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Xie MX, Rao JH, Tian XY, Liu JK, Li X, Chen ZY, Cao Y, Chen AN, Shu HH, Zhang XL. ATF4 inhibits TRPV4 function and controls itch perception in rodents and nonhuman primates. Pain 2024:00006396-990000000-00537. [PMID: 38422489 DOI: 10.1097/j.pain.0000000000003189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 01/03/2024] [Indexed: 03/02/2024]
Abstract
ABSTRACT Acute and chronic itch are prevalent and incapacitating, yet the neural mechanisms underlying both acute and chronic itch are just starting to be unraveled. Activated transcription factor 4 (ATF4) belongs to the ATF/CREB transcription factor family and primarily participates in the regulation of gene transcription. Our previous study has demonstrated that ATF4 is expressed in sensory neurons. Nevertheless, the role of ATF4 in itch sensation remains poorly understood. Here, we demonstrate that ATF4 plays a significant role in regulating itch sensation. The absence of ATF4 in dorsal root ganglion (DRG) neurons enhances the itch sensitivity of mice. Overexpression of ATF4 in sensory neurons significantly alleviates the acute and chronic pruritus in mice. Furthermore, ATF4 interacts with the transient receptor potential cation channel subfamily V member 4 (TRPV4) and inhibits its function without altering the expression or membrane trafficking of TRPV4 in sensory neurons. In addition, interference with ATF4 increases the itch sensitivity in nonhuman primates and enhances TRPV4 currents in nonhuman primates DRG neurons; ATF4 and TRPV4 also co-expresses in human sensory neurons. Our data demonstrate that ATF4 controls pruritus by regulating TRPV4 signaling through a nontranscriptional mechanism and identifies a potential new strategy for the treatment of pathological pruritus.
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Affiliation(s)
- Man-Xiu Xie
- Department of Anesthesiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Guangzhou, China
| | - Jun-Hua Rao
- Guangdong Key Laboratory of Animal Conservation and Resource Utilization, Guangdong Public Laboratory of Wild Animal Conservation and Utilization, Institute of Zoology, Guangdong Academy of Sciences, Guangzhou, China
| | - Xiao-Yu Tian
- Medical Research Institute, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
| | - Jin-Kun Liu
- Medical Research Institute, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
- Guangdong Cardiovascular Institute, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Guangzhou, China
| | - Xiao Li
- College of Food Science and Technology, Hainan University, Haikou, China
| | - Zi-Yi Chen
- Zhongshan School of Medicine of Sun Yat-sen University, Guangzhou, China
| | - Yan Cao
- College of Food Science and Technology, Hainan University, Haikou, China
| | - An-Nan Chen
- Zhongshan School of Medicine of Sun Yat-sen University, Guangzhou, China
| | - Hai-Hua Shu
- Department of Anesthesiology, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
| | - Xiao-Long Zhang
- Medical Research Institute, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, Guangzhou, China
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Chu YP, Jin LW, Wang LC, Ho PC, Wei WY, Tsai KJ. Transthyretin attenuates TDP-43 proteinopathy by autophagy activation via ATF4 in FTLD-TDP. Brain 2023; 146:2089-2106. [PMID: 36355566 PMCID: PMC10411944 DOI: 10.1093/brain/awac412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 10/01/2022] [Accepted: 10/06/2022] [Indexed: 11/12/2022] Open
Abstract
TAR DNA-binding protein-43 (TDP-43) proteinopathies are accompanied by the pathological hallmark of cytoplasmic inclusions in the neurodegenerative diseases, including frontal temporal lobar degeneration-TDP and amyotrophic lateral sclerosis. We found that transthyretin accumulates with TDP-43 cytoplasmic inclusions in frontal temporal lobar degeneration-TDP human patients and transgenic mice, in which transthyretin exhibits dramatic expression decline in elderly mice. The upregulation of transthyretin expression was demonstrated to facilitate the clearance of cytoplasmic TDP-43 inclusions through autophagy, in which transthyretin induces autophagy upregulation via ATF4. Of interest, transthyretin upregulated ATF4 expression and promoted ATF4 nuclear import, presenting physical interaction. Neuronal expression of transthyretin in frontal temporal lobar degeneration-TDP mice restored autophagy function and facilitated early soluble TDP-43 aggregates for autophagosome targeting, ameliorating neuropathology and behavioural deficits. Thus, transthyretin conducted two-way regulations by either inducing autophagy activation or escorting TDP-43 aggregates targeted autophagosomes, suggesting that transthyretin is a potential modulator therapy for neurological disorders caused by TDP-43 proteinopathy.
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Affiliation(s)
- Yuan-Ping Chu
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Lee-Way Jin
- Department of Pathology and Laboratory Medicine, UC Davis Medical Center, CA, USA
| | - Liang-Chao Wang
- Division of Neurosurgery, Department of Surgery, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Pei-Chuan Ho
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Yen Wei
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Kuen-Jer Tsai
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan
- Research Center of Clinical Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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Akyuz E, Koklu B, Uner A, Angelopoulou E, Paudel YN. Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy. J Neurosci Res 2021; 100:413-443. [PMID: 34713909 DOI: 10.1002/jnr.24985] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 09/23/2021] [Accepted: 10/01/2021] [Indexed: 01/29/2023]
Abstract
Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.
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Affiliation(s)
- Enes Akyuz
- Faculty of International Medicine, Department of Biophysics, University of Health Sciences, Istanbul, Turkey
| | - Betul Koklu
- Faculty of Medicine, Namık Kemal University, Tekirdağ, Turkey
| | - Arda Uner
- Faculty of Medicine, Yozgat Bozok University, Yozgat, Turkey
| | - Efthalia Angelopoulou
- Department of Biological Chemistry, Medical School, National and Kapodistrian University of Athens, Athens, Greece
| | - Yam Nath Paudel
- Neuropharmacology Research Strength, Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Bandar Sunway, Malaysia
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GABA B Receptor Chemistry and Pharmacology: Agonists, Antagonists, and Allosteric Modulators. Curr Top Behav Neurosci 2021; 52:81-118. [PMID: 34036555 DOI: 10.1007/7854_2021_232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The GABAB receptors are metabotropic G protein-coupled receptors (GPCRs) that mediate the actions of the primary inhibitory neurotransmitter, γ-aminobutyric acid (GABA). In the CNS, GABA plays an important role in behavior, learning and memory, cognition, and stress. GABA is also located throughout the gastrointestinal (GI) tract and is involved in the autonomic control of the intestine and esophageal reflex. Consequently, dysregulated GABAB receptor signaling is associated with neurological, mental health, and gastrointestinal disorders; hence, these receptors have been identified as key therapeutic targets and are the focus of multiple drug discovery efforts for indications such as muscle spasticity disorders, schizophrenia, pain, addiction, and gastroesophageal reflex disease (GERD). Numerous agonists, antagonists, and allosteric modulators of the GABAB receptor have been described; however, Lioresal® (Baclofen; β-(4-chlorophenyl)-γ-aminobutyric acid) is the only FDA-approved drug that selectively targets GABAB receptors in clinical use; undesirable side effects, such as sedation, muscle weakness, fatigue, cognitive deficits, seizures, tolerance and potential for abuse, limit their therapeutic use. Here, we review GABAB receptor chemistry and pharmacology, presenting orthosteric agonists, antagonists, and positive and negative allosteric modulators, and highlight the therapeutic potential of targeting GABAB receptor modulation for the treatment of various CNS and peripheral disorders.
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Bai X, Kirchhoff F, Scheller A. Oligodendroglial GABAergic Signaling: More Than Inhibition! Neurosci Bull 2021; 37:1039-1050. [PMID: 33928492 PMCID: PMC8275815 DOI: 10.1007/s12264-021-00693-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 11/22/2020] [Indexed: 12/12/2022] Open
Abstract
GABA is the main inhibitory neurotransmitter in the CNS acting at two distinct types of receptor: ligand-gated ionotropic GABAA receptors and G protein-coupled metabotropic GABAB receptors, thus mediating fast and slow inhibition of excitability at central synapses. GABAergic signal transmission has been intensively studied in neurons in contrast to oligodendrocytes and their precursors (OPCs), although the latter express both types of GABA receptor. Recent studies focusing on interneuron myelination and interneuron-OPC synapses have shed light on the importance of GABA signaling in the oligodendrocyte lineage. In this review, we start with a short summary on GABA itself and neuronal GABAergic signaling. Then, we elaborate on the physiological role of GABA receptors within the oligodendrocyte lineage and conclude with a description of these receptors as putative targets in treatments of CNS diseases.
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Affiliation(s)
- Xianshu Bai
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, 66421, Homburg, Germany
| | - Frank Kirchhoff
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, 66421, Homburg, Germany.
| | - Anja Scheller
- Molecular Physiology, Center for Integrative Physiology and Molecular Medicine (CIPMM), University of Saarland, 66421, Homburg, Germany
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Xie MX, Cao XY, Zeng WA, Lai RC, Guo L, Wang JC, Xiao YB, Zhang X, Chen D, Liu XG, Zhang XL. ATF4 selectively regulates heat nociception and contributes to kinesin-mediated TRPM3 trafficking. Nat Commun 2021; 12:1401. [PMID: 33658516 PMCID: PMC7930092 DOI: 10.1038/s41467-021-21731-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 02/09/2021] [Indexed: 12/30/2022] Open
Abstract
Effective treatments for patients suffering from heat hypersensitivity are lacking, mostly due to our limited understanding of the pathogenic mechanisms underlying this disorder. In the nervous system, activating transcription factor 4 (ATF4) is involved in the regulation of synaptic plasticity and memory formation. Here, we show that ATF4 plays an important role in heat nociception. Indeed, loss of ATF4 in mouse dorsal root ganglion (DRG) neurons selectively impairs heat sensitivity. Mechanistically, we show that ATF4 interacts with transient receptor potential cation channel subfamily M member-3 (TRPM3) and mediates the membrane trafficking of TRPM3 in DRG neurons in response to heat. Loss of ATF4 also significantly decreases the current and KIF17-mediated trafficking of TRPM3, suggesting that the KIF17/ATF4/TRPM3 complex is required for the neuronal response to heat stimuli. Our findings unveil the non-transcriptional role of ATF4 in the response to heat stimuli in DRG neurons.
