajeya
- Department of Physiology and Pharmacology, University of Salamanca Salamanca, Spain
| | - Juan D Navarro-Lopez
- Neurophysiology and Behavior Lab, Centro Regional de Investigaciones Biomédicas, School of Medicine of Ciudad Real, University of Castilla-La Mancha Ciudad Real, Spain
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Effect of baclofen on morphine-induced conditioned place preference, extinction, and stress-induced reinstatement in chronically stressed mice. Psychopharmacology (Berl) 2014; 231:27-36. [PMID: 23892776 PMCID: PMC3889653 DOI: 10.1007/s00213-013-3204-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2013] [Accepted: 06/27/2013] [Indexed: 02/07/2023]
Abstract
RATIONALE AND OBJECTIVE A stress-induced increase in excitability can result from a reduction in inhibitory neurotransmission. Modulation of gamma-aminobutyric acid (GABA)ergic transmission is an effective treatment for drug seeking and relapse. This study investigated whether baclofen, a GABA(B) receptor agonist, had an impact on morphine-induced conditioned place preference (CPP), extinction, and stress-induced relapse in chronically stressed mice. METHODS Chronic stress was induced by restraining mice for 2 h for seven consecutive days. We first investigated whether chronic stress influenced morphine-induced CPP, extinction, and stress-induced relapse in the stressed mice. Next, we investigated whether three different doses of baclofen influenced chronic stress as measured by the expression of morphine-induced CPP. We chose the most effective dose for subsequent extinction and reinstatement experiments. Reinstatement of morphine-induced CPP was induced by a 6-min forced swim stress. Locomotor activity was also measured for each test. RESULTS Chronic stress facilitated the expression of morphine-induced CPP and prolonged extinction time. Forced swim stress primed the reinstatement of morphine-induced CPP in mice. Baclofen treatment affected the impact of chronic stress on different phases of morphine-induced CPP. CONCLUSIONS Our results showed that baclofen antagonized the effects of chronic stress on morphine-induced CPP. These findings suggest the potential clinical utility of GABA(B) receptor-positive modulators as an anti-addiction agent in people suffering from chronic stress.
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Nava-Mesa MO, Jiménez-Díaz L, Yajeya J, Navarro-Lopez JD. Amyloid-β induces synaptic dysfunction through G protein-gated inwardly rectifying potassium channels in the fimbria-CA3 hippocampal synapse. Front Cell Neurosci 2013; 7:117. [PMID: 23898239 PMCID: PMC3722514 DOI: 10.3389/fncel.2013.00117] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 07/05/2013] [Indexed: 01/08/2023] Open
Abstract
Last evidences suggest that, in Alzheimer's disease (AD) early stage, Amyloid-β (Aβ) peptide induces an imbalance between excitatory and inhibitory neurotransmission systems resulting in the functional impairment of neural networks. Such alterations are particularly important in the septohippocampal system where learning and memory processes take place depending on accurate oscillatory activity tuned at fimbria-CA3 synapse. Here, the acute effects of Aβ on CA3 pyramidal neurons and their synaptic activation from septal part of the fimbria were studied in rats. A triphasic postsynaptic response defined by an excitatory potential (EPSP) followed by both early and late inhibitory potentials (IPSP) was evoked. The EPSP was glutamatergic acting on ionotropic receptors. The early IPSP was blocked by GABAA antagonists whereas the late IPSP was removed by GABAB antagonists. Aβ perfusion induced recorded cells to depolarize, increase their input resistance and decrease the late IPSP. Aβ action mechanism was localized at postsynaptic level and most likely linked to GABAB-related ion channels conductance decrease. In addition, it was found that the specific pharmacological modulation of the GABAB receptor effector, G-protein-coupled inward rectifier potassium (GirK) channels, mimicked all Aβ effects previously described. Thus, our findings suggest that Aβ altering GirK channels conductance in CA3 pyramidal neurons might have a key role in the septohippocampal activity dysfunction observed in AD.
