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Yuan D, Zhou Z, Song M, Zhang Y, Zhang Y, Ren P, Chen Z, Fu Y. Role of GABA B receptors in cognition and EEG activity in aged APP and PS1 transgenic mice. Neurochem Int 2024; 175:105718. [PMID: 38490487 DOI: 10.1016/j.neuint.2024.105718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 02/27/2024] [Accepted: 03/04/2024] [Indexed: 03/17/2024]
Abstract
Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Recent evidence suggests that gamma-aminobutyric acid B (GABAB) receptor-mediated inhibition is a major contributor to AD pathobiology, and GABAB receptors have been hypothesized to be a potential target for AD treatment. The aim of this study is to determine how GABAB regulation alters cognitive function and brain activity in an AD mouse model. Early, middle and late stage (8-23 months) amyloid precursor protein (APP) and presenilin 1 (PS1) transgenic mice were used for the study. The GABAB agonist baclofen (1 and 2.5 mg/kg, i. p.) and the antagonist phaclofen (0.5 mg/kg, i. p.) were used. Primarily, we found that GABAB activation was able to improve spatial and/or working memory performance in early and late stage AD animals. In addition, GABAB activation and inhibition could regulate global and local EEG oscillations in AD animals, with activation mainly regulating low-frequency activity (delta-theta bands) and inhibition mainly regulating mid- and high-frequency activity (alpha-gamma bands), although the regulated magnitude at some frequencies was reduced in AD. The cognitive improvements in AD animals may be explained by the reduced EEG activity in the theta frequency band (2-4 Hz). This study provides evidence for a potential therapeutic effect of baclofen in the elderly AD brain and for GABAB receptor-mediated inhibition as a potential therapeutic target for AD.
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Affiliation(s)
- Dong Yuan
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Zheng Zhou
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Meihui Song
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Yunfan Zhang
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Yunbin Zhang
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Ping Ren
- Department of Geriatric Psychiatry, Shenzhen Mental Health Center, Shenzhen Kangning Hospital, Shenzhen, Guangdong, 518020, China
| | - Zhuangfei Chen
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China
| | - Yu Fu
- Medical School, Kunming University of Science & Technology, Kunming, Yunnan, 650500, China.
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Petrella M, Borruto AM, Curti L, Domi A, Domi E, Xu L, Barbier E, Ilari A, Heilig M, Weiss F, Mannaioni G, Masi A, Ciccocioppo R. Pharmacological blockage of NOP receptors decreases ventral tegmental area dopamine neuronal activity through GABA B receptor-mediated mechanism. Neuropharmacology 2024; 248:109866. [PMID: 38364970 DOI: 10.1016/j.neuropharm.2024.109866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 01/15/2024] [Accepted: 02/05/2024] [Indexed: 02/18/2024]
Abstract
The Nociceptin/Orphanin FQ (N/OFQ) peptide and its receptor NOP are highly expressed within several regions of the mesolimbic system, including the ventral tegmental area (VTA). Evidence indicates that the N/OFQ-NOP receptor system is involved in reward processing and historically it has been proposed that activation of NOP receptors attenuates the motivation for substances of abuse. However, recent findings demonstrated that drug self-administration and relapse to drug-seeking are also attenuated after administration of NOP receptor antagonists. Here, to shed light on the mechanisms through which NOP receptor blockers modulate these processes, we utilized ex vivo patch-clamp recordings to investigate the effect of the selective NOP receptor antagonist LY2817412 on VTA dopaminergic (DA) function in male rats. Results showed that, similar to the endogenous NOP receptor agonist N/OFQ, LY2817412 reduced the spontaneous basal firing discharge of VTA DA neurons. Consistently, we found that NOP receptors are expressed both in VTA DA and GABA cells and that LY2817412 slice perfusion increased GABA release onto VTA DA cells. Finally, in the attempt to dissect the role of postsynaptic and presynaptic NOP receptors, we tested the effect of N/OFQ and LY2817412 in the presence of GABA receptors blockers. Results showed that the effect of LY2817412 was abolished following pretreatment with GABABR, but not GABAAR, blockers. Conversely, inhibition of DA neuronal activity by N/OFQ was unaffected by blockade of GABA receptors. Altogether, these results suggest that both NOP receptor agonists and antagonists can decrease VTA DA neuronal activity, but through distinct mechanisms of action. The effect of NOP receptor antagonists occurs through a GABABR-mediated mechanism while NOP receptor agonists seem to act via a direct effect on VTA DA neurons.
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Affiliation(s)
- Michele Petrella
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Anna Maria Borruto
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Lorenzo Curti
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, Florence, Italy
| | - Ana Domi
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Esi Domi
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy; Center for Social and Affective Neuroscience, Institute for Clinical and Experimental Medicine, Linkoping University, Linkoping, 58183, Sweden
| | - Li Xu
- Center for Social and Affective Neuroscience, Institute for Clinical and Experimental Medicine, Linkoping University, Linkoping, 58183, Sweden
| | - Estelle Barbier
- Center for Social and Affective Neuroscience, Institute for Clinical and Experimental Medicine, Linkoping University, Linkoping, 58183, Sweden
| | - Alice Ilari
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy
| | - Markus Heilig
- Center for Social and Affective Neuroscience, Institute for Clinical and Experimental Medicine, Linkoping University, Linkoping, 58183, Sweden
| | - Friedbert Weiss
- Department of Molecular and Cellular Neuroscience, The Scripps Research Institute, La Jolla, CA, USA
| | - Guido Mannaioni
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, Florence, Italy
| | - Alessio Masi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of Florence, Florence, Italy
| | - Roberto Ciccocioppo
- School of Pharmacy, Center for Neuroscience, Pharmacology Unit, University of Camerino, Camerino, Italy.
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Colombo G. Positive allosteric modulators of the GABAB receptor: a new class of ligands with therapeutic potential for alcohol use disorder. Alcohol Alcohol 2024; 59:agae018. [PMID: 38566580 DOI: 10.1093/alcalc/agae018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/22/2024] [Accepted: 03/08/2024] [Indexed: 04/04/2024] Open
Abstract
BACKGROUND Positive allosteric modulators (PAMs) of the GABAB receptor constitute a new class of GABAB-receptor ligands. GABAB PAMs reproduce several pharmacological effects of the orthosteric GABAB receptor agonist, baclofen, although displaying a better safety profile. AIMS This paper reviews the reducing or, frequently, even suppressing effects of all GABAB PAMs tested to date on multiple alcohol-related behaviours in laboratory rodents exposed to validated experimental models of human alcohol use disorder. RESULTS Acute or repeated treatment with CGP7930, GS39783, BHF177, rac-BHFF, ADX71441, CMPPE, COR659, ASP8062, KK-92A, and ORM-27669 reduced excessive alcohol drinking, relapse- and binge-like drinking, operant alcohol self-administration, reinstatement of alcohol seeking, and alcohol-induced conditioned place preference in rats and mice. CONCLUSIONS These effects closely mirrored those of baclofen; notably, they were associated to remarkably lower levels of tolerance and toxicity. The recent transition of ASP8062 to clinical testing will soon prove whether these highly consistent preclinical data translate to AUD patients.
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Affiliation(s)
- Giancarlo Colombo
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, I-09042, Monserrato (CA), Italy
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Qiao S, Zhang WY, Xie YF, Li HY, Cui CS, Tao SX, Xin T, Liu QJ. Diagnostic signatures and immune cell infiltration characteristics in anti-GABA BR encephalitis. J Neuroimmunol 2024; 388:578296. [PMID: 38309225 DOI: 10.1016/j.jneuroim.2024.578296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 08/16/2023] [Accepted: 01/23/2024] [Indexed: 02/05/2024]
Abstract
PURPOSE Anti-gamma-aminobutyric acid B receptor (GABABR) encephalitis is an uncommon form of autoimmune encephalitis associated with a poor prognosis and a high fatality rate. We aim to find diagnostic markers for anti- GABABR encephalitis as well as the effects of immune cell infiltration on this pathology. METHODS For quantitative proteomic analysis, isobaric tags for relative and absolute quantitation were used in conjunction with LC-MS/MS analysis. To conduct functional correlation analyses, differentially expressed proteins (DEPs) were identified. Following that, we used bioinformatics analysis to screen for and determine the diagnostic signatures of anti- GABABR encephalitis. ROC curves were used to evaluate the diagnostic values. To assess the inflammatory status of anti- GABABR encephalitis, we used cell-type identification by estimating relative subsets of the RNA transcript (CIBERSORT) and explored the link between diagnostic markers and infiltrating immune cells. RESULTS Overall, 108 robust DEPs (47 upregulated and 61 downregulated) were identified, of which 11 were immune related. The most impressively enriched pathways were complemented and coagulation cascades, actin cytoskeleton regulation, and cholesterol metabolism; GSEA revealed that the enriched pathways were considerably differentially connected to immune modulation. Eleven immune-related DEPs were chosen for further investigation. We developed a novel diagnostic model based on CSF1R and AZGP1 serum levels using ROC analysis (area under the ROC curve = 1). M1 macrophages and activated natural killer cells are likely to play a role in course of anti- GABABR encephalitis. CONCLUSION We identified CSF1R and AZGP1 are possible anti-GABABR encephalitis diagnostic indicators, and immune cell infiltration may have a significant impact on the development and occurrence of anti- GABABR encephalitis.
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Affiliation(s)
- Shan Qiao
- Department of Neurology, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China; Key Laboratory for Experimental Teratology, Ministry of Education and Department of Medical Genetics, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan 250012, China
| | - Wen-Yu Zhang
- Department of Clinical Research, Central Hospital Affiliated to Shandong First Medical University, Jinan 250013, China
| | - Yun-Fang Xie
- Key Laboratory for Experimental Teratology, Ministry of Education and Department of Medical Genetics, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan 250012, China
| | - Hai-Yun Li
- Department of Geriatric Medicine, Qilu Hospital of Shandong University, Jinan, China
| | - Cai-San Cui
- Department of Neurology, Qilu Hospital of Shandong University, Jinan, China
| | - Shu-Xin Tao
- Department of Neurology, Liaocheng People's Hospital, Liaocheng, Shandong, China
| | - Tao Xin
- Department of Neurosurgery, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China; Medical Science and Technology Innovation Center, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China.
| | - Qi-Ji Liu
- Key Laboratory for Experimental Teratology, Ministry of Education and Department of Medical Genetics, School of Basic Medical Sciences, Cheeloo College of Medicine, Shandong University, Jinan 250012, China.
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Guzikowski NJ, Kavalali ET. Synaptic vesicle pool heterogeneity drives an anomalous form of synaptic plasticity. Proc Natl Acad Sci U S A 2024; 121:e2401734121. [PMID: 38422062 PMCID: PMC10945817 DOI: 10.1073/pnas.2401734121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Affiliation(s)
- Natalie J. Guzikowski
- Department of Pharmacology, Vanderbilt University, Nashville, TN37240-7933
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN37240-7933
| | - Ege T. Kavalali
- Department of Pharmacology, Vanderbilt University, Nashville, TN37240-7933
- Vanderbilt Brain Institute, Vanderbilt University, Nashville, TN37240-7933
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Javadova A, Felmy F. GABA B receptor-mediated modulation in the developing dorsal nucleus of the lateral lemniscus. Eur J Neurosci 2024; 59:966-981. [PMID: 38180306 DOI: 10.1111/ejn.16246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 11/30/2023] [Accepted: 12/18/2023] [Indexed: 01/06/2024]
Abstract
The dorsal nucleus of the lateral lemniscus (DNLL) is a GABAergic, reciprocally connected auditory brainstem structure that continues to develop postnatally in rodents. One key feature of the DNLL is the generation of a strong, prolonged, ionotropic, GABAA receptor-mediated inhibition. Possible GABAB receptor-mediated signalling is unexplored in the DNLL. Here, we used Mongolian gerbils of either sex to describe GABAB receptor-mediated modulation of postsynaptic potassium currents and synaptic inputs in postnatal (P) animals of days 10/11 and 23-28. Throughout development, we observed the presence of a Baclofen-activated GABAB receptor-enhanced potassium outward conductance that is capable of suppressing action potential generation. In P10/11, old gerbils GABAB receptor activation enhances glutamatergic and suppresses ionotropic GABAergic synaptic transmission. During development, this differential modulation becomes less distinct, because in P22-28, old animals Baclofen-activated GABAB receptors rather enhance ionotropic GABAergic synaptic transmission, whereas glutamatergic transmission is both enhanced and suppressed. Blocking GABAB receptors causes an increase in ionotropic GABAergic transmission in P10/11 old gerbils that was independent on stimulation frequency but depended on the type of short-term plasticity. Together with the lack of Baclofen-induced changes in the synaptic paired-pulse ratio of either input type, we suggest that GABAB receptor-mediated modulation is predominantly postsynaptic and activates different signalling cascades. Thus, we argue that in DNLL neurons, the GABAB receptor is a post-synaptically located signalling hub that alters signalling cascades during development for distinct targets.
