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Wang X, Zhao Z, Guo J, Mei D, Duan Y, Zhang Y, Gou L. GABA B1 receptor knockdown in prefrontal cortex induces behavioral aberrations associated with autism spectrum disorder in mice. Brain Res Bull 2023; 202:110755. [PMID: 37678443 DOI: 10.1016/j.brainresbull.2023.110755] [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: 06/14/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 09/09/2023]
Abstract
Autism spectrum disorder (ASD) is a set of heterogeneous neurodevelopmental disorders, characterized by social interaction deficit, stereotyped or repetitive behaviors. Apart from these core symptoms, a great number of individuals with ASD exhibit higher levels of anxiety and memory deficits. Previous studies demonstrate pronounced decrease of γ-aminobutyric acid B1 receptor (GABAB1R) protein level of frontal lobe in both ASD patients and animal models. The aim of the present study was to determine the role of GABAB1R in ASD-related behavioral aberrations. Herein, the protein and mRNA levels of GABAB1R in the prefrontal cortex (PFC) of sodium valproic acid (VPA)-induced mouse ASD model were determined by Western blot and qRT-PCR analysis, respectively. Moreover, the behavioral abnormalities in naive mice with GABAB1R knockdown mediated by recombinant adeno-associated virus (rAAV) were assessed in a comprehensive test battery consisted of social interaction, marble burying, self-grooming, open-field, Y-maze and novel object recognition tests. Furthermore, the action potential changes induced by GABAB1R deficiency were examined in neurons within the PFC of mouse. The results show that the mRNA and protein levels of GABAB1R in the PFC of prenatal VPA-induced mouse ASD model were decreased. Concomitantly, naive mice with GABAB1R knockdown exhibited ASD-like behaviors, such as impaired social interaction and communication, elevated stereotypes, anxiety and memory deficits. Patch-clamp recordings also revealed that GABAB1R knockdown provoked enhanced neuronal excitability by increasing action potential discharge frequencies. Overall, these findings support a notion that GABAB1R deficiency might contribute to ASD-like phenotypes, with the pathogenesis most likely resulting from enhanced neuronal excitability. SUBHEADINGS: GABAB1 Knockdown Induces Behavioral Aberrations with ASD.
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Affiliation(s)
- Xiaona Wang
- Children's Hospital Affiliated to Zhengzhou University, Henan Children's Hospital, Zhengzhou Children's Hospital, Henan Key Laboratory of Children's Genetics and Metabolic Diseases, Henan Children's Neurodevelopment Engineering Research Center, Zhengzhou, China.
| | - Zhengqin Zhao
- Department of Nuclear Medicine, Affiliated Hospital of Guangdong Medical University, Zhanjiang, Guangdong, China
| | - Jisheng Guo
- School of Basic Medical Sciences, Yantai Campus of Binzhou Medical University, Yantai City, Shandong, China
| | - Daoqi Mei
- Department of Neurology, Children's Hospital Affiliated to Zhengzhou University, Zhengzhou, China
| | - Yongtao Duan
- Children's Hospital Affiliated to Zhengzhou University, Henan Children's Hospital, Zhengzhou Children's Hospital, Henan Key Laboratory of Children's Genetics and Metabolic Diseases, Henan Children's Neurodevelopment Engineering Research Center, Zhengzhou, China
| | - Yaodong Zhang
- Children's Hospital Affiliated to Zhengzhou University, Henan Children's Hospital, Zhengzhou Children's Hospital, Henan Key Laboratory of Children's Genetics and Metabolic Diseases, Henan Children's Neurodevelopment Engineering Research Center, Zhengzhou, China.
| | - Lingshan Gou
- Peninsula Cancer Research Center, Binzhou Medical University, Yantai, Shandong, China.
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Unravelling biological roles and mechanisms of GABA BR on addiction and depression through mood and memory disorders. Biomed Pharmacother 2022; 155:113700. [PMID: 36152411 DOI: 10.1016/j.biopha.2022.113700] [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: 08/12/2022] [Revised: 09/08/2022] [Accepted: 09/13/2022] [Indexed: 11/23/2022] Open
Abstract
The metabotropic γ-aminobutyric acid type B receptor (GABABR) remains a hotspot in the recent research area. Being an idiosyncratic G-protein coupled receptor family member, the GABABR manifests adaptively tailored functionality under multifarious modulations by a constellation of agents, pointing to cross-talk between receptors and effectors that converge on the domains of mood and memory. This review systematically summarizes the latest achievements in signal transduction mechanisms of the GABABR-effector-regulator complex and probes how the up-and down-regulation of membrane-delimited GABABRs are associated with manifold intrinsic and extrinsic agents in synaptic strength and plasticity. Neuropsychiatric conditions depression and addiction share the similar pathophysiology of synapse inadaptability underlying negative mood-related processes, memory formations, and impairments. In the attempt to emphasize all convergent discoveries, we hope the insights gained on the GABABR system mechanisms of action are conducive to designing more therapeutic candidates so as to refine the prognosis rate of diseases and minimize side effects.
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Neurexins regulate presynaptic GABA B-receptors at central synapses. Nat Commun 2021; 12:2380. [PMID: 33888718 PMCID: PMC8062527 DOI: 10.1038/s41467-021-22753-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 03/20/2021] [Indexed: 11/28/2022] Open
Abstract
Diverse signaling complexes are precisely assembled at the presynaptic active zone for dynamic modulation of synaptic transmission and synaptic plasticity. Presynaptic GABAB-receptors nucleate critical signaling complexes regulating neurotransmitter release at most synapses. However, the molecular mechanisms underlying assembly of GABAB-receptor signaling complexes remain unclear. Here we show that neurexins are required for the localization and function of presynaptic GABAB-receptor signaling complexes. At four model synapses, excitatory calyx of Held synapses in the brainstem, excitatory and inhibitory synapses on hippocampal CA1-region pyramidal neurons, and inhibitory basket cell synapses in the cerebellum, deletion of neurexins rendered neurotransmitter release significantly less sensitive to GABAB-receptor activation. Moreover, deletion of neurexins caused a loss of GABAB-receptors from the presynaptic active zone of the calyx synapse. These findings extend the role of neurexins at the presynaptic active zone to enabling GABAB-receptor signaling, supporting the notion that neurexins function as central organizers of active zone signaling complexes. Neurexins are evolutionarily conserved cell adhesion molecules that tune synapse formation and specification. Here the authors show that neurexins play similar roles in regulating presynaptic GABAB receptors at multiple CNS synapses.
