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Li S, Wei X, Huang H, Ye L, Ma M, Sun L, Lu Y, Wu Y. Neuroplastin exerts antiepileptic effects through binding to the α1 subunit of GABA type A receptors to inhibit the internalization of the receptors. J Transl Med 2023; 21:707. [PMID: 37814294 PMCID: PMC10563248 DOI: 10.1186/s12967-023-04596-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Accepted: 10/04/2023] [Indexed: 10/11/2023] Open
Abstract
BACKGROUND Seizures are associated with a decrease in γ-aminobutyric type A acid receptors (GABAaRs) on the neuronal surface, which may be regulated by enhanced internalization of GABAaRs. When interactions between GABAaR subunit α-1 (GABRA1) and postsynaptic scaffold proteins are weakened, the α1-containing GABAaRs leave the postsynaptic membrane and are internalized. Previous evidence suggested that neuroplastin (NPTN) promotes the localization of GABRA1 on the postsynaptic membrane. However, the association between NPTN and GABRA1 in seizures and its effect on the internalization of α1-containing GABAaRs on the neuronal surface has not been studied before. METHODS An in vitro seizure model was constructed using magnesium-free extracellular fluid, and an in vivo model of status epilepticus (SE) was constructed using pentylenetetrazole (PTZ). Additionally, in vitro and in vivo NPTN-overexpression models were constructed. Electrophysiological recordings and internalization assays were performed to evaluate the action potentials and miniature inhibitory postsynaptic currents of neurons, as well as the intracellular accumulation ratio of α1-containing GABAaRs in neurons. Western blot analysis was performed to detect the expression of GABRA1 and NPTN both in vitro and in vivo. Immunofluorescence co-localization analysis and co-immunoprecipitation were performed to evaluate the interaction between GABRA1 and NPTN. RESULTS The expression of GABRA1 was found to be decreased on the neuronal surface both in vivo and in vitro seizure models. In the in vitro seizure model, α1-containing GABAaRs showed increased internalization. NPTN expression was found to be positively correlated with GABRA1 expression on the neuronal surface both in vivo and in vitro seizure models. In addition, NPTN overexpression alleviated seizures and NPTN was shown to bind to GABRA1 to form protein complexes that can be disrupted during seizures in both in vivo and in vitro models. Furthermore, NPTN was found to inhibit the internalization of α1-containing GABAaRs in the in vitro seizure model. CONCLUSION Our findings provide evidence that NPTN may exert antiepileptic effects by binding to GABRA1 to inhibit the internalization of α1-containing GABAaRs.
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Affiliation(s)
- Sijun Li
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Xing Wei
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Hongmi Huang
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Lin Ye
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Meigang Ma
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Lanfeng Sun
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Yuling Lu
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China
| | - Yuan Wu
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Guangxi Medical University, Shuangyong Road No.6, Nanning, Guangxi, China.