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Affiliation(s)
- Mauricio O Nava-Mesa
- Laboratorio Neurofisiología y Comportamiento, Facultad de Medicina de Ciudad Real, Universidad de Castilla-La Mancha Ciudad Real, Spain ; Department of Fisiología y Farmacología, Universidad de Salamanca Salamanca, Spain
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Fajardo-Serrano A, Wydeven N, Young D, Watanabe M, Shigemoto R, Martemyanov KA, Wickman K, Luján R. Association of Rgs7/Gβ5 complexes with Girk channels and GABAB receptors in hippocampal CA1 pyramidal neurons. Hippocampus 2013; 23:1231-45. [PMID: 23804514 DOI: 10.1002/hipo.22161] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2013] [Indexed: 12/15/2022]
Abstract
In the hippocampus, signaling through G protein-coupled receptors is modulated by Regulators of G protein signaling (Rgs) proteins, which act to stimulate the rate of GTP hydrolysis, and consequently, G protein inactivation. The R7-Rgs subfamily selectively deactivates the G(i/o)-class of Gα subunits that mediate the action of several GPCRs. Here, we used co-immunoprecipitation, electrophysiology and immunoelectron microscopy techniques to investigate the formation of macromolecular complexes and spatial relationship of Rgs7/Gβ5 complexes and its prototypical signaling partners, the GABAB receptor and Girk channel. Co-expression of recombinant GABAB receptors and Girk channels in combination with co-immunoprecipitation experiments established that the Rgs7/Gβ5 forms complexes with GABAB receptors or Girk channels. Using electrophysiological experiments, we found that GABAB -Girk current deactivation kinetics was markedly faster in cells coexpressing Rgs7/Gβ5. At the electron microscopic level, immunolabeling for Rgs7 and Gβ5 proteins was found primarily in the dendritic layers of the hippocampus and showed similar distribution patterns. Immunoreactivity was mostly localized along the extrasynaptic plasma membrane of dendritic shafts and spines of pyramidal cells and, to a lesser extent, to that of presynaptic terminals. Quantitative analysis of immunogold particles for Rgs7 and Gβ5 revealed an enrichment of the two proteins around excitatory synapses on dendritic spines, virtually identical to that of Girk2 and GABAB1 . These data support the existence of macromolecular complexes composed of GABAB receptor-G protein-Rgs7-Girk channels in which Rgs7 and Gβ5 proteins may preferentialy modulate GABAB receptor signaling through the deactivation of Girk channels on dendritic spines. In contrast, Rgs7 and Girk2 were associated but mainly segregated from GABAB1 in dendritic shafts, where Rgs7/Gβ5 signaling complexes might modulate Girk-dependent signaling via a different metabotropic receptor(s).
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Affiliation(s)
- Ana Fajardo-Serrano
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006, Albacete, Spain
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Differential GABAB-receptor-mediated effects in perisomatic- and dendrite-targeting parvalbumin interneurons. J Neurosci 2013; 33:7961-74. [PMID: 23637187 DOI: 10.1523/jneurosci.1186-12.2013] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Inhibitory parvalbumin-containing interneurons (PVIs) control neuronal discharge and support the generation of theta- and gamma-frequency oscillations in cortical networks. Fast GABAergic input onto PVIs is crucial for their synchronization and oscillatory entrainment, but the role of metabotropic GABA(B) receptors (GABA(B)Rs) in mediating slow presynaptic and postsynaptic inhibition remains unknown. In this study, we have combined high-resolution immunoelectron microscopy, whole-cell patch-clamp recording, and computational modeling to investigate the subcellular distribution and effects of GABA(B)Rs and their postsynaptic effector Kir3 channels in rat hippocampal PVIs. Pre-embedding immunogold labeling revealed that the receptors and channels localize at high levels to the extrasynaptic membrane of parvalbumin-immunoreactive dendrites. Immunoreactivity for GABA(B)Rs was also present at lower levels on PVI axon terminals. Whole-cell recordings further showed that synaptically released GABA in response to extracellular stimulation evokes large GABA(B)R-mediated slow IPSCs in perisomatic-targeting (PT) PVIs, but only small or no currents in dendrite-targeting (DT) PVIs. In contrast, paired recordings demonstrated that GABA(B)R activation results in presynaptic inhibition at the output synapses of both PT and DT PVIs, but more strongly in the latter. Finally, computational analysis indicated that GABA(B) IPSCs can phasically modulate the discharge of PT interneurons at theta frequencies. In summary, our results show that GABA(B)Rs differentially mediate slow presynaptic and postsynaptic inhibition in PVIs and can contribute to the dynamic modulation of their activity during oscillations. Furthermore, these data provide evidence for a compartment-specific molecular divergence of hippocampal PVI subtypes, suggesting that activation of GABA(B)Rs may shift the balance between perisomatic and dendritic inhibition.