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Mechanisms and Regulation of Neuronal GABA B Receptor-Dependent Signaling. Curr Top Behav Neurosci 2020; 52:39-79. [PMID: 32808092 DOI: 10.1007/7854_2020_129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
γ-Aminobutyric acid B receptors (GABABRs) are broadly expressed throughout the central nervous system where they play an important role in regulating neuronal excitability and synaptic transmission. GABABRs are G protein-coupled receptors that mediate slow and sustained inhibitory actions via modulation of several downstream effector enzymes and ion channels. GABABRs are obligate heterodimers that associate with diverse arrays of proteins to form modular complexes that carry out distinct physiological functions. GABABR-dependent signaling is fine-tuned and regulated through a multitude of mechanisms that are relevant to physiological and pathophysiological states. This review summarizes the current knowledge on GABABR signal transduction and discusses key factors that influence the strength and sensitivity of GABABR-dependent signaling in neurons.
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TERUNUMA M. Diversity of structure and function of GABA B receptors: a complexity of GABA B-mediated signaling. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2018; 94:390-411. [PMID: 30541966 PMCID: PMC6374141 DOI: 10.2183/pjab.94.026] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2018] [Accepted: 10/09/2018] [Indexed: 05/24/2023]
Abstract
γ-aminobutyric acid type B (GABAB) receptors are broadly expressed in the nervous system and play an important role in neuronal excitability. GABAB receptors are G protein-coupled receptors that mediate slow and prolonged inhibitory action, via activation of Gαi/o-type proteins. GABAB receptors mediate their inhibitory action through activating inwardly rectifying K+ channels, inactivating voltage-gated Ca2+ channels, and inhibiting adenylate cyclase. Functional GABAB receptors are obligate heterodimers formed by the co-assembly of R1 and R2 subunits. It is well established that GABAB receptors interact not only with G proteins and effectors but also with various proteins. This review summarizes the structure, subunit isoforms, and function of GABAB receptors, and discusses the complexity of GABAB receptors, including how receptors are localized in specific subcellular compartments, the mechanism regulating cell surface expression and mobility of the receptors, and the diversity of receptor signaling through receptor crosstalk and interacting proteins.
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Affiliation(s)
- Miho TERUNUMA
- Division of Oral Biochemistry, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
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Wild AR, Dell'Acqua ML. Potential for therapeutic targeting of AKAP signaling complexes in nervous system disorders. Pharmacol Ther 2017; 185:99-121. [PMID: 29262295 DOI: 10.1016/j.pharmthera.2017.12.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
A common feature of neurological and neuropsychiatric disorders is a breakdown in the integrity of intracellular signal transduction pathways. Dysregulation of ion channels and receptors in the cell membrane and the enzymatic mediators that link them to intracellular effectors can lead to synaptic dysfunction and neuronal death. However, therapeutic targeting of these ubiquitous signaling elements can lead to off-target side effects due to their widespread expression in multiple systems of the body. A-kinase anchoring proteins (AKAPs) are multivalent scaffolding proteins that compartmentalize a diverse range of receptor and effector proteins to streamline signaling within nanodomain signalosomes. A number of essential neurological processes are known to critically depend on AKAP-directed signaling and an understanding of the role AKAPs play in nervous system disorders has emerged in recent years. Selective targeting of AKAP protein-protein interactions may be a means to uncouple pathologically active signaling pathways in neurological disorders with a greater degree of specificity. In this review we will discuss the role of AKAPs in both regulating normal nervous system function and dysfunction associated with disease, and the potential for therapeutic targeting of AKAP signaling complexes.
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Affiliation(s)
- Angela R Wild
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
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Pin JP, Bettler B. Organization and functions of mGlu and GABAB receptor complexes. Nature 2016; 540:60-68. [DOI: 10.1038/nature20566] [Citation(s) in RCA: 155] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 10/21/2016] [Indexed: 02/08/2023]
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Blanz J, Zunke F, Markmann S, Damme M, Braulke T, Saftig P, Schwake M. Mannose 6-phosphate-independent Lysosomal Sorting of LIMP-2. Traffic 2015; 16:1127-36. [PMID: 26219725 DOI: 10.1111/tra.12313] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 07/22/2015] [Accepted: 07/23/2015] [Indexed: 12/12/2022]
Abstract
The lysosomal integral membrane protein type 2 (LIMP-2/SCARB2) has been described as a mannose 6-phosphate (M6P)-independent trafficking receptor for β-glucocerebrosidase (GC). Recently, a putative M6P residue in a crystal structure of a recombinantly expressed LIMP-2 ectodomain has been reported. Based on surface plasmon resonance and fluorescence lifetime imaging analyses, it was suggested that the interaction of soluble LIMP-2 with the cation-independent M6P receptor (MPR) results in M6P-dependent targeting of LIMP-2 to lysosomes. As the physiological relevance of this observation was not addressed, we investigated M6P-dependent delivery of LIMP-2 to lysosomes in murine liver and mouse embryonic fibroblasts. We demonstrate that LIMP-2 and GC reach lysosomes independent of the M6P pathway. In fibroblasts lacking either MPRs or the M6P-forming N-acetylglucosamine (GlcNAc)-1-phosphotransferase, LIMP-2 still localizes to lysosomes. Immunoblot analyses also revealed comparable LIMP-2 levels within lysosomes purified from liver of wild-type (wt) and GlcNAc-1-phosphotransferase-defective mice. Heterologous expression of the luminal domain of LIMP-2 in wild-type, LIMP-2-deficient and GlcNAc-1-phosphotransferase-defective cells further established that the M6P modification is dispensable for lysosomal sorting of LIMP-2. Finally, cathepsin Z, a known GlcNAc-1-phosphotransferase substrate, but not LIMP-2, could be precipitated with M6P-specific antibodies. These data prove M6P-independent lysosomal sorting of LIMP-2 and subsequently GC in vivo.
