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Phillips S, Chatham JC, McMahon LL. Forskolin reverses the O-GlcNAcylation dependent decrease in GABAAR current amplitude at hippocampal synapses possibly at a neurosteroid site on GABAARs. RESEARCH SQUARE 2024:rs.3.rs-4140038. [PMID: 38659738 PMCID: PMC11042418 DOI: 10.21203/rs.3.rs-4140038/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
GABAergic transmission is influenced by post-translational modifications, like phosphorylation, impacting channel conductance, allosteric modulator sensitivity, and membrane trafficking. O-GlcNAcylation is a post-translational modification involving the O-linked attachment of β-N-acetylglucosamine on serine/threonine residues. Previously we reported an acute increase in O-GlcNAcylation elicits a long-term depression of evoked GABAAR inhibitory post synaptic currents (eIPSCs) onto hippocampal principal cells. Importantly, O-GlcNAcylation and phosphorylation can co-occur or compete for the same residue; whether they interact in modulating GABAergic IPSCs is unknown. We tested this by recording IPSCs from hippocampal principal cells and pharmacologically increased O-GlcNAcylation, before or after increasing serine phosphorylation using the adenylate cyclase activator, forskolin. Although forskolin had no significant effect on baseline eIPSC amplitude, we found that a prior increase in O-GlcNAcylation unmasks a forskolin-dependent increase in eIPSC amplitude, reversing the O-GlcNAc-induced eIPSC depression. Inhibition of adenylate cyclase or protein kinase A did not prevent the potentiating effect of forskolin, indicating serine phosphorylation is not the mechanism. Surprisingly, increasing O-GlcNAcylation also unmasked a potentiating effect of the neurosteroids 5α-pregnane-3α,21-diol-20-one (THDOC) and progesterone on eIPSC amplitude, mimicking forskolin. Our findings show under conditions of heightened O-GlcNAcylation, the neurosteroid site on synaptic GABAARs is accessible to agonists, permitting strengthening of synaptic inhibition.
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Phillips S, Chatham JC, McMahon L. Forskolin reverses the O-GlcNAcylation dependent decrease in GABAAR current amplitude at hippocampal synapses possibly through a neurosteroid site on GABAARs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.06.583612. [PMID: 38496430 PMCID: PMC10942432 DOI: 10.1101/2024.03.06.583612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
GABAergic transmission is influenced by post-translational modifications, like phosphorylation, impacting channel conductance, allosteric modulator sensitivity, and membrane trafficking. O-GlcNAcylation is a post-translational modification involving the O-linked attachment of β-N-acetylglucosamine on serine/threonine residues. Previously we reported an acute increase in O-GlcNAcylation elicits a long-term depression of evoked GABAAR inhibitory post synaptic currents (eIPSCs) onto hippocampal principal cells. Importantly O-GlcNAcylation and phosphorylation can co-occur or compete for the same residue; whether they interact in modulating GABAergic IPSCs is unknown. We tested this by recording IPSCs from hippocampal principal cells and pharmacologically increased O-GlcNAcylation, before or after increasing serine phosphorylation using the adenylate cyclase activator, forskolin. Although forskolin had no significant effect on baseline eIPSC amplitude, we found that a prior increase in O-GlcNAcylation unmasks a forskolin-dependent increase in eIPSC amplitude, reversing the O-GlcNAc-induced eIPSC depression. Inhibition of adenylate cyclase or protein kinase A did not prevent the potentiating effect of forskolin, indicating serine phosphorylation is not the mechanism. Surprisingly, increasing O-GlcNAcylation also unmasked a potentiating effect of the neurosteroids 5α-pregnane-3α,21-diol-20-one (THDOC) and progesterone on eIPSC amplitude, mimicking forskolin. Our findings show under conditions of heightened O-GlcNAcylation, the neurosteroid site on synaptic GABAARs is accessible to agonists, permitting strengthening of synaptic inhibition.
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García-Rojas F, Flores-Muñoz C, Santander O, Solis P, Martínez AD, Ardiles ÁO, Fuenzalida M. Pannexin-1 Modulates Inhibitory Transmission and Hippocampal Synaptic Plasticity. Biomolecules 2023; 13:887. [PMID: 37371467 DOI: 10.3390/biom13060887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/22/2023] [Accepted: 05/23/2023] [Indexed: 06/29/2023] Open
Abstract
Pannexin-1 (Panx1) hemichannel is a non-selective transmembrane channel that may play important roles in intercellular signaling by allowing the permeation of ions and metabolites, such as ATP. Although recent evidence shows that the Panx1 hemichannel is involved in controlling excitatory synaptic transmission, the role of Panx1 in inhibitory transmission remains unknown. Here, we studied the contribution of Panx1 to the GABAergic synaptic efficacy onto CA1 pyramidal neurons (PyNs) by using patch-clamp recordings and pharmacological approaches in wild-type and Panx1 knock-out (Panx1-KO) mice. We reported that blockage of the Panx1 hemichannel with the mimetic peptide 10Panx1 increases the synaptic level of endocannabinoids (eCB) and the activation of cannabinoid receptors type 1 (CB1Rs), which results in a decrease in hippocampal GABAergic efficacy, shifting excitation/inhibition (E/I) balance toward excitation and facilitating the induction of long-term potentiation. Our finding provides important insight unveiling that Panx1 can strongly influence the overall neuronal excitability and play a key role in shaping synaptic changes affecting the amplitude and direction of plasticity, as well as learning and memory processes.
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Affiliation(s)
- Francisca García-Rojas
- Centro de Neurobiología y Fisiopatología Integrativa, CENFI, Instituto de Fisiología, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Carolina Flores-Muñoz
- Centro de Neurobiología y Fisiopatología Integrativa, CENFI, Instituto de Fisiología, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Centro de Neurología Traslacional, Facultad de Medicina, Universidad de Valparaíso, Valparaíso 2341386, Chile
| | - Odra Santander
- Centro de Neurobiología y Fisiopatología Integrativa, CENFI, Instituto de Fisiología, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Pamela Solis
- Centro de Neurobiología y Fisiopatología Integrativa, CENFI, Instituto de Fisiología, Universidad de Valparaíso, Valparaíso 2340000, Chile
- Programa de Magister en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso 2340000, Chile
| | - Agustín D Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Álvaro O Ardiles
- Centro de Neurología Traslacional, Facultad de Medicina, Universidad de Valparaíso, Valparaíso 2341386, Chile
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
- Centro Interdisciplinario de Estudios en Salud, Escuela de Medicina, Facultad de Medicina, Universidad de Valparaíso, Viña del Mar 2572007, Chile
| | - Marco Fuenzalida
- Centro de Neurobiología y Fisiopatología Integrativa, CENFI, Instituto de Fisiología, Universidad de Valparaíso, Valparaíso 2340000, Chile
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Li C, Huang S, Peng J, Hong T, Zhou C, Tang J. 14-3-3ζ Mediates GABA AR Activation by Interacting with BIG1. Mol Neurobiol 2023; 60:1721-1732. [PMID: 36562883 DOI: 10.1007/s12035-022-03172-z] [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: 07/28/2022] [Accepted: 12/10/2022] [Indexed: 12/24/2022]
Abstract
Most fast synaptic inhibitions in the mammalian brain are mediated by GABAA receptors (GABAARs). An appropriate level of GABAAR expression at the cell surface is essential for neurodevelopment and the efficacy of GABAergic synaptic transmission. We previously reported that brefeldin A-inhibited GDP/GTP exchange factor 1 (BIG1), a binding partner of GABAARs, plays an important role in trafficking GABAARs to the cell surface. However, its regulatory mechanisms remain unknown. In the present study, we identified a new cellular protein, 14-3-3ζ, which can interact with the β subunit of GABAARs and BIG1 both in vitro and in vivo and colocalizes in the soma, dendrites, and axons of hippocampal neurons. Overexpression of 14-3-3ζ-WT increased the surface expression of BIG1 in dendrites and axons, as well as the binding of BIG1 with GABAAR. Depleted 14-3-3ζ with efficacious siRNA attenuated the interaction between BIG1 and GABAARs and resulted in significant decreases in the surface expression levels of BIG1 and GABAAR. GABAAR agonist treatment increased the expression levels of BIG1 and 14-3-3ζ on the surface, indicating that 14-3-3ζ is involved in regulating BIG1-mediated GABAAR surface expression. Depletion of BIG1 or 14-3-3ζ significantly decreased GABAAR expression at the cell surface and suppressed the GABA-gated influx of chloride ions. These data indicate that the combination of 14-3-3ζ and BIG1 is required for GABAAR membrane expression. Our results provide a potential promising therapeutic target for neurological disorders involving GABAergic synaptic transmission.
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Affiliation(s)
- Cuixian Li
- Experiment Teaching & Administration Center, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Shen Huang
- Experiment Teaching & Administration Center, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Jin Peng
- Laboratory of Pharmacology and Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, 510515, China
| | - Tianguo Hong
- Experiment Teaching & Administration Center, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China
| | - Chun Zhou
- Laboratory of Immunopharmacology, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, 510515, China.
- SMU-KI United Medical Inflammatory Center, School of Pharmaceutical Sciences; Guangdong Provincial Key Laboratory of Shock and Microcirculation, Southern Medical University, Guangzhou, 510515, China.
| | - Jie Tang
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, 510515, China.
- Department of Physiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, 510515, China.
- Department of Otolaryngology Head & Neck Surgery, Zhujiang Hospital, Southern Medical University, Guangzhou, 510282, China.
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Wang B, Zhao M, Su Z, Jin B, Yang X, Zhang C, Guo B, Li J, Hong W, Liu J, Zhao Y, Hou Y, Lai F, Zhang W, Qin L, Zhang W, Luo J, Zheng R. RIIβ-PKA in GABAergic Neurons of Dorsal Median Hypothalamus Governs White Adipose Browning. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2205173. [PMID: 36529950 PMCID: PMC9929258 DOI: 10.1002/advs.202205173] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/18/2022] [Indexed: 06/17/2023]
Abstract
The RIIβ subunit of cAMP-dependent protein kinase A (PKA) is expressed in the brain and adipose tissue. RIIβ-knockout mice show leanness and increased UCP1 in brown adipose tissue. The authors have previously reported that RIIβ reexpression in hypothalamic GABAergic neurons rescues the leanness. However, whether white adipose tissue (WAT) browning contributes to the leanness and whether RIIβ-PKA in these neurons governs WAT browning are unknown. Here, this work reports that RIIβ-KO mice exhibit a robust WAT browning. RIIβ reexpression in dorsal median hypothalamic GABAergic neurons (DMH GABAergic neurons) abrogates WAT browning. Single-cell sequencing, transcriptome sequencing, and electrophysiological studies show increased GABAergic activity in DMH GABAergic neurons of RIIβ-KO mice. Activation of DMH GABAergic neurons or inhibition of PKA in these neurons elicits WAT browning and thus lowers body weight. These findings reveal that RIIβ-PKA in DMH GABAergic neurons regulates WAT browning. Targeting RIIβ-PKA in DMH GABAergic neurons may offer a clinically useful way to promote WAT browning for treating obesity and other metabolic disorders.
