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Yang X, Le Corronc H, Legendre P, Triller A, Specht CG. Differential regulation of glycinergic and GABAergic nanocolumns at mixed inhibitory synapses. EMBO Rep 2021; 22:e52154. [PMID: 34047007 PMCID: PMC8256292 DOI: 10.15252/embr.202052154] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 04/24/2021] [Accepted: 04/30/2021] [Indexed: 12/19/2022] Open
Abstract
Super‐resolution imaging has revealed that key synaptic proteins are dynamically organized within sub‐synaptic domains (SSDs). To examine how different inhibitory receptors are regulated, we carried out dual‐color direct stochastic optical reconstruction microscopy (dSTORM) of GlyRs and GABAARs at mixed inhibitory synapses in spinal cord neurons. We show that endogenous GlyRs and GABAARs as well as their common scaffold protein gephyrin form SSDs that align with pre‐synaptic RIM1/2, thus creating trans‐synaptic nanocolumns. Strikingly, GlyRs and GABAARs occupy different sub‐synaptic spaces, exhibiting only a partial overlap at mixed inhibitory synapses. When network activity is increased by 4‐aminopyridine treatment, the GABAAR copy numbers and the number of GABAAR SSDs are reduced, while GlyRs remain largely unchanged. This differential regulation is likely the result of changes in gephyrin phosphorylation that preferentially occurs outside of SSDs. The activity‐dependent regulation of GABAARs versus GlyRs suggests that different signaling pathways control the receptors' sub‐synaptic clustering. Taken together, our data reinforce the notion that the precise sub‐synaptic organization of GlyRs, GABAARs, and gephyrin has functional consequences for the plasticity of mixed inhibitory synapses.
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Affiliation(s)
- Xiaojuan Yang
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France.,School of Psychology and Cognitive Science, East China Normal University, Shanghai, China
| | - Hervé Le Corronc
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS, Inserm, UPMC, Sorbonne University, Paris, France
| | - Pascal Legendre
- Institute of Biology Paris Seine, Neuroscience Paris Seine, CNRS, Inserm, UPMC, Sorbonne University, Paris, France
| | - Antoine Triller
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France
| | - Christian G Specht
- Institute of Biology of the École Normale Supérieure (IBENS), CNRS, Inserm, PSL Research University, Paris, France.,Diseases and Hormones of the Nervous System (DHNS), Inserm, Université Paris-Saclay, Le Kremlin-Bicêtre, France
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2
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Yang X, Annaert W. The Nanoscopic Organization of Synapse Structures: A Common Basis for Cell Communication. MEMBRANES 2021; 11:248. [PMID: 33808285 PMCID: PMC8065904 DOI: 10.3390/membranes11040248] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/26/2021] [Accepted: 03/27/2021] [Indexed: 11/16/2022]
Abstract
Synapse structures, including neuronal and immunological synapses, can be seen as the plasma membrane contact sites between two individual cells where information is transmitted from one cell to the other. The distance between the two plasma membranes is only a few tens of nanometers, but these areas are densely populated with functionally different proteins, including adhesion proteins, receptors, and transporters. The narrow space between the two plasma membranes has been a barrier for resolving the synaptic architecture due to the diffraction limit in conventional microscopy (~250 nm). Various advanced super-resolution microscopy techniques, such as stimulated emission depletion (STED), structured illumination microscopy (SIM), and single-molecule localization microscopy (SMLM), bypass the diffraction limit and provide a sub-diffraction-limit resolving power, ranging from 10 to 100 nm. The studies using super-resolution microscopy have revealed unprecedented details of the nanoscopic organization and dynamics of synaptic molecules. In general, most synaptic proteins appear to be heterogeneously distributed and form nanodomains at the membranes. These nanodomains are dynamic functional units, playing important roles in mediating signal transmission through synapses. Herein, we discuss our current knowledge on the super-resolution nanoscopic architecture of synapses and their functional implications, with a particular focus on the neuronal synapses and immune synapses.
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Affiliation(s)
| | - Wim Annaert
- VIB Center for Brain and Disease Research and KU Leuven, Department of Neurosciences, Gasthuisberg, B-3000 Leuven, Belgium;
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3
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Tang ZQ, Lu YG, Huang YN, Chen L. Cross-talk pattern between GABA A- and glycine-receptors in CNS neurons is shaped by their relative expression levels. Brain Res 2020; 1748:147071. [PMID: 32827550 DOI: 10.1016/j.brainres.2020.147071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 08/03/2020] [Accepted: 08/17/2020] [Indexed: 11/17/2022]
Abstract
GABAA receptors (GABAARs) and glycine receptors (GlyRs) are two principal inhibitory chloride ion channels in the central nervous system. The two receptors do not function independently but cross-talk to each other, i.e., the activation of one receptor would inhibit the other. This cross-talk is present in different patterns across various regions in the central nervous system; however, the factor that determines these patterns is not understood. Here, we show that the pattern of cross-talk between the two receptors is shaped by their relative expression level in a neuron: a higher expression level correlates with louder talk. In line with a tendency of decrease in expression level of GlyRs and increase in expression level of GABAARs from the spinal cord, the brainstem to the neocortex, GlyRs talked much louder (i.e. produced greater inhibition) than GABAARs (one-way pattern) in spinal cord neurons, about equally loud as GABAARs (symmetric pattern) in inferior colliculus neurons and less loud (i.e. less inhibition) than GABAARs (asymmetric pattern) in auditory cortex neurons. Overexpression of GlyRs in inferior colliculus neurons produced an asymmetric pattern that should otherwise have been observed in spinal cord neurons. These expression level-dependent patterns of cross-talk between the two receptors may suggest how the central nervous system uses an alternative mechanism to maintain a delicate level of inhibition through adjusting the proportion of the two receptors in a neuron along its pathway.
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Affiliation(s)
- Zheng-Quan Tang
- School of Life Sciences, Anhui University, Hefei 230601, China; Key Laboratory of Human Microenvironment and Precision Medicine of Anhui Higher Education Institutes, Anhui University, Hefei 230601, China.
| | - Yun-Gang Lu
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; Auditory Research Laboratory, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Yi-Na Huang
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; Auditory Research Laboratory, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Lin Chen
- CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China; Auditory Research Laboratory, School of Life Sciences, University of Science and Technology of China, Hefei 230027, China.
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4
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Hirrlinger J, Marx G, Besser S, Sicker M, Köhler S, Hirrlinger PG, Wojcik SM, Eulenburg V, Winkler U, Hülsmann S. GABA-Glycine Cotransmitting Neurons in the Ventrolateral Medulla: Development and Functional Relevance for Breathing. Front Cell Neurosci 2019; 13:517. [PMID: 31803026 PMCID: PMC6877658 DOI: 10.3389/fncel.2019.00517] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 11/04/2019] [Indexed: 11/13/2022] Open
Abstract
Inhibitory neurons crucially contribute to shaping the breathing rhythm in the brain stem. These neurons use GABA or glycine as neurotransmitter; or co-release GABA and glycine. However, the developmental relationship between GABAergic, glycinergic and cotransmitting neurons, and the functional relevance of cotransmitting neurons has remained enigmatic. Transgenic mice expressing fluorescent markers or the split-Cre system in inhibitory neurons were developed to track the three different interneuron phenotypes. During late embryonic development, the majority of inhibitory neurons in the ventrolateral medulla are cotransmitting cells, most of which differentiate into GABAergic and glycinergic neurons around birth and around postnatal day 4, respectively. Functional inactivation of cotransmitting neurons revealed an increase of the number of respiratory pauses, the cycle-by-cycle variability, and the overall variability of breathing. In summary, the majority of cotransmitting neurons differentiate into GABAergic or glycinergic neurons within the first 2 weeks after birth and these neurons contribute to fine-tuning of the breathing pattern.
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Affiliation(s)
- Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany.,Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Grit Marx
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Stefanie Besser
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Marit Sicker
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Susanne Köhler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Petra G Hirrlinger
- Medizinisch-Experimentelles Zentrum, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Volker Eulenburg
- Department for Anesthesiology and Intensive Care Therapy, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Ulrike Winkler
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Leipzig, Germany
| | - Swen Hülsmann
- Department of Anaesthesiology, University Medical Center, Georg-August University, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, Göttingen, Germany
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5
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Yoshida A, Moritani M, Nagase Y, Bae YC. Projection and synaptic connectivity of trigeminal mesencephalic nucleus neurons controlling jaw reflexes. J Oral Sci 2018. [PMID: 28637975 DOI: 10.2334/josnusd.16-0845] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Neurons in the trigeminal mesencephalic nucleus (Vmes) receive deep sensation (proprioception) from jaw-closing muscle spindles and periodontal ligaments and project primarily to the jaw-closing motoneuron pool (jaw-closing nucleus) of the trigeminal motor nucleus and to the supratrigeminal nucleus. Numerous articles have described the morphology and physiology of the central projections of Vmes afferents originating from the muscle spindles and periodontal ligaments. However, no report has provided a detailed description of projection and synaptic connectivity, especially of single afferents, and their functional implications. In this review, we reanalyze data obtained by single intra-axonal recording and labeling of functionally identified Vmes muscle spindle afferents and periodontal ligament afferents and by electron microscopic observation of their projection features and synaptic organization of boutons, to compare the data for the jaw-closing nucleus and supratrigeminal nucleus. Our analysis shows that each Vmes afferent type has characteristic projection pattern and synaptic feature that may be important in jaw-reflex control.