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Affiliation(s)
- Judith Blanz
- Biochemisches Institut der Christian Albrechts Universität zu Kiel, Otto-Hahn-Platz 9, 24118, Kiel, Germany
| | - Friederike Zunke
- Biochemisches Institut der Christian Albrechts Universität zu Kiel, Otto-Hahn-Platz 9, 24118, Kiel, Germany
| | - Sandra Markmann
- Arbeitsbereich Molekularbiologie, Klinik und Poliklinik für Kinder- und Jugendmedizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Markus Damme
- Biochemisches Institut der Christian Albrechts Universität zu Kiel, Otto-Hahn-Platz 9, 24118, Kiel, Germany
| | - Thomas Braulke
- Arbeitsbereich Molekularbiologie, Klinik und Poliklinik für Kinder- und Jugendmedizin, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Paul Saftig
- Biochemisches Institut der Christian Albrechts Universität zu Kiel, Otto-Hahn-Platz 9, 24118, Kiel, Germany
| | - Michael Schwake
- Biochemie III/ Fakultät für Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
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Kantamneni S. Cross-talk and regulation between glutamate and GABAB receptors. Front Cell Neurosci 2015; 9:135. [PMID: 25914625 PMCID: PMC4392697 DOI: 10.3389/fncel.2015.00135] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/23/2015] [Indexed: 12/16/2022] Open
Abstract
Brain function depends on co-ordinated transmission of signals from both excitatory and inhibitory neurotransmitters acting upon target neurons. NMDA, AMPA and mGluR receptors are the major subclasses of glutamate receptors that are involved in excitatory transmission at synapses, mechanisms of activity dependent synaptic plasticity, brain development and many neurological diseases. In addition to canonical role of regulating presynaptic release and activating postsynaptic potassium channels, GABAB receptors also regulate glutamate receptors. There is increasing evidence that metabotropic GABAB receptors are now known to play an important role in modulating the excitability of circuits throughout the brain by directly influencing different types of postsynaptic glutamate receptors. Specifically, GABAB receptors affect the expression, activity and signaling of glutamate receptors under physiological and pathological conditions. Conversely, NMDA receptor activity differentially regulates GABAB receptor subunit expression, signaling and function. In this review I will describe how GABAB receptor activity influence glutamate receptor function and vice versa. Such a modulation has widespread implications for the control of neurotransmission, calcium-dependent neuronal function, pain pathways and in various psychiatric and neurodegenerative diseases.
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Affiliation(s)
- Sriharsha Kantamneni
- Bradford School of Pharmacy, School of Life Sciences, University of Bradford Bradford, West Yorkshire, UK
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10
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Kennedy JE, Marchese A. Regulation of GPCR Trafficking by Ubiquitin. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:15-38. [PMID: 26055053 DOI: 10.1016/bs.pmbts.2015.02.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
G protein-coupled receptor (GPCR)-promoted signaling mediates cellular responses to a variety of stimuli involved in diverse physiological processes. In addition, GPCRs are also the largest class of target for many drugs used to treat a variety of diseases. Despite the role of GPCR signaling in health and disease, the molecular mechanisms governing GPCR signaling remain poorly understanding. Classically, GPCR signaling is tightly regulated by GPCR kinases and β-arrestins, which act in a concerted fashion to govern GPCR desensitization and also GPCR trafficking. Ubiquitination has now emerged as an important posttranslational modification that has multiple roles, either directly or indirectly, in governing GPCR trafficking. Recent studies have revealed a mechanistic link between GPCR phosphorylation, β-arrestins, and ubiquitination. Here, we review recent developments in our understanding of how ubiquitin regulates GPCR trafficking within the endocytic pathway.
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Affiliation(s)
- Justine E Kennedy
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Health Sciences Division, Maywood, Illinois, USA
| | - Adriano Marchese
- Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Health Sciences Division, Maywood, Illinois, USA.
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Bishop P, Rubin P, Thomson AR, Rocca D, Henley JM. The ubiquitin C-terminal hydrolase L1 (UCH-L1) C terminus plays a key role in protein stability, but its farnesylation is not required for membrane association in primary neurons. J Biol Chem 2014; 289:36140-9. [PMID: 25326379 PMCID: PMC4276877 DOI: 10.1074/jbc.m114.557124] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ubiquitin C-terminal hydrolase L1 (UCH-L1) is a deubiquitinating enzyme that is highly expressed in neurons. A possible role for UCH-L1 in neurodegeneration has been highlighted because of its presence in Lewy bodies associated with Parkinson disease and neurofibrillary tangles observed in Alzheimer disease. UCH-L1 exists in two forms in neurons, a soluble cytoplasmic form (UCH-L1(C)) and a membrane-associated form (UCH-L1(M)). Alzheimer brains show reduced levels of soluble UCH-L1(C) correlating with the formation of UCH-L1-immunoreactive tau tangles, whereas UCH-L1(M) has been implicated in α-synuclein dysfunction. Given these reports of divergent roles, we investigated the properties of UCH-L1 membrane association. Surprisingly, our results indicate that UCH-L1 does not partition to the membrane in the cultured cell lines we tested. Furthermore, in primary cultured neurons, a proportion of UCH-L1(M) does partition to the membrane, but, contrary to a previous report, this does not require farnesylation. Deletion of the four C-terminal residues caused the loss of protein solubility, abrogation of substrate binding, increased cell death, and an abnormal intracellular distribution, consistent with protein dysfunction and aggregation. These data indicate that UCH-L1 is differently processed in neurons compared with clonal cell lines and that farnesylation does not account for the membrane association in neurons.