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Affiliation(s)
- Bingwei Wang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Miao Zhao
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Zhijie Su
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Baohua Jin
- Department of PharmacologyInstitution of Chinese Integrative MedicineHebei Medical UniversityShijiazhuang050017P. R. China
| | - Xiaoning Yang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Chenyu Zhang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Bingbing Guo
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Jiebo Li
- Institute of Medical PhotonicsBeijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijing100191P. R. China
| | - Weili Hong
- Institute of Medical PhotonicsBeijing Advanced Innovation Center for Biomedical EngineeringSchool of Biological Science and Medical EngineeringBeihang UniversityBeijing100191P. R. China
| | - Jiarui Liu
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Yun Zhao
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Yujia Hou
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Futing Lai
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Wei Zhang
- Department of PharmacologyInstitution of Chinese Integrative MedicineHebei Medical UniversityShijiazhuang050017P. R. China
| | - Lihua Qin
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Weiguang Zhang
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Jianyuan Luo
- Department of Medical GeneticsSchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
- Department of Biochemistry and Molecular BiologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
| | - Ruimao Zheng
- Department of AnatomyHistology and EmbryologySchool of Basic Medical SciencesPeking UniversityBeijing100191P. R. China
- Neuroscience Research InstituteKey Laboratory for Neuroscience of Ministry of EducationKey Laboratory for Neuroscience of National Health Commission of the People's Republic of ChinaPeking UniversityBeijing100191P. R. China
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Deane DT, Cope TA, Schulz AM, Bennett ET, Hughes RM. Design, Heterologous Expression, and Application of an Immobilized Protein Kinase. Bioconjug Chem 2023; 34:204-211. [PMID: 36379001 DOI: 10.1021/acs.bioconjchem.2c00485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Protein kinase A (PKA) is a biologically important enzyme for cell regulation, often referred to as the "central kinase". An immobilized PKA that retains substrate specificity and activity would be a useful tool for laboratory scientists, enabling targeted phosphorylation without interference from downstream kinase contamination or kinase autophosphorylation in sensitive assays. Moreover, it might also provide the benefits of robustness and reusability that are often associated with immobilized enzyme preparations. In this work, we describe the creation of a recombinant PKA fusion protein that incorporates the HaloTag covalent immobilization system. We demonstrate that protein fusion design, including affinity tag placement, is critical for optimal heterologous expression in Escherichia coli. Furthermore, we demonstrate various applications of our immobilized PKA, including the phosphorylation of recombinant PKA substrates, such as vasodilator-stimulated phosphoprotein, and endogenous PKA substrates in a cell lysate. This immobilized PKA also possesses robust activity and reusability over multiple trials. This work holds promise as a generalizable strategy for the production and application of immobilized protein kinases.
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Affiliation(s)
- Dalton T Deane
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Thomas A Cope
- University of Alabama, Tuscaloosa, Alabama 35487, United States
| | - Anna M Schulz
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Edward T Bennett
- University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27514, United States
| | - Robert M Hughes
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
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Wang L, Wang B, Wu C, Wang J, Sun M. Autism Spectrum Disorder: Neurodevelopmental Risk Factors, Biological Mechanism, and Precision Therapy. Int J Mol Sci 2023; 24:ijms24031819. [PMID: 36768153 PMCID: PMC9915249 DOI: 10.3390/ijms24031819] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 01/12/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023] Open
Abstract
Autism spectrum disorder (ASD) is a heterogeneous, behaviorally defined neurodevelopmental disorder. Over the past two decades, the prevalence of autism spectrum disorders has progressively increased, however, no clear diagnostic markers and specifically targeted medications for autism have emerged. As a result, neurobehavioral abnormalities, neurobiological alterations in ASD, and the development of novel ASD pharmacological therapy necessitate multidisciplinary collaboration. In this review, we discuss the development of multiple animal models of ASD to contribute to the disease mechanisms of ASD, as well as new studies from multiple disciplines to assess the behavioral pathology of ASD. In addition, we summarize and highlight the mechanistic advances regarding gene transcription, RNA and non-coding RNA translation, abnormal synaptic signaling pathways, epigenetic post-translational modifications, brain-gut axis, immune inflammation and neural loop abnormalities in autism to provide a theoretical basis for the next step of precision therapy. Furthermore, we review existing autism therapy tactics and limits and present challenges and opportunities for translating multidisciplinary knowledge of ASD into clinical practice.
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Blednov YA, Da Costa A, Mason S, Mayfield J, Moss SJ, Messing RO. Apremilast-induced increases in acute ethanol intoxication and decreases in ethanol drinking in mice involve PKA phosphorylation of GABA A β3 subunits. Neuropharmacology 2022; 220:109255. [PMID: 36152689 PMCID: PMC9810330 DOI: 10.1016/j.neuropharm.2022.109255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/23/2022] [Accepted: 09/10/2022] [Indexed: 01/05/2023]
Abstract
We previously showed that apremilast, an FDA-approved PDE4 inhibitor, selectively alters behavioral responses to ethanol and certain GABAergic drugs in a PKA-dependent manner in C57BL6/J mice. Here, we investigated if PKA phosphorylation of β3 GABAA receptor subunits is involved in apremilast regulation of ethanol, propofol, or diazepam responses. Apremilast prolonged rotarod ataxia and loss of the righting reflex by ethanol and propofol in wild-type mice, but not in β3-S408A/S409A knock-in mice. In contrast, apremilast hastened recovery from the ataxic and sedative effects of diazepam in both genotypes. These findings suggest that apremilast modulation of ethanol and propofol behaviors in wild-type mice is mediated by β3 subunit phosphorylation, whereas its actions on diazepam responses involve a different mechanism. The PKA inhibitor H-89 prevented apremilast modulation of ethanol-induced ataxia. Apremilast sensitized wild-type males to ethanol-induced ataxia and decreased acute functional tolerance (AFT) in females but had no effect in β3-S408A/S409A mice of either sex. These results could not be attributed to genotype differences in blood ethanol clearance. There were also no baseline genotype differences in ethanol consumption and preference in two different voluntary drinking procedures. However, the ability of apremilast to reduce ethanol consumption was diminished in β3-S408A/S409A mice. Our results provide strong evidence that PKA-dependent phosphorylation of β3 GABAA receptor subunits is an important mechanism by which apremilast increases acute sensitivity to alcohol, decreases AFT, and decreases ethanol drinking.
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Affiliation(s)
- Yuri A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Adriana Da Costa
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Sonia Mason
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Jody Mayfield
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Stephen J Moss
- Department of Neuroscience, Tufts University School of Medicine, Boston, MA, 02111, USA
| | - Robert O Messing
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA; Department of Neuroscience, The University of Texas at Austin, Austin, TX, 78712, USA; Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, 78712, USA.
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Braga MFM, Juranek J, Eiden LE, Li Z, Figueiredo TH, de Araujo Furtado M, Marini AM. GABAergic circuits of the basolateral amygdala and generation of anxiety after traumatic brain injury. Amino Acids 2022; 54:1229-1249. [PMID: 35798984 DOI: 10.1007/s00726-022-03184-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Accepted: 06/20/2022] [Indexed: 11/25/2022]
Abstract
Traumatic brain injury (TBI) has reached epidemic proportions around the world and is a major public health concern in the United States. Approximately 2.8 million individuals sustain a traumatic brain injury and are treated in an Emergency Department yearly in the U.S., and about 50,000 of them die. Persistent symptoms develop in 10-15% of the cases including neuropsychiatric disorders. Anxiety is the second most common neuropsychiatric disorder that develops in those with persistent neuropsychiatric symptoms after TBI. Abnormalities or atrophy in the temporal lobe has been shown in the overwhelming number of TBI cases. The basolateral amygdala (BLA), a temporal lobe structure that consolidates, stores and generates fear and anxiety-based behavioral outputs, is a critical brain region in the anxiety circuitry. In this review, we sought to capture studies that characterized the relationship between human post-traumatic anxiety and structural/functional alterations in the amygdala. We compared the human findings with results obtained with a reproducible mild TBI animal model that demonstrated a direct relationship between the alterations in the BLA and an anxiety-like phenotype. From this analysis, both preliminary insights, and gaps in knowledge, have emerged which may open new directions for the development of rational and more efficacious treatments.
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Affiliation(s)
- Maria F M Braga
- Department of Anatomy, Physiology and Genetics and Program in Neuroscience, Uniformed Services University of the Health Science School of Medicine, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA
| | - Jenifer Juranek
- Department of Pediatric Surgery, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, TX, 77030, USA
| | - Lee E Eiden
- Section On Molecular Neuroscience, National Institute of Mental Health, Intramural Research Program, Bethesda, MD, 20814, USA
| | - Zheng Li
- Section On Synapse Development and Plasticity, National Institute of Mental Health, Intramural Research Program, Bethesda, MD, 20814, USA
| | - Taiza H Figueiredo
- Department of Anatomy, Physiology and Genetics and Program in Neuroscience, Uniformed Services University of the Health Science School of Medicine, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA
| | - Marcio de Araujo Furtado
- Department of Anatomy, Physiology and Genetics and Program in Neuroscience, Uniformed Services University of the Health Science School of Medicine, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA
| | - Ann M Marini
- Department of Neurology and Program in Neuroscience, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA.
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Halff EF, Hannan S, Kwanthongdee J, Lesept F, Smart TG, Kittler JT. Phosphorylation of neuroligin-2 by PKA regulates its cell surface abundance and synaptic stabilization. Sci Signal 2022; 15:eabg2505. [PMID: 35727864 DOI: 10.1126/scisignal.abg2505] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The trans-synaptic adhesion molecule neuroligin-2 (NL2) is essential for the development and function of inhibitory synapses. NL2 recruits the postsynaptic scaffold protein gephyrin, which, in turn, stabilizes γ-aminobutyric acid type A receptors (GABAARs) in the postsynaptic domain. Thus, the amount of NL2 at the synapse can control synaptic GABAAR concentration to tune inhibitory neurotransmission efficacy. Here, using biochemistry, imaging, single-particle tracking, and electrophysiology, we uncovered a key role for cAMP-dependent protein kinase (PKA) in the synaptic stabilization of NL2. We found that PKA-mediated phosphorylation of NL2 at Ser714 caused its dispersal from the synapse and reduced NL2 surface amounts, leading to a loss of synaptic GABAARs. Conversely, enhancing the stability of NL2 at synapses by abolishing PKA-mediated phosphorylation led to increased inhibitory signaling. Thus, PKA plays a key role in regulating NL2 function and GABA-mediated synaptic inhibition.
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Affiliation(s)
- Els F Halff
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Saad Hannan
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Jaturon Kwanthongdee
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK.,Princess Srisavangavadhana College of Medicine, Chulabhorn Royal Academy, Bangkok 10210, Thailand
| | - Flavie Lesept
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Josef T Kittler
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
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11
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Rhynchosia volubilis Promotes Cell Survival via cAMP-PKA/ERK-CREB Pathway. Pharmaceuticals (Basel) 2022; 15:ph15010073. [PMID: 35056130 PMCID: PMC8778899 DOI: 10.3390/ph15010073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/29/2021] [Accepted: 01/03/2022] [Indexed: 02/01/2023] Open
Abstract
Rhynchosia volubilis, a small black bean, has been used as a traditional remedy to treat diseases and maintain health in East Asia, but its cellular effects and molecular mechanisms are not fully understood. The purpose of this study was to investigate the effect of ethanol extract from Rhynchosia volubilis (EERV) on cell survival and to elucidate the biochemical signaling pathways. Our results showed that EERV stimulated the cyclic AMP (cAMP) signal revealed by a fluorescent protein (FP)-based intensiometric sensor. Using a Förster resonance energy transfer (FRET)-based sensor, we further revealed that EERV could activate PKA and ERK signals, which are downstream effectors of cAMP. In addition, we reported that EERV could induce the phosphorylation of CREB, a key signal for cell survival. Thus, our results suggested that EERV protects against apoptosis by activating the cell survival pathway through the cAMP-PKA/ERK-CREB pathway.
