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Martín-Belmonte A, Aguado C, Alfaro-Ruiz R, Kulik A, de la Ossa L, Moreno-Martínez AE, Alberquilla S, García-Carracedo L, Fernández M, Fajardo-Serrano A, Aso E, Shigemoto R, Martín ED, Fukazawa Y, Ciruela F, Luján R. Nanoarchitecture of Ca V2.1 channels and GABA B receptors in the mouse hippocampus: Impact of APP/PS1 pathology. Brain Pathol 2024:e13279. [PMID: 38887180 DOI: 10.1111/bpa.13279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 05/27/2024] [Indexed: 06/20/2024] Open
Abstract
Voltage-gated CaV2.1 (P/Q-type) Ca2+ channels play a crucial role in regulating neurotransmitter release, thus contributing to synaptic plasticity and to processes such as learning and memory. Despite their recognized importance in neural function, there is limited information on their potential involvement in neurodegenerative conditions such as Alzheimer's disease (AD). Here, we aimed to explore the impact of AD pathology on the density and nanoscale compartmentalization of CaV2.1 channels in the hippocampus in association with GABAB receptors. Histoblotting experiments showed that the density of CaV2.1 channel was significantly reduced in the hippocampus of APP/PS1 mice in a laminar-dependent manner. CaV2.1 channel was enriched in the active zone of the axon terminals and was present at a very low density over the surface of dendritic tree of the CA1 pyramidal cells, as shown by quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL). In APP/PS1 mice, the density of CaV2.1 channel in the active zone was significantly reduced in the strata radiatum and lacunosum-moleculare, while it remained unaltered in the stratum oriens. The decline in Cav2.1 channel density was found to be associated with a corresponding impairment in the GABAergic synaptic function, as evidenced by electrophysiological experiments carried out in the hippocampus of APP/PS1 mice. Remarkably, double SDS-FRL showed a co-clustering of CaV2.1 channel and GABAB1 receptor in nanodomains (~40-50 nm) in wild type mice, while in APP/PS1 mice this nanoarchitecture was absent. Together, these findings suggest that the AD pathology-induced reduction in CaV2.1 channel density and CaV2.1-GABAB1 de-clustering may play a role in the synaptic transmission alterations shown in the AD hippocampus. Therefore, uncovering these layer-dependent changes in P/Q calcium currents associated with AD pathology can benefit the development of future strategies for AD management.
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Affiliation(s)
- Alejandro Martín-Belmonte
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Carolina Aguado
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Rocío Alfaro-Ruiz
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Akos Kulik
- Institute for Physiology II, Medical Faculty, University of Freiburg, Freiburg, Germany
| | - Luis de la Ossa
- Departamento de Sistemas Informáticos, Escuela Superior de Ingeniería Informática, Universidad de Castilla-La Mancha, Albacete, Spain
| | - Ana Esther Moreno-Martínez
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Samuel Alberquilla
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Lucía García-Carracedo
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Miriam Fernández
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
| | - Ana Fajardo-Serrano
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
| | - Ester Aso
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Eduardo D Martín
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Faculty of Medical Science, University of Fukui, Fukui, Japan
- Life Science Innovation Center, University of Fukui, Fukui, Japan
| | - Francisco Ciruela
- Pharmacology Unit, Department of Pathology and Experimental Therapeutics, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, Barcelona, Spain
- Neuropharmacology and Pain Group, Neuroscience Program, Institut d'Investigació Biomèdica de Bellvitge, Barcelona, Spain
| | - Rafael Luján
- Departamento de Ciencias Médicas, Facultad de Medicina, Synaptic Structure Laboratory, Instituto de Biomedicina de la UCLM (IB-UCLM), Universidad Castilla-La Mancha, Albacete, Spain
- Laboratorio de Estructura Sináptica, Instituto de Investigación Sanitaria de Castilla-La Mancha (IDISCAM), Albacete, Spain
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2
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Homma H, Yoshioka Y, Fujita K, Shirai S, Hama Y, Komano H, Saito Y, Yabe I, Okano H, Sasaki H, Tanaka H, Okazawa H. Dynamic molecular network analysis of iPSC-Purkinje cells differentiation delineates roles of ISG15 in SCA1 at the earliest stage. Commun Biol 2024; 7:413. [PMID: 38594382 PMCID: PMC11003991 DOI: 10.1038/s42003-024-06066-z] [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: 05/03/2023] [Accepted: 03/18/2024] [Indexed: 04/11/2024] Open
Abstract
Better understanding of the earliest molecular pathologies of all neurodegenerative diseases is expected to improve human therapeutics. We investigated the earliest molecular pathology of spinocerebellar ataxia type 1 (SCA1), a rare familial neurodegenerative disease that primarily induces death and dysfunction of cerebellum Purkinje cells. Extensive prior studies have identified involvement of transcription or RNA-splicing factors in the molecular pathology of SCA1. However, the regulatory network of SCA1 pathology, especially central regulators of the earliest developmental stages and inflammatory events, remains incompletely understood. Here, we elucidated the earliest developmental pathology of SCA1 using originally developed dynamic molecular network analyses of sequentially acquired RNA-seq data during differentiation of SCA1 patient-derived induced pluripotent stem cells (iPSCs) to Purkinje cells. Dynamic molecular network analysis implicated histone genes and cytokine-relevant immune response genes at the earliest stages of development, and revealed relevance of ISG15 to the following degradation and accumulation of mutant ataxin-1 in Purkinje cells of SCA1 model mice and human patients.
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Affiliation(s)
- Hidenori Homma
- Department of Neuropathology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Yuki Yoshioka
- Department of Neuropathology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Kyota Fujita
- Department of Neuropathology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
- Research Center for Child Mental Development, Kanazawa University, 13-1 Takaramachi, Kanazawa-shi, Ishikawa, 920-8640, Japan
| | - Shinichi Shirai
- Department of Neurology, Faculty of Medicine, Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan
| | - Yuka Hama
- Department of Neurology, Faculty of Medicine, Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan
| | - Hajime Komano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Yuko Saito
- Department of Neuropathology, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan
| | - Ichiro Yabe
- Department of Neurology, Faculty of Medicine, Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Hidenao Sasaki
- Department of Neurology, Faculty of Medicine, Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan
| | - Hikari Tanaka
- Department of Neuropathology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.
| | - Hitoshi Okazawa
- Department of Neuropathology, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.
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Huang H, Shakkottai VG. Targeting Ion Channels and Purkinje Neuron Intrinsic Membrane Excitability as a Therapeutic Strategy for Cerebellar Ataxia. Life (Basel) 2023; 13:1350. [PMID: 37374132 DOI: 10.3390/life13061350] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 06/03/2023] [Accepted: 06/06/2023] [Indexed: 06/29/2023] Open
Abstract
In degenerative neurological disorders such as Parkinson's disease, a convergence of widely varying insults results in a loss of dopaminergic neurons and, thus, the motor symptoms of the disease. Dopamine replacement therapy with agents such as levodopa is a mainstay of therapy. Cerebellar ataxias, a heterogeneous group of currently untreatable conditions, have not been identified to have a shared physiology that is a target of therapy. In this review, we propose that perturbations in cerebellar Purkinje neuron intrinsic membrane excitability, a result of ion channel dysregulation, is a common pathophysiologic mechanism that drives motor impairment and vulnerability to degeneration in cerebellar ataxias of widely differing genetic etiologies. We further propose that treatments aimed at restoring Purkinje neuron intrinsic membrane excitability have the potential to be a shared therapy in cerebellar ataxia akin to levodopa for Parkinson's disease.
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Affiliation(s)
- Haoran Huang
- Medical Scientist Training Program, The Ohio State University College of Medicine, Columbus, OH 43210, USA
| | - Vikram G Shakkottai
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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4
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Martín-Belmonte A, Aguado C, Alfaro-Ruiz R, Moreno-Martínez AE, de la Ossa L, Aso E, Gómez-Acero L, Shigemoto R, Fukazawa Y, Ciruela F, Luján R. Nanoscale alterations in GABAB receptors and GIRK channel organization on the hippocampus of APP/PS1 mice. Alzheimers Res Ther 2022; 14:136. [PMID: 36131327 PMCID: PMC9490896 DOI: 10.1186/s13195-022-01078-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 09/13/2022] [Indexed: 11/10/2022]
Abstract
Alzheimer’s disease (AD) is characterized by a reorganization of brain activity determining network hyperexcitability and loss of synaptic plasticity. Precisely, a dysfunction in metabotropic GABAB receptor signalling through G protein-gated inwardly rectifying K+ (GIRK or Kir3) channels on the hippocampus has been postulated. Thus, we determined the impact of amyloid-β (Aβ) pathology in GIRK channel density, subcellular distribution, and its association with GABAB receptors in hippocampal CA1 pyramidal neurons from the APP/PS1 mouse model using quantitative SDS-digested freeze-fracture replica labelling (SDS-FRL) and proximity ligation in situ assay (P-LISA). In wild type mice, single SDS-FRL detection revealed a similar dendritic gradient for GIRK1 and GIRK2 in CA1 pyramidal cells, with higher densities in spines, and GIRK3 showed a lower and uniform distribution. Double SDS-FRL showed a co-clustering of GIRK2 and GIRK1 in post- and presynaptic compartments, but not for GIRK2 and GIRK3. Likewise, double GABAB1 and GIRK2 SDS-FRL detection displayed a high degree of co-clustering in nanodomains (40–50 nm) mostly in spines and axon terminals. In APP/PS1 mice, the density of GIRK2 and GIRK1, but not for GIRK3, was significantly reduced along the neuronal surface of CA1 pyramidal cells and in axon terminals contacting them. Importantly, GABAB1 and GIRK2 co-clustering was not present in APP/PS1 mice. Similarly, P-LISA experiments revealed a significant reduction in GABAB1 and GIRK2 interaction on the hippocampus of this animal model. Overall, our results provide compelling evidence showing a significant reduction on the cell surface density of pre- and postsynaptic GIRK1 and GIRK2, but not GIRK3, and a decline in GABAB receptors and GIRK2 channels co-clustering in hippocampal pyramidal neurons from APP/PS1 mice, thus suggesting that a disruption in the GABAB receptor–GIRK channel membrane assembly causes dysregulation in the GABAB signalling via GIRK channels in this AD animal model.
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Desai K, Aneja A, Luthra M. Lung cancer masquerading as a paraneoplastic neurologic syndrome without a primary lung mass: Case report and review of literature. Lung India 2021; 38:577-580. [PMID: 34747743 PMCID: PMC8614603 DOI: 10.4103/lungindia.lungindia_893_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Paraneoplastic and autoimmune encephalitis (AIE) syndromes describe a range of inflammatory disorders of the brain. "Classic" paraneoplastic encephalitis syndromes occur due to a remote neoplasm and are associated with antibodies that target intracellular neuronal proteins while the more recently described AIE syndromes are not always paraneoplastic and occur in association with antibodies that target cell-surface neuronal receptors (e.g., anti-NMDA receptor, anti-LGI1, anti-GABAB receptor).[1] Diagnosis can be difficult and delayed due to nonspecific clinical, imaging, and laboratory findings, and in those syndromes associated with a neoplasm, the neurologic syndromes often precede the cancer diagnosis. We present a case of a 64-year-old patient diagnosed with anti-GABAB receptor encephalitis that subsequently revealed an underlying small cell lung cancer without a primary lung tumor. This case highlights the clinical challenge in diagnosing immune-mediated encephalitis, its methodical work up, and subsequent management.