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Affiliation(s)
- Man-Xiu Xie
- Department of Anesthesiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng East Road, Guangzhou, China
| | - Xian-Ying Cao
- College of Food Science and Technology, Hainan University, 58 Renmin Avenue, Haikou, China
- State Key Laboratory of Marine Resources Utilization of South China Sea, 58 Renmin Avenue, Haikou, China
| | - Wei-An Zeng
- Department of Anesthesiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng East Road, Guangzhou, China
| | - Ren-Chun Lai
- Department of Anesthesiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng East Road, Guangzhou, China
| | - Lan Guo
- College of Food Science and Technology, Hainan University, 58 Renmin Avenue, Haikou, China
| | - Jun-Chao Wang
- Department of Anesthesiology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng East Road, Guangzhou, China
| | - Yi-Bin Xiao
- Pain Research Center and Department of Physiology, Zhongshan School of Medicine of Sun Yat-sen University, 74 Zhongshan Road 2, Guangzhou, China
| | - Xi Zhang
- Pain Research Center and Department of Physiology, Zhongshan School of Medicine of Sun Yat-sen University, 74 Zhongshan Road 2, Guangzhou, China
| | - Di Chen
- College of Food Science and Technology, Hainan University, 58 Renmin Avenue, Haikou, China
| | - Xian-Guo Liu
- Pain Research Center and Department of Physiology, Zhongshan School of Medicine of Sun Yat-sen University, 74 Zhongshan Road 2, Guangzhou, China.
| | - Xiao-Long Zhang
- Medical Research Center of Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, 106 Zhongshan Rd. 2, Guangzhou, China.
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Boussicault L, Laffaire J, Schmitt P, Rinaudo P, Callizot N, Nabirotchkin S, Hajj R, Cohen D. Combination of acamprosate and baclofen (PXT864) as a potential new therapy for amyotrophic lateral sclerosis. J Neurosci Res 2020; 98:2435-2450. [PMID: 32815196 PMCID: PMC7693228 DOI: 10.1002/jnr.24714] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 07/16/2020] [Accepted: 07/25/2020] [Indexed: 12/11/2022]
Abstract
There is currently no therapy impacting the course of amyotrophic lateral sclerosis (ALS). The only approved treatments are riluzole and edaravone, but their efficacy is modest and short‐lasting, highlighting the need for innovative therapies. We previously demonstrated the ability of PXT864, a combination of low doses of acamprosate and baclofen, to synergistically restore cellular and behavioral activity in Alzheimer's and Parkinson's disease models. The overlapping genetic, molecular, and cellular characteristics of these neurodegenerative diseases supported investigating the effectiveness of PXT864 in ALS. As neuromuscular junction (NMJ) alterations is a key feature of ALS, the effects of PXT864 in primary neuron‐muscle cocultures injured by glutamate were studied. PXT864 significantly and synergistically preserved NMJ and motoneuron integrity following glutamate excitotoxicity. PXT864 added to riluzole significantly improved such protection. PXT864 activity was then assessed in primary cultures of motoneurons derived from SOD1G93A rat embryos. These motoneurons presented severe maturation defects that were significantly improved by PXT864. In this model, glutamate application induced an accumulation of TDP‐43 protein in the cytoplasm, a hallmark that was completely prevented by PXT864. The anti‐TDP‐43 aggregation effect was also confirmed in a cell line expressing TDP‐43 fused to GFP. These results demonstrate the value of PXT864 as a promising therapeutic strategy for the treatment of ALS.
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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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Seifikalhor M, Aliniaeifard S, Hassani B, Niknam V, Lastochkina O. Diverse role of γ-aminobutyric acid in dynamic plant cell responses. PLANT CELL REPORTS 2019; 38:847-867. [PMID: 30739138 DOI: 10.1007/s00299-019-02396-z] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/02/2019] [Indexed: 05/05/2023]
Abstract
Gamma-aminobutyric acid (GABA), a four-carbon non-protein amino acid, is found in most prokaryotic and eukaryotic organisms. Although, ample research into GABA has occurred in mammals as it is a major inhibitory neurotransmitter; in plants, a role for GABA has often been suggested as a metabolite that changes under stress rather than as a signal, as no receptor or motif for GABA binding was identified until recently and many aspects of its biological function (ranging from perception to function) remain to be answered. In this review, flexible properties of GABA in regulation of plant responses to various environmental biotic and abiotic stresses and its integration in plant growth and development either as a metabolite or a signaling molecule are discussed. We have elaborated on the role of GABA in stress adaptation (i.e., salinity, hypoxia/anoxia, drought, temperature, heavy metals, plant-insect interplay and ROS-related responses) and its contribution in non-stress-related biological pathways (i.e., involvement in plant-microbe interaction, contribution to the carbon and nitrogen metabolism and governing of signal transduction pathways). This review aims to represent the multifunctional contribution of GABA in various biological and physiological mechanisms under stress conditions; the objective is to review the current state of knowledge about GABA role beyond stress-related responses. Our effort is to place findings about GABA in an organized and broader context to highlight its shared metabolic and biologic functions in plants under variable conditions. This will provide potential modes of GABA crosstalk in dynamic plant cell responses.
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Affiliation(s)
- Maryam Seifikalhor
- Department of Plant Biology, Center of Excellence in Phylogeny of Living Organisms in Iran, School of Biology, College of Science, University of Tehran, Tehran, 14155, Iran
| | - Sasan Aliniaeifard
- Department of Horticulture, College of Aburaihan, University of Tehran, Tehran, Iran.
| | - Batool Hassani
- Department of Plant Sciences, Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, Iran
| | - Vahid Niknam
- Department of Plant Biology, Center of Excellence in Phylogeny of Living Organisms in Iran, School of Biology, College of Science, University of Tehran, Tehran, 14155, Iran
| | - Oksana Lastochkina
- Bashkir Research Institute of Agriculture, Russian Academy of Sciences, Ufa, Russia
- Institute of Biochemistry and Genetics, Russian Academy of Sciences, Ufa, Russia
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Activating Transcription Factor 4 (ATF4) Regulates Neuronal Activity by Controlling GABA BR Trafficking. J Neurosci 2018; 38:6102-6113. [PMID: 29875265 DOI: 10.1523/jneurosci.3350-17.2018] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 05/29/2018] [Accepted: 05/31/2018] [Indexed: 11/21/2022] Open
Abstract
Activating Transcription Factor 4 (ATF4) has been postulated as a key regulator of learning and memory. We previously reported that specific hippocampal ATF4 downregulation causes deficits in synaptic plasticity and memory and reduction of glutamatergic functionality. Here we extend our studies to address ATF4's role in neuronal excitability. We find that long-term ATF4 knockdown in cultured rat hippocampal neurons significantly increases the frequency of spontaneous action potentials. This effect is associated with decreased functionality of metabotropic GABAB receptors (GABABRs). Knocking down ATF4 results in significant reduction of GABABR-induced GIRK currents and increased mIPSC frequency. Furthermore, reducing ATF4 significantly decreases expression of membrane-exposed, but not total, GABABR 1a and 1b subunits, indicating that ATF4 regulates GABABR trafficking. In contrast, ATF4 knockdown has no effect on surface expression of GABABR2s, several GABABR-coupled ion channels or β2 and γ2 GABAARs. Pharmacologic manipulations confirmed the relationship between GABABR functionality and action potential frequency in our cultures. Specifically, the effects of ATF4 downregulation cited above are fully rescued by transcriptionally active, but not by transcriptionally inactive, shRNA-resistant, ATF4. We previously reported that ATF4 promotes stabilization of the actin-regulatory protein Cdc42 by a transcription-dependent mechanism. To test the hypothesis that this action underlies the mechanism by which ATF4 loss affects neuronal firing rates and GABABR trafficking, we downregulated Cdc42 and found that this phenocopies the effects of ATF4 knockdown on these properties. In conclusion, our data favor a model in which ATF4, by regulating Cdc42 expression, affects trafficking of GABABRs, which in turn modulates the excitability properties of neurons.SIGNIFICANCE STATEMENT GABAB receptors (GABABRs), the metabotropic receptors for the inhibitory neurotransmitter GABA, have crucial roles in controlling the firing rate of neurons. Deficits in trafficking/functionality of GABABRs have been linked to a variety of neurological and psychiatric conditions, including epilepsy, anxiety, depression, schizophrenia, addiction, and pain. Here we show that GABABRs trafficking is influenced by Activating Transcription Factor 4 (ATF4), a protein that has a pivotal role in hippocampal memory processes. We found that ATF4 downregulation in hippocampal neurons reduces membrane-bound GABABR levels and thereby increases intrinsic excitability. These effects are mediated by loss of the small GTPase Cdc42 following ATF4 downregulation. These findings reveal a critical role for ATF4 in regulating the modulation of neuronal excitability by GABABRs.