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12
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Significance of GABA A Receptor for Cognitive Function and Hippocampal Pathology. Int J Mol Sci 2021; 22:ijms222212456. [PMID: 34830337 PMCID: PMC8623595 DOI: 10.3390/ijms222212456] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Revised: 11/08/2021] [Accepted: 11/08/2021] [Indexed: 02/05/2023] Open
Abstract
The hippocampus is a primary area for contextual memory, known to process spatiotemporal information within a specific episode. Long-term strengthening of glutamatergic transmission is a mechanism of contextual learning in the dorsal cornu ammonis 1 (CA1) area of the hippocampus. CA1-specific immobilization or blockade of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor delivery can impair learning performance, indicating a causal relationship between learning and receptor delivery into the synapse. Moreover, contextual learning also strengthens GABAA (gamma-aminobutyric acid) receptor-mediated inhibitory synapses onto CA1 neurons. Recently we revealed that strengthening of GABAA receptor-mediated inhibitory synapses preceded excitatory synaptic plasticity after contextual learning, resulting in a reduced synaptic excitatory/inhibitory (E/I) input balance that returned to pretraining levels within 10 min. The faster plasticity at inhibitory synapses may allow encoding a contextual memory and prevent cognitive dysfunction in various hippocampal pathologies. In this review, we focus on the dynamic changes of GABAA receptor mediated-synaptic currents after contextual learning and the intracellular mechanism underlying rapid inhibitory synaptic plasticity. In addition, we discuss that several pathologies, such as Alzheimer’s disease, autism spectrum disorders and epilepsy are characterized by alterations in GABAA receptor trafficking, synaptic E/I imbalance and neuronal excitability.
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13
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Sexton CA, Penzinger R, Mortensen M, Bright DP, Smart TG. Structural determinants and regulation of spontaneous activity in GABA A receptors. Nat Commun 2021; 12:5457. [PMID: 34526505 PMCID: PMC8443696 DOI: 10.1038/s41467-021-25633-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/24/2021] [Indexed: 11/25/2022] Open
Abstract
GABAA receptors are vital for controlling neuronal excitability and can display significant levels of constitutive activity that contributes to tonic inhibition. However, the mechanisms underlying spontaneity are poorly understood. Here we demonstrate a strict requirement for β3 subunit incorporation into receptors for spontaneous gating, facilitated by α4, α6 and δ subunits. The crucial molecular determinant involves four amino acids (GKER) in the β3 subunit's extracellular domain, which interacts with adjacent receptor subunits to promote transition to activated, open channel conformations. Spontaneous activity is further regulated by β3 subunit phosphorylation and by allosteric modulators including neurosteroids and benzodiazepines. Promoting spontaneous activity reduced neuronal excitability, indicating that spontaneous currents will alter neural network activity. This study demonstrates how regional diversity in GABAA receptor isoform, protein kinase activity, and neurosteroid levels, can impact on tonic inhibition through the modulation of spontaneous GABAA receptor gating.
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Affiliation(s)
- Craig A Sexton
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Reka Penzinger
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Martin Mortensen
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Damian P Bright
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology & Pharmacology, UCL, London, UK.
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14
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Regulation of GABA A Receptors Induced by the Activation of L-Type Voltage-Gated Calcium Channels. MEMBRANES 2021; 11:membranes11070486. [PMID: 34209589 PMCID: PMC8304739 DOI: 10.3390/membranes11070486] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 12/30/2022]
Abstract
GABAA receptors are pentameric ion channels that mediate most synaptic and tonic extrasynaptic inhibitory transmissions in the central nervous system. There are multiple GABAA receptor subtypes constructed from 19 different subunits in mammals that exhibit different regional and subcellular distributions and distinct pharmacological properties. Dysfunctional alterations of GABAA receptors are associated with various neuropsychiatric disorders. Short- and long-term plastic changes in GABAA receptors can be induced by the activation of different intracellular signaling pathways that are triggered, under physiological and pathological conditions, by calcium entering through voltage-gated calcium channels. This review discusses several mechanisms of regulation of GABAA receptor function that result from the activation of L-type voltage gated calcium channels. Calcium influx via these channels activates different signaling cascades that lead to changes in GABAA receptor transcription, phosphorylation, trafficking, and synaptic clustering, thus regulating the inhibitory synaptic strength. These plastic mechanisms regulate the interplay of synaptic excitation and inhibition that is crucial for the normal function of neuronal circuits.
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15
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Nakamura Y, Morrow DH, Nathanson AJ, Henley JM, Wilkinson KA, Moss SJ. Phosphorylation on Ser-359 of the α2 subunit in GABA type A receptors down-regulates their density at inhibitory synapses. J Biol Chem 2020; 295:12330-12342. [PMID: 32620552 PMCID: PMC7458806 DOI: 10.1074/jbc.ra120.014303] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/25/2020] [Indexed: 11/06/2022] Open
Abstract
GABA type A receptors (GABAARs) mediate fast synaptic inhibition and are trafficked to functionally diverse synapses. However, the precise molecular mechanisms that regulate the synaptic targeting of these receptors are unclear. Whereas it has been previously shown that phosphorylation events in α4, β, and γ subunits of GABAARs govern their function and trafficking, phosphorylation of other subunits has not yet been demonstrated. Here, we show that the α2 subunit of GABAARs is phosphorylated at Ser-359 and enables dynamic regulation of GABAAR binding to the scaffolding proteins gephyrin and collybistin. We initially identified Ser-359 phosphorylation by MS analysis, and additional experiments revealed that it is regulated by the activities of cAMP-dependent protein kinase (PKA) and the protein phosphatase 1 (PP1) and/or PP2A. GST-based pulldowns and coimmunoprecipitation experiments demonstrate preferential binding of both gephyrin and collybistin to WT and an S359A phosphonull variant, but not to an S359D phosphomimetic variant. Furthermore, the decreased capacity of the α2 S359D variant to bind collybistin and gephyrin decreased the density of synaptic α2-containing GABAAR clusters and caused an absence of α2 enrichment in the axon initial segment. These results suggest that PKA-mediated phosphorylation and PP1/PP2A-dependent dephosphorylation of the α2 subunit play a role in the dynamic regulation of GABAAR accumulation at inhibitory synapses, thereby regulating the strength of synaptic inhibition. The MS data have been deposited to ProteomeXchange, with the data set identifier PXD019597.
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Affiliation(s)
- Yasuko Nakamura
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Danielle H. Morrow
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA
| | - Anna J. Nathanson
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA
| | - Jeremy M. Henley
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Kevin A. Wilkinson
- School of Biochemistry, Centre for Synaptic Plasticity, University of Bristol, Bristol, United Kingdom
| | - Stephen J. Moss
- Department of Neuroscience, Tufts University, School of Medicine, Boston, Massachusetts, USA,Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom,For correspondence: S. J. Moss,
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16
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Blednov YA, Borghese CM, Dugan MP, Pradhan S, Thodati TM, Kichili NR, Harris RA, Messing RO. Apremilast regulates acute effects of ethanol and other GABAergic drugs via protein kinase A-dependent signaling. Neuropharmacology 2020; 178:108220. [PMID: 32736086 DOI: 10.1016/j.neuropharm.2020.108220] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Revised: 06/15/2020] [Accepted: 06/19/2020] [Indexed: 12/19/2022]
Abstract
Phosphodiesterase type 4 (PDE4) inhibitors prevent hydrolysis of cyclic adenosine monophosphate and increase protein kinase A (PKA)-mediated phosphorylation. PDE4 inhibitors also regulate responses to ethanol and GABAergic drugs. We investigated mechanisms by which the PDE4 inhibitor, apremilast, regulates acute effects of ethanol and GABAergic drugs in male and female mice. Apremilast prolonged the sedative-hypnotic effects of gaboxadol, zolpidem, and propofol but did not alter etomidate effects, and unexpectedly shortened the sedative-hypnotic effects of diazepam. Apremilast prolonged rotarod ataxia induced by zolpidem, propofol, and loreclezole, shortened recovery from diazepam, but had no effect on ataxia induced by gaboxadol or etomidate. The PKA inhibitor H-89 blocked apremilast's ability to prolong the sedative-hypnotic effects of ethanol, gaboxadol, and propofol and to prolong ethanol- and propofol-induced ataxia. H-89 also blocked apremilast's ability to shorten the sedative-hypnotic and ataxic effects of diazepam. The β1-specific antagonist, salicylidene salicylhydrazide (SCS), produced faster recovery from ethanol- and diazepam-induced ataxia, but did not alter propofol- or etomidate-induced ataxia. SCS shortened the sedative-hypnotic effects of ethanol and diazepam but not of propofol. In Xenopus oocytes, a phosphomimetic (aspartate) mutation at the PKA phosphorylation site in β1 subunits decreased the maximal GABA current in receptors containing α1 or α3, but not α2 subunits. In contrast, phosphomimetic mutations at PKA sites in β3 subunits increased the maximal GABA current in receptors containing α1 or α2, but not α3 subunits. The GABA potency and allosteric modulation by ethanol, propofol, etomidate, zolpidem, flunitrazepam, or diazepam were not altered by these mutations. We propose a model whereby apremilast increases PKA-mediated phosphorylation of β1-and β3-containing GABAA receptors and selectively alters acute tolerance to ethanol and GABAergic drugs.
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Affiliation(s)
- Yuri A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Cecilia M Borghese
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Michael P Dugan
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Swetak Pradhan
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Thanvi M Thodati
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Nikhita R Kichili
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Robert O Messing
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, 78712, USA; Department of Neuroscience, The University of Texas at Austin, Austin, TX, 78712, USA; Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, 78712, USA.
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17
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Vaaga CE, Brown ST, Raman IM. Cerebellar modulation of synaptic input to freezing-related neurons in the periaqueductal gray. eLife 2020; 9:e54302. [PMID: 32207681 PMCID: PMC7124251 DOI: 10.7554/elife.54302] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/24/2020] [Indexed: 01/23/2023] Open
Abstract
Innate defensive behaviors, such as freezing, are adaptive for avoiding predation. Freezing-related midbrain regions project to the cerebellum, which is known to regulate rapid sensorimotor integration, raising the question of cerebellar contributions to freezing. Here, we find that neurons of the mouse medial (fastigial) cerebellar nuclei (mCbN), which fire spontaneously with wide dynamic ranges, send glutamatergic projections to the ventrolateral periaqueductal gray (vlPAG), which contains diverse cell types. In freely moving mice, optogenetically stimulating glutamatergic vlPAG neurons that express Chx10 reliably induces freezing. In vlPAG slices, mCbN terminals excite ~20% of neurons positive for Chx10 or GAD2 and ~70% of dopaminergic TH-positive neurons. Stimulating either mCbN afferents or TH neurons augments IPSCs and suppresses EPSCs in Chx10 neurons by activating postsynaptic D2 receptors. The results suggest that mCbN activity regulates dopaminergic modulation of the vlPAG, favoring inhibition of Chx10 neurons. Suppression of cerebellar output may therefore facilitate freezing.
