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Joglekar A, Hu W, Zhang B, Narykov O, Diekhans M, Marrocco J, Balacco J, Ndhlovu LC, Milner TA, Fedrigo O, Jarvis ED, Sheynkman G, Korkin D, Ross ME, Tilgner HU. Single-cell long-read sequencing-based mapping reveals specialized splicing patterns in developing and adult mouse and human brain. Nat Neurosci 2024; 27:1051-1063. [PMID: 38594596 PMCID: PMC11156538 DOI: 10.1038/s41593-024-01616-4] [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: 04/22/2023] [Accepted: 03/07/2024] [Indexed: 04/11/2024]
Abstract
RNA isoforms influence cell identity and function. However, a comprehensive brain isoform map was lacking. We analyze single-cell RNA isoforms across brain regions, cell subtypes, developmental time points and species. For 72% of genes, full-length isoform expression varies along one or more axes. Splicing, transcription start and polyadenylation sites vary strongly between cell types, influence protein architecture and associate with disease-linked variation. Additionally, neurotransmitter transport and synapse turnover genes harbor cell-type variability across anatomical regions. Regulation of cell-type-specific splicing is pronounced in the postnatal day 21-to-postnatal day 28 adolescent transition. Developmental isoform regulation is stronger than regional regulation for the same cell type. Cell-type-specific isoform regulation in mice is mostly maintained in the human hippocampus, allowing extrapolation to the human brain. Conversely, the human brain harbors additional cell-type specificity, suggesting gain-of-function isoforms. Together, this detailed single-cell atlas of full-length isoform regulation across development, anatomical regions and species reveals an unappreciated degree of isoform variability across multiple axes.
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Affiliation(s)
- Anoushka Joglekar
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
- New York Genome Center, New York, NY, USA
| | - Wen Hu
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
| | - Bei Zhang
- Spatial Genomics, Inc., Pasadena, CA, USA
| | - Oleksandr Narykov
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA
- Computer Science Department, Worcester Polytechnic Institute, Worcester, MA, USA
- Data Science Program, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Mark Diekhans
- UC Genomics Institute, University of California, Santa Cruz, Santa Cruz, CA, USA
| | - Jordan Marrocco
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Department of Biology, Touro University, New York, NY, USA
- Laboratory of Neuroendocrinology, The Rockefeller University, New York, NY, USA
| | - Jennifer Balacco
- Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA
| | - Lishomwa C Ndhlovu
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Department of Medicine, Division of Infectious Diseases, Weill Cornell Medicine, New York, NY, USA
| | - Teresa A Milner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Olivier Fedrigo
- Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA
| | - Erich D Jarvis
- Vertebrate Genome Lab, The Rockefeller University, New York, NY, USA
- Laboratory of Neurogenetics of Language, The Rockefeller University, New York, NY, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
| | - Gloria Sheynkman
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA, USA
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
- Center for Public Health Genomics, University of Virginia, Charlottesville, VA, USA
- UVA Comprehensive Cancer Center, University of Virginia, Charlottesville, VA, USA
| | - Dmitry Korkin
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA
- Computer Science Department, Worcester Polytechnic Institute, Worcester, MA, USA
- Data Science Program, Worcester Polytechnic Institute, Worcester, MA, USA
| | - M Elizabeth Ross
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
| | - Hagen U Tilgner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA.
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA.
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2
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Joglekar A, Hu W, Zhang B, Narykov O, Diekhans M, Balacco J, Ndhlovu LC, Milner TA, Fedrigo O, Jarvis ED, Sheynkman G, Korkin D, Ross ME, Tilgner HU. Single-cell long-read mRNA isoform regulation is pervasive across mammalian brain regions, cell types, and development. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.02.535281. [PMID: 37066387 PMCID: PMC10103983 DOI: 10.1101/2023.04.02.535281] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
RNA isoforms influence cell identity and function. Until recently, technological limitations prevented a genome-wide appraisal of isoform influence on cell identity in various parts of the brain. Using enhanced long-read single-cell isoform sequencing, we comprehensively analyze RNA isoforms in multiple mouse brain regions, cell subtypes, and developmental timepoints from postnatal day 14 (P14) to adult (P56). For 75% of genes, full-length isoform expression varies along one or more axes of phenotypic origin, underscoring the pervasiveness of isoform regulation across multiple scales. As expected, splicing varies strongly between cell types. However, certain gene classes including neurotransmitter release and reuptake as well as synapse turnover, harbor significant variability in the same cell type across anatomical regions, suggesting differences in network activity may influence cell-type identity. Glial brain-region specificity in isoform expression includes strong poly(A)-site regulation, whereas neurons have stronger TSS regulation. Furthermore, developmental patterns of cell-type specific splicing are especially pronounced in the murine adolescent transition from P21 to P28. The same cell type traced across development shows more isoform variability than across adult anatomical regions, indicating a coordinated modulation of functional programs dictating neural development. As most cell-type specific exons in P56 mouse hippocampus behave similarly in newly generated data from human hippocampi, these principles may be extrapolated to human brain. However, human brains have evolved additional cell-type specificity in splicing, suggesting gain-of-function isoforms. Taken together, we present a detailed single-cell atlas of full-length brain isoform regulation across development and anatomical regions, providing a previously unappreciated degree of isoform variability across multiple scales of the brain.
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Affiliation(s)
- Anoushka Joglekar
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
| | - Wen Hu
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
| | | | - Oleksandr Narykov
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA
- Computer Science Department, Worcester Polytechnic Institute, Worcester, MA, USA
- Data Science Program, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Mark Diekhans
- UC Santa Cruz Genomics Institute, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
| | | | - Lishomwa C Ndhlovu
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Department of Medicine, Division of Infectious Diseases, Weill Cornell Medicine, New York, NY, USA
| | - Teresa A Milner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
| | - Olivier Fedrigo
- Vertebrate Genome Lab, the Rockefeller University, New York, NY
| | - Erich D Jarvis
- Vertebrate Genome Lab, the Rockefeller University, New York, NY
- Laboratory of Neurogenetics of Language, the Rockefeller University, New York, NY
- Howard Hughes Medical Institute, Chevy Chase, MD
| | - Gloria Sheynkman
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia, USA
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, VA, USA
- Center for Public Health Genomics, University of Virginia, Charlottesville, VA, USA
- UVA Comprehensive Cancer Center, University of Virginia, Charlottesville, Virginia, USA
| | - Dmitry Korkin
- Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, MA, USA
- Computer Science Department, Worcester Polytechnic Institute, Worcester, MA, USA
- Data Science Program, Worcester Polytechnic Institute, Worcester, MA, USA
| | - M Elizabeth Ross
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
| | - Hagen U Tilgner
- Feil Family Brain and Mind Research Institute, Weill Cornell Medicine, New York, NY, USA
- Center for Neurogenetics, Weill Cornell Medicine, New York, NY, USA
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3
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Kaplanian A, Vinos M, Skaliora I. GABAb- and GABAa- mediated regulation of Up and Down states across development. J Physiol 2022; 600:2401-2427. [PMID: 35365894 DOI: 10.1113/jp282736] [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: 12/15/2021] [Accepted: 03/18/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Slow oscillations (SOs), the EEG hallmark of non-REM sleep, and their cellular counterpart, Up-and-Down states (UDSs), are considered the default activity of the cerebral cortex and reflect the underlying neural connectivity. GABAb- and GABAa- receptor-mediated inhibition play a major role in regulating UDS activity. Although SOs and UDSs exhibit significant alterations as a function of age, it is unknown how developmental changes in inhibition contribute to the developmental profile of this activity. In this study, we reveal for the first time, age-dependent effects of GABAb and GABAa signalling on UDSs. We also document the differential subunit composition of postsynaptic GABAa receptors in young and adult animals, highlighting the α1-subunit as a major component of the age-differentiated regulation of UDSs. These findings help clarify the mechanisms that underlie the maturation of cortical network activity, and enhance our understanding regarding the emergence of neurodevelopmental disorders. ABSTRACT Slow oscillations, the hallmark of non-REM sleep, and their cellular counterpart, Up-and-Down states (UDSs), are considered a signature of cortical dynamics that reflect the intrinsic network organization. Although previous studies have explored the role of inhibition in regulating UDSs, little is known about whether this role changes with maturation. This is surprising since both slow oscillations and UDSs exhibit significant age-dependent alterations. To elucidate the developmental impact of GABAb and GABAa receptors on UDS activity, we conducted simultaneous LFP and intracellular recordings ex vivo, in brain slices of young and adult male mice, using selective blockers, CGP and non-saturating concentration of gabazine, respectively. Blockade of both GABAb- and GABAa- signalling showed age-differentiated functions. CGP caused an increase in Down state duration in young animals, but a decrease in adults. Gabazine evoked Spike-and-Wave-Discharges in both ages; however, while young networks became completely epileptic, adults maintained the ability to generate UDSs. Furthermore, voltage clamp recordings of mIPSCs revealed that gabazine selectively blocks phasic currents, particularly involving postsynaptic mechanisms. The latter exhibit clear maturational changes, suggesting a different subunit composition of GABAa receptors in young vs. adult animals. Indeed, subsequent LFP recordings under diazepam (nanomolar or micromolar concentrations) revealed that mechanisms engaging the drug's classical-binding-site, mediated by α1-subunit containing GABAa receptors, have a bigger contribution in Up state initiation in young networks compared to adults. Taken together, these findings help clarify the mechanisms that underlie the maturation of cortical network activity and enhance our understanding regarding the emergence of neurodevelopmental disorders. Abstract figure legend GABAb receptors' participation in Up state termination mechanisms is well-conserved across development. However, regulation of Down-to-Up transitions is age-dependent; GABAb receptors promote them in young while preventing them in adults. Up state maintenance is determined by age-dependent synaptic GABAa receptors' subunit composition and kinetics; α1-GABAa receptors dominate in young while non-α1-GABAa receptors dominate in adults. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Ani Kaplanian
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of Biology, University of Patras, Rio, 26504, Greece
| | - Michael Vinos
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of History and Philosophy of Science, University of Athens, Athens, 15771, Greece
| | - Irini Skaliora
- Center for Basic Research, Biomedical Research Foundation of Academy of Athens (BRFAA), Athens, 11527, Greece.,Department of History and Philosophy of Science, University of Athens, Athens, 15771, Greece
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Keeping the Balance: GABAB Receptors in the Developing Brain and Beyond. Brain Sci 2022; 12:brainsci12040419. [PMID: 35447949 PMCID: PMC9031223 DOI: 10.3390/brainsci12040419] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/18/2022] [Accepted: 03/21/2022] [Indexed: 12/16/2022] Open
Abstract
The main neurotransmitter in the brain responsible for the inhibition of neuronal activity is γ-aminobutyric acid (GABA). It plays a crucial role in circuit formation during development, both via its primary effects as a neurotransmitter and also as a trophic factor. The GABAB receptors (GABABRs) are G protein-coupled metabotropic receptors; on one hand, they can influence proliferation and migration; and, on the other, they can inhibit cells by modulating the function of K+ and Ca2+ channels, doing so on a slower time scale and with a longer-lasting effect compared to ionotropic GABAA receptors. GABABRs are expressed pre- and post-synaptically, at both glutamatergic and GABAergic terminals, thus being able to shape neuronal activity, plasticity, and the balance between excitatory and inhibitory synaptic transmission in response to varying levels of extracellular GABA concentration. Furthermore, given their subunit composition and their ability to form complexes with several associated proteins, GABABRs display heterogeneity with regard to their function, which makes them a promising target for pharmacological interventions. This review will describe (i) the latest results concerning GABABRs/GABABR-complex structures, their function, and the developmental time course of their appearance and functional integration in the brain, (ii) their involvement in manifestation of various pathophysiological conditions, and (iii) the current status of preclinical and clinical studies involving GABABR-targeting drugs.