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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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12
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Wright R, Newey SE, Ilie A, Wefelmeyer W, Raimondo JV, Ginham R, Mcllhinney RAJ, Akerman CJ. Neuronal Chloride Regulation via KCC2 Is Modulated through a GABA B Receptor Protein Complex. J Neurosci 2017; 37:5447-5462. [PMID: 28450542 PMCID: PMC5452337 DOI: 10.1523/jneurosci.2164-16.2017] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 03/31/2017] [Accepted: 04/06/2017] [Indexed: 01/06/2023] Open
Abstract
GABAB receptors are G-protein-coupled receptors that mediate inhibitory synaptic actions through a series of downstream target proteins. It is increasingly appreciated that the GABAB receptor forms part of larger signaling complexes, which enable the receptor to mediate multiple different effects within neurons. Here we report that GABAB receptors can physically associate with the potassium-chloride cotransporter protein, KCC2, which sets the driving force for the chloride-permeable ionotropic GABAA receptor in mature neurons. Using biochemical, molecular, and functional studies in rodent hippocampus, we show that activation of GABAB receptors results in a decrease in KCC2 function, which is associated with a reduction in the protein at the cell surface. These findings reveal a novel "crosstalk" between the GABA receptor systems, which can be recruited under conditions of high GABA release and which could be important for the regulation of inhibitory synaptic transmission.SIGNIFICANCE STATEMENT Synaptic inhibition in the brain is mediated by ionotropic GABAA receptors (GABAARs) and metabotropic GABAB receptors (GABABRs). To fully appreciate the function and regulation of these neurotransmitter receptors, we must understand their interactions with other proteins. We describe a novel association between the GABABR and the potassium-chloride cotransporter protein, KCC2. This association is significant because KCC2 sets the intracellular chloride concentration found in mature neurons and thereby establishes the driving force for the chloride-permeable GABAAR. We demonstrate that GABABR activation can regulate KCC2 at the cell surface in a manner that alters intracellular chloride and the reversal potential for the GABAAR. Our data therefore support an additional mechanism by which GABABRs are able to modulate fast synaptic inhibition.
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Affiliation(s)
| | | | | | | | | | - Rachel Ginham
- Medical Research Council Anatomical Neuropharmacology Unit, University of Oxford, Oxford, OX1 3QT, United Kingdom
| | - R A Jeffrey Mcllhinney
- Medical Research Council Anatomical Neuropharmacology Unit, University of Oxford, Oxford, OX1 3QT, United Kingdom
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Sun Y, Huang P. Adenosine A2B Receptor: From Cell Biology to Human Diseases. Front Chem 2016; 4:37. [PMID: 27606311 PMCID: PMC4995213 DOI: 10.3389/fchem.2016.00037] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 08/11/2016] [Indexed: 12/26/2022] Open
Abstract
Extracellular adenosine is a ubiquitous signaling molecule that modulates a wide array of biological processes. Recently, significant advances have been made in our understanding of A2B adenosine receptor (A2BAR). In this review, we first summarize some of the general characteristics of A2BAR, and then we describe the multiple binding partners of the receptor, such as newly identified α-actinin-1 and p105, and discuss how these associated proteins could modulate A2BAR's functions, including certain seemingly paradoxical functions of the receptor. Growing evidence indicates a critical role of A2BAR in cancer, renal disease, and diabetes, in addition to its importance in the regulation of vascular diseases, and lung disease. Here, we also discuss the role of A2BAR in cancer, renal disease, and diabetes and the potential of the receptor as a target for treating these three diseases.
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Affiliation(s)
- Ying Sun
- Department of Biology, South University of Science and Technology of ChinaShenzhen, China; Shenzhen Key Laboratory of Cell Microenvironment, South University of Science and Technology of ChinaShenzhen, China
| | - Pingbo Huang
- Division of Life Science, Hong Kong University of Science and TechnologyHong Kong, China; Division of Biomedical Engineering, Hong Kong University of Science and TechnologyHong Kong, China; State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and TechnologyHong Kong, China
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14
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Korpi ER, den Hollander B, Farooq U, Vashchinkina E, Rajkumar R, Nutt DJ, Hyytiä P, Dawe GS. Mechanisms of Action and Persistent Neuroplasticity by Drugs of Abuse. Pharmacol Rev 2015; 67:872-1004. [DOI: 10.1124/pr.115.010967] [Citation(s) in RCA: 101] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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15
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Zhang Z, Zhang W, Huang S, Sun Q, Wang Y, Hu Y, Sun N, Zhang Y, Jiang Z, Minato N, Pin JP, Su L, Liu J. GABAB receptor promotes its own surface expression by recruiting a Rap1-dependent signaling cascade. J Cell Sci 2015; 128:2302-13. [DOI: 10.1242/jcs.167056] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 05/05/2015] [Indexed: 12/11/2022] Open
Abstract
ABSTRACT
G-protein-coupled receptors (GPCRs) are key players in cell signaling, and their cell surface expression is tightly regulated. For many GPCRs such as β2-AR (β2-adrenergic receptor), receptor activation leads to downregulation of receptor surface expression, a phenomenon that has been extensively characterized. By contrast, some other GPCRs, such as GABAB receptor, remain relatively stable at the cell surface even after prolonged agonist treatment; however, the underlying mechanisms are unclear. Here, we identify the small GTPase Rap1 as a key regulator for promoting GABAB receptor surface expression. Agonist stimulation of GABAB receptor signals through Gαi/o to inhibit Rap1GAPII (also known as Rap1GAP1b, an isoform of Rap1GAP1), thereby activating Rap1 (which has two isoforms, Rap1a and Rap1b) in cultured cerebellar granule neurons (CGNs). The active form of Rap1 is then recruited to GABAB receptor through physical interactions in CGNs. This Rap1-dependent signaling cascade promotes GABAB receptor surface expression by stimulating receptor recycling. Our results uncover a new mechanism regulating GPCR surface expression and also provide a potential explanation for the slow, long-lasting inhibitory action of GABA neurotransmitter.
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Affiliation(s)
- Zongyong Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Wenhua Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Siluo Huang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qian Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yunyun Wang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yongjian Hu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Ninghua Sun
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Yilei Zhang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Zhihua Jiang
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Nagahiro Minato
- Department of Immunology and Cell Biology, Kyoto University, Kyoto 606-8501, Japan
| | - Jean-Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS, UMR 5203, Université Montpellier 1 et 2, Montpellier cedex 5 34094, France
| | - Li Su
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jianfeng Liu
- Cellular Signaling Laboratory, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology and the Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan 430074, China
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16
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Degro CE, Kulik A, Booker SA, Vida I. Compartmental distribution of GABAB receptor-mediated currents along the somatodendritic axis of hippocampal principal cells. Front Synaptic Neurosci 2015; 7:6. [PMID: 25852540 PMCID: PMC4369648 DOI: 10.3389/fnsyn.2015.00006] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 02/15/2015] [Indexed: 02/02/2023] Open
Abstract
Activity of cortical principal cells is controlled by the GABAergic system providing inhibition in a compartmentalized manner along their somatodendritic axis. While GABAAR-mediated inhibitory synaptic transmission has been extensively characterized in hippocampal principal cells, little is known about the distribution of postsynaptic effects of GABABRs. In the present study, we have investigated the functional localization of GABABRs and their effector inwardly rectifying potassium (Kir3) channels by combining electrophysiological recordings in acute rat hippocampal slices, high-resolution immunoelectron microscopic analysis and single cell simulations. Pharmacologically isolated slow inhibitory postsynaptic currents were elicited in the three major hippocampal principal cell types by endogenous GABA released by electrical stimulation, photolysis of caged-GABA, as well as the canonical agonist baclofen, with the highest amplitudes observed in the CA3. Spatially restricted currents were assessed along the axis of principal cells by uncaging GABA in the different hippocampal layers. GABABR-mediated currents were present along the entire somatodendritic axis of principal cells, but non-uniformly distributed: largest currents and the highest conductance densities determined in the simulations were consistently found on the distal apical dendrites. Finally, immunocytochemical localization of GABABRs and Kir3 channels showed that distributions overlap but their densities diverge, particularly on the basal dendrites of pyramidal cells. GABABRs current amplitudes and the conductance densities correlated better with Kir3 density, suggesting a bottlenecking effect defined by the effector channel. These data demonstrate a compartmentalized distribution of the GABABR-Kir3 signaling cascade and suggest differential control of synaptic transmission, dendritic integration and synaptic plasticity at afferent pathways onto hippocampal principal cells.
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Affiliation(s)
- Claudius E Degro
- Institute for Integrative Neuroanatomy, Neurocure Cluster of Excellence, Charité Universitätsmedizin Berlin Germany
| | - Akos Kulik
- Institute for Physiology II, Bioss Centre for Biological Signalling Studies, University of Freiburg Freiburg Germany
| | - Sam A Booker
- Institute for Integrative Neuroanatomy, Neurocure Cluster of Excellence, Charité Universitätsmedizin Berlin Germany
| | - Imre Vida
- Institute for Integrative Neuroanatomy, Neurocure Cluster of Excellence, Charité Universitätsmedizin Berlin Germany
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17
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Popova E. GABAergic neurotransmission and retinal ganglion cell function. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2015; 201:261-83. [PMID: 25656810 DOI: 10.1007/s00359-015-0981-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 01/19/2015] [Accepted: 01/21/2015] [Indexed: 01/13/2023]
Abstract
Ganglion cells are the output retinal neurons that convey visual information to the brain. There are ~20 different types of ganglion cells, each encoding a specific aspect of the visual scene as spatial and temporal contrast, orientation, direction of movement, presence of looming stimuli; etc. Ganglion cell functioning depends on the intrinsic properties of ganglion cell's membrane as well as on the excitatory and inhibitory inputs that these cells receive from other retinal neurons. GABA is one of the most abundant inhibitory neurotransmitters in the retina. How it modulates the activity of different types of ganglion cells and what is its significance in extracting the basic features from visual scene are questions with fundamental importance in visual neuroscience. The present review summarizes current data concerning the types of membrane receptors that mediate GABA action in proximal retina; the effects of GABA and its antagonists on the ganglion cell light-evoked postsynaptic potentials and spike discharges; the action of GABAergic agents on centre-surround organization of the receptive fields and feature related ganglion cell activity. Special emphasis is put on the GABA action regarding the ON-OFF and sustained-transient ganglion cell dichotomy in both nonmammalian and mammalian retina.