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Affiliation(s)
- Krisha Desai
- Department of Medicine, School of Medicine, J. Willis Hurst Internal Medicine Residency Program, Emory University, Atlanta, Georgia
| | - Ankur Aneja
- Department of Medicine, School of Medicine, J. Willis Hurst Internal Medicine Residency Program, Emory University, Atlanta, Georgia
| | - Munish Luthra
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, School of Medicine, Emory University, Atlanta, Georgia
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Cuadrado-Tejedor M, Pérez-González M, Alfaro-Ruiz R, Badesso S, Sucunza D, Espelosin M, Ursúa S, Lachen-Montes M, Fernández-Irigoyen J, Santamaria E, Luján R, García-Osta A. Amyloid-Driven Tau Accumulation on Mitochondria Potentially Leads to Cognitive Deterioration in Alzheimer's Disease. Int J Mol Sci 2021; 22:ijms222111950. [PMID: 34769380 PMCID: PMC8584544 DOI: 10.3390/ijms222111950] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 10/28/2021] [Accepted: 10/30/2021] [Indexed: 11/18/2022] Open
Abstract
Despite the well-accepted role of the two main neuropathological markers (β-amyloid and tau) in the progression of Alzheimer’s disease, the interaction and specific contribution of each of them is not fully elucidated. To address this question, in the present study, an adeno-associated virus (AAV9) carrying the mutant P301L form of human tau, was injected into the dorsal hippocampi of APP/PS1 transgenic mice or wild type mice (WT). Three months after injections, memory tasks, biochemical and immunohistochemical analysis were performed. We found that the overexpression of hTauP301L accelerates memory deficits in APP/PS1 mice, but it did not affect memory function of WT mice. Likewise, biochemical assays showed that only in the case of APP/PS1-hTauP301L injected mice, an important accumulation of tau was observed in the insoluble urea fraction. Similarly, electron microscopy images revealed that numerous clusters of tau immunoparticles appear at the dendrites of APP/PS1 injected mice and not in WT animals, suggesting that the presence of amyloid is necessary to induce tau aggregation. Interestingly, these tau immunoparticles accumulate in dendritic mitochondria in the APP/PS1 mice, whereas most of mitochondria in WT injected mice remain free of tau immunoparticles. Taken together, it seems that amyloid induces tau aggregation and accumulation in the dendritic mitochondria and subsequently may alter synapse function, thus, contributing to accelerate cognitive decline in APP/PS1 mice.
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Affiliation(s)
- Mar Cuadrado-Tejedor
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
- Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, 31008 Pamplona, Spain
- Correspondence: (M.C.-T.); (A.G.-O.)
| | - Marta Pérez-González
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
- Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, 31008 Pamplona, Spain
| | - Rocío Alfaro-Ruiz
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Department Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, 02008 Albacete, Spain; (R.A.-R.); (R.L.)
| | - Sara Badesso
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
- Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, 31008 Pamplona, Spain
| | - Diego Sucunza
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
| | - María Espelosin
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
| | - Susana Ursúa
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
| | - Mercedes Lachen-Montes
- Clinical Neuroproteomics Unit, Proteomics Platform, Proteored-ISCIII, Navarrabiomed, Hospital Universitario de Navarra (HUN), Universidad Pública de Navarra (UPNA), IdiSNA, 31008 Pamplona, Spain; (M.L.-M.); (J.F.-I.); (E.S.)
| | - Joaquín Fernández-Irigoyen
- Clinical Neuroproteomics Unit, Proteomics Platform, Proteored-ISCIII, Navarrabiomed, Hospital Universitario de Navarra (HUN), Universidad Pública de Navarra (UPNA), IdiSNA, 31008 Pamplona, Spain; (M.L.-M.); (J.F.-I.); (E.S.)
| | - Enrique Santamaria
- Clinical Neuroproteomics Unit, Proteomics Platform, Proteored-ISCIII, Navarrabiomed, Hospital Universitario de Navarra (HUN), Universidad Pública de Navarra (UPNA), IdiSNA, 31008 Pamplona, Spain; (M.L.-M.); (J.F.-I.); (E.S.)
| | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Department Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, 02008 Albacete, Spain; (R.A.-R.); (R.L.)
| | - Ana García-Osta
- Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, IdiSNA, 31008 Pamplona, Spain; (M.P.-G.); (S.B.); (M.E.); (S.U.)
- Correspondence: (M.C.-T.); (A.G.-O.)
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Olivero G, Vergassola M, Cisani F, Roggeri A, Pittaluga A. Presynaptic Release-regulating Metabotropic Glutamate Receptors: An Update. Curr Neuropharmacol 2021; 18:655-672. [PMID: 31775600 PMCID: PMC7457419 DOI: 10.2174/1570159x17666191127112339] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/15/2019] [Accepted: 11/22/2019] [Indexed: 12/18/2022] Open
Abstract
Metabotropic glutamate (mGlu) receptors represent the largest family of glutamate receptors in mammals and act as fine tuners of the chemical transmission in central nervous system (CNS). In the last decade, results concerning the expression and the subcellular localization of mGlu receptors further clarified their role in physio-pathological conditions. Concomitantly, their pharmacological characterization largely improved thanks to the identification of new compounds (chemical ligands and antibodies recognizing epitopic sequences of the receptor proteins) that allowed to decipher the protein compositions of the naive receptors. mGlu receptors are expressed at the presynaptic site of chemical synapses. Here, they modulate intraterminal enzymatic pathways controlling the migration and the fusion of vesicles to synaptic membranes as well as the phosphorylation of colocalized receptors. Both the control of transmitter exocytosis and the phosphorylation of colocalized receptors elicited by mGlu receptors are relevant events that dictate the plasticity of nerve terminals, and account for the main role of presynaptic mGlu receptors as modulators of neuronal signalling. The role of the presynaptic mGlu receptors in the CNS has been the matter of several studies and this review aims at briefly summarizing the recent observations obtained with isolated nerve endings (we refer to as synaptosomes). We focus on the pharmacological characterization of these receptors and on their receptor-receptor interaction / oligo-dimerization in nerve endings that could be relevant to the development of new therapeutic approaches for the cure of central pathologies.
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Affiliation(s)
| | | | | | | | - Anna Pittaluga
- Department of Pharmacy, University of Genoa, Genoa, Italy.,Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ospedale Policlinico San Martino, Genoa, Italy
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8
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Talapka P, Kocsis Z, Marsi LD, Szarvas VE, Kisvárday ZF. Application of the Mirror Technique for Three-Dimensional Electron Microscopy of Neurochemically Identified GABA-ergic Dendrites. Front Neuroanat 2021; 15:652422. [PMID: 33958990 PMCID: PMC8093522 DOI: 10.3389/fnana.2021.652422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 03/25/2021] [Indexed: 11/15/2022] Open
Abstract
In the nervous system synaptic input arrives chiefly on dendrites and their type and distribution have been assumed pivotal in signal integration. We have developed an immunohistochemistry (IH)-correlated electron microscopy (EM) method – the “mirror” technique – by which synaptic input to entire dendrites of neurochemically identified interneurons (INs) can be mapped due preserving high-fidelity tissue ultrastructure. Hence, this approach allows quantitative assessment of morphometric parameters of synaptic inputs along the whole length of dendrites originating from the parent soma. The method exploits the fact that adjoining sections have truncated or cut cell bodies which appear on the common surfaces in a mirror fashion. In one of the sections the histochemical marker of the GABAergic subtype, calbindin was revealed in cell bodies whereas in the other section the remaining part of the very same cell bodies were subjected to serial section EM to trace and reconstruct the synaptology of entire dendrites. Here, we provide exemplary data on the synaptic coverage of two dendrites belonging to the same calbindin-D28K immunopositive IN and determine the spatial distribution of asymmetric and symmetric synapses, surface area and volume of the presynaptic boutons, morphometric parameters of synaptic vesicles, and area extent of the active zones.
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Affiliation(s)
- Petra Talapka
- MTA-DE Neuroscience Research Group, University of Debrecen, Debrecen, Hungary.,Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zsolt Kocsis
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Lívia Diána Marsi
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Vera Etelka Szarvas
- Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Zoltán F Kisvárday
- MTA-DE Neuroscience Research Group, University of Debrecen, Debrecen, Hungary.,Department of Anatomy, Histology and Embryology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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9
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Irie T, Yamazaki D, Kikura-Hanajiri R. F-phenibut (β-(4-Fluorophenyl)-GABA), a potent GABA B receptor agonist, activates an outward-rectifying K + current and suppresses the generation of action potentials in mouse cerebellar Purkinje cells. Eur J Pharmacol 2020; 884:173437. [PMID: 32735986 DOI: 10.1016/j.ejphar.2020.173437] [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: 03/31/2020] [Revised: 07/27/2020] [Accepted: 07/27/2020] [Indexed: 11/15/2022]
Abstract
The GABA analog phenibut (β-Phenyl-GABA) is a GABAB receptor agonist that has been licensed for various uses in Russia. Phenibut is also available as a dietary supplement from online vendors worldwide, and previous studies have indicated that phenibut overdose results in intoxication, withdrawal symptoms, and addiction. F-phenibut (β-(4-Fluorophenyl)-GABA), a derivative of phenibut, has not been approved for clinical use. However, it is also available as a nootropic supplement from online suppliers. F-phenibut binds to GABAB with a higher affinity than phenibut; therefore, F-phenibut may lead to more serious intoxication than phenibut. However, the mechanisms by which F-phenibut acts on GABAB receptors and influences neuronal function remain unknown. In the present study, we compared the potency of F-phenibut, phenibut, and the GABAB agonist (±)-baclofen (baclofen) using in vitro patch-clamp recordings obtained from mouse cerebellar Purkinje cells slice preparations Our findings indicate that F-phenibut acted as a potent GABAB agonist. EC50 of outward current density evoked by the three GABAB agonists decreased in the following order: phenibut (1362 μM) > F-phenibut (23.3 μM) > baclofen (6.0 μM). The outward current induced by GABAB agonists was an outward-rectifying K+ current, in contrast to the previous finding that GABAB agonists activates an inward-rectifying K+ current. The K+ current recorded in the present study was insensitive to extracellular Ba2+, intra- or extracellular Cs+, and intra- or extracellular tetraethylammonium-Cl. Moreover, F-phenibut suppressed action potential generation in Purkinje cells. Thus, abuse of F-phenibut may lead to severe damage by inhibiting the excitability of GABAB-expressing neurons.