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Affiliation(s)
- Atsushi Yoshida
- Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University
| | - Masayuki Moritani
- Department of Physical Therapy, Faculty of Health Science, Morinomiya University of Medical Sciences
| | - Yoshitaka Nagase
- Department of Acupuncture, Takarazuka University of Medical and Health Care
| | - Yong Chul Bae
- Department of Anatomy, School of Dentistry, Kyungpook National University
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6
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Nerlich J, Rübsamen R, Milenkovic I. Developmental Shift of Inhibitory Transmitter Content at a Central Auditory Synapse. Front Cell Neurosci 2017; 11:211. [PMID: 28769768 PMCID: PMC5516124 DOI: 10.3389/fncel.2017.00211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 07/03/2017] [Indexed: 12/11/2022] Open
Abstract
Synaptic inhibition in the CNS is mostly mediated by GABA or glycine. Generally, the use of the two transmitters is spatially segregated, but there are central synapses employing both, which allows for spatial and temporal variability of inhibitory mechanisms. Spherical bushy cells (SBCs) in the mammalian cochlear nucleus receive primary excitatory inputs through auditory nerve fibers arising from the organ of Corti and non-primary inhibition mediated by a dual glycine-GABA transmission. Slow kinetics IPSCs enable activity dependent tonic-like conductance build up, functioning as a gain control by filtering out small or temporally imprecise EPSPs. However, it remained elusive whether GABA and glycine are released as content of the same vesicle or from distinct presynaptic terminals. The developmental profile of quantal release was investigated with whole cell recordings of miniature inhibitory postsynaptic currents (mIPSCs) from P1–P25 SBCs of Mongolian gerbils. GABA is the initial transmitter eliciting slow-rising and -decaying events of relatively small amplitudes, occurring only during early postnatal life. Around and after hearing onset, the inhibitory quanta are predominantly containing glycine that—with maturity—triggers progressively larger and longer mIPSC. In addition, GABA corelease with glycine evokes mIPSCs of particularly large amplitudes consistently occurring across all ages, but with low probability. Together, these results suggest that GABA, as the primary transmitter released from immature inhibitory terminals, initially plays a developmental role. In maturity, GABA is contained in synaptic vesicles only in addition to glycine to increase the inhibitory potency, thereby fulfilling solely a modulatory function.
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Affiliation(s)
- Jana Nerlich
- Department of Physiology, Faculty of Medicine, Carl Ludwig Institute for Physiology, University of LeipzigLeipzig, Germany
| | - Rudolf Rübsamen
- Faculty of Biosciences, Pharmacy and Psychology, University of LeipzigLeipzig, Germany
| | - Ivan Milenkovic
- Department of Physiology, Faculty of Medicine, Carl Ludwig Institute for Physiology, University of LeipzigLeipzig, Germany
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7
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Lamotte d'Incamps B, Bhumbra GS, Foster JD, Beato M, Ascher P. Segregation of glutamatergic and cholinergic transmission at the mixed motoneuron Renshaw cell synapse. Sci Rep 2017. [PMID: 28642492 PMCID: PMC5481398 DOI: 10.1038/s41598-017-04266-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In neonatal mice motoneurons excite Renshaw cells by releasing both acetylcholine (ACh) and glutamate. These two neurotransmitters activate two types of nicotinic receptors (nAChRs) (the homomeric α7 receptors and the heteromeric α*ß* receptors) as well as the two types of glutamate receptors (GluRs) (AMPARs and NMDARs). Using paired recordings, we confirm that a single motoneuron can release both transmitters on a single post-synaptic Renshaw cell. We then show that co-transmission is preserved in adult animals. Kinetic analysis of miniature EPSCs revealed quantal release of mixed events associating AMPARs and NMDARs, as well as α7 and α*ß* nAChRs, but no evidence was found for mEPSCs associating nAChRs with GluRs. Bayesian Quantal Analysis (BQA) of evoked EPSCs showed that the number of functional contacts on a single Renshaw cell is more than halved when the nicotinic receptors are blocked, confirming that the two neurotransmitters systems are segregated. Our observations can be explained if ACh and glutamate are released from common vesicles onto spatially segregated post-synaptic receptors clusters, but a pre-synaptic segregation of cholinergic and glutamatergic release sites is also possible.
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Affiliation(s)
- Boris Lamotte d'Incamps
- Center for Neurophysics, Physiology and Pathologies, CNRS UMR 8119, Université Paris Descartes, Paris, France.
| | - Gardave S Bhumbra
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Joshua D Foster
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Marco Beato
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London, United Kingdom
| | - Philippe Ascher
- Physiologie cérébrale, CNRS UMR 8118, Université Paris Descartes, Paris, France
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8
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Aubrey KR. Presynaptic control of inhibitory neurotransmitter content in VIAAT containing synaptic vesicles. Neurochem Int 2016; 98:94-102. [PMID: 27296116 DOI: 10.1016/j.neuint.2016.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 05/21/2016] [Accepted: 06/07/2016] [Indexed: 12/13/2022]
Abstract
In mammals, fast inhibitory neurotransmission is carried out by two amino acid transmitters, γ-aminobutyric acid (GABA) and glycine. The higher brain uses only GABA, but in the spinal cord and brain stem both GABA and glycine act as inhibitory signals. In some cases GABA and glycine are co-released from the same neuron where they are co-packaged into synaptic vesicles by a shared vesicular inhibitory amino acid transporter, VIAAT (also called vGAT). The vesicular content of all other classical neurotransmitters (eg. glutamate, monoamines, acetylcholine) is determined by the presence of a specialized vesicular transporter. Because VIAAT is non-specific, the phenotype of inhibitory synaptic vesicles is instead predicted to be dependent on the relative concentration of GABA and glycine in the cytosol of the presynaptic terminal. This predicts that changes in GABA or glycine supply should be reflected in vesicle transmitter content but as yet, the mechanisms that control GABA versus glycine uptake into synaptic vesicles and their potential for modulation are not clearly understood. This review summarizes the most relevant experimental data that examines the link between GABA and glycine accumulation in the presynaptic cytosol and the inhibitory vesicle phenotype. The accumulated evidence challenges the hypothesis that vesicular phenotype is determined simply by the competition of inhibitory transmitter for VIAAT and instead suggest that the GABA/glycine balance in vesicles is dynamically regulated.
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Affiliation(s)
- Karin R Aubrey
- Pain Management Research Institute, Kolling Institute of Medical Research & Northern Clinical School, University of Sydney at Royal North Shore Hospital, Pacific Hwy, St Leonards, NSW, 2065, Australia.
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9
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Dynamic fidelity control to the central auditory system: synergistic glycine/GABAergic inhibition in the cochlear nucleus. J Neurosci 2014; 34:11604-20. [PMID: 25164657 DOI: 10.1523/jneurosci.0719-14.2014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
GABA and glycine are the major inhibitory transmitters that attune neuronal activity in the CNS of mammals. The respective transmitters are mostly spatially separated, that is, synaptic inhibition in the forebrain areas is mediated by GABA, whereas glycine is predominantly used in the brainstem. Accordingly, inhibition in auditory brainstem circuits is largely mediated by glycine, but there are few auditory synapses using both transmitters in maturity. Little is known about physiological advantages of such a two-transmitter inhibitory mechanism. We explored the benefit of engaging both glycine and GABA with inhibition at the endbulb of Held-spherical bushy cell synapse in the auditory brainstem of juvenile Mongolian gerbils. This model synapse enables selective in vivo activation of excitatory and inhibitory neuronal inputs through systemic sound stimulation and precise analysis of the input (endbulb of Held) output (spherical bushy cell) function. The combination of in vivo and slice electrophysiology revealed that the dynamic AP inhibition in spherical bushy cells closely matches the inhibitory conductance profile determined by the glycine-R and GABAA-R. The slow and potent glycinergic component dominates the inhibitory conductance, thereby primarily accounting for its high-pass filter properties. GABAergic transmission enhances the inhibitory strength and shapes its duration in an activity-dependent manner, thus increasing the inhibitory potency to suppress the excitation through the endbulb of Held. Finally, in silico modeling provides a strong link between in vivo and slice data by simulating the interactions between the endbulb- and the synergistic glycine-GABA-conductances during in vivo-like spontaneous and sound evoked activities.
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10
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Sun H, Lu L, Zuo Y, Wang Y, Jiao Y, Zeng WZ, Huang C, Zhu MX, Zamponi GW, Zhou T, Xu TL, Cheng J, Li Y. Kainate receptor activation induces glycine receptor endocytosis through PKC deSUMOylation. Nat Commun 2014; 5:4980. [PMID: 25236484 PMCID: PMC4199113 DOI: 10.1038/ncomms5980] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 08/13/2014] [Indexed: 01/21/2023] Open
Abstract
Surface expression and regulated endocytosis of glycine receptors (GlyRs) play a critical function in balancing neuronal excitability. SUMOylation (SUMO modification) is of critical importance for maintaining neuronal function in the central nervous system. Here we show that activation of kainate receptors (KARs) causes GlyR endocytosis in a calcium- and protein kinase C (PKC)-dependent manner, leading to reduced GlyR-mediated synaptic activity in cultured spinal cord neurons and the superficial dorsal horn of rat spinal cord slices. This effect requires SUMO1/sentrin-specific peptidase 1 (SENP1)-mediated deSUMOylation of PKC, indicating that the crosstalk between KARs and GlyRs relies on the SUMOylation status of PKC. SENP1-mediated deSUMOylation of PKC is involved in the kainate-induced GlyR endocytosis and thus plays an important role in the anti-homeostatic regulation between excitatory and inhibitory ligand-gated ion channels. Altogether, we have identified a SUMOylation-dependent regulatory pathway for GlyR endocytosis, which may have important physiological implications for proper neuronal excitability. Maintenance of proper membrane excitability is vital to neuronal function and in several neuronal types this relies on a balance between receptor-mediated excitation and inhibition. Here the authors report a crosstalk between excitatory kainate receptors and inhibitory glycine receptors that relies on the SUMOylation status of PKC.