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Affiliation(s)
- Paul Bishop
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Philip Rubin
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Andrew R Thomson
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Dan Rocca
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M Henley
- From the School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
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Burmakina S, Geng Y, Chen Y, Fan QR. Heterodimeric coiled-coil interactions of human GABAB receptor. Proc Natl Acad Sci U S A 2014; 111:6958-63. [PMID: 24778228 PMCID: PMC4024898 DOI: 10.1073/pnas.1400081111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Metabotropic GABAB receptor is a G protein-coupled receptor that mediates inhibitory neurotransmission in the CNS. It functions as an obligatory heterodimer of GABAB receptor 1 (GBR1) and GABAB receptor 2 (GBR2) subunits. The association between GBR1 and GBR2 masks an endoplasmic reticulum (ER) retention signal in the cytoplasmic region of GBR1 and facilitates cell surface expression of both subunits. Here, we present, to our knowledge, the first crystal structure of an intracellular coiled-coil heterodimer of human GABAB receptor. We found that polar interactions buried within the hydrophobic core determine the specificity of heterodimer pairing. Disruption of the hydrophobic coiled-coil interface with single mutations in either subunit impairs surface expression of GBR1, confirming that the coiled-coil interaction is required to inactivate the adjacent ER retention signal of GBR1. The coiled-coil assembly buries an internalization motif of GBR1 at the heterodimer interface. The ER retention signal of GBR1 is not part of the core coiled-coil structure, suggesting that it is sterically shielded by GBR2 upon heterodimer formation.
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Affiliation(s)
| | | | | | - Qing R Fan
- Departments of Pharmacology andPathology and Cell Biology, Columbia University, New York, NY 10032
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Kantamneni S, Gonzàlez-Gonzàlez IM, Luo J, Cimarosti H, Jacobs SC, Jaafari N, Henley JM. Differential regulation of GABAB receptor trafficking by different modes of N-methyl-D-aspartate (NMDA) receptor signaling. J Biol Chem 2014; 289:6681-6694. [PMID: 24425870 PMCID: PMC3945329 DOI: 10.1074/jbc.m113.487348] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 12/24/2013] [Indexed: 12/31/2022] Open
Abstract
Inhibitory GABAB receptors (GABABRs) can down-regulate most excitatory synapses in the CNS by reducing postsynaptic excitability. Functional GABABRs are heterodimers of GABAB1 and GABAB2 subunits and here we show that the trafficking and surface expression of GABABRs is differentially regulated by synaptic or pathophysiological activation of NMDA receptors (NMDARs). Activation of synaptic NMDARs using a chemLTP protocol increases GABABR recycling and surface expression. In contrast, excitotoxic global activation of synaptic and extrasynaptic NMDARs by bath application of NMDA causes the loss of surface GABABRs. Intriguingly, exposing neurons to extreme metabolic stress using oxygen/glucose deprivation (OGD) increases GABAB1 but decreases GABAB2 surface expression. The increase in surface GABAB1 involves enhanced recycling and is blocked by the NMDAR antagonist AP5. The decrease in surface GABAB2 is also blocked by AP5 and by inhibiting degradation pathways. These results indicate that NMDAR activity is critical in GABABR trafficking and function and that the individual subunits can be separately controlled to regulate neuronal responsiveness and survival.
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Affiliation(s)
- Sriharsha Kantamneni
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
| | | | - Jia Luo
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Helena Cimarosti
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Susan C Jacobs
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Nadia Jaafari
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom
| | - Jeremy M Henley
- School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, United Kingdom.
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Receptor trafficking and the regulation of synaptic plasticity by SUMO. Neuromolecular Med 2013; 15:692-706. [PMID: 23934328 DOI: 10.1007/s12017-013-8253-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 07/25/2013] [Indexed: 12/18/2022]
Abstract
Timely and efficient information transfer at synapses is fundamental to brain function. Synapses are highly dynamic structures that exhibit long-lasting activity-dependent alterations to their structure and transmission efficiency, a phenomenon termed synaptic plasticity. These changes, which occur through alterations in presynaptic release or in the trafficking of postsynaptic receptor proteins, underpin the formation and stabilisation of neural circuits during brain development, and encode, process and store information essential for learning, memory and cognition. In recent years, it has emerged that the ubiquitin-like posttranslational modification SUMOylation is an important mediator of several aspects of neuronal and synaptic function. Through orchestrating synapse formation, presynaptic release and the trafficking of postsynaptic receptor proteins during forms of synaptic plasticity such as long-term potentiation, long-term depression and homeostatic scaling, SUMOylation is being increasingly appreciated to play a central role in neurotransmission. In this review, we outline key discoveries in this relatively new field, provide an update on recent progress regarding the targets and consequences of protein SUMOylation in synaptic function and plasticity, and highlight key outstanding questions regarding the roles of protein SUMOylation in the brain.
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Baloucoune GA, Chun L, Zhang W, Xu C, Huang S, Sun Q, Wang Y, Tu H, Liu J. GABAB receptor subunit GB1 at the cell surface independently activates ERK1/2 through IGF-1R transactivation. PLoS One 2012; 7:e39698. [PMID: 22761875 PMCID: PMC3386256 DOI: 10.1371/journal.pone.0039698] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 05/29/2012] [Indexed: 12/24/2022] Open
Abstract
Background Functional GABAB receptor is believed to require hetero-dimerization between GABAB1 (GB1) and GABAB2 (GB2) subunits. The GB1 extracellular domain is required for ligand binding, and the GB2 trans-membrane domain is responsible for coupling to G proteins. Atypical GABAB receptor responses observed in GB2-deficient mice suggested that GB1 may have activity in the absence of GB2. However the underlying mechanisms remain poorly characterized. Methodology/Principal Findings Here, by using cells overexpressing a GB1 mutant (GB1asa) with the ability to translocate to the cell surface in the absence of GB2, we show that GABAB receptor agonists, such as GABA and Baclofen, can induce ERK1/2 phosphorylation in the absence of GB2. Furthermore, we demonstrate that GB1asa induces ERK1/2 phosphorylation through Gi/o proteins and PLC dependent IGF-1R transactivation. Conclusions/Significance Our data suggest that GB1 may form a functional receptor at the cell surface in the absence of GB2.