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Affiliation(s)
- Tomohiko Irie
- Division of Pharmacology, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, 210-9501, Japan.
| | - Daiju Yamazaki
- Division of Pharmacology, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, 210-9501, Japan
| | - Ruri Kikura-Hanajiri
- Division of Pharmacognosy, Phytochemistry, and Narcotics, National Institute of Health Sciences, 3-25-26 Tonomachi, Kawasaki-ku, Kawasaki City, Kanagawa, 210-9501, Japan
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10
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Alfaro-Ruíz R, Aguado C, Martín-Belmonte A, Moreno-Martínez AE, Luján R. Cellular and Subcellular Localisation of Kv4-Associated KChIP Proteins in the Rat Cerebellum. Int J Mol Sci 2020; 21:ijms21176403. [PMID: 32899153 PMCID: PMC7503578 DOI: 10.3390/ijms21176403] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 08/28/2020] [Accepted: 08/31/2020] [Indexed: 11/29/2022] Open
Abstract
The K+ channel interacting proteins (KChIPs) are a family of cytosolic proteins that interact with Kv4 channels, leading to higher current density, modulation of channel inactivation and faster recovery from inactivation. Using immunohistochemical techniques at the light and electron microscopic level combined with quantitative analysis, we investigated the cellular and subcellular localisation of KChIP3 and KChIP4 to compare their distribution patterns with those for Kv4.2 and Kv4.3 in the cerebellar cortex. Immunohistochemistry at the light microscopic level demonstrated that KChIP3, KChIP4, Kv4.2 and Kv4.3 proteins were widely expressed in the cerebellum, with mostly overlapping patterns. Immunoelectron microscopic techniques showed that KChIP3, KChIP4, Kv4.2 and Kv4.3 shared virtually the same somato-dendritic domains of Purkinje cells and granule cells. Application of quantitative approaches showed that KChIP3 and KChIP4 were mainly membrane-associated, but also present at cytoplasmic sites close to the plasma membrane, in dendritic spines and shafts of Purkinje cells (PCs) and dendrites of granule cells (GCs). Similarly, immunoparticles for Kv4.2 and Kv4.3 were observed along the plasma membrane and at intracellular sites in the same neuron populations. In addition to the preferential postsynaptic distribution, KChIPs and Kv4 were also distributed presynaptically in parallel fibres and mossy fibres. Immunoparticles for KChIP3, KChIP4 and Kv4.3 were detected in parallel fibres, and KChIP3, KChIP4, Kv4.2 and Kv4.3 were found in parallel fibres, indicating that composition of KChIP and Kv4 seems to be input-dependent. Together, our findings unravelled previously uncharacterised KChIP and Kv4 subcellular localisation patterns in neurons, revealed that KChIP have additional Kv4-unrelated functions in the cerebellum and support the formation of macromolecular complexes between KChIP3 and KChIP4 with heterotetrameric Kv4.2/Kv4.3 channels.
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Affiliation(s)
| | | | | | | | - Rafael Luján
- Correspondence: ; Tel.: +34-967-599200 (ext. 2196)
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11
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Nardone R, Sebastianelli L, Brigo F, Golaszewski S, Trinka E, Pucks-Faes E, Saltuari L, Versace V. Effects of intrathecal baclofen therapy in subjects with disorders of consciousness: a reappraisal. J Neural Transm (Vienna) 2020; 127:1209-1215. [PMID: 32710152 DOI: 10.1007/s00702-020-02233-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 07/14/2020] [Indexed: 01/16/2023]
Abstract
Baclofen is a structural analogue of gamma-amino-butyric acid (GABA), which reduces spastic hypertonia of striated muscle due to a mechanism of GABAB-ergic inhibition of mono- and polysynaptic reflexes at the spinal level. There are reports of patients with severe disorders of consciousness that presented a substantial improvement following intrathecal baclofen (ITB) administration for severe spasticity. The neural mechanisms underlying the clinical recovery after ITB have not yet been clarified. Baclofen could modulate sleep-wake cycles that may be dysregulated and thus interfere with alertness and awareness. The diminished proprioceptive and nociceptive sensory inputs may relieve thalamo-cortical neural networks involved in maintaining the consciousness of the self and the world. ITB treatment might also promote the recovery of an impaired GABAergic cortical tone, restoring the balance between excitatory and inhibitory cortical activity. Furthermore, glutamatergic synapses are directly or indirectly modulated by GABAB-ergic receptors. Neurophysiological techniques (such as transcranial magnetic stimulation, electroencephalography, or the combination of both) can be helpful to explore the effects of intrathecal or oral baclofen on the modulation of neural cortical circuits in humans with disorders of consciousness.
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Affiliation(s)
- Raffaele Nardone
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy. .,Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria. .,Spinal Cord Injury and Tissue Regeneration Center, Salzburg, Austria. .,Karl Landsteiner Institut für Neurorehabilitation und Raumfahrtneurologie, Salzburg, Austria.
| | - Luca Sebastianelli
- Department of Neurorehabilitation, Hospital of Vipiteno, Vipiteno, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
| | - Francesco Brigo
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy.,Department of Neuroscience, Biomedicine and Movement Science, University of Verona, Verona, Italy
| | - Stefan Golaszewski
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.,Karl Landsteiner Institut für Neurorehabilitation und Raumfahrtneurologie, Salzburg, Austria
| | - Eugen Trinka
- Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University, Salzburg, Austria.,Centre for Cognitive Neurosciences Salzburg, Salzburg, Austria.,University for Medical Informatics and Health Technology, UMIT, Hall in Tirol, Austria
| | | | - Leopold Saltuari
- Department of Neurorehabilitation, Hospital of Vipiteno, Vipiteno, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
| | - Viviana Versace
- Department of Neurology, Hospital of Merano (SABES-ASDAA), Merano-Meran, Italy.,Research Unit for Neurorehabilitation South Tyrol, Bolzano, Italy
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12
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Pérez-González M, Mendioroz M, Badesso S, Sucunza D, Roldan M, Espelosín M, Ursua S, Luján R, Cuadrado-Tejedor M, Garcia-Osta A. PLA2G4E, a candidate gene for resilience in Alzheimer´s disease and a new target for dementia treatment. Prog Neurobiol 2020; 191:101818. [PMID: 32380223 DOI: 10.1016/j.pneurobio.2020.101818] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/27/2020] [Accepted: 04/23/2020] [Indexed: 12/16/2022]
Abstract
Clinical studies revealed that some aged-individuals accumulate a significant number of histopathological Alzheimer´s disease (AD) lesions in their brain, yet without developing any signs of dementia. Animal models of AD represent suitable tools to identify genes that might promote cognitive resilience and hence, this study first set out to identify cognitively resilient individuals in the aged-Tg2576 mouse model. A transcriptomic analysis of these mice identified PLA2G4E as a gene that might confer resistance to dementia. Indeed, a significant decrease in PLA2G4E is evident in the brain of late-stage AD patients, whereas no such changes are observed in early stage patients with AD neuropathological lesions but no signs of dementia. We demonstrated that adeno-associated viral vector-mediated overexpression of PLA2G4E in hippocampal neurons completely restored cognitive deficits in elderly APP/PS1 mice, without affecting the amyloid or tau pathology. These PLA2G4E overexpressing APP/PS1 mice developed significantly more dendritic spines than sham-injected mice, coinciding with the cognitive improvement observed. Hence, these results support the idea that a loss of PLA2G4E might play a key role in the onset of dementia in AD, highlighting the potential of PLA2G4E overexpression as a novel therapeutic strategy to manage AD and other disorders that course with memory deficits.
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Affiliation(s)
- Marta Pérez-González
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain
| | - Maite Mendioroz
- IdiSNA (Navarra Institute for Health Research) Pamplona, Spain; Neuroepigenetics Laboratory, Navarrabiomed, Public University of Navarra (UPNA), Pamplona, Spain; Department of Neurology, Complejo Hospitalario de Navarra, Pamplona, Spain
| | - Sara Badesso
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain
| | - Diego Sucunza
- Parkinson´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain
| | - Miren Roldan
- IdiSNA (Navarra Institute for Health Research) Pamplona, Spain; Neuroepigenetics Laboratory, Navarrabiomed, Public University of Navarra (UPNA), Pamplona, Spain
| | - Maria Espelosín
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain
| | - Susana Ursua
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain
| | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
| | - Mar Cuadrado-Tejedor
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; Department of Pathology, Anatomy and Physiology, School of Medicine, University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain.
| | - Ana Garcia-Osta
- Alzheimer´s Disease, Neurosciences Program, Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; IdiSNA (Navarra Institute for Health Research) Pamplona, Spain.
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13
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Density of GABA B Receptors Is Reduced in Granule Cells of the Hippocampus in a Mouse Model of Alzheimer's Disease. Int J Mol Sci 2020; 21:ijms21072459. [PMID: 32252271 PMCID: PMC7177735 DOI: 10.3390/ijms21072459] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/27/2020] [Accepted: 03/31/2020] [Indexed: 12/22/2022] Open
Abstract
Metabotropic γ-aminobutyric acid (GABAB) receptors contribute to the control of network activity and information processing in hippocampal circuits by regulating neuronal excitability and synaptic transmission. The dysfunction in the dentate gyrus (DG) has been implicated in Alzheimer´s disease (AD). Given the involvement of GABAB receptors in AD, to determine their subcellular localisation and possible alteration in granule cells of the DG in a mouse model of AD at 12 months of age, we used high-resolution immunoelectron microscopic analysis. Immunohistochemistry at the light microscopic level showed that the regional and cellular expression pattern of GABAB1 was similar in an AD model mouse expressing mutated human amyloid precursor protein and presenilin1 (APP/PS1) and in age-matched wild type mice. High-resolution immunoelectron microscopy revealed a distance-dependent gradient of immunolabelling for GABAB receptors, increasing from proximal to distal dendrites in both wild type and APP/PS1 mice. However, the overall density of GABAB receptors at the neuronal surface of these postsynaptic compartments of granule cells was significantly reduced in APP/PS1 mice. Parallel to this reduction in surface receptors, we found a significant increase in GABAB1 at cytoplasmic sites. GABAB receptors were also detected at presynaptic sites in the molecular layer of the DG. We also found a decrease in plasma membrane GABAB receptors in axon terminals contacting dendritic spines of granule cells, which was more pronounced in the outer than in the inner molecular layer. Altogether, our data showing post- and presynaptic reduction in surface GABAB receptors in the DG suggest the alteration of the GABAB-mediated modulation of excitability and synaptic transmission in granule cells, which may contribute to the cognitive dysfunctions in the APP/PS1 model of AD.
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14
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Martín-Belmonte A, Aguado C, Alfaro-Ruíz R, Moreno-Martínez AE, de la Ossa L, Martínez-Hernández J, Buisson A, Früh S, Bettler B, Shigemoto R, Fukazawa Y, Luján R. Reduction in the neuronal surface of post and presynaptic GABA B receptors in the hippocampus in a mouse model of Alzheimer's disease. Brain Pathol 2019; 30:554-575. [PMID: 31729777 PMCID: PMC7317930 DOI: 10.1111/bpa.12802] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 11/04/2019] [Indexed: 12/25/2022] Open
Abstract
The hippocampus plays key roles in learning and memory and is a main target of Alzheimer's disease (AD), which causes progressive memory impairments. Despite numerous investigations about the processes required for the normal hippocampal functions, the neurotransmitter receptors involved in the synaptic deficits by which AD disables the hippocampus are not yet characterized. By combining histoblots, western blots, immunohistochemistry and high-resolution immunoelectron microscopic methods for GABAB receptors, this study provides a quantitative description of the expression and the subcellular localization of GABAB1 in the hippocampus in a mouse model of AD at 1, 6 and 12 months of age. Western blots and histoblots showed that the total amount of protein and the laminar expression pattern of GABAB1 were similar in APP/PS1 mice and in age-matched wild-type mice. In contrast, immunoelectron microscopic techniques showed that the subcellular localization of GABAB1 subunit did not change significantly in APP/PS1 mice at 1 month of age, was significantly reduced in the stratum lacunosum-moleculare of CA1 pyramidal cells at 6 months of age and significantly reduced at the membrane surface of CA1 pyramidal cells at 12 months of age. This reduction of plasma membrane GABAB1 was paralleled by a significant increase of the subunit at the intracellular sites. We further observed a decrease of membrane-targeted GABAB receptors in axon terminals contacting CA1 pyramidal cells. Our data demonstrate compartment- and age-dependent reduction of plasma membrane-targeted GABAB receptors in the CA1 region of the hippocampus, suggesting that this decrease might be enough to alter the GABAB -mediated synaptic transmission taking place in AD.