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Cortical excitability changes correlate with fluctuations in glucose levels in patients with epilepsy. Epilepsy Behav 2013; 27:455-60. [PMID: 23603690 DOI: 10.1016/j.yebeh.2013.03.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 03/09/2013] [Accepted: 03/16/2013] [Indexed: 11/21/2022]
Abstract
OBJECTIVE We used transcranial magnetic stimulation (TMS) to investigate motor cortical excitability changes in relation to blood glucose levels. METHODS Twenty-two drug-naïve patients with epilepsy [11 generalized and 11 focal] and 10 controls were studied twice on the same day; first after 12h of fasting and then 2h postprandial. Motor threshold and paired-pulse TMS at a number of short and long interstimulus intervals were measured. Serum glucose levels were measured each time. RESULTS Decreased long intracortical inhibition was seen in patients and controls during fasting compared to postprandial studies. This effect was much more prominent in patients with generalized epilepsy (with effect sizes of up to 0.8) in whom there was also evidence of increased intracortical facilitation (effect size: 0.3). CONCLUSION Cortical excitability varies with fluctuations in blood glucose levels. This variation is more prominent in patients with epilepsy. Decreased glucose levels may be an important physiological seizure trigger.
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Differential development of tolerance to the functional and behavioral effects of repeated baclofen treatment in rats. Pharmacol Biochem Behav 2013; 106:27-32. [PMID: 23500188 DOI: 10.1016/j.pbb.2013.03.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/27/2013] [Accepted: 03/02/2013] [Indexed: 11/21/2022]
Abstract
Baclofen, a gamma-aminobutyric acid (GABA)B receptor agonist, has been used clinically to treat muscle spasticity, rigidity and pain. More recently, interest in the use of baclofen as an addiction medicine has grown, with promising preclinical cocaine and amphetamine data and demonstrated clinical benefit from alcohol and nicotine studies. Few preclinical investigations, however, have utilized chronic dosing of baclofen, which is important given that tolerance can occur to many of its effects. Thus the question of whether chronic treatment of baclofen maintains the efficacy of acute doses is imperative. The neural substrates that underlie the effects of baclofen, particularly those after chronic treatment, are also not known. In the present study, therefore, rats were treated with either a) vehicle, b) acute baclofen (5 mg/kg) or c) chronic baclofen (5 mg/kg, t.i.d. for 5 days). The effects of acute and chronic baclofen administration, compared to vehicle, were assessed using locomotor activity and changes in brain glucose metabolism (a measure of functional brain activity). Acute baclofen significantly reduced locomotor activity (horizontal and total distance traveled), while chronic baclofen failed to affect locomotor activity. Acute baclofen resulted in significantly lower rates of local cerebral glucose utilization throughout many areas of the brain, including the prefrontal cortex, caudate putamen, septum and hippocampus. The majority of these functional effects, with the exception of the caudate putamen and septum, were absent in animals chronically treated with baclofen. Despite the tolerance to the locomotor and functional effects of baclofen following repeated treatment, these persistent effects on functional activity in the caudate putamen and septum may provide insights into the way in which baclofen alters the reinforcing effects of abused substances such as cocaine, alcohol, and methamphetamine both in humans and animal models.
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Nakamura A, Yoshino M. A novel GABAergic action mediated by functional coupling between GABAB-like receptor and two different high-conductance K+ channels in cricket Kenyon cells. J Neurophysiol 2013; 109:1735-45. [PMID: 23303861 DOI: 10.1152/jn.00915.2012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The γ-aminobutyric acid type B (GABA(B)) receptor has been shown to attenuate high-voltage-activated Ca(2+) currents and enhance voltage-dependent or inwardly rectifying K(+) currents in a variety of neurons. In this study, we report a novel coupling of GABA(B)-like receptor with two different high-conductance K(+) channels, Na(+)-activated K(+) (K(Na)) channel and Ca(2+)-activated K(+) (K(Ca)) channel, in Kenyon cells isolated from the mushroom body of the cricket brain. Single-channel activities of K(Na) and K(Ca) channels in response to bath applications of GABA and the GABA(B)-specific agonist SKF97541 were recorded with the cell-attached patch configuration. The open probability (P(o)) of both K(Na) and K(Ca) channels was found to be increased by bath application of GABA, and this increase in Po was antagonized by coapplication of the GABAB antagonist CGP54626, suggesting that GABA(B)-like receptors mediate these actions. Similarly, GABA(B)-specific agonist SKF97541 increased the Po of both K(Na) and K(Ca) channels. Perforated-patch recordings using β-escin further revealed that SKF97541 increased the amplitude of the outward currents elicited by step depolarizations. Under current-clamp conditions, SKF97541 decreased the firing frequency of spontaneous action potential (AP) and changed the AP waveform. The amplitude and duration of AP were decreased, whereas the afterhyperpolarization of AP was increased. Resting membrane potential, however, was not significantly altered by SKF97541. Taken together, these results suggest that GABA(B)-like receptor is functionally coupled with both K(Na) and K(Ca) channels and this coupling mechanism may serve to prevent AP formation and limit excitatory synaptic input.