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Abstract
A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABAB receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABAB receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
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6
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Chen W, Zhang Q, Wang H, Tan D, Tan Y. Unique and independent role of the GABA B1 subunit in embryo implantation and uterine decidualization in mice. Genes Dis 2019; 8:79-86. [PMID: 33569516 PMCID: PMC7859463 DOI: 10.1016/j.gendis.2019.06.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 06/18/2019] [Accepted: 06/19/2019] [Indexed: 01/26/2023] Open
Abstract
Embryo implantation and decidualization are crucial for successful pregnancy, which include multiple genes and signaling pathways, while the precise mechanism regarding embryo implantation and decidualization has yet to be explored. The GABA which activates GABAA or GABAB receptors has been found playing an important role in early pregnancy. Here we seek to investigate whether GABAB receptors participate in embryo implantation in mice. This study first characterized the spatiotemporal expression pattern of GABAB receptors in the uterus during the peri-implantation period and found that GABAB1 expression was drastically upregulated in stromal cells on days 4–6, a period of embryo implantation and early stages of decidualization. Embryo delayed implantation and oil-induced decidualization models were further used to confirm that the GABAB1 was associated with embryo implantation and decidualization. We also found estrogen or progesterone had no directly effect on expression of GABAB1 in ovariectomized model. Because we were unable to detect significant GABAB2 which couples with GABAB1 to form whole GABAB receptors, and the agonist and antagonist of whole GABAB receptors had weak effect on the proliferation and differentiation of stromal cells as well, we excluded the possibility whole GABAB receptors function, and concluded it should be non-classical signals of GABAB1 involving in embryo implantation and decidualization. Future studies should focus on investigating the roles and mechanisms of GABAB1 during embryo implantation and decidualization.
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Affiliation(s)
- Wenhao Chen
- Laboratory Animal Center, Chongqing Medical University, Chongqing, 400016, PR China
| | - Qian Zhang
- Laboratory Animal Center, Chongqing Medical University, Chongqing, 400016, PR China
| | - Haibin Wang
- Reproductive Medical Center, The First Affiliated Hospital of Xiamen University, Xiamen, 361003, Fujian, PR China.,Fujian Provincial Key Laboratory of Reproductive Health Research, Medical College of Xiamen University, Xiamen, 361102, Fujian, PR China
| | - Dongmei Tan
- Laboratory Animal Center, Chongqing Medical University, Chongqing, 400016, PR China
| | - Yi Tan
- Laboratory Animal Center, Chongqing Medical University, Chongqing, 400016, PR China
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7
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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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8
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Cai S, Fischer QS, He Y, Zhang L, Liu H, Daw NW, Yang Y. GABAB receptor-dependent bidirectional regulation of critical period ocular dominance plasticity in cats. PLoS One 2017; 12:e0180162. [PMID: 28662175 PMCID: PMC5491141 DOI: 10.1371/journal.pone.0180162] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 06/09/2017] [Indexed: 01/05/2023] Open
Abstract
Gama amino butyric acid (GABA) inhibition plays an important role in the onset and offset of the critical period for ocular dominance (OD) plasticity in the primary visual cortex. Previous studies have focused on the involvement of GABAA receptors, while the potential contribution of GABAB receptors to OD plasticity has been neglected. In this study, the GABAB receptor antagonist SCH50911 or agonist baclofen was infused into the primary visual cortex of cats concurrently with a period of monocular deprivation (MD). Using single-unit recordings we found that the OD shift induced by four days of MD during the critical period was impaired by infusion of the antagonist SCH50911, but enhanced by infusion of the agonist baclofen. In contrast, seven days of MD in adult cats did not induce any significant OD shift, even when combined with the infusion of SCH50911 or baclofen. Together, these findings indicate that an endogenous GABAB receptor-mediated inhibition contributes to juvenile, but not adult, OD plasticity.
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Affiliation(s)
- Shanshan Cai
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Quentin S. Fischer
- Department of Ophthalmology and Visual Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Yu He
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Li Zhang
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Hanxiao Liu
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Nigel W. Daw
- Department of Ophthalmology and Visual Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Yupeng Yang
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, China
- Department of Ophthalmology and Visual Sciences, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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9
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Creanza TM, Liguori M, Liuni S, Nuzziello N, Ancona N. Meta-Analysis of Differential Connectivity in Gene Co-Expression Networks in Multiple Sclerosis. Int J Mol Sci 2016; 17:E936. [PMID: 27314336 PMCID: PMC4926469 DOI: 10.3390/ijms17060936] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 05/09/2016] [Accepted: 05/24/2016] [Indexed: 12/20/2022] Open
Abstract
Differential gene expression analyses to investigate multiple sclerosis (MS) molecular pathogenesis cannot detect genes harboring genetic and/or epigenetic modifications that change the gene functions without affecting their expression. Differential co-expression network approaches may capture changes in functional interactions resulting from these alterations. We re-analyzed 595 mRNA arrays from publicly available datasets by studying changes in gene co-expression networks in MS and in response to interferon (IFN)-β treatment. Interestingly, MS networks show a reduced connectivity relative to the healthy condition, and the treatment activates the transcription of genes and increases their connectivity in MS patients. Importantly, the analysis of changes in gene connectivity in MS patients provides new evidence of association for genes already implicated in MS by single-nucleotide polymorphism studies and that do not show differential expression. This is the case of amiloride-sensitive cation channel 1 neuronal (ACCN1) that shows a reduced number of interacting partners in MS networks, and it is known for its role in synaptic transmission and central nervous system (CNS) development. Furthermore, our study confirms a deregulation of the vitamin D system: among the transcription factors that potentially regulate the deregulated genes, we find TCF3 and SP1 that are both involved in vitamin D3-induced p27Kip1 expression. Unveiling differential network properties allows us to gain systems-level insights into disease mechanisms and may suggest putative targets for the treatment.
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Affiliation(s)
- Teresa Maria Creanza
- Institute of Intelligent Systems for Automation, National Research Council of Italy, 70126 Bari, Italy.
- Center for Complex Systems in Molecular Biology and Medicine, University of Turin, 10123 Turin, Italy.
| | - Maria Liguori
- Institute of Biomedical Technologies, National Research Council of Italy, 70126 Bari, Italy.
| | - Sabino Liuni
- Institute of Biomedical Technologies, National Research Council of Italy, 70126 Bari, Italy.
| | - Nicoletta Nuzziello
- Institute of Biomedical Technologies, National Research Council of Italy, 70126 Bari, Italy.
- Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari, 70126 Bari, Italy.
| | - Nicola Ancona
- Institute of Intelligent Systems for Automation, National Research Council of Italy, 70126 Bari, Italy.
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10
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Synaptic Plasticity, a Prominent Contributor to the Anxiety in Fragile X Syndrome. Neural Plast 2016; 2016:9353929. [PMID: 27239350 PMCID: PMC4864533 DOI: 10.1155/2016/9353929] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 04/04/2016] [Indexed: 01/03/2023] Open
Abstract
Fragile X syndrome (FXS) is an inheritable neuropsychological disease caused by expansion of the CGG trinucleotide repeat affecting the fmr1 gene on X chromosome, resulting in silence of the fmr1 gene and failed expression of FMRP. Patients with FXS suffer from cognitive impairment, sensory integration deficits, learning disability, anxiety, autistic traits, and so forth. Specifically, the morbidity of anxiety in FXS individuals remains high from childhood to adulthood. By and large, it is common that the change of brain plasticity plays a key role in the progression of disease. But for now, most studies excessively emphasized the one-sided factor on the change of synaptic plasticity participating in the generation of anxiety during the development of FXS. Here we proposed an integrated concept to acquire better recognition about the details of this process.
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11
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Rózsa M, Baka J, Bordé S, Rózsa B, Katona G, Tamás G. Unitary GABAergic volume transmission from individual interneurons to astrocytes in the cerebral cortex. Brain Struct Funct 2015; 222:651-659. [PMID: 26683686 DOI: 10.1007/s00429-015-1166-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 11/27/2015] [Indexed: 01/06/2023]
Abstract
Communication between individual GABAergic cells and their target neurons is mediated by synapses and, in the case of neurogliaform cells (NGFCs), by unitary volume transmission. Effects of non-synaptic volume transmission might involve non-neuronal targets, and astrocytes not receiving GABAergic synapses but expressing GABA receptors are suitable for evaluating this hypothesis. Testing several cortical interneuron types in slices of the rat cerebral cortex, we show selective unitary transmission from NGFCs to astrocytes with an early, GABAA receptor and GABA transporter-mediated component and a late component that results from the activation of GABA transporters and neuronal GABAB receptors. We could not detect Ca2+ influx in astrocytes associated with unitary GABAergic responses. Our experiments identify a presynaptic cell-type-specific, GABA-mediated communication pathway from individual neurons to astrocytes, assigning a role for unitary volume transmission in the control of ionic and neurotransmitter homeostasis.
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Affiliation(s)
- Márton Rózsa
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Anatomy, Physiology and Neuroscience, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary
| | - Judith Baka
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Anatomy, Physiology and Neuroscience, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary
| | - Sándor Bordé
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Anatomy, Physiology and Neuroscience, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary
| | - Balázs Rózsa
- Two-Photon Imaging Center, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary
| | - Gergely Katona
- Two-Photon Imaging Center, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, 1083, Hungary
| | - Gábor Tamás
- MTA-SZTE Research Group for Cortical Microcircuits, Department of Anatomy, Physiology and Neuroscience, University of Szeged, Közép fasor 52, Szeged, 6726, Hungary.