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Affiliation(s)
- Amina Javadova
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Hannover, Germany
- Infection Medicine and Veterinary Sciences (HGNI), Hannover Graduate School for Neurosciences, Hannover, Germany
| | - Felix Felmy
- Institute for Zoology, University of Veterinary Medicine Foundation, Hannover, Hannover, Germany
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Ngodup T, Irie T, Elkins SP, Trussell LO. The Na + leak channel NALCN controls spontaneous activity and mediates synaptic modulation by α2-adrenergic receptors in auditory neurons. eLife 2024; 12:RP89520. [PMID: 38197879 PMCID: PMC10945507 DOI: 10.7554/elife.89520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024] Open
Abstract
Cartwheel interneurons of the dorsal cochlear nucleus (DCN) potently suppress multisensory signals that converge with primary auditory afferent input, and thus regulate auditory processing. Noradrenergic fibers from locus coeruleus project to the DCN, and α2-adrenergic receptors inhibit spontaneous spike activity but simultaneously enhance synaptic strength in cartwheel cells, a dual effect leading to enhanced signal-to-noise for inhibition. However, the ionic mechanism of this striking modulation is unknown. We generated a glycinergic neuron-specific knockout of the Na+ leak channel NALCN in mice and found that its presence was required for spontaneous firing in cartwheel cells. Activation of α2-adrenergic receptors inhibited both NALCN and spike generation, and this modulation was absent in the NALCN knockout. Moreover, α2-dependent enhancement of synaptic strength was also absent in the knockout. GABAB receptors mediated inhibition through NALCN as well, acting on the same population of channels as α2 receptors, suggesting close apposition of both receptor subtypes with NALCN. Thus, multiple neuromodulatory systems determine the impact of synaptic inhibition by suppressing the excitatory leak channel, NALCN.
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Affiliation(s)
- Tenzin Ngodup
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
| | - Tomohiko Irie
- Department of Physiology, Kitasato University School of MedicineSagamiharaJapan
| | - Seán P Elkins
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
| | - Laurence O Trussell
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science UniversityPortlandUnited States
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Li X, Zhu Y, Sun H, Shen Z, Sun J, Xiao S, He X, Liu B, Wang Y, Hu Y, Liu B, Liang Y, Jiang Y, Du J, Xu C, Fang J, Shao X. Electroacupuncture Inhibits Pain Memory and Related Anxiety-Like Behaviors by Blockading the GABA B Receptor Function in the Midcingulate Cortex. Mol Neurobiol 2023; 60:6613-6626. [PMID: 37468738 PMCID: PMC10533721 DOI: 10.1007/s12035-023-03467-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Accepted: 06/24/2023] [Indexed: 07/21/2023]
Abstract
Pain memory is commonly considered an underlying cause of chronic pain and is also responsible for a range of anxiety. Electroacupuncture (EA) has been shown to ameliorate pain memories and exert anti-anxiety effects. Previous research has indicated that GABAergic neurons and/or GABA receptors (GABARs) in the midcingulate cortex (MCC) have potential associations with chronic pain and anxiety. However, there is no known empirical research that has specifically studied the effects of EA on the GABAergic system in the MCC. Here, we used cross-injection of carrageenan to establish the pain memory rats model. Immunofluorescence were used to detect the excitability of GABAergic neurons within MCC. Von Frey filament, elevated zero maze, and open field tests were used to measure mechanical allodynia and anxiety-like behaviors, combined with chemogenetic and pharmacologic technologies. Finally, this study provides evidence that pain memories contribute to generalized negative emotions and that downregulating the activity of GABAergic neurons within MCC could block pain memories and reverse anxiety emotion. Specifically, GABABR is involved in pain memory and related anxiety-like behaviors. Activation of GABAergic neurons in the MCC did not reverse the effects of EA on pain memories and related anxiety-like behaviors, whereas these effects could be reversed by a GABABR agonist. These findings highlight the functional significance of GABABR in the EA-mediated attenuation of pain memories and related anxiety-like behaviors in rats.
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Affiliation(s)
- Xiaoyu Li
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Yichen Zhu
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Haiju Sun
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Zui Shen
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Jing Sun
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Siqi Xiao
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Xiaofen He
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Boyu Liu
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Yifang Wang
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Yuxin Hu
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Boyi Liu
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Yi Liang
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Yongliang Jiang
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Junying Du
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Chi Xu
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China
| | - Jianqiao Fang
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China.
| | - Xiaomei Shao
- The Third Clinical Medical College, Key Laboratory of Acupuncture and Neurology of Zhejiang Province, Zhejiang Chinese Medical University, No.548 Binwen Road, Binjiang District, Hangzhou, 310053, Zhejiang, China.
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Nakamizo-Dojo M, Ishii K, Yoshino J, Tsuji M, Emoto K. Descending GABAergic pathway links brain sugar-sensing to peripheral nociceptive gating in Drosophila. Nat Commun 2023; 14:6515. [PMID: 37845214 PMCID: PMC10579361 DOI: 10.1038/s41467-023-42202-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 10/03/2023] [Indexed: 10/18/2023] Open
Abstract
Although painful stimuli elicit defensive responses including escape behavior for survival, starved animals often prioritize feeding over escape even in a noxious environment. This behavioral priority is typically mediated by suppression of noxious inputs through descending control in the brain, yet underlying molecular and cellular mechanisms are incompletely understood. Here we identify a cluster of GABAergic neurons in Drosophila larval brain, designated as SEZ-localized Descending GABAergic neurons (SDGs), that project descending axons onto the axon terminals of the peripheral nociceptive neurons and prevent presynaptic activity through GABAB receptors. Remarkably, glucose feeding to starved larvae causes sustained activation of SDGs through glucose-sensing neurons and subsequent insulin signaling in SDGs, which attenuates nociception and thereby suppresses escape behavior in response to multiple noxious stimuli. These findings illustrate a neural mechanism by which sugar sensing neurons in the brain engages descending GABAergic neurons in nociceptive gating to achieve hierarchical interaction between feeding and escape behavior.
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Affiliation(s)
- Mami Nakamizo-Dojo
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kenichi Ishii
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Jiro Yoshino
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Masato Tsuji
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Kazuo Emoto
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
- International Research Center for Neurointelligence (WPI-IRCN), 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
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Tureček R, Melichar A, Králíková M, Hrušková B. The role of GABA B receptors in the subcortical pathways of the mammalian auditory system. Front Endocrinol (Lausanne) 2023; 14:1195038. [PMID: 37635966 PMCID: PMC10456889 DOI: 10.3389/fendo.2023.1195038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
GABAB receptors are G-protein coupled receptors for the inhibitory neurotransmitter GABA. Functional GABAB receptors are formed as heteromers of GABAB1 and GABAB2 subunits, which further associate with various regulatory and signaling proteins to provide receptor complexes with distinct pharmacological and physiological properties. GABAB receptors are widely distributed in nervous tissue, where they are involved in a number of processes and in turn are subject to a number of regulatory mechanisms. In this review, we summarize current knowledge of the cellular distribution and function of the receptors in the inner ear and auditory pathway of the mammalian brainstem and midbrain. The findings suggest that in these regions, GABAB receptors are involved in processes essential for proper auditory function, such as cochlear amplifier modulation, regulation of spontaneous activity, binaural and temporal information processing, and predictive coding. Since impaired GABAergic inhibition has been found to be associated with various forms of hearing loss, GABAB dysfunction could also play a role in some pathologies of the auditory system.
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Affiliation(s)
- Rostislav Tureček
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Adolf Melichar
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
- Second Faculty of Medicine, Charles University, Prague, Czechia
| | - Michaela Králíková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
| | - Bohdana Hrušková
- Department of Auditory Neuroscience, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czechia
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Li Q, Zhang X, Zeng T, Yang B, Duan J, Tang Y. Clinical characteristics and prognosis of anti-GABABR encephalitis: A single-center experience. Medicine (Baltimore) 2023; 102:e32956. [PMID: 36800611 PMCID: PMC9936044 DOI: 10.1097/md.0000000000032956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
Abstract
The purpose of this study was to assess the demographic data, clinical manifestations, cerebrospinal fluid (CSF), hematology, brain magnetic resonance imaging, electroencephalograms, and therapy and prognosis related to anti-gamma-aminobutyric acid B (anti-GABABR) encephalitis. We retrospectively examined the demographic data, clinical manifestations, laboratory results, brain magnetic resonance imaging, electroencephalograms, and therapy and prognosis of 6 patients with anti-GABABR encephalitis. We used the clinical data of patients with anti-GABABR encephalitis admitted to the Department of Neurology of Mianyang Central Hospital obtained from January 2017 to September 2020. Six patients with anti-GABABR encephalitis were included. Generalized tonic-clonic seizure was the first clinical symptom in 5 patients, while 1 patient first showed behavior disorder. After the first clinical symptom attack, 2 patients developed a memory deficit, 4 cases showed cognitive decline, 3 cases showed behavior disorder, 1 patient developed status epilepticus and only 1 patient returned to normal. CSF testing indicated normal intracranial pressure in 5 patients and elevated pressure in only 1 patient. Additionally, the cerebrospinal fluid tests revealed slight leukocytosis in all patients and elevated protein levels in 5 patients. The anti-GABABR antibody was positive in both serum and CSF in all patients. Brain magnetic resonance imaging showed limbic system lesions in 4 patients. Long-term electroencephalograms revealed abnormal waves in half of the patients. All patients were treated with high dosages of methylprednisolone, which was combined with intravenous immunoglobulin in 2 patients; symptoms were improved in 4 patients, 1 patient showed no significant change and 1 patient with status epilepticus died of severe pneumonia during hospitalization. Epilepsy is the most common initial symptom in patients of anti-GABABR encephalitis. Many patients are also affected by tumors. Early immunotherapy can achieve excellent effects, the long-term prognosis is good for most patients.
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Affiliation(s)
- Qiang Li
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
| | - Xianwen Zhang
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
| | - Ting Zeng
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
| | - Bufan Yang
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
| | - Jingfeng Duan
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
| | - Yufeng Tang
- Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China
- * Correspondence: Yufeng Tang, Department of Neurology, Mianyang Central Hospital, School of Medicine, University of Electronic Science and Technology of China, Mianyang, China (e-mail: )
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12
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Affiliation(s)
- J Y Shen
- From the Department of Neurology, National Neuroscience Institute, Singapore, Singapore
| | - G J Ng
- From the Department of Neurology, National Neuroscience Institute, Singapore, Singapore
| | - T Yeo
- From the Department of Neurology, National Neuroscience Institute, Singapore, Singapore
- Duke-NUS Medical School, Singapore, Singapore
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13
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Onishi Y, Yamamura Y, Hosogi M, Higashi H, Ogita K, Kinjo T, Uno K, Yoneda Y, Kuramoto N. Delayed Expression of Both GABA BR1 and GABA BR2 Subunits in Murine Hippocampal Dentate Gyrus After a Single Systemic Injection of Trimethyltin. Neurochem Res 2022; 47:2780-2792. [PMID: 35737203 DOI: 10.1007/s11064-022-03652-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/26/2022] [Accepted: 06/06/2022] [Indexed: 11/24/2022]
Abstract
Trimethyltin (TMT) has been used as a cytotoxin to neurons rather than glial cells in the mammalian hippocampus. The systemic administration of TMT led to declined fluorescence of ZnAF-2 DA staining as a marker of intact mossy fibers and increased fluorescence of Fluoro-Jade B staining as a marker of degenerated neurons during the initial 2 to 5 days after the administration with later ameliorations within 30 days in the hippocampal dentate gyrus (DG) and CA3 region in mice. On immunoblotting analysis, both GABABR1 and GABABR2 subunit levels increased during 15 to 30 days after TMT along with significant decreases in glutamatergic GluA1 and GluA2/3 receptor subunit levels during 2 to 7 days in the DG, but not in other hippocampal regions such as CA1 and CA3 regions. Immunohistochemical analysis revealed the constitutive and inducible expression of GABABR2 subunit in cells immunoreactive to an astrocytic marker as well as neuronal markers in the DG with the absence of neither GABABR1a nor GABABR1b subunit from cells positive to an astrocytic marker. These results suggest that both GABABR1 and GABABR2 subunits may be up-regulated in cells other than neurons and astroglia in the DG at a late stage of TMT intoxication in mice.