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Affiliation(s)
- Christopher E Vaaga
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Spencer T Brown
- Department of Neurobiology, Northwestern University, Evanston, United States
| | - Indira M Raman
- Department of Neurobiology, Northwestern University, Evanston, United States
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18
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Kfir A, Awasthi R, Ghosh S, Kundu S, Paul B, Lamprecht R, Barkai E. A Cellular Mechanism of Learning-Induced Enhancement of Synaptic Inhibition: PKC-Dependent Upregulation of KCC2 Activation. Sci Rep 2020; 10:962. [PMID: 31969605 PMCID: PMC6976593 DOI: 10.1038/s41598-020-57626-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Accepted: 12/18/2019] [Indexed: 01/23/2023] Open
Abstract
Long-term memory of complex olfactory learning is expressed by wide spread enhancement in excitatory and inhibitory synaptic transmission onto piriform cortex pyramidal neurons. A particularly interesting modification in synaptic inhibition is the hyperpolarization of the reversal potential of the fast post synaptic inhibitory potential (fIPSP). Here we study the mechanism underlying the maintenance of such a shift in the fIPSP. Blocking of the neuronal specific K+-Cl- co-transporter (KCC2) in neurons of trained rats significantly depolarized the averaged fIPSP reversal potential of the spontaneous miniature inhibitory post synaptic currents (mIPSCs), to the averaged pre-training level. A similar effect was obtained by blocking PKC, which was previously shown to upregulate KCC2. Accordingly, the level of PKC-dependent phosphorylation of KCC2, at the serine 940 site, was significantly increased after learning. In contrast, blocking two other key second messenger systems CaMKII and PKA, which have no phosphorylation sites on KCC2, had no effect on the fIPSP reversal potential. Importantly, the PKC inhibitor also reduced the averaged amplitude of the spontaneous miniature excitatory synaptic currents (mEPSCs) in neurons of trained rats only, to the pre-training level. We conclude that learning-induced hyper-polarization of the fIPSP reversal potential is mediated by PKC-dependent increase of KCC2 phosphorylation.
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Affiliation(s)
- Adi Kfir
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Richa Awasthi
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Sourav Ghosh
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Sankhanava Kundu
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Blesson Paul
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Raphael Lamprecht
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Edi Barkai
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
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19
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Mechanisms of GABA B receptor enhancement of extrasynaptic GABA A receptor currents in cerebellar granule cells. Sci Rep 2019; 9:16683. [PMID: 31723152 PMCID: PMC6853962 DOI: 10.1038/s41598-019-53087-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/26/2019] [Indexed: 12/31/2022] Open
Abstract
Many neurons, including cerebellar granule cells, exhibit a tonic GABA current mediated by extrasynaptic GABAA receptors. This current is a critical regulator of firing and the target of many clinically relevant compounds. Using a combination of patch clamp electrophysiology and photolytic uncaging of RuBi-GABA we show that GABAB receptors are tonically active and enhance extrasynaptic GABAA receptor currents in cerebellar granule cells. This enhancement is not associated with meaningful changes in GABAA receptor potency, mean channel open-time, open probability, or single-channel current. However, there was a significant (~40%) decrease in the number of channels participating in the GABA uncaging current and an increase in receptor desensitization. Furthermore, we find that adenylate cyclase, PKA, CaMKII, and release of Ca2+ from intracellular stores are necessary for modulation of GABAA receptors. Overall, this work reveals crosstalk between postsynaptic GABAA and GABAB receptors and identifies the signaling pathways and mechanisms involved.
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20
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cAMP-EPAC-Dependent Regulation of Gephyrin Phosphorylation and GABA AR Trapping at Inhibitory Synapses. iScience 2019; 22:453-465. [PMID: 31835170 PMCID: PMC6926171 DOI: 10.1016/j.isci.2019.11.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/11/2019] [Accepted: 11/05/2019] [Indexed: 01/13/2023] Open
Abstract
GABAA and glycine receptors are thought to compete for gephyrin-binding sites at mixed inhibitory synapses. Changes in the occupancy of one receptor type are therefore expected to have opposite effects on the clustering of the other receptors. This does not explain, however, whether different receptors can be regulated independently from one another. Here we show that cAMP-dependent signaling reduces gephyrin phosphorylation at residue S270 in spinal cord neurons. Although no ultrastructural changes of the synaptic scaffold were detected using super-resolution imaging, gephyrin de-phosphorylation was associated with a selective increase in GABAAR diffusion and the loss of the receptors from synapses. As opposed to the PKA-dependent dispersal of α3-containing GlyRs, the regulation of gephyrin phosphorylation and GABAAR dynamics acts via non-canonical EPAC signaling. Subtype-specific changes in receptor mobility can thus differentially contribute to changes in inhibitory synaptic strength, such as the disinhibition of spinal cord neurons during inflammatory processes.
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21
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Sakimoto Y, Kida H, Mitsushima D. Temporal dynamics of learning-promoted synaptic diversity in CA1 pyramidal neurons. FASEB J 2019; 33:14382-14393. [PMID: 31689120 PMCID: PMC6894079 DOI: 10.1096/fj.201801893rrr] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Although contextual learning requires plasticity at both excitatory and inhibitory (E/I) synapses in cornu ammonis 1 (CA1) neurons, the temporal dynamics across the neuronal population are poorly understood. Using an inhibitory avoidance task, we analyzed the dynamic changes in learning-induced E/I synaptic plasticity. The training strengthened GABAA receptor–mediated synapses within 1 min, peaked at 10 min, and lasted for over 60 min. The intracellular loop (Ser408−409) of GABAA receptor β3 subunit was also phosphorylated within 1 min of training. As the results of strengthening of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor–mediated synapses, CA1 pyramidal neurons exhibited broad diversity of E/I synaptic currents within 5 min. Moreover, presynaptic glutamate release probability at basal dendrites also increased within 5 min. To further quantify the diversified E/I synaptic currents, we calculated self-entropy (bit) for individual neurons. The neurons showed individual levels of the parameter, which rapidly increased within 1 min of training and maintained for over 60 min. These results suggest that learning-induced synaptic plasticity is critical immediately following encoding rather than during the retrieval phase of the learning. Understanding the temporal dynamics along with the quantification of synaptic diversity would be necessary to identify a failure point for learning-promoted plasticity in cognitive disorders.—Sakimoto, Y., Kida, H., Mitsushima, D. Temporal dynamics of learning-promoted synaptic diversity in CA1 pyramidal neurons.
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Affiliation(s)
- Yuya Sakimoto
- Department of Physiology, Graduate School of Medicine, Yamaguchi University, Ube, Japan
| | - Hiroyuki Kida
- Department of Physiology, Graduate School of Medicine, Yamaguchi University, Ube, Japan
| | - Dai Mitsushima
- Department of Physiology, Graduate School of Medicine, Yamaguchi University, Ube, Japan.,The Research Institute for Time Studies, Yamaguchi University, Yamaguchi, Japan
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22
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Mele M, Costa RO, Duarte CB. Alterations in GABA A-Receptor Trafficking and Synaptic Dysfunction in Brain Disorders. Front Cell Neurosci 2019; 13:77. [PMID: 30899215 PMCID: PMC6416223 DOI: 10.3389/fncel.2019.00077] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/15/2019] [Indexed: 12/12/2022] Open
Abstract
GABAA receptors (GABAAR) are the major players in fast inhibitory neurotransmission in the central nervous system (CNS). Regulation of GABAAR trafficking and the control of their surface expression play important roles in the modulation of the strength of synaptic inhibition. Different pieces of evidence show that alterations in the surface distribution of GABAAR and dysregulation of their turnover impair the activity of inhibitory synapses. A diminished efficacy of inhibitory neurotransmission affects the excitatory/inhibitory balance and is a common feature of various disorders of the CNS characterized by an increased excitability of neuronal networks. The synaptic pool of GABAAR is mainly controlled through regulation of internalization, recycling and lateral diffusion of the receptors. Under physiological condition these mechanisms are finely coordinated to define the strength of GABAergic synapses. In this review article, we focus on the alteration in GABAAR trafficking with an impact on the function of inhibitory synapses in various disorders of the CNS. In particular we discuss how similar molecular mechanisms affecting the synaptic distribution of GABAAR and consequently the excitatory/inhibitory balance may be associated with a wide diversity of pathologies of the CNS, from psychiatric disorders to acute alterations leading to neuronal death. A better understanding of the cellular and molecular mechanisms that contribute to the impairment of GABAergic neurotransmission in these disorders, in particular the alterations in GABAAR trafficking and surface distribution, may lead to the identification of new pharmacological targets and to the development of novel therapeutic strategies.
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Affiliation(s)
- Miranda Mele
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Rui O Costa
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Institute for Interdisciplinary Research, University of Coimbra, Coimbra, Portugal
| | - Carlos B Duarte
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.,Department of Life Sciences, University of Coimbra, Coimbra, Portugal
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23
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Long-term application of cannabinoids leads to dissociation between changes in cAMP and modulation of GABA A receptors of mouse trigeminal sensory neurons. Neurochem Int 2019; 126:74-85. [PMID: 30633953 DOI: 10.1016/j.neuint.2019.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/20/2018] [Accepted: 01/07/2019] [Indexed: 12/11/2022]
Abstract
Antinociception caused by cannabinoids may have a partial peripheral origin in addition to its central site of action. In fact, we have observed that anandamide selectively and reversibly inhibits GABAA receptors of putative nociceptive neurons of mouse trigeminal sensory ganglia via CB1 receptor activation to inhibit adenylyl cyclase and decrease cAMP with downstream posttranslational alterations. Since cannabinoids are often used chronically, we studied changes in cAMP levels and GABA-mediated currents of trigeminal neurons following 24 h application of anandamide (0.5 μM) or the synthetic cannabinoid WIN 55,212-2 (5 μM). With this protocol GABA responses were similar to control despite persistent fall in cAMP levels. Inhibition by WIN 55,212-2 of GABA effects recovered after 30 min washout and was not associated with changes in CB1 receptor expression, indicating lack of CB1 receptor inactivation and transient loss of negative coupling between CB1 receptors and GABAA receptors. The phosphodiesterase inhibitor rolipram (100 μM; 24 h) enhanced cAMP levels and GABA-mediated currents, suggesting GABAA receptors were sensitive to persistent upregulation via cAMP. While the adenylyl cyclase activator forskolin (1-20 μM) facilitated cAMP levels and GABA currents following 30 min application, this action was lost after 24 h in line with the drug limited lifespan. The PKA inhibitor PKI 14-22 (10 μM) increased cAMP without changing GABA currents. These data indicate that modulation of GABAA receptors by intracellular cAMP could be lost following persistent application of cannabinoids. Thus, these observations provide an insight into the waning antinociceptive effects of these compounds.