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Affiliation(s)
- Alejandro Martín-Belmonte
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
| | - Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
| | - Rocío Alfaro-Ruíz
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
| | - Ana Esther Moreno-Martínez
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
| | - Luis de la Ossa
- Departamento de Sistemas Informáticos, Escuela Superior de Ingeniería Informática, Universidad de Castilla-La Mancha, 02071, Albacete, Spain
| | - José Martínez-Hernández
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
| | - Alain Buisson
- Grenoble Institut des Neurosciences, Université Grenoble Alpes, BP 170, Grenoble, France
| | - Simon Früh
- Department of Biomedicine, Institute of Physiology, University of Basel, Basel, Switzerland
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, University of Basel, Basel, Switzerland
| | - Ryuichi Shigemoto
- Institute of Science and Technology (IST Austria), Am Campus 1, A-3400, Klosterneuburg, Austria
| | - Yugo Fukazawa
- Division of Brain Structure and Function, Faculty of Medical Science, University of Fukui, Fukui, Japan.,Life Science Innovation Center, University of Fukui, Fukui, Japan.,Research Center for Child Mental Development, Faculty of Medical Science, University of Fukui, Fukui, Japan
| | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/ Almansa 14, 02008, Albacete, Spain
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15
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Typical clinical and imaging manifestations of encephalitis with anti-γ-aminobutyric acid B receptor antibodies: clinical experience and a literature review. Neurol Sci 2019; 40:769-777. [PMID: 30671737 DOI: 10.1007/s10072-018-3679-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 12/06/2018] [Indexed: 12/28/2022]
Abstract
OBJECTIVE To explore the clinical, imaging, and electroencephalogram (EEG) findings, as well as the treatment and prognosis of five patients with anti-γ-aminobutyric acid B receptor (GABABR) encephalitis and review the current literature to gain a deeper understanding and improve the clinical diagnostic ability of the disease. METHODS Clinical data such as blood examination, imaging, computed tomography (CT), EEG, and magnetic resonance imaging (MRI) findings from five patients with anti-GABABR encephalitis were retrospectively analyzed. RESULTS Based on the imaging data, autoimmune encephalitis with anti-GABABR antibodies displayed subacute onset of episodic memory loss, seizures, and confusion, in addition to signal changes in the medial temporal lobe and/or hippocampus. Anti-GABABR antibodies were found in blood and cerebrospinal fluid (CSF) in all five patients, although the CSF leukocyte count and the levels of protein, sugar, and chloride showed no obvious abnormalities. On MRI, only two patients presented with abnormal signals in the medial temporal lobe and/or hippocampus. The EEG showed a slow wave rhythm in all five patients. After treatment with methylprednisolone pulse therapy combined with antiepileptic treatment, all five patients recovered well, without any complications. CONCLUSIONS Autoimmune encephalitis with anti-GABABR antibodies may be a severe and refractory disease. Anti-GABABR antibodies tested in CSF and serum play a crucial role in the definitive diagnosis and treatment of autoimmune encephalitis. Early treatment is of vital importance to avoid serious complications and neurological sequelae.
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16
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Vergassola M, Olivero G, Cisani F, Usai C, Bossi S, Puliti A, Pittaluga A. Presynaptic mGlu1 Receptors Control GABA B Receptors in an Antagonist-Like Manner in Mouse Cortical GABAergic and Glutamatergic Nerve Endings. Front Mol Neurosci 2018; 11:324. [PMID: 30279647 PMCID: PMC6153310 DOI: 10.3389/fnmol.2018.00324] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 08/22/2018] [Indexed: 01/03/2023] Open
Abstract
Mouse cortical GABAergic synaptosomes possess presynaptic inhibitory GABAB autoreceptors. Accordingly, (±)baclofen (3 μM) inhibits in a CGP53423-sensitive manner the 12 mM KCl-evoked release of preloaded [3H]GABA. Differently, the existence of presynaptic release-regulating metabotropic glutamate type 1 (mGlu1) heteroreceptors in these terminals is still matter of discussion, although confocal microscopy unveiled the existence of mGlu1α with GABAB1 or GABAB2 proteins in cortical VGAT-positive synaptosomes. The group I mGlu agonist 3,5-DHPG failed to modify on its own the 12 mM KCl-evoked [3H]GABA exocytosis from cortical nerve endings, but, when added concomitantly to the GABAB agonist, it significantly reduced the 3 μM (±)baclofen-induced inhibition of [3H]GABA exocytosis. Conversely, the mGlu1 antagonist LY367385 (0.03–1 μM), inactive on its own on GABA exocytosis, amplified the 3 μM (±)baclofen-induced inhibition of [3H]GABA overflow. The ( ± )baclofen-induced inhibition of [3H]GABA exocytosis was more pronounced in cortical synaptosomes from Grm1crv4/crv4 mice, which bear a spontaneous mutation of the Grm1 gene leading to the functional inactivation of the mGlu1 receptor. Inasmuch, the expression of GABAB2 receptor protein in cortical synaptosomal lysates from Grm1crv4/crv4 mice was increased when compared to controls. Altogether, these observations seem best interpreted by assuming that mGlu1 coexist with GABAB receptors in GABAergic cortical synaptosomes, where they control GABA receptors in an antagonist-like manner. We then asked whether the mGlu1-mediated control of GABAB receptors is restricted to GABAergic terminals, or if it occurs also in other subpopulations of nerve endings. Release-regulating GABAB receptors also exist in glutamatergic nerve endings. (±)baclofen (1 μM) diminished the 12 mM KCl-evoked [3H]D-aspartate overflow. Also in these terminals, the concomitant presence of 1 μM LY367385, inactive on its own, significantly amplified the inhibitory effect exerted by (±)baclofen on [3H]D-aspartate exocytosis. Confocal microscopy confirmed the colocalization of mGlu1 with GABAB1 and GABAB2 labeling in vesicular glutamate type1 transporter-positive particles. Our results support the conclusion that mGlu1 receptors modulate in an antagonist-like manner presynaptic release-regulating GABAB receptors. This receptor–receptor interaction could be neuroprotective in central disease typified by hyperglutamatergicity.
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Affiliation(s)
| | | | | | - Cesare Usai
- Institute of Biophysics, National Research Council, Genoa, Italy
| | - Simone Bossi
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, Genoa, Italy
| | - Aldamaria Puliti
- Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, Genoa, Italy.,IRCCS Istituto Giannina Gaslini, Genoa, Italy.,Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Anna Pittaluga
- Department of Pharmacy, University of Genoa, Genoa, Italy.,Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
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17
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Tian J, Zhu MX. GABA B Receptors Augment TRPC3-Mediated Slow Excitatory Postsynaptic Current to Regulate Cerebellar Purkinje Neuron Response to Type-1 Metabotropic Glutamate Receptor Activation. Cells 2018; 7:cells7080090. [PMID: 30060610 PMCID: PMC6116156 DOI: 10.3390/cells7080090] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2018] [Revised: 07/18/2018] [Accepted: 07/27/2018] [Indexed: 02/02/2023] Open
Abstract
During strong parallel fiber stimulation, glutamate released at parallel fiber-Purkinje cell synapses activates type-1 metabotropic glutamate receptor (mGluR1) to trigger a slow excitatory postsynaptic current (sEPSC) in cerebellar Purkinje neurons. The sEPSC is mediated by transient receptor potential canonical 3 (TRPC3) channels. Often co-localized with mGluR1 in Purkinje neuron dendrites are type B γ-aminobutyric acid receptors (GABABRs) that respond to inhibitory synaptic inputs from interneurons located in the molecular layer of cerebellar cortex. It has been shown that activation of postsynaptic GABABRs potentiates mGluR1 activation-evoked sEPSC in Purkinje cells, but the underlying molecular mechanism remains elusive. Here we report that the augmentation of mGluR1-sEPSC by GABABR activation in Purkinje neurons is completely absent in TRPC3 knockout mice, but totally intact in TRPC1-, TRPC4-, and TRPC1,4,5,6-knockout mice, suggesting that TRPC3 is the only TRPC isoform that mediates the potentiation. Moreover, our results indicate that the potentiation reflects a postsynaptic mechanism that requires both GABABRs and mGluR1 because it is unaffected by blocking neurotransmission with tetrodotoxin but blocked by inhibiting either GABABRs or mGluR1. Furthermore, we show that the co-stimulation of GABABRs has an effect on shaping the response of Purkinje cell firing to mGluR1-sEPSC, revealing a new function of inhibitory input on excitatory neurotransmission. We conclude that postsynaptic GABABRs regulate Purkinje cell responses to strong glutamatergic stimulation through modulation of mGluR1-TRPC3 coupling. Since mGluR1-TRPC3 coupling is essential in cerebellar long-term depression, synapse elimination, and motor coordination, our findings may have implications in essential cerebellar functions, such as motor coordination and learning.
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Affiliation(s)
- Jinbin Tian
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
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18
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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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Chen X, Liu F, Li JM, Xie XQ, Wang Q, Zhou D, Shang H. Encephalitis with antibodies against the GABA B receptor: seizures as the most common presentation at admission. Neurol Res 2017; 39:973-980. [PMID: 28974152 DOI: 10.1080/01616412.2017.1351062] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE Autoimmune encephalitis associated with antibodies against gamma-aminobutyric-acid B receptor (GABABR) has not been described in detail in Chinese patients. METHODS Patients with anti-GABABR encephalitis treated between January 2013 and December 2015 were analyzed in terms of clinical characteristics, laboratory findings, tumor presence, autoantibody patterns, treatment response and outcomes. RESULTS Eleven patients were identified (male, N = 8; female, N = 3), with the median age of 51 years. All patients presented with seizures (N = 11; 100%), and they were given anti-epileptic drugs and first-line immunotherapy to address the disease. Seizures always accompanied by limbic manifestations (N = 10; 90.9%). Extralimbic manifestations were present in 4 patients (N = 4; 36.4%). MRI Brain abnormality with increased medio-temporal lobe T2/FLAIR signal were present in 2 patients (N = 2; 18.2%), and epileptiform epileptiform activity on electroencephalography were observed in 2 patients (N = 2; 18.2%). Small-cell lung cancer was histologically confirmed in 3 patients (N = 3; 27.3%). Seven patients showed good outcomes (mRS 1-2; N = 7; 63.6%), one patient showed poor neurological status with minimal changes (mRS 4; N = 1; 9.1%), and three patients died during follow-up (mRS = 6; N = 3; 27.3%). Outcomes were correlated with age-of-onset, and were worse among older patients (P = 0.0112). CONCLUSION Anti-GABABR encephalitis is a potentially treatable disorder involving seizures as the most predominant presentation at admission. It should be considered as a possible diagnosis in middle-aged and older patients with refractory new-onset epilepsy.