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Affiliation(s)
- Yuki Onishi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
- Laboratory of Pharmacology, Faculty of Pharmaceutical Sciences, Hiroshima International University, Hiroshima, 737-0112, Japan
| | - Yusuke Yamamura
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
| | - Misa Hosogi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Hiroshi Higashi
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Kiyokazu Ogita
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
- Setsunan University, 17-8 Ikedanakamachi, Neyagawa, Osaka, 572-8508, Japan
| | - Toshihiko Kinjo
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Kyosuke Uno
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Yukio Yoneda
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan
| | - Nobuyuki Kuramoto
- Laboratories of Molecular Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan.
- Laboratories of Pharmacology, Faculty of Pharmaceutical Sciences, Setsunan University, Hirakata, Osaka, 573-0101, Japan.
- The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo, 140-0001, Japan.
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D'Onofrio G, Riva A, Di Rosa G, Cali' E, Efthymiou S, Gitto E, Madia F, Accogli A, Zara F, Houlden H, Salpietro V, Striano P, Soler D. Paroxysmal limb dystonias associated with GABBR2 pathogenic variant: A case-based literature review. Brain Dev 2022; 44:469-473. [PMID: 35414446 DOI: 10.1016/j.braindev.2022.03.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 03/28/2022] [Accepted: 03/29/2022] [Indexed: 11/18/2022]
Abstract
BACKGROUND De novo mutations in the GABBR2 (Gamma-Aminobutyric acid Type B Receptor Subunit 2) gene have recently been reported to be associated with a form of early-infantile epileptic encephalopathy (EIEE59; OMIM# 617904), as well as a Rett syndrome (RTT)-like disorder defined as a neurodevelopmental disorder with poor language and loss of hand skills (NDPLHS; OMIM# 617903). METHODS We describe a pediatric case carrying a de novo GABBR2 pathogenic variant and showing a phenotype encompassing RTT, epilepsy, generalized hypotonia with a paroxysmal limb dystonia. RESULTS A 11-year-old girl, born to non-consanguineous parents after an uneventful pregnancy, had developmental delay and generalized hypotonia. At age 3.5 months she presented with infantile spasms with an electroencephalographic pattern of hypsarrhythmia. After treatment with clonazepam and prednisolone, she became seizure-free with a slow background electrical activity. Brain magnetic resonance imaging was normal. Paroxysmal dystonic posturing of the extremities, especially the upper limbs, have been observed since the age of 3 years. Motor stereotypies, non-epileptic episodes of hyperventilation and breath-holding were also reported. The girl suffered from feeding difficulties requiring gastrostomy at the age of 8. Exome sequencing (ES) revealed a de novo GABBR2 pathogenic variant (NM_005458:c.G2077T:p.G693W). CONCLUSION Paroxysmal limb dystonias, especially in the context of neurodevelopmental disorder featuring epilepsy, generalized hypotonia and RTT-like features should lead to the suspect of GABBR2 mutations.
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Affiliation(s)
- Gianluca D'Onofrio
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy
| | - Antonella Riva
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy
| | - Gabriella Di Rosa
- Child Neuropsychiatry Unit, Department of Pediatrics, University of Messina, Messina 98100, Italy
| | - Elisa Cali'
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Gower Street, London WC1E 6BT, United Kingdom
| | - Stephanie Efthymiou
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Gower Street, London WC1E 6BT, United Kingdom
| | - Eloisa Gitto
- Intensive Neonatal and Pediatric Care Unit, Department of Pediatrics, University of Messina, Messina 98100, Italy
| | - Francesca Madia
- Unit of Medical Genetics, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy
| | - Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, Montreal Children's Hospital, McGill University Health Centre (MUHC), Montreal, Canada; Department of Human Genetics, McGill University, Montreal, QC, Canada
| | - Federico Zara
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Unit of Medical Genetics, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Gower Street, London WC1E 6BT, United Kingdom
| | - Vincenzo Salpietro
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, Gower Street, London WC1E 6BT, United Kingdom
| | - Pasquale Striano
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Via Gerolamo Gaslini 5, 16147 Genoa, Italy; Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto "Giannina Gaslini", Via Gerolamo Gaslini 5, 16147 Genoa, Italy
| | - Doriette Soler
- Department of Paediatrics, Mater dei Hospital, Msida, Malta.
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15
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Abstract
GABAB receptors (GBRs), the G protein-coupled receptors for the inhibitory neurotransmitter γ-aminobutyric acid (GABA), activate Go/i-type G proteins that regulate adenylyl cyclase, Ca2+ channels, and K+ channels. GBR signaling to enzymes and ion channels influences neuronal activity, plasticity processes, and network activity throughout the brain. GBRs are obligatory heterodimers composed of GB1a or GB1b subunits with a GB2 subunit. Heterodimeric GB1a/2 and GB1b/2 receptors represent functional units that associate in a modular fashion with regulatory, trafficking, and effector proteins to generate receptors with distinct physiological functions. This review summarizes current knowledge on the structure, organization, and functions of multi-protein GBR complexes.
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Affiliation(s)
- Thorsten Fritzius
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Michal Stawarski
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland
| | - Shin Isogai
- Biozentrum, Focal Area Structural Biology and Biophysics, University of Basel, Basel, Switzerland.
- Microbial Downstream Process Development, Lonza AG, Visp, Switzerland.
| | - Bernhard Bettler
- Department of Biomedicine, Institute of Physiology, Pharmazentrum, University of Basel, Basel, Switzerland.
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16
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Abstract
GABA is the main inhibitory neurotransmitter in the mammalian central nervous system (CNS) and acts via metabotropic GABAB receptors. Neurodegenerative diseases are a major burden and affect an ever increasing number of humans. The actual therapeutic drugs available are partially effective to slow down the progression of the diseases, but there is a clear need to improve pharmacological treatment thus find alternative drug targets and develop newer pharmaco-treatments. This chapter is dedicated to reviewing the latest evidence about GABAB receptors and their inhibitory mechanisms and pathways involved in the neurodegenerative pathologies.
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Affiliation(s)
- Alessandra P Princivalle
- Department of Bioscience and Chemistry, Biomolecular Research Centre, College of Health, Wellbeing and Life Sciences at Sheffield Hallam University, Sheffield, UK.
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17
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Abstract
Preclinical research over the past several decades has demonstrated a role for the γ-aminobutyric acidB (GABAB) receptor in alcohol use disorder (AUD). This chapter offers an examination of preclinical evidence on the role of the GABAB receptor on alcohol-related behaviors with a particular focus on the GABAB receptor agonist baclofen, for which effects have been most extensively studied, and positive allosteric modulators (PAMs) of the GABAB receptor. Studies employing rodent and non-human primate models have shown that activation of the GABAB receptor can reduce (1) stimulating and rewarding effects of alcohol; (2) signs of alcohol withdrawal in rats made physically dependent on alcohol; (3) acquisition and maintenance of alcohol drinking under a two-bottle alcohol versus water choice procedure; (4) alcohol intake under oral operant self-administration procedures; (5) motivational properties of alcohol measured using extinction and progressive ratio procedures; (6) the increase in alcohol intake after a period of alcohol abstinence (the alcohol deprivation effect or ADE); and (7) the ability of alcohol cues and stress to reinstate alcohol seeking when alcohol is no longer available. Baclofen and GABAB PAMs reduce the abovementioned behaviors across different preclinical models, which provides strong evidence for a significant role of the GABAB receptor in alcohol-related behaviors and supports development of medications targeting GABAB receptors for the treatment of AUD. This chapter highlights the value of examining mechanisms of alcohol-related behaviors across multiple animal models to increase the confidence in identification of new therapeutic targets.
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Affiliation(s)
- August F Holtyn
- Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Elise M Weerts
- Johns Hopkins University School of Medicine, Baltimore, MD, USA
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18
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Abstract
Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the brain, acts at the ionotropic GABAA and GABAC receptors, and the metabotropic GABAB receptor. This chapter summarizes the studies that have investigated the role of the GABAB receptor in stress-related psychiatric disorders including anxiety and mood disorders. Overall, clinical and preclinical evidences strongly suggest that the GABAB receptor is a therapeutic candidate for depression and anxiety disorders. However, the clinical development of GABAB receptor-based drugs to treat these disorders has been hampered by their potential side-effects, particularly those of agonists. Nevertheless, the discovery of novel GABAB receptor allosteric modulators, and increasing understanding of the influence of specific intracellular GABAB receptor-associated proteins on GABAB receptor activity, may now pave the way towards GABAB receptor therapeutics in the treatment of mood and anxiety disorders.
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Affiliation(s)
- Daniela Felice
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
- APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - John F Cryan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
| | - Olivia F O'Leary
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
- APC Microbiome Ireland, University College Cork, Cork, Ireland.
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19
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Abstract
A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABAB receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABAB receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
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20
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Deng SL, Hu ZL, Mao L, Gao B, Yang Q, Wang F, Chen JG. The effects of Kctd12, an auxiliary subunit of GABA B receptor in dentate gyrus on behavioral response to chronic social defeat stress in mice. Pharmacol Res 2021; 163:105355. [PMID: 33285230 DOI: 10.1016/j.phrs.2020.105355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2019] [Revised: 11/17/2020] [Accepted: 12/01/2020] [Indexed: 12/28/2022]
Abstract
Adaptive responses to stress are critical to enhance physical and mental well-being, but excessive or prolonged stress may cause inadaptability and increase the risks of psychiatric disorders, such as depression. GABABR signaling is fundamental to brain function and has been identified in neuropsychiatric disorders. KCTD12 is a critical auxiliary subunit in GABABR signaling, but its role in mental disorders, such as depression is unclear. In the present study, we used a well-validated mice model, chronic social defeat stress (CSDS) to investigate behavioral responses to stress and explore the role of Kctd12 in stress response, as well as the relevant mechanisms. We found that CSDS increased the expression of Kctd12 in the dentate gyrus (DG), a subregion of hippocampus. Overexpression of Kctd12 in DG induced higher responsiveness to acute stress and increased vulnerability to social stress in mice, whereas knock-down of Kctd12 in DG prevented the social avoidance. Furthermore, an increased expression of GABAB receptor 2 (GB2) in the DG of CSDS-treated mice was observed, and CGP35348, an antagonist of GABABR, improved the stress-induced behavior responses along with suppressing the excess expression of Kctd12. In addition, Kctd12 regulated the excitability of granule cell in DG, and the stimulation of neuronal activity by silencing Kctd12 contributed to the antidepressant-like effect of fluoxetine. These findings identify that the Kctd12 in DG works as a critical mediator of stress responses, providing a promising therapeutic target in stress-related psychiatric disorders, including depression.