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Affiliation(s)
- E Popova
- Department of Physiology, Medical Faculty, Medical University, 1431, Sofia, Bulgaria,
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18
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Liu J, Pasini S, Shelanski ML, Greene LA. Activating transcription factor 4 (ATF4) modulates post-synaptic development and dendritic spine morphology. Front Cell Neurosci 2014; 8:177. [PMID: 25071442 PMCID: PMC4075335 DOI: 10.3389/fncel.2014.00177] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 06/07/2014] [Indexed: 11/15/2022] Open
Abstract
The ubiquitously expressed activating transcription factor 4 (ATF4) has been variably reported to either promote or inhibit neuronal plasticity and memory. However, the potential cellular bases for these and other actions of ATF4 in brain are not well-defined. In this report, we focus on ATF4's role in post-synaptic synapse development and dendritic spine morphology. shRNA-mediated silencing of ATF4 significantly reduces the densities of PSD-95 and GluR1 puncta (presumed markers of excitatory synapses) in long-term cultures of cortical and hippocampal neurons. ATF4 knockdown also decreases the density of mushroom spines and increases formation of abnormally-long dendritic filopodia in such cultures. In vivo knockdown of ATF4 in adult mouse hippocampal neurons also reduces mushroom spine density. In contrast, ATF4 over-expression does not affect the densities of PSD-95 puncta or mushrooom spines. Regulation of synaptic puncta and spine densities by ATF4 requires its transcriptional activity and is mediated at least in part by indirectly controlling the stability and expression of the total and active forms of the actin regulatory protein Cdc42. In support of such a mechanism, ATF4 silencing decreases the half-life of Cdc42 in cultured cortical neurons from 31.5 to 18.5 h while knockdown of Cdc42, like ATF4 knockdown, reduces the densities of mushroom spines and PSD-95 puncta. Thus, ATF4 appears to participate in neuronal development and plasticity by regulating the post-synaptic development of synapses and dendritic mushroom spines via a mechanism that includes regulation of Cdc42 levels.
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Affiliation(s)
- Jin Liu
- Department of Pathology and Cell Biology, Columbia University Medical Center New York, NY, USA
| | - Silvia Pasini
- Department of Pathology and Cell Biology, Columbia University Medical Center New York, NY, USA
| | - Michael L Shelanski
- Department of Pathology and Cell Biology, Columbia University Medical Center New York, NY, USA
| | - Lloyd A Greene
- Department of Pathology and Cell Biology, Columbia University Medical Center New York, NY, USA
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19
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Bjordal M, Arquier N, Kniazeff J, Pin JP, Léopold P. Sensing of amino acids in a dopaminergic circuitry promotes rejection of an incomplete diet in Drosophila. Cell 2014; 156:510-21. [PMID: 24485457 DOI: 10.1016/j.cell.2013.12.024] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 08/07/2013] [Accepted: 11/15/2013] [Indexed: 01/18/2023]
Abstract
The brain is the central organizer of food intake, matching the quality and quantity of the food sources with organismal needs. To ensure appropriate amino acid balance, many species reject a diet lacking one or several essential amino acids (EAAs) and seek out a better food source. Here, we show that, in Drosophila larvae, this behavior relies on innate sensing of amino acids in dopaminergic (DA) neurons of the brain. We demonstrate that the amino acid sensor GCN2 acts upstream of GABA signaling in DA neurons to promote avoidance of the EAA-deficient diet. Using real-time calcium imaging in larval brains, we show that amino acid imbalance induces a rapid and reversible activation of three DA neurons that are necessary and sufficient for food rejection. Taken together, these data identify a central amino-acid-sensing mechanism operating in specific DA neurons and controlling food intake.
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Affiliation(s)
- Marianne Bjordal
- University of Nice-Sophia Antipolis, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; CNRS, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; INSERM, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France
| | - Nathalie Arquier
- University of Nice-Sophia Antipolis, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; CNRS, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; INSERM, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France
| | - Julie Kniazeff
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Université Montpellier 1 & 2, 34094 Montpellier, France
| | - Jean Philippe Pin
- Institut de Génomique Fonctionnelle, CNRS UMR5203, INSERM U661, Université Montpellier 1 & 2, 34094 Montpellier, France
| | - Pierre Léopold
- University of Nice-Sophia Antipolis, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; CNRS, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France; INSERM, Institute of Biology Valrose, Parc Valrose, 06108 Nice, France.
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20
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Hypothalamic eIF2α signaling regulates food intake. Cell Rep 2014; 6:438-44. [PMID: 24485657 DOI: 10.1016/j.celrep.2014.01.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 11/28/2013] [Accepted: 01/06/2014] [Indexed: 01/13/2023] Open
Abstract
The reversible phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α) is a highly conserved signal implicated in the cellular adaptation to numerous stresses such as the one caused by amino acid limitation. In response to dietary amino acid deficiency, the brain-specific activation of the eIF2α kinase GCN2 leads to food intake inhibition. We report here that GCN2 is rapidly activated in the mediobasal hypothalamus (MBH) after consumption of a leucine-deficient diet. Furthermore, knockdown of GCN2 in this particular area shows that MBH GCN2 activity controls the onset of the aversive response. Importantly, pharmacological experiments demonstrate that the sole phosphorylation of eIF2α in the MBH is sufficient to regulate food intake. eIF2α signaling being at the crossroad of stress pathways activated in several pathological states, our study indicates that hypothalamic eIF2α phosphorylation could play a critical role in the onset of anorexia associated with certain diseases.
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21
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Effect of GABAB receptor antagonist (CGP35348) on learning and memory in albino mice. ScientificWorldJournal 2014; 2014:983651. [PMID: 24574938 PMCID: PMC3916030 DOI: 10.1155/2014/983651] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2013] [Accepted: 10/27/2013] [Indexed: 01/01/2023] Open
Abstract
The present study was designed to demonstrate the potential effect of CGP 35348 (GABAB receptor antagonist) on the learning, memory formation, and neuromuscular coordination in albino mouse. Mice were intrapertoneally injected with 1 mg CGP 35348/mL of distilled water/Kg body weight, while the control animals were injected with equal volume of saline solution. A battery of neurological tests was applied following the intrapertoneal injections. Results of rota rod indicated that CGP 35348 had no effect on neuromuscular coordination in both male (P = 0.528) and female (P = 0.125) albino mice. CGP 35348 treated females demonstrated poor exploratory behavior during open filed for several parameters (time mobile (P = 0.04), time immobile (P = 0.04), rotations (P = 0.04), and anticlockwise rotations (P = 0.038)). The results for Morris water maze (MWM) retention phase indicated that CGP 35348 treated male mice took shorter latency to reach the hidden platform (P = 0.04) than control indicating improved memory. This observation was complemented by the swim strategies used by mice during training days in MWM as CGP 35348 treated males used more direct and focal approach to reach the platform as the training proceeded.
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22
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Zhang P, Sun Q, Zhao C, Ling S, Li Q, Chang YZ, Li Y. HDAC4 protects cells from ER stress induced apoptosis through interaction with ATF4. Cell Signal 2013; 26:556-63. [PMID: 24308964 DOI: 10.1016/j.cellsig.2013.11.026] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 11/26/2013] [Indexed: 10/26/2022]
Abstract
Histone deacetylase 4 (HDAC4) is involved in the regulation of many fundamental cell processes such as proliferation, differentiation, and survival via the modification of their substrates or protein-protein interactions. In this study, we found that HDAC4 could be upregulated under ER stress. There exists a direct interaction between HDAC4 and activating transcription factor 4 (ATF4). In vitro, overexpression of HDAC4 caused the retention of ATF4 in cytoplasm and inhibition of ATF4 transcriptional activity. ER stress could promote cell apoptosis through the upregulation of ATF4 levels and its target genes such as CHOP and TRB3. This effect was exacerbated by downregulation of HDAC4 levels. These results demonstrated that HDAC4 played an important role in the regulation of ER stress-induced apoptosis through interacting with ATF4 and inhibiting its transcriptional activity.
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Affiliation(s)
- Pengfei Zhang
- Key Lab of Physiology, Biochemistry & Molecular Biology of Hebei Province, Hebei Normal University, Shijiazhuang 050024, China; State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing 100094, China
| | - Qiao Sun
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing 100094, China
| | - Chenyang Zhao
- Key Lab of Physiology, Biochemistry & Molecular Biology of Hebei Province, Hebei Normal University, Shijiazhuang 050024, China
| | - Shukuan Ling
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing 100094, China
| | - Qi Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing 100094, China
| | - Yan-Zhong Chang
- Key Lab of Physiology, Biochemistry & Molecular Biology of Hebei Province, Hebei Normal University, Shijiazhuang 050024, China.
| | - Yingxian Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing 100094, China.
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23
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Molecular Mechanisms of G Protein-Independent Signaling Mediated by 7-Transmembrane Receptors. NEUROPHYSIOLOGY+ 2012. [DOI: 10.1007/s11062-012-9295-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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24
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Takahata Y, Hinoi E, Takarada T, Nakamura Y, Ogawa S, Yoneda Y. Positive regulation by γ-aminobutyric acid B receptor subunit-1 of chondrogenesis through acceleration of nuclear translocation of activating transcription factor-4. J Biol Chem 2012; 287:33293-303. [PMID: 22879594 DOI: 10.1074/jbc.m112.344051] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
A view that signaling machineries for the neurotransmitter γ-aminobutyric acid (GABA) are functionally expressed by cells outside the central nervous system is now prevailing. In this study, we attempted to demonstrate functional expression of GABAergic signaling molecules by chondrocytes. In cultured murine costal chondrocytes, mRNA was constitutively expressed for metabotropic GABA(B) receptor subunit-1 (GABA(B)R1), but not for GABA(B)R2. Immunohistochemical analysis revealed the predominant expression of GABA(B)R1 by prehypertrophic to hypertrophic chondrocytes in tibial sections of newborn mice. The GABA(B)R agonist baclofen failed to significantly affect chondrocytic differentiation determined by Alcian blue staining and alkaline phosphatase activity in cultured chondrocytes, whereas newborn mice knocked out of GABA(B)R1 (KO) showed a decreased body size and delayed calcification in hyoid bone and forelimb and hindlimb digits. Delayed calcification was also seen in cultured metatarsals from KO mice with a marked reduction of Indian hedgehog gene (Ihh) expression. Introduction of GABA(B)R1 led to synergistic promotion of the transcriptional activity of activating transcription factor-4 (ATF4) essential for normal chondrogenesis, in addition to facilitating ATF4-dependent Ihh promoter activation. Although immunoreactive ATF4 was negligibly detected in the nucleus of chondrocytes from KO mice, ATF4 expression was again seen in the nucleus and cytoplasm after the retroviral introduction of GABA(B)R1 into cultured chondrocytes from KO mice. In nuclear extracts of KO chondrocytes, a marked decrease was seen in ATF4 DNA binding. These results suggest that GABA(B)R1 positively regulates chondrogenesis through a mechanism relevant to the acceleration of nuclear translocation of ATF4 for Ihh expression in chondrocytes.