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Affiliation(s)
- Guillaume A. Baloucoune
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Lei Chun
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Wenhua Zhang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Chanjuan Xu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Siluo Huang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Qian Sun
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yunyun Wang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Haijun Tu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jianfeng Liu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- * E-mail:
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Craig TJ, Henley JM. Protein SUMOylation in spine structure and function. Curr Opin Neurobiol 2012; 22:480-7. [PMID: 22054923 PMCID: PMC3379963 DOI: 10.1016/j.conb.2011.10.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 10/18/2011] [Accepted: 10/18/2011] [Indexed: 11/18/2022]
Abstract
The active regulation of spine structure and function is of fundamental importance for information storage in the brain. Many proteins involved in spine development and activity-dependent remodelling are potential or validated substrates for modification by the Small Ubiquitin-like Modifier (SUMO). The functional consequences of neuronal protein SUMOylation appear diverse and, in many cases, have not yet been determined. However, for several proteins SUMOylation has been shown to be a key regulator, which has a profound impact on spine dynamics and protein trafficking and function. Here we provide an overview of neuronal SUMOylation and discuss how greater understanding of this relatively recently discovered posttranslational modification will provide insight into the complexity of protein interactions that control synaptic activity and dysfunction.
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Affiliation(s)
- Tim J Craig
- MRC Centre for Synaptic Plasticity, School of Biochemistry Medical Sciences Building, University of Bristol, University Walk, Bristol, BS8 1TD, UK
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17
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Craig TJ, Jaafari N, Petrovic MM, Jacobs SC, Rubin PP, Mellor JR, Henley JM. Homeostatic synaptic scaling is regulated by protein SUMOylation. J Biol Chem 2012; 287:22781-8. [PMID: 22582390 PMCID: PMC3391081 DOI: 10.1074/jbc.m112.356337] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Homeostatic scaling allows neurons to alter synaptic transmission to compensate for changes in network activity. Here, we show that suppression of network activity with tetrodotoxin, which increases surface expression of AMPA receptors (AMPARs), dramatically reduces levels of the deSUMOylating (where SUMO is small ubiquitin-like modifier) enzyme SENP1, leading to a consequent increase in protein SUMOylation. Overexpression of the catalytic domain of SENP1 prevents this scaling effect, and we identify Arc as a SUMO substrate involved in the tetrodotoxin-induced increase in AMPAR surface expression. Thus, protein SUMOylation plays an important and previously unsuspected role in synaptic trafficking of AMPARs that underlies homeostatic scaling.
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Affiliation(s)
- Tim J Craig
- Medical Research Council Centre for Synaptic Plasticity, School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom
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18
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Kuzirian MS, Paradis S. Emerging themes in GABAergic synapse development. Prog Neurobiol 2011; 95:68-87. [PMID: 21798307 DOI: 10.1016/j.pneurobio.2011.07.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 06/30/2011] [Accepted: 07/03/2011] [Indexed: 12/25/2022]
Abstract
Glutamatergic synapse development has been rigorously investigated for the past two decades at both the molecular and cell biological level yet a comparable intensity of investigation into the cellular and molecular mechanisms of GABAergic synapse development has been lacking until relatively recently. This review will provide a detailed overview of the current understanding of GABAergic synapse development with a particular emphasis on assembly of synaptic components, molecular mechanisms of synaptic development, and a subset of human disorders which manifest when GABAergic synapse development is disrupted. An unexpected and emerging theme from these studies is that glutamatergic and GABAergic synapse development share a number of overlapping molecular and cell biological mechanisms that will be emphasized in this review.
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Affiliation(s)
- Marissa S Kuzirian
- Brandeis Univeristy, Department of Biology, National Center for Behavioral Genomics, Volen Center for Complex Systems, Waltham, MA 02453, USA
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19
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Activity-dependent SUMOylation of the brain-specific scaffolding protein GISP. Biochem Biophys Res Commun 2011; 409:657-62. [PMID: 21616059 DOI: 10.1016/j.bbrc.2011.05.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 05/11/2011] [Indexed: 11/21/2022]
Abstract
G-protein coupled receptor interacting scaffold protein (GISP) is a multi-domain, brain-specific protein derived from the A-kinase anchoring protein (AKAP)-9 gene. Using yeast two-hybrid screens to identify GISP interacting proteins we isolated the SUMO conjugating enzyme Ubc9. GISP interacts with Ubc9 in vitro, in heterologous cells and in neurons. SUMOylation is a post-translational modification in which the small protein SUMO is covalently conjugated to target proteins, modulating their function. Consistent with its interaction with Ubc9, we show that GISP is SUMOylated by both SUMO-1 and SUMO-2 in both in vitro SUMOylation assays and in mammalian cells. Intriguingly, SUMOylation of GISP in neurons occurs in an activity-dependent manner in response to chemical LTP. These data suggest that GISP is a novel neuronal SUMO substrate whose SUMOylation status is modulated by neuronal activity.