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Affiliation(s)
- Hao Sun
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Li Lu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yong Zuo
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yan Wang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yingfu Jiao
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Wei-Zheng Zeng
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Chao Huang
- Center for Translational Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, The University of Calgary, Calgary T2N 4 N1, Alberta, Canada
| | - Tong Zhou
- Department of Medicine, The University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
| | - Tian-Le Xu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Jinke Cheng
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yong Li
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
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11
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Linsalata AE, Chen X, Winters CA, Reese TS. Electron tomography on γ-aminobutyric acid-ergic synapses reveals a discontinuous postsynaptic network of filaments. J Comp Neurol 2014; 522:921-36. [PMID: 23982982 DOI: 10.1002/cne.23453] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 08/05/2013] [Accepted: 08/13/2013] [Indexed: 12/16/2022]
Abstract
The regulation of synaptic strength at γ-aminobutyric acid (GABA)-ergic synapses is dependent on the dynamic capture, retention, and modulation of GABA A-type receptors by cytoplasmic proteins at GABAergic postsynaptic sites. How these proteins are oriented and organized in the postsynaptic cytoplasm is not yet established. To better understand these structures and gain further insight into the mechanisms by which they regulate receptor populations at postsynaptic sites, we utilized electron tomography to examine GABAergic synapses in dissociated rat hippocampal cultures. GABAergic synapses were identified and selected for tomography by using a set of criteria derived from the structure of immunogold-labeled GABAergic synapses. Tomography revealed a complex postsynaptic network composed of filaments that extend ∼ 100 nm into the cytoplasm from the postsynaptic membrane. The distribution of these postsynaptic filaments was strikingly similar to that of the immunogold label for gephyrin. Filaments were interconnected through uniform patterns of contact, forming complexes composed of 2-12 filaments each. Complexes did not link to form an integrated, continuous scaffold, suggesting that GABAergic postsynaptic specializations are less rigidly organized than glutamatergic postsynaptic densities.
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Affiliation(s)
- Alexander E Linsalata
- Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, 20892
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12
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Abstract
The neurotransmitters GABA and glycine mediate fast synaptic inhibition by activating ligand-gated chloride channels--namely, type A GABA (GABA(A)) and glycine receptors. Both types of receptors are anchored postsynaptically by gephyrin, which self-assembles into a scaffold and interacts with the cytoskeleton. Current research indicates that postsynaptic gephyrin clusters are dynamic assemblies that are held together and regulated by multiple protein-protein interactions. Moreover, post-translational modifications of gephyrin regulate the formation and plasticity of GABAergic synapses by altering the clustering properties of postsynaptic scaffolds and thereby the availability and function of receptors and other signalling molecules. Here, we discuss the formation and regulation of the gephyrin scaffold, its role in GABAergic and glycinergic synaptic function and the implications for the pathophysiology of brain disorders caused by abnormal inhibitory neurotransmission.
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13
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Becchetti A. Neuronal nicotinic receptors in sleep-related epilepsy: studies in integrative biology. ISRN BIOCHEMISTRY 2012; 2012:262941. [PMID: 25969754 PMCID: PMC4392997 DOI: 10.5402/2012/262941] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 10/21/2012] [Indexed: 11/23/2022]
Abstract
Although Mendelian diseases are rare, when considered one by one, overall they constitute a significant social burden. Besides the medical aspects, they propose us one of the most general biological problems. Given the simplest physiological perturbation of an organism, that is, a single gene mutation, how do its effects percolate through the hierarchical biological levels to determine the pathogenesis? And how robust is the physiological system to this perturbation? To solve these problems, the study of genetic epilepsies caused by mutant ion channels presents special advantages, as it can exploit the full range of modern experimental methods. These allow to extend the functional analysis from single channels to whole brains. An instructive example is autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE), which can be caused by mutations in neuronal nicotinic acetylcholine receptors. In vitro, such mutations often produce hyperfunctional receptors, at least in heterozygous condition. However, understanding how this leads to sleep-related frontal epilepsy is all but straightforward. Several available animal models are helping us to determine the effects of ADNFLE mutations on the mammalian brain. Because of the complexity of the cholinergic regulation in both developing and mature brains, several pathogenic mechanisms are possible, which also present different therapeutic implications.
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Affiliation(s)
- Andrea Becchetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy
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14
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Inhibitory inputs to four types of spinocerebellar tract neurons in the cat spinal cord. Neuroscience 2012; 226:253-69. [PMID: 22989920 DOI: 10.1016/j.neuroscience.2012.09.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 09/05/2012] [Accepted: 09/06/2012] [Indexed: 11/24/2022]
Abstract
Spinocerebellar tract neurons are inhibited by various sources of input via pathways activated by descending tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with ventral spinocerebellar tract (VSCT) and dorsal spinocerebellar tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of spinocerebellar tract neurons to the cerebellum.
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Shrivastava AN, Triller A, Sieghart W. GABA(A) Receptors: Post-Synaptic Co-Localization and Cross-Talk with Other Receptors. Front Cell Neurosci 2011; 5:7. [PMID: 21734865 PMCID: PMC3123775 DOI: 10.3389/fncel.2011.00007] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 06/06/2011] [Indexed: 11/14/2022] Open
Abstract
γ-Aminobutyric acid type A receptors (GABAARs) are the major inhibitory neurotransmitter receptors in the central nervous system, and importantly contribute to the functional regulation of the nervous system. Several studies in the last few decades have convincingly shown that GABA can be co-localized with other neurotransmitters in the same synapse, and can be co-released with these neurotransmitters either from the same vesicles or from different vesicle pools. The co-released transmitters may act on post-synaptically co-localized receptors resulting in a simultaneous activation of both receptors. Most of the studies investigating such co-activation observed a reduced efficacy of GABA for activating GABAARs and thus, a reduced inhibition of the post-synaptic neuron. Similarly, in several cases activation of GABAARs has been reported to suppress the response of the associated receptors. Such a receptor cross-talk is either mediated via a direct coupling between the two receptors or via the activation of intracellular signaling pathways and is used for fine tuning of inhibition in the nervous system. Recently, it was demonstrated that a direct interaction of different receptors might already occur in intracellular compartments and might also be used to specifically target the receptors to the cell membrane. In this article, we provide an overview on such cross-talks between GABAARs and several other neurotransmitter receptors and briefly discuss their possible physiological and clinical importance.
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Affiliation(s)
- Amulya Nidhi Shrivastava
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University of Vienna Vienna, Austria
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Glycine receptor channels in spinal motoneurons are abnormal in a transgenic mouse model of amyotrophic lateral sclerosis. J Neurosci 2011; 31:2815-27. [PMID: 21414903 DOI: 10.1523/jneurosci.2475-10.2011] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a rapidly evolving and fatal adult-onset neurological disease characterized by progressive degeneration of motoneurons. Our previous study showed that glycinergic innervation of spinal motoneurons is deficient in an ALS mouse model expressing a mutant form of human superoxide dismutase-1 with a Gly93→Ala substitution (G93A-SOD1). In this study, we have examined, using whole-cell patch-clamp recordings, glycine receptor (GlyR)-mediated currents in spinal motoneurons from these transgenic mice. We developed a dissociated spinal cord culture model using embryonic transgenic mice expressing enhanced green fluorescent protein (eGFP) driven by the Hb9 promoter. Motoneurons were identified as Hb9-eGFP-expressing (Hb9-eGFP(+)) neurons with a characteristic morphology. To examine GlyRs in ALS motoneurons, we bred G93A-SOD1 mice to Hb9-eGFP mice and compared glycine-evoked currents in cultured Hb9-eGFP(+) motoneurons prepared from G93A-SOD1 embryos and from their nontransgenic littermates. Glycine-evoked current density was significantly smaller in the G93A-SOD1 motoneurons compared with control. Furthermore, the averaged current densities of spontaneous glycinergic miniature IPSCs (mIPSCs) were significantly smaller in the G93A-SOD1 motoneurons than in control motoneurons. No significant differences in GABA-induced currents and GABAergic mIPSCs were observed between G93A-SOD1 and control motoneurons. Quantitative single-cell reverse transcription-PCR found lower GlyRα1 subunit mRNA expression in G93A-SOD1 motoneurons, indicating that the reduction of GlyR current may result from the downregulation of GlyR mRNA expression in motoneurons. Immunocytochemistry demonstrated a decrease of surface postsynaptic GlyR on G93A-SOD1 motoneurons. Our study suggests that selective alterations in GlyR function contribute to inhibitory insufficiency in motoneurons early in the disease process of ALS.
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Waldvogel HJ, Baer K, Eady E, Allen KL, Gilbert RT, Mohler H, Rees MI, Nicholson LFB, Faull RLM. Differential localization of gamma-aminobutyric acid type A and glycine receptor subunits and gephyrin in the human pons, medulla oblongata and uppermost cervical segment of the spinal cord: an immunohistochemical study. J Comp Neurol 2010; 518:305-28. [PMID: 19950251 DOI: 10.1002/cne.22212] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Gephyrin is a multifunctional protein responsible for the clustering of glycine receptors (GlyR) and gamma-aminobutyric acid type A receptors (GABA(A)R). GlyR and GABA(A)R are heteropentameric chloride ion channels that facilitate fast-response, inhibitory neurotransmission in the mammalian brain and spinal cord. We investigated the immunohistochemical distribution of gephyrin and the major GABA(A)R and GlyR subunits in the human light microscopically in the rostral and caudal one-thirds of the pons, in the middle and caudal one-thirds of the medulla oblongata, and in the first cervical segment of the spinal cord. The results demonstrate a widespread pattern of immunoreactivity for GlyR and GABA(A)R subunits throughout these regions, including the spinal trigeminal nucleus, abducens nucleus, facial nucleus, pontine reticular formation, dorsal motor nucleus of the vagus nerve, hypoglossal nucleus, lateral cuneate nucleus, and nucleus of the solitary tract. The GABA(A)R alpha(1) and GlyR alpha(1) and beta subunits show high levels of immunoreactivity in these nuclei. The GABA(A)R subunits alpha(2), alpha(3), beta(2,3), and gamma(2) present weaker levels of immunoreactivity. Exceptions are intense levels of GABA(A)R alpha(2) subunit immunoreactivity in the inferior olivary complex and high levels of GABA(A)R alpha(3) subunit immunoreactivity in the locus coeruleus and raphe nuclei. Gephyrin immunoreactivity is highest in the first segment of the cervical spinal cord and hypoglossal nucleus. Our results suggest that a variety of different inhibitory receptor subtypes is responsible for inhibitory functions in the human brainstem and cervical spinal cord and that gephyrin functions as a clustering molecule for major subtypes of these inhibitory neurotransmitter receptors.