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24
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Szodorai E, Bampali K, Romanov RA, Kasper S, Hökfelt T, Ernst M, Lubec G, Harkany T. Diversity matters: combinatorial information coding by GABA A receptor subunits during spatial learning and its allosteric modulation. Cell Signal 2018; 50:142-159. [DOI: 10.1016/j.cellsig.2018.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/08/2018] [Accepted: 07/09/2018] [Indexed: 01/11/2023]
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25
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Lorenz-Guertin JM, Bambino MJ, Jacob TC. γ2 GABA AR Trafficking and the Consequences of Human Genetic Variation. Front Cell Neurosci 2018; 12:265. [PMID: 30190672 PMCID: PMC6116786 DOI: 10.3389/fncel.2018.00265] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 08/02/2018] [Indexed: 11/13/2022] Open
Abstract
GABA type A receptors (GABAARs) mediate the majority of fast inhibitory neurotransmission in the central nervous system (CNS). Most prevalent as heteropentamers composed of two α, two β, and a γ2 subunit, these ligand-gated ionotropic chloride channels are capable of extensive genetic diversity (α1-6, β1-3, γ1-3, δ, 𝜀, 𝜃, π, ρ1-3). Part of this selective GABAAR assembly arises from the critical role for γ2 in maintaining synaptic receptor localization and function. Accordingly, mutations in this subunit account for over half of the known epilepsy-associated genetic anomalies identified in GABAARs. Fundamental structure-function studies and cellular pathology investigations have revealed dynamic GABAAR trafficking and synaptic scaffolding as critical regulators of GABAergic inhibition. Here, we introduce in vitro and in vivo findings regarding the specific role of the γ2 subunit in receptor trafficking. We then examine γ2 subunit human genetic variation and assess disease related phenotypes and the potential role of altered GABAAR trafficking. Finally, we discuss new-age imaging techniques and their potential to provide novel insight into critical regulatory mechanisms of GABAAR function.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Matthew J Bambino
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
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26
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Brewer AL, Liu S, Buhler AV, Shirachi DY, Quock RM. Role of spinal GABA receptors in the acute antinociceptive response of mice to hyperbaric oxygen. Brain Res 2018; 1699:107-116. [PMID: 30077648 DOI: 10.1016/j.brainres.2018.08.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/15/2018] [Accepted: 08/02/2018] [Indexed: 02/01/2023]
Abstract
New pain treatments are in demand due to the pervasive nature of pain conditions. Hyperbaric oxygen (HBO2) has shown potential in treating pain in both clinical and preclinical settings, although the mechanism of this effect is still unknown. The aim of this study was to investigate whether the major inhibitory neurotransmitter γ-aminobutyric acid (GABA) is involved in HBO2-induced antinociception in the central nervous system (CNS). To accomplish this goal, pharmacological interactions between GABA drugs and HBO2 were investigated using the behavioral acetic acid abdominal constriction test. Western blotting was used to quantify protein changes that might occur as a result of the interactions. GABAA but not GABAB receptor antagonists dose-dependently reduced HBO2 antinociception, while antagonism of the GABA reuptake transporter enhanced this effect. Western blot results showed an interaction between the pain stimulus and HBO2 on expression of the phosphorylated β3 subunit of the GABAA receptor at S408/409 in homogenates of the lumbar but not thoracic spinal cord. A significant interaction was also found in neuronal nitric oxide synthase (nNOS) expression in the lumbar but not thoracic spinal cord. These findings support the notion that GABA may be involved in HBO2-induced antinociception at the GABAA receptor but indicate that more study will be needed to understand the intricacies of this interaction.
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Affiliation(s)
- Abigail L Brewer
- Department of Psychology, Washington State University, Pullman, WA 99164, USA
| | - Shulin Liu
- Department of Aviation Medicine, Naval Medicine Research Institute, Second Military Medical University, Shanghai 200433, China
| | - Amber V Buhler
- School of Pharmacy, Pacific University Oregon, Hillsboro, OR 97123, USA
| | - Donald Y Shirachi
- Department of Physiology and Pharmacology, Thomas J. Long School of Pharmacy and Health Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Raymond M Quock
- Department of Psychology, Washington State University, Pullman, WA 99164, USA; Translational Addiction Research Center, Washington State University, Pullman, WA 99164, USA.
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27
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Chuang SH, Reddy DS. 3 β-Methyl-Neurosteroid Analogs Are Preferential Positive Allosteric Modulators and Direct Activators of Extrasynaptic δ-Subunit γ-Aminobutyric Acid Type A Receptors in the Hippocampus Dentate Gyrus Subfield. J Pharmacol Exp Ther 2018; 365:583-601. [PMID: 29602830 DOI: 10.1124/jpet.117.246660] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/28/2018] [Indexed: 02/06/2023] Open
Abstract
Neurosteroids are powerful modulators of γ-aminobutyric acid (GABA)-A receptors. Ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one, GX) and synthetic analogs of the neurosteroid allopregnanolone (AP) are designed to treat epilepsy and related conditions. However, their precise mechanism of action in native neurons remains unclear. Here, we sought to determine the mode of action of GX and its analogs at GABA-A receptors in native hippocampal neurons by analyzing extrasynaptic receptor-mediated tonic currents and synaptic receptor-mediated phasic currents. Concentration-response profiles of GX were determined in two cell types: δ-containing dentate gyrus granule cells (DGGCs) and γ2-containing CA1 pyramidal cells (CA1PCs). GX produced significantly greater potentiation of the GABA-A receptor-activated chloride currents in DGGCs (500%) than CA1PCs (200%). In the absence of GABA, GX evoked 2-fold greater inward currents in DGGCs than CA1PCs, which were 2-fold greater than AP within DGGCs. In hippocampus slices, GX potentiated and directly activated tonic currents in DGGCs. These responses were significantly diminished in DGGCs from δ-subunit knockout (δKO) mice, confirming GX's selectivity for δGABA-A receptors. Like AP, GX potentiation of tonic currents was prevented by protein kinase C inhibition. Furthermore, GX's protection against hippocampus-kindled seizures was significantly diminished in δKO mice. GX analogs exhibited greater potency and efficacy than GX on δGABA-A receptor-mediated tonic inhibition. In summary, these results provide strong evidence that GX and its analogs are preferential allosteric modulators and direct activators of extrasynaptic δGABA-A receptors regulating network inhibition and seizures in the dentate gyrus. Therefore, these findings provide a mechanistic rationale for the clinical use of synthetic neurosteroids in epilepsy and seizure disorders.
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Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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28
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Sharonova IN, Bukanova YV, Myasoedov NF, Skrebitskii VG. Modulation of GABA- and Glycine-Activated Ionic Currents with Semax in Isolated Cerebral Neurons. Bull Exp Biol Med 2018; 164:612-616. [PMID: 29577196 DOI: 10.1007/s10517-018-4043-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Indexed: 12/01/2022]
Abstract
The concentration-clamp experiments with neurons isolated from the rat brain showed that nootropic and neuroprotective drug Semax added to perfusion solution at concentration of 1 μM augmented the amplitude of GABA-activated ionic currents in cerebellum Purkinje cells by 147±13%. In addition, Semax in perfusion solution (0.1 and 1 μM) diminished the amplitude of glycine-activated chloride currents in hippocampal pyramidal neurons down to 68 and 43% control level, respectively. Both potentiating and inhibitory effects developed slowly, and they were poorly reversible, which indicated a probable implication of second messengers in the observed phenomena. Semax accelerated the falling edge of glycine-activated current both after a short-term co-application with agonist and after addition of this peptide into perfusion solution.
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Affiliation(s)
| | | | - N F Myasoedov
- Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russia
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29
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Lorenz-Guertin JM, Jacob TC. GABA type a receptor trafficking and the architecture of synaptic inhibition. Dev Neurobiol 2018; 78:238-270. [PMID: 28901728 PMCID: PMC6589839 DOI: 10.1002/dneu.22536] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/08/2017] [Accepted: 09/08/2017] [Indexed: 12/21/2022]
Abstract
Ubiquitous expression of GABA type A receptors (GABAA R) in the central nervous system establishes their central role in coordinating most aspects of neural function and development. Dysregulation of GABAergic neurotransmission manifests in a number of human health disorders and conditions that in certain cases can be alleviated by drugs targeting these receptors. Precise changes in the quantity or activity of GABAA Rs localized at the cell surface and at GABAergic postsynaptic sites directly impact the strength of inhibition. The molecular mechanisms constituting receptor trafficking to and from these compartments therefore dictate the efficacy of GABAA R function. Here we review the current understanding of how GABAA Rs traffic through biogenesis, plasma membrane transport, and degradation. Emphasis is placed on discussing novel GABAergic synaptic proteins, receptor and scaffolding post-translational modifications, activity-dependent changes in GABAA R confinement, and neuropeptide and neurosteroid mediated changes. We further highlight modern techniques currently advancing the knowledge of GABAA R trafficking and clinically relevant neurodevelopmental diseases connected to GABAergic dysfunction. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 78: 238-270, 2018.
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Affiliation(s)
- Joshua M Lorenz-Guertin
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
| | - Tija C Jacob
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, 15261
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30
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Ghosh S, Reuveni I, Zidan S, Lamprecht R, Barkai E. Learning-induced modulation of the effect of endocannabinoids on inhibitory synaptic transmission. J Neurophysiol 2018; 119:752-760. [DOI: 10.1152/jn.00623.2017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Endocannabinoids are key modulators that regulate central brain functions and behaviors, including learning and memory. At the cellular and molecular levels, endocannabinoids are potent modulators of excitatory and inhibitory synaptic function. Most effects of cannabinoids are thought to be mediated via G protein-coupled cannabinoid receptors. In particular, cannabinoids released from postsynaptic neurons are suggested to act as retrograde messengers, activating presynaptic type-1 cannabinoid receptors (CB1Rs), thereby inducing suppression of synaptic release. Another central mechanism of cannabinoid-induced action requires activation of astroglial CB1Rs. CB1Rs are also implicated in self-modulation of cortical neurons. Rats that are trained in a particularly difficult olfactory-discrimination task show a dramatic increased ability to acquire memories of new odors. The memory of the acquired high-skill acquisition, termed “rule learning” or “learning set,” lasts for many months. Using this behavioral paradigm, we show a novel function of action for CB1Rs, supporting long-term memory by maintaining persistent enhancement of inhibitory synaptic transmission. Long-lasting enhancement of inhibitory synaptic transmission is blocked by a CB1R inverse agonist. This effect is mediated by a novel purely postsynaptic mechanism, obtained by enhancing the single GABAA channel conductance that is PKA dependent. The significant role that CB1R has in maintaining learning-induced long-term strengthening of synaptic inhibition suggests that endocannabinoids have a key role in maintaining long-term memory by enhancing synaptic inhibition. NEW & NOTEWORTHY In this study we show a novel function and mechanism of action for cannabinoids in neurons, mediated by activation of type-1 cannabinoid receptors, supporting long-term memory by maintaining persistent enhancement of inhibitory synaptic transmission on excitatory neurons. This effect is mediated by a novel purely postsynaptic mechanism, obtained by enhancing the single GABAA channel conductance that is PKA dependent. Thus we report for the first time that endocannabinoids have a key role maintaining learning-induced synaptic modification.
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Affiliation(s)
- Sourav Ghosh
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Iris Reuveni
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Samaa Zidan
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Raphael Lamprecht
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Edi Barkai
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
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31
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Martinello K, Sciaccaluga M, Morace R, Mascia A, Arcella A, Esposito V, Fucile S. Loss of constitutive functional γ-aminobutyric acid type A-B receptor crosstalk in layer 5 pyramidal neurons of human epileptic temporal cortex. Epilepsia 2017; 59:449-459. [PMID: 29283181 DOI: 10.1111/epi.13991] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/05/2017] [Indexed: 12/24/2022]
Abstract
OBJECTIVE γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in adult central nervous system, and profound alterations of GABA receptor functions are linked to temporal lobe epilepsy (TLE). Here we describe the functional relationships between GABA receptors type B (GABAB R) and type A (GABAA R) in human temporal cortex and how TLE affects this aspect of GABAergic signaling. METHODS Miniature inhibitory postsynaptic currents (mIPSCs) were recorded by patch-clamp techniques from human L5 pyramidal neurons in slices from temporal cortex tissue obtained from surgery. RESULTS We describe a constitutive functional crosstalk between GABAB Rs and GABAA Rs in human temporal layer 5 pyramidal neurons, which is lost in epileptic tissues. The activation of GABAB Rs by baclofen, in addition to the expected reduction of mIPSC frequency, produced, in cortex of nonepileptic patients, the prolongation of mIPSC rise and decay times, thus increasing the inhibitory net charge associated with a single synaptic event. Block of K+ channels did not prevent the increase of decay time and charge. Protein kinase A (PKA) blocker KT5720 and pertussis toxin inhibited the action of baclofen, whereas 8Br-cAMP mimicked the GABAB R action. The same GABAB R-mediated modulation of GABAA Rs was observed in pyramidal neurons of rat temporal cortex, with both PKA and PKC involved in the process. In cortices from TLE patients and epileptic rats, baclofen lost its ability to modulate mIPSCs. SIGNIFICANCE Our results highlight the association of TLE with functional changes of GABAergic signaling that may be related to seizure propagation, and suggest that the selective activation of a definite subset of nonpresynaptic GABAB Rs may be therapeutically useful in TLE.