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Cifuentes-Diaz C, Marullo S, Doly S. Anatomical and ultrastructural study of PRAF2 expression in the mouse central nervous system. Brain Struct Funct 2015; 221:4169-4185. [PMID: 26645984 DOI: 10.1007/s00429-015-1159-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/24/2015] [Indexed: 02/01/2023]
Abstract
Prenylated Rab acceptor family, member 2 (PRAF2) is a four transmembrane domain protein of 19 kDa that is highly expressed in particular areas of mammalian brains. PRAF2 is mostly found in the endoplasmic reticulum (ER) of neurons where it plays the role of gatekeeper for the GB1 subunit of the GABAB receptor, preventing its progression in the biosynthetic pathway in the absence of hetero-dimerization with the GB2 subunit. However, PRAF2 can interact with several receptors and immunofluorescence studies indicate that PRAF2 distribution is larger than the ER, suggesting additional biological functions. Here, we conducted an immuno-cytochemical study of PRAF2 distribution in mouse central nervous system (CNS) at anatomical, cellular and ultra-structural levels. PRAF2 appears widely expressed in various regions of mature CNS, such as the olfactory bulbs, cerebral cortex, amygdala, hippocampus, ventral tegmental area and spinal cord. Consistent with its regulatory role of GABAB receptors, PRAF2 was particularly abundant in brain regions known to express GB1 subunits. However, other brain areas where GB1 is expressed, such as basal ganglia, thalamus and hypothalamus, contain little or no PRAF2. In these areas, GB1 subunits might reach the cell surface of neurons independently of GB2 to exert biological functions distinct from those of GABAB receptors, or be regulated by other gatekeepers. Electron microscopy studies confirmed the localization of PRAF2 in the ER, but identified previously unappreciated localizations, in mitochondria, primary cilia and sub-synaptic region. These data indicate additional modes of GABAB regulation in specific brain areas and new biological functions of PRAF2.
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Affiliation(s)
- Carmen Cifuentes-Diaz
- Institut du Fer à Moulin, INSERM UMR-S839, Université Pierre et Marie Curie, 75005, Paris, France
| | - Stefano Marullo
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Descartes, Sorbonne Paris Cité, 27 rue du Faubourg St-Jacques, 75014, Paris, France
| | - Stéphane Doly
- Institut Cochin, INSERM U1016, CNRS UMR8104, Université Paris Descartes, Sorbonne Paris Cité, 27 rue du Faubourg St-Jacques, 75014, Paris, France.
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Kim J, Son Y, Kim J, Lee S, Kang S, Park K, Kim SH, Kim JC, Kim J, Takayama C, Im HI, Yang M, Shin T, Moon C. Developmental and degenerative modulation of GABAergic transmission in the mouse hippocampus. Int J Dev Neurosci 2015; 47:320-32. [PMID: 26394279 DOI: 10.1016/j.ijdevneu.2015.08.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 08/05/2015] [Accepted: 08/21/2015] [Indexed: 11/30/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter involved in synaptic plasticity. GABAergic transmission is also implicated in developmental and degenerative processes in the brain. The goal of the present study was to understand the developmental and degenerative regulation of GABAergic transmission in the mouse hippocampus by examining changes in GABA receptor subunit mRNA levels and GABA-related protein expression during postnatal development of the hippocampus and trimethyltin (TMT)-induced neurodegeneration in the juvenile (postnatal day [PD] 24) and adult hippocampus (PD 56). During postnatal development, the mRNA levels of GABA A receptor (GABAAR) subunits, including α1, α4, β1, β2, and δ; GABA B receptor (GABABR) subunit 2; and the expression of GABA-related proteins, including glutamic acid decarboxylase, vesicular GABA transporter (VGAT), and potassium chloride cotransporter 2 increased gradually in the mouse hippocampus. The results of seizure scoring and histopathological findings in the hippocampus revealed a more pronounced response to the same administered TMT dose in juvenile mice, compared with that in adult mice. The mRNA levels of most GABA receptor subunits in the juvenile hippocampus, excluding GABAAR subunit β3, were dynamically altered after TMT treatment. The mRNA levels of GABAAR subunits γ2 and δ decreased significantly in the adult hippocampus following TMT treatment, whereas the level of GABABR subunit 1 mRNA increased significantly. Among the GABA-related proteins, only VGAT decreased significantly in the juvenile and adult mouse hippocampus after TMT treatment. In conclusion, regulation of GABAergic signaling in the mouse hippocampus may be related to maturation of the central nervous system and the degree of neurodegeneration during postnatal development and TMT-induced neurodegeneration in the experimental animals.
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Affiliation(s)
- Jinwook Kim
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Yeonghoon Son
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Juhwan Kim
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea; Center for Neuroscience, Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea
| | - Sueun Lee
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Sohi Kang
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Kyunghwan Park
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Sung-Ho Kim
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Jong-Choon Kim
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea
| | - Jeongtae Kim
- Department of Molecular Anatomy, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan
| | - Chitoshi Takayama
- Department of Molecular Anatomy, Faculty of Medicine, University of the Ryukyus, Okinawa 903-0215, Japan
| | - Heh-In Im
- Center for Neuroscience, Korea Institute of Science and Technology (KIST), Seoul 136-791, South Korea
| | - Miyoung Yang
- Department of Anatomy, School of Medicine, Wonkwang University, Iksan, Jeonbuk 570-749, South Korea
| | - Taekyun Shin
- Department of Veterinary Anatomy, College of Veterinary Medicine, Jeju National University, Jeju 690-756, South Korea.
| | - Changjong Moon
- Departments of Veterinary Anatomy and Veterinary Toxicology, College of Veterinary Medicine and Animal Medical Institute, Chonnam National University, Gwangju 500-757, South Korea.
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Benke D, Balakrishnan K, Zemoura K. Regulation of Cell Surface GABAB Receptors. DIVERSITY AND FUNCTIONS OF GABA RECEPTORS: A TRIBUTE TO HANNS MÖHLER, PART B 2015; 73:41-70. [DOI: 10.1016/bs.apha.2014.11.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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15
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Abstract
The defensive burying test is an experimental model that is used to explore anxiety-like behavior in adult rats. Because the expression of anxiety-like behavior may differ between infant and adult rats, we tested the impact of chambers with different sizes and shapes on defensive burying in 28-day-old Wistar rats. The first two chambers had base areas of 560 cm, but one was rectangular and the other round. The base areas of the other two chambers were 282 cm, also with one rectangular and one round. We examined the effects of vehicle and 1 mg/kg diazepam on defensive burying in the various chambers. Locomotor activity was also measured to identify or exclude any sedative effects. Independent of the treatments used, the infant rats showed a shorter burying latency in the three modified chambers and a longer cumulative burying time compared with the original apparatus. The effects of diazepam (i.e. increased latency and decreased burying time) were only significant in the small round chamber, without significant effects on general motor activity. These results suggest that a small round chamber that is used to test burying behavior is sensitive to the anxiolytic actions of diazepam when the experimental subjects are very young rats.
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Hawkes R. Purkinje cell stripes and long-term depression at the parallel fiber-Purkinje cell synapse. Front Syst Neurosci 2014; 8:41. [PMID: 24734006 PMCID: PMC3975104 DOI: 10.3389/fnsys.2014.00041] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 03/07/2014] [Indexed: 12/13/2022] Open
Abstract
The cerebellar cortex comprises a stereotyped array of transverse zones and parasagittal stripes, built around multiple Purkinje cell subtypes, which is highly conserved across birds and mammals. This architecture is revealed in the restricted expression patterns of numerous molecules, in the terminal fields of the afferent projections, in the distribution of interneurons, and in the functional organization. This review provides an overview of cerebellar architecture with an emphasis on attempts to relate molecular architecture to the expression of long-term depression (LTD) at the parallel fiber-Purkinje cell (pf-PC) synapse.
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Affiliation(s)
- Richard Hawkes
- Department of Cell Biology and Anatomy, University of Calgary Calgary, AB, Canada ; Hotchkiss Brain Institute, University of Calgary Calgary, AB, Canada ; Genes and Development Research Group, Faculty of Medicine, University of Calgary Calgary, AB, Canada
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Thibault K, Calvino B, Rivals I, Marchand F, Dubacq S, McMahon SB, Pezet S. Molecular mechanisms underlying the enhanced analgesic effect of oxycodone compared to morphine in chemotherapy-induced neuropathic pain. PLoS One 2014; 9:e91297. [PMID: 24618941 PMCID: PMC3949760 DOI: 10.1371/journal.pone.0091297] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 02/07/2014] [Indexed: 11/30/2022] Open
Abstract
Oxycodone is a μ-opioid receptor agonist, used for the treatment of a large variety of painful disorders. Several studies have reported that oxycodone is a more potent pain reliever than morphine, and that it improves the quality of life of patients. However, the neurobiological mechanisms underlying the therapeutic action of these two opioids are only partially understood. The aim of this study was to define the molecular changes underlying the long-lasting analgesic effects of oxycodone and morphine in an animal model of peripheral neuropathy induced by a chemotherapic agent, vincristine. Using a behavioural approach, we show that oxycodone maintains an optimal analgesic effect after chronic treatment, whereas the effect of morphine dies down. In addition, using DNA microarray technology on dorsal root ganglia, we provide evidence that the long-term analgesic effect of oxycodone is due to an up-regulation in GABAB receptor expression in sensory neurons. These receptors are transported to their central terminals within the dorsal horn, and subsequently reinforce a presynaptic inhibition, since only the long-lasting (and not acute) anti-hyperalgesic effect of oxycodone was abolished by intrathecal administration of a GABAB receptor antagonist; in contrast, the morphine effect was unaffected. Our study demonstrates that the GABAB receptor is functionally required for the alleviating effect of oxycodone in neuropathic pain condition, thus providing new insight into the molecular mechanisms underlying the sustained analgesic action of oxycodone.