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Affiliation(s)
- Si-Long Deng
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Zhuang-Li Hu
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; Hubei Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation (HUST), Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China
| | - Li Mao
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Bo Gao
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Qiong Yang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Fang Wang
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; Hubei Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation (HUST), Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative-Innovation Center for Brain Science, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China.
| | - Jian-Guo Chen
- Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China; Hubei Key Laboratory of Drug Target Research and Pharmacodynamic Evaluation (HUST), Wuhan, 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, Wuhan, 430030, China; The Collaborative-Innovation Center for Brain Science, Wuhan, 430030, China; The Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, 430030, China.
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21
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Lobina C, Maccioni P, Lorrai I, Zaru A, Collu M, Carai MAM, Brizzi A, Mugnaini C, Gessa GL, Corelli F, Colombo G. Suppressing effect of the novel positive allosteric modulator of the GABA B receptor, COR659, on locomotor hyperactivity induced by different drugs of abuse. Behav Brain Res 2020; 400:113045. [PMID: 33309750 DOI: 10.1016/j.bbr.2020.113045] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 11/10/2020] [Accepted: 11/23/2020] [Indexed: 01/08/2023]
Abstract
COR659 is a recently synthesized positive allosteric modulator (PAM) of the GABAB receptor. Similarly to all GABAB PAMs tested to date, COR659 has been reported to suppress different alcohol-related behaviors in rodents. The present study was designed to assess whether the anti-addictive properties of COR659 extend to drugs of abuse other than alcohol. Specifically, it investigated the effect of COR659 on cocaine-, amphetamine-, nicotine-, and morphine-induced locomotor hyperactivity in mice. To this aim, independent groups of CD1 mice were acutely pretreated with COR659 (0, 10, and 20 mg/kg; i.p.), then acutely treated with cocaine (0 and 10 mg/kg, s.c.), amphetamine (0 and 5 mg/kg; s.c.), nicotine (0 and 0.05 mg/kg; s.c.), or morphine (0 and 20 mg/kg; s.c.), and finally exposed for 60 min to a photocell-equipped motility cage. When given alone, both doses of COR659 were ineffective on spontaneous locomotor activity. Pretreatment with COR659 reduced, or even suppressed, the increase in motility counts induced by cocaine, amphetamine, nicotine, and morphine. Since locomotor hyperactivity is an attribute common to drugs of abuse, the results of the present study constitute the first line of evidence on the extension of the preclinical, anti-addictive profile of COR659 to cocaine, amphetamine, nicotine, and morphine.
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Affiliation(s)
- Carla Lobina
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy
| | - Paola Maccioni
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy
| | - Irene Lorrai
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy; Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, I-09042, Italy
| | - Alessandro Zaru
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy; Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, I-09042, Italy
| | - Maria Collu
- Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, I-09042, Italy
| | - Mauro A M Carai
- Cagliari Pharmacological Research, Cagliari, CA, I-09127, Italy
| | - Antonella Brizzi
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, Siena, SI, I-53100, Italy
| | - Claudia Mugnaini
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, Siena, SI, I-53100, Italy
| | - Gian Luigi Gessa
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy; Department of Biomedical Sciences, University of Cagliari, Monserrato, CA, I-09042, Italy
| | - Federico Corelli
- Department of Biotechnology, Chemistry, and Pharmacy, University of Siena, Siena, SI, I-53100, Italy
| | - Giancarlo Colombo
- Neuroscience Institute, Section of Cagliari, National Research Council of Italy, Monserrato, CA, I-09042, Italy.
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22
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Perez‐Zabalza M, Reig R, Manrique J, Jercog D, Winograd M, Parga N, Sanchez‐Vives MV. Modulation of cortical slow oscillatory rhythm by GABA B receptors: an in vitro experimental and computational study. J Physiol 2020; 598:3439-3457. [PMID: 32406934 PMCID: PMC7984206 DOI: 10.1113/jp279476] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 05/11/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We confirm that GABAB receptors (GABAB -Rs) are involved in the termination of Up-states; their blockade consistently elongates Up-states. GABAB -Rs also modulate Down-states and the oscillatory cycle, thus having an impact on slow oscillation rhythm and its regularity. The most frequent effect of GABAB -R blockade is elongation of Down-states and subsequent decrease of oscillatory frequency, with an increased regularity. In a quarter of cases, GABAB -R blockade shortened Down-states and increased oscillatory frequency, changes that are independent of firing rates in Up-states. Our computer model provides mechanisms for the experimentally observed dynamics following blockade of GABAB -Rs, for Up/Down durations, oscillatory frequency and regularity. The time course of excitation, inhibition and adaptation can explain the observed dynamics of the network. This study brings novel insights into the role of GABAB -R-mediated slow inhibition on the slow oscillatory activity, which is considered the default activity pattern of the cortical network. ABSTRACT Slow wave oscillations (SWOs) dominate cortical activity during deep sleep, anaesthesia and in some brain lesions. SWOs are composed of periods of activity (Up states) interspersed with periods of silence (Down states). The rhythmicity expressed during SWOs integrates neuronal and connectivity properties of the network and is often altered under pathological conditions. Adaptation mechanisms as well as synaptic inhibition mediated by GABAB receptors (GABAB -Rs) have been proposed as mechanisms governing the termination of Up states. The interplay between these two mechanisms is not well understood, and the role of GABAB -Rs controlling the whole cycle of the SWO has not been described. Here we contribute to its understanding by combining in vitro experiments on spontaneously active cortical slices and computational techniques. GABAB -R blockade modified the whole SWO cycle, not only elongating Up states, but also affecting the subsequent Down state duration. Furthermore, while adaptation tends to yield a rather regular behaviour, we demonstrate that GABAB -R activation desynchronizes the SWOs. Interestingly, variability changes could be accomplished in two different ways: by either shortening or lengthening the duration of Down states. Even when the most common observation following GABAB -Rs blocking is the lengthening of Down states, both changes are expressed experimentally and also in numerical simulations. Our simulations suggest that the sluggishness of GABAB -Rs to follow the excitatory fluctuations of the cortical network can explain these different network dynamics modulated by GABAB -Rs.
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Affiliation(s)
- Maria Perez‐Zabalza
- Institut d'Investigaciones Biomediques August Pi i Sunyer (IDIBAPS)BarcelonaSpain
| | - Ramon Reig
- Instituto de Neurociencias de Alicante, CSIC‐UMHSan Juan de AlicanteAlicanteSpain
| | | | - Daniel Jercog
- Institut d'Investigaciones Biomediques August Pi i Sunyer (IDIBAPS)BarcelonaSpain
| | - Milena Winograd
- Instituto de Neurociencias de Alicante, CSIC‐UMHSan Juan de AlicanteAlicanteSpain
| | - Nestor Parga
- Física TeóricaUniversidad Autónoma MadridMadridSpain
- Centro de Investigación Avanzada en Física FundamentalUniversidad Autónoma de MadridMadridSpain
| | - Maria V. Sanchez‐Vives
- Institut d'Investigaciones Biomediques August Pi i Sunyer (IDIBAPS)BarcelonaSpain
- Institució Catalana de Recerca i Estudis Avançats (ICREA)BarcelonaSpain
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Evenseth LSM, Ocello R, Gabrielsen M, Masetti M, Recanatini M, Sylte I, Cavalli A. Exploring Conformational Dynamics of the Extracellular Venus flytrap Domain of the GABA B Receptor: A Path-Metadynamics Study. J Chem Inf Model 2020; 60:2294-2303. [PMID: 32233432 PMCID: PMC7997371 DOI: 10.1021/acs.jcim.0c00163] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Indexed: 12/21/2022]
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the central nervous system (CNS). Dysfunctional GABAergic neurotransmission is associated with numerous neurological and neuropsychiatric disorders. The GABAB receptor (GABAB-R) is a heterodimeric class C G protein-coupled receptor (GPCR) comprised of GABAB1a/b and GABAB2 subunits. The orthosteric binding site for GABA is located in the extracellular Venus flytrap (VFT) domain of the GABAB1a/b. Knowledge about molecular mechanisms and druggable receptor conformations associated with activation is highly important to understand the receptor function and for rational drug design. Currently, the conformational changes of the receptor upon activation are not well described. On the basis of other class C members, the VFT is proposed to fluctuate between an open/inactive and closed/active state and one of these conformations is stabilized upon ligand binding. In the present study, we investigated the dynamics of the GABAB1b-R VFT in the apo form by combining unbiased molecular dynamics with path-metadynamics. Our simulations confirmed the open/inactive and closed/active state as the main conformations adopted by the receptor. Sizeable energy barriers were found between stable minima, suggesting a relatively slow interconversion. Previously undisclosed metastable states were also identified, which might hold potential for future drug discovery efforts.
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Affiliation(s)
- Linn S. M. Evenseth
- Molecular
Pharmacology and Toxicology, Department of Medical Biology, Faculty
of Health Sciences, UiT—The Arctic
University of Norway, NO-9037Tromsø, Norway
| | - Riccardo Ocello
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum—Università di Bologna, Via Belmeloro 6, I-40126 Bologna, Italy
- CompuNet, Istituto Italiano
di Tecnologia, Via Morego
30, I-16163 Genova, Italy
| | - Mari Gabrielsen
- Molecular
Pharmacology and Toxicology, Department of Medical Biology, Faculty
of Health Sciences, UiT—The Arctic
University of Norway, NO-9037Tromsø, Norway
| | - Matteo Masetti
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum—Università di Bologna, Via Belmeloro 6, I-40126 Bologna, Italy
| | - Maurizio Recanatini
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum—Università di Bologna, Via Belmeloro 6, I-40126 Bologna, Italy
| | - Ingebrigt Sylte
- Molecular
Pharmacology and Toxicology, Department of Medical Biology, Faculty
of Health Sciences, UiT—The Arctic
University of Norway, NO-9037Tromsø, Norway
| | - Andrea Cavalli
- Department
of Pharmacy and Biotechnology, Alma Mater
Studiorum—Università di Bologna, Via Belmeloro 6, I-40126 Bologna, Italy
- CompuNet, Istituto Italiano
di Tecnologia, Via Morego
30, I-16163 Genova, Italy
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Wang WB, Zhu JZ, Li XY, Li CH, Su JG, Li JY. Enhancement of protein mechanical stability: Correlated deformations are handcuffed by ligand binding. J Chem Phys 2019; 150:155102. [PMID: 31005084 DOI: 10.1063/1.5054932] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
As revealed by previous experiments, protein mechanical stability can be effectively regulated by ligand binding with the binding site distant from the force-bearing region. However, the mechanism for such long-range allosteric control of protein mechanics is still largely unknown. In this work, we use protein topology-based elastic network model (ENM) and all-atomic steered molecular dynamics (SMD) simulations to study the impact of ligand binding on protein mechanical stability in two systems, i.e., GB1 and CheY-binding P2-domain of CheA (CBDCheA). Both ENM and SMD results show that the ligand binding has considerable and negligible effects on the mechanical stability of these two proteins, respectively. These results are consistent with the experimental observations. A physical mechanism for the enhancement of protein mechanical stability was then proposed: the correlated deformations of the force-bearing region and the binding site are handcuffed by the binding of ligand. The handcuff effect suppresses the propagation of internal force in the force-bearing region, thus improving the resistance to the loading force. Our study indicates that ENM method can effectively identify the structure motifs allosterically related to the deformation in the force bearing region, as well as the force propagation pathway within the structure of the studied proteins. Hence, it should be helpful to understand the molecular origin of the different mechanical properties in response to ligand binding for GB1 and CBDCheA.