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Affiliation(s)
- H J Waldvogel
- Department of Anatomy with Radiology, Faculty of Medical and Health Science, University of Auckland, Auckland, New Zealand.
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Racca C, Gardiol A, Eom T, Ule J, Triller A, Darnell RB. The Neuronal Splicing Factor Nova Co-Localizes with Target RNAs in the Dendrite. Front Neural Circuits 2010; 4:5. [PMID: 20407637 PMCID: PMC2856630 DOI: 10.3389/neuro.04.005.2010] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Accepted: 02/01/2010] [Indexed: 01/10/2023] Open
Abstract
Nova proteins are neuron-specific RNA binding proteins targeted by autoantibodies in a disorder manifest by failure of motor inhibition, and they regulate splicing and alternative 3' processing. Nova regulates splicing of RNAs encoding synaptic proteins, including the inhibitory glycine receptor alpha2 subunit (GlyRalpha2), and binds to others, including the GIRK2 channel. We found that Nova harbors functional NES and NLS elements, shuttles between the nucleus and cytoplasm, and that 50% of the protein localizes to the soma-dendritic compartment. Immunofluoresence and EM analysis of spinal cord motor neurons demonstrated that Nova co-localizes beneath synaptic contacts in dendrites with the same RNA, GlyRalpha2, whose splicing it regulates in the nucleus. HITS-CLIP identified intronic and 3' UTR sites where Nova binds to GlyRalpha2 and GIRK2 transcripts in the brain. This led directly to the identification of a 3' UTR localization element that mediates Nova-dependent localization of GIRK2 in primary neurons. These data demonstrate that HITS-CLIP can identify functional RNA localization elements, and they suggest new links between the regulation of nuclear RNA processing and mRNA localization.
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Affiliation(s)
- Claudia Racca
- Biologie Cellulaire de la Synapse Normale et Pathologique, Institut National de la Santé et de la Recherche Médicale, Ecole Normale SupérieureParis, France
- Institute of Neuroscience, Newcastle UniversityNewcastle upon Tyne, UK
| | - Alejandra Gardiol
- Biologie Cellulaire de la Synapse Normale et Pathologique, Institut National de la Santé et de la Recherche Médicale, Ecole Normale SupérieureParis, France
- The Wellcome Trust CR UK Gurdon Institute, University of CambridgeCambridge, UK
| | - Taesun Eom
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller UniversityNew York, NY, USA
| | - Jernej Ule
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller UniversityNew York, NY, USA
- Medical Research Council Laboratory of Molecular BiologyCambridge, UK
| | - Antoine Triller
- Biologie Cellulaire de la Synapse Normale et Pathologique, Institut National de la Santé et de la Recherche Médicale, Ecole Normale SupérieureParis, France
| | - Robert B. Darnell
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller UniversityNew York, NY, USA
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Dumoulin A, Triller A, Kneussel M. Cellular transport and membrane dynamics of the glycine receptor. Front Mol Neurosci 2010; 2:28. [PMID: 20161805 PMCID: PMC2820378 DOI: 10.3389/neuro.02.028.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2009] [Accepted: 11/19/2009] [Indexed: 01/04/2023] Open
Abstract
Regulation of synaptic transmission is essential to tune individual-to-network neuronal activity. One way to modulate synaptic strength is to regulate neurotransmitter receptor numbers at postsynaptic sites. This can be achieved either through plasma membrane insertion of receptors derived from intracellular vesicle pools, a process depending on active cytoskeleton transport, or through surface membrane removal via endocytosis. In parallel, lateral diffusion events along the plasma membrane allow the exchange of receptor molecules between synaptic and extrasynaptic compartments, contributing to synaptic strength regulation. In recent years, results obtained from several groups studying glycine receptor (GlyR) trafficking and dynamics shed light on the regulation of synaptic GlyR density. Here, we review (i) proteins and mechanisms involved in GlyR cytoskeletal transport, (ii) the diffusion dynamics of GlyR and of its scaffolding protein gephyrin that control receptor numbers, and its relationship with synaptic plasticity, and (iii) adaptative changes in GlyR diffusion in response to global activity modifications, as a homeostatic mechanism.
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Affiliation(s)
- Andrea Dumoulin
- Biologie Cellulaire de la Synapse, Ecole Normale Superieure Paris, France
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20
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21
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Baer K, Waldvogel HJ, Faull RLM, Rees MI. Localization of glycine receptors in the human forebrain, brainstem, and cervical spinal cord: an immunohistochemical review. Front Mol Neurosci 2009; 2:25. [PMID: 19915682 PMCID: PMC2776491 DOI: 10.3389/neuro.02.025.2009] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 10/15/2009] [Indexed: 11/26/2022] Open
Abstract
Inhibitory neurotransmitter receptors for glycine (GlyR) are heteropentameric chloride ion channels that are comprised of four functional subunits, alpha1–3 and beta and that facilitate fast-response, inhibitory neurotransmission in the mammalian brain and spinal cord. We have investigated the distribution of GlyRs in the human forebrain, brainstem, and cervical spinal cord using immunohistochemistry at light and confocal laser scanning microscopy levels. This review will summarize the present knowledge on the GlyR distribution in the human brain using our established immunohistochemical techniques. The results of our immunohistochemical labeling studies demonstrated GlyR immunoreactivity (IR) throughout the human basal ganglia, substantia nigra, various pontine regions, rostral medulla oblongata and the cervical spinal cord present an intense and abundant punctate IR along the membranes of the neuronal soma and dendrites. This work is part of a systematic study of inhibitory neurotransmitter receptor distribution in the human CNS, and provides a basis for additional detailed physiological and pharmacological studies on the inter-relationship of GlyR, GABAAR and gephyrin in the human brain. This basic mapping exercise, we believe, will provide important baselines for the testing of future pharmacotherapies and drug regimes that modulate neuroinhibitory systems. These findings provide new information for understanding the complexity of glycinergic functions in the human brain, which will translate into the contribution of inhibitory mechanisms in paroxysmal disorders and neurodegenerative diseases such as Epilepsy, Huntington's and Parkinson's Disease and Motor Neuron Disease.
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Affiliation(s)
- Kristin Baer
- Molecular Neuroscience, Institute of Life Science, School of Medicine, Swansea University Swansea, UK
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22
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Kalinina NI, Kurchavyi GG, Amakhin DV, Veselkin NP. Differences in the activation of inhibitory motoneuron receptors in the frog Rana ridibunda by GABA and glycine and their interaction. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2009; 39:775-83. [PMID: 19779830 DOI: 10.1007/s11055-009-9192-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Indexed: 11/29/2022]
Abstract
Intracellular recording of potentials was used in isolated spinal cord segments from the frog Rana ridibunda to compare the inhibitory effects of GABA and glycine on the motoneuron membrane. At equal concentrations, the response (a change in membrane potential) to application of glycine was 1.5-2 times greater than the response to GABA in terms of amplitude, and EC(50) values were 0.75 and 1.57 mM, respectively. The response to simultaneous application of GABA and glycine averaged 79.1 +/- 2.4% (n = 19) of the sum of the individual responses and 130.1 +/- 1.5% (n = 19) of the glycine response (partial occlusion). Preliminary application of glycine decreased the GABA response by 85.3 +/- 0.2% (n = 10), while preapplication of GABA decreased the glycine response by only 52.9 +/- 0.3% (n = 11). The glycine and GABA responses were specifically suppressed by strychnine and bicuculline. These results provide evidence that as in mammals, amphibian motoneurons have both glycine (predominantly) and GABA(A) receptors; they also show that asymmetrical cross inhibition can occur.
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Affiliation(s)
- N I Kalinina
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 194223, St. Petersburg, Russia
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23
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24
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Schilling K, Oberdick J, Rossi F, Baader SL. Besides Purkinje cells and granule neurons: an appraisal of the cell biology of the interneurons of the cerebellar cortex. Histochem Cell Biol 2008; 130:601-15. [PMID: 18677503 DOI: 10.1007/s00418-008-0483-y] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2008] [Indexed: 01/29/2023]
Abstract
Ever since the groundbreaking work of Ramon y Cajal, the cerebellar cortex has been recognized as one of the most regularly structured and wired parts of the brain formed by a rather limited set of distinct cells. Its rather protracted course of development, which persists well into postnatal life, the availability of multiple natural mutants, and, more recently, the availability of distinct molecular genetic tools to identify and manipulate discrete cell types have suggested the cerebellar cortex as an excellent model to understand the formation and working of the central nervous system. However, the formulation of a unifying model of cerebellar function has so far proven to be a most cantankerous problem, not least because our understanding of the internal cerebellar cortical circuitry is clearly spotty. Recent research has highlighted the fact that cerebellar cortical interneurons are a quite more diverse and heterogeneous class of cells than generally appreciated, and have provided novel insights into the mechanisms that underpin the development and histogenetic integration of these cells. Here, we provide a short overview of cerebellar cortical interneuron diversity, and we summarize some recent results that are hoped to provide a primer on current understanding of cerebellar biology.
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Affiliation(s)
- Karl Schilling
- Anatomisches Institut, Anatomie und Zellbiologie, Rheinische Friedrich-Wilhelms-Universität, Nussalle 10, 53115 Bonn, Germany.