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Affiliation(s)
- Xueping Chen
- a Department of Neurology , West China Hospital, Sichuan University , Chengdu , China
| | - Fan Liu
- b Department of Nursing , West China Hospital of Stomatology, Sichuan University , Chengdu , China
| | - Jin-Mei Li
- a Department of Neurology , West China Hospital, Sichuan University , Chengdu , China
| | - Xiao-Qi Xie
- c Neurological Intensive Care Unit , West China Hospital, Sichuan University , Chengdu , China
| | - Qiong Wang
- c Neurological Intensive Care Unit , West China Hospital, Sichuan University , Chengdu , China
| | - Dong Zhou
- a Department of Neurology , West China Hospital, Sichuan University , Chengdu , China
| | - Huifang Shang
- a Department of Neurology , West China Hospital, Sichuan University , Chengdu , China
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Guan HZ, Ren HT, Yang XZ, Lu Q, Peng B, Zhu YC, Shao XQ, Hu YQ, Zhou D, Cui LY. Limbic Encephalitis Associated with Anti-γ-aminobutyric Acid B Receptor Antibodies: A Case Series from China. Chin Med J (Engl) 2016; 128:3023-8. [PMID: 26608981 PMCID: PMC4795264 DOI: 10.4103/0366-6999.168989] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Background: Autoimmune encephalitis associated with antibodies against γ-aminobutyric acid B receptor (GABAB R) in patients with limbic encephalitis (LE) was first described in 2010. We present a series of Han Chinese patients for further clinical refinement. Methods: Serum and cerebrospinal fluid (CSF) samples from patients referred to the program of encephalitis and paraneoplastic syndrome of Peking Union Medical College Hospital were tested with indirect immunofluorescence. Clinical information of patients with anti-GABAB R antibody positivity was retrospectively reviewed, and descriptive statistical analysis was performed. Results: All eighteen anti-GABAB R antibody-positive cases had limbic syndromes, and electroencephalogram (EEG) or neuroimaging evidence fulfilled the diagnostic criteria of LE. Four patients had additional antibodies against Hu in serum and one had anti-N-methyl-d-aspartate receptor antibody in both sera and CSF. Seventeen (17/18) patients presented with new-onset refractory seizure or status epileptics. Twelve (12/18) patients had memory deficits, 11 (11/18) patients had personality change, 7 (7/18) patients had disturbance of consciousness, and 3 (3/18) patients showed cerebellar dysfunction. One patient with LE had progressive motor and sensory polyneuropathy. Lung cancer was detected in 6 (6/18) patients. Ten (10/18) patients showed abnormality in bilateral or unilateral mediotemporal region on magnetic resonance imaging. Ten (10/18) patients had temporal lobe epileptic activity with or without general slowing on EEG. Seventeen patients received immunotherapy and 15 of them showed neurological improvement. Four patients with lung cancer died within 1–12 months due to neoplastic complications. Conclusions: Our study demonstrates that most Han Chinese patients with anti-GABAB R antibody-associated LE have prominent refractory epilepsy and show neurological improvement on immunotherapy. Patients with underlying lung tumor have a relatively poor prognosis. Testing for anti-GABAB R antibodies is necessary for patients with possible LE or new-onset epilepsy with unknown etiology.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Li-Ying Cui
- Department of Neurology, Peking Union Medical College Hospital; Neuroscience Center, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China
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Aguado C, Orlandi C, Fajardo-Serrano A, Gil-Minguez M, Martemyanov KA, Luján R. Cellular and Subcellular Localization of the RGS7/Gβ5/R7BP Complex in the Cerebellar Cortex. Front Neuroanat 2016; 10:114. [PMID: 27965545 PMCID: PMC5127842 DOI: 10.3389/fnana.2016.00114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 11/10/2016] [Indexed: 11/13/2022] Open
Abstract
A member of regulator of G-protein signaling family, RGS7, is an essential modulator of signaling through GABAB receptors. RGS7 functions as a macromolecular complex with type 5 G protein β (Gβ5) and R7 binding protein (R7BP) to control the localization and function of the resultant heterotrimeric complexes. Here, we used co-immunoprecipitation, in situ hybridization, histoblot and immunohistochemical techniques at the light and electron microscopic level to advance understanding of RGS7-Gβ5-R7BP complexes in the central nervous system, focusing on distinct neuronal populations in the cerebellar cortex. Histoblot analysis showed that RGS7, Gβ5 and R7BP proteins were widely expressed in the brain, with mostly an overlapping pattern and showing a high expression level in the molecular layer of the cerebellar cortex. Co-immunoprecipitation experiments established that the RGS7/Gβ5 forms complexes with R7BP in the cerebellum. At the cellular level, RGS7 and R7BP mRNAs were expressed at the highest level in Purkinje cells (PCs) and Golgi cells, and at low levels in granule cells. Immunohistochemistry confirmed that labeling for RGS7, Gβ5 and R7BP were present in the three neuronal populations and concentrated in dendrites and spines. At the electron microscopic level, immunolabeling for RGS7, Gβ5 and R7BP proteins was found both at postsynaptic and presynaptic sites and showed similar distribution patterns. Immunoreactivity for the three proteins was mostly localized along the extrasynaptic plasma membrane of dendritic shafts and spines of PCs and to a lesser extent, in axon terminals (AT) establishing excitatory synapses. Quantitative analysis of immunogold particles for RGS7, Gβ5 and R7BP revealed that they are non-uniformly distributed along the surface of PCs, and show enrichment around excitatory synapses on dendritic spines. We further report that deletion of R7BP in mice reduced the targeting of both RGS7 and Gβ5 to the plasma membrane. Altogether, these data support the existence of macromolecular complexes composed of RGS7-Gβ5-R7BP in PCs. The location at post- and pre-synaptic sites in PCs spines-parallel fiber synapses suggests their involvement in the modulation of glutamatergic neurotransmission in the cerebellar cortex.
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Affiliation(s)
- Carolina Aguado
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Cesare Orlandi
- Department of Neuroscience, The Scripps Research Institute Jupiter, FL, USA
| | - Ana Fajardo-Serrano
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Mercedes Gil-Minguez
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | | | - Rafael Luján
- Synaptic Structure Laboratory, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
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Aguado C, García-Madrona S, Gil-Minguez M, Luján R. Ontogenic Changes and Differential Localization of T-type Ca(2+) Channel Subunits Cav3.1 and Cav3.2 in Mouse Hippocampus and Cerebellum. Front Neuroanat 2016; 10:83. [PMID: 27616982 PMCID: PMC4999439 DOI: 10.3389/fnana.2016.00083] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/11/2016] [Indexed: 12/31/2022] Open
Abstract
T-type calcium (Ca(2+)) channels play a central role in regulating membrane excitability in the brain. Although the contributions of T-type current to neuron output is often proposed to reflect a differential distribution of T-type channel subtypes to somato-dendritic compartments, their precise subcellular distributions in central neurons are not fully determined. Using histoblot and high-resolution immunoelectron microscopic techniques, we have investigated the expression, regional distribution and subcellular localization of T-type Cav3.1 and Cav3.2 channel subunits in the adult brain, as well as the ontogeny of expression during postnatal development. Histoblot analysis showed that Cav3.1 and Cav3.2 proteins were widely expressed in the brain, with mostly non-overlapping patterns. Cav3.1 showed the highest expression level in the molecular layer (ml) of the cerebellum (Cb), and Cav3.2 in the hippocampus (Hp) and the ml of Cb. During development, levels of Cav3.1 and Cav3.2 increased with age, although there were marked region- and developmental stage-specific differences in their expression. At the cellular and subcellular level, immunoelectron microscopy showed that labeling for Cav3.1 was present in somato-dendritic domains of hippocampal interneurons and Purkinje cells (PCs), while Cav3.2 was present in somato-dendritic domains of CA1 pyramidal cells, hippocampal interneurons and PCs. Most of the immunoparticles for Cav3.1 and Cav3.2 were either associated with the plasma membrane or the intracellular membranes, with notable differences depending on the compartment. Thus, Cav3.1 was mainly located in the plasma membrane of interneurons, whereas Cav3.2 was mainly located in the plasma membrane of dendritic spines and had a major intracellular distribution in dendritic shafts. In PCs, Cav3.1 and Cav3.2 showed similar distribution patterns. In addition to its main postsynaptic distribution, Cav3.2 but not Cav3.1 was also detected in axon terminals establishing excitatory synapses. These results shed new light on the subcellular localization of T-type channel subunits and provide evidence for the non-uniform distribution of Cav3.1 and Cav3.2 subunits over the plasma membrane of central neurons, which may account for the functional heterogeneity of T-type mediated current.
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Affiliation(s)
- Carolina Aguado
- Synaptic Structure Laboratory, Department Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Sebastián García-Madrona
- Synaptic Structure Laboratory, Department Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Mercedes Gil-Minguez
- Synaptic Structure Laboratory, Department Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
| | - Rafael Luján
- Synaptic Structure Laboratory, Department Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Spain
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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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Bragina L, Bonifacino T, Bassi S, Milanese M, Bonanno G, Conti F. Differential expression of metabotropic glutamate and GABA receptors at neocortical glutamatergic and GABAergic axon terminals. Front Cell Neurosci 2015; 9:345. [PMID: 26388733 PMCID: PMC4559644 DOI: 10.3389/fncel.2015.00345] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 08/18/2015] [Indexed: 12/04/2022] Open
Abstract
Metabotropic glutamate (Glu) receptors (mGluRs) and GABAB receptors are highly expressed at presynaptic sites. To verify the possibility that the two classes of metabotropic receptors contribute to axon terminals heterogeneity, we studied the localization of mGluR1α, mGluR5, mGluR2/3, mGluR7, and GABAB1 in VGLUT1-, VGLUT2-, and VGAT- positive terminals in the cerebral cortex of adult rats. VGLUT1-positive puncta expressed mGluR1α (∼5%), mGluR5 (∼6%), mGluR2/3 (∼22%), mGluR7 (∼17%), and GABAB1 (∼40%); VGLUT2-positive terminals expressed mGluR1α (∼10%), mGluR5 (∼11%), mGluR2/3 (∼20%), mGluR7 (∼28%), and GABAB1 (∼25%); whereas VGAT-positive puncta expressed mGluR1α (∼27%), mGluR5 (∼24%), mGluR2/3 (∼38%), mGluR7 (∼31%), and GABAB1 (∼19%). Control experiments ruled out the possibility that postsynaptic mGluRs and GABAB1 might have significantly biased our results. We also performed functional assays in synaptosomal preparations, and showed that all agonists modify Glu and GABA levels, which return to baseline upon exposure to antagonists. Overall, these findings indicate that mGluR1α, mGluR5, mGluR2/3, mGluR7, and GABAB1 expression differ significantly between glutamatergic and GABAergic axon terminals, and that the robust expression of heteroreceptors may contribute to the homeostatic regulation of the balance between excitation and inhibition.
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Affiliation(s)
- Luca Bragina
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
- Center for Neurobiology of Aging, Istituto Nazionale di Riposo e Cura per Anziani – Istituto di Ricovero e Cura a Carattere ScientificoAncona, Italy
| | - Tiziana Bonifacino
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
| | - Silvia Bassi
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
| | - Marco Milanese
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
| | - Giambattista Bonanno
- Department of Pharmacy, Unit of Pharmacology and Toxicology, University of GenoaGenoa, Italy
- Center of Excellence for Biomedical Research, University of GenoaGenoa, Italy
| | - Fiorenzo Conti
- Section of Neuroscience and Cell Biology, Department of Experimental and Clinical Medicine, Università Politecnica delle MarcheAncona, Italy
- Center for Neurobiology of Aging, Istituto Nazionale di Riposo e Cura per Anziani – Istituto di Ricovero e Cura a Carattere ScientificoAncona, Italy
- Fondazione di Medicina Molecolare, Università Politecnica delle MarcheAncona, Italy
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25
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Kantamneni S. Cross-talk and regulation between glutamate and GABAB receptors. Front Cell Neurosci 2015; 9:135. [PMID: 25914625 PMCID: PMC4392697 DOI: 10.3389/fncel.2015.00135] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/23/2015] [Indexed: 12/16/2022] Open
Abstract
Brain function depends on co-ordinated transmission of signals from both excitatory and inhibitory neurotransmitters acting upon target neurons. NMDA, AMPA and mGluR receptors are the major subclasses of glutamate receptors that are involved in excitatory transmission at synapses, mechanisms of activity dependent synaptic plasticity, brain development and many neurological diseases. In addition to canonical role of regulating presynaptic release and activating postsynaptic potassium channels, GABAB receptors also regulate glutamate receptors. There is increasing evidence that metabotropic GABAB receptors are now known to play an important role in modulating the excitability of circuits throughout the brain by directly influencing different types of postsynaptic glutamate receptors. Specifically, GABAB receptors affect the expression, activity and signaling of glutamate receptors under physiological and pathological conditions. Conversely, NMDA receptor activity differentially regulates GABAB receptor subunit expression, signaling and function. In this review I will describe how GABAB receptor activity influence glutamate receptor function and vice versa. Such a modulation has widespread implications for the control of neurotransmission, calcium-dependent neuronal function, pain pathways and in various psychiatric and neurodegenerative diseases.