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Affiliation(s)
- Wei Bu Wang
- Key Laboratory for Microstructural Material Physics of Hebei Province, College of Science, Yanshan University, Qinhuangdao 066004, China
| | - Jian Zhuo Zhu
- Key Laboratory for Microstructural Material Physics of Hebei Province, College of Science, Yanshan University, Qinhuangdao 066004, China
| | - Xing Yuan Li
- Key Laboratory for Microstructural Material Physics of Hebei Province, College of Science, Yanshan University, Qinhuangdao 066004, China
| | - Chun Hua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Beijing 100124, China
| | - Ji Guo Su
- Key Laboratory for Microstructural Material Physics of Hebei Province, College of Science, Yanshan University, Qinhuangdao 066004, China
| | - Jing Yuan Li
- Institute of Quantitative Biology and Department of Physics, Zhejiang University, Hangzhou 310027, China
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Lupinsky D, Moquin L, Gratton A. Interhemispheric regulation of the rat medial prefrontal cortical glutamate stress response: role of local GABA- and dopamine-sensitive mechanisms. Psychopharmacology (Berl) 2017; 234:353-363. [PMID: 27822602 DOI: 10.1007/s00213-016-4468-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 10/21/2016] [Indexed: 11/26/2022]
Abstract
RATIONALE We previously reported that stressors increase medial prefrontal cortex (PFC) glutamate (GLU) levels as a result of activating callosal neurons located in the opposite hemisphere and that this PFC GLU stress response is regulated by GLU-, dopamine- (DA-), and GABA-sensitive mechanisms (Lupinsky et al. 2010). OBJECTIVES Here, we examine the possibility that PFC DA regulates the stress responsivity of callosal neurons indirectly by acting at D1 and D2 receptors located on GABA interneurons. METHODS Microdialysis combined with drug perfusion (reverse dialysis) or microinjections was used in adult male Long-Evans rats to characterize D1, D2, and GABAB receptor-mediated regulation of the PFC GABA response to tail-pinch (TP) stress. RESULTS We report that TP stress reliably elicited comparable increases in extracellular GABA in the left and right PFCs. SCH23390 (D1 antagonist; 100 μM perfusate concentration) perfused by reverse microdialysis attenuated the local GABA stress responses equally in the left and right PFCs. Intra-PFC raclopride perfusion (D2 antagonist; 100 μM) had the opposite effect, not only potentiating the local GABA stress response but also causing a transient elevation in basal (pre-stress) GABA. Moreover, unilateral PFC raclopride microinjection (6 nmol) attenuated the GLU response to TP stress in the contralateral PFC. Finally, intra-PFC baclofen perfusion (GABAB agonist; 100 μM) inhibited the local GLU and GABA stress responses. CONCLUSIONS Taken together, these findings implicate PFC GABA interneurons in processing stressful stimuli, showing that local D1, D2, and GABAB receptor-mediated changes in PFC GABA transmission play a crucial role in the interhemispheric regulation of GLU stress responsivity.
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Affiliation(s)
- Derek Lupinsky
- Department of Psychiatry, McGill University, Montréal, Québec, H4H 1R3, Canada.
- Douglas Institute Research Center, 6875 LaSalle Blvd, Montréal, Québec, H4H 1R3, Canada.
| | - Luc Moquin
- Douglas Institute Research Center, 6875 LaSalle Blvd, Montréal, Québec, H4H 1R3, Canada
| | - Alain Gratton
- Department of Psychiatry, McGill University, Montréal, Québec, H4H 1R3, Canada
- Douglas Institute Research Center, 6875 LaSalle Blvd, Montréal, Québec, H4H 1R3, Canada
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Zhang M, Hao HJ, Liu LP, Zhang HH, Zhou YY. [An analysis and literature review of two cases of autoimmune encephalitis with GABA B receptor antibodies]. Zhonghua Nei Ke Za Zhi 2016; 55:791-793. [PMID: 27686441 DOI: 10.3760/cma.j.issn.0578-1426.2016.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Autoimmune encephalitis with GABAB receptor antibodies has been rarely reported. Two cases of GABAB receptor antibodies encephalitis were presented here.Epilepsy was the onset symptom, followed by declined consciousness and frequent seizures. Fever was presented in the whole course of the disease. Myorhythmia of the two hands and pilomotor seizures were shown in the later course of the disease. No specificity was demonstrated in electroencephalograms and magnetic resonance imaging. Sensitive response was shown to the first-line immunotherapy.
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Affiliation(s)
- M Zhang
- Department of Neurology, Tianjin Huanhu Hospital, Tianjin 300060, China
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Nashawi H, Masocha W, Edafiogho IO, Kombian SB. Paclitaxel Causes Electrophysiological Changes in the Anterior Cingulate Cortex via Modulation of the γ-Aminobutyric Acid-ergic System. Med Princ Pract 2016; 25:423-8. [PMID: 27336416 PMCID: PMC5588502 DOI: 10.1159/000447775] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 06/22/2016] [Indexed: 01/08/2023] Open
Abstract
OBJECTIVE The aim of this study was to elucidate any electrophysiological changes that may contribute to the development of neuropathic pain during treatment with the anticancer drug paclitaxel, particularly in the γ-aminobutyric acid (GABA) system. MATERIALS AND METHODS One hundred and eight Sprague-Dawley rats were used (untreated control: 43; vehicle-treated: 21, and paclitaxel-treated: 44). Paclitaxel (8 mg/kg) was administered intraperitoneally on 2 alternate days to induce mechanical allodynia. The rats were sacrificed 7 days after treatment to obtain slices of the anterior cingulate cortex (ACC), a brain region involved in the central processing of pain. Field excitatory postsynaptic potentials (fEPSPs) were recorded in layer II/III of ACC slices, and stimulus-response curves were constructed. The observed effects were pharmacologically characterized by bath application of GABA and appropriate drugs to the slices. RESULTS The paclitaxel-treated rats developed mechanical allodynia (i.e. reduced withdrawal threshold to mechanical stimuli). Slices from paclitaxel-treated rats produced a significantly higher maximal response (Emax) than those from untreated rats (p < 0.001). Bath application of GABA (0.4 µM) reversed this effect and returned the excitability to a level similar to control. Pretreatment of the slices with the GABAB receptor blocker CGP 55845 (50 µM) increased Emax in slices from untreated rats (p < 0.01) but not from paclitaxel-treated rats. CONCLUSION In this study, there was a GABA deficit in paclitaxel-treated rats compared to untreated ones. Such a deficit could contribute to the pathophysiology of paclitaxel-induced neuropathic pain (PINP). Thus, the GABAergic system might be a potential therapeutic target for managing PINP.
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Affiliation(s)
- Houda Nashawi
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Health Sciences Centre, Kuwait University, Jabriya, Kuwait, Conn., USA
| | - Willias Masocha
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Health Sciences Centre, Kuwait University, Jabriya, Kuwait, Conn., USA
- *Willias Masocha, Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Health Sciences Centre, Kuwait University, PO Box 24923, Safat, Jabriya 13110 (Kuwait), E-Mail
| | - Ivan O. Edafiogho
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Saint Joseph, Hartford, Conn., USA
| | - Samuel B. Kombian
- Department of Pharmacology and Therapeutics, Faculty of Pharmacy, Health Sciences Centre, Kuwait University, Jabriya, Kuwait, Conn., USA
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Bonaventura MM, Rodriguez D, Ferreira ML, Crivello M, Repetto EM, Bettler B, Libertun C, Lux-Lantos VA. Sex differences in insulin resistance in GABAB1 knockout mice. Life Sci 2013; 92:175-82. [PMID: 23178152 DOI: 10.1016/j.lfs.2012.11.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 10/16/2012] [Accepted: 11/07/2012] [Indexed: 11/17/2022]
Abstract
AIMS We have previously demonstrated that the absence of functional GABA B receptors (GABABRs) disturbs glucose homeostasis in GABAB1KO mice. The aim of this work was to extend our studies of these alterations in GABAB1KO mice and investigate the sexual differences therein. MAIN METHODS Male and female, GABAB1KO and WT mice were used. Glucose and insulin tolerance tests (GTT and ITT), and insulin and glucagon secretion tests (IST and GST) were performed. Blood glucose, serum insulin and hyperglycemic hormones were determined, and HOMA-IR calculated. Skeletal muscle insulin receptor β subunit (IRβ), insulin receptor substrates 1/2 (IRS1, IRS2) and hexokinase-II levels were determined by Western blot. Skeletal muscle insulin sensitivity was assessed by in vivo insulin-induced Akt phosphorylation (Western blot). Food intake and hypothalamic NPY mRNA expression (by qPCR) were also evaluated. KEY FINDINGS Fasted insulin and HOMA-IR were augmented in GABAB1KO males, with no alterations in females. Areas under the curve (AUC) for GTT and ITT were increased in GABAB1KO mice of both genders, indicating compromised insulin sensitivity. No genotype differences were observed in IST, GST or in IRβ, IRS1, IRS2 and hexokinase-II expression. Akt activation was severely impaired in GABAB1KO males while no alterations were observed in females. GABAB1KO mice showed increased food intake and NPY expression. SIGNIFICANCE Glucose metabolism and energy balance disruptions were more pronounced in GABAB1KO males, which develop peripheral insulin resistance probably due to augmented insulin secretion. Metabolic alterations in females were milder and possibly due to previously described reproductive disorders, such as persistent estrus.
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Affiliation(s)
- M M Bonaventura
- Instituto de Biología y Medicina Experimental-CONICET, Buenos Aires, Argentina
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29
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Andriamampandry C, Taleb O, Kemmel V, Humbert JP, Aunis D, Maitre M. Cloning and functional characterization of a gamma-hydroxybutyrate receptor identified in the human brain. FASEB J 2006; 21:885-95. [PMID: 17197387 DOI: 10.1096/fj.06-6509com] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Two parent clones of a gamma-hydroxybutyrate (GHB) receptor, C12K32 and GHBh1, were isolated from a human frontal cortex cDNA library. The two clones differ by a deleted cytosine in C12K32. CHO cells transfected with either C12K32 or GHBh1 responded positively to submicromolar GHB stimulation. However, unlike C12K32, GHBh1 desensitizes rapidly on application of low concentrations of GHB. GHB receptor properties were then studied on C12K32 expressed in CHO cells. C12K32 bound GHB with a Kd of 114 nM and has no affinity for GABA or glutamate. GHB and NCS-382 displaced [3H]GHB with an IC50 of 53 +/- 8 and 120 +/- 18 nM, respectively. In patch-clamp experiments, GHB induced a dose-dependent response with an EC50 of 130 nM. This response was antagonized by NCS-382, was not reproduced by GABA, and was sensitive to the addition of GTP-gamma-S in the recording pipette. CHO cells transfected with C12K32 exhibited GTPgamma-35S binding with an EC50 of 462 nM for GHB and an IC50 of 2.9 microM for NCS-382. The present data led to the conclusion that both C12K32 and GHBh1 are two closely related isoforms of a human GHB receptor, GHBh1, that is described in the databank as the GPCR 172A.
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Abstract
RATIONALE Previous data have demonstrated that the convulsant effects of cocaine can be modulated by compounds that increase levels of endogenous gamma-aminobutyric acid (GABA) or that directly stimulate GABA(A) receptors. OBJECTIVES To determine whether the convulsant effects of cocaine can be modulated by ligands selective for GABA(B) receptors in mice. METHODS Effects of the GABA(B) receptor agonist ((+/-)-baclofen), antagonist (phaclofen), and their combination were tested against clonic seizures induced by cocaine (75 mg/kg). Enantiomers of baclofen were used to confirm stereospecificity of (+/-)-baclofen's effects. Pharmacological specificity of (+/-)-baclofen's effects was tested by comparison against seizures induced by GBR 12909 (monoamine transporter inhibitor), pentylenetetrazole (GABA(A) antagonist), N-methyl-D-aspartate (NMDA agonist), and aminophylline (A1/A2 adenosine antagonist). Additionally, effects of (+/-)-baclofen on kindled seizures induced by repeated administration of cocaine (60 mg/kg every 24 h for 6 days) were evaluated. The inverted screen test was used to assess behavioral side effects of baclofen. RESULTS (+/-)-Baclofen dose-dependently inhibited acute (ED50=4.1 mg/kg) and kindled (6.4 mg/kg) seizures induced by cocaine at doses somewhat lower than those producing behavioral side effects (11.5 mg/kg), and these effects were stereospecific. (+/-)-Baclofen suppressed seizures induced by GBR 12909 but not by pentylenetetrazole, NMDA, and aminophylline, suggesting selectivity of its anticonvulsant effects for monoamine-related mechanisms. Finally, phaclofen dose-dependently enhanced the convulsant effects of a threshold dose of cocaine (60 mg/kg). CONCLUSIONS Modulation of GABA(B) receptors can affect seizures induced by cocaine. This molecular mechanism may be involved in seizures induced by cocaine or, alternatively, may function as an independent inhibitory mechanism against seizures arising from blockade of monoamine uptake.