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25
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Tsvetkov EA, Veselkin NP. Interaction of the postsynaptic effects of glycine and GABA on spinal cord neurons in the frog Rana temporaria. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 2008; 38:589-96. [PMID: 18607736 DOI: 10.1007/s11055-008-9022-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Indexed: 10/21/2022]
Abstract
Studies were performed on mechanically isolated spinal cord multipolar cells (presumptive motoneurons) from the frog Rana temporaria using patch-clamp methods in the whole-cell configuration. These experiments showed that the amplitudes of transmembrane currents arising in response to simultaneous application of GABA and glycine were smaller than the sums of the amplitudes of the responses of the same neurons to GABA and glycine applied individually. Investigation of the mechanisms of this occlusion showed that superfusion of neurons with glycine solution (0.2 mM) resulted in complete blockade of responses to application of GABA (5 mM) and vice versa. This phenomenon may have resulted from cross-blockade associated with the existence of a single receptor complex sensitive to both GABA and glycine and from the interaction of GABA and glycine receptors.
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Affiliation(s)
- E A Tsvetkov
- I. M. Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 M. Torez Prospekt, St. Petersburg, Russia
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26
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Tsvetkov EA, Polina YA, Malkiel AI, Vesselkin NP. Effect of baclofen on ionotropic current evoked by application of glycine on spinal cord neurons of the frog Rana temporaria. J EVOL BIOCHEM PHYS+ 2008. [DOI: 10.1134/s0022093008030150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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27
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Schneider Gasser EM, Straub CJ, Panzanelli P, Weinmann O, Sassoè-Pognetto M, Fritschy JM. Immunofluorescence in brain sections: simultaneous detection of presynaptic and postsynaptic proteins in identified neurons. Nat Protoc 2007; 1:1887-97. [PMID: 17487173 DOI: 10.1038/nprot.2006.265] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Elucidating the molecular organization of synapses is essential for understanding brain function and plasticity. Immunofluorescence, combined with various fluorescent probes, is a sensitive and versatile method for morphological studies. However, analysis of synaptic proteins in situ is limited by epitope-masking after tissue fixation. Furthermore, postsynaptic proteins (such as ionotropic receptors and scaffolding proteins) often require weaker fixation for optimal detection than most intracellular markers, thereby hindering simultaneous visualization of these molecules. We present three protocols, which are alternatives to perfusion fixation, to overcome these restrictions. Brief tissue fixation shortly after interruption of vital functions preserves morphology and antigenicity. Combined with specific neuronal markers, selective detection of gamma-aminobutyric acid A (GABA(A)) receptors and the scaffolding protein gephyrin in relation to identified inhibitory presynaptic terminals in the rodent brain is feasible by confocal laser scanning microscopy. The most sophisticated of these protocols can be associated with electrophysiology for correlative studies of synapse structure and function. These protocols require 2-3 consecutive days for completion.
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Affiliation(s)
- Edith M Schneider Gasser
- Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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Aubrey KR, Rossi FM, Ruivo R, Alboni S, Bellenchi GC, Le Goff A, Gasnier B, Supplisson S. The transporters GlyT2 and VIAAT cooperate to determine the vesicular glycinergic phenotype. J Neurosci 2007; 27:6273-81. [PMID: 17554001 PMCID: PMC6672136 DOI: 10.1523/jneurosci.1024-07.2007] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The mechanisms that specify the vesicular phenotype of inhibitory interneurons in vertebrates are poorly understood because the two main inhibitory transmitters, glycine and GABA, share the same vesicular inhibitory amino acid transporter (VIAAT) and are both present in neurons during postnatal development. We have expressed VIAAT and the plasmalemmal transporters for glycine and GABA in a neuroendocrine cell line and measured the quantal release of glycine and GABA using a novel double-sniffer patch-clamp technique. We found that glycine is released from vesicles when VIAAT is coexpressed with either the neuronal transporter GlyT2 or the glial transporter GlyT1. However, GlyT2 was more effective than GlyT1, probably because GlyT2 is unable to operate in the reverse mode, which gives it an advantage in maintaining the high cytosolic glycine concentration required for efficient vesicular loading by VIAAT. The vesicular inhibitory phenotype was gradually altered from glycinergic to GABAergic through mixed events when GABA is introduced into the secretory cell and competes for uptake by VIAAT. Interestingly, the VIAAT ortholog from Caenorhabditis elegans (UNC-47), a species lacking glycine transmission, also supports glycine exocytosis in the presence of GlyT2, and a point mutation of UNC-47 that abolishes GABA transmission in the worm confers glycine specificity. Together, these results suggest that an increased cytosolic availability of glycine in VIAAT-containing terminals was crucial for the emergence of glycinergic transmission in vertebrates.
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Affiliation(s)
- Karin R Aubrey
- Laboratoire de Neurobiologie, Centre National de la Recherche Scientifique, Ecole Normale Supérieure, 75005 Paris, France
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Kneussel M, Loebrich S. Trafficking and synaptic anchoring of ionotropic inhibitory neurotransmitter receptors. Biol Cell 2007; 99:297-309. [PMID: 17504238 DOI: 10.1042/bc20060120] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Neurotransmitter receptors are subject to microtubule-based transport between intracellular organelles and the neuronal plasma membrane. Receptors that arrive at plasma membrane compartments diffuse laterally within the plane of the cellular surface. To achieve immobilization at their sites of action, cytoplasmic receptor residues bind to submembrane proteins, which are coupled to the underlying cytoskeleton by multiprotein scaffolds. GABA(A)Rs (gamma-aminobutyric type A receptors) and GlyRs (glycine receptors) are the major inhibitory receptors in the central nervous system. At inhibitory postsynaptic sites, all GlyRs and the majority of GABA(A)Rs directly or indirectly couple to gephyrin, a multimeric PSD (postsynaptic density) component. In addition to cluster formations at axo-dendritic contacts, individual GABA(A)R subtypes also anchor and concentrate at extrasynaptic positions, either through association with gephyrin or direct interaction with the ERM (ezrin/radixin/moesin) family protein radixin. In addition to their role in diffusion trapping of surface receptors, scaffold components also undergo rapid exchange to/from and between postsynaptic specializations, leading to a dynamic equilibrium of receptor-scaffold complexes. Moreover, scaffold components serve as adaptor proteins that mediate specificity in intracellular transport complexes. In the present review, we discuss the dynamic delivery, stabilization and removal of inhibitory receptors at synaptic sites.
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Affiliation(s)
- Matthias Kneussel
- Zentrum für Molekulare Neurobiologie Hamburg, ZMNH, Universität Hamburg, Falkenried 94, Germany.
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Sun Y, Godfrey DA, Godfrey TG, Rubin AM. Changes of amino acid concentrations in the rat vestibular nuclei after inferior cerebellar peduncle transection. J Neurosci Res 2007; 85:558-74. [PMID: 17131392 DOI: 10.1002/jnr.21136] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although there is a close relationship between the vestibular nuclear complex (VNC) and the cerebellum, little is known about the contribution of cerebellar inputs to amino acid neurotransmission in the VNC. Microdissection of freeze-dried brain sections and high-performance liquid chromatography (HPLC) were combined to measure changes of amino acid concentrations within the VNC of rats following transection of the cerebellovestibular connections in the inferior cerebellar peduncle. Distributions of 12 amino acids within the VNC at 2, 4, 7, and 30 days after surgery were compared with those for control and sham-lesioned rats. Concentrations of gamma-aminobutyric acid (GABA) decreased by 2 days after unilateral peduncle transection in nearly all VNC regions on the lesioned side and to lesser extents on the unlesioned side and showed partial recovery up to 30 days postsurgery. Asymmetries between the two sides of the VNC were maintained through 30 days. Glutamate concentrations were reduced bilaterally in virtually all regions of the VNC by 2 days and showed complete recovery in most VNC regions by 30 days. Glutamine concentrations increased, starting 2 days after surgery, especially on the lesioned side, so that there was asymmetry generally opposite that of glutamate. Concentrations of taurine, aspartate, and glycine also underwent partially reversible changes after peduncle transection. The results suggest that GABA and glutamate are prominent neurotransmitters in bilateral projections from the cerebellum to the VNC and that amino acid metabolism in the VNC is strongly influenced by its cerebellar connections.
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Affiliation(s)
- Yizhe Sun
- Division of Otolaryngology and Dentistry, Department of Surgery, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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Polina YA, Amakhin DV, Kozhanov VM, Kurchavyi GG, Veselkin NP. Three types of inhibitory miniature potentials in frog spinal cord motoneurons: Possible GABA and glycine cotransmission. ACTA ACUST UNITED AC 2007; 37:271-6. [PMID: 17294103 DOI: 10.1007/s11055-007-0011-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2005] [Indexed: 10/23/2022]
Abstract
Miniature inhibitory postsynaptic potentials (mIPSP) of motoneurons in isolated frog spinal cord were recorded in conditions of blockade of the conduction of nerve spikes and ionotropic glutamate receptors (TTX, 1 microM, CNQX, 25 microM, D-AP5, 50 microM). Three types of mIPSP were identified: those with fast and slow time characteristics and mIPSP with two-component decays. Two-component mIPSP accounted for 8.7% of all selected responses, fast mIPSP for 64.5%, and slow mIPSP for 26.8%. Blockade of GABA(A) receptors with bicuculline (20 microM) led to decreases in the numbers of slow and two-component mIPSP and an increase in the number of mIPSP with fast kinetics. Strychnine (1 microM), a blocker of glycine receptors, led to a reduction in the number of fast receptors and an increase in the number of slow potentials. These data suggest that frog spinal cord motoneurons have three types of inhibitory mIPSP, mediated by GABA, glycine, and simultaneous release of these two transmitters from the same presynaptic terminals.