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Affiliation(s)
| | | | | | | | | | - Vincenzo Esposito
- Neuromed IRCCS, Pozzilli, Italy.,Department of Neurosurgery, Sapienza University of Rome, Rome, Italy
| | - Sergio Fucile
- Neuromed IRCCS, Pozzilli, Italy.,Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy
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32
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Shen W, Nan C, Nelson PT, Ripps H, Slaughter MM. GABA B receptor attenuation of GABA A currents in neurons of the mammalian central nervous system. Physiol Rep 2017; 5:5/6/e13129. [PMID: 28348006 PMCID: PMC5371550 DOI: 10.14814/phy2.13129] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 11/18/2016] [Indexed: 11/24/2022] Open
Abstract
Ionotropic receptors are tightly regulated by second messenger systems and are often present along with their metabotropic counterparts on a neuron's plasma membrane. This leads to the hypothesis that the two receptor subtypes can interact, and indeed this has been observed in excitatory glutamate and inhibitory GABA receptors. In both systems the metabotropic pathway augments the ionotropic receptor response. However, we have found that the metabotropic GABAB receptor can suppress the ionotropic GABAA receptor current, in both the in vitro mouse retina and in human amygdala membrane fractions. Expression of amygdala membrane microdomains in Xenopus oocytes by microtransplantation produced functional ionotropic and metabotropic GABA receptors. Most GABAA receptors had properties of α‐subunit containing receptors, with ~5% having ρ‐subunit properties. Only GABAA receptors with α‐subunit‐like properties were regulated by GABAB receptors. In mouse retinal ganglion cells, where only α‐subunit‐containing GABAA receptors are expressed, GABAB receptors suppressed GABAA receptor currents. This suppression was blocked by GABAB receptor antagonists, G‐protein inhibitors, and GABAB receptor antibodies. Based on the kinetic differences between metabotropic and ionotropic receptors, their interaction would suppress repeated, rapid GABAergic inhibition.
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Affiliation(s)
- Wen Shen
- Department of Biomedical Science, Charles E. Schmidt College of Medicine Florida Atlantic University, Boca Raton, Florida
| | - Changlong Nan
- Department of Biomedical Science, Charles E. Schmidt College of Medicine Florida Atlantic University, Boca Raton, Florida
| | - Peter T Nelson
- Division of Neuropathology, Department of Pathology, University of Kentucky, Lexington, Kentucky.,Sanders-Brown Centre on Aging, University of Kentucky, Lexington, Kentucky
| | - Harris Ripps
- Department of Ophthalmology and Visual Sciences, University of Illinois College of Medicine, Chicago, Illinois.,Whitman Investigator, Marine Biological Laboratory, Woods Hole, Massachusetts
| | - Malcolm M Slaughter
- Department of Physiology and Biophysics, State University of New York at Buffalo, Buffalo, New York
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33
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Chuang SH, Reddy DS. Genetic and Molecular Regulation of Extrasynaptic GABA-A Receptors in the Brain: Therapeutic Insights for Epilepsy. J Pharmacol Exp Ther 2017; 364:180-197. [PMID: 29142081 DOI: 10.1124/jpet.117.244673] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/13/2017] [Indexed: 12/18/2022] Open
Abstract
GABA-A receptors play a pivotal role in many brain diseases. Epilepsy is caused by acquired conditions and genetic defects in GABA receptor channels regulating neuronal excitability in the brain. The latter is referred to as GABA channelopathies. In the last two decades, major advances have been made in the genetics of epilepsy. The presence of specific GABAergic genetic abnormalities leading to some of the classic epileptic syndromes has been identified. Advances in molecular cloning and recombinant systems have helped characterize mutations in GABA-A receptor subunit genes in clinical neurology. GABA-A receptors are the prime targets for neurosteroids (NSs). However, GABA-A receptors are not static but undergo rapid changes in their number or composition in response to the neuroendocrine milieu. This review describes the recent advances in the genetic and neuroendocrine control of extrasynaptic and synaptic GABA-A receptors in epilepsy and its impact on neurologic conditions. It highlights the current knowledge of GABA genetics in epilepsy, with an emphasis on the neuroendocrine regulation of extrasynaptic GABA-A receptors in network excitability and seizure susceptibility. Recent advances in molecular regulation of extrasynaptic GABA-A receptor-mediated tonic inhibition are providing unique new therapeutic approaches for epilepsy, status epilepticus, and certain brain disorders. The discovery of an extrasynaptic molecular mechanism represents a milestone for developing novel therapies such as NS replacement therapy for catamenial epilepsy.
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Affiliation(s)
- Shu-Hui Chuang
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
| | - Doodipala Samba Reddy
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, Bryan, Texas
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34
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Vien TN, Moss SJ, Davies PA. Regulating the Efficacy of Inhibition Through Trafficking of γ-Aminobutyric Acid Type A Receptors. Anesth Analg 2017; 123:1220-1227. [PMID: 27285004 DOI: 10.1213/ane.0000000000001349] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Trafficking of anesthetic-sensitive receptors within the plasma membrane, or from one cellular component to another, occurs continuously. Changes in receptor trafficking have implications in altering anesthetic sensitivity. γ-Aminobutyric acid type A receptors (GABAARs) are anion-permeable ion channels and are the major class of receptor in the adult mammalian central nervous system that mediates inhibition. GABAergic signaling allows for precise synchronized firing of action potentials within brain circuits that is critical for cognition, behavior, and consciousness. This precision depends upon tightly controlled trafficking of GABAARs into the membrane. General anesthetics bind to and allosterically enhance GABAARs by prolonging the open state of the receptor and thereby altering neuronal and brain circuit activity. Subunit composition and GABAAR localization strongly influence anesthetic end points; therefore, changes in GABAAR trafficking could have significant consequences to anesthetic sensitivity. GABAARs are not static membrane structures but are in a constant state of flux between extrasynaptic and synaptic locations and are continually endocytosed and recycled from and to the membrane. Neuronal activity, posttranslational modifications, and some naturally occurring and synthetic compounds can influence the expression and trafficking of GABAARs. In this article, we review GABAARs, their trafficking, and how phosphorylation of GABAAR subunits can influence the surface expression and function of the receptor. Ultimately, alterations of GABAAR trafficking could modify anesthetic end points, both unintentionally through pathologic processes but potentially as a therapeutic target to adjust anesthetic-sensitive GABAARs.
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Affiliation(s)
- Thuy N Vien
- From the *Department of Neuroscience, Tufts University School of Medicine, Sackler School of Graduate Biomedical Sciences, Boston, Massachusetts; and †Department of Neuroscience, Tufts University School of Medicine, Boston, Massachusetts
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35
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Rozov AV, Valiullina FF, Bolshakov AP. Mechanisms of long-term plasticity of hippocampal GABAergic synapses. BIOCHEMISTRY (MOSCOW) 2017; 82:257-263. [DOI: 10.1134/s0006297917030038] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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36
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Mele M, Leal G, Duarte CB. Role of GABAAR trafficking in the plasticity of inhibitory synapses. J Neurochem 2016; 139:997-1018. [DOI: 10.1111/jnc.13742] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/12/2016] [Accepted: 07/13/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Miranda Mele
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Graciano Leal
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
| | - Carlos B. Duarte
- Center for Neuroscience and Cell Biology; University of Coimbra; Coimbra Portugal
- Department of Life Sciences; University of Coimbra; Coimbra Portugal
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37
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Jappy D, Valiullina F, Draguhn A, Rozov A. GABABR-Dependent Long-Term Depression at Hippocampal Synapses between CB1-Positive Interneurons and CA1 Pyramidal Cells. Front Cell Neurosci 2016; 10:4. [PMID: 26858602 PMCID: PMC4729905 DOI: 10.3389/fncel.2016.00004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/04/2016] [Indexed: 12/31/2022] Open
Abstract
Activity induced long lasting modifications of synaptic efficacy have been extensively studied in excitatory synapses, however, long term plasticity is also a property of inhibitory synapses. Inhibitory neurons in the hippocampal CA1 region can be subdivided according to the compartment they target on the pyramidal cell. Some interneurons preferentially innervate the perisomatic area and axon hillock of the pyramidal cells while others preferentially target dendritic branches and spines. Another characteristic feature allowing functional classification of interneurons is cell type specific expression of different neurochemical markers and receptors. In the hippocampal CA1 region, nearly 90% of the interneurons expressing cannabinoid type 1 receptors (CB1R) also express cholecystokinin (CCK). Therefore, the functional presence of CB1 receptors can be used for identification of the inhibitory input from CCK positive (CCK+) interneurons to CA1 pyramidal cells. The goal of this study was to explore the nature of long term plasticity at the synapses between interneurons expressing CB1Rs (putative CCK+) and pyramidal neurons in the CA1 region of the hippocampus in vitro. We found that theta burst stimulation triggered robust long-term depression (LTD) at this synapse. The locus of LTD induction was postsynaptic and required activation of GABAB receptors. We also showed that LTD at this synaptic connection involves GABABR-dependent suppression of adenylyl cyclase and consequent reduction of PKA activity. In this respect, CB1+ to pyramidal cell synapses differ from the majority of the other hippocampal inhibitory connections where theta burst stimulation results in long-term potentiation.
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Affiliation(s)
- Dave Jappy
- OpenLab of Neurobiology, Kazan Federal University Kazan, Russia
| | | | - Andreas Draguhn
- Department of Physiology and Pathophysiology, University of Heidelberg Heidelberg, Germany
| | - Andrei Rozov
- OpenLab of Neurobiology, Kazan Federal UniversityKazan, Russia; Department of Physiology and Pathophysiology, University of HeidelbergHeidelberg, Germany
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38
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Bohnsack JP, Carlson SL, Morrow AL. Differential regulation of synaptic and extrasynaptic α4 GABA(A) receptor populations by protein kinase A and protein kinase C in cultured cortical neurons. Neuropharmacology 2016; 105:124-132. [PMID: 26767953 DOI: 10.1016/j.neuropharm.2016.01.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 12/07/2015] [Accepted: 01/04/2016] [Indexed: 11/24/2022]
Abstract
The GABAA α4 subunit exists in two distinct populations of GABAA receptors. Synaptic GABAA α4 receptors are localized at the synapse and mediate phasic inhibitory neurotransmission, while extrasynaptic GABAA receptors are located outside of the synapse and mediate tonic inhibitory transmission. These receptors have distinct pharmacological and biophysical properties that contribute to interest in how these different subtypes are regulated under physiological and pathological states. We utilized subcellular fractionation procedures to separate these populations of receptors in order to investigate their regulation by protein kinases in cortical cultured neurons. Protein kinase A (PKA) activation decreases synaptic α4 expression while protein kinase C (PKC) activation increases α4 subunit expression, and these effects are associated with increased β3 S408/409 or γ2 S327 phosphorylation respectively. In contrast, PKA activation increases extrasynaptic α4 and δ subunit expression, while PKC activation has no effect. Our findings suggest synaptic and extrasynaptic GABAA α4 subunit expression can be modulated by PKA to inform the development of more specific therapeutics for neurological diseases that involve deficits in GABAergic transmission.
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Affiliation(s)
- John Peyton Bohnsack
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7365, USA; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill NC, 27599-7178, USA
| | - Stephen L Carlson
- Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill NC, 27599-7178, USA
| | - A Leslie Morrow
- Department of Pharmacology, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7365, USA; Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599-7365, USA; Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill, Chapel Hill NC, 27599-7178, USA.