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Affiliation(s)
- Maciej Gasior
- Drug Development Group, Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, 5500 Nathan Shock Drive, Baltimore, MD 21224, USA.
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Abstract
It is currently accepted that cGMP-dependent protein kinase (PKG) inhibits platelet activation. Here, we show that PKG plays an important stimulatory role in platelet activation. Expression of recombinant PKG in a reconstituted cell model enhanced von Willebrand factor (vWF)-induced activation of the platelet integrin alpha(IIb)beta(3). PKG knockout mice showed impaired platelet responses to vWF or low doses of thrombin and prolonged bleeding time. Human platelet aggregation induced by vWF or low-dose thrombin was inhibited by PKG inhibitors but enhanced by cGMP. Furthermore, a cGMP-enhancing agent, sildenafil, promoted vWF- or thrombin-induced platelet aggregation. The cGMP-stimulated platelet responses are biphasic, consisting of an initial transient stimulatory response that promotes platelet aggregation and a subsequent inhibitory response that limits the size of thrombi.
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Affiliation(s)
- Zhenyu Li
- Department of Pharmacology, College of Medicine, University of Illinois, 835 South Wolcott Avenue, Chicago, IL 60612, USA
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32
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Abstract
The effects of the GABA(B) receptor agonists baclofen (1.4 and 7 micromol/kg i.v.) and CGP 44532 ([(2S)-3-amino-2-hydroxypropyl]methyl phosphinic acid], 0.2 and 0.7 micromol/kg i.v.) on transient lower esophageal sphincter relaxations and spontaneous and pharyngeally stimulated swallowing were investigated in conscious dogs. Both compounds inhibited transient lower esophageal sphincter relaxations dose-dependently, CGP 44532 being approximately fivefold more potent. In experiments designed to measure transient lower esophageal sphincter relaxations, spontaneous swallowing was suppressed by both compounds. When swallowing was evoked by intrapharyngeal water injection, both baclofen and CGP 44532 reduced the occurrence of primary peristalsis. It is concluded that centrally acting GABA(B) receptor agonists inhibit spontaneous and stimulated swallowing probably through an action in the central pattern generator for swallowing.
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Affiliation(s)
- Anders Lehmann
- Integrative Pharmacology, Gastrointestinal Biology, AstraZeneca R&D Mölndal, Mölndal, Sweden.
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Martinez-Torres A, Miledi R. Expression of gamma-aminobutyric acid rho 1 and rho 1 Delta 450 as gene fusions with the green fluorescent protein. Proc Natl Acad Sci U S A 2001; 98:1947-51. [PMID: 11172056 PMCID: PMC29362 DOI: 10.1073/pnas.98.4.1947] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/11/2000] [Indexed: 11/18/2022] Open
Abstract
The functional characteristics and cellular localization of the gamma aminobutyric acid (GABA) rho 1 receptor and its nonfunctional isoform rho 1 Delta 450 were investigated by expressing them as gene fusions with the enhanced version of the green fluorescent protein (GFP). Oocytes injected with rho 1-GFP had receptors that gated chloride channels when activated by GABA. The functional characteristics of these receptors were the same as for those of wild-type rho 1 receptors. Fluorescence, because of the chimeric receptors expressed, was over the whole oocyte but was more intense near the cell surface and more abundant in the animal hemisphere. Similar to the wild type, rho 1 Delta 450-GFP did not lead to the expression of functional GABA receptors, and injected oocytes failed to generate currents even after exposure to high concentrations of GABA. Nonetheless, the fluorescence displayed by oocytes expressing rho 1 Delta 450-GFP was distributed similarly to that of rho 1-GFP. Mammalian cells transfected with the rho 1-GFP or rho 1 Delta 450-GFP constructs showed mostly intracellularly distributed fluorescence in confocal microscope images. A sparse localization of fluorescence was observed in the plasma membrane regardless of the cell line used. We conclude that rho 1 Delta 450 is expressed and transported close to, and perhaps incorporated into, the plasma membrane. Thus, rho 1- and rho 1 Delta 450-GFP fusions provide a powerful tool to visualize the traffic of GABA type C receptors.
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Affiliation(s)
- A Martinez-Torres
- Laboratory of Cellular and Molecular Neurobiology, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA
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Billups D, Hanley JG, Orme M, Attwell D, Moss SJ. GABAC receptor sensitivity is modulated by interaction with MAP1B. J Neurosci 2000; 20:8643-50. [PMID: 11102469 PMCID: PMC6773065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2000] [Revised: 09/13/2000] [Accepted: 09/18/2000] [Indexed: 02/18/2023] Open
Abstract
GABA(C) receptors contain rho subunits and mediate feedback inhibition from retinal amacrine cells to bipolar cells. We previously identified the cytoskeletal protein MAP1B as a rho1 subunit anchoring protein. Here, we analyze the structural basis and functional significance of the MAP1B-rho1 interaction. Twelve amino acids at the C terminus of the large intracellular loop of rho1 (and also rho2) are sufficient for interaction with MAP1B. Disruption of the MAP1B-rho interaction in bipolar cells in retinal slices decreased the EC(50) of their GABA(C) receptors, doubling the receptors' current at low GABA concentrations without affecting their maximum current at high concentrations. Thus, anchoring to the cytoskeleton lowers the sensitivity of GABA(C) receptors and provides a likely site for functional modulation of GABA(C) receptor-mediated inhibition.
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MESH Headings
- Amino Acid Transport Systems, Neutral
- Animals
- Binding Sites/genetics
- Binding, Competitive/drug effects
- Binding, Competitive/genetics
- Blotting, Western
- COS Cells
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cells, Cultured
- Dose-Response Relationship, Drug
- GABA Antagonists/pharmacology
- Glutathione Transferase/genetics
- Glycine Agents/pharmacology
- Glycine Plasma Membrane Transport Proteins
- In Vitro Techniques
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Mutagenesis, Site-Directed
- Patch-Clamp Techniques
- Peptides/genetics
- Peptides/pharmacology
- Phosphinic Acids/pharmacology
- Protein Structure, Tertiary/genetics
- Pyridines/pharmacology
- Receptors, GABA/genetics
- Receptors, GABA/metabolism
- Receptors, GABA-B
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Retina/drug effects
- Retina/metabolism
- Transfection
- gamma-Aminobutyric Acid/metabolism
- gamma-Aminobutyric Acid/pharmacokinetics
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Affiliation(s)
- D Billups
- Laboratory for Molecular Cell Biology, Department of Pharmacology, University College London, London, WC1E 6BT, United Kingdom
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35
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Abstract
GABA(C) receptors are expressed in the whole brain, but predominantly in the retina. They can be identified by their unique pharmacology. The establishment of the entire pharmacology is, however, quite tedious. We show here that loreclezole dose dependently inhibits ionic currents elicited by GABA (gamma-aminobutyric acid) with an IC(50) of about 0.5 microM in homomeric rho1 GABA(C) receptors expressed in Xenopus oocytes. Thus, loreclezole may constitute a functional marker for these receptors.
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Affiliation(s)
- U Thomet
- Department of Pharmacology, University of Bern, Friedbuehlstr. 49, CH-3010, Bern, Switzerland
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36
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Pan ZH, Zhang D, Zhang X, Lipton SA. Evidence for coassembly of mutant GABAC rho1 with GABAA gamma2S, glycine alpha1 and glycine alpha2 receptor subunits in vitro. Eur J Neurosci 2000; 12:3137-45. [PMID: 10998097 DOI: 10.1046/j.1460-9568.2000.00198.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Functional coassembly of gamma-aminobutyric acid (GABA)C rho1 subunits with GABAA (alpha1, beta2, and gamma2S) or glycine (alpha1, alpha2, and beta) subunits was examined using two-electrode voltage-clamp recordings in the Xenopus laevis oocyte expression system. To facilitate this study, we took advantage of the unique gating and pharmacological properties of two mutant rho1 subunits, rho1(T314A) and rho1(T314A/L317A). When the rho1(T314A) subunit was coexpressed with GABA gamma2S, glycine alpha1 or glycine alpha2 subunits, GABA response properties were different from those of homomeric rho1(T314A) receptors. Additionally, the sensitivity of heteromeric rho1(T314A) and gamma2S receptors to picrotoxinin (PTX) blockade of GABA-evoked responses was altered compared to that of homomeric rho1(T314A) receptors. Changes in GABA response properties and picrotoxinin sensitivity were also observed when rho1(T314A) subunits were coexpressed with wild-type rho1 subunits. When rho1(T314A/L317A) subunits were coexpressed with GABA gamma2S, glycine alpha1 or glycine alpha2 subunits, suppression by GABA of spontaneously active current was reduced compared to that of homomeric rho1(T314A/L317A) receptors. Recovery of the spontaneous current from inhibition by GABA for GABA rho1(T314A/L317A)/gamma2S heteromeric receptors displayed an additional component. Coinjection of wild-type rho1 with gamma2S cRNAs at a ratio of 1 : 1 resulted in a > 10-fold reduction in GABA-evoked current. Furthermore, coexpression of wild-type rho1 and gamma2S subunits was found to shift the GABA dose-response curve. Our results provide functional evidence that the GABAC rho1 subunit can coassemble with the GABAA gamma2S subunit, and, at least in its mutated form, rho1 can also form heteromeric receptors with glycine alpha1 or alpha2 subunits in vitro.
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MESH Headings
- Animals
- Dose-Response Relationship, Drug
- Electrophysiology
- GABA Antagonists/pharmacology
- Gene Expression/physiology
- In Vitro Techniques
- Mutagenesis/physiology
- Neural Inhibition/genetics
- Oocytes/physiology
- Picrotoxin/pharmacology
- Protein Structure, Tertiary/genetics
- Rats
- Receptors, GABA/chemistry
- Receptors, GABA/genetics
- Receptors, GABA/metabolism
- Receptors, GABA-A/chemistry
- Receptors, GABA-A/genetics
- Receptors, GABA-A/metabolism
- Receptors, GABA-B
- Receptors, Glycine/chemistry
- Receptors, Glycine/genetics
- Receptors, Glycine/metabolism
- Retina/metabolism
- Xenopus laevis
- gamma-Aminobutyric Acid/pharmacology
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Affiliation(s)
- Z H Pan
- CNS Research Institute, Brigham & Women's Hospital and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA.
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37
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Marcos I, Ruiz A, Blaschak CJ, Borrego S, Cutting GR, Antinolo G. Mutation analysis of GABRR1 and GABRR2 in autosomal recessive retinitis pigmentosa. J Med Genet 2000; 37:E5. [PMID: 10851258 PMCID: PMC1734609 DOI: 10.1136/jmg.37.6.e5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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38
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Filippov AK, Couve A, Pangalos MN, Walsh FS, Brown DA, Moss SJ. Heteromeric assembly of GABA(B)R1 and GABA(B)R2 receptor subunits inhibits Ca(2+) current in sympathetic neurons. J Neurosci 2000; 20:2867-74. [PMID: 10751439 PMCID: PMC6772195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/1999] [Revised: 02/02/2000] [Accepted: 02/07/2000] [Indexed: 02/16/2023] Open
Abstract
Neuronal GABA(B) receptors regulate calcium and potassium currents via G-protein-coupled mechanisms and play a critical role in long-term inhibition of synaptic transmission in the CNS. Recent studies have demonstrated that assembly of GABA(B) receptor GABA(B)R1 and GABA(B)R2 subunits into functional heterodimers is required for coupling to potassium channels in heterologous systems. However whether heterodimerization is required for the coupling of GABA(B) receptors to effector systems in neurons remains to be established. To address this issue, we have studied the coupling of recombinant GABA(B) receptors to endogenous Ca(2+) channels in superior cervical ganglion (SCG) neurons using nuclear microinjection to introduce both sense and antisense expression constructs. Patch-clamp recording from neurons injected with both GABA(B)R1a/1b and GABA(B)R2 cDNAs or with GABA(B)R2 alone produced marked baclofen-mediated inhibition of Ca(2+) channel currents via a pertussis toxin-sensitive mechanism. The actions of baclofen were blocked by CGP62349, a specific GABA(B) antagonist, and were voltage dependent. Interestingly, SCGs were found to express abundantly GABA(B)R1 but not GABA(B)R2 at the protein level. To determine whether heterodimerization of GABA(B)R1 and GABA(B)R2 subunits was required for Ca(2+) inhibition, the GABA(B)R2 expression construct was microinjected with a GABA(B)R1 antisense construct. This resulted in a dramatic decrease in the levels of the endogenous GABA(B)R1 protein and a marked reduction in the inhibitory effects of baclofen on Ca(2+) currents. Therefore our results suggest that in neurons heteromeric assemblies of GABA(B)R1 and GABA(B)R2 are essential to mediate GABAergic inhibition of Ca(2+) channel currents.