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Affiliation(s)
- Yu A Polina
- Karelia State Pedagogical University, Petrozavodsk, Russia
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Yamada T, Terashima T, Okubo T, Juneja LR, Yokogoshi H. Effects of theanine, r-glutamylethylamide, on neurotransmitter release and its relationship with glutamic acid neurotransmission. Nutr Neurosci 2006; 8:219-26. [PMID: 16493792 DOI: 10.1080/10284150500170799] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
t Theanine, r-glutamylethylamide, is one of the major amino acid components in green tea and many researchers have compared theanine's effects with glutamic acid because the chemical structure is similar. In the previous study, we demonstrated that theanine can pass brain-blood barrier and may play as an agonist or an antagonist of some receptors. In this study, we investigated the effects of theanine on neurotransmitter release in the rat brain striatum by in vivo brain microdialysis and examined whether theanine affected glutamate transporters by comparing it with a glutamate transporter blocker, L-trans-Pyrrolidine-2,4-dicarboxylic acid (L-trans-2,4-PDC). Because we investigated whether the effects of theanine is similar to L-trans-2,4-PDC on the brain neurotransmission, we measured dopamine release and some amino acids release which are known as excitatory or inhibitory neurotransmitters from neurons by theanine or L-trans-2,4-PDC perfusion into the rat brain striatum. L-trans-2,4-PDC or theanine perfusion into the brain striatum caused dopamine release from dopaminergic neurons. In addition, L-trans-2,4-PDC perfusion increased glutamic acid, aspartic acid and, whereas theanine perfusion prevented aspartic acid release and increased glycine release. These results suggested that the mechanism of dopamine release caused by theanine is different from glutamate transporter blockers or glutamic acid. Further, L-trans-2,4-PDC cause excitatory neurotransmission, whereas theanine may inhibit excitatory neurotransmission and cause inhibitory neurotransmission via glycine receptors.
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Affiliation(s)
- Takashi Yamada
- Laboratory of Nutritional Biochemistry, Ministry of Education, Culture, Sports, Science and Technology of Japan, University of Shizuoka.
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van Zundert B, Castro P, Aguayo LG. Glycinergic and GABAergic synaptic transmission are differentially affected by gephyrin in spinal neurons. Brain Res 2005; 1050:40-7. [PMID: 15963957 DOI: 10.1016/j.brainres.2005.05.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2004] [Revised: 05/04/2005] [Accepted: 05/09/2005] [Indexed: 11/20/2022]
Abstract
In the present study, we have examined the physiological properties of synaptic currents mediated by GlyRs and GABAARs after culturing spinal neurons with a gephyrin antisense oligonucleotide. Application of gephyrin antisense, but not the sense, reduced the glycinergic mIPSC amplitude ( approximately 50%) and frequency ( approximately 85%), indicating the importance of gephyrin for GlyR anchoring at postsynaptic sites. On the other hand, the glycine-evoked current amplitude was unchanged indicating that functional GlyRs were still located in the extrasynaptic membrane. The analysis of the GABAergic transmission in the same neurons revealed approximately 70% reduction in the frequency of the GABAergic mIPSCs, without changes in the amplitude. Interestingly, the modulation of remaining GABAAR-mediated synaptic events by zinc and diazepam was significantly altered by the antisense. These results indicate that gephyrin is required for the membrane insertion/stabilization of the GABAAR gamma2 subunit as well as for its subsequent localization in the postsynaptic membrane.
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Affiliation(s)
- Brigitte van Zundert
- Department of Physiology, University of Concepción, Laboratory of Neurophysiology, P.O. Box 160-C, Concepción, Chile
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Abstract
The Mauthner (M) cell is a critical element in a vital escape "reflex" triggered by abrupt or threatening events. Its properties at the molecular and synaptic levels, their various forms of plasticity, and the design of its networks, are all well adapted for this survival function. They guarantee that this behavior is appropriately unilateral, variable, and unpredictable. The M cell sets the behavioral threshold, and, acting in concert with other elements of the brainstem escape network, determines when, where, and how the escape is executed.
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Affiliation(s)
- Henri Korn
- Laboratoire Recepteurs et Cognition, CNRS, URA 2182, Institut Pasteur, 25, rue du Docteur-Roux, 75724 Paris Cedex 15, France
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Shigenaga Y, Moritani M, Oh SJ, Park KP, Paik SK, Bae JY, Kim HN, Ma SK, Park CW, Yoshida A, Ottersen OP, Bae YC. The distribution of inhibitory and excitatory synapses on single, reconstructed jaw-opening motoneurons in the cat. Neuroscience 2005; 133:507-18. [PMID: 15878646 DOI: 10.1016/j.neuroscience.2005.02.022] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Revised: 02/03/2005] [Accepted: 02/12/2005] [Indexed: 11/21/2022]
Abstract
In a previous study, we reported that the distribution of inhibitory input, in contrast to excitatory input, decreased somatofugally along dendrites of cat jaw-closing alpha-motoneurons [J Comp Neurol 414 (1999) 454]. The present study examined the distribution of GABA, glycine, and glutamate immunopositive boutons covering horseradish peroxidase-labeled cat jaw-opening motoneurons. The motoneurons were divided into four compartments: the soma, and primary, intermediate, and distal dendrites. Ninety-seven percent of the total number of studied boutons had immunoreactivity for at least one of the three amino acids. The proportion of boutons immunoreactive for GABA and/or glycine was lower than the proportion of boutons immunoreactive for glutamate. Boutons immunoreactive to glycine alone were more numerous than boutons double-labeled for GABA and glycine, which, in turn, occurred more frequently than boutons immunoreactive to GABA alone. The percentage synaptic covering (proportion of membrane covered by synaptic boutons) of the putatively excitatory (glutamate containing) and putatively inhibitory (GABA and/or glycine containing) boutons decreased somatofugally along the dendrites. Such systematic variations were not seen in the packing density (number of boutons per 100 microm(2)); the packing density showed a distinct drop between the soma and primary dendrites but did not differ significantly among the three dendritic compartments. Overall, the packing density was slightly higher for the putatively excitatory boutons than for the inhibitory ones. When taken together with previous analyses of jaw-closing alpha-motoneurons the present data on jaw-opening alpha-motoneurons indicate that the two types of neuron differ in regard to the nature of synaptic integration in the dendritic tree.
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Affiliation(s)
- Y Shigenaga
- Department of Oral Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Jung-Gu, Daegu 700-412, Korea.
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36
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Abstract
The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning GlyR molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.
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Affiliation(s)
- Joseph W Lynch
- School of Biomedical Sciences, Univ. of Queensland, Brisbane QLD 4072, Australia.
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Rubio ME, Juiz JM. Differential distribution of synaptic endings containing glutamate, glycine, and GABA in the rat dorsal cochlear nucleus. J Comp Neurol 2004; 477:253-72. [PMID: 15305363 DOI: 10.1002/cne.20248] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The dorsal cochlear nucleus (DCN) integrates the synaptic information depending on the organization of the excitatory and inhibitory connections. This study provides, qualitatively and quantitatively, analyses of the organization and distribution of excitatory and inhibitory input on projection neurons (fusiform cells), and inhibitory interneurons (vertical and cartwheel cells) in the DCN, using a combination of high-resolution ultrastructural techniques together with postembedding immunogold labeling. The combination of ultrastructural morphometry together with immunogold labeling enables the identification and quantification of four major synaptic inputs according to their neurotransmitter content. Only one category of synaptic ending was immunoreactive for glutamate and three for glycine and/or gamma-aminobutyric-acid (GABA). Among those, nine subtypes of synaptic endings were identified. These differed in their ultrastructural characteristics and distribution in the nucleus and on three cell types analyzed. Four of the subtypes were immunoreactive for glutamate and contained round synaptic vesicles, whereas five were immunoreactive for glycine and/or GABA and contained flattened or pleomorphic synaptic vesicles. The analysis of the distribution of the nine synaptic endings on the cell types revealed that eight distributed on fusiform cells, six on vertical cells and five on cartwheel cells. In addition, postembedding immunogold labeling of the glycine receptor alpha1 subunit showed that it was present at postsynaptic membranes in apposition to synaptic endings containing flattened or pleomorphic synaptic vesicles and immunoreactive for glycine and/or GABA on the three cells analyzed. This information is valuable to our understanding of the response properties of DCN neurons.
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Affiliation(s)
- Maria E Rubio
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut 06269-4156, USA.
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Trudeau LE. Glutamate co-transmission as an emerging concept in monoamine neuron function. J Psychiatry Neurosci 2004; 29:296-310. [PMID: 15309046 PMCID: PMC446224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 03/01/2023] Open
Abstract
Converging research efforts over the last 4 decades have established beyond a doubt that many, if not most, neurons release more than 1 neurotransmitter. Although much attention has been paid to the co-release of small-molecule neurotransmitters with neuropeptides, a number of examples of co-release of 2 small-molecule neurotransmitters have now been described. It has been suggested recently that monoamine neurons use glutamate as a co-transmitter. First, both serotonin (5-HT) and dopamine (DA) neurons in culture establish functional glutamatergic synapses in addition to classic terminals that release 5-HT or DA. Second, immunocytochemical work has provided evidence for the presence of neurotransmitter pools of glutamate in DA, 5-HT and noradrenergic neurons. Third, the recent cloning of 3 vesicular glutamate transporters (VGLUT1-3) has led to the discovery that noradrenergic neurons contain VGLUT2 mRNA, whereas 5-HT neurons contain VGLUT3 mRNA. Finally, although VGLUT2 mRNA does not appear to be abundant in DA neurons in the adult brain, DA neurons cultured from neonatal animals express VGLUT2, suggesting that these neurons may have the capacity to express this protein under specific conditions. Taken together with recent work describing the capacity of neurons to change neurotransmitter phenotype during development or in an activity-dependent manner, the finding of glutamate co-transmission in monoamine neurons may lead to significant revisions of current physiologic models of monoamine neuron function. In addition, the possible role of glutamate co-release in physiopathologic models of diseases that implicate central monoamine pathways, such as schizophrenia, must now be seriously considered.
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Affiliation(s)
- Louis-Eric Trudeau
- Department of Pharmacology, Faculty of Medicine, Université de Montréal, Montréal, Que.