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Hernandez CC, Tian X, Hu N, Shen W, Catron MA, Yang Y, Chen J, Jiang Y, Zhang Y, Macdonald RL. Dravet syndrome-associated mutations in GABRA1, GABRB2 and GABRG2 define the genetic landscape of defects of GABA A receptors. Brain Commun 2021; 3:fcab033. [PMID: 34095830 PMCID: PMC8176149 DOI: 10.1093/braincomms/fcab033] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 01/07/2021] [Accepted: 01/14/2021] [Indexed: 12/29/2022] Open
Abstract
Dravet syndrome is a rare, catastrophic epileptic encephalopathy that begins in the first year of life, usually with febrile or afebrile hemiclonic or generalized tonic-clonic seizures followed by status epilepticus. De novo variants in genes that mediate synaptic transmission such as SCN1A and PCDH19 are often associated with Dravet syndrome. Recently, GABAA receptor subunit genes (GABRs) encoding α1 (GABRA1), β3 (GABRB3) and γ2 (GABRG2), but not β2 (GABRB2) or β1 (GABRB1), subunits are frequently associated with Dravet syndrome or Dravet syndrome-like phenotype. We performed next generation sequencing on 870 patients with Dravet syndrome and identified nine variants in three different GABRs. Interestingly, the variants were all in genes encoding the most common GABAA receptor, the α1β2γ2 receptor. Mutations in GABRA1 (c.644T>C, p. L215P; c.640C>T, p. R214C; c.859G>A; V287I; c.641G>A, p. R214H) and GABRG2 (c.269C>G, p. T90R; c.1025C>T, p. P342L) presented as de novo cases, while in GABRB2 two variants were de novo (c.992T>C, p. F331S; c.542A>T, p. Y181F) and one was autosomal dominant and inherited from the maternal side (c.990_992del, p.330_331del). We characterized the effects of these GABR variants on GABAA receptor biogenesis and channel function. We found that defects in receptor gating were the common deficiency of GABRA1 and GABRB2 Dravet syndrome variants, while mainly trafficking defects were found with the GABRG2 (c.269C>G, p. T90R) variant. It seems that variants in α1 and β2 subunits are less tolerated than in γ2 subunits, since variant α1 and β2 subunits express well but were functionally deficient. This suggests that all of these GABR variants are all targeting GABR genes that encode the assembled α1β2γ2 receptor, and regardless of which of the three subunits are mutated, variants in genes coding for α1, β2 and γ2 receptor subunits make them candidate causative genes in the pathogenesis of Dravet syndrome.
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Affiliation(s)
- Ciria C Hernandez
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48198, USA
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - XiaoJuan Tian
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
- Department of Neurology, Beijing Children’s Hospital, Capital Medical University, National Center for Children’s Health, Beijing 100045, China
| | - Ningning Hu
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Wangzhen Shen
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
| | - Mackenzie A Catron
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
- Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37240, USA
| | - Ying Yang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Jiaoyang Chen
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Yuwu Jiang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
- Center of Epilepsy, Beijing Institute for Brain Disorders, Beijing 100069, China
| | - Yuehua Zhang
- Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing 100034, China
| | - Robert L Macdonald
- Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37240, USA
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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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Wongsamitkul N, Maldifassi MC, Simeone X, Baur R, Ernst M, Sigel E. α subunits in GABA A receptors are dispensable for GABA and diazepam action. Sci Rep 2017; 7:15498. [PMID: 29138471 PMCID: PMC5686171 DOI: 10.1038/s41598-017-15628-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/31/2017] [Indexed: 11/10/2022] Open
Abstract
The major isoform of the GABAA receptor is α1β2γ2. The binding sites for the agonist GABA are located at the β2+/α1− subunit interfaces and the modulatory site for benzodiazepines at α1+/γ2−. In the absence of α1 subunits, a receptor was formed that was gated by GABA and modulated by diazepam similarly. This indicates that alternative subunits can take over the role of the α1 subunits. Point mutations were introduced in β2 or γ2 subunits at positions homologous to α1− benzodiazepine binding and GABA binding positions, respectively. From this mutation work we conclude that the site for GABA is located at a β2+/β2− subunit interface and that the diazepam site is located at the β2+/γ2− subunit interface. Computational docking leads to a structural hypothesis attributing this non-canonical interaction to a binding mode nearly identical with the one at the α1+/γ2− interface. Thus, the β2 subunit can take over the role of the α1 subunit for the formation of both sites, its minus side for the GABA binding site and its plus side for the diazepam binding site.
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Affiliation(s)
- Nisa Wongsamitkul
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Maria C Maldifassi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.,Centro Interdisciplinario de Neurociencia de Valparaíso. Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Xenia Simeone
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Roland Baur
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Margot Ernst
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Erwin Sigel
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland.