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Affiliation(s)
- Sriharsha Kantamneni
- Bradford School of Pharmacy, School of Life Sciences, University of Bradford Bradford, West Yorkshire, UK
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26
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Filip M, Frankowska M, Sadakierska-Chudy A, Suder A, Szumiec Ł, Mierzejewski P, Bienkowski P, Przegaliński E, Cryan JF. GABAB receptors as a therapeutic strategy in substance use disorders: Focus on positive allosteric modulators. Neuropharmacology 2015; 88:36-47. [DOI: 10.1016/j.neuropharm.2014.06.016] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/10/2014] [Accepted: 06/15/2014] [Indexed: 12/16/2022]
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Luján R, Aguado C. Localization and Targeting of GIRK Channels in Mammalian Central Neurons. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:161-200. [PMID: 26422985 DOI: 10.1016/bs.irn.2015.05.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
G protein-gated inwardly rectifying K(+) (GIRK/K(ir)3) channels are critical to brain function. They hyperpolarize neurons in response to activation of different G protein-coupled receptors, reducing cell excitability. Molecular cloning has revealed four distinct mammalian genes (GIRK1-4), which, with the exception of GIRK4, are broadly expressed in the central nervous system (CNS) and have been implicated in a variety of neurological disorders. Although the molecular structure and composition of GIRK channels are key determinants of their biophysical properties, their cellular and subcellular localization patterns and densities on the neuronal surface are just as important to nerve function. Current data obtained with high-resolution quantitative localization techniques reveal complex, subcellular compartment-specific distribution patterns of GIRK channel subunits. Recent efforts have focused on determining the associated proteins that form macromolecular complexes with GIRK channels. Demonstration of the precise subcellular compartmentalization of GIRK channels and their associated proteins represents a crucial step in understanding the contribution of these channels to specific aspects of neuronal function under both physiological and pathological conditions. Here, we present an overview of studies aimed at determining the cellular and subcellular localization of GIRK channel subunits in mammalian brain neurons and discuss implications for neuronal physiology.
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Affiliation(s)
- Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain.
| | - Carolina Aguado
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
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28
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Ballesteros-Merino C, Martínez-Hernández J, Aguado C, Watanabe M, Adelman JP, Luján R. Localization of SK2 channels relative to excitatory synaptic sites in the mouse developing Purkinje cells. Front Neuroanat 2014; 8:154. [PMID: 25565979 PMCID: PMC4266016 DOI: 10.3389/fnana.2014.00154] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 11/25/2014] [Indexed: 11/18/2022] Open
Abstract
Small-conductance, Ca2+-activated K+ (SK) channels regulate neuronal excitability in a variety of ways. To understand their roles in different neuronal subtypes it is important to determine their precise subcellular distribution. Here, we used biochemical, light microscopy immunohistochemical and immunoelectron microscopy techniques, combined with quantitative approaches, to reveal the expression and subcellular localization patterns of SK2 in the developing cerebellum. Using western blots, the SK2 protein showed a progressive increase during postnatal development. At the light microscopic level, SK2 immunoreactivity was very prominent in the developing Purkinje cells (PC), particularly in the molecular layer (ML). Electron microscopy revealed that throughout development SK2 was mostly detected at the extrasynaptic and perisynaptic plasma membrane of dendritic shafts and dendritic spines of PCs. However, there was some localization at axon terminals as well. Quantitative analyses and 3D reconstructions further revealed a progressive developmental change of SK2 on the surface of PCs from dendritic shafts to dendritic spines. Together, these results indicate that SK2 channels undergo dynamic spatial regulation during cerebellar development, and this process is associated with the formation and maturation of excitatory synaptic contacts to PCs.
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Affiliation(s)
- Carmen Ballesteros-Merino
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Albacete, Spain
| | - José Martínez-Hernández
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Albacete, Spain
| | - Carolina Aguado
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Albacete, Spain
| | - Masahiko Watanabe
- Department of Anatomy, Hokkaido University School of Medicine Sapporo, Japan
| | - John P Adelman
- Vollum Institute, Oregon Health and Science University Portland, OR, USA
| | - Rafael Luján
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha Albacete, Albacete, Spain
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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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Kantamneni S, Gonzàlez-Gonzàlez IM, Luo J, Cimarosti H, Jacobs SC, Jaafari N, Henley JM. Differential regulation of GABAB receptor trafficking by different modes of N-methyl-D-aspartate (NMDA) receptor signaling. J Biol Chem 2014; 289:6681-6694. [PMID: 24425870 PMCID: PMC3945329 DOI: 10.1074/jbc.m113.487348] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 12/24/2013] [Indexed: 12/31/2022] Open
Abstract
Inhibitory GABAB receptors (GABABRs) can down-regulate most excitatory synapses in the CNS by reducing postsynaptic excitability. Functional GABABRs are heterodimers of GABAB1 and GABAB2 subunits and here we show that the trafficking and surface expression of GABABRs is differentially regulated by synaptic or pathophysiological activation of NMDA receptors (NMDARs). Activation of synaptic NMDARs using a chemLTP protocol increases GABABR recycling and surface expression. In contrast, excitotoxic global activation of synaptic and extrasynaptic NMDARs by bath application of NMDA causes the loss of surface GABABRs. Intriguingly, exposing neurons to extreme metabolic stress using oxygen/glucose deprivation (OGD) increases GABAB1 but decreases GABAB2 surface expression. The increase in surface GABAB1 involves enhanced recycling and is blocked by the NMDAR antagonist AP5. The decrease in surface GABAB2 is also blocked by AP5 and by inhibiting degradation pathways. These results indicate that NMDAR activity is critical in GABABR trafficking and function and that the individual subunits can be separately controlled to regulate neuronal responsiveness and survival.
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Affiliation(s)
- Sriharsha Kantamneni
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
| | | | - Jia Luo
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Helena Cimarosti
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Susan C Jacobs
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Nadia Jaafari
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M Henley
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
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Ballesteros-Merino C, Watanabe M, Shigemoto R, Fukazawa Y, Adelman JP, Luján R. Differential subcellular localization of SK3-containing channels in the hippocampus. Eur J Neurosci 2014; 39:883-892. [PMID: 24405447 DOI: 10.1111/ejn.12474] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/03/2013] [Accepted: 12/03/2013] [Indexed: 12/22/2022]
Abstract
Small-conductance, Ca(2+) -activated K(+) (SK) channels are expressed in the hippocampus where they regulate synaptic responses, plasticity, and learning and memory. To investigate the expression of SK3 (KCNN3) subunits, we determined the developmental profile and subcellular distribution of SK3 in the developing mouse hippocampus using western blots, immunohistochemistry and high-resolution immunoelectron microscopy. The results showed that SK3 expression increased during postnatal development, and that the localization of SK3 changed from being mainly associated with the endoplasmic reticulum and intracellular sites during the first postnatal week to being progressively concentrated in dendritic spines during later stages. In the adult, SK3 was localized mainly in postsynaptic compartments, both at extrasynaptic sites and along the postsynaptic density of excitatory synapses. Double labelling showed that SK3 co-localized with SK2 (KCNN2) and with N-methyl-D-aspartate receptors. Finally, quantitative analysis of SK3 density revealed two subcellular distribution patterns in different hippocampal layers, with SK3 being unevenly distributed in CA1 region of the hippocampus pyramidal cells and homogeneously distributed in dentate gyrus granule cells. Our results revealed a complex cell surface distribution of SK3-containing channels and a distinct developmental program that may influence different hippocampal functions.
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Affiliation(s)
- Carmen Ballesteros-Merino
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, Albacete, Spain
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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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Höftberger R, Titulaer MJ, Sabater L, Dome B, Rózsás A, Hegedus B, Hoda MA, Laszlo V, Ankersmit HJ, Harms L, Boyero S, de Felipe A, Saiz A, Dalmau J, Graus F. Encephalitis and GABAB receptor antibodies: novel findings in a new case series of 20 patients. Neurology 2013; 81:1500-6. [PMID: 24068784 DOI: 10.1212/wnl.0b013e3182a9585f] [Citation(s) in RCA: 302] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
OBJECTIVE To report the clinical features of 20 newly diagnosed patients with GABAB receptor (GABABR) antibodies and determine the frequency of associated tumors and concurrent neuronal autoantibodies. METHODS Clinical data were retrospectively obtained and evaluated. Serum and CSF samples were examined for additional antibodies using methods previously reported. RESULTS Seventeen patients presented with seizures, memory loss, and confusion, compatible with limbic encephalitis (LE), one patient presented with ataxia, one patient presented with status epilepticus, and one patient presented with opsoclonus-myoclonus syndrome (OMS). Nineteen (95%) patients eventually developed LE during the course of the disease. Small-cell lung cancer (SCLC) was identified in 10 (50%) patients, all with LE. Treatment and outcome was available from 19 patients: 15 showed complete (n = 7) or partial (n = 8) neurologic improvement after steroids, IV immunoglobulins, or plasma exchange and oncologic treatment when indicated; 1 patient died of tumor progression shortly after the first cycle of immunotherapy, and 3 were not treated. Five patients with SCLC had additional onconeuronal antibodies (Ri, amphiphysin, or SOX1), and 2 without tumor had GAD65 and NMDAR antibodies, respectively. GABABR antibodies were not detected in serum of 116 patients with SCLC without neurologic symptoms. CONCLUSION Our study confirms GABABR as an autoantigen of paraneoplastic and nonparaneoplastic LE and expands the phenotype of GABABR antibodies to ataxia, OMS, and status epilepticus. The long-term prognosis is dictated by the presence of a tumor. Recognition of syndromes associated with GABABR antibodies is important because they usually respond to treatment.