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39
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Gravielle MC. Activation-induced regulation of GABAA receptors: Is there a link with the molecular basis of benzodiazepine tolerance? Pharmacol Res 2015; 109:92-100. [PMID: 26733466 DOI: 10.1016/j.phrs.2015.12.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/21/2015] [Accepted: 12/22/2015] [Indexed: 12/01/2022]
Abstract
Benzodiazepines have been used clinically for more than 50 years to treat disorders such as insomnia, anxiety, and epilepsy, as well as to aid muscle relaxation and anesthesia. The therapeutic index for benzodiazepines if very high and the toxicity is low. However, their usefulness is limited by the development of either or both tolerance to most of their pharmacological actions and dependence. Tolerance develops at different rates depending on the pharmacological action, suggesting the existence of distinct mechanisms for each behavioral parameter. Alternatively, multiple mechanisms could coexist depending on the subtype of GABAA receptor expressed and the brain region involved. Because most of the pharmacological actions of benzodiazepines are mediated through GABAA receptor binding, adaptive alterations in the number, structure, and/or functions of these receptors may play an important role in the development of tolerance. This review is focused on the regulation of GABAA receptors induced by long-term benzodiazepine exposure and its relationship with the development of tolerance. Understanding the mechanisms behind benzodiazepine tolerance is critical for designing drugs that could maintain their efficacy during long-term treatments.
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Affiliation(s)
- María Clara Gravielle
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
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40
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Yang G, Ren Z, Mei YA. Exposure to 50 Hz magnetic field modulates GABAA currents in cerebellar granule neurons through an EP receptor-mediated PKC pathway. J Cell Mol Med 2015; 19:2413-22. [PMID: 26176998 PMCID: PMC4594682 DOI: 10.1111/jcmm.12626] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 05/12/2015] [Indexed: 12/31/2022] Open
Abstract
Previous work from both our lab and others have indicated that exposure to 50 Hz magnetic fields (ELF-MF) was able to modify ion channel functions. However, very few studies have investigated the effects of MF on γ-aminobutyric acid (GABA) type A receptors (GABA(A) Rs) channel functioning, which are fundamental to overall neuronal excitability. Here, our major goal is to reveal the potential effects of ELF-MF on GABA(A) Rs activity in rat cerebellar granule neurons (CGNs). Our results indicated that exposing CGNs to 1 mT ELF-MF for 60 min. significantly increased GABA(A) R currents without modifying sensitivity to GABA. However, activation of PKA by db-cAMP failed to do so, but led to a slight decrease instead. On the other hand, PKC activation or inhibition by PMA or Bis and Docosahexaenoic acid (DHA) mimicked or eliminated the field-induced-increase of GABA(A) R currents. Western blot analysis indicated that the intracellular levels of phosphorylated PKC (pPKC) were significantly elevated after 60 min. of ELF-MF exposure, which was subsequently blocked by application of DHA or EP1 receptor-specific (prostaglandin E receptor 1) antagonist (SC19220), but not by EP2-EP4 receptor-specific antagonists. SC19220 also significantly inhibited the ELF-MF-induced elevation on GABA(A) R currents. Together, these data obviously demonstrated for the first time that neuronal GABA(A) currents are significantly increased by ELF-MF exposure, and also suggest that these effects are mediated via an EP1 receptor-mediated PKC pathway. Future work will focus on a more comprehensive analysis of the physiological and/or pathological consequences of these effects.
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Affiliation(s)
- Guang Yang
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan UniversityShanghai, China
| | - Zhen Ren
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan UniversityShanghai, China
| | - Yan-Ai Mei
- School of Life Sciences, Institute of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan UniversityShanghai, China
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He Q, Duguid I, Clark B, Panzanelli P, Patel B, Thomas P, Fritschy JM, Smart TG. Interneuron- and GABA(A) receptor-specific inhibitory synaptic plasticity in cerebellar Purkinje cells. Nat Commun 2015; 6:7364. [PMID: 26179122 PMCID: PMC4518301 DOI: 10.1038/ncomms8364] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 05/01/2015] [Indexed: 01/16/2023] Open
Abstract
Inhibitory synaptic plasticity is important for shaping both neuronal excitability and network activity. Here we investigate the input and GABA(A) receptor subunit specificity of inhibitory synaptic plasticity by studying cerebellar interneuron-Purkinje cell (PC) synapses. Depolarizing PCs initiated a long-lasting increase in GABA-mediated synaptic currents. By stimulating individual interneurons, this plasticity was observed at somatodendritic basket cell synapses, but not at distal dendritic stellate cell synapses. Basket cell synapses predominantly express β2-subunit-containing GABA(A) receptors; deletion of the β2-subunit ablates this plasticity, demonstrating its reliance on GABA(A) receptor subunit composition. The increase in synaptic currents is dependent upon an increase in newly synthesized cell surface synaptic GABA(A) receptors and is abolished by preventing CaMKII phosphorylation of GABA(A) receptors. Our results reveal a novel GABA(A) receptor subunit- and input-specific form of inhibitory synaptic plasticity that regulates the temporal firing pattern of the principal output cells of the cerebellum.
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Affiliation(s)
- Qionger He
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Ian Duguid
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Beverley Clark
- Wolfson Institute for Biomedical Research, UCL, Gower Street, London WC1E 6BT, UK
| | - Patrizia Panzanelli
- Department of Neuroscience Rita Levi Montalcini, University of Turin, 15-10126 Turin, Italy
| | - Bijal Patel
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Philip Thomas
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Jean-Marc Fritschy
- Institute of Pharmacology, University of Zurich, Winterthurestrasse 190, Zurich 8057, Switzerland
| | - Trevor G Smart
- Department of Neuroscience, Physiology and Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
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Jang HJ, Cho KH, Joo K, Kim MJ, Rhie DJ. Differential modulation of phasic and tonic inhibition underlies serotonergic suppression of long-term potentiation in the rat visual cortex. Neuroscience 2015; 301:351-62. [PMID: 26086544 DOI: 10.1016/j.neuroscience.2015.06.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 05/07/2015] [Accepted: 06/09/2015] [Indexed: 01/22/2023]
Abstract
GABA receptor type A (GABA(A)R)-mediated inhibition is divided into phasic and tonic inhibition. GABA(A)Rs mediating the two inhibitory modalities exhibit differences in subcellular localization and subunit composition. We previously demonstrated that phasic and tonic inhibition are independently regulated by Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and protein kinase A (PKA), respectively. Since modulation of GABA(A)Rs by phosphorylation differs depending on subunit composition and protein kinases, phasic and tonic inhibition might be differentially regulated by a single neuromodulator activating multiple protein kinases. However, the neuromodulatory control for phasic and tonic inhibition is largely unknown. Thus, in the present study, we concurrently investigated the serotonin (5-HT) regulation of phasic and tonic inhibition and its functional implication in the pyramidal neurons of the rat visual cortex. Interestingly, 5-HT enhanced phasic inhibition but suppressed tonic inhibition. Increase in phasic inhibition was mediated by 5-HT2 receptor and CaMKII, whereas decrease in tonic inhibition depended on 5-HT1A receptor and PKA. Thus, phasic and tonic inhibition might be independently regulated even by a single neuromodulator. Functionally, the opposite modulation of phasic and tonic inhibition decreased the summation of consecutive excitatory postsynaptic potentials (EPSPs) without affecting the shape of single EPSPs, which might underlie the suppression of the induction of long-term potentiation by 5-HT. These results suggest that the integrative regulation of phasic and tonic inhibition provides mechanisms for elaborate modulation of shape and summation of EPSPs and long-term synaptic plasticity.
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Affiliation(s)
- H-J Jang
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea; Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 137-701, Republic of Korea
| | - K-H Cho
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea
| | - K Joo
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea
| | - M-J Kim
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea
| | - D-J Rhie
- Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea; Catholic Neuroscience Institute, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
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Persistent CaMKII activation mediates learning-induced long-lasting enhancement of synaptic inhibition. J Neurosci 2015; 35:128-39. [PMID: 25568108 DOI: 10.1523/jneurosci.2123-14.2015] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Training rats in a particularly difficult olfactory-discrimination task results in acquisition of high skill to perform the task superbly, termed "rule learning" or "learning set." Such complex learning results in enhanced intrinsic neuronal excitability of piriform cortex pyramidal neurons, and in their excitatory synaptic interconnections. These changes, while subserving memory maintenance, must be counterbalanced by modifications that prevent overspreading of activity and uncontrolled synaptic strengthening. Indeed, we have previously shown that the average amplitude of GABAA-mediated miniature IPSCs (mIPSCs) in these neurons is enhanced for several days after learning, an enhancement mediated via a postsynaptic mechanism. To unravel the molecular mechanism of this long-term inhibition enhancement, we tested the role of key second-messenger systems in maintaining such long-lasting modulation. The calcium/calmodulin-dependent kinase II (CaMKII) blocker, KN93, significantly reduced the average mIPSC amplitude in neurons from trained rats only to the average pretraining level. A similar effect was obtained by the CaMKII peptide inhibitor, tatCN21. Such reduction resulted from decreased single-channel conductance and not in the number of activated channels. The PKC inhibitor, GF109203X, reduced the average mIPSC amplitude in neurons from naive, pseudo-trained, and trained animals, and the difference between the trained and control groups remained. Such reduction resulted from a decrease in the number of activated channels. The PKA inhibitor H89 dihydrochloride did not affect the average mIPSC amplitude in neurons from any of the three groups. We conclude that learning-induced enhancement of GABAA-mediated synaptic inhibition is maintained by persistent CaMKII activation.
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Nakamura Y, Darnieder LM, Deeb TZ, Moss SJ. Regulation of GABAARs by phosphorylation. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 72:97-146. [PMID: 25600368 PMCID: PMC5337123 DOI: 10.1016/bs.apha.2014.11.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
γ-Aminobutyric acid type A receptors (GABAARs) are the principal mediators of fast synaptic inhibition in the brain as well as the low persistent extrasynaptic inhibition, both of which are fundamental to proper brain function. Thus unsurprisingly, deficits in GABAARs are implicated in a number of neurological disorders and diseases. The complexity of GABAAR regulation is determined not only by the heterogeneity of these receptors but also by its posttranslational modifications, the foremost, and best characterized of which is phosphorylation. This review will explore the details of this dynamic process, our understanding of which has barely scratched the surface. GABAARs are regulated by a number of kinases and phosphatases, and its phosphorylation plays an important role in governing its trafficking, expression, and interaction partners. Here, we summarize the progress in understanding the role phosphorylation plays in the regulation of GABAARs. This includes how phosphorylation can affect the allosteric modulation of GABAARs, as well as signaling pathways that affect GABAAR phosphorylation. Finally, we discuss the dysregulation of GABAAR phosphorylation and its implication in disease processes.