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20
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Chalifoux JR, Carter AG. GABAB receptor modulation of synaptic function. Curr Opin Neurobiol 2011; 21:339-44. [PMID: 21376567 DOI: 10.1016/j.conb.2011.02.004] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 02/01/2011] [Indexed: 01/17/2023]
Abstract
Neuromodulators have complex effects on both the presynaptic release and postsynaptic detection of neurotransmitters. Here we describe recent advances in our understanding of synaptic modulation by metabotropic GABAB receptors. By inhibiting multivesicular release from the presynaptic terminal, these receptors decrease the synaptic glutamate signal. GABAB receptors also inhibit the Ca2+ permeability of NMDA receptors to decrease Ca2+ signals in postsynaptic spines. These new findings highlight the importance of GABAB receptors in regulating many aspects of synaptic transmission. They also point to novel questions about the spatiotemporal dynamics and sources of synaptic modulation in the brain.
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Affiliation(s)
- Jason R Chalifoux
- Center for Neural Science, New York University, 4 Washington Place, New York, NY 10003, United States
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21
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Zunner D, Deschermeier C, Kornau HC. GABA(B) receptor subunit 1 binds to proteins affected in 22q11 deletion syndrome. Biochem Biophys Res Commun 2010; 393:185-9. [PMID: 20036641 DOI: 10.1016/j.bbrc.2009.12.120] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 12/20/2009] [Indexed: 01/08/2023]
Abstract
GABA(B) receptors mediate slow inhibitory effects of the neurotransmitter gamma-aminobutyric acid (GABA) on synaptic transmission in the central nervous system. They function as heterodimeric G-protein-coupled receptors composed of the seven-transmembrane domain proteins GABA(B1) and GABA(B2), which are linked through a coiled-coil interaction. The ligand-binding subunit GABA(B1) is at first retained in the endoplasmic reticulum and is transported to the cell surface only upon assembly with GABA(B2). Here, we report that GABA(B1), via the coiled-coil domain, can also bind to soluble proteins of unknown function, that are affected in 22q11 deletion/DiGeorge syndrome and are therefore referred to as DiGeorge critical region 6 (DGCR6). In transfected neurons the GABA(B1)-DGCR6 association resulted in a redistribution of both proteins into intracellular clusters. Furthermore, the C-terminus of GABA(B2) interfered with the novel interaction, consistent with heterodimer formation overriding transient DGCR6-binding to GABA(B1). Thus, sequential coiled-coil interactions may direct GABA(B1) into functional receptors.
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Affiliation(s)
- Dagmar Zunner
- Center for Molecular Neurobiology, University of Hamburg, Germany
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22
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Direct interaction of GABAB receptors with M2 muscarinic receptors enhances muscarinic signaling. J Neurosci 2010; 29:15796-809. [PMID: 20016095 DOI: 10.1523/jneurosci.4103-09.2009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Downregulation of G-protein-coupled receptors (GPCRs) provides an important mechanism for reducing neurotransmitter signaling during sustained stimulation. Chronic stimulation of M(2) muscarinic receptors (M(2)Rs) causes internalization of M(2)R and G-protein-activated inwardly rectifying potassium (GIRK) channels in neuronal PC12 cells, resulting in loss of function. Here, we show that coexpression of GABA(B) R2 receptors (GBR2s) rescues both surface expression and function of M(2)R, including M(2)R-induced activation of GIRKs and inhibition of cAMP production. GBR2 showed significant association with M(2)R at the plasma membrane but not other GPCRs (M(1)R, mu-opioid receptor), as detected by fluorescence resonance energy transfer measured with total internal reflection fluorescence microscopy. Unique regions of the proximal C-terminal domains of GBR2 and M(2)R mediate specific binding between M(2)R and GBR2. In the brain, GBR2, but not GBR1, biochemically coprecipitates with M(2)R and overlaps with M(2)R expression in cortical neurons. This novel heteromeric association between M(2)R and GBR2 provides a possible mechanism for altering muscarinic signaling in the brain and represents a previously unrecognized role for GBR2.
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23
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Benke D. Mechanisms of GABAB receptor exocytosis, endocytosis, and degradation. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:93-111. [PMID: 20655479 DOI: 10.1016/s1054-3589(10)58004-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GABA(B) receptors belong to the family of G-protein-coupled receptors, which mediate slow inhibitory neurotransmission in the central nervous system. They are promising drug targets for a variety of neurological disorders and play important functions in regulating synaptic plasticity. Signaling strength is critically dependent on the availability of the receptors at the cell surface. Several distinct highly regulated trafficking mechanisms ensure the presence of adequate receptor numbers in the plasma membrane. The rate of exocytosis of newly synthesized receptors from the endoplasmic reticulum via the Golgi apparatus to the cell surface as well as the rates of their endocytosis and degradation determines the retention time of receptors at the cell surface. This chapter focuses on the recently emerged mechanisms of GABA(B) receptor exocytosis, endocytosis, recycling, and degradation.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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24
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Genetic factors and epigenetic factors for autism: endoplasmic reticulum stress and impaired synaptic function. Cell Biol Int 2009; 34:13-9. [PMID: 20001973 DOI: 10.1042/cbi20090250] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The molecular pathogenesis of ASD (autism spectrum disorder), one of the heritable neurodevelopmental disorders, is not well understood, although over 15 autistic-susceptible gene loci have been extensively studied. A major issue is whether the proteins that these candidate genes encode are involved in general function and signal transduction. Several mutations in genes encoding synaptic adhesion molecules such as neuroligin, neurexin, CNTNAP (contactin-associated protein) and CADM1 (cell-adhesion molecule 1) found in ASD suggest that impaired synaptic function is the underlying pathogenesis. However, knockout mouse models of these mutations do not show all of the autism-related symptoms, suggesting that gain-of-function in addition to loss-of-function arising from these mutations may be associated with ASD pathogenesis. Another finding is that family members with a given mutation frequently do not manifest autistic symptoms, which possibly may be because of gender effects, dominance theory and environmental factors, including hormones and stress. Thus epigenetic factors complicate our understanding of the relationship between these mutated genes and ASD pathogenesis. We focus in the present review on findings that ER (endoplasmic reticulum) stress arising from these mutations causes a trafficking disorder of synaptic receptors, such as GABA (gamma-aminobutyric acid) B-receptors, and leads to their impaired synaptic function and signal transduction. In the present review we propose a hypothesis that ASD pathogenesis is linked not only to loss-of-function but also to gain-of-function, with an ER stress response to unfolded proteins under the influence of epigenetic factors.