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Affiliation(s)
- Karine Thibault
- Brain Plasticity Unit, ESPCI-ParisTech, Paris, France
- Centre National de la Recherche Scientifique, UMR 8249, Paris, France
- Neurorestoration Group, The Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
- * E-mail:
| | - Bernard Calvino
- Brain Plasticity Unit, ESPCI-ParisTech, Paris, France
- Centre National de la Recherche Scientifique, UMR 8249, Paris, France
| | - Isabelle Rivals
- Equipe de Statistique Appliquée, ESPCI-ParisTech, Paris, France
| | - Fabien Marchand
- Institut National de la Santé et de la Recherche Médicale, Unité 1107, NEURO-DOL, Clermont-Ferrand, France
- Clermont Université, Université d'Auvergne, Pharmacologie Fondamentale et Clinique de la Douleur, Clermont-Ferrand, France
| | - Sophie Dubacq
- Brain Plasticity Unit, ESPCI-ParisTech, Paris, France
- Centre National de la Recherche Scientifique, UMR 8249, Paris, France
| | - Stephen B. McMahon
- Neurorestoration Group, The Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Sophie Pezet
- Brain Plasticity Unit, ESPCI-ParisTech, Paris, France
- Centre National de la Recherche Scientifique, UMR 8249, Paris, France
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Gaiarsa JL, Porcher C. Emerging neurotrophic role of GABAB receptors in neuronal circuit development. Front Cell Neurosci 2013; 7:206. [PMID: 24282395 PMCID: PMC3824957 DOI: 10.3389/fncel.2013.00206] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 10/18/2013] [Indexed: 12/22/2022] Open
Abstract
The proper development of highly organized structures in the central nervous system is a complex process during which key events – neurogenesis, migration, growth, differentiation, and synaptogenesis – have to take place in an appropriate manner to create functional neuronal networks. It is now well established that GABA, the main inhibitory neurotransmitter in the adult mammalian brain, plays more than a classical inhibitory role and can function as an important developmental signal early in life. GABA binds to chloride-permeable ionotropic GABAA receptors and to G-protein-coupled GABAB receptors (GABAB-Rs). Although most of the trophic actions of GABA have been attributed to the activation of GABAA receptors, recent advances show that GABAB-Rs also regulate fundamental steps of network development. This review summarizes some of the recent progress about the neurotrophic role of GABAB-Rs to neuronal development.
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Affiliation(s)
- Jean-Luc Gaiarsa
- Institut National de la Santé et de la Recherche Médicale U-901 Marseille, France ; Aix-Marseille Université, UMR S901 Marseille, France ; Institut de Neurobiologie de la Méditerranée Marseille, France
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Engle MP, Merrill MA, Marquez De Prado B, Hammond DL. Spinal nerve ligation decreases γ-aminobutyric acidB receptors on specific populations of immunohistochemically identified neurons in L5 dorsal root ganglion of the rat. J Comp Neurol 2012; 520:1663-77. [PMID: 22120979 DOI: 10.1002/cne.23005] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This study examined the distribution of γ-aminobutyric acid (GABA)(B) receptors on immunohistochemically identified neurons, and levels of GABA(B(1)) and GABA(B(2)) mRNA, in the L4 and L5 dorsal root ganglia (DRG) of the rat in the absence of injury and 2 weeks after L5 spinal nerve ligation. In uninjured DRG, GABA(B(1)) immunoreactivity colocalized exclusively with the neuronal marker (NeuN) and did not colocalize with the satellite cell marker S-100. The GABA(B(1)) subunit colocalized to >97% of DRG neurons immunoreactive (IR) for neurofilament 200 (N52) or calcitonin gene-related peptide (CGRP), or labeled by isolectin B4 (IB4). Immunoreactivity for GABA(B(2)) was not detectable. L5 spinal nerve ligation did not alter the number of GABA(B(1)) -IR neurons or its colocalization pattern in the L4 DRG. However, ligation reduced the number of GABA(B(1)) -IR neurons in the L5 DRG by ≈38% compared with sham-operated and naïve rats. Specifically, ligation decreased the number of CGRP-IR neurons in the L5 DRG by 75%, but did not decrease the percent colocalization of GABA(B(1)) in those that remained. In the few IB4-positive neurons that remained in the L5 DRG, colocalization of GABA(B(1)) -IR decreased to 75%. Ligation also decreased levels of GABA(B(1)) and GABA(B(2)) mRNA in the L5, but not the L4 DRG compared with sham-operated or naïve rats. These findings indicate that the GABA(B) receptor is positioned to presynaptically modulate afferent transmission by myelinated, unmyelinated, and peptidergic afferents in the dorsal horn. Loss of GABA(B) receptors on primary afferent neurons may contribute to the development of mechanical allodynia after L5 spinal nerve ligation.
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Affiliation(s)
- Mitchell P Engle
- Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, USA
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20
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Presynaptic GABA(B) receptors decrease neurotransmitter release in vestibular nuclei neurons during vestibular compensation. Neuroscience 2012; 223:333-54. [PMID: 22871524 DOI: 10.1016/j.neuroscience.2012.07.061] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Revised: 07/18/2012] [Accepted: 07/30/2012] [Indexed: 01/25/2023]
Abstract
Unilateral damage to the peripheral vestibular receptors precipitates a debilitating syndrome of oculomotor and balance deficits at rest, which extensively normalize during the first week after the lesion due to vestibular compensation. In vivo studies suggest that GABA(B) receptor activation facilitates recovery. However, the presynaptic or postsynaptic sites of action of GABA(B) receptors in vestibular nuclei neurons after lesions have not been determined. Accordingly, here presynaptic and postsynaptic GABA(B) receptor activity in principal cells of the tangential nucleus, a major avian vestibular nucleus, was investigated using patch-clamp recordings correlated with immunolabeling and confocal imaging of the GABA(B) receptor subunit-2 (GABA(B)R2) in controls and operated chickens shortly after unilateral vestibular ganglionectomy (UVG). Baclofen, a GABA(B) agonist, generated no postsynaptic currents in principal cells in controls, which correlated with weak GABA(B)R2 immunolabeling on principal cell surfaces. However, baclofen decreased miniature excitatory postsynaptic current (mEPSC) and GABAergic miniature inhibitory postsynaptic current (mIPSC) events in principal cells in controls, compensating and uncompensated chickens three days after UVG, indicating the presence of functional GABA(B) receptors on presynaptic terminals. Baclofen decreased GABAergic mIPSC frequency to the greatest extent in principal cells on the intact side of compensating chickens, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 2-labeled terminals. In uncompensated chickens, baclofen decreased mEPSC frequency to the greatest extent in principal cells on the intact side, with concurrent increases in GABA(B)R2 pixel brightness and percentage overlap in synaptotagmin 1-labeled terminals. Altogether, these results revealed changes in presynaptic GABA(B) receptor function and expression which differed in compensating and uncompensated chickens shortly after UVG. This work supports an important role for GABA(B) autoreceptor-mediated inhibition in vestibular nuclei neurons on the intact side during early stages of vestibular compensation, and a role for GABA(B) heteroreceptor-mediated inhibition of glutamatergic terminals on the intact side in the failure to recover function.
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Abstract
The neurotransmitter GABA (γ-aminobutyric acid), acting via inotropic GABA(A) and metabotropic GABA(B) receptors, plays an essential role in a variety of distinct neuronal processes, including regulation of neuronal excitability, determination of temporal aspects of spike trains, control of the size and propagation of neuronal assemblies, generation of oscillatory activity, and neuronal plasticity. Although the developmental switch between excitatory and inhibitory GABA(A) receptor-mediated responses is widely appreciated, the fact that the postnatal maturation of the GABAergic system lasts until late adolescence is not so persuasively promoted. This review summarizes recent knowledge of the maturation of various aspects of the GABAergic systems, like functional expression of GABA synthesizing/degrading enzymes and transporters, density of GABAergic synapses, GABAergic projection patterns, GABA receptor subunit composition, and properties of GABAergic interneurons, with an emphasis on the late developmental alterations. In addition, some aspects of the development of mental capabilities during adolescence and their relation the delayed maturation of the GABAergic system are presented.
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Affiliation(s)
- Werner Kilb
- Institute of Physiology and Pathophysiology, University Medical Center of the Johannes Gutenberg University, Mainz, Germany.
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22
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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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24
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Tian Y, Gunther JR, Liao IH, Liu D, Ander BP, Stamova BS, Lit L, Jickling GC, Xu H, Zhan X, Sharp FR. GABA- and acetylcholine-related gene expression in blood correlate with tic severity and microarray evidence for alternative splicing in Tourette syndrome: a pilot study. Brain Res 2011; 1381:228-36. [PMID: 21241679 DOI: 10.1016/j.brainres.2011.01.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 12/08/2010] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
Abstract
Tourette syndrome (TS) is a complex childhood neurodevelopmental disorder characterized by motor and vocal tics. Recently, altered numbers of GABAergic-parvalbumin (PV) and cholinergic interneurons were observed in the basal ganglia of individuals with TS. Thus, we postulated that gamma-amino butyric acid (GABA)- and acetylcholine (ACh)-related genes might be associated with the pathophysiology of TS. Total RNA isolated from whole blood of 26 un-medicated TS subjects and 23 healthy controls (HC) was processed on Affymetrix Human Exon 1.0 ST arrays. Data were analyzed to identify genes whose expression correlated with tic severity in TS, and to identify genes differentially spliced in TS compared to HC subjects. Many genes (3627) correlated with tic severity in TS (p < 0.05) among which GABA- (p = 2.1 × 10⁻³) and ACh- (p = 4.25 × 10⁻⁸) related genes were significantly over-represented. Moreover, several GABA and ACh-related genes were predicted to be alternatively spliced in TS compared to HC including GABA receptors GABRA4 and GABRG1, the nicotinic ACh receptor CHRNA4 and cholinergic differentiation factor (CDF). This pilot study suggests that at least some of these GABA- and ACh-related genes observed in blood that correlate with tics or are alternatively spliced are involved in the pathophysiology of TS and tics.
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Affiliation(s)
- Yingfang Tian
- University of California at Davis, M.I.N.D., Institute and Department of Neurology, USA
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25
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The mammalian interaural time difference detection circuit is differentially controlled by GABAB receptors during development. J Neurosci 2010; 30:9715-27. [PMID: 20660254 DOI: 10.1523/jneurosci.1552-10.2010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Throughout development GABA(B) receptors (GABA(B)Rs) are widely expressed in the mammalian brain. In mature auditory brainstem neurons, GABA(B)Rs are involved in the short-term regulation of the strength and dynamics of excitatory and inhibitory inputs, thus modulating sound analysis. During development, GABA(B)Rs also contribute to long-term changes in input strength. Using a combination of whole-cell patch-clamp recordings in acute brain slices and immunostainings in gerbils, we characterized developmental changes in GABA(B)R-mediated regulation of synaptic inputs to neurons in the medial superior olive (MSO), an auditory brainstem nucleus that analyzes interaural time differences (ITDs). Here, we show that, before hearing onset, GABA(B)R-mediated depression of transmitter release is much stronger for excitation than inhibition, whereas in mature animals GABA(B)Rs mainly control the inhibition. During the same developmental period, GABA(B)R immunoreactivity shifts from the dendritic to the somatic region of the MSO. Furthermore, only before hearing onset (postnatal day 12), stimulation of the fibers originating in the medial and the lateral nucleus of the trapezoid body (MNTB and LNTB) activates GABA(B)Rs on both the inhibitory and the excitatory inputs. After hearing onset, GAD65-positive endings devoid of glycine transporter reactivity suggest GABA release from sources other than the MNTB and LNTB. At this age, pharmacological increase of spontaneous synaptic release activates GABA(B)Rs only on the inhibitory inputs. This indicates not only a profound inhibitory effect of GABA(B)Rs on the major inputs to MSO neurons in neonatal animals but also a direct modulatory role of GABA(B)Rs for ITD analysis in the MSO of adult animals.