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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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Jiang X, Su L, Zhang Q, He C, Zhang Z, Yi P, Liu J. GABAB receptor complex as a potential target for tumor therapy. J Histochem Cytochem 2012; 60:269-79. [PMID: 22266766 DOI: 10.1369/0022155412438105] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate central nervous system. Metabotropic GABA(B) receptors are heterodimeric G-protein-coupled receptors (GPCRs) consisting of GABA(B1) and GABA(B2) subunits. The intracellular C-terminal domains of GABA(B) receptors are involved in heterodimerization, oligomerization, and association with other proteins, which results in a large receptor complex. Multiple splice variants of the GABA(B1) subunit have been identified in which GABA(B1a) and GABA(B1b) are the most abundant isoforms in the nervous system. Isoforms GABA(B1c) through GABA(B1n) are minor isoforms and are detectable only at mRNA levels. Some of the minor isoforms have been detected in peripheral tissues and encode putative soluble proteins with C-terminal truncations. Interestingly, increased expression of GABA(B) receptors has been detected in several human cancer cells and tissues. Moreover, GABA(B) receptor agonist baclofen inhibited tumor growth in rat models. GABA(B) receptor activation not only induces suppressing the proliferation and migration of various human tumor cells but also results in inactivation of CREB (cAMP-responsive element binding protein) and ERK in tumor cells. Their structural complexity makes it possible to disrupt the functions of GABA(B) receptors in various ways, raising GABA(B) receptor diversity as a potential therapeutic target in some human cancers.
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Affiliation(s)
- Xinnong Jiang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, P. R. China.
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Enoch MA, Zhou Z, Kimura M, Mash DC, Yuan Q, Goldman D. GABAergic gene expression in postmortem hippocampus from alcoholics and cocaine addicts; corresponding findings in alcohol-naïve P and NP rats. PLoS One 2012; 7:e29369. [PMID: 22253714 PMCID: PMC3258238 DOI: 10.1371/journal.pone.0029369] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 11/27/2011] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND By performing identical studies in humans and rats, we attempted to distinguish vulnerability factors for addiction from neurobiological effects of chronic drug exposure. We focused on the GABAergic system within the hippocampus, a brain region that is a constituent of the memory/conditioning neuronal circuitry of addiction that is considered to be important in drug reinforcement behaviors in animals and craving and relapse in humans. METHODOLOGY Using RNA-Seq we quantified mRNA transcripts in postmortem total hippocampus from alcoholics, cocaine addicts and controls and also from alcohol-naïve, alcohol preferring (P) and non-preferring (NP) rats selectively bred for extremes of alcohol-seeking behavior that also show a general addictive tendency. A pathway-targeted analysis of 25 GABAergic genes encoding proteins implicated in GABA synthesis, metabolism, synaptic transmission and re-uptake was undertaken. PRINCIPAL FINDINGS Directionally consistent and biologically plausible overlapping and specific changes were detected: 14/25 of the human genes and 12/25 of the rat genes showed nominally significant differences in gene expression (global p values: 9×10⁻¹⁴, 7×10⁻¹¹ respectively). Principal FDR-corrected findings were that GABBR1 was down-regulated in alcoholics, cocaine addicts and P rats with congruent findings in NSF, implicated in GABAB signaling efficacy, potentially resulting in increased synaptic GABA. GABRG2, encoding the gamma2 subunit required for postsynaptic clustering of GABAA receptors together with GPHN, encoding the associated scaffolding protein gephryin, were both down-regulated in alcoholics and cocaine addicts but were both up-regulated in P rats. There were also expression changes specific to cocaine addicts (GAD1, GAD2), alcoholics (GABRA2) and P rats (ABAT, GABRG3). CONCLUSIONS/SIGNIFICANCE Our study confirms the involvement of the GABAergic system in alcoholism but also reveals a hippocampal GABA input in cocaine addiction. Congruent findings in human addicts and P rats provide clues to predisposing factors for alcohol and drug addiction. Finally, the results of this study have therapeutic implications.
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Affiliation(s)
- Mary-Anne Enoch
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, United States of America.