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Chua HC, Chebib M. GABA A Receptors and the Diversity in their Structure and Pharmacology. ADVANCES IN PHARMACOLOGY 2017; 79:1-34. [DOI: 10.1016/bs.apha.2017.03.003] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Beart PM. Synaptic signalling and its interface with neuropathologies: snapshots from the past, present and future. J Neurochem 2016; 139 Suppl 2:76-90. [PMID: 27144305 DOI: 10.1111/jnc.13598] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 02/09/2016] [Accepted: 02/26/2016] [Indexed: 11/30/2022]
Abstract
This 'Past to Future' Review as part of the 60th anniversary year of the Journal of Neurochemistry focuses on synaptic transmission and associated signalling, and seeks to identify seminal progress in neurochemistry over the last 10 years which has advanced our understanding of neuronal communication in brain. The approach adopted analyses neurotransmitters on a case by case basis (i.e. amino acids, monoamines, acetylcholine, neuropeptides, ATP/purines and gasotransmitters) to highlight novel findings that have changed the way we view each type of transmitter, to explore commonalities and interactions, and to note how new insights have changed the way we view the biology of degenerative, psychiatric and behavioural conditions. Across all transmitter systems there was remarkable growth in the identification of targets likely to provide therapeutic benefit and which undoubtedly was driven by the elucidation of circuit function and new vistas of synaptic signalling. There has been an increasing trend to relate signalling to disease, notably for Alzheimer's and Parkinson's disease and related conditions, and which has occurred for each transmitter family. Forebrain circuitry and tonic excitatory control have been the centre of great attention yielding novel findings that will impact upon cognitive, emotional and addictive behaviours. Other impressive insights focus on gasotransmitters integrating activity as volume transmitters. Exciting developments in how serotonin, cholinergic, l-glutamate, galanin and adenosine receptors and their associated signalling can be beneficially targeted should underpin the development of new therapies. Clearly integrated, multifaceted neurochemistry has changed the way we view synaptic signalling and its relevance to pathobiology. Highlighted are important advances in synaptic signalling over the last decade in the Journal of Neurochemistry. Across all transmitter systems elucidation of circuit function, and notably molecular insights, have underpinned remarkable growth in the identification of targets likely to provide therapeutic benefit in neuropathologies. Another commonality was wide interest in forebrain circuitry and its tonic excitatory control. Increasingly observations relate to signalling in disease and behavioural conditions. This article is part of the 60th Anniversary special issue.
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Affiliation(s)
- Philip M Beart
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, Australia.
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Bracamontes JR, Akk G, Steinbach JH. Introduced Amino Terminal Epitopes Can Reduce Surface Expression of Neuronal Nicotinic Receptors. PLoS One 2016; 11:e0151071. [PMID: 26963253 PMCID: PMC4786271 DOI: 10.1371/journal.pone.0151071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 02/23/2016] [Indexed: 12/05/2022] Open
Abstract
Epitopes accessible on the surface of intact cells are extremely valuable in studies of membrane proteins, allowing quantification and determination of the distribution of proteins as well as identification of cells expressing large numbers of proteins. However for many membrane proteins there are no suitable antibodies to native sequences, due to lack of availability, low affinity or lack of specificity. In these cases the use of an introduced epitope at specific sites in the protein of interest can often provide a suitable tool for studies. However, the introduction of the epitope sequence has the potential to affect protein expression, the assembly of multisubunit proteins or transport to the surface membrane. We find that surface expression of heteromeric neuronal nicotinic receptors containing the α4 and β4 subunits can be affected by introduced epitopes when inserted near the amino terminus of a subunit. The FLAG epitope greatly reduces surface expression when introduced into either α4 or β4 subunits, the V5 epitope has little effect when placed in either, while the Myc epitope reduces expression more when inserted into β4 than α4. These results indicate that the extreme amino terminal region is important for assembly of these receptors, and demonstrate that some widely used introduced epitopes may severely reduce surface expression.
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Affiliation(s)
- John R. Bracamontes
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, United States of America
| | - Gustav Akk
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, United States of America
- Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, Saint Louis, MO, United States of America
| | - Joe Henry Steinbach
- Department of Anesthesiology, Washington University School of Medicine, Saint Louis, MO, United States of America
- Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, Saint Louis, MO, United States of America
- * E-mail:
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Fu YL, Wang YJ, Mu TW. Proteostasis Maintenance of Cys-Loop Receptors. ION CHANNELS AS THERAPEUTIC TARGETS, PART A 2016; 103:1-23. [DOI: 10.1016/bs.apcsb.2015.11.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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