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Zunner D, Deschermeier C, Kornau HC. GABA(B) receptor subunit 1 binds to proteins affected in 22q11 deletion syndrome. Biochem Biophys Res Commun 2010; 393:185-9. [PMID: 20036641 DOI: 10.1016/j.bbrc.2009.12.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 12/20/2009] [Indexed: 01/08/2023]
Abstract
GABA(B) receptors mediate slow inhibitory effects of the neurotransmitter gamma-aminobutyric acid (GABA) on synaptic transmission in the central nervous system. They function as heterodimeric G-protein-coupled receptors composed of the seven-transmembrane domain proteins GABA(B1) and GABA(B2), which are linked through a coiled-coil interaction. The ligand-binding subunit GABA(B1) is at first retained in the endoplasmic reticulum and is transported to the cell surface only upon assembly with GABA(B2). Here, we report that GABA(B1), via the coiled-coil domain, can also bind to soluble proteins of unknown function, that are affected in 22q11 deletion/DiGeorge syndrome and are therefore referred to as DiGeorge critical region 6 (DGCR6). In transfected neurons the GABA(B1)-DGCR6 association resulted in a redistribution of both proteins into intracellular clusters. Furthermore, the C-terminus of GABA(B2) interfered with the novel interaction, consistent with heterodimer formation overriding transient DGCR6-binding to GABA(B1). Thus, sequential coiled-coil interactions may direct GABA(B1) into functional receptors.
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Affiliation(s)
- Dagmar Zunner
- Center for Molecular Neurobiology, University of Hamburg, Germany
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27
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Casanova E, Guetg N, Vigot R, Seddik R, Julio-Pieper M, Hyland NP, Cryan JF, Gassmann M, Bettler B. A mouse model for visualization of GABA(B) receptors. Genesis 2010; 47:595-602. [PMID: 19603512 DOI: 10.1002/dvg.20535] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
GABA(B) receptors are the G-protein-coupled receptors for the neurotransmitter gamma-aminobutyric acid (GABA). Receptor subtypes are based on the subunit isoforms GABA(B1a) and GABA(B1b), which combine with GABA(B2) subunits to form heteromeric receptors. Here, we used a modified bacterial artificial chromosome (BAC) containing the GABA(B1) gene to generate transgenic mice expressing GABA(B1a) and GABA(B1b) subunits fused to the enhanced green fluorescence protein (eGFP). We demonstrate that the GABA(B1)-eGFP fusion proteins reproduce the cellular expression patterns of endogenous GABA(B1) proteins in the brain and in peripheral tissue. Crossing the GABA(B1)-eGFP BAC transgene into the GABA(B1) (-/-) background restores pre and postsynaptic GABA(B) functions, showing that the GABA(B1)-eGFP fusion proteins substitute for the lack of endogenous GABA(B1) proteins. Finally, we demonstrate that the GABA(B1)-eGFP fusion proteins replicate the temporal expression patterns of native GABA(B) receptors in cultured neurons. These transgenic mice therefore provide a validated tool for direct visualization of native GABA(B) receptors.
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Affiliation(s)
- Emilio Casanova
- Department of Biomedicine, Institute of Physiology, University of Basel, Basel, Switzerland
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28
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Villemure JF, Adam L, Bevan N, Gearing K, Chénier S, Bouvier M. Subcellular distribution of GABA(B) receptor homo- and hetero-dimers. Biochem J 2009; 388:47-55. [PMID: 15617512 PMCID: PMC1186692 DOI: 10.1042/bj20041435] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GBRs (GABA(B) receptors; where GABA stands for gamma-aminobutyric acid) are G-protein-coupled receptors that mediate slow synaptic inhibition in the brain and spinal cord. In vitro assays have previously demonstrated that these receptors are heterodimers assembled from two homologous subunits, GBR1 and GBR2, neither of which is capable of producing functional GBR on their own. We have used co-immunoprecipitation in combination with bioluminescence and fluorescence resonance energy transfer approaches in living cells to assess directly the interaction between GBR subunits and determine their subcellular localization. The results show that, in addition to forming heterodimers, GBR1 and GBR2 can associate as stable homodimers. Confocal microscopy indicates that, while GBR1/GBR1 homodimers are retained in the endoplasmic reticulum and endoplasmic reticulum-Golgi intermediate compartment, both GBR2/GBR2 homodimers and GBR1/GBR2 heterodimers are present at the plasma membrane. Although these observations shed new light on the assembly of GBR complexes, they raise questions about the potential functional roles of GBR1 and GBR2 homodimers.
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Affiliation(s)
- Josée-France Villemure
- *Department of Biochemistry, Université de Montréal, C. P. 6128, succursale Centre-Ville, Montreal, QC, Canada H3C 3J7
| | - Lynda Adam
- *Department of Biochemistry, Université de Montréal, C. P. 6128, succursale Centre-Ville, Montreal, QC, Canada H3C 3J7
| | - Nicola J. Bevan
- †GlaxoSmithKline Research and Development, Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, U.K
| | - Katy Gearing
- †GlaxoSmithKline Research and Development, Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire SG1 2NY, U.K
| | - Sébastien Chénier
- *Department of Biochemistry, Université de Montréal, C. P. 6128, succursale Centre-Ville, Montreal, QC, Canada H3C 3J7
| | - Michel Bouvier
- *Department of Biochemistry, Université de Montréal, C. P. 6128, succursale Centre-Ville, Montreal, QC, Canada H3C 3J7
- To whom correspondence should be addressed (email )
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Sun H, Wu SH. The physiological role of pre- and postsynaptic GABA(B) receptors in membrane excitability and synaptic transmission of neurons in the rat's dorsal cortex of the inferior colliculus. Neuroscience 2009; 160:198-211. [PMID: 19409201 DOI: 10.1016/j.neuroscience.2009.02.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2008] [Revised: 02/02/2009] [Accepted: 02/04/2009] [Indexed: 10/21/2022]
Abstract
In the inferior colliculus (IC), GABAergic inhibition mediated by GABA(A) receptors has been shown to play a significant role in regulating physiological responses, but little is known about the physiological role of GABA(B) receptors in IC neurons. In the present study, we used whole-cell patch clamp recording in vitro to investigate the effects of activation of GABA(B) receptors on membrane excitability and synaptic transmission of neurons in the rat's dorsal cortex of the inferior colliculus (ICD). Repetitive stimulation of GABAergic inputs to ICD neurons at high frequencies could elicit a slow and long-lasting postsynaptic response, which was reversibly abolished by the GABA(B) receptor antagonist, CGP 35348. The results suggest that postsynaptic GABA(B) receptors can directly mediate inhibitory synaptic transmission in ICD. The role of postsynaptic GABA(B) receptors in regulation of membrane excitability was further investigated by application of the GABA(B) receptor agonist, baclofen. Baclofen hyperpolarized the cell, reduced the membrane input resistance and firing rate, increased the threshold for generating action potentials (APs), and decreased the amplitude of the AP and its associated after-hyperpolarization. The Ca2+-mediated rebound depolarization following hyperpolarization and the depolarization hump at the beginning of membrane depolarization were also suppressed by baclofen. In voltage clamp experiments, baclofen induced inward rectifying K+ current and reduced low- and high-threshold Ca2+ currents, which may account for the suppression of membrane excitability by postsynaptic GABA(B) receptors. Application of baclofen also reduced excitatory synaptic responses mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and inhibitory synaptic responses mediated by GABA(A) receptors. Baclofen increased the ratios of 2nd/1st excitatory and inhibitory postsynaptic currents to paired-pulse stimulation of the synaptic inputs. These results suggest that fast glutamatergic and GABAergic synaptic transmission in ICD can be modulated by presynaptic GABA(B) receptors.
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Affiliation(s)
- H Sun
- Institute of Neuroscience, 335 Life Sciences Research Building, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S5B6, Canada
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30
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Liu Y, Huang R, Han L, Ke W, Shao K, Ye L, Lou J, Jiang C. Brain-targeting gene delivery and cellular internalization mechanisms for modified rabies virus glycoprotein RVG29 nanoparticles. Biomaterials 2009; 30:4195-202. [PMID: 19467700 DOI: 10.1016/j.biomaterials.2009.02.051] [Citation(s) in RCA: 182] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 04/22/2009] [Indexed: 01/06/2023]
Abstract
A 29 amino-acid peptide derived from the rabies virus glycoprotein (RVG29) was exploited as a ligand for efficient brain-targeting gene delivery. RVG29 was modified on polyamidoamine dendrimers (PAMAM) through bifunctional PEG, then complexed with DNA, yielding PAMAM-PEG-RVG29/DNA nanoparticles (NPs). The NPs were observed to be uptaken by brain capillary endothelial cells (BCECs) through a clathrin and caveolae mediated energy-depending endocytosis. The specific cellular uptake can be inhibited by free RVG29 and GABA but not by nicotinic acetylcholine receptor (nAchR) agonists/antagonists, indicating RVG29 probably relates to the GABA(B) receptor besides nAchR reported previously. PAMAM-PEG-RVG29/DNA NPs showed higher blood-brain barrier (BBB)-crossing efficiency than PAMAM/DNA NPs in an in vitro BBB model. In vivo imaging showed that the NPs were preferably accumulated in brain. The report gene expression of the PAMAM-PEG-RVG29/DNA NPs was observed in brain, and significantly higher than unmodified NPs. Thus, PAMAM-PEG-RVG29 provides a safe and noninvasive approach for the gene delivery across the BBB.
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Affiliation(s)
- Yang Liu
- Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, PR China
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31
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Chung SH, Kim CT, Hawkes R. Compartmentation of GABA B receptor2 expression in the mouse cerebellar cortex. THE CEREBELLUM 2009; 7:295-303. [PMID: 18418671 DOI: 10.1007/s12311-008-0030-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite the apparent uniformity in cellular composition of the adult mammalian cerebellar cortex, it is actually highly compartmentalized into transverse zones, and within each zone the cortex is further subdivided into a reproducible array of parasagittal stripes. The most extensively studied compartmentation antigen is zebrin II/aldolase c, which is expressed by a subset of Purkinje cells forming parasagittal stripes. Gamma-aminobutyric acid B receptors (GABABRs) are G-protein-coupled receptors that mediate a slow, prolonged form of inhibition in many brain areas. This study examines the localization of GABABR2 in the mouse cerebellum by using whole mount and section immunohistochemistry. The data reveal that GABABR2 immunoreactivity is expressed strongly in the dendrites of a subset of Purkinje cells that form a reproducible array of transverse zones and parasagittal stripes. By using double immunostaining, the striped pattern of GABABR2 expression was shown to be identical to that revealed by anti-zebrin II and complementary to that of phospholipase Cbeta4. This finding supports previous functional studies showing that inhibitory neurotransmission is highly patterned in the cerebellar cortex.