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25
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Pooler AM, Gray AG, McIlhinney RAJ. Identification of a novel region of the GABA(B2) C-terminus that regulates surface expression and neuronal targeting of the GABA(B) receptor. Eur J Neurosci 2009; 29:869-78. [PMID: 19291218 DOI: 10.1111/j.1460-9568.2009.06636.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
GABA(B) is a G protein-coupled receptor composed of two subunits, GABA(B1) and GABA(B2). GABA(B1) contains an endoplasmic reticulum-retention sequence and is trafficked to the cell surface only in association with GABA(B2). To determine whether the C-terminus of GABA(B2) regulates GABA(B) trafficking, we constructed forms of GABA(B2) with various C-terminal truncations and examined their surface expression. Truncation of GABA(B2) after residue 841 significantly reduced surface expression of both the subunit and the heterodimerized receptor. Turnover of the Delta841 construct, however, did not differ from that of full-length GABA(B2). To determine whether the C-terminus of GABA(B2) might target GABA(B) to neurites, cultured hippocampal neurons were transfected with the truncated GABA(B2) constructs. Truncation of GABA(B2) at residue 841 resulted in primarily somatic localization; furthermore, axonal trafficking of this construct was significantly more restricted than dendritic trafficking. Finally, to biochemically assess trafficking of the truncated GABA(B2) constructs, we digested transfected HEK293 cell lysates with endoglycosidase H. When GABA(B2) was truncated at residue 841, it became sensitive to digestion by this enzyme, indicating incomplete trafficking. Taken together, these data show that the region of the GABA(B2) C-terminus between residues 841 and 862 is important for regulating forward trafficking and neuronal targeting of the GABA(B) receptor.
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Affiliation(s)
- A M Pooler
- Medical Research Council, Anatomical Neuropharmacology Unit, Mansfield Road, Oxford OX13TH, UK
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26
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Kantamneni S, Holman D, Wilkinson KA, Nishimune A, Henley JM. GISP increases neurotransmitter receptor stability by down-regulating ESCRT-mediated lysosomal degradation. Neurosci Lett 2009; 452:106-10. [PMID: 19154774 DOI: 10.1016/j.neulet.2009.01.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2008] [Revised: 12/30/2008] [Accepted: 01/07/2009] [Indexed: 11/26/2022]
Abstract
GPCR interacting scaffold protein (GISP) is a multi-domain brain-specific scaffold protein that can regulate GABA(B) receptor complexes by both enhancing their surface expression and by inhibiting their lysosomal degradation. GISP retards degradation of GABA(B) receptors through its interaction with tumour susceptibility gene 101 (TSG101), a member of the endosomal sorting complex required for transport (ESCRT) lysosomal sorting machinery. We show that in addition to GABA(B), GISP exerts a more general role to increase the steady-state levels of several neurotransmitter receptors. Further, GISP delays TSG101-dependent agonist-induced EGFR down-regulation in human embryonic kidney (HEK) 293 cells whereas a mutant GISP lacking the TSG101 binding domain has no effect. These data suggest that GISP acts as a negative regulator of TSG101-dependent lysosomal degradation and plays an important role in determining the availability of neurotransmitter receptors.
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Affiliation(s)
- Sriharsha Kantamneni
- MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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27
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Richer M, David M, Villeneuve LR, Trieu P, Ethier N, Pétrin D, Mamarbachi AM, Hébert TE. GABA-B(1) receptors are coupled to the ERK1/2 MAP kinase pathway in the absence of GABA-B(2) subunits. J Mol Neurosci 2008; 38:67-79. [PMID: 19052921 DOI: 10.1007/s12031-008-9163-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 11/06/2008] [Indexed: 01/22/2023]
Abstract
In the current model of gamma-aminobutyric acid (GABA) B receptor function, there is a requirement for GABA-B(1/2) heterodimerisation for targetting to the cell surface. However, different lines of evidence suggest that the GABA-B(1) subunit can form a functional receptor in the absence of GABA-B(2). We observed coupling of endogenous GABA-B(1) receptors in the DI-TNC1 glial cell line to the ERK pathway in response to baclofen even though these cells do not express GABA-B(2). GABA-B(1A) receptors were also able to mediate a rapid, transient, and dose-dependent activation of the ERK1/2 MAP kinase pathway when transfected alone into HEK 293 cells. The response was abolished by G(i/o) and MEK inhibition, potentiated by inhibitors of phospholipase C and protein kinase C and did not involve PI-3-kinase activity. Finally, using bioluminescence resonance energy transfer and co-immunoprecipitation, we show the existence of homodimeric GABA-B(1A) receptors in transfected HEK293 cells. Altogether, our observations show that GABA-B(1A) receptors are able to activate the ERK1/2 pathway despite the absence of surface targetting partner GABA-B(2) in both HEK 293 cells and the DI-TNC1 cell line.