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Affiliation(s)
- A K Filippov
- Department of Pharmacology, University College London, London WC1E 6BT, United Kingdom
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39
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Abstract
We have examined the sensitivity of human and rat homo-oligomeric rho(1) GABA receptors to variations in extracellular pH (pH(o)) using the whole-cell patch clamp technique. The GABA-induced conductance mediated by the rat rho(1) receptor (rho(1)-R) decreased with a decrease in pH(o) between 9.0 to 5.4. Below pH(o) 7.4 the effect of protons on the GABA-induced conductance was apparently competitive, but above pH(o) 7.4 the inhibitory effect of extracellular protons was almost independent on the GABA concentration. Titration of the GABA-induced conductance at 3 microM GABA revealed two protonation sites on rat rho(1)-R with pKa 6.4 and pKa 8.2. At 10 microM GABA the low pKa (6.4) was shifted to a clearly lower value (5.6), but the high pKa was only slightly decreased (from 8.2 to 7.9). Zn(2+) ions were capable of relieving the proton inhibition at low pH(o) indicating that Zn(2+) interacts with the low pKa site. Unlike the rat rho(1)-R, the human rho(1)-R was sensitive only to changes in pH(o) at acidic levels. Proton inhibition of human rho(1)-R was apparently competitive, as observed on rat-rho(1) at acidic pH(o). Titration of the human rho(1)-R gave a single H(+) binding site with a pKa of 6.3, similar to the value for the low pKa on rat rho(1)-R. The pKa value of human rho(1)-R was not dependent on the GABA concentration. A chimeric receptor, consisting of the N-terminal part of the rat rho(1)-R and C-terminal part of the human rho(1)-R, displayed pH(o) sensitivity similar to that observed for rat rho(1)-R. This indicates that the high pKa of rat rho(1)-R is attributable to the 11 amino acid differences between the rat and human rho(1)-R extracellular domains.
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Affiliation(s)
- C Rivera
- Department of Biosciences, Division of Animal Physiology, P.O. Box 17, FIN-00014 University of Helsinki, Finland
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40
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Carlson BX, Engblom AC, Kristiansen U, Schousboe A, Olsen RW. A single glycine residue at the entrance to the first membrane-spanning domain of the gamma-aminobutyric acid type A receptor beta(2) subunit affects allosteric sensitivity to GABA and anesthetics. Mol Pharmacol 2000; 57:474-84. [PMID: 10692487 DOI: 10.1124/mol.57.3.474] [Citation(s) in RCA: 230] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Site-directed mutagenesis of the gamma-aminobutyric acid type A (GABA(A)) receptor beta(2) subunit has demonstrated that conversion of a conserved glycine residue located at the entrance to the first transmembrane domain into the homologous rho(1) residue phenylalanine alters the modulating effects of four different i.v. anesthetics: pentobarbital, alphaxalone, etomidate, and propofol. Using the baculovirus expression system in Spodoptera frugiperda 9 cells, anesthetic-induced enhancement of [(3)H]muscimol and [(3)H]flunitrazepam binding in receptors containing the beta(2)(G219F) point mutation displayed a significantly reduced efficacy in modulation by all four i.v. anesthetics tested. Furthermore, GABA(A) receptors containing the alpha(1)(G223F) point mutation also significantly decreased the maximal effect of etomidate- and propofol-induced enhancement of ligand binding. Conversely, the homologous point mutation in rho(1) receptors (F261G) changed the i.v. anesthetic-insensitive receptor to confer anesthetic modulation of [(3)H]muscimol binding. Consistent with the binding, functional analysis of pentobarbital-enhanced GABA currents recorded with whole-cell patch clamp demonstrated the beta(2)(G219F) subunit mutation eliminated the potentiating effect of the anesthetic. Similarly, propofol-enhanced GABA currents were potentiated less in alpha(1)beta(2)(G219F)gamma(2) receptors than in alpha(1)beta(2)gamma(2) receptors. Although ligand binding displayed comparable K(D) values for muscimol among wild-type, alpha(1)beta(2)gamma(2), and mutant receptors, patch-clamp recordings showed that alpha(1)beta(2)(G219F)gamma(2) receptors had a significantly more potent response to GABA than did alpha(1)beta(2)gamma(2) or alpha(1)(G223F)beta(2)gamma(2). The alpha(1)beta(2)(G219F)gamma(2) receptors also were more sensitive to direct channel activation by pentobarbital and propofol in the absence of GABA. These results suggest that the first transmembrane glycine residue on the beta(2) subunit may be important for conformational or allosteric interactions of channel gating by both GABA and anesthetics.
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Affiliation(s)
- B X Carlson
- Department of Pharmacology, The Royal Danish School of Pharmacy, Copenhagen, Denmark
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41
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Dharmaraj S, Li Y, Robitaille JM, Silva E, Zhu D, Mitchell TN, Maltby LP, Baffoe-Bonnie AB, Maumenee IH. A novel locus for Leber congenital amaurosis maps to chromosome 6q. Am J Hum Genet 2000; 66:319-26. [PMID: 10631161 PMCID: PMC1288337 DOI: 10.1086/302719] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Sharola Dharmaraj
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Yingying Li
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Johane M. Robitaille
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Eduardo Silva
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Danping Zhu
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Thomas N. Mitchell
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Lara P. Maltby
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Agnes B. Baffoe-Bonnie
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
| | - Irene H. Maumenee
- The Johns Hopkins Center for Hereditary Eye Diseases, The Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore; IWK-Grace Health Centre, Dalhousie University, Halifax; Women's and Children's Health, North Carolina Department of Health and Human Services, Wilmington; Fox Chase Cancer Center, Philadelphia; and Division of Statistical Genetics, National Human Genome Research Institute, National Institutes of Health, Bethesda
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42
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Wotring VE, Chang Y, Weiss DS. Permeability and single channel conductance of human homomeric rho1 GABAC receptors. J Physiol 1999; 521 Pt 2:327-36. [PMID: 10581305 PMCID: PMC2269674 DOI: 10.1111/j.1469-7793.1999.00327.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/1999] [Accepted: 09/24/1999] [Indexed: 11/27/2022] Open
Abstract
1. Homomeric human rho1 GABAC receptors were expressed in Xenopus oocytes and in human embryonic kidney cells (HEK293) in order to examine their conductance and permeability. 2. Reversal potentials of currents elicited by gamma-aminobutyric acid (GABA) were measured in extracellular solutions of various ionic composition to determine relative permeability of homomeric rho1 receptors. The rank order of anionic permeability was: SCN- > I- > NO3- > Br- > Cl- > formate (For-) > HCO3- > acetate (Ac-) approximately proprionate (Prop-) approximately isethionate (Ise-) approximately F- approximately PO4-. 3. In the oocyte expression system, relative permeabilities to SCN-, I-, NO3-, Br- and HCO3- were higher for rho1 GABAC receptors than alpha1beta2gamma2L GABAA receptors. 4. Expression of rho1 GABAC receptors in Xenopus oocytes and in HEK293 cells gave similar relative permeabilities for selected anions, suggesting that the expression system does not significantly alter permeation properties. 5. The pore diameter of the homomeric rho1 GABAC receptor expressed in oocytes was estimated to be 0.61 nm, which is somewhat larger than the 0.56 nm pore diameter estimated for alpha1beta2gamma2L GABAA receptors. 6. Homomeric rho1 GABA receptors expressed in oocytes had a single channel chord conductance of 0.65 +/- 0.04 pS (mean +/- s.e.m.) when the internal chloride concentration ([Cl-]i) was 20 mM. With a [Cl-]i of 100 mM, the single channel chord conductance was 1.59 +/- 0.24 pS. 7. The mean open time directly measured from 43 GABA-induced channel openings in six patches was 3. 2 +/- 0.8 s. The mean open time in the presence of 100 microM picrotoxin was 0.07 +/- 0.01 s (77 openings from 3 patches). 8. The differences observed in ionic permeabilities, pore size, single channel conductance and mean open time suggest that the rho1 homomeric receptor may not be the native retinal GABAC receptor reported previously.
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Affiliation(s)
- V E Wotring
- Department of Neurobiology, University of Alabama at Birmingham, 1719 Sixth Avenue South, CIRC 410, Birmingham, AL 35294, USA
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43
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Sloviter RS, Ali-Akbarian L, Elliott RC, Bowery BJ, Bowery NG. Localization of GABA(B) (R1) receptors in the rat hippocampus by immunocytochemistry and high resolution autoradiography, with specific reference to its localization in identified hippocampal interneuron subpopulations. Neuropharmacology 1999; 38:1707-21. [PMID: 10587087 DOI: 10.1016/s0028-3908(99)00132-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Immunocytochemical and autoradiographic methods were used to localize the GABA(B) receptor in the normal rat hippocampus. GABA(B) receptor 1-like immunoreactivity (GBR1-LI) was most intense in presumed GABAergic interneurons of all hippocampal subregions. It was also present throughout the hippocampal neuropil, where it was most intense in the dendritic strata of the dentate gyrus, which are innervated by the perforant pathway and inhibitory dentate hilar cells, and in strata oriens and radiatum of area CA3. The dendritic regions of area CA1 exhibited less GBR1-LI than area CA3. GBR1-LI was detectable in the somata of CA1 pyramidal cells, but was minimal or undetectable within the somata of dentate granule cells and CA3 pyramidal cells. GBR1-LI was similarly minimal in the dentate hilar neuropil, and in stratum lucidum, the two regions that contain granule cell axons and terminals. Nor was GBR1-LI detectable in the inhibitory basket cell fiber systems that surround hippocampal principal cell somata. Fluorescence co-localization studies indicated that significant proportions of interneurons expressing somatostatin, neuropeptide Y, cholecystokinin, calbindin, or calretinin also expressed GBR1-LI constitutively. Conversely, parvalbumin-positive GABAergic basket cells of the dentate gyrus and hippocampus, which form GABA(A) receptor-mediated inhibitory axo-somatic synapses, rarely contained detectable GBR1-LI. High resolution autoradiography with the GABA(B) receptor antagonist CGP 62349 revealed a close correspondence between receptor ligand binding and GBR1-LI, with several notable exceptions. Ligand binding closely matched GBR1-LI throughout the hippocampal, cortical, thalamic, and cerebellar neuropil. However, the hippocampal interneuron somata and dendrites that exhibited the most intense GBR1-LI, and the GBR1-positive somata of CA1 pyramidal cells, did not exhibit a similar density of [3H]-CGP 62349 binding. These data clarify the relationship between immunocytochemically identified receptor protein and potentially functional receptors, indicating that GBR1-LI reflects both non-functional cytoplasmic GBR1 and the ligand-bindable form of the protein, both before dimerization with GBR2 and after translocation to functional sites within cells. The staining and binding patterns further suggest that GBR1 is constitutively expressed in specific neuronal populations, and may exist in higher concentration in the axons of inhibitory hippocampal pathways that innervate dendritic zones, than in axo-somatic inhibitory terminals. Whether GBR1 is inducible in cells that contain GBR1 mRNA, but no detectable constitutive protein, remains to be determined in experimental studies.