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37
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Shoemaker PA. Neural bistability and amplification mediated by NMDA receptors: Analysis of stationary equations. Neurocomputing 2011. [DOI: 10.1016/j.neucom.2011.04.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Mowery TM, Sarin RM, Elliott KS, E Garraghty P. Nerve injury-induced changes in GABA(A) and GABA(B) sub-unit expression in area 3b and cuneate nucleus of adult squirrel monkeys: further evidence of developmental recapitulation. Brain Res 2011; 1415:63-75. [PMID: 21880301 DOI: 10.1016/j.brainres.2011.07.066] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2011] [Revised: 07/24/2011] [Accepted: 07/30/2011] [Indexed: 11/27/2022]
Abstract
The primate somatosensory system provides an excellent model system with which to investigate adult neural plasticity. Here, we report immunohistochemical staining data for the GABA(A) α1, GABA(B)R1a, and GABA(B)R1b receptor subunits in somatosensory area 3b, and cuneate nucleus one week after median nerve compression in adult squirrel monkeys. We find a significant decrease in GABA(A) α1 subunit staining across all cortical layers and within both soma and neuropil of the deprived cortical and brainstem regions. The GABA(B) staining showed an opposing shift in deprived regions, with a significant increase in presynaptic GABA(B)R1a staining, and a significant decrease in postsynaptic GABA(B)R1b staining in deprived regions of the cortex and brainstem. These changes in receptor subunit expression generate patterns that are very similar to those reported in the neonate. Furthermore, the similarities between brainstem and cortical expression suggest conserved forms of adult plasticity in these two regions. Taken together these results, along with the results from our previous paper investigating AMPA subunit expression in these same animals, support the hypothesis that deprived neurons enter a previously hidden state of developmental recapitulation that serves to prime the brain for NMDA receptor mediated receptive field reorganization.
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Affiliation(s)
- Todd M Mowery
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, Hershey, PA 17033, USA.
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Luo J, Becnel J, Nichols CD, Nässel DR. Insulin-producing cells in the brain of adult Drosophila are regulated by the serotonin 5-HT1A receptor. Cell Mol Life Sci 2011; 69:471-84. [PMID: 21818550 DOI: 10.1007/s00018-011-0789-0] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 07/01/2011] [Accepted: 07/25/2011] [Indexed: 12/20/2022]
Abstract
Insulin signaling regulates lifespan, reproduction, metabolic homeostasis, and resistance to stress in the adult organism. In Drosophila, there are seven insulin-like peptides (DILP1-7). Three of these (DILP2, 3 and 5) are produced in median neurosecretory cells of the brain, designated IPCs. Previous work has suggested that production or release of DILPs in IPCs can be regulated by a factor secreted from the fat body as well as by neuronal GABA or short neuropeptide F. There is also evidence that serotonergic neurons may regulate IPCs. Here, we investigated mechanisms by which serotonin may regulate the IPCs. We show that the IPCs in adult flies express the 5-HT(1A), but not the 5-HT(1B) or 5-HT(7) receptors, and that processes of serotonergic neurons impinge on the IPC branches. Knockdown of 5-HT(1A) in IPCs by targeted RNA interference (RNAi) leads to increased sensitivity to heat, prolonged recovery after cold knockdown and decreased resistance to starvation. Lipid metabolism is also affected, but no effect on growth was seen. Furthermore, we show that DILP2-immunolevels in IPCs increase after 5-HT(1A) knockdown; this is accentuated by starvation. Heterozygous 5-HT(1A) mutant flies display the same phenotype in all assays, as seen after targeted 5-HT(1A) RNAi, and flies fed the 5-HT(1A) antagonist WAY100635 display reduced lifespan at starvation. Our findings suggest that serotonin acts on brain IPCs via the 5-HT(1A) receptor, thereby affecting their activity and probably insulin signaling. Thus, we have identified a second inhibitory pathway regulating IPC activity in the Drosophila brain.
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Affiliation(s)
- Jiangnan Luo
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, 10691 Stockholm, Sweden
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Contribution of metabotropic GABA(B) receptors to neuronal network construction. Pharmacol Ther 2011; 132:170-9. [PMID: 21718720 DOI: 10.1016/j.pharmthera.2011.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 06/08/2011] [Indexed: 01/05/2023]
Abstract
In the 1980s, Bowery and colleagues discovered the presence of a novel, bicuculline-resistant and baclofen-sensitive type of GABA receptor on peripheral nerve terminals, the GABA(B) receptor. Since this pioneering work, GABA(B) receptors have been identified in the Central Nervous System (CNS), where they provide an important inhibitory control of postsynaptic excitability and presynaptic transmitter release. GABA(B) receptors have been implicated in a number of important processes in the adult brain such as the regulation of synaptic plasticity and modulation of rhythmic activity. As a result of these studies, several potential therapeutic applications of GABA(B) receptor ligands have been identified. Recent advances have further shown that GABA(B) receptors play more than a classical inhibitory role in adult neurotransmission, and can in fact function as an important developmental signal early in life. Here we summarize current knowledge on the contribution of GABA(B) receptors to the construction and function of developing neuronal networks.