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Adams JM, Thomas P, Smart TG. Modulation of neurosteroid potentiation by protein kinases at synaptic- and extrasynaptic-type GABAA receptors. Neuropharmacology 2015; 88:63-73. [PMID: 25278033 PMCID: PMC4239298 DOI: 10.1016/j.neuropharm.2014.09.021] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/08/2014] [Accepted: 09/18/2014] [Indexed: 01/21/2023]
Abstract
GABAA receptors are important for inhibition in the CNS where neurosteroids and protein kinases are potent endogenous modulators. Acting individually, these can either enhance or depress receptor function, dependent upon the type of neurosteroid or kinase and the receptor subunit combination. However, in vivo, these modulators probably act in concert to fine-tune GABAA receptor activity and thus inhibition, although how this is achieved remains unclear. Therefore, we investigated the relationship between these modulators at synaptic-type α1β3γ2L and extrasynaptic-type α4β3δ GABAA receptors using electrophysiology. For α1β3γ2L, potentiation of GABA responses by tetrahydro-deoxycorticosterone was reduced after inhibiting protein kinase C, and enhanced following its activation, suggesting this kinase regulates neurosteroid modulation. In comparison, neurosteroid potentiation was reduced at α1β3(S408A,S409A)γ2L receptors, and unaltered by PKC inhibitors or activators, indicating that phosphorylation of β3 subunits is important for regulating neurosteroid activity. To determine whether extrasynaptic-type GABAA receptors were similarly modulated, α4β3δ and α4β3(S408A,S409A)δ receptors were investigated. Neurosteroid potentiation was reduced at both receptors by the kinase inhibitor staurosporine. By contrast, neurosteroid-mediated potentiation at α4(S443A)β3(S408A,S409A)δ receptors was unaffected by protein kinase inhibition, strongly suggesting that phosphorylation of α4 and β3 subunits is required for regulating neurosteroid activity at extrasynaptic receptors. Western blot analyses revealed that neurosteroids increased phosphorylation of β3(S408,S409) implying that a reciprocal pathway exists for neurosteroids to modulate phosphorylation of GABAA receptors. Overall, these findings provide important insight into the regulation of GABAA receptors in vivo, and into the mechanisms by which GABAergic inhibitory transmission may be simultaneously tuned by two endogenous neuromodulators.
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Affiliation(s)
- Joanna M Adams
- Department of Neuroscience, Physiology & Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Philip Thomas
- Department of Neuroscience, Physiology & Pharmacology, UCL, Gower Street, London WC1E 6BT, UK
| | - Trevor G Smart
- Department of Neuroscience, Physiology & Pharmacology, UCL, Gower Street, London WC1E 6BT, UK.
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Comenencia-Ortiz E, Moss SJ, Davies PA. Phosphorylation of GABAA receptors influences receptor trafficking and neurosteroid actions. Psychopharmacology (Berl) 2014; 231:3453-65. [PMID: 24847959 PMCID: PMC4135009 DOI: 10.1007/s00213-014-3617-z] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/02/2014] [Indexed: 01/06/2023]
Abstract
RATIONALE Gamma-aminobutyric acid type A receptors (GABAARs) are the principal mediators of inhibitory transmission in the mammalian central nervous system. GABAARs can be localized at post-synaptic inhibitory specializations or at extrasynaptic sites. While synaptic GABAARs are activated transiently following the release of GABA from presynaptic vesicles, extrasynaptic GABAARs are typically activated continuously by ambient GABA concentrations and thus mediate tonic inhibition. The tonic inhibitory currents mediated by extrasynaptic GABAARs control neuronal excitability and the strength of synaptic transmission. However, the mechanisms by which neurons control the functional properties of extrasynaptic GABAARs had not yet been explored. OBJECTIVES We review GABAARs, how they are assembled and trafficked, and the role phosphorylation has on receptor insertion and membrane stabilization. Finally, we review the modulation of GABAARs by neurosteroids and how GABAAR phosphorylation can influence the actions of neurosteroids. CONCLUSIONS Trafficking and stability of functional channels to the membrane surface are critical for inhibitory efficacy. Phosphorylation of residues within GABAAR subunits plays an essential role in the assembly, trafficking, and cell surface stability of GABAARs. Neurosteroids are produced in the brain and are highly efficacious allosteric modulators of GABAAR-mediated current. This allosteric modulation by neurosteroids is influenced by the phosphorylated state of the GABAAR which is subunit dependent, adding temporal and regional variability to the neurosteroid response. Possible links between neurosteroid actions, phosphorylation, and GABAAR trafficking remain to be explored, but potential novel therapeutic targets may exist for numerous neurological and psychological disorders which are linked to fluctuations in neurosteroid levels and GABAA subunit expression.
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Postsynaptic activity reverses the sign of the acetylcholine-induced long-term plasticity of GABAA inhibition. Proc Natl Acad Sci U S A 2014; 111:E2741-50. [PMID: 24938789 DOI: 10.1073/pnas.1321777111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Acetylcholine (ACh) regulates forms of plasticity that control cognitive functions but the underlying mechanisms remain largely unknown. ACh controls the intrinsic excitability, as well as the synaptic excitation and inhibition of CA1 hippocampal pyramidal cells (PCs), cells known to participate in circuits involved in cognition and spatial navigation. However, how ACh regulates inhibition in function of postsynaptic activity has not been well studied. Here we show that in rat PCs, a brief pulse of ACh or a brief stimulation of cholinergic septal fibers combined with repeated depolarization induces strong long-term enhancement of GABAA inhibition (GABAA-LTP). Indeed, this enhanced inhibition is due to the increased activation of α5βγ2 subunit-containing GABAA receptors by the GABA released. GABAA-LTP requires the activation of M1-muscarinic receptors and an increase in cytosolic Ca(2+). In the absence of PC depolarization ACh triggered a presynaptic depolarization-induced suppression of inhibition (DSI), revealing that postsynaptic activity gates the effects of ACh from presynaptic DSI to postsynaptic LTP. These results provide key insights into mechanisms potentially linked with cognitive functions, spatial navigation, and the homeostatic control of abnormal hyperexcitable states.
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48
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Deidda G, Bozarth IF, Cancedda L. Modulation of GABAergic transmission in development and neurodevelopmental disorders: investigating physiology and pathology to gain therapeutic perspectives. Front Cell Neurosci 2014; 8:119. [PMID: 24904277 PMCID: PMC4033255 DOI: 10.3389/fncel.2014.00119] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 04/14/2014] [Indexed: 01/30/2023] Open
Abstract
During mammalian ontogenesis, the neurotransmitter GABA is a fundamental regulator of neuronal networks. In neuronal development, GABAergic signaling regulates neural proliferation, migration, differentiation, and neuronal-network wiring. In the adult, GABA orchestrates the activity of different neuronal cell-types largely interconnected, by powerfully modulating synaptic activity. GABA exerts these functions by binding to chloride-permeable ionotropic GABAA receptors and metabotropic GABAB receptors. According to its functional importance during development, GABA is implicated in a number of neurodevelopmental disorders such as autism, Fragile X, Rett syndrome, Down syndrome, schizophrenia, Tourette's syndrome and neurofibromatosis. The strength and polarity of GABAergic transmission is continuously modulated during physiological, but also pathological conditions. For GABAergic transmission through GABAA receptors, strength regulation is achieved by different mechanisms such as modulation of GABAA receptors themselves, variation of intracellular chloride concentration, and alteration in GABA metabolism. In the never-ending effort to find possible treatments for GABA-related neurological diseases, of great importance would be modulating GABAergic transmission in a safe and possibly physiological way, without the dangers of either silencing network activity or causing epileptic seizures. In this review, we will discuss the different ways to modulate GABAergic transmission normally at work both during physiological and pathological conditions. Our aim is to highlight new research perspectives for therapeutic treatments that reinstate natural and physiological brain functions in neuro-pathological conditions.
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Affiliation(s)
- Gabriele Deidda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Ignacio F Bozarth
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
| | - Laura Cancedda
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia Genova, Italy
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Gutiérrez ML, Ferreri MC, Farb DH, Gravielle MC. GABA-induced uncoupling of GABA/benzodiazepine site interactions is associated with increased phosphorylation of the GABAA receptor. J Neurosci Res 2014; 92:1054-61. [PMID: 24723313 DOI: 10.1002/jnr.23387] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 02/14/2014] [Accepted: 02/26/2014] [Indexed: 11/08/2022]
Abstract
The use-dependent regulation of the GABAA receptor occurs under physiological, pathological, and pharmacological conditions. Tolerance induced by prolonged administration of benzodiazepines is associated with changes in GABAA receptor function. Chronic exposure of neurons to GABA for 48 hr induces a downregulation of the GABAA receptor number and an uncoupling of the GABA/benzodiazepine site interactions. A single brief exposure ((t1/2) = 3 min) of rat neocortical neurons to the neurotransmitter initiates a process that results in uncoupling hours later (t(1/2) = 12 hr) without alterations in the number of GABAA receptors and provides a paradigm to study the uncoupling mechanism selectively. Here we report that uncoupling induced by a brief GABAA receptor activation is blocked by the coincubation with inhibitors of protein kinases A and C, indicating that the uncoupling is mediated by the activation of a phosphorylation cascade. GABA-induced uncoupling is accompanied by subunit-selective changes in the GABAA receptor mRNA levels. However, the GABA-induced downregulation of the α3 subunit mRNA level is not altered by the kinase inhibitors, suggesting that the uncoupling is the result of a posttranscriptional regulatory process. GABA exposure also produces an increase in the serine phosphorylation on the GABAA receptor γ2 subunit. Taken together, our results suggest that the GABA-induced uncoupling is mediated by a posttranscriptional mechanism involving an increase in the phosphorylation of GABAA receptors. The uncoupling of the GABAA receptor may represent a compensatory mechanism to control GABAergic neurotransmission under conditions in which receptors are persistently activated.
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Affiliation(s)
- María L Gutiérrez
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
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Volgin DV, Lu JW, Stettner GM, Mann GL, Ross RJ, Morrison AR, Kubin L. Time- and behavioral state-dependent changes in posterior hypothalamic GABAA receptors contribute to the regulation of sleep. PLoS One 2014; 9:e86545. [PMID: 24466145 PMCID: PMC3897747 DOI: 10.1371/journal.pone.0086545] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 12/11/2013] [Indexed: 12/17/2022] Open
Abstract
Sleep-wake behavior is regulated by a circadian rhythm, homeostatically and by additional mechanisms that determine the timing of slow-wave sleep and rapid eye movement sleep (REMS) episodes. The posterior hypothalamus coordinates the neural and humoral signals with the rest-activity cycle. It contains wake-active neurons, and is a site where stimulation of inhibitory GABAA receptors promotes sleep, whereas their antagonism enhances wakefulness. We explored whether GABAergic mechanisms present in the posterior hypothalamus contribute to the homeostatic and other aspects of sleep-wake regulation. Using micropunches of tissue extracted from either the perifornical (PF) or dorsomedial (DM) regions of the posterior hypothalamus of rats, we determined that mRNA levels for selected subunits of GABAA receptors (β1, β3 and ε) were higher at the end of the active period or following sleep deprivation, when the need for sleep is high, than after several hours of sleep, when sleep need is partially fulfilled. Such a pattern was present in the PF region only, and was consistent with changes in β1 subunit and GABA synthesizing enzyme (GAD) protein levels. In contrast, in the DM region, the levels of GABAA receptor subunit mRNAs and proteins (α1, α2, β1) and GAD varied with circadian time, but were not responsive to sleep deprivation. Separate experiments with sleep-wake monitoring and local perfusion of the PF region with the GABAA receptor antagonist bicuculline revealed that the antagonist had a weaker sleep-reducing effect when sleep need was enhanced by sleep deprivation and that the increased amount of REMS characteristic of the late sleep period was dependent on endogenous GABAergic inhibition. These results support the concept that a varying magnitude of GABAergic inhibition exerted within the PF region contributes to the homeostatic regulation of sleep and shapes its temporal pattern, whereas GABAergic mechanisms in the DM region contribute to circadian regulation.
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Affiliation(s)
- Denys V. Volgin
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Jackie W. Lu
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Georg M. Stettner
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Graziella L. Mann
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Richard J. Ross
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Psychiatry, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Behavioral Health Service, Philadelphia Veterans Affairs Medical Center, Philadelphia, Pennsylvania, United States of America
| | - Adrian R. Morrison
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Leszek Kubin
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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