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Affiliation(s)
- Romana Höftberger
- From the Service of Neurology (R.H., M.T., L.S., A.S., F.G.), Hospital Clínic, Universitat de Barcelona and Institut d'Investigació Biomèdica August Pi i Sunyer (IDIBAPS), Barcelona, Spain; Institute of Neurology (R.H.), Medical University of Vienna, Austria; Department of Neurology (M.T.), Erasmus Medical Center, Rotterdam, the Netherlands; Department of Tumor Biology (B.D., A.R., B.H., M.A.H., V.L.), National Koranyi Institute of TB and Pulmonology, Budapest, Hungary; Department of Thoracic Surgery (B.D., A.R., B.H., M.A.H., V.L., H.J.A.), Medical University of Vienna, Austria; 2nd Department of Pathology (B.H.), Semmelweis University, Budapest, Hungary; Christian Doppler Laboratory for Cardiac and Thoracic Diagnosis and Regeneration (H.J.A.), Vienna, Austria; Department of Neurology (L.H.), Charité University Medicine Berlin, Germany; Servicio Neurología (S.B.), Hospital de Cruces, Barakaldo; Servicio Neurología (A.d.F.), Hospital Ramón y Cajal, Madrid; Institució Catalana de Recerca i Estudis Avançats (ICREA) (J.D.), IDIBAPS, Hospital Clínic, Barcelona, Spain; and Department of Neurology (J.D.), University of Pennsylvania, Philadelphia
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Ehrlich DE, Ryan SJ, Hazra R, Guo JD, Rainnie DG. Postnatal maturation of GABAergic transmission in the rat basolateral amygdala. J Neurophysiol 2013; 110:926-41. [PMID: 23719209 PMCID: PMC3742982 DOI: 10.1152/jn.01105.2012] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 05/28/2013] [Indexed: 12/12/2022] Open
Abstract
Many psychiatric disorders, including anxiety and autism spectrum disorders, have early ages of onset and high incidence in juveniles. To better treat and prevent these disorders, it is important to first understand normal development of brain circuits that process emotion. Healthy and maladaptive emotional processing involve the basolateral amygdala (BLA), dysfunction of which has been implicated in numerous psychiatric disorders. Normal function of the adult BLA relies on a fine balance of glutamatergic excitation and GABAergic inhibition. Elsewhere in the brain GABAergic transmission changes throughout development, but little is known about the maturation of GABAergic transmission in the BLA. Here we used whole cell patch-clamp recording and single-cell RT-PCR to study GABAergic transmission in rat BLA principal neurons at postnatal day (P)7, P14, P21, P28, and P35. GABAA currents exhibited a significant twofold reduction in rise time and nearly 25% reduction in decay time constant between P7 and P28. This corresponded with a shift in expression of GABAA receptor subunit mRNA from the α2- to the α1-subunit. The reversal potential for GABAA receptors transitioned from depolarizing to hyperpolarizing with age, from around -55 mV at P7 to -70 mV by P21. There was a corresponding shift in expression of opposing chloride pumps that influence the reversal, from NKCC1 to KCC2. Finally, we observed short-term depression of GABAA postsynaptic currents in immature neurons that was significantly and gradually abolished by P28. These findings reveal that in the developing BLA GABAergic transmission is highly dynamic, reaching maturity at the end of the first postnatal month.
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Affiliation(s)
- David E Ehrlich
- Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30329, USA
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Fajardo-Serrano A, Wydeven N, Young D, Watanabe M, Shigemoto R, Martemyanov KA, Wickman K, Luján R. Association of Rgs7/Gβ5 complexes with Girk channels and GABAB receptors in hippocampal CA1 pyramidal neurons. Hippocampus 2013; 23:1231-45. [PMID: 23804514 DOI: 10.1002/hipo.22161] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2013] [Indexed: 12/15/2022]
Abstract
In the hippocampus, signaling through G protein-coupled receptors is modulated by Regulators of G protein signaling (Rgs) proteins, which act to stimulate the rate of GTP hydrolysis, and consequently, G protein inactivation. The R7-Rgs subfamily selectively deactivates the G(i/o)-class of Gα subunits that mediate the action of several GPCRs. Here, we used co-immunoprecipitation, electrophysiology and immunoelectron microscopy techniques to investigate the formation of macromolecular complexes and spatial relationship of Rgs7/Gβ5 complexes and its prototypical signaling partners, the GABAB receptor and Girk channel. Co-expression of recombinant GABAB receptors and Girk channels in combination with co-immunoprecipitation experiments established that the Rgs7/Gβ5 forms complexes with GABAB receptors or Girk channels. Using electrophysiological experiments, we found that GABAB -Girk current deactivation kinetics was markedly faster in cells coexpressing Rgs7/Gβ5. At the electron microscopic level, immunolabeling for Rgs7 and Gβ5 proteins was found primarily in the dendritic layers of the hippocampus and showed similar distribution patterns. Immunoreactivity was mostly localized along the extrasynaptic plasma membrane of dendritic shafts and spines of pyramidal cells and, to a lesser extent, to that of presynaptic terminals. Quantitative analysis of immunogold particles for Rgs7 and Gβ5 revealed an enrichment of the two proteins around excitatory synapses on dendritic spines, virtually identical to that of Girk2 and GABAB1 . These data support the existence of macromolecular complexes composed of GABAB receptor-G protein-Rgs7-Girk channels in which Rgs7 and Gβ5 proteins may preferentialy modulate GABAB receptor signaling through the deactivation of Girk channels on dendritic spines. In contrast, Rgs7 and Girk2 were associated but mainly segregated from GABAB1 in dendritic shafts, where Rgs7/Gβ5 signaling complexes might modulate Girk-dependent signaling via a different metabotropic receptor(s).
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Affiliation(s)
- Ana Fajardo-Serrano
- Instituto de Investigación en Discapacidades Neurológicas (IDINE), Departamento de Ciencias Médicas, Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006, Albacete, Spain
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Martínez-Hernández J, Ballesteros-Merino C, Fernández-Alacid L, Nicolau JC, Aguado C, Luján R. Polarised localisation of the voltage-gated sodium channel Na(v)1.2 in cerebellar granule cells. THE CEREBELLUM 2013; 12:16-26. [PMID: 22528969 DOI: 10.1007/s12311-012-0387-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Voltage-gated sodium channels are responsible for action potential initiation and propagation in electrically excitable cells. In this study, we used biochemical, immunohistochemical and quantitative immunoelectron microscopy techniques to reveal the temporal and spatial expression of the Na(v)1.2 channel subunit in granule cells of cerebellum. Using histoblot, we detected Na(v)1.2 widely distributed in the adult brain, but prominently expressed in the cerebellum. During postnatal development, Na(v)1.2 mRNA and protein were detected low during the first and second postnatal week, increased to P15 and then continue to decrease until adult levels. At the light microscopic level, Na(v)1.2 immunoreactivity concentrated in the molecular layer of the cerebellar cortex. Using immunofluorescence, Na(v)1.2 colocalised with VGluT1, but not with VGluT2, demonstrating that the subunit was preferentially present in parallel fibre axons and axon terminals. At the electron microscopic level, Na(v)1.2 immunoparticles were exclusively detected at presynaptic sites in granule cell axons and axon terminals of granule cells, with occasional clustering in their axon initial segment. This was demonstrated using quantitative immunogold analysis. In the axon terminals, the distribution of Na(v)1.2 was relatively uniform along the extrasynaptic plasma membrane and never detected in the active zone. We could not find detectable levels of Na(v)1.2 at postsynaptic elements of granule cells or other cerebellar cell types. The present findings show a polarised distribution of Na(v)1.2 along the neuronal surface of granule cells and suggest its primary involvement in the transmission of information from granule cells to Purkinje cells.
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Affiliation(s)
- José Martínez-Hernández
- Department of Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha, Campus Biosanitario, C/Almansa 14, 02006, Albacete, Spain
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Aguado C, Fernández-Alacid L, Cabañero MJ, Yanagawa Y, Schilling K, Watanabe M, Fritschy JM, Luján R. Differential maturation of GIRK2-expressing neurons in the mouse cerebellum. J Chem Neuroanat 2013; 47:79-89. [DOI: 10.1016/j.jchemneu.2012.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 11/22/2012] [Accepted: 11/26/2012] [Indexed: 12/22/2022]
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Fujita E, Tanabe Y, Imhof BA, Momoi MY, Momoi T. A complex of synaptic adhesion molecule CADM1, a molecule related to autism spectrum disorder, with MUPP1 in the cerebellum. J Neurochem 2012; 123:886-94. [PMID: 22994563 DOI: 10.1111/jnc.12022] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 06/27/2012] [Accepted: 09/10/2012] [Indexed: 01/14/2023]
Abstract
Mutations in the synaptic adhesion protein CADM1 (RA175/SynCAM1) are associated with autism spectrum disorder (ASD), a neurodevelopmental disorder of uncertain molecular origin. Cadm1-knock out (KO) mice exhibit smaller cerebella with decreased number of synapse of Purkinje cells and some ASD-like symptoms, including impaired ultrasonic vocalization. In this study, we examined the alteration of the Cadm1 synaptic complex in the mouse cerebellum at post-natal stages. The C-terminal peptide of Cadm1 associated with Mupp1 at PSD-95/Dlg/ZO-1 (PDZ)(1-5), a scaffold protein containing 13 PDZ domains, which interacted with gamma-aminobutyric acid type B receptor (GABBR)2 at PDZ13, but not with PSD-95. The GABBR2 was detected in a set of proteins interacting with Cadm1 C-terminal. Cadm1 colocalized with Mupp1 and GABBR2 on the dendrites of Purkinje cells in the molecular layers of the developing cerebellum and on the dendrites of hippocampal neurons cultured in vitro. These observations suggest that the Cadm1 synaptic receptor complex, including Mupp1-GABBR2, is located on the dendrites of Purkinje cells. The amount of GABBR2 protein, but not mRNA, was increased in the cerebella of Cadm1 KO mice, suggesting that lack of Cadm1 does not affect transcription of GABBR2, but may stabilize the Mupp1-GABBR2 complex; the Mupp1-GABBR2 interaction may be stabilized by conformational change in Mupp1 or association with other adhesion molecules and by anchorage to the post-synaptic membrane. Up-regulation of GABBR2 in the cerebellum in the absence of CADM1 may be associated with ASD pathogenesis.
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Affiliation(s)
- Eriko Fujita
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
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Ferrándiz-Huertas C, Gil-Mínguez M, Luján R. Regional expression and subcellular localization of the voltage-gated calcium channel β subunits in the developing mouse brain. J Neurochem 2012; 122:1095-107. [PMID: 22737983 DOI: 10.1111/j.1471-4159.2012.07853.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Ca(2+) channel β subunits determine the maturation, biophysical properties and cell surface expression of high voltage-activated channels. Thus, we have analysed the expression, regional distribution and subcellular localization of the Ca(v) β subunit family in mice from birth to adulthood. In the hippocampus and cerebellum, Ca(v) β(1), Ca(v) β(3) and Ca(v) β(4) protein levels increased with age, although there were marked region- and developmental stage-specific differences in their expression. Ca(v) β(1) was predominantly expressed in the strata oriens and radiatum of the hippocampus, and only weakly in the cerebellum. The Ca(v) β(3) subunit was mainly expressed in the strata radiatum and lucidum of the hippocampus and in the molecular layer of the cerebellum. During development, Ca(v) β(3) protein expression in the cerebellum peaked at postnatal days (P) 15 and 21, and had diminished drastically by P60, and in the hippocampus increased with age throughout all subfields. Ca(v) β(4) protein was detected throughout the cerebellum, particularly in the molecular layer, and in contrast to the other subunits, Ca(v) β(4) was mainly detected in the molecular layer and the hilus of the hippocampus. At the subcellular level, Ca(v) β(1) and Ca(v) β(3) were predominantly located post-synaptically in hippocampal pyramidal cells and cerebellar Purkinje cells. Ca(v) β(4) subunits were detected in the pre-synaptic and post-synaptic compartments of both regions, albeit more strongly at post-synaptic sites. These results shed new light on the developmental regulation and subcellular localization of Ca(v) β subunits, and their possible role in pre- and post-synaptic transmission.