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Affiliation(s)
- Yoshifumi Takahata
- Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
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25
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Sun Y, Duan Y, Eisenstein AS, Hu W, Quintana A, Lam WK, Wang Y, Wu Z, Ravid K, Huang P. A novel mechanism of control of NFκB activation and inflammation involving A2B adenosine receptors. J Cell Sci 2012; 125:4507-17. [PMID: 22767505 DOI: 10.1242/jcs.105023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The nuclear factor kappa B (NFκB) pathway controls a variety of processes, including inflammation, and thus, the regulation of NFκB has been a continued focus of study. Here, we report a newly identified regulation of this pathway, involving direct binding of the transcription factor NFκB1 (the p105 subunit of NFκB) to the C-terminus of the A(2B) adenosine receptor (A(2B)AR), independent of ligand activation. Intriguingly, binding of A(2B)AR to specific sites on p105 prevents polyubiquitylation and degradation of p105 protein. Ectopic expression of the A(2B)AR increases p105 levels and inhibits NFκB activation, whereas p105 protein levels are reduced in cells from A(2B)AR-knockout mice. In accordance with the known regulation of expression of anti- and pro-inflammatory cytokines by p105, A(2B)AR-null mice generate less interleukin (IL)-10, and more IL-12 and tumor necrosis factor (TNF-α). Taken together, our results show that the A(2B)AR inhibits NFκB activation by physically interacting with p105, thereby blocking its polyubiquitylation and degradation. Our findings unveil a surprising function for the A(2B)AR, and provide a novel mechanistic insight into the control of the NFκB pathway and inflammation.
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Affiliation(s)
- Ying Sun
- Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, People's Republic of China
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26
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Bradshaw NJ, Porteous DJ. DISC1-binding proteins in neural development, signalling and schizophrenia. Neuropharmacology 2012; 62:1230-41. [PMID: 21195721 PMCID: PMC3275753 DOI: 10.1016/j.neuropharm.2010.12.027] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 12/17/2010] [Accepted: 12/22/2010] [Indexed: 12/18/2022]
Abstract
In the decade since Disrupted in Schizophrenia 1 (DISC1) was first identified it has become one of the most convincing risk genes for major mental illness. As a multi-functional scaffold protein, DISC1 has multiple identified protein interaction partners that highlight pathologically relevant molecular pathways with potential for pharmaceutical intervention. Amongst these are proteins involved in neuronal migration (e.g. APP, Dixdc1, LIS1, NDE1, NDEL1), neural progenitor proliferation (GSK3β), neurosignalling (Girdin, GSK3β, PDE4) and synaptic function (Kal7, TNIK). Furthermore, emerging evidence of genetic association (NDEL1, PCM1, PDE4B) and copy number variation (NDE1) implicate several DISC1-binding partners as risk factors for schizophrenia in their own right. Thus, a picture begins to emerge of DISC1 as a key hub for multiple critical developmental pathways within the brain, disruption of which can lead to a variety of psychiatric illness phenotypes.
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Key Words
- disc1
- schizophrenia
- neurodevelopment
- signalling
- synapse
- association studies
- app, amyloid precursor protein
- atf4, activating transcription factor 4
- bace1, β-site app-cleaving enzyme-1
- bbs4, bardet–biedl syndrome 4
- cep290, centrosomal protein 290 kda
- cnv, copy number variation
- cre, camp response element
- dbz, disc1-binding zinc finger
- disc1, disrupted in schizophrenia 1
- dixdc1, dishevelled-axin domain containing-1
- fez1, fasciculation and elongation protein zeta 1
- glur, glutamate receptor
- gsk3β, glycogen synthase kinase 3β
- kal7, kalirin-7
- lef/tcf, lymphoid enhancer factor/t cell factor
- lis1, lissencephaly 1
- mtor, mammalian target of rapamycin
- nde1, nuclear distribution factor e homologue 1 or nuclear distribution element 1
- ndel1, nde-like 1
- nrg, neuregulin
- pacap, pituitary adenylate cyclase-activating polypeptide
- pcm1, pericentriolar material 1
- pcnt, pericentrin
- pde4, phosphodiesterase 4
- pi3 k, phosphatidylinositiol 3-kinase
- psd, post-synaptic density
- rac1, ras-related c3 botulinum toxin substrate 1
- tnik, traf2 and nck interacting kinase
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Affiliation(s)
- Nicholas J. Bradshaw
- Medical Genetics Section, Molecular Medicine Centre, Institute of Genetics & Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road South, Edinburgh, Midlothian EH4 2XU, UK
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27
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Jiang X, Su L, Zhang Q, He C, Zhang Z, Yi P, Liu J. GABAB receptor complex as a potential target for tumor therapy. J Histochem Cytochem 2012; 60:269-79. [PMID: 22266766 DOI: 10.1369/0022155412438105] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the vertebrate central nervous system. Metabotropic GABA(B) receptors are heterodimeric G-protein-coupled receptors (GPCRs) consisting of GABA(B1) and GABA(B2) subunits. The intracellular C-terminal domains of GABA(B) receptors are involved in heterodimerization, oligomerization, and association with other proteins, which results in a large receptor complex. Multiple splice variants of the GABA(B1) subunit have been identified in which GABA(B1a) and GABA(B1b) are the most abundant isoforms in the nervous system. Isoforms GABA(B1c) through GABA(B1n) are minor isoforms and are detectable only at mRNA levels. Some of the minor isoforms have been detected in peripheral tissues and encode putative soluble proteins with C-terminal truncations. Interestingly, increased expression of GABA(B) receptors has been detected in several human cancer cells and tissues. Moreover, GABA(B) receptor agonist baclofen inhibited tumor growth in rat models. GABA(B) receptor activation not only induces suppressing the proliferation and migration of various human tumor cells but also results in inactivation of CREB (cAMP-responsive element binding protein) and ERK in tumor cells. Their structural complexity makes it possible to disrupt the functions of GABA(B) receptors in various ways, raising GABA(B) receptor diversity as a potential therapeutic target in some human cancers.
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Affiliation(s)
- Xinnong Jiang
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics of Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, P. R. China.
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Tadevosyan A, Vaniotis G, Allen BG, Hébert TE, Nattel S. G protein-coupled receptor signalling in the cardiac nuclear membrane: evidence and possible roles in physiological and pathophysiological function. J Physiol 2011; 590:1313-30. [PMID: 22183719 DOI: 10.1113/jphysiol.2011.222794] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
G protein-coupled receptors (GPCRs) play key physiological roles in numerous tissues, including the heart, and their dysfunction influences a wide range of cardiovascular diseases. Recently, the notion of nuclear localization and action of GPCRs has become more widely accepted. Nuclear-localized receptors may regulate distinct signalling pathways, suggesting that the biological responses mediated by GPCRs are not solely initiated at the cell surface but may result from the integration of extracellular and intracellular signalling pathways. Many of the observed nuclear effects are not prevented by classical inhibitors that exclusively target cell surface receptors, presumably because of their structures, lipophilic properties, or affinity for nuclear receptors. In this topical review, we discuss specifically how angiotensin-II, endothelin, β-adrenergic and opioid receptors located on the nuclear envelope activate signalling pathways, which convert intracrine stimuli into acute responses such as generation of second messengers and direct genomic effects, and thereby participate in the development of cardiovascular disorders.
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Affiliation(s)
- Artavazd Tadevosyan
- Department of Medicine, Université de Montréal, Montréal, Québec, Canada H3C 3J7
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Takahata Y, Takarada T, Hinoi E, Nakamura Y, Fujita H, Yoneda Y. Osteoblastic γ-aminobutyric acid, type B receptors negatively regulate osteoblastogenesis toward disturbance of osteoclastogenesis mediated by receptor activator of nuclear factor κB ligand in mouse bone. J Biol Chem 2011; 286:32906-17. [PMID: 21828041 PMCID: PMC3190880 DOI: 10.1074/jbc.m111.253526] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 07/11/2011] [Indexed: 11/06/2022] Open
Abstract
The prevailing view is that signaling machineries for the neurotransmitter GABA are also expressed by cells outside the CNS. In cultured murine calvarial osteoblasts, mRNA was constitutively expressed for both subunits 1 and 2 of metabotropic GABA(B) receptor (GABA(B)R), along with inhibition by the GABA(B)R agonist baclofen of cAMP formation, alkaline phosphatase (ALP) activity, and Ca(2+) accumulation. Moreover, baclofen significantly inhibited the transactivation of receptor activator of nuclear factor-κB ligand (RANKL) gene in a manner sensitive to a GABA(B)R antagonist, in addition to decreasing mRNA expression of bone morphogenetic protein-2 (BMP2), osteocalcin, and osterix. In osteoblastic MC3T3-E1 cells stably transfected with GABA(B)R1 subunit, significant reductions were seen in ALP activity and Ca(2+) accumulation, as well as mRNA expression of osteocalcin, osteopontin, and osterix. In cultured calvarial osteoblasts from GABA(B)R1-null mice exhibiting low bone mineral density in tibia and femur, by contrast, both ALP activity and Ca(2+) accumulation were significantly increased together with promoted expression of both mRNA and proteins for BMP2 and osterix. No significant change was seen in the number of multinucleated cells stained for tartrate-resistant acid phosphatase during the culture of osteoclasts prepared from GABA(B)R1-null mice, whereas a significant increase was seen in the number of tartrate-resistant acid phosphatase-positive multinucleated cells in co-culture of osteoclasts with osteoblasts isolated from GABA(B)R1-null mice. These results suggest that GABA(B)R is predominantly expressed by osteoblasts to negatively regulate osteoblastogenesis through down-regulation of BMP2 expression toward disturbance of osteoclastogenesis after down-regulation of RANKL expression in mouse bone.