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Metz M, Gassmann M, Fakler B, Schaeren-Wiemers N, Bettler B. Distribution of the auxiliary GABAB receptor subunits KCTD8, 12, 12b, and 16 in the mouse brain. J Comp Neurol 2011; 519:1435-54. [DOI: 10.1002/cne.22610] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Ciruela F, Vallano A, Arnau JM, Sánchez S, Borroto-Escuela DO, Agnati LF, Fuxe K, Fernández-Dueñas V. G protein-coupled receptor oligomerization for what? J Recept Signal Transduct Res 2011; 30:322-30. [PMID: 20718634 DOI: 10.3109/10799893.2010.508166] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Although the G protein-coupled receptor (GPCR) oligomerization has been questioned during the last decade, under some premises the existence of a supramolecular organization of these receptors begins now to be widely accepted by the scientific community. Indeed, GPCR oligomers may enhance the diversity and performance by which extracellular signals are transferred to the G proteins in the process of receptor transduction, although the mechanism that underlie this phenomenon remains still unexplained. Recently, a trans-conformational switching model has been proposed as a mechanism allowing direct inhibition of receptor activation. Thus, heterotropic receptor-receptor allosteric regulations are behind the GPCR oligomeric function. Accordingly, we revise here how GPCR oligomerization impinge in several important receptor functions like biosynthesis, plasma membrane diffusion or velocity, pharmacology and signaling. Overall, the rationale of receptor oligomerization might lie in the cellular need of sensing complex extracellular signals and to translate into a simple computational mode.
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Affiliation(s)
- Francisco Ciruela
- Unitat de Farmacologia, Departament de Patologia i Terapèutica Experimental, Facultat de Medicina, IDIBELL-Universitat de Barcelona, 08907 Barcelona, Spain.
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Insulin signaling, lifespan and stress resistance are modulated by metabotropic GABA receptors on insulin producing cells in the brain of Drosophila. PLoS One 2010; 5:e15780. [PMID: 21209905 PMCID: PMC3012717 DOI: 10.1371/journal.pone.0015780] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 11/24/2010] [Indexed: 12/17/2022] Open
Abstract
Insulin-like peptides (ILPs) regulate growth, reproduction, metabolic homeostasis, life span and stress resistance in worms, flies and mammals. A set of insulin producing cells (IPCs) in the Drosophila brain that express three ILPs (DILP2, 3 and 5) have been the main focus of interest in hormonal DILP signaling. Little is, however, known about factors that regulate DILP production and release by these IPCs. Here we show that the IPCs express the metabotropic GABAB receptor (GBR), but not the ionotropic GABAA receptor subunit RDL. Diminishing the GBR expression on these cells by targeted RNA interference abbreviates life span, decreases metabolic stress resistance and alters carbohydrate and lipid metabolism at stress, but not growth in Drosophila. A direct effect of diminishing GBR on IPCs is an increase in DILP immunofluorescence in these cells, an effect that is accentuated at starvation. Knockdown of irk3, possibly part of a G protein-activated inwardly rectifying K+ channel that may link to GBRs, phenocopies GBR knockdown in starvation experiments. Our experiments suggest that the GBR is involved in inhibitory control of DILP production and release in adult flies at metabolic stress and that this receptor mediates a GABA signal from brain interneurons that may convey nutritional signals. This is the first demonstration of a neurotransmitter that inhibits insulin signaling in its regulation of metabolism, stress and life span in an invertebrate brain.
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Song Y, Slaughter MM. GABA(B) receptor feedback regulation of bipolar cell transmitter release. J Physiol 2010; 588:4937-49. [PMID: 20974680 DOI: 10.1113/jphysiol.2010.194233] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
GABAergic amacrine cell feedback to bipolar cells in retina has been described, activating both GABA(A) and GABA(C) receptors. We explored whether metabotropic GABA(B) receptors also participate in this feedback pathway. CGP55845, a potent GABA(B) receptor antagonist, was employed to determine the endogenous role of these receptors. Ganglion cell EPSCs and IPSCs were monitored to measure the output of bipolar and amacrine cells. Using the tiger salamander slice preparation, we found that GABA(B) receptor pathways regulate bipolar cell release directly and indirectly. In the direct pathway, the GABA(B) receptor antagonist reduces EPSC amplitude, indicating that GABA(B) receptors cause enhanced glutamate release from bipolar cells to one set of ganglion cells. In the indirect pathway, the GABA(B) receptor antagonist reduces EPSC amplitude in another set of ganglion cells. The indirect pathway is only evident when GABA(A) receptors are inhibited, and is blocked by a glycine receptor antagonist. Thus, this second feedback pathway involves direct glycine feedback to the bipolar cell and this glycinergic amacrine cell is suppressed by GABAergic amacrine cells, through both GABA(A) and GABA(B) but not GABA(C) receptors. Overall, GABA(B) receptors do contribute to feedback regulation of bipolar cell transmitter release. However, unlike the ionotropic GABA receptor pathways, the metabotropic GABA receptor pathways act to enhance bipolar cell transmitter release. Furthermore, there are three discrete subsets of bipolar cell output regulated by GABA(B) receptor feedback (direct, indirect and null), implying three distinct, non-overlapping bipolar cell to ganglion cell circuits.