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Affiliation(s)
- Clotilde Ferrándiz-Huertas
- Dept. Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
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Benke D, Zemoura K, Maier PJ. Modulation of cell surface GABA(B) receptors by desensitization, trafficking and regulated degradation. World J Biol Chem 2012; 3:61-72. [PMID: 22558486 PMCID: PMC3342575 DOI: 10.4331/wjbc.v3.i4.61] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2011] [Revised: 12/08/2011] [Accepted: 12/15/2011] [Indexed: 02/05/2023] Open
Abstract
Inhibitory neurotransmission ensures normal brain function by counteracting and integrating excitatory activity. γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian central nervous system, and mediates its effects via two classes of receptors: the GABA(A) and GABA(B) receptors. GABA(A) receptors are heteropentameric GABA-gated chloride channels and responsible for fast inhibitory neurotransmission. GABA(B) receptors are heterodimeric G protein coupled receptors (GPCR) that mediate slow and prolonged inhibitory transmission. The extent of inhibitory neurotransmission is determined by a variety of factors, such as the degree of transmitter release and changes in receptor activity by posttranslational modifications (e.g., phosphorylation), as well as by the number of receptors present in the plasma membrane available for signal transduction. The level of GABA(B) receptors at the cell surface critically depends on the residence time at the cell surface and finally the rates of endocytosis and degradation. In this review we focus primarily on recent advances in the understanding of trafficking mechanisms that determine the expression level of GABA(B) receptors in the plasma membrane, and thereby signaling strength.
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Affiliation(s)
- Dietmar Benke
- Dietmar Benke, Khaled Zemoura, Patrick J Maier, Institute of Pharmacology and Toxicology, University of Zürich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
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Fernández-Alacid L, Watanabe M, Molnár E, Wickman K, Luján R. Developmental regulation of G protein-gated inwardly-rectifying K+ (GIRK/Kir3) channel subunits in the brain. Eur J Neurosci 2011; 34:1724-36. [PMID: 22098295 DOI: 10.1111/j.1460-9568.2011.07886.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
G protein-gated inwardly-rectifying K(+) (GIRK/family 3 of inwardly-rectifying K(+) ) channels are coupled to neurotransmitter action and can play important roles in modulating neuronal excitability. We investigated the temporal and spatial expression of GIRK1, GIRK2 and GIRK3 subunits in the developing and adult brain of mice and rats using biochemical, immunohistochemical and immunoelectron microscopic techniques. At all ages analysed, the overall distribution patterns of GIRK1-3 were very similar, with high expression levels in the neocortex, cerebellum, hippocampus and thalamus. Focusing on the hippocampus, histoblotting and immunohistochemistry showed that GIRK1-3 protein levels increased with age, and this was accompanied by a shift in the subcellular localization of the subunits. Early in development (postnatal day 5), GIRK subunits were predominantly localized to the endoplasmic reticulum in the pyramidal cells, but by postnatal day 60 they were mostly found along the plasma membrane. During development, GIRK1 and GIRK2 were found primarily at postsynaptic sites, whereas GIRK3 was predominantly detected at presynaptic sites. In addition, GIRK1 and GIRK2 expression on the spine plasma membrane showed identical proximal-to-distal gradients that differed from GIRK3 distribution. Furthermore, although GIRK1 was never found within the postsynaptic density (PSD), the level of GIRK2 in the PSD progressively increased and GIRK3 did not change in the PSD during development. Together, these findings shed new light on the developmental regulation and subcellular diversity of neuronal GIRK channels, and support the contention that distinct subpopulations of GIRK channels exert separable influences on neuronal excitability. The ability to selectively target specific subpopulations of GIRK channels may prove effective in the treatment of disorders of excitability.
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Affiliation(s)
- Laura Fernández-Alacid
- Departamento de Ciencias Médicas, Facultad de Medicina, Instituto de Investigación en Discapacidades Neurológicas (IDINE), Universidad de Castilla-La Mancha, Albacete, Spain
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Ballesteros-Merino C, Lin M, Wu WW, Ferrandiz-Huertas C, Cabañero MJ, Watanabe M, Fukazawa Y, Shigemoto R, Maylie J, Adelman JP, Luján R. Developmental profile of SK2 channel expression and function in CA1 neurons. Hippocampus 2011; 22:1467-80. [PMID: 22072564 DOI: 10.1002/hipo.20986] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/02/2011] [Indexed: 12/16/2022]
Abstract
We investigated the temporal and spatial expression of SK2 in the developing mouse hippocampus using molecular and biochemical techniques, quantitative immunogold electron microscopy, and electrophysiology. The mRNA encoding SK2 was expressed in the developing and adult hippocampus. Western blotting and immunohistochemistry showed that SK2 protein increased with age. This was accompanied by a shift in subcellular localization. Early in development (P5), SK2 was predominantly localized to the endoplasmic reticulum in the pyramidal cell layer. But by P30 SK2 was almost exclusively expressed in the dendrites and spines. The level of SK2 at the postsynaptic density (PSD) also increased during development. In the adult, SK2 expression on the spine plasma membrane showed a proximal-to-distal gradient. Consistent with this redistribution and gradient of SK2, the selective SK channel blocker apamin increased evoked excitatory postsynaptic potentials (EPSPs) only in CA1 pyramidal neurons from mice older than P15. However, the effect of apamin on EPSPs was not different between synapses in proximal or distal stratum radiatum or stratum lacunosum-moleculare in adult. These results show a developmental increase and gradient in SK2-containing channel surface expression that underlie their influence on neurotransmission, and that may contribute to increased memory acquisition during early development.
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Affiliation(s)
- Carmen Ballesteros-Merino
- Departamento de Ciencias Médicas, Instituto de Investigación en Discapacidades Neurológicas, Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain
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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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Revealing protein oligomerization and densities in situ using spatial intensity distribution analysis. Proc Natl Acad Sci U S A 2011; 108:7010-5. [PMID: 21482753 DOI: 10.1073/pnas.1018658108] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Measuring protein interactions is key to understanding cell signaling mechanisms, but quantitative analysis of these interactions in situ has remained a major challenge. Here, we present spatial intensity distribution analysis (SpIDA), an analysis technique for image data obtained using standard fluorescence microscopy. SpIDA directly measures fluorescent macromolecule densities and oligomerization states sampled within single images. The method is based on fitting intensity histograms calculated from images to obtain density maps of fluorescent molecules and their quantal brightness. Because spatial distributions are acquired by imaging, SpIDA can be applied to the analysis of images of chemically fixed tissue as well as live cells. However, the technique does not rely on spatial correlations, freeing it from biases caused by subcellular compartmentalization and heterogeneity within tissue samples. Analysis of computer-based simulations and immunocytochemically stained GABA(B) receptors in spinal cord samples shows that the approach yields accurate measurements over a broader range of densities than established procedures. SpIDA is applicable to sampling within small areas (6 μm(2)) and reveals the presence of monomers and dimers with single-dye labeling. Finally, using GFP-tagged receptor subunits, we show that SpIDA can resolve dynamic changes in receptor oligomerization in live cells. The advantages and greater versatility of SpIDA over current techniques open the door to quantificative studies of protein interactions in native tissue using standard fluorescence microscopy.
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Jamal L, Zhang H, Finlayson PG, Porter LA, Zhang H. The level and distribution of the GABA(B)R2 receptor subunit in the rat's central auditory system. Neuroscience 2011; 181:243-56. [PMID: 21371537 DOI: 10.1016/j.neuroscience.2011.02.050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 01/31/2011] [Accepted: 02/22/2011] [Indexed: 11/27/2022]
Abstract
The GABA(B) receptor is important for the function of auditory neurons. We used Western blotting and immunohistochemical methods to examine the level and localization of GABA(B)R2, a required subunit of a functional GABA(B) receptor, in the rat's central auditory system. Results revealed that this subunit was expressed throughout the auditory system with the level being high in the layers I-V of the auditory cortex, medial geniculate nucleus, dorsomedial and lateral parts of the inferior colliculus, and the molecular and fusiform cell layers of the dorsal cochlear nucleus. Labeled cell bodies were found in all the areas showing immunoreactivity. Neuropil labeling was strong in areas with high overall levels of immunoreactivity. Regional distributions of the receptor subunit revealed clear boundaries of some auditory subnuclei including the dorsal and ventral cochlear nuclei and the lateral superior olivary nucleus. Differences in immunoreactivity were found between the central nucleus and the dorsal cortex of the inferior colliculus and between the dorsal and ventral parts of the ventral nucleus of the lateral lemniscus, although no clear boundaries were observed. No differences in immunoreactivity were found between the core and the belt areas of the auditory cortex and among the subdivisions of the medial geniculate nucleus. The regional distribution of the receptor subunit in auditory structures is consistent with inputs to these structures and the cellular localization of the receptor in auditory neurons supports the contribution of the GABA(B) receptor to synaptic responses in these neurons.
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Affiliation(s)
- L Jamal
- Department of Biological Sciences, University of Windsor, Windsor, ON N9B 3P4, Canada
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Presynaptic HCN1 channels regulate Cav3.2 activity and neurotransmission at select cortical synapses. Nat Neurosci 2011; 14:478-86. [PMID: 21358644 PMCID: PMC3068302 DOI: 10.1038/nn.2757] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 01/13/2011] [Indexed: 11/09/2022]
Abstract
The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are subthreshold, voltage-gated ion channels that are highly expressed in hippocampal and cortical pyramidal cell dendrites, where they are important for regulating synaptic potential integration and plasticity. We found that HCN1 subunits are also localized to the active zone of mature asymmetric synaptic terminals targeting mouse entorhinal cortical layer III pyramidal neurons. HCN channels inhibited glutamate synaptic release by suppressing the activity of low-threshold voltage-gated T-type (Ca(V)3.2) Ca²(+) channels. Consistent with this, electron microscopy revealed colocalization of presynaptic HCN1 and Ca(V)3.2 subunit. This represents a previously unknown mechanism by which HCN channels regulate synaptic strength and thereby neural information processing and network excitability.
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Ciruela F, Fernández-Dueñas V, Sahlholm K, Fernández-Alacid L, Nicolau JC, Watanabe M, Luján R. Evidence for oligomerization between GABAB receptors and GIRK channels containing the GIRK1 and GIRK3 subunits. Eur J Neurosci 2010; 32:1265-77. [PMID: 20846323 DOI: 10.1111/j.1460-9568.2010.07356.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The stimulation of inhibitory neurotransmitter receptors, such as γ-aminobutyric acid type B (GABA(B) ) receptors, activates G protein-gated inwardly-rectifying K(+) (GIRK) channels, which influence membrane excitability. There is now evidence suggesting that G protein-coupled receptors and G protein-gated inwardly-rectifying K(+) [GIRK/family 3 of inwardly-rectifying K(+) (Kir3)] channels do not diffuse freely within the plasma membrane, but instead there are direct protein-protein interactions between them. Here, we used bioluminescence resonance energy transfer, co-immunoprecipitation, confocal and electron microscopy techniques to investigate the oligomerization of GABA(B) receptors with GIRK channels containing the GIRK3 subunit, whose contribution to functional channels is still unresolved. Co-expression of GABA(B) receptors and GIRK channels in human embryonic kidney-293 cells in combination with co-immunoprecipitation experiments established that the metabotropic receptor forms stable complexes with GIRK channels. Using bioluminescence resonance energy transfer, we have shown that, in living cells under physiological conditions, GABA(B) receptors interact directly with GIRK1/GIRK3 heterotetramers. In addition, we have provided evidence that the receptor-effector complexes are also found in vivo and identified that the cerebellar granule cells are one neuron population where the interaction probably takes place. Altogether, our data show that signalling complexes containing GABA(B) receptors and GIRK channels are formed shortly after biosynthesis, probably in the endoplasmic reticulum and/or endoplasmic reticulum/Golgi apparatus complex, suggesting that this might be a general feature of receptor-effector ion channel signal transduction and supporting a channel-forming role for the GIRK3 subunit.
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Affiliation(s)
- Francisco Ciruela
- Unitat de Farmacologia (4102), Departament Patologia i Terapèutica Experimental, Facultat de Medicina-Bellvitge, Universitat de IDIBELL-Universitat de Barcelona, L'Hospitalet de Llobregat, Barcelona, Spain.
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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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