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Affiliation(s)
- R S Sloviter
- Department of Pharmacology, University of Arizona College of Medicine, Tucson 85724-5050, USA.
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44
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Bailey ME, Albrecht BE, Johnson KJ, Darlison MG. Genetic linkage and radiation hybrid mapping of the three human GABA(C) receptor rho subunit genes: GABRR1, GABRR2 and GABRR3. Biochim Biophys Acta 1999; 1447:307-12. [PMID: 10542332 DOI: 10.1016/s0167-4781(99)00167-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
GABA(C) receptors mediate rapid inhibitory neurotransmission in retina. We have mapped, in detail, the human genes which encode the three polypeptides that comprise this receptor: rho1 (GABRR1), rho2 (GABRR2) and rho3 (GABRR3). We show that GABRR1 and GABRR2 are located close together, in a region of chromosome 6q that contains loci for inherited disorders of the eye, but that GABRR3 maps to chromosome 3q11-q13.3. Our mapping data suggest that the rho polypeptide genes, which are thought to share a common ancestor with GABA(A) receptor subunit genes, diverged at an early stage in the evolution of this gene family.
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Affiliation(s)
- M E Bailey
- Division of Molecular Genetics, Institute of Biomedical and Life Sciences, University of Glasgow, Anderson College, 56 Dumbarton Road, Glasgow, UK.
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45
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Ng GY, McDonald T, Bonnert T, Rigby M, Heavens R, Whiting P, Chateauneuf A, Coulombe N, Kargman S, Caskey T, Evans J, O'neill GP, Liu Q. Cloning of a novel G-protein-coupled receptor GPR 51 resembling GABAB receptors expressed predominantly in nervous tissues and mapped proximal to the hereditary sensory neuropathy type 1 locus on chromosome 9. Genomics 1999; 56:288-95. [PMID: 10087195 DOI: 10.1006/geno.1998.5706] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Query of the expressed sequence tag database with the rat metabotropic GABABR1A receptor amino acid sequence using the TFASTA algorithm revealed two partial cDNA fragments whose sequence information was then used to isolate by PCR a novel full-length human cDNA encoding a putative G-protein-coupled receptor (GPCR), termed GPR 51. Sequence analysis revealed that it encoded a protein of 941 amino acids, similar in size and homology to GABAB receptors followed by metabotropic glutamate receptors but not other GPCRs. GPR 51 expressed in COS-1 cells showed no specific binding for [3H](+)baclofen and when expressed in Xenopus oocyte and Xenopus melanophore functional assays showed no activity to GABA, (-)baclofen, and glutamic acid. Northern blot analysis and in situ hybridization revealed that GPR 51 transcripts were predominantly expressed in the central nervous system with highest abundance in the cortex, thalamus, hippocampus, amygdala, cerebellum, and spinal cord. In contrast, GPR 51 receptor transcripts were almost not detected in the peripheral tissues. Gene GPR 51 was localized by radiation hybrid mapping to chromosome 9, 4.81 cR from the WI-8684 marker, and proximal to the hereditary sensory neuropathy type 1 locus.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Brain/anatomy & histology
- Brain/metabolism
- COS Cells
- Charcot-Marie-Tooth Disease/genetics
- Chromosome Mapping
- Chromosomes, Human, Pair 9/genetics
- Cloning, Molecular
- Expressed Sequence Tags
- GTP-Binding Proteins/genetics
- Humans
- In Situ Hybridization
- Molecular Sequence Data
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Nervous System/metabolism
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, G-Protein-Coupled
- Receptors, GABA/genetics
- Receptors, GABA-B
- Saimiri/anatomy & histology
- Saimiri/metabolism
- Sequence Homology, Amino Acid
- Tissue Distribution
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Affiliation(s)
- G Y Ng
- Department of Biochemistry and Molecular Biology, Merck Frosst Center for Therapeutic Research, 16711 TransCanada Highway, Kirkland, Quebec, H9H 3L1,
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46
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Martin SC, Russek SJ, Farb DH. Molecular identification of the human GABABR2: cell surface expression and coupling to adenylyl cyclase in the absence of GABABR1. Mol Cell Neurosci 1999; 13:180-91. [PMID: 10328880 DOI: 10.1006/mcne.1999.0741] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have identified a gene encoding a GABAB receptor, the human GABABR2, located on chromosome 9q22.1, that is distinct from the recently reported rat GABABR1. GABABR2 structurally resembles GABABR1 (35% identity), having seven transmembrane domains and a large extracellular region, but differs in having a longer carboxy-terminal tail. GABABR2 is localized to the cell surface in transfected COS cells, and negatively couples to adenylyl cyclase in response to GABA, baclofen, and 3-aminopropyl(methyl)phosphinic acid in CHO cells lacking GABABR1. Baclofen action is inhibited by the GABABR antagonist, 2-hydroxysaclofen. The human GABABR2 and GABABR1 genes are differentially expressed in the nervous system, with the greatest difference being detected in the striatum in which GABABR1 but not GABABR2 mRNA transcripts are detected. GABABR2 and GABABR1 mRNAs are also coexpressed in various brain regions such as the Purkinje cell layer of the cerebellum. Identification of a functional homomeric GABABR2 coupled to adenylyl cyclase suggests that the complexity of GABAB pharmacological data is at least in part due to the presence of more than one receptor and opens avenues for future research leading to an understanding of metabotropic GABA receptor signal transduction mechanisms.
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Affiliation(s)
- S C Martin
- Department of Pharmacology, Boston University School of Medicine, 715 Albany Street, Boston, Massachusetts, 02118-2394, USA
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Ogurusu T, Yanagi K, Watanabe M, Fukaya M, Shingai R. Localization of GABA receptor rho 2 and rho 3 subunits in rat brain and functional expression of homooligomeric rho 3 receptors and heterooligomeric rho 2 rho 3 receptors. Recept Channels 1999; 6:463-75. [PMID: 10635063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Ionotropic GABA receptors that are composed of rho subunits act to gate bicuculline-insensitive Cl- currents. Reverse transcription-polymerase chain reaction analysis revealed that the expression of rho 2 mRNA in adult rat brain was approximately eight times higher than mRNA in the rat brain at embryonic day 16, while that of rho 3 in the embryonic brain was approximately six times higher than in the adult brain. In the adult rat brain the rho 3 mRNA was present in the mesencephalon, hippocampus, cerebellum, thalamus and basal ganglia. In situ hybridization has been used to demonstrate the presence of rho 2 mRNA in the hippocampal CA1 region of the 8-day-old rat, and in the CAl region of the hippocampus, lateral geniculate nucleus, superficial gray layer of the superior colliculus and the pars compacta of the substantia nigra of the adult rat. When the homooligomeric rho 3 receptors were expressed in Xenopus oocytes, applications of agonists induced ionic currents. The order of potency of the agonists was muscimol > GABA = trans-4-amino-crotonic acid > cis-4-aminocrotonic acid. The ionic currents induced by GABA were blocked by picrotoxinin and Zn2+ in dose-dependent manner. In heterooligomeric rho 2 rho 3 receptors, picrotoxinin sensitivity was significantly reduced.
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Affiliation(s)
- T Ogurusu
- Department of Information Science, Faculty of Engineering, Iwate University, Japan
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White JH, Wise A, Main MJ, Green A, Fraser NJ, Disney GH, Barnes AA, Emson P, Foord SM, Marshall FH. Heterodimerization is required for the formation of a functional GABA(B) receptor. Nature 1998; 396:679-82. [PMID: 9872316 DOI: 10.1038/25354] [Citation(s) in RCA: 848] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the mammalian central nervous system, where it exerts its effects through ionotropic (GABA(A/C)) receptors to produce fast synaptic inhibition and metabotropic (GABA(B)) receptors to produce slow, prolonged inhibitory signals. The gene encoding a GABA(B) receptor (GABA(B)R1) has been cloned; however, when expressed in mammalian cells this receptor is retained as an immature glycoprotein on intracellular membranes and exhibits low affinity for agonists compared with the endogenous receptor on brain membranes. Here we report the cloning of a complementary DNA encoding a new subtype of the GABAB receptor (GABA(B)R2), which we identified by mining expressed-sequence-tag databases. Yeast two-hybrid screening showed that this new GABA(B)R2-receptor subtype forms heterodimers with GABA(B)R1 through an interaction at their intracellular carboxy-terminal tails. Upon expression with GABA(B)R2 in HEK293T cells, GABA(B)R1 is terminally glycosylated and expressed at the cell surface. Co-expression of the two receptors produces a fully functional GABA(B) receptor at the cell surface; this receptor binds GABA with a high affinity equivalent to that of the endogenous brain receptor. These results indicate that, in vivo, functional brain GABA(B) receptors may be heterodimers composed of GABA(B)R1 and GABA(B)R2.
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Affiliation(s)
- J H White
- Receptor Systems, Molecular Pharmacology Unit, GlaxoWellcome, Medicines Research Centre, Stevenage, Hertfordshire, UK
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Abstract
Desensitization of ligand-gated receptor channels is an intrinsic feedback mechanism and prevents the receptor/channels from becoming overly activated thereby maintaining biological function of the nervous system. Desensitization also plays an important role in neuronal plasticity. By taking advantage of biophysical and pharmacological diversities of GABA beta2 subunits from the brain and rho1 subunits from the retina, structural determinants that confer agonist-induced desensitization were identified. A synthetic chimeric receptor/channel was created from the beta2 and rho1 subunits for this investigation. The chimera was constructed from the extracellular N-domain of the beta2 subunit, extending from the amino terminus to the beginning region of the M1 transmembrane segment, and from the C-domain of the rho1 subunit extending from the M1 transmembrane segment to the carboxyl terminus. The C-domain region included the M1 to M4 transmembrane regions and the large intracellular loop between the M3 and M4 transmembrane segments. Homo-oligomeric GABA beta2, rho1, and beta2/rho1 chimeric receptor/channels were individually expressed in Xenopus oocytes, and the desensitization characteristics attributable to each type of subunit were compared. Results from the present study reveal that motifs in the amino-terminal and carboxyl-terminal domains of the beta2 subunit conferred the agonist-induced desensitization; chloroform modulation was linked to specific phases of the GABA-activated current decay.
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Affiliation(s)
- L Lu
- Department of Physiology and Biophysics, Wright State University, School of Medicine, Dayton, OH 45435, USA
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Hackam AS, Wang TL, Guggino WB, Cutting GR. The N-terminal domain of human GABA receptor rho1 subunits contains signals for homooligomeric and heterooligomeric interaction. J Biol Chem 1997; 272:13750-7. [PMID: 9153229 DOI: 10.1074/jbc.272.21.13750] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
gamma-Aminobutyric acid type C (GABAC) receptors identified in retina appear to be composed of GABA rho subunits. The purpose of this study was to localize signals for homooligomeric assembly of rho1 subunits and to investigate whether the same region contained signals for heterooligomeric interaction with rho2 subunits. In vitro translated human rho1 was shown to be membrane-associated, and proteinase K susceptibility studies indicated that the N terminus was oriented in the lumen of ER-derived microsomal vesicles. This orientation suggested the involvement of the N terminus of rho1 in the initial steps of subunit assembly. To test this hypothesis, mutants were created containing only N-terminal sequences (N-rho1) or C-terminal sequences (C-rho1) of rho1. Co-immunoprecipitation studies revealed that N-rho1, but not C-rho1, interacted with rho1 in vitro. When coexpressed in Xenopus oocytes, N-rho1 interfered with rho1 receptor formation. Together, these data suggested that signals for rho1 homooligomeric assembly reside in the N-terminal half of the subunit. Sequential immunoprecipitations were then performed upon cotranslated rho1 and rho2 subunits which demonstrated that rho1 and rho2 interacted in vitro. Co-immunoprecipitation indicated that N-rho1 specifically associated with rho2. Therefore, the N-terminal regions of rho subunits contain the initial signals for both homooligomeric and heterooligomeric assembly into receptors with GABAC properties.
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Affiliation(s)
- A S Hackam
- Center for Medical Genetics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA
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