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Affiliation(s)
- Yoshifumi Takahata
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
| | - Takeshi Takarada
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
| | - Eiichi Hinoi
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
| | - Yukari Nakamura
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
| | - Hiroyuki Fujita
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
| | - Yukio Yoneda
- From the Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa 920-1192, Japan
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Altered GABA signaling in early life epilepsies. Neural Plast 2011; 2011:527605. [PMID: 21826277 PMCID: PMC3150203 DOI: 10.1155/2011/527605] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Revised: 05/04/2011] [Accepted: 05/27/2011] [Indexed: 01/13/2023] Open
Abstract
The incidence of seizures is particularly high in the early ages of life. The immaturity of inhibitory systems, such as GABA, during normal brain development and its further dysregulation under pathological conditions that predispose to seizures have been speculated to play a major role in facilitating seizures. Seizures can further impair or disrupt GABAA signaling by reshuffling the subunit composition of its receptors or causing aberrant reappearance of depolarizing or hyperpolarizing GABAA receptor currents. Such effects may not result in epileptogenesis as frequently as they do in adults. Given the central role of GABAA signaling in brain function and development, perturbation of its physiological role may interfere with neuronal morphology, differentiation, and connectivity, manifesting as cognitive or neurodevelopmental deficits. The current GABAergic antiepileptic drugs, while often effective for adults, are not always capable of stopping seizures and preventing their sequelae in neonates. Recent studies have explored the therapeutic potential of chloride cotransporter inhibitors, such as bumetanide, as adjunctive therapies of neonatal seizures. However, more needs to be known so as to develop therapies capable of stopping seizures while preserving the age- and sex-appropriate development of the brain.
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Contribution of metabotropic GABA(B) receptors to neuronal network construction. Pharmacol Ther 2011; 132:170-9. [PMID: 21718720 DOI: 10.1016/j.pharmthera.2011.06.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 06/08/2011] [Indexed: 01/05/2023]
Abstract
In the 1980s, Bowery and colleagues discovered the presence of a novel, bicuculline-resistant and baclofen-sensitive type of GABA receptor on peripheral nerve terminals, the GABA(B) receptor. Since this pioneering work, GABA(B) receptors have been identified in the Central Nervous System (CNS), where they provide an important inhibitory control of postsynaptic excitability and presynaptic transmitter release. GABA(B) receptors have been implicated in a number of important processes in the adult brain such as the regulation of synaptic plasticity and modulation of rhythmic activity. As a result of these studies, several potential therapeutic applications of GABA(B) receptor ligands have been identified. Recent advances have further shown that GABA(B) receptors play more than a classical inhibitory role in adult neurotransmission, and can in fact function as an important developmental signal early in life. Here we summarize current knowledge on the contribution of GABA(B) receptors to the construction and function of developing neuronal networks.
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Nakamura Y, Hinoi E, Takarada T, Takahata Y, Yamamoto T, Fujita H, Takada S, Hashizume S, Yoneda Y. Positive regulation by GABA(B)R1 subunit of leptin expression through gene transactivation in adipocytes. PLoS One 2011; 6:e20167. [PMID: 21655283 PMCID: PMC3105007 DOI: 10.1371/journal.pone.0020167] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 04/14/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The view that γ-aminobutyric acid (GABA) plays a functional role in non-neuronal tissues, in addition to an inhibitory neurotransmitter role in the mammalian central nervous system, is prevailing, while little attention has been paid to GABAergic signaling machineries expressed by adipocytes to date. In this study, we attempted to demonstrate the possible functional expression of GABAergic signaling machineries by adipocytes. METHODOLOGY/PRINCIPAL FINDINGS GABA(B) receptor 1 (GABA(B)R1) subunit was constitutively expressed by mouse embryonic fibroblasts differentiated into adipocytes and adipocytic 3T3-L1 cells in culture, as well as mouse white adipose tissue, with no responsiveness to GABA(B)R ligands. However, no prominent expression was seen with mRNA for GABA(B)R2 subunit required for heteromeric orchestration of the functional GABA(B)R by any adipocytic cells and tissues. Leptin mRNA expression was significantly and selectively decreased in adipose tissue and embryonic fibroblasts, along with drastically reduced plasma leptin levels, in GABA(B)R1-null mice than in wild-type mice. Knockdown by siRNA of GABA(B)R1 subunit led to significant decreases in leptin promoter activity and leptin mRNA levels in 3T3-L1 cells. CONCLUSIONS/SIGNIFICANCE Our results indicate that GABA(B)R1 subunit is constitutively expressed by adipocytes to primarily regulate leptin expression at the transcriptional level through a mechanism not relevant to the function as a partner of heterodimeric assembly to the functional GABA(B)R.
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Affiliation(s)
- Yukari Nakamura
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Eiichi Hinoi
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Takeshi Takarada
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Yoshifumi Takahata
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Tomomi Yamamoto
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Hiroyuki Fujita
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Saya Takada
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Syota Hashizume
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
| | - Yukio Yoneda
- Laboratory of Molecular Pharmacology, Division of Pharmaceutical Sciences, Kanazawa University Graduate School of Natural Science and Technology, Kanazawa, Ishikawa, Japan
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Renault H, El Amrani A, Palanivelu R, Updegraff EP, Yu A, Renou JP, Preuss D, Bouchereau A, Deleu C. GABA accumulation causes cell elongation defects and a decrease in expression of genes encoding secreted and cell wall-related proteins in Arabidopsis thaliana. PLANT & CELL PHYSIOLOGY 2011; 52:894-908. [PMID: 21471118 PMCID: PMC3093128 DOI: 10.1093/pcp/pcr041] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Accepted: 03/27/2011] [Indexed: 05/18/2023]
Abstract
GABA (γ-aminobutyric acid), a non-protein amino acid, is a signaling factor in many organisms. In plants, GABA is known to accumulate under a variety of stresses. However, the consequence of GABA accumulation, especially in vegetative tissues, remains poorly understood. Moreover, gene expression changes as a consequence of GABA accumulation in plants are largely unknown. The pop2 mutant, which is defective in GABA catabolism and accumulates GABA, is a good model to examine the effects of GABA accumulation on plant development. Here, we show that the pop2 mutants have pollen tube elongation defects in the transmitting tract of pistils. Additionally, we observed growth inhibition of primary root and dark-grown hypocotyl, at least in part due to cell elongation defects, upon exposure to exogenous GABA. Microarray analysis of pop2-1 seedlings grown in GABA-supplemented medium revealed that 60% of genes whose expression decreased encode secreted proteins. Besides, functional classification of genes with decreased expression in the pop2-1 mutant showed that cell wall-related genes were significantly enriched in the microarray data set, consistent with the cell elongation defects observed in pop2 mutants. Our study identifies cell elongation defects caused by GABA accumulation in both reproductive and vegetative tissues. Additionally, our results show that genes that encode secreted and cell wall-related proteins may mediate some of the effects of GABA accumulation. The potential function of GABA as a growth control factor under stressful conditions is discussed.
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Affiliation(s)
- Hugues Renault
- Amélioration des Plantes et Biotechnologies Végétales, UMR 118 INRA, Agrocampus Ouest, Université de Rennes 1, F-35653 Le Rheu cedex, France.
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Frank CL, Ge X, Xie Z, Zhou Y, Tsai LH. Control of activating transcription factor 4 (ATF4) persistence by multisite phosphorylation impacts cell cycle progression and neurogenesis. J Biol Chem 2010; 285:33324-33337. [PMID: 20724472 PMCID: PMC2963346 DOI: 10.1074/jbc.m110.140699] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Organogenesis is a highly integrated process with a fundamental requirement for precise cell cycle control. Mechanistically, the cell cycle is composed of transitions and thresholds that are controlled by coordinated post-translational modifications. In this study, we describe a novel mechanism controlling the persistence of the transcription factor ATF4 by multisite phosphorylation. Proline-directed phosphorylation acted additively to regulate multiple aspects of ATF4 degradation. Stabilized ATF4 mutants exhibit decreased β-TrCP degron phosphorylation, β-TrCP interaction, and ubiquitination, as well as elicit early G1 arrest. Expression of stabilized ATF4 also had significant consequences in the developing neocortex. Mutant ATF4 expressing cells exhibited positioning and differentiation defects that were attributed to early G1 arrest, suggesting that neurogenesis is sensitive to ATF4 dosage. We propose that precise regulation of the ATF4 dosage impacts cell cycle control and impinges on neurogenesis.
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Affiliation(s)
- Christopher L Frank
- From the Massachusetts Institute of Technology, Picower Institute for Learning and Memory, the Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, the Stanley Center for Psychiatric Research
| | - Xuecai Ge
- From the Massachusetts Institute of Technology, Picower Institute for Learning and Memory, the Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, the Stanley Center for Psychiatric Research
| | - Zhigang Xie
- From the Massachusetts Institute of Technology, Picower Institute for Learning and Memory, the Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, the Stanley Center for Psychiatric Research; Departments of Neurosurgery and Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Ying Zhou
- From the Massachusetts Institute of Technology, Picower Institute for Learning and Memory, the Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, the Stanley Center for Psychiatric Research
| | - Li-Huei Tsai
- From the Massachusetts Institute of Technology, Picower Institute for Learning and Memory, the Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, the Stanley Center for Psychiatric Research; Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.