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Affiliation(s)
- Seung-Hyuk Chung
- Department of Cell Biology & Anatomy, Hotchkiss Brain Institute, and Genes and Development Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada
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32
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Dupré DJ, Robitaille M, Rebois RV, Hébert TE. The role of Gbetagamma subunits in the organization, assembly, and function of GPCR signaling complexes. Annu Rev Pharmacol Toxicol 2009; 49:31-56. [PMID: 18834311 DOI: 10.1146/annurev-pharmtox-061008-103038] [Citation(s) in RCA: 212] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The role of Gbetagamma subunits in cellular signaling has become well established in the past 20 years. Not only do they regulate effectors once thought to be the sole targets of Galpha subunits, but it has become clear that they also have a unique set of binding partners and regulate signaling pathways that are not always localized to the plasma membrane. However, this may be only the beginning of the story. Gbetagamma subunits interact with G protein-coupled receptors, Galpha subunits, and several different effector molecules during assembly and trafficking of receptor-based signaling complexes and not simply in response to ligand stimulation at sites of receptor cellular activity. Gbetagamma assembly itself seems to be tightly regulated via the action of molecular chaperones and in turn may serve a similar role in the assembly of specific signaling complexes. We propose that specific Gbetagamma subunits have a broader role in controlling the architecture, assembly, and activity of cellular signaling pathways.
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Affiliation(s)
- Denis J Dupré
- Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.
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33
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Zheng F, Adelsberger H, Müller MR, Fritschy JM, Werner S, Alzheimer C. Activin tunes GABAergic neurotransmission and modulates anxiety-like behavior. Mol Psychiatry 2009; 14:332-46. [PMID: 18180762 DOI: 10.1038/sj.mp.4002131] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Activin, a member of the transforming growth factor-beta superfamily, affords neuroprotection in acute brain injury, but its physiological functions in normal adult brain are largely unknown. Using transgenic (tg) mice expressing a dominant-negative activin receptor mutant under the control of the CaMKIIalpha promoter in forebrain neurons, we identified activin as a key regulator of gamma-aminobutyric acid (GABA)ergic synapses and anxiety-like behavior. In the open field, wild-type (wt) and tg mice did not differ in spontaneous locomotion and exploration behavior. However, tg mice visited inner fields significantly more often than wt mice. In the light-dark exploration test, tg mice made more exits, spent significantly more time on a well-lit elevated bar and went farther away from the dark box as compared to wt mice. In addition, the anxiolytic effect of diazepam was abrogated in tg mice. Thus the disruption of activin receptor signaling produced a low-anxiety phenotype that failed to respond to benzodiazepines. In whole-cell recordings from hippocampal pyramidal cells, enhanced spontaneous GABA release, increased GABA tonus, reduced benzodiazepine sensitivity and augmented GABA(B) receptor function emerged as likely substrates of the low-anxiety phenotype. These data provide strong evidence that activin influences pre- and postsynaptic components of GABAergic synapses in a highly synergistic fashion. Given the crucial role of GABAergic neurotransmission in emotional states, anxiety and depression, dysfunctions of activin receptor signaling could be involved in affective disorders: and drugs affecting this pathway might show promise for psychopharmacological treatment.
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Affiliation(s)
- F Zheng
- Institute of Physiology, University of Kiel, Kiel, Germany
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34
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Meier SD, Kafitz KW, Rose CR. Developmental profile and mechanisms of GABA-induced calcium signaling in hippocampal astrocytes. Glia 2008; 56:1127-37. [PMID: 18442094 DOI: 10.1002/glia.20684] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
GABA (gamma-aminobutyric acid) is a transmitter with dual action. Whereas it excites neurons during the first week of postnatal development, it represents the major inhibitory transmitter in the mature brain. GABA also activates astrocytes by binding to ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. This results in glial calcium transients which can induce the release of gliotransmitters, rendering GABA an important mediator of neuron-glia interaction. Using whole-cell patch-clamp and ratiometric calcium imaging in hippocampal slices from rats at postnatal days 3-34, we have analyzed the developmental profile as well as the cellular mechanisms of calcium signals induced by GABA(A) and GABA(B) receptor activation in astrocytes. We found that GABA-evoked glial calcium transients are mediated by both GABA(A) and GABA(B) receptors. Throughout development, GABA(A)-receptor activation resulted in immediate calcium transients in the vast majority of astrocytes, most likely by influx of calcium through voltage-gated calcium channels. GABA(B) receptor activation, in contrast, resulted in delayed calcium transients, which were blocked following depletion of intracellular calcium stores and during persistent activation of heterotrimeric G-proteins. GABA(B) receptor-mediated calcium signals exhibited a clear developmental profile with less than 10% of astrocytes responding at P3 or P32-34, and about 60% of cells between P11 and P15. Our data thus indicate that GABA(B) receptor-mediated calcium transients are due to calcium release from intracellular stores following G-protein activation. Moreover, GABA(B) receptor-mediated calcium signaling in astrocytes preferentially occurs at a period during postnatal development when hippocampal networks are established.
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Affiliation(s)
- Silke D Meier
- Institute for Neurobiology, Heinrich-Heine-University of Duesseldorf, Universitaetsstrasse 1, Duesseldorf, Germany
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35
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Wilkins ME, Li X, Smart TG. Tracking cell surface GABAB receptors using an alpha-bungarotoxin tag. J Biol Chem 2008; 283:34745-52. [PMID: 18812318 DOI: 10.1074/jbc.m803197200] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
GABA(B) receptors mediate slow synaptic inhibition in the central nervous system and are important for synaptic plasticity as well as being implicated in disease. Located at pre- and postsynaptic sites, GABA(B) receptors will influence cell excitability, but their effectiveness in doing so will be dependent, in part, on their trafficking to, and stability on, the cell surface membrane. To examine the dynamic behavior of GABA(B) receptors in GIRK cells and neurons, we have devised a method that is based on tagging the receptor with the binding site components for the neurotoxin, alpha-bungarotoxin. By using the alpha-bungarotoxin binding site-tagged GABA(B) R1a subunit (R1a(BBS)), co-expressed with the R2 subunit, we can track receptor mobility using the small reporter, alpha-bungarotoxin-conjugated rhodamine. In this way, the rates of internalization and membrane insertion for these receptors could be measured with fixed and live cells. The results indicate that GABA(B) receptors rapidly turnover in the cell membrane, with the rate of internalization affected by the state of receptor activation. The bungarotoxin-based method of receptor-tagging seems ideally suited to follow the dynamic regulation of other G-protein-coupled receptors.
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Affiliation(s)
- Megan E Wilkins
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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36
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Boivin B, Vaniotis G, Allen BG, Hébert TE. G protein-coupled receptors in and on the cell nucleus: a new signaling paradigm? J Recept Signal Transduct Res 2008; 28:15-28. [PMID: 18437627 DOI: 10.1080/10799890801941889] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Signaling from internalizing and endosomal receptors has almost become a classic GPCR paradigm in the last several years. However, it has become clear in recent years that GPCRs also elicit signals when resident at other subcellular sites including the endoplasmic reticulum, Golgi apparatus, and the nucleus. In this review we discuss the nature, function, and trafficking of nuclear GPCR signaling complexes, as well as potential sources of endogenous and exogenous ligands. Finally, we pose a series of questions that will need to be answered in the coming years to confirm and extend this as a new paradigm for GPCR signaling.
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Affiliation(s)
- Benoit Boivin
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA
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37
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GABAB Receptors in Neuroendocrine Regulation. Cell Mol Neurobiol 2008; 28:803-17. [DOI: 10.1007/s10571-008-9263-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 01/18/2008] [Indexed: 12/14/2022]
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38
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Luján R. Subcellular regulation of metabotropic GABA receptors in the developing cerebellum. THE CEREBELLUM 2007; 6:123-9. [PMID: 17510912 DOI: 10.1080/14734220601039157] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Our understanding of GABAergic and glutamatergic neurotransmission in the CNS has been greatly influenced with the discovery and subsequent investigations of the metabotropic gamma-aminobutyric acid (B) (GABA(B)) receptors. These G-protein coupled receptors mediate slow inhibitory neurotransmission and are widely expressed and distributed in the cerebellum, where they play critical roles in neuronal excitability and modulation of synaptic neurotransmission. Their function is modulated by interaction with effector ion channels, notably inwardly rectifying K(+) channels and voltage-gated Ca(2+) channels. The receptors are encoded by two distinct subunits, GABA(B1) and GABA(B2), both of which are required in order to function normally in vivo, as shown in recombinant expression systems and in GABA(B1) -/- mice. The GABA(B1) and GABA(B2) subunits exhibit overlapping distributions in the cerebellar cortex, both at pre- and postsynaptic sites, during development and adulthood. They are in particular abundant in Purkinje cells prior to synaptogenesis and throughout postnatal development. Using high-resolution immunohistochemical techniques at the electron microscopic level in combination with quantitative analysis and three-dimensional reconstructions, it has recently been demonstrated that GABA(B) receptors undergo changes in localization on the surface of Purkinje cell dendrites and spines during postnatal development in association with the establishment and maturation of excitatory synapses. Due to this dynamic regulation, the highest densities of GABA(B1) and GABA(B2) subunits occur around the glutamatergic synapses between Purkinje cell spines and parallel fibre varicosities. This review highlights recent studies that have shed further light on the subcellular localization during postnatal development and the cell surface dynamics of GABA(B) receptors.
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Affiliation(s)
- Rafael Luján
- Departamento de Ciencias Médicas, Facultad de Medicina-CRIB, Universidad de Castilla-La Mancha, Campus Biosanitario, Albacete, Spain.
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39
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Grampp T, Sauter K, Markovic B, Benke D. Gamma-aminobutyric acid type B receptors are constitutively internalized via the clathrin-dependent pathway and targeted to lysosomes for degradation. J Biol Chem 2007; 282:24157-65. [PMID: 17581821 DOI: 10.1074/jbc.m702626200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Receptor internalization is recognized as an important mechanism for rapidly regulating cell surface numbers of receptors. However, there are conflicting results on the existence of rapid endocytosis of gamma-aminobutyric acid, type B (GABAB) receptors. Therefore, we analyzed internalization of GABAB receptors expressed in HEK 293 cells qualitatively and quantitatively using immunocytochemical, cell surface enzyme-linked immunosorbent assay, and biotinylation methods. The data indicate the existence of rapid constitutive receptor internalization, with the first endocytosed receptors being observed in proximity of the plasma membrane after 10 min. After 120 min, a loss of about 40-50% of cell surface receptors was detected. Stimulation of GABAB receptors with GABA or baclofen did not enhance endocytosis of receptors, indicating the lack of agonist-induced internalization. The data suggest that GABAB receptors were endocytosed via the classical dynamin- and clathrin-dependent pathway and accumulated in an endosomal sorting compartment before being targeted to lysosomes for degradation. No evidence for recycling of receptors back to the cell surface was found. In conclusion, the results indicate the presence of constitutive internalization of GABAB receptors via clathrin-coated pits, which resulted in lysosomal degradation of the receptors.