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Affiliation(s)
- Maxime Richer
- Département de biochimie and Groupe de recherche universitaire sur le médicament (GRUM), Université de Montréal, Montréal, Québec, Canada
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28
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Kantamneni S, Holman D, Wilkinson KA, Corrêa SAL, Feligioni M, Ogden S, Fraser W, Nishimune A, Henley JM. GISP binding to TSG101 increases GABA receptor stability by down-regulating ESCRT-mediated lysosomal degradation. J Neurochem 2008. [PMID: 18643869 DOI: 10.1111/j.1471-4159.2008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The neuron-specific G protein-coupled receptor interacting scaffold protein (GISP) is a multidomain, brain-specific protein derived from the A-kinase anchoring protein-9 gene. We originally isolated GISP as an interacting partner for the GABA(B) receptor subunit GABA(B1). Here, we show that the protein tumour susceptibility gene 101 (TSG101), an integral component of the endosomal sorting machinery that targets membrane proteins for lysosomal degradation, also interacts with GISP. TSG101 co-immunoprecipitates with GISP from adult rat brain, and using GST pull-downs, we identified that the eighth coiled-coiled region of GISP is critical for TSG101 association. Intriguingly, although there is no direct interaction between GISP and the GABA(B2) subunit, their co-expression in HEK293 cells increases levels of GABA(B2). GISP also inhibits TSG101-dependent GABA(B2) down-regulation in human embryonic kidney 293 cells whereas over-expression of a mutant GISP lacking the TSG101 binding domain has no effect on GABA(B2) degradation. These data suggest that GISP can function as a negative regulator of TSG101-dependent lysosomal degradation of transmembrane proteins in neurons to promote receptor stability.
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Affiliation(s)
- Sriharsha Kantamneni
- Department of Anatomy, MRC Centre for Synaptic Plasticity, School of Medical Sciences, University of Bristol, Bristol, UK
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29
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Kantamneni S, Holman D, Wilkinson KA, Corrêa SAL, Feligioni M, Ogden S, Fraser W, Nishimune A, Henley JM. GISP binding to TSG101 increases GABA receptor stability by down-regulating ESCRT-mediated lysosomal degradation. J Neurochem 2008; 107:86-95. [PMID: 18643869 DOI: 10.1111/j.1471-4159.2008.05580.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neuron-specific G protein-coupled receptor interacting scaffold protein (GISP) is a multidomain, brain-specific protein derived from the A-kinase anchoring protein-9 gene. We originally isolated GISP as an interacting partner for the GABA(B) receptor subunit GABA(B1). Here, we show that the protein tumour susceptibility gene 101 (TSG101), an integral component of the endosomal sorting machinery that targets membrane proteins for lysosomal degradation, also interacts with GISP. TSG101 co-immunoprecipitates with GISP from adult rat brain, and using GST pull-downs, we identified that the eighth coiled-coiled region of GISP is critical for TSG101 association. Intriguingly, although there is no direct interaction between GISP and the GABA(B2) subunit, their co-expression in HEK293 cells increases levels of GABA(B2). GISP also inhibits TSG101-dependent GABA(B2) down-regulation in human embryonic kidney 293 cells whereas over-expression of a mutant GISP lacking the TSG101 binding domain has no effect on GABA(B2) degradation. These data suggest that GISP can function as a negative regulator of TSG101-dependent lysosomal degradation of transmembrane proteins in neurons to promote receptor stability.
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Affiliation(s)
- Sriharsha Kantamneni
- Department of Anatomy, MRC Centre for Synaptic Plasticity, School of Medical Sciences, University of Bristol, Bristol, UK
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30
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Kantamneni S, Holman D, Wilkinson KA, Corrêa SAL, Feligioni M, Ogden S, Fraser W, Nishimune A, Henley JM. GISP binding to TSG101 increases GABA receptor stability by down-regulating ESCRT-mediated lysosomal degradation. J Neurochem 2008. [PMID: 18643869 DOI: 10.1111/j.1471-4159.2008.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neuron-specific G protein-coupled receptor interacting scaffold protein (GISP) is a multidomain, brain-specific protein derived from the A-kinase anchoring protein-9 gene. We originally isolated GISP as an interacting partner for the GABA(B) receptor subunit GABA(B1). Here, we show that the protein tumour susceptibility gene 101 (TSG101), an integral component of the endosomal sorting machinery that targets membrane proteins for lysosomal degradation, also interacts with GISP. TSG101 co-immunoprecipitates with GISP from adult rat brain, and using GST pull-downs, we identified that the eighth coiled-coiled region of GISP is critical for TSG101 association. Intriguingly, although there is no direct interaction between GISP and the GABA(B2) subunit, their co-expression in HEK293 cells increases levels of GABA(B2). GISP also inhibits TSG101-dependent GABA(B2) down-regulation in human embryonic kidney 293 cells whereas over-expression of a mutant GISP lacking the TSG101 binding domain has no effect on GABA(B2) degradation. These data suggest that GISP can function as a negative regulator of TSG101-dependent lysosomal degradation of transmembrane proteins in neurons to promote receptor stability.
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Affiliation(s)
- Sriharsha Kantamneni
- Department of Anatomy, MRC Centre for Synaptic Plasticity, School of Medical Sciences, University of Bristol, Bristol, UK
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31
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Wilkinson KA, Nishimune A, Henley JM. Analysis of SUMO-1 modification of neuronal proteins containing consensus SUMOylation motifs. Neurosci Lett 2008; 436:239-44. [PMID: 18400391 DOI: 10.1016/j.neulet.2008.03.029] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 03/10/2008] [Accepted: 03/12/2008] [Indexed: 12/31/2022]
Abstract
SUMOylation is emerging as an important mechanism for modulating protein function in many cell types. A large variety of proteins have been proposed as SUMO targets based on the presence of a consensus SUMOylation core motif (Psi-K-x-D/E). In neurons these include multiple synaptic proteins but it has not been established whether proteins carrying this motif are SUMOylated either in vitro or in vivo. Here we use a bacterial SUMOylation assay to systematically test for SUMO-1 modification of a selection of neuronal proteins containing one or more amino acid sequences predicted as high-probability SUMOylation sites in computer-based searches. Of the 39 proteins analysed only 14 sites were posttranslationally modified by SUMO-1, including the group III metabotropic glutamate receptors and the kainate receptor subunit GluR7. These results identify new candidate proteins that may be involved in the SUMO regulation of synaptic activity and also demonstrate that the presence of the Psi-K-x-D/E motif is not sufficient to indicate that a protein can be SUMOylated in this bacterial system.
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Affiliation(s)
- Kevin A Wilkinson
- MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University of Bristol, University Walk, Bristol BS81TD, UK
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