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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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Cryan JF, Slattery DA. GABAB Receptors and Depression: Current Status. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:427-51. [DOI: 10.1016/s1054-3589(10)58016-5] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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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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Sunyer B, Shim KS, An G, Höger H, Lubec G. Hippocampal levels of phosphorylated protein kinase A (phosphor-S96) are linked to spatial memory enhancement by SGS742. Hippocampus 2009; 19:90-8. [PMID: 18727045 DOI: 10.1002/hipo.20484] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cognitive enhancement by the GABA (B) receptor antagonist SGS742 has been well-documented, but mechanisms of action are not fully elucidated. Previous work has proposed involvement of somatostatin-14 and protein kinase C in cognitive enhancement; phospho-protein kinase A (p-PKA), fyn, and phospho-fyn are known signaling systems for spatial memory. It was the aim of the study to determine hippocampal levels of these proteins following SGS742-treatment and to correlate them with the outcome from the Morris water maze (MWM), represented by the parameter "time spent in the target quadrant" during the probe trial. OF1 mice were used for the experiments and divided into four groups: intraperitoneal SGS742 and saline solution treatment, both, tested in the MWM, and two yoked controls. Six hours following the probe trial, hippocampal protein levels were determined by immunoblotting. In the MWM, time spent in the target quadrant was significantly enhanced by SGS742 treatment. p-PKA levels were significantly increased only in the SGS742-treated group tested in the MWM as compared to saline treatment. In yoked controls, no significant differences in p-PKA levels between SGS742 and saline treatment were observed. Somatostatin-14 levels were significantly increased in both SGS742-treated groups. No statistically significant changes of other protein levels were observed. We propose that GABA (B) antagonism represented by SGS742 treatment led to cognitive enhancement involving p-PKA, because yoked controls treated with SGS742 were comparable to yoked saline-treated controls. The finding that somatostatin-14 was also induced in the SGS742-treated yoked controls points to a drug side effect, and therefore the role of somatostatin-14 for cognitive enhancement remains open.
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Affiliation(s)
- Berta Sunyer
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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Sunyer B, Diao WF, Kang SU, An G, Boddul S, Lubec G. Cognitive Enhancement by SGS742 in OF1 Mice Is Linked to Specific Hippocampal Protein Expression. J Proteome Res 2008; 7:5237-53. [DOI: 10.1021/pr800594b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Berta Sunyer
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Wei-Fei Diao
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Sung Ung Kang
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gunyong An
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Sanjay Boddul
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Department of Pediatrics, Medical University of Vienna, Vienna, Austria
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Importin-mediated retrograde transport of CREB2 from distal processes to the nucleus in neurons. Proc Natl Acad Sci U S A 2008; 105:17175-80. [PMID: 18957537 DOI: 10.1073/pnas.0803906105] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Signals received at distal synapses of neurons must be conveyed to the nucleus to initiate the changes in transcription that underlie long-lasting synaptic plasticity. The presence of importin nuclear transporters and of select transcription factors at synapses raises the possibility that importins directly transport transcription factors from synapse to nucleus to modulate gene expression. Here, we show that cyclic AMP response element binding protein 2 (CREB2)/activating transcription factor 4 (ATF4), a transcriptional repressor that modulates long-term synaptic plasticity and memory, localizes to distal dendrites of rodent hippocampal neurons and neurites of Aplysia sensory neurons (SNs) and binds to specific importin alpha isoforms. Binding of CREB2 to importin alpha is required for its transport from distal dendrites to the soma and for its translocation into the nucleus. CREB2 accumulates in the nucleus during long-term depression (LTD) but not long-term potentiation of rodent hippocampal synapses, and during LTD but not long-term facilitation (LTF) of Aplysia sensory-motor synapses. Time-lapse microscopy of CREB2 tagged with a photoconvertible fluorescent protein further reveals retrograde transport of CREB2 from distal neurites to the nucleus of Aplysia SN during phenylalanine-methionine-arginine-phenylalanine-amide (FMRFamide)-induced LTD. Together, our findings indicate that CREB2 is a novel cargo of importin alpha that translocates from distal synaptic sites to the nucleus after stimuli that induce LTD of neuronal synapses.
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Qu M, Tang F, Wang L, Yan H, Han Y, Yan J, Yue W, Zhang D. Associations of ATF4 gene polymorphisms with schizophrenia in male patients. Am J Med Genet B Neuropsychiatr Genet 2008; 147B:732-6. [PMID: 18163433 DOI: 10.1002/ajmg.b.30675] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Activating transcription factor 4 (ATF4) is considered as a positional candidate gene for schizophrenia due to its location at chromosome 22q13, a region linked to schizophrenia. Furthermore, as protein interaction partner of ATF4, disrupted in schizophrenia 1 (DISC1) and its signal pathway implicated in the pathophysiology of schizophrenia have been widely supported by a number of genetic and neurobiological studies. Our aim was to investigate whether ATF4 is associated with schizophrenia in case-control samples of Han Chinese subjects consisting of 352 schizophrenia patients and 357 healthy controls. We detected 18 single nucleotide polymorphisms (SNPs) in ATF4 locus, two of which were analyzed, including one insertion at the putative core promoter region (rs17001266, -/C) and one nonsynonymous variant in exon 1 (rs4894, C/A, Pro22Gln). Allele distributions of two SNPs showed significant associations with schizophrenia in male subjects (respectively, rs17001266: P = 0.021, OR = 1.58, 95% CI = 1.07-2.33; rs4894: P = 0.004, OR = 1.78, 95% CI = 1.19-2.67), but not in female subjects as well as the entire population. Two haplotypes CC and -A constructed of rs17001266-rs4894 also revealed significant associations with schizophrenia in male group (global P = 0.0097). These findings support that ATF4 gene may be involved in susceptibility to schizophrenia with sex-dependent effect in the Chinese Han population and suggest that further functional assays are needed to verify their relevance to the pathogenesis of schizophrenia.
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Affiliation(s)
- Mei Qu
- Key Laboratory for Mental Health, Ministry of Health, Institute of Mental Health, Peking University, Beijing, China
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42
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Boivin B, Vaniotis G, Allen BG, Hébert TE. G protein-coupled receptors in and on the cell nucleus: a new signaling paradigm? J Recept Signal Transduct Res 2008; 28:15-28. [PMID: 18437627 DOI: 10.1080/10799890801941889] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Signaling from internalizing and endosomal receptors has almost become a classic GPCR paradigm in the last several years. However, it has become clear in recent years that GPCRs also elicit signals when resident at other subcellular sites including the endoplasmic reticulum, Golgi apparatus, and the nucleus. In this review we discuss the nature, function, and trafficking of nuclear GPCR signaling complexes, as well as potential sources of endogenous and exogenous ligands. Finally, we pose a series of questions that will need to be answered in the coming years to confirm and extend this as a new paradigm for GPCR signaling.
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Affiliation(s)
- Benoit Boivin
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, USA
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43
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Vidal RL, Ramírez A, Castro M, Concha II, Couve A. Marlin-1 is expressed in testis and associates to the cytoskeleton and GABAB receptors. J Cell Biochem 2008; 103:886-95. [PMID: 17668444 DOI: 10.1002/jcb.21456] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Marlin-1 is a GABA(B) receptor and Jak tyrosine kinase-binding protein that also associates with RNA and microtubules. In humans and rodents, expression of Marlin-1 is predominantly restricted to the brain, but expression in lymphoid cells has also been reported. Here, we have studied the distribution of Marlin-1 in testis and spermatozoa. Our results indicate that Marlin-1 is highly expressed in testis. The protein is abundant in spermatogonia, spermatocytes, spermatozoa, and Sertoli cells. We also have studied the subcellular distribution in spermatozoa. Marlin-1 is present in the tail and to a lesser degree in the head of the sperm cell. Finally, we have explored two protein interactions. Our findings demonstrate that Marlin-1 associates with a microtubule fraction and with GABA(B) receptors in testis suggesting that the set of protein interactions of Marlin-1 are conserved in different tissues.
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Affiliation(s)
- René L Vidal
- Institute of Biochemistry, Universidad Austral de Chile, Isla Teja, Valdivia, Chile
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Sunyer B, Shim KS, Höger H, Lubec G. The Cognitive Enhancer SGS742 Does not Involve Major Known Signaling Cascades in OF1 Mice. Neurochem Res 2008; 33:1384-92. [DOI: 10.1007/s11064-008-9596-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Accepted: 01/10/2008] [Indexed: 11/25/2022]
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Bonaventura MM, Catalano PN, Chamson-Reig A, Arany E, Hill D, Bettler B, Saravia F, Libertun C, Lux-Lantos VA. GABAB receptors and glucose homeostasis: evaluation in GABAB receptor knockout mice. Am J Physiol Endocrinol Metab 2008; 294:E157-67. [PMID: 17971510 DOI: 10.1152/ajpendo.00615.2006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
GABA has been proposed to inhibit insulin secretion through GABAB receptors (GABABRs) in pancreatic beta-cells. We investigated whether GABABRs participated in the regulation of glucose homeostasis in vivo. The animals used in this study were adult male and female BALB/C mice, mice deficient in the GABAB1 subunit of the GABABR (GABAB(-/-)), and wild types (WT). Blood glucose was measured under fasting/fed conditions and in glucose tolerance tests (GTTs) with a Lifescan Glucose meter, and serum insulin was measured by ELISA. Pancreatic insulin content and islet insulin were released by RIA. Western blots for the GABAB1 subunit in islet membranes and immunohistochemistry for insulin and GABAB1 were performed in both genotypes. BALB/C mice preinjected with Baclofen (GABABR agonist, 7.5 mg/kg ip) presented impaired GTTs and decreased insulin secretion compared with saline-preinjected controls. GABAB(-/-) mice showed fasting and fed glucose levels similar to WT. GABAB(-/-) mice showed improved GTTs at moderate glucose overloads (2 g/kg). Baclofen pretreatment did not modify GTTs in GABAB(-/-) mice, whereas it impaired normal glycemia reinstatement in WT. Baclofen inhibited glucose-stimulated insulin secretion in WT isolated islets but was without effect in GABAB(-/-) islets. In GABAB(-/-) males, pancreatic insulin content was increased, basal and glucose-stimulated insulin secretion were augmented, and impaired insulin tolerance test and increased homeostatic model assessment of insulin resistance index were determined. Immunohistochemistry for insulin demonstrated an increase of very large islets in GABAB(-/-) males. Results demonstrate that GABABRs are involved in the regulation of glucose homeostasis in vivo and that the constitutive absence of GABABRs induces alterations in pancreatic histology, physiology, and insulin resistance.