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Affiliation(s)
- Thomas Grampp
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich 8057, Switzerland
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40
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Marshall FH. The role of GABA(B) receptors in the regulation of excitatory neurotransmission. Results Probl Cell Differ 2007; 44:87-98. [PMID: 17549439 DOI: 10.1007/400_2007_038] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
GABA(B) receptors are the metabotrophic receptors for GABA. They are members of the G-protein coupled superfamily of receptors but are highly unusual as they are made up of a dimer of 7-transmembrane spanning subunits. The receptors are widely distributed throughout the central nervous system where they act post-synaptically to cause a long-lasting hyperpolarisation through the activation of a potassium conductance. They are also present pre-synaptically where they act as auto and heteroreceptors to inhibit neurotransmitter release. GABA(B) receptors play a complex role in the regulation of excitatory transmission and their activation can have both inhibitory and dis-inhibitory effects. This has profound physiological and behavioural consequences including modification of LTP and memory, regulation of seizure activity and nociception.
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Affiliation(s)
- Fiona H Marshall
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK.
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41
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Merlo D, Mollinari C, Inaba Y, Cardinale A, Rinaldi AM, D'Antuono M, D'Arcangelo G, Tancredi V, Ragsdale D, Avoli M. Reduced GABAB receptor subunit expression and paired-pulse depression in a genetic model of absence seizures. Neurobiol Dis 2007; 25:631-41. [PMID: 17207629 DOI: 10.1016/j.nbd.2006.11.005] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 10/17/2006] [Accepted: 11/05/2006] [Indexed: 10/23/2022] Open
Abstract
Neocortical networks play a major role in the genesis of generalized spike-and-wave (SW) discharges associated with absence seizures in humans and in animal models, including genetically predisposed WAG/Rij rats. Here, we tested the hypothesis that alterations in GABA(B) receptors contribute to neocortical hyperexcitability in these animals. By using Real-Time PCR we found that mRNA levels for most GABA(B(1)) subunits are diminished in epileptic WAG/Rij neocortex as compared with age-matched non-epileptic controls (NEC), whereas GABA(B(2)) mRNA is unchanged. Next, we investigated the cellular distribution of GABA(B(1)) and GABA(B(2)) subunits by confocal microscopy and discovered that GABA(B(1)) subunits fail to localize in the distal dendrites of WAG/Rij neocortical pyramidal cells. Intracellular recordings from neocortical cells in an in vitro slice preparation demonstrated reduced paired-pulse depression of pharmacologically isolated excitatory and inhibitory responses in epileptic WAG/Rij rats as compared with NECs; moreover, paired-pulse depression in NEC slices was diminished by a GABA(B) receptor antagonist to a greater extent than in WAG/Rij rats further suggesting GABA(B) receptor dysfunction. In conclusion, our data identify changes in GABA(B) receptor subunit expression and distribution along with decreased paired-pulse depression in epileptic WAG/Rij rat neocortex. We propose that these alterations may contribute to neocortical hyperexcitability and thus to SW generation in absence epilepsy.
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Affiliation(s)
- D Merlo
- Istituto Superiore di Sanità, Dipartimento di Biologia Cellulare e Neuroscienze, 00161 Rome, Italy
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42
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Jacobson LH, Bettler B, Kaupmann K, Cryan JF. GABAB1 receptor subunit isoforms exert a differential influence on baseline but not GABAB receptor agonist-induced changes in mice. J Pharmacol Exp Ther 2006; 319:1317-26. [PMID: 16990508 DOI: 10.1124/jpet.106.111971] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
GABA(B) receptor agonists produce hypothermia and motor incoordination. Two GABA(B(1)) receptor subunit isoforms exist, but because of lack of specific molecular or pharmacological tools, the relevance of these isoforms in controlling basal body temperature, locomotor activity, or in vivo responses to GABA(B) receptor agonists has been unknown. Here, we used mice deficient in the GABA(B(1a)) and GABA(B(1b)) subunit isoforms to examine the influence of these isoforms on both baseline motor behavior and body temperature and on the motor-incoordinating and hypothermic responses to the GABA(B) receptor agonists l-baclofen and gamma-hydroxybutyrate (GHB). GABA(B(1b))(-/-) mice were hyperactive in a novel environment and showed slower habituation than either GABA(B(1a))(-/-) or wild-type mice. GABA(B(1b))(-/-) mice were hyperactive throughout the circadian dark phase. Hypothermia in response to l-baclofen (6 and 12 mg/kg) or GHB (1 g/kg), baclofen-induced ataxia as determined on the fixed-speed Rotarod, and GHB-induced hypolocomotion were significantly, but for the most part similarly, attenuated in both GABA(B(1a))(-/-) and GABA(B(1b))(-/-) mice. We conclude that l-baclofen and GHB are nonselective for either GABA(B(1)) receptor isoform in terms of in vivo responses. However, GABA(B(1)) receptor isoforms have distinct and different roles in mediating locomotor behavioral responses to a novel environment. Therefore, GABA(B(1a)) and GABA(B(1b)) isoforms are functionally relevant molecular variants of the GABA(B(1)) receptor subunit, which are differentially involved in specific neurophysiological processes and behaviors.
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Affiliation(s)
- Laura H Jacobson
- Novartis Institutes for BioMedical Research, Novartis Pharma AG, Basel, Switzerland
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43
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Dupré DJ, Hébert TE. Biosynthesis and trafficking of seven transmembrane receptor signalling complexes. Cell Signal 2006; 18:1549-59. [PMID: 16677801 DOI: 10.1016/j.cellsig.2006.03.009] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2006] [Accepted: 03/21/2006] [Indexed: 12/16/2022]
Abstract
Recent studies have shown that 7-transmembrane receptors (7TM-Rs), their associated signalling molecules and scaffolding proteins are often constitutively associated under basal conditions. These studies highlight that receptor ontogeny and trafficking are likely to play key roles in the determination of both signalling specificity and efficacy. This review highlights information about how 7TM-Rs and their associated signalling molecules are trafficked to the cell surface as well as other intracellular destinations.
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Affiliation(s)
- Denis J Dupré
- Department of Pharmacology and Therapeutics, McIntyre Medical Sciences Building, 3655 Promenade Sir William Osler, Montréal, Québec, Canada H3G 1Y6
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44
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Kornau HC. GABAB receptors and synaptic modulation. Cell Tissue Res 2006; 326:517-33. [PMID: 16932937 DOI: 10.1007/s00441-006-0264-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2006] [Accepted: 05/31/2006] [Indexed: 12/18/2022]
Abstract
GABA(B) receptors modulate transmitter release and postsynaptic membrane potential at various types of central synapses. They function as heterodimers of two related seven-transmembrane domain receptor subunits. Trafficking, activation and signalling of GABA(B) receptors are regulated both by allosteric interactions between the subunits and by the binding of additional proteins. Recent studies have shed light on the roles of GABA(B) receptors in plasticity processes at excitatory synapses. This review summarizes our knowledge of the localization, structure and function of GABA(B) receptors in the central nervous system and their use as drug targets for neurological and psychiatric disorders.
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Affiliation(s)
- Hans-Christian Kornau
- Center for Molecular Neurobiology (ZMNH), University of Hamburg, Falkenried 94, 20251 Hamburg, Germany.
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Vigot R, Barbieri S, Bräuner-Osborne H, Turecek R, Shigemoto R, Zhang YP, Luján R, Jacobson LH, Biermann B, Fritschy JM, Vacher CM, Müller M, Sansig G, Guetg N, Cryan JF, Kaupmann K, Gassmann M, Oertner TG, Bettler B. Differential compartmentalization and distinct functions of GABAB receptor variants. Neuron 2006. [PMID: 16701209 DOI: 10.1016/j.neuron.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2022]
Abstract
GABAB receptors are the G protein-coupled receptors for the main inhibitory neurotransmitter in the brain, gamma-aminobutyric acid (GABA). Molecular diversity in the GABAB system arises from the GABAB1a and GABAB1b subunit isoforms that solely differ in their ectodomains by a pair of sushi repeats that is unique to GABAB1a. Using a combined genetic, physiological, and morphological approach, we now demonstrate that GABAB1 isoforms localize to distinct synaptic sites and convey separate functions in vivo. At hippocampal CA3-to-CA1 synapses, GABAB1a assembles heteroreceptors inhibiting glutamate release, while predominantly GABAB1b mediates postsynaptic inhibition. Electron microscopy reveals a synaptic distribution of GABAB1 isoforms that agrees with the observed functional differences. Transfected CA3 neurons selectively express GABAB1a in distal axons, suggesting that the sushi repeats, a conserved protein interaction motif, specify heteroreceptor localization. The constitutive absence of GABAB1a but not GABAB1b results in impaired synaptic plasticity and hippocampus-dependent memory, emphasizing molecular differences in synaptic GABAB functions.
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Affiliation(s)
- Réjan Vigot
- Department of Clinical-Biological Sciences, Institute of Physiology, Pharmazentrum, University of Basel, CH-4056 Basel, Switzerland
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46
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Vigot R, Barbieri S, Bräuner-Osborne H, Turecek R, Shigemoto R, Zhang YP, Luján R, Jacobson LH, Biermann B, Fritschy JM, Vacher CM, Müller M, Sansig G, Guetg N, Cryan JF, Kaupmann K, Gassmann M, Oertner TG, Bettler B. Differential compartmentalization and distinct functions of GABAB receptor variants. Neuron 2006; 50:589-601. [PMID: 16701209 PMCID: PMC3531664 DOI: 10.1016/j.neuron.2006.04.014] [Citation(s) in RCA: 243] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2006] [Revised: 03/24/2006] [Accepted: 04/03/2006] [Indexed: 12/12/2022]
Abstract
GABAB receptors are the G protein-coupled receptors for the main inhibitory neurotransmitter in the brain, gamma-aminobutyric acid (GABA). Molecular diversity in the GABAB system arises from the GABAB1a and GABAB1b subunit isoforms that solely differ in their ectodomains by a pair of sushi repeats that is unique to GABAB1a. Using a combined genetic, physiological, and morphological approach, we now demonstrate that GABAB1 isoforms localize to distinct synaptic sites and convey separate functions in vivo. At hippocampal CA3-to-CA1 synapses, GABAB1a assembles heteroreceptors inhibiting glutamate release, while predominantly GABAB1b mediates postsynaptic inhibition. Electron microscopy reveals a synaptic distribution of GABAB1 isoforms that agrees with the observed functional differences. Transfected CA3 neurons selectively express GABAB1a in distal axons, suggesting that the sushi repeats, a conserved protein interaction motif, specify heteroreceptor localization. The constitutive absence of GABAB1a but not GABAB1b results in impaired synaptic plasticity and hippocampus-dependent memory, emphasizing molecular differences in synaptic GABAB functions.