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Zhou C, Dacheux RF. AII amacrine cells in the rabbit retina possess AMPA-, NMDA-, GABA-, and glycine-activated currents. Vis Neurosci 2004; 21:181-8. [PMID: 15259569 DOI: 10.1017/s0952523804042099] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Physiological properties of ligand-activated currents were characterized for morphologically identified AII amacrine cells in the rabbit retina by using whole-cell recordings in a superfused retina slice preparation. The AII amacrine cells were identified based on their distinct narrow-field, bistratified morphology. In the present study, the whole-cell recordings from AII amacrine cells synaptically isolated from presynaptic influences demonstrated the presence of glutamate AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid) receptors, but no kainate receptors. The presence of only AMPA receptors on rabbit AII amacrine cells is in contrast to an earlier study on rabbit AII amacrine cells by Bloomfield and Xin (2000), but consistent with previous studies on rat AII amacrine cells. In addition, NMDA (N-methyl-D-aspartate) -activated currents blocked by the NMDA antagonist D-AP7 (D-2-amino-7-phosphonoheptanoic acid) were found on the AII amacrine cells. These most likely extrasynaptic NMDA-activated currents were attenuated by the presence of Co2+interacting with Mg2+and Ca2+as they competed for divalent cation-binding sites within the NMDA channel. AII amacrine cells also possessed GABA (γ-aminobutyric acid) -activated currents that were unaffected by the GABACreceptor antagonist TPMPA (1,2,5,6-tetrahydropyridine-4-yl methylphosphinic), but were completely blocked by the GABAAantagonist bicuculline. This indicates that the major inhibitory inputs were mediated by only GABAAreceptors located directly on the AII amacrine cells. Furthermore, although the AII amacrine cells were glycinergic amacrine cells, they also possessed glycine-activated currents that may be mediated by autoreceptors.
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Affiliation(s)
- Chengwen Zhou
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham 35294-0009, USA
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Baer K, Waldvogel HJ, During MJ, Snell RG, Faull RLM, Rees MI. Association of gephyrin and glycine receptors in the human brainstem and spinal cord: an immunohistochemical analysis. Neuroscience 2004; 122:773-84. [PMID: 14622920 DOI: 10.1016/s0306-4522(03)00543-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Gephyrin is a postsynaptic clustering molecule that forms a protein scaffold to anchor inhibitory neurotransmitter receptors at the postsynaptic membrane of neurons. Gephyrin was first identified as a protein component of the glycine receptor complex and is also colocalized with several GABAA receptor subunits in rodent brain. We have studied the distribution of gephyrin and glycine receptor subunits in the human brainstem and spinal cord using immunohistochemistry at light and confocal laser scanning microscopy levels. This study demonstrates the novel localization of gephyrin with glycine receptors in the human brainstem and spinal cord. Colocalization of immunoreactivities for gephyrin and glycine receptor subunits was detected in the dorsal and ventral horns of the spinal cord, the hypoglossal nucleus and the medial vestibular nucleus of the medulla. The results clearly establish that gephyrin is ubiquitously distributed and is colocalized, with a large proportion of glycine receptor subunits in the human brainstem and spinal cord. We therefore suggest that gephyrin functions as a clustering molecule for major subtypes of glycine receptors in the human CNS.
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Affiliation(s)
- K Baer
- Department of Molecular Medicine and Pathology, Faculty of Medical and Health Sciences, Private Bag 92019, University of Auckland, Auckland, New Zealand
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41
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van Zundert B, Alvarez FJ, Tapia JC, Yeh HH, Diaz E, Aguayo LG. Developmental-dependent action of microtubule depolymerization on the function and structure of synaptic glycine receptor clusters in spinal neurons. J Neurophysiol 2004; 91:1036-49. [PMID: 12968009 DOI: 10.1152/jn.00364.2003] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microtubules have been proposed to interact with gephyrin/glycine receptors (GlyRs) in synaptic aggregates. However, the consequence of microtubule disruption on the structure of postsynaptic GlyR/gephyrin clusters is controversial and possible alterations in function are largely unknown. In this study, we have examined the physiological and morphological properties of GlyR/gephyrin clusters after colchicine treatment in cultured spinal neurons during development. In immature neurons (5-7 DIV), disruption of microtubules resulted in a 33 +/- 4% decrease in the peak amplitude and a 72 +/- 15% reduction in the frequency of spontaneous glycinergic miniature postsynaptic currents (mIPSCs) recorded in whole cell mode. However, similar colchicine treatments resulted in smaller effects on 10-12 DIV neurons and no effect on mature neurons (15-17 DIV). The decrease in glycinergic mIPSC amplitude and frequency reflects postsynaptic actions of colchicine, since postsynaptic stabilization of microtubules with GTP prevented both actions and similar reductions in mIPSC frequency were obtained by modifying the Cl(-) driving force to obtain parallel reductions in mIPSC amplitude. Confocal microscopy revealed that colchicine reduced the average length and immunofluorescence intensity of synaptic gephyrin/GlyR clusters in immature (approximately 30%) and intermediate (approximately 15%) neurons, but not in mature clusters. Thus the structural and functional changes of postsynaptic gephyrin/GlyR clusters after colchicine treatment were tightly correlated. Finally, RT-PCR, kinetic analysis and picrotoxin blockade of glycinergic mIPSCs indicated a reorganization of the postsynaptic region from containing both alpha2beta and alpha1beta GlyRs in immature neurons to only alpha1beta GlyRs in mature neurons. Microtubule disruption preferentially affected postsynaptic sites containing alpha2beta-containing synaptic receptors.
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Affiliation(s)
- Brigitte van Zundert
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Concepción, Chile
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Waldvogel HJ, Baer K, Snell RG, During MJ, Faull RLM, Rees MI. Distribution of gephyrin in the human brain: an immunohistochemical analysis. Neuroscience 2003; 116:145-56. [PMID: 12535948 DOI: 10.1016/s0306-4522(02)00550-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Gephyrin is an ubiquitously expressed protein that, in the central nervous system, generates a protein scaffold to anchor inhibitory neurotransmitter receptors in the postsynaptic membrane. It was first identified as a protein component of the glycine receptor complex. Recent studies have demonstrated that gephyrin is colocalized with several subtypes of GABA(A) receptors and is part of postsynaptic GABA(A) receptor clusters. Here, we describe a study of the regional and cellular distribution of gephyrin in the human brain, determined by immunohistochemical localisation at the light and confocal laser scanning microscopic levels. At the regional level, gephyrin immunoreactivity was observed in most of the major brain regions examined. The most intense staining was in the cerebral cortex, hippocampus and caudate-putamen, in various brainstem nuclei with more moderate levels in the thalamus and cerebellum. At the cellular level gephyrin immunoreactivity was present on the plasma membranes of the soma and dendrites of pyramidal neurons throughout the various cortical regions examined. In the hippocampus, intense staining was observed on the granule cells of the dentate gyrus, and neurons of the CA1 and CA3 regions showed intense punctate gephyrin staining on their apical dendrites and cell bodies. Gephyrin immunoreactivity was also observed on neurons in the thalamus, globus pallidus and substantia nigra. In the putamen intense labelling of the striosomes was observed; most of the medium-sized neurons in the caudate-putamen were weakly labelled and many large neurons of the striatum were conspicuously stained. Many of the brainstem nuclei, notably the dorsal motor nucleus of the vagus, hypoglossal nucleus, trigeminal nucleus and inferior olive were all labelled with gephyrin. The spinal cord also showed high levels of gephyrin immunoreactivity. Our results demonstrate that the anchoring protein gephyrin is ubiquitously present in the human brain. We therefore suggest that gephyrin may have a central organizer role in assembling and stabilizing inhibitory postsynaptic membranes in human brain and is similar in function to those observed in the rodent brain. These findings contribute towards elucidating the role of gephyrin in the human brain.
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Affiliation(s)
- H J Waldvogel
- Department of Anatomy, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
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Danglot L, Triller A, Bessis A. Association of gephyrin with synaptic and extrasynaptic GABAA receptors varies during development in cultured hippocampal neurons. Mol Cell Neurosci 2003; 23:264-78. [PMID: 12812758 DOI: 10.1016/s1044-7431(03)00069-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Several studies have reported extrasynaptic clusters of GABAA receptors in hippocampal neurons. Yet their functional relevance as well as their evolution in relation with gephyrin during synaptogenesis remain unknown. We have analyzed the expression pattern of the main proteins of the GABAergic synapses during synaptogenesis in cultured hippocampal neurons. We found that GABAergic terminals, characterized by VIAAT and GAD-65 expression, differentiated 3 to 7 days after the glutamatergic endings. At the postsynaptic side, the GABAAR- beta3 subunit was first diffuse and then clustered when GABAergic terminals differentiated and gephyrin formed large clusters. Colocalization of these proteins was high and increased with development. At later stages, GABAAR beta3 clusters colocalized with gephyrin at synaptic but also at extrasynaptic sites. GABAAR gamma2 subunits were directly expressed as clusters which were first extrasynaptic and not associated with gephyrin. Subsequently, the GABAAR gamma2 subunits associated with gephyrin at synaptic and/or extrasynaptic sites. Our data indicate that formation of GABAAR gamma2 subunit clusters is gephyrin independent.