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Affiliation(s)
- Yunbo Song
- Department of Physiology & Biophysics, Center for Neuroscience, 124 Sherman Hall, 3435 Main Street, Buffalo, NY 14214, USA.
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Ciruela F, Fernández-Dueñas V, Sahlholm K, Fernández-Alacid L, Nicolau JC, Watanabe M, Luján R. Evidence for oligomerization between GABAB receptors and GIRK channels containing the GIRK1 and GIRK3 subunits. Eur J Neurosci 2010; 32:1265-77. [PMID: 20846323 DOI: 10.1111/j.1460-9568.2010.07356.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The stimulation of inhibitory neurotransmitter receptors, such as γ-aminobutyric acid type B (GABA(B) ) receptors, activates G protein-gated inwardly-rectifying K(+) (GIRK) channels, which influence membrane excitability. There is now evidence suggesting that G protein-coupled receptors and G protein-gated inwardly-rectifying K(+) [GIRK/family 3 of inwardly-rectifying K(+) (Kir3)] channels do not diffuse freely within the plasma membrane, but instead there are direct protein-protein interactions between them. Here, we used bioluminescence resonance energy transfer, co-immunoprecipitation, confocal and electron microscopy techniques to investigate the oligomerization of GABA(B) receptors with GIRK channels containing the GIRK3 subunit, whose contribution to functional channels is still unresolved. Co-expression of GABA(B) receptors and GIRK channels in human embryonic kidney-293 cells in combination with co-immunoprecipitation experiments established that the metabotropic receptor forms stable complexes with GIRK channels. Using bioluminescence resonance energy transfer, we have shown that, in living cells under physiological conditions, GABA(B) receptors interact directly with GIRK1/GIRK3 heterotetramers. In addition, we have provided evidence that the receptor-effector complexes are also found in vivo and identified that the cerebellar granule cells are one neuron population where the interaction probably takes place. Altogether, our data show that signalling complexes containing GABA(B) receptors and GIRK channels are formed shortly after biosynthesis, probably in the endoplasmic reticulum and/or endoplasmic reticulum/Golgi apparatus complex, suggesting that this might be a general feature of receptor-effector ion channel signal transduction and supporting a channel-forming role for the GIRK3 subunit.
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Affiliation(s)
- Francisco Ciruela
- Unitat de Farmacologia (4102), Departament Patologia i Terapèutica Experimental, Facultat de Medicina-Bellvitge, Universitat de IDIBELL-Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain.
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Abstract
Autism is a behaviorally defined neurodevelopmental disorder and among its symptoms are disturbances in face and emotional processing. Emerging evidence demonstrates abnormalities in the GABAergic (gamma-aminobutyric acid) system in autism, which likely contributes to these deficits. GABA(B) receptors play an important role in modulating synapses and maintaining the balance of excitation-inhibition in the brain. The density of GABA(B) receptors in subjects with autism and matched controls was quantified in the anterior and posterior cingulate cortex, important for socio-emotional and cognitive processing, and the fusiform gyrus, important for identification of faces and facial expressions. Significant reductions in GABA(B) receptor density were demonstrated in all three regions examined suggesting that alterations in this key inhibitory receptor subtype may contribute to the functional deficits in individuals with autism. Interestingly, the presence of seizure in a subset of autism cases did not have a significant effect on the density of GABA(B) receptors in any of the three regions.
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Affiliation(s)
- Adrian L Oblak
- Department of Anatomy and Neurobiology, Laboratory of Autism Neuroscience Research, Boston University School of Medicine, Boston, MA 02118, USA.