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Affiliation(s)
- Réjan Vigot
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | - Samuel Barbieri
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | - Hans Bräuner-Osborne
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
- Department of Medicinal Chemistry Danish University of Pharmaceutical Sciences DK-2100 Copenhagen Denmark
| | - Rostislav Turecek
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
- Institute of Experimental Medicine Academy of Sciences 142 20 Prague Czech Republic
| | - Ryuichi Shigemoto
- Division of Cerebral Structure National Institute for Physiological Sciences Myodaiji, Okazaki 444-8585 Japan
- CREST Japan Science and Technology Corporation Kawaguchi 332-0012 Japan
| | | | - Rafael Luján
- Division of Cerebral Structure National Institute for Physiological Sciences Myodaiji, Okazaki 444-8585 Japan
- CREST Japan Science and Technology Corporation Kawaguchi 332-0012 Japan
- Department Ciencias Médicas Facultad de Medicina-CRIB Universidad de Castilla-La Mancha 02006 Albacete Spain
| | - Laura H. Jacobson
- Novartis Institutes for BioMedical Research Novartis Pharma AG CH-4002 Basel Switzerland
| | - Barbara Biermann
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | - Jean-Marc Fritschy
- Institute of Pharmacology and Toxicology University of Zurich CH-8057 Zurich Switzerland
| | - Claire-Marie Vacher
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | - Matthias Müller
- Novartis Institutes for BioMedical Research Novartis Pharma AG CH-4002 Basel Switzerland
| | - Gilles Sansig
- Novartis Institutes for BioMedical Research Novartis Pharma AG CH-4002 Basel Switzerland
| | - Nicole Guetg
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | - John F. Cryan
- Novartis Institutes for BioMedical Research Novartis Pharma AG CH-4002 Basel Switzerland
| | - Klemens Kaupmann
- Novartis Institutes for BioMedical Research Novartis Pharma AG CH-4002 Basel Switzerland
| | - Martin Gassmann
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
| | | | - Bernhard Bettler
- Department of Clinical-Biological Sciences Institute of Physiology Pharmazentrum University of Basel CH-4056 Basel Switzerland
- Correspondence:
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47
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Rey-Roldán EB, Bianchi MS, Bettler B, Becu-Villalobos D, Lux-Lantos VA, Libertun C. Adenohypophyseal and hypothalamic GABA B receptor subunits are downregulated by estradiol in adult female rats. Life Sci 2006; 79:342-50. [PMID: 16516242 DOI: 10.1016/j.lfs.2006.01.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 12/15/2005] [Accepted: 01/09/2006] [Indexed: 11/22/2022]
Abstract
Gamma-aminobutyric acid (GABA) participates in neuroendocrine regulation. Since steroid hormones have been shown to modulate the GABAergic system, here we evaluated the effect of chronic in vivo estradiol administration on GABA B receptor (GABA(B)R) expression. GABA(B1) and GABA(B2) subunits were analyzed by Western Blot and RT-PCR, in hypothalami and anterior pituitaries of adult female rats: a) treated for 1 week with estradiol-valerate (a single dose of 100 mug /kg: E1), b) implanted with a 10 mg pellet of estradiol-benzoate for 5 weeks (E5) or c) on proestrous (P), d) ovariectomized (OVX). Pituitary GABA(B)R levels were correlated to a biological effect: baclofen, a GABA(B)R agonist, action on intracellular calcium titers ([Ca(2+)](i)) in pituitary cells. E5 pituitaries showed a significant decrease in the expression of GABA(B1) and GABA(B2) mRNAs compared to P. The GABA(B1a) splice variant of GABA(B1) was always more abundant than GABA(B1b) in this tissue. Similar to the pituitary, hypothalamic GABA(B1) and GABA(B2) mRNAs decreased in E5; this was confirmed at the protein level. In the hypothalamus GABA(B1b) was the main variant expressed in P rats, and was the one significantly sensitive to estradiol-induced decrease, as determined by Western Blots. Castration did not modify GABA(B)R expression with regards to P in either tissue. In P pituitary cells baclofen induced a decrease in [Ca(2+)](i), in contrast this effect was lost in E5 cells. We conclude that chronic estradiol treatment negatively regulates the expression of the GABA(B)R subunits in the pituitary and the hypothalamus. This effect is coupled to a loss of baclofen action on intracellular calcium in pituitary cells.
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Affiliation(s)
- Estela B Rey-Roldán
- Instituto de Biología y Medicina Experimental-CONICET, Buenos Aires, Argentina
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48
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Luján R, Shigemoto R. Localization of metabotropic GABA receptor subunits GABAB1 and GABAB2 relative to synaptic sites in the rat developing cerebellum. Eur J Neurosci 2006; 23:1479-90. [PMID: 16553611 DOI: 10.1111/j.1460-9568.2006.04669.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The highest densities of the two metabotropic GABA subunits, GABAB1 and GABAB2, have been reported as occurring around the glutamatergic synapses between Purkinje cell spines and parallel fibre varicosities. In order to determine how this distribution is achieved during development, we investigated the expression pattern and the cellular and subcellular localization of the GABAB1 and GABAB2 subunits in the rat cerebellum during postnatal development. At the light microscopic level, immunoreactivity for the GABAB1 and GABAB2 subunits was very prominent in the developing molecular layer, especially in Purkinje cells. Using double immunofluorescence, we demonstrated that GABAB1 was transiently expressed in glial cells. At the electron microscopic level, immunoreactivity for GABAB receptors was always detected both pre- and postsynaptically. Presynaptically, GABAB1 and GABAB2 were localized in the extrasynaptic membrane of parallel fibres at all ages, and only rarely in GABAergic axons. Postsynaptically, GABAB receptors were localized to the extrasynaptic and perisynaptic plasma membrane of Purkinje cell dendrites and spines throughout development. Quantitative analysis and three-dimensional reconstructions further revealed a progressive developmental movement of the GABAB1 subunit on the surface of Purkinje cells from dendritic shafts to its final destination, the dendritic spines. Together, these results indicate that GABAB receptors undergo dynamic regulation during cerebellar development in association with the establishment and maturation of glutamatergic synapses to Purkinje cells.
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Affiliation(s)
- R Luján
- Departamento de Ciencias Médicas, Facultad de Medicina, Centro Regional de Investigaciones Biomédicas, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006 Albacete, Spain.
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49
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McCarson KE, Duric V, Reisman SA, Winter M, Enna SJ. GABA(B) receptor function and subunit expression in the rat spinal cord as indicators of stress and the antinociceptive response to antidepressants. Brain Res 2005; 1068:109-17. [PMID: 16368079 DOI: 10.1016/j.brainres.2005.11.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Revised: 11/02/2005] [Accepted: 11/06/2005] [Indexed: 02/05/2023]
Abstract
Experiments were undertaken to examine whether once daily i.p. administration of either of two antidepressants used for the treatment of neuropathic pain, amitriptyline (10 mg/kg) and fluoxetine (5 mg/kg), to rats for 7 days modifies GABA(B) receptor function and subunit expression in the lumbar spinal cord. The results indicate that, as previously reported for desipramine, both amitriptyline and fluoxetine increase the pain threshold to a thermal stimulus, the expression of GABA(B(1)) subunits, and baclofen-stimulated [35S]GTPgammaS binding, a measure of GABA(B) receptor function. The effects of antidepressant administration on GABA(B(1b)) and GABA(B(2)) subunit expression in spinal cord are more variable than for GABA(B(1a)). It was also discovered that repeated daily exposure to a thermal stimulus or immobilization stress increases GABA(B(1a)) expression in the lumbar spinal cord, with no commensurate change in thermal pain threshold or GABA(B) receptor sensitivity. These results support a relationship between GABA(B) receptors and the action of antidepressants. The findings demonstrate that drug-induced increases in GABA(B) receptor function can occur independently of any change in GABA(B) receptor subunit expression and are consistent with the notion that GABA(B) receptor subunits have multiple functions, only one of which is dimerization to form GABA(B) receptors. The data also suggest that GABA(B) subunit gene expression may serve as a preclinical marker of antidepressant efficacy and of drug- or stress-induced modifications in central nervous system activity.
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Affiliation(s)
- Kenneth E McCarson
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
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50
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Bianchi MS, Lux-Lantos VA, Bettler B, Libertun C. Expression of gamma-aminobutyric acid B receptor subunits in hypothalamus of male and female developing rats. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 2005; 160:124-9. [PMID: 16297450 DOI: 10.1016/j.devbrainres.2005.06.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 06/28/2005] [Accepted: 06/30/2005] [Indexed: 11/26/2022]
Abstract
GABA and its receptors show particular ontogenic distributions in different rat brain areas. Recently, GABAB receptors (GBR) have been described to assemble as heterodimers formed by a GBR1a/b and a GBR2 subunit. Here, the ontogeny of rat GBRs and the pattern of subunit expression in both sexes were determined in the hypothalamus, a critical area for homeostatic regulation. Male and female rats were sacrificed at 1, 4, 12, 20, 28, 38 days of life and at adulthood and hypothalami were removed and frozen. Western blots analysis for GBR1 and GBR2 subunits showed that both were expressed in male and female hypothalamic membranes from day 1 to adulthood. In females, both GBR1a and GBR1b were maximally expressed in newborns and decreased towards adulthood. At birth, expression of GBR1a was significantly higher than GBR1b, while at 38 days, GBR1b was more abundant. In males, GBR1a and GBR1b expression was higher in young animals and decreased gradually showing adult levels between the second and third weeks of age without differences between isoforms. Comparing GBR1 variants levels in hypothalamus between sexes, GBR1a was significantly more abundant in females at birth while at 38 days its expression was higher in males; GBR1b showed no sex differences along development. GBR2 was detected in hypothalami of females and males at all ages; maximum levels were observed at 12 days and adult levels were attained at 38 days, without sex differences. This is the first report on the ontogeny of hypothalamic GABAB receptors in male and female rats, with a particular developmental pattern of subunit and isoform expression and presenting some sex differences.
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Affiliation(s)
- María S Bianchi
- Instituto de Biología y Medicina Experimental-CONICET, V. de Obligado 2490, (C1428ADN) Buenos Aires, Argentina
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