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Affiliation(s)
- M M Bonaventura
- Instituto de Biología y Medicina Experimental-Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
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Abstract
The DISC locus is located at the breakpoint of a balanced t(1;11) chromosomal translocation in a large and unique Scottish family. This translocation segregates in a highly statistically significant manner with a broad diagnosis of psychiatric illness, including schizophrenia, bipolar disorder and major depression, as well as with a narrow diagnosis of schizophrenia alone. Two novel genes were identified at this locus and due to the high prevalence of schizophrenia in this family, they were named Disrupted-in-Schizophrenia-1 (DISC1) and Disrupted-in-Schizophrenia-2 (DISC2). DISC1 encodes a novel multifunctional scaffold protein, whereas DISC2 is a putative noncoding RNA gene antisense to DISC1. A number of independent genetic linkage and association studies in diverse populations support the original linkage findings in the Scottish family and genetic evidence now implicates the DISC locus in susceptibility to schizophrenia, schizoaffective disorder, bipolar disorder and major depression as well as various cognitive traits. Despite this, with the exception of the t(1;11) translocation, robust evidence for a functional variant(s) is still lacking and genetic heterogeneity is likely. Of the two genes identified at this locus, DISC1 has been prioritized as the most probable candidate susceptibility gene for psychiatric illness, as its protein sequence is directly disrupted by the translocation. Much research has been undertaken in recent years to elucidate the biological functions of the DISC1 protein and to further our understanding of how it contributes to the pathogenesis of schizophrenia. These data are the main subject of this review; however, the potential involvement of DISC2 in the pathogenesis of psychiatric illness is also discussed. A detailed picture of DISC1 function is now emerging, which encompasses roles in neurodevelopment, cytoskeletal function and cAMP signalling, and several DISC1 interactors have also been defined as independent genetic susceptibility factors for psychiatric illness. DISC1 is a hub protein in a multidimensional risk pathway for major mental illness, and studies of this pathway are opening up opportunities for a better understanding of causality and possible mechanisms of intervention.
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Affiliation(s)
- J E Chubb
- Medical Genetics Section, The Centre for Molecular Medicine, Western General Hospital, The University of Edinburgh, Edinburgh, UK
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Tu H, Rondard P, Xu C, Bertaso F, Cao F, Zhang X, Pin JP, Liu J. Dominant role of GABAB2 and Gbetagamma for GABAB receptor-mediated-ERK1/2/CREB pathway in cerebellar neurons. Cell Signal 2007; 19:1996-2002. [PMID: 17582742 DOI: 10.1016/j.cellsig.2007.05.004] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2007] [Accepted: 05/20/2007] [Indexed: 11/23/2022]
Abstract
gamma-aminobutyric acid type B (GABA(B)) receptor is an allosteric complex made of two subunits, GABA(B1) and GABA(B2). GABA(B2) plays a major role in the coupling to G protein whereas GABA(B1) binds GABA. It has been shown that GABA(B) receptor activates ERK(1/2) in neurons of the central nervous system, but the molecular mechanisms underlying this event are poorly characterized. Here, we demonstrate that activation of GABA(B) receptor by either GABA or the selective agonist baclofen induces ERK(1/2) phosphorylation in cultured cerebellar granule neurons. We also show that CGP7930, a positive allosteric regulator specific of GABA(B2), alone can induce the phosphorylation of ERK(1/2). PTX, a G(i/o) inhibitor, abolishes both baclofen and CGP7930-mediated-ERK(1/2) phosphorylation. Moreover, both baclofen and CGP7930 induce ERK-dependent CREB phosphorylation. Furthermore, by using LY294002, a PI-3 kinase inhibitor, and a C-term of GRK-2 that has been reported to sequester Gbetagamma subunits, we demonstrate the role of Gbetagamma in GABA(B) receptor-mediated-ERK(1/2) phosphorylation. In conclusion, the activation of GABA(B) receptor leads to ERK(1/2) phosphorylation via the coupling of GABA(B2) to G(i/o) and by releasing Gbetagamma subunits which in turn induce the activation of CREB. These findings suggest a role of GABA(B) receptor in long-term change in the central nervous system.
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Affiliation(s)
- Haijun Tu
- Sino-France Laboratory for Drug Screening, Key Laboratory of Molecular Biophysics, Ministry of Education, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
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Ligon B, Yang J, Morin SB, Ruberti MF, Steer ML. Regulation of pancreatic islet cell survival and replication by gamma-aminobutyric acid. Diabetologia 2007; 50:764-73. [PMID: 17318626 DOI: 10.1007/s00125-007-0601-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Accepted: 12/17/2006] [Indexed: 10/23/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic islets have evolved remarkable, though poorly understood mechanisms to modify beta cell mass when nutrient intake fluctuates or cells are damaged. We hypothesised that appropriate and timely adjustments in cell number occur because beta cells release proliferative signals to surrounding cells when stimulated by nutrients and 'bleed' these growth factors upon injury. MATERIALS AND METHODS In rat pancreatic islets, we measured DNA content, insulin content, insulin secretion after treatment, immunoblots of apoptotic proteins and the uptake of nucleoside analogues to assess the ability of gamma-aminobutyric acid (GABA), which is highly concentrated in beta cells, to act as a growth and survival factor. This focus is supported by work from others demonstrating that GABA increases cell proliferation in the developing nervous system, acts as a survival factor for differentiated neurons and, interestingly, protects plants under stress. RESULTS Our results show that DNA, insulin content and insulin secretion are higher in freshly isolated islets treated with GABA or GABA B receptor agonists. Exposure to GABA upregulated the anti-apoptotic protein B-cell chronic lymphocytic leukaemia XL and limited activation of caspase 3 in islets. The cellular proliferation rate in GABA-treated islets was twice that of untreated controls. CONCLUSIONS/INTERPRETATION We conclude that GABA serves diverse purposes in the islet, meeting a number of functional criteria to act as an endogenous co-regulator of beta cell mass.
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Affiliation(s)
- B Ligon
- Department of Neuroscience, Tufts University School of Medicine, 136 Harrison Ave., Boston, MA 02111, USA.
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Kantamneni S, Corrêa SAL, Hodgkinson GK, Meyer G, Vinh NN, Henley JM, Nishimune A. GISP: a novel brain-specific protein that promotes surface expression and function of GABA(B) receptors. J Neurochem 2007; 100:1003-17. [PMID: 17241134 PMCID: PMC3315443 DOI: 10.1111/j.1471-4159.2006.04271.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synaptic transmission depends on the regulated surface expression of neurotransmitter receptors, but many of the cellular processes required to achieve this remain poorly understood. To better define specific mechanisms for the GABA(B) receptor (GABA(B)R) trafficking, we screened for proteins that bind to the carboxy-terminus of the GABA(B1) subunit. We report the identification and characterization of a novel 130-kDa protein, GPCR interacting scaffolding protein (GISP), that interacts directly with the GABA(B1) subunit via a coiled-coil domain. GISP co-fractionates with GABA(B)R and with the postsynaptic density and co-immunoprecipitates with GABA(B1) and GABA(B2) from rat brain. In cultured hippocampal neurons, GISP displays a punctate dendritic distribution and has an overlapping localization with GABA(B)Rs. When co-expressed with GABA(B)Rs in human embryonic kidney cells, GISP promotes GABA(B)R surface expression and enhances both baclofen-evoked extracellular signal-regulated kinase (ERK) phosphorylation and G-protein inwardly rectifying potassium channel (GIRK) currents. These results suggest that GISP is involved in the forward trafficking and stabilization of functional GABA(B)Rs.
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Balasubramanian S, Fam SR, Hall RA. GABAB receptor association with the PDZ scaffold Mupp1 alters receptor stability and function. J Biol Chem 2006; 282:4162-71. [PMID: 17145756 DOI: 10.1074/jbc.m607695200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
gamma-Aminobutyric acid, type B (GABA(B)) receptors are heterodimeric G protein-coupled receptors that mediate slow inhibitory synaptic transmission in the central nervous system. To identify novel interacting partners that might regulate GABA(B) receptor (GABA(B)R) functionality, we screened the GABA(B)R2 carboxyl terminus against a recently created proteomic array of 96 distinct PDZ (PSD-95/Dlg/ZO-1 homology) domains. The screen identified three specific PDZ domains that exhibit interactions with GABA(B)R2: Mupp1 PDZ13, PAPIN PDZ1, and Erbin PDZ. Biochemical analysis confirmed that full-length Mupp1 and PAPIN interact with GABA(B)R2 in cells. Disruption of the GABA(B)R2 interaction with PDZ scaffolds by a point mutation to the carboxyl terminus of the receptor dramatically decreased receptor stability and attenuated the duration of GABA(B) receptor signaling. The effects of mutating the GABA(B)R2 carboxyl terminus on receptor stability and signaling were mimicked by small interference RNA knockdown of endogenous Mupp1. These findings reveal that GABA(B) receptor stability and signaling can be modulated via GABA(B)R2 interactions with the PDZ scaffold protein Mupp1, which may contribute to cell-specific regulation of GABA(B) receptors in the central nervous system.
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