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Ishii H, Nakajo K, Yanagawa Y, Kubo Y. Identification and characterization of Cs+-permeable K+ channel current in mouse cerebellar Purkinje cells in lobules 9 and 10 evoked by molecular layer stimulation. Eur J Neurosci 2010; 32:736-48. [DOI: 10.1111/j.1460-9568.2010.07336.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Cash RFH, Ziemann U, Murray K, Thickbroom GW. Late Cortical Disinhibition in Human Motor Cortex: A Triple-Pulse Transcranial Magnetic Stimulation Study. J Neurophysiol 2010; 103:511-8. [DOI: 10.1152/jn.00782.2009] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In human motor cortex transcranial magnetic stimulation (TMS) has been used to identify short-interval intracortical inhibition (SICI) corresponding to γ-aminobutyric acid type A (GABAA) effects and long-interval intracortical inhibition (LICI) and the cortical silent period (SP) corresponding to postsynaptic GABAB effects. Presynaptic GABAB effects, corresponding to disinhibition, can also be identified with TMS and have been shown to be acting during LICI by measuring SICI after a suprathreshold priming stimulus (PS). The duration of disinhibition is not certain and, guided by studies in experimental preparations, we hypothesized that it may be longer-lasting than postsynaptic inhibition, leading to a period of late cortical disinhibition and consequently a net increase in corticospinal excitability. We tested this first by measuring the motor-evoked potential (MEP) to a test stimulus (TS), delivered after a PS at interpulse intervals (IPIs) ≤300 ms that encompassed the period of PS-induced LICI and its aftermath. MEP amplitude was initially decreased, but then increased at IPIs of 190–210 ms, reaching 160 ± 17% of baseline 200 ms after PS ( P < 0.05). SP duration was 181 ± 5 ms. A second experiment established that the onset of the later period of increased excitability correlated with PS intensity ( r2 = 0.99) and with the duration of the SP ( r2 = 0.99). The third and main experiment demonstrated that SICI was significantly reduced in strength at all IPIs ≤220 ms after PS. We conclude that TMS-induced LICI is associated with a period of disinhibition that is at first masked by LICI, but that outlasts LICI and gives rise to a period during which disinhibition predominates and net excitability is raised. Identification of this late period of disinhibition in human motor cortex may provide an opportunity to explore or modulate the behavior of excitatory networks at a time when inhibitory effects are restrained.
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Affiliation(s)
- R. F. H. Cash
- Centre for Neuromuscular and Neurological Disorders and
| | - U. Ziemann
- Department of Neurology, Goethe-University of Frankfurt, Frankfurt, Germany/
| | - K. Murray
- School of Mathematics and Statistics, University of Western Australia, Crawley, Perth, Australia; and
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Brennan PM, Whittle IR. Intrathecal baclofen therapy for neurological disorders: a sound knowledge base but many challenges remain. Br J Neurosurg 2009; 22:508-19. [DOI: 10.1080/02688690802233364] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Fernández-Alacid L, Aguado C, Ciruela F, Martín R, Colón J, Cabañero MJ, Gassmann M, Watanabe M, Shigemoto R, Wickman K, Bettler B, Sánchez-Prieto J, Luján R. Subcellular compartment-specific molecular diversity of pre- and post-synaptic GABA-activated GIRK channels in Purkinje cells. J Neurochem 2009; 110:1363-76. [PMID: 19558451 DOI: 10.1111/j.1471-4159.2009.06229.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Activation of G protein-gated inwardly-rectifying K(+) (GIRK or Kir3) channels by metabotropic gamma-aminobutyric acid (B) (GABA(B)) receptors is an essential signalling pathway controlling neuronal excitability and synaptic transmission in the brain. To investigate the relationship between GIRK channel subunits and GABA(B) receptors in cerebellar Purkinje cells at post- and pre-synaptic sites, we used biochemical, functional and immunohistochemical techniques. Co-immunoprecipitation analysis demonstrated that GIRK subunits are co-assembled with GABA(B) receptors in the cerebellum. Immunoelectron microscopy showed that the subunit composition of GIRK channels in Purkinje cell spines is compartment-dependent. Thus, at extrasynaptic sites GIRK channels are formed by GIRK1/GIRK2/GIRK3, post-synaptic densities contain GIRK2/GIRK3 and dendritic shafts contain GIRK1/GIRK3. The post-synaptic association of GIRK subunits with GABA(B) receptors in Purkinje cells is supported by the subcellular regulation of the ion channel and the receptor in mutant mice. At pre-synaptic sites, GIRK channels localized to parallel fibre terminals are formed by GIRK1/GIRK2/GIRK3 and co-localize with GABA(B) receptors. Consistent with this morphological evidence we demonstrate their functional interaction at axon terminals in the cerebellum by showing that GIRK channels play a role in the inhibition of glutamate release by GABA(B) receptors. The association of GIRK channels and GABA(B) receptors with excitatory synapses at both post- and pre-synaptic sites indicates their intimate involvement in the modulation of glutamatergic neurotransmission in the cerebellum.
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Affiliation(s)
- Laura Fernández-Alacid
- Departamento de Ciencias Médicas, CRIB-Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
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