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Affiliation(s)
- Lydia Danglot
- Laboratoire de Biologie Cellulaire de la Synapse Normale et Pathologique, Institut National de la Santé et de la Recherche Médicale U497, Ecole Normale Supérieure, 75005, Paris, France
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Somogyi J. Differences in ratios of GABA, glycine and glutamate immunoreactivities in nerve terminals on rat hindlimb motoneurons: a possible source of post-synaptic variability. Brain Res Bull 2002; 59:151-61. [PMID: 12379445 DOI: 10.1016/s0361-9230(02)00843-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Previous pharmacological and physiological data on GABA and glycine receptor-dependent components of miniature inhibitory post-synaptic currents show that the electrophysiological characteristics of synaptic transmission from inhibitory synapses on spinal motoneurons are highly variable. Although post-synaptic factors are thought to be the major underlying cause of this variability, quantitative immunohistochemical data suggest that the transmitter content of afferents also vary from terminal to terminal. To examine whether ratios of amino acid staining densities vary similar to those of components of post-synaptic currents mediated by the corresponding receptors, we quantified immunogold labeling for GABA, glycine and the major excitatory transmitter, glutamate, in nerve terminals contacting the dendrites of motoneurons retrogradely labeled from the rat hindlimb muscle, biceps femoris. Nearly all terminals (94%) were immunoreactive for at least one amino acid and 64% of these contained two or three amino acids. All possible combinations of GABA, glycine and glutamate labeling were found. Over 70% of the terminals contained glycine, of which 60% also labeled for GABA. Of these GABA/glycine boutons, 40% also had glutamate. Half of all terminals contained GABA, but terminals immunoreactive for GABA alone were extremely rare. Immunoreactivity for glutamate occurred in 48% of all terminals and nearly 60% of these also contained glycine. Labeling densities for GABA, glycine and glutamate varied over a wide range from terminal to terminal. We hypothesize that this diversity in amino acid content may be a major underlying cause of variability in GABA- and glycine receptor-mediated components of miniature inhibitory post-synaptic currents in motoneurons.
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Affiliation(s)
- Jozsef Somogyi
- Cardiovascular Neuroscience Group, Cardiovascular Medicine and Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia.
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45
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Abstract
The clustering of glycine receptors and major subtypes of GABA(A) receptors at inhibitory synapses is mediated by the tubulin-binding protein gephyrin. In an attempt to identify additional components of inhibitory postsynaptic specializations, we performed a yeast two-hybrid screen using gephyrin as bait. Multiple positive clones encoded either the dynein light chain-1 (Dlc-1), also known as dynein LC8 and protein inhibitor of neuronal nitric oxide synthase, or its homolog Dlc-2. Dlc-1 protein bound efficiently to gephyrin in in vitro binding assays and colocalized with gephyrin during coexpression in HEK293 cells. The binding site for Dlc was mapped to a fragment of 63 amino acids within the central linker domain of gephyrin. In hippocampal neurons, endogenous Dlc protein was enriched at synaptic sites identified by synaptophysin and gephyrin immunostaining. Immunoelectron microscopy in spinal cord sections revealed Dlc immunoreactivity at the edges of postsynaptic differentiations, in close contact with cytoskeletal structures and at the periphery of the Golgi apparatus. Because Dlc-1 and Dlc-2 have been described as stoichiometric components of cytoplasmic dynein and myosin-Va complexes, our results suggest that motor proteins are involved in the subcellular localization of gephyrin.
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46
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Sotelo C, Cholley B, El Mestikawy S, Gozlan H, Hamon M. Direct Immunohistochemical Evidence of the Existence of 5-HT1A Autoreceptors on Serotoninergic Neurons in the Midbrain Raphe Nuclei. Eur J Neurosci 2002; 2:1144-1154. [PMID: 12106075 DOI: 10.1111/j.1460-9568.1990.tb00026.x] [Citation(s) in RCA: 227] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Physiological, pharmacological and radioautographic binding studies have suggested the presence of the 5-HT1A autoreceptors on midbrain serotoninergic neurons. The recent production of specific anti-rat 5-HT1A receptor antibodies in rabbits injected with a synthetic peptide has provided a tool to examine this problem directly. Using the immunoperoxidase method to localize the receptor protein, neurons of all the sizes and forms characterizing the neuronal populations in the dorsal and median raphe nuclei were stained. Reaction product was distributed along the neuronal surface, outlining the contours of perikarya and dendrites in a continuous but uneven manner. Intracellular staining was scarce and confined to the perinuclear region. Double immunohistochemical staining using the anti-5-HT1A receptor antibodies and an anti-serotonin (5-HT) antiserum showed that all the 5-HT1A receptor immunoreactive neurons in the dorsal raphe, and the vast majority of them in the median raphe, are serotoninergic neurons. These data provide the first direct demonstration of the existence of 5-HT1A autoreceptors on the perikarya and dendrites of serotoninergic neurons in the anterior raphe nuclei.
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Affiliation(s)
- Constantino Sotelo
- INSERM U. 106, Histologie Normale et Pathologique du Système Nerveux, Hôpital de la Salpétrière, 47 Boulevard de l'Hôpital, 75651 Paris Cédex 13, France
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47
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Kneussel M. Dynamic regulation of GABA(A) receptors at synaptic sites. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2002; 39:74-83. [PMID: 12086709 DOI: 10.1016/s0165-0173(02)00159-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
gamma-Aminobutyric acid type A receptors (GABA(A)Rs) mediate fast synaptic inhibition in brain and spinal cord. They are ligand-gated ion channels composed of numerous distinct subunit combinations. For efficient synaptic transmission, GABA(A)Rs need to be localized to and anchored at postsynaptic sites in precise apposition to presynaptic nerve terminals that release the neurotransmitter GABA. Neurons therefore require distinct mechanisms to regulate intracellular vesicular protein traffic, plasma membrane insertion, synaptic clustering and turnover of GABA(A)Rs. The GABA(A) receptor-associated protein GABARAP interacts with the gamma2 subunit of GABA(A)Rs and displays high homology to proteins involved in membrane fusion underlying Golgi transport and autophagic processes. The binding of GABARAP with NSF, microtubules and gephyrin together with its localization at intracellular membranes suggests a role in GABA(A)R targeting and/or degradation. Growth factor tyrosine kinase receptor activation is involved in the control of GABA(A)R levels at the plasma membrane. In particular insulin recruits GABA(A)Rs to the cell surface. Furthermore, the regulation of GABA(A)R surface half-life can also be the consequence of negative modulation at the proteasome level. Plic-1, a ubiquitin-like protein binds to both the proteasome and GABA(A)Rs and the Plic1-GABA(A)R interaction is important for the maintenance of GABA-activated current amplitudes. At synaptic sites, GABA(A)Rs are clustered via gephyrin-dependent and gephyrin-independent mechanisms and may subsequently become internalized via clathrin-mediated endocytosis underlying receptor recycling or degradation processes. This article discusses these recent data in the field of GABA(A)R dynamics.
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Affiliation(s)
- Matthias Kneussel
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, Deutschordenstrasse 46, D-60528 Frankfurt/Main, Germany.
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Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev 2002; 82:503-68. [PMID: 11917096 DOI: 10.1152/physrev.00029.2001] [Citation(s) in RCA: 934] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cl- channels reside both in the plasma membrane and in intracellular organelles. Their functions range from ion homeostasis to cell volume regulation, transepithelial transport, and regulation of electrical excitability. Their physiological roles are impressively illustrated by various inherited diseases and knock-out mouse models. Thus the loss of distinct Cl- channels leads to an impairment of transepithelial transport in cystic fibrosis and Bartter's syndrome, to increased muscle excitability in myotonia congenita, to reduced endosomal acidification and impaired endocytosis in Dent's disease, and to impaired extracellular acidification by osteoclasts and osteopetrosis. The disruption of several Cl- channels in mice results in blindness. Several classes of Cl- channels have not yet been identified at the molecular level. Three molecularly distinct Cl- channel families (CLC, CFTR, and ligand-gated GABA and glycine receptors) are well established. Mutagenesis and functional studies have yielded considerable insights into their structure and function. Recently, the detailed structure of bacterial CLC proteins was determined by X-ray analysis of three-dimensional crystals. Nonetheless, they are less well understood than cation channels and show remarkably different biophysical and structural properties. Other gene families (CLIC or CLCA) were also reported to encode Cl- channels but are less well characterized. This review focuses on molecularly identified Cl- channels and their physiological roles.
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Affiliation(s)
- Thomas J Jentsch
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany.
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Lüscher B, Fritschy JM. Subcellular localization and regulation of GABAA receptors and associated proteins. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2002; 48:31-64. [PMID: 11526740 DOI: 10.1016/s0074-7742(01)48013-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Affiliation(s)
- B Lüscher
- Department of Biology and Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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Bae YC, Choi BJ, Lee MG, Lee HJ, Park KP, Zhang LF, Honma S, Fukami H, Yoshida A, Ottersen OP, Shigenaga Y. Quantitative ultrastructural analysis of glycine- and gamma-aminobutyric acid-immunoreactive terminals on trigeminal alpha- and gamma-motoneuron somata in the rat. J Comp Neurol 2002; 442:308-19. [PMID: 11793336 DOI: 10.1002/cne.10092] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Detailed knowledge of the inhibitory input to trigeminal motoneurons is needed to understand better the central mechanisms of jaw movements. Here a quantitative analysis of terminals contacting somata of jaw-closing (JC) and jaw-opening (JO) alpha-motoneurons, and of JC gamma-motoneurons, was performed by use of serial sectioning and postembedding immunogold cytochemistry. For each type of motoneuron, the synaptic boutons were classified into four groups, i.e., immunonegative boutons or boutons immunoreactive to glycine only, to gamma-aminobutyric acid (GABA) only, or to both glycine and GABA. The density of immunolabeled boutons was much higher for the alpha- than for the gamma-motoneurons. In the alpha-motoneuron populations, the immunolabeled boutons were subdivided into one large group of boutons containing glycine-like immunoreactivity only, one group of intermediate size harboring both glycine- and GABA-like immunoreactivity, and a small group of boutons containing GABA-like immunoreactivity only. The percentage of immunolabeled boutons was higher for JC than JO alpha-motoneurons, the most pronounced difference being observed for glycine-like immunoreactivity. In contrast, on the somatic membrane of gamma-motoneurons, the three types of immunoreactive bouton occurred at similar frequencies. These results indicate that trigeminal motoneurons are strongly and differentially controlled by premotoneurons containing glycine and/or GABA and suggest that these neurons play an important role for the generation of masticatory patterns.
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Affiliation(s)
- Yong Chul Bae
- Department of Oral Anatomy, School of Dentistry, Kyungpook University, Taegu 700-